Redheaded Woodpecker. 
Courtesy Dr. George S. Britten. 
This photograph shows how the tail is used as a brace and how the toes 
are opposite so as to grip the bark of the tree. These are adaptations not 
seen in the house sparrow, for example. Do you see any other adaptation? NEW BIOLOGY 
BY 
W. M. SMALLWOOD 
SYRACUSE UNIVERSITY 
IDA L. REVELEY 
WELLS COLLEGE 
GUY A. BAILEY 
GENESEO STATE NORMAL SCHOOL 
ALLYN and BACON 
BOSTON NEW YORK CHICAGO 
ATLANTA SAN FRANCISCO COPYRIGHT, 1924 
BY ALLYN AND BACON. 
AAO PREFACE 
The New Biology offers a unit course dealing with the 
fundamental functions of living things. But, owing to the 
fact that different animals and plants may be used equally 
well in a study of these processes, we offer a wider selection 
than the minimum requirements. 
The forms of life are so numerous and their interrelations 
so complex that only the more general facts are presented. 
Such a plan, however, gives an insight into the way that 
organisms live and the dependence of living things on the 
physical world. Some of these relations are modified by 
man as he uses them to serve his own ends. 
We are coming to realize more and more that it is what 
an organism does that is important rather than the details 
of its structure, and this is the reason that we have departed 
somewhat from the older type study which has characterized 
earlier texts on biology. 
Biology will take its recognized place as a valuable subject 
in training only when teachers require accuracy of observa- 
tion and the recording of these observed facts in suitable 
note-books. It is possible to learn much about our own lives 
from the study of animals and plants, but trustworthy con- 
clusions can be formulated only from reliable observations. 
We have suggested a method of study in the laboratory 
problems to train the student in accuracy of observing and 
recording. 
All the remarkable progress in biological information 
has come through the painstaking observations of many 
scientists, who by their contributions have made the world 
a better place to live in. But in our zeal to apply these 
III IV 
PREFACE 
brilliant discoveries to human welfare, we must not overlook 
the beauty of biology; and, as we attempt to understand 
life, let us not miss the delight that comes from simply know- 
ing animals and plants in their homes. The first spring 
flower and the first immigrant bird herald the coming of 
spring. These in turn are followed by so many living things 
that every excursion to parks and woods throughout the 
summer and fall furnishes one with a most varied program 
of entertainment. Even the winter supplies many oppor- 
tunities for the study of animals and plants that have now 
become our friends. One is richer and happier who has 
such a storehouse of pictures to enjoy when his duties do 
not permit him to wander a-field. 
It is a pleasure to express our appreciation to the several 
high school teachers who have given us practical assistance 
by their friendly criticisms. We have drawn freely from the 
works of the numerous specialists in the many fields of 
biology whose contributions have made possible this book. 
Dr. Carlton F. Potter, Dr. David Gillette, and Dr. Walter 
Street have assisted the authors in showing the close con- 
nection between biology and our own bodies. The United 
States Department of Agriculture, The National Museum, 
The American Museum of Natural History, Nature Maga- 
zine, and many personal friends have furnished us with 
illustrations that add much to the value of this book. 
W. M. S. 
I. L. R. 
G. A. B. , 
June 1924. ACKNOWLEDGMENT OF ILLUSTRATIONS 
M. W. Blackman, New York State College of Forestry, 18, 108, 109. 
W. E. Britton, Connecticut Agricultural Station, 47. 
Conservation Commission, New York State, 168, 169, 361, 365. 
Cornell State College of Agriculture, 410, 411, 412. 
Fitzhenry-Guptill Co., Boston, 10. 
D. F. MacDougal, Desert Laboratory, Tucson, Ariz., 289. 
W. A. McKeever, 217, 218, 219. 
Dr. J. S. Marshall, Berkeley, Cal., 227, 230. 
S. O. Mast, Goucher College, Baltimore, Md., 179. 
W. A. Murrill, 382, 383, 384. 
New York State Bureau of Health, 267, 409. 
Omaha Chamber of Commerce, 212, 215, 216. 
Dr. Edward Packard, Saranac Lake, N. Y., 259, 260. 
F. C. Paulmier, 65, 66, 67. 
Dr. C. Potter, Syracuse, N. Y., 193, 194, 195, 196, 197, 203, 204, 224, 
231. 
A. M. Reese, University of West Virginia, Morgantown, W. Va., 37, 
38, 39, 40. 
A. G. Rutheven, University of Michigan, Ann Arbor, Mich., 106. 
G. B. Simpson, 71, 72. 
B. G. Smith, Ypsilanti, Mich., 86. 
J. M. Thorburn & Co., New York City, 242. 
C. H. Townsend, New York Aquarium, 74, 77, 85. 
University of Minnesota, 275, 301, 386, 387. 
United States Census 1910, 211. 
United States Department of Agriculture, 4, 5, 27, 28, 34, 42, 48, 49, 
50, 51, 52, 55, 56, 58, 60, 83, 84, 165, 210, 385, 393, 394, 413. 
United States Department of the Interior, 359, 360, 362, 363, 364, 366, 
389, 396. 
Jerome Walker, Physiology, 186, 234, 235, 243, 244, 246, 252. 
Anti-Saloon League, 251. 
Syracuse University, Botany Department, 286. 
National Museum, 102, 159, 285, 370. 
E. N. Sanborn, 148, 164. 
Tucson Chamber of Commerce, 388, 391, 392, 395, 397, 398. 
J. E. Weaver, University of Nebraska, 304. 
Anna Botsford Comstock, 375, 376. 
V CONTENTS 
PART I 
THE IDEA OF BIOLOGY 
CHAPTER PAGE 
I. The Life of the Apple Tree 1 
II. Important Life Functions 15 
III. Composition of Living Things .... 24 
IV. The Green Plant as a Food Factory . . 37 
V. The Physical Basis of Life .... 44 
PART II 
APPLICATION OF BIOLOGIC PRINCIPLES TO ANIMAL LIFE 
VI. The Grasshopper, an Introduction to the Study 
of Insects 49 
VII. Insects in General 62 
VIII. Moths and Bees 94 
IX. The Crab Family and How They Live . . 108 
X. A Simple Vertebrate, the Fish . . . .124 
XI. Frogs and Their Ways of Living . . . 141 
XII. A Group of Vertebrates That Have Become 
Nearly Extinct 162 
XIII. Birds 171 
XIV. Mammals, the Present Rulers of the Universe 207 
XV. The Simplest Animals - Protozoa . . . 241 
PART III 
THE APPLICATION OF BIOLOGIC PRINCIPLES TO THE 
HUMAN BODY 
XVI. Resemblances between Man and Other Animals 255 
XVII. General Structure of the Human Body . .261 
XVIII. Respiration 285 
XIX. Foods, Stimulants, and Narcotics . . . 297 
XX. Digestion and Absorption 333 
XXI. Circulation and Assimilation .... 349 
VII VIII 
CONTENTS 
CHAPTER PAGE 
XXII. Excretion 363 
XXIII. The Nervous System of Man .... 369 
XXIV. Bacteria : the Smallest Plants .... 389 
XXV. Health 404 
PART IV 
APPLICATION OF BIOLOGIC PRINCIPLES TO PLANTS 
XXVI. Study of a Living Green Plant . . . 436 
XXVII. Leaves - the Plant's Work-shop . . . 444 
XXVIII. Stems, the Plant's Transportation System . 466 
XXIX. The Root, the Plant's Absorbing Organ and 
Anchor 485 
XXX. Flowers and Fruits 496 
XXXI. Seeds and Germination ..... 531 
XXXII. Forests and Forest Products .... 544 
XXXIII. Fungi - Plants That Lack Chlorophyll . . 571 
XXXIV. Plant Culture 585 
PART V 
GENERAL BIOLOGY 
XXXV. Application of Biologic Principles to Human 
Interests 602 
XXXVI. Health and Conservation 624 
XXXVII. Biology and Human Progress .... 649 
Glossary 671 
Index 1 LIST OF ILLUSTRATIONS 
Redheaded Woodpecker. Colored .... Frontispiece 
FIGURE PAGE 
1. The Apple Tree in Blossom ....... 2 
2. Leaf-miners Destroying an Elm Leaf ..... 3 
3. The Fallen Apple Tree Undergoing Decay .... 4 
4. The "Worm" in the Apple 6 
5. Pupa of Codling Moth 7 
6. Adult Codling Moth ........ 7 
7. Picking Apples 9 
8. Successive Steps in Budding 10 
9. Successive Steps 1-5 in Grafting . . . . . .11 
10. High-power Spraying Machine Used in Orchard and City 
Parks .......... 12 
11. Squirrel . 18 
12. Adaptation of the Hand ....... 19 
13. Milkweed Seed 20 
14. Head of Eagle 21 
15. The Force of Gravity 33 
16. Cell from Fern Showing Chloroplasts and Nucleus . . 38 
17. Osmosis .......... 42 
18. A Cell 44 
19. Similar Cells United to Form a Tissue .... 45 
20. Female Grasshopper 51 
21. The Lips and Teeth of the Grasshopper .... 53 
22. Important Parts of the Grasshopper 54 
23. The Jumping Leg of the Grasshopper ..... 54 
24. Fore- and Hind-wings of the Grasshopper .... 55 
25. Incomplete Metamorphosis in the Grasshopper ... 58 
26. The Katydid ......... 59 
27. Cotton Plant ......... 63 
28. Adult Seventeen-year Cicada and Nymph .... 66 
29. Beetles .......... 68 
30. This Beetle Is the Fastest Flying Animal Known . . 69 
31. Eggs of Ladybug 70 
32. Tent Caterpillars ........ 72 
33. Wingless Female of Tussock Moth ..... 73 
IX X 
LIST OF ILLUSTRATIONS 
FIGURE PAGE 
34. Male and Female Cooties ....... 75 
35. Larva? of Destructive Insects 77 
36. Cedar Waxwing . . . . . . . .81 
37. Eggs and Larvae of Mosquito 82 
38. Larva of Culex in Breathing Position .... 83 
39. Pupa of Culex . . . . . . . ' .83 
40. Positions of Culex and Anopheles ..... 84 
41. The Dragon-fly ......... 85 
42. The Common House-fly 86 
43. Thalessa Laying Eggs ........ 88 
44. Tremex 89 
45. A Moth Showing Protective Colo ation .... 90 
46. Monarch Butterfly Showing Successive Stages in Its Meta- 
morphosis 95 
47. Young Tobacco Worm, a Caterpillar ..... 97 
48. Honey-bees 98 
49. Three Queen Cells ........ 99 
50. Honey-bee Egg, Young Larva, Old Larva, and Pupa . . 99 
51. Inner Surface of Left Hind Leg of Worker .... 100 
52. Outer Surface of Left Hind Leg of Worker .... 100 
53. The bee's Sting 101 
54. Honey-bees Clustering at Swarming Time .... 102 
55. Capturing a Swarm ........ 103 
56. Model Apiary ......... 104 
57. Tongue of Honey-bee ........ 105 
58. Worker Honey-bee Laden with Pollen .... 105 
59. Crayfish, Showing Eggs ....... 108 
60. Moulted Exoskeleton of Lobster ...... 109 
61. Body of Crayfish ......... 110 
62. Appendages of Crayfish Ill 
63. Organs of Crayfish . . . . . . . .114 
64. Nervous System of Crayfish 116 
65. Soft-shelled Crab Used for Food . . . . . .117 
66. Cyclops .......... 118 
67. Pill-bug . ■ 118 
68. Spider . . . 119 
69. Web of Spider 120 
70. Millipede; Centipede . 121 
71. Clam, Showing Foot . 121 
72. Inside of Clam Shell 122 
73. Embryo of Clam 122 LIST OF ILLUSTRATIONS 
XI 
FIGURE PAGE 
74. Perch, an Important Food-fish Common in Nearly All 
Freshwater Ponds . . . . . . . .125 
75. External Parts of Fish 126 
76. Scales of Fish 126 
77. Sunfish or Pumpkinseed 128 
78. Fish-eating Insect 129 
79. Gills of Fishes ......... 131 
80. Eggs of the Land-locked Salmon . . . . . .133 
81. Young Fish Just at the Hatching Stage .... 133 
82. Young Fish Seventeen Days after Hatching . . . 134 
83. The Grayfish Belongs to the Shark Family .... 136 
84. The Whiting or Eulachon 136 
85. Brook Trout ......... 137 
86. Some Common Salamanders Found on Land . . . 141 
87. Leopard Frog . . . . . . . . .142 
88. Diagram Showing Organs of Frog . . . . .144 
89. Digestive Tract of Frog . . . . . . .145 
90. Diagram to Show the Relations of the Testes to the Kidneys 
and the Relation of the Kidneys to the Intestine . . 146 
91. Central Nervous System of Frog . . . . .148 
92. Frog Eggs 150 
93. Diagram Illustrating Fertilization in Frog Egg . . . 151 
94. Dividing Egg of Frog 151 
95. The Embryo Becoming a Tadpole ..... 152 
96. Tadpoles .......... 153 
97. Toad 154 
98. Different Stages in the Life History of the Toad . . . 155 
99. A Group of Fossil Animals ....... 156 
100. A Fossil Leaf ......... 157 
101. Tree Frog 158 
102. Dinosaur 162 
103. The Oldest Living Animal 163 
104. Lizard ........... 164 
105. Head of Rattlesnake 165 
106. Rattlesnake - Poisonous 166 
107. Rattles of Rattlesnake 166 
108. Bull Snake with Hen's Egg in Mouth 167 
109. Bull Snake after Swallowing Egg . . . . .167 
110. Garter Snake and Seventeen Young 168 
111. Alligators 169 
112. Shrike / . . .172 XII 
LIST OF ILLUSTRATIONS 
FIGURE PAGE 
113. Diagram of Bird 173 
114. Prairie Horned Larks 173 
115. Nest of Goldfinch 174 
116. Eggs of the Woodcock 174 
117. Woodcock on Nest 177 
118. Nest of Chipping Sparrow with Cowbird's Egg . . .178 
119. Male and Female Cowbirds 179 
120. Bluebird 182 
121. Catbird 183 
122. Crow Feeding on Fish and Corn . . . . . .184 
123. Chickadee .......... 185 
124. Baltimore Oriole . . . . . . . . 185 
125. Robin 186 
126. House Sparrow 186 
127. Downy Woodpecker and Song Sparrow .... 187 
128. Barn Swallow ......... 188 
129. Flicker 189 
130. Phoebe .......... 190 
131. Herring Gulls ......... 191 
132. Screech Owl 192 
133. Yellow Warbler ......... 193 
134. House Wren ......... 194 
135. Kingfisher . . . . . . . . . . 194 
136. Junco ........... 195 
137. Bird's Feet 195 
138. Rose-breasted Grosbeak ....... 196 
139. Skeleton of a Mallard Duck . . . . . .196 
140. Young Pelican 197 
141. Canadian Wild Geese 198 
142. Ring-necked Plover 198 
143. Pelican Feeding Young ....... 199 
144. Common Booby, Young and Adult 200 
145. Bird Photography ........ 202 
146. Nest of the Yellow Warbler in Which a Cowbird's Egg Has 
Been Laid ......... 203 
147. Skeleton of a Dog 207 
148. Giraffe........... 208 
149. Deer Mouse 209 
150. Stomach of Sheep . 210 
151. Fore-arm and Hand of Mole 211 
152. Mole 211 LIST OF ILLUSTRATIONS 
XIII 
FIGURE PAGE 
153. Arm (Wing) of Bat 212 
154. Flipper of Balaenoptera Borealis 212 
155. Flying Squirrel . . .* 213 
156. Skeleton of Ziphioid Whale ....... 213 
157. Kangaroo with Young in Pouch ...... 214 
158. American Opossum ........ 215 
159. Elephant with a Highly Adaptive "Trunk" . . . 216 
160. Bison or American Buffalo ....... 218 
Red Foxes. Colored facing 218 
161. Wolf 220 
162. Bat with Expanded Wing 223 
163. Bat Sleeping 224 
164. Rabbit 225 
165. Tree Girdled by Rabbits ....... 226 
166. Skunk .......... 227 
167. Runways of Muskrat ........ 228 
168. Young Poplar Trees Cut Down by Beaver .... 229 
169. A Beaver House ......... 230 
170. A Standard Breed of Trotting Horse 231 
171. Cow and Calf 233 
172. Hampshire Sheep ........ 234 
173. Sow and Pigs 235 
174. Photomicrograph of an Amoeba ...... 243 
175. Diagram of an Amoeba ....... 244 
176. Amoeba Dividing by Fission ...... 246 
177. Diagram of Paramecium 247 
178. Paramecia Stained to Show the Nucleus .... 247 
179. Paramecium ......... 248 
180. Paramecium before and after Dividing .... 249 
181. Paramecium Reproducing by Fission 249 
182. Vorticella .......... 250 
183. Some Flagellate Protozoa 250 
184. One of the Foraminifera ....... 251 
185. Reindeer .......... 256 
186. Thoracic and Abdominal Cavities 262 
187. View of Skull from Below ....... 263 
188. Skeleton of Man ......... 264 
189. Front View of Skull ........ 265 
190. Diagram to Show the Relation of the Diaphragm to the Ribs 266 
191. Diagram to Show the Structure of Bone ... . . 267 
192. Cartilage .......... 267 XIV 
LIST OF ILLUSTRATIONS 
FIGURE PAGE 
193. X-Ray of Hand of Child 268 
194. X-Ray of Hand of Adult ....... 269 
195. X-Ray of Dislocated Finger * . . . . . . 269 
196. X-Ray of Broken Femur ....... 270 
196a. X-Ray of the Same Bone after Healing . . . 270 
197. Longitudinal Section of Femur, Showing the Compact and 
Spongy Tissue of Bone . . . . . . .271 
198. Voluntary Muscle Cells 272 
199. Involuntary Muscle Cells 272 
200. Heart Muscle Cells ........ 273 
201. Hip and Thigh Muscles ....... 274 
202. Muscles of Upper Leg 275 
203. X-Ray of the Foot of a Girl Wearing a High-Heeled Shoe . 281 
204. X-Ray of the Foot of a Girl Wearing a Sensible Shoe . . 282 
205. The Lungs and Heart ........ 286 
206. Voice Box or Larynx . . . . . . . 287 
207. Ciliated Epithelium 288 
208. Hot-air Heating ......... 292 
209. Steam Heating ......... 293 
210. School Children Raising Primary Foods .... 298 
211. Distribution of Dairy Cows in the United States . . 300 
212. Flouring Mill Where Wheat Is Turned into Flour . . 304 
213. Table of Protein Consumption ...... 308 
214. Table of Fat Consumption ....... 309 
215. Huge Grain Elevator ........ 312 
216. Raising Wheat for Flour ....... 316 
217. Chart of Heart Pulsation ....... 323 
218. Chart of Heart Pulsation ....... 324 
219. Chart of Heart Pulsation ....... 324 
220. Alimentary Canal of Man with Its Two Chief Digestive 
Glands, the Liver and Pancreas, Connected with the Small 
Intestine .......... 334 
221. Tongue of Man, Showing Two of the Three Kinds of 
Papillae 334 
222. Diagram of Taste Cells in the Tongue .... 335 
223. Pear-shaped Human Stomach ...... 336 
224. X-Ray Photograph of Human Stomach .... 336 
225. Diagram of a Villus from the Inner Wall of the Intestine . 337 
226. Human Gastric Gland ........ 338 
227. Permanent Teeth . . . . . . • 339 
228. Vertical Section of Tooth ....... 340 LIST OF ILLUSTRATIONS 
XV 
FIGURE PAGE 
229. X-Ray of Two Teeth ........ 340 
230. Milk Teeth 341 
231. X-Ray Photograph of Large Intestine of Man Showing 
Appendix .......... 344 
232. Photomicrograph of Human Blood 349 
233. Photomicrograph of Blood of Frog ..... 350 
234. Organs of Circulation ........ 351 
235. The Human Heart ........ 352 
236. Diagram of Capillaries ....... 353 
237. Heart ........... 354 
238. Main Arteries of Man . . . . . . . . 355 
239. Main Arteries of Frog ........ 355 
240. Diagram of Artery, Capillary and Vein .... 356 
241. Diagram of a Vein Showing the Valves .... 357 
242. Superficial Lymphatics of Arm and Hand .... 357 
243. Longitudinal Section of Kidney 364 
244. Diagram Showing Relation of Artery and Vein to Portion 
of Minute Kidney Tube ....... 365 
245. Diagram of Skin 365 
246. Nervous System of Man ....... 370 
247* Nerve Cells .......... 371 
248. Nerve Cells 372 
249. Diagram to Show Reflex Action 373 
250. Brain Control ......... 377 
251. Effects of Alcohol ........ 379 
252. Section of Eye 381 
253. How We See the Pencil ....... 382 
254. Plan of Ear 385 
255. Diagram of Cocci, Bacilli, Spirilla, Bacillus with Flagella . 390 
256. Culture Dish with Bacteria (a) . . . . . . 395 
257. Culture Dish with Bacteria (&) ..... 396 
258. Milk Bottles with and without Metal Caps . . . 397 
259. Tuberculosis Cure, Summer 405 
260. Tuberculosis Cure, Winter ....... 407 
261. Bacilli of Tuberculosis ........ 408 
262. Mosquito-destroying Fish 412 
263. Flatworm .......... 415 
264. Hair Worm Living as a Parasite in the Body of the Grass- 
hopper . . . 416 
265. Tapeworm 417 
266. Trichinella .......... 418 XVI 
LIST OF ILLUSTRATIONS 
FIGURE PAGE 
267. Story of the Epidemic of Septic Sore Throat at Rockville 
Centre, Long Island 429 
268. Pleurococcus ......... 438 
269. Cells in Different Stages of Division ..... 439 
270. Photomicrograph of the Cells Shown in Figure 269 . . 440 
271. Leaf of Oak .......... 444 
272. Leaf of a Strawberry, Showing Stipules .... 444 
273. Leaf of Elm ......... 445 
274. Illustration Showing the Arrangement by Which Leaves Re- 
ceive as Much Light as Possible 446 
275. Leaves of Young Plant of Pokeweed 447 
276. Palmately Compound Leaf of Woodbine .... 448 
277. Twining Petiole of Clematis ...... 449 
278. Leaf of Nasturtium ........ 449 
279. Leaves of Barberry 450 
280. Indian Pipe 451 
281. Diagram of Structure of a Leaf 452 
282. Bit of Epidermis of Leaf . . . . . . 454 
283. Skeleton of Polar Leaf . . . . . . 460 
284. Tw'g of Horse-ches nut ,469 
285. Excurrent Stem (Trunk) of Evergreen .... 470 
286. Cross Section of Young Dicotyledonous Stem . . .471 
287. Broken End of Corn Stem ....... 473 
288. Cross Section of Monocotyledonous Stem .... 474 
289. Giant Cactus ......... 477 
290. Dandelion .......... 479 
291. Corm of Indian Corn . . . . . . . 479 
292. Grains of Potato Starch ....... 480 
293. Potato, a Common Tuber ....... 480 
294. Rhizome of Pteris, a Common Fern ..... 481 
295. Cross Section of Underground Stem of Pteris, a Common 
Fern 482 
296. Cross and Longitudinal Section of Root .... 485 
297. Vertical Section of Root ....... 485 
298. Cross Section of Root with Root Hairs .... 486 
299. Bit of Epidermis of Root, Showing Origin of Root Hairs . 486 
300. Germinating Wheat, Showing Root Hairs . . . 487 
301. Root System of Rhubarb, a Medicinal Plant . . . 488 
302. Fjbrous Roots of a Buttercup ...... 489 
303. Fascicled Roots of Dahlia ....... 490 
304. Root System of Corn ........ 491 LIST OF ILLUSTRATIONS 
XVII 
FIGURE PAGE 
305. Flower of Nasturtium 497 
306. Flower of Nasturtium with Petals Removed . . . 497 
307. Pistil and Stamen of Nasturtium 498 
308. Long-spurred Blue Violet ....... 499 
309. Flower of Lily 500 
310. Stamens 500 
311. Stamen of Lily 501 
312. Spike 503 
313. Staminate Flowers of Poplar 503 
314. Compound Umbel of Wild Parsnip ..... 504 
315. Disc Flower of Daisy ........ 504 
316. Ray Flower of Daisy 505 
317. Spike of Plantain, a Common Weed ..... 505 
318. Flower of Calla ......... 506 
319. Flower of Columbine ........ 506 
320. Pollen Grains Sprouting and Growing through Style . . 507 
321. Pollen Grain Sprouted 507 
322. Portion of Pollen Tube Dissolving Its Way through Loose 
Tissue of Style 507 
323. Flowers of Willow ........ 508 
324. Staminate Flowers of Corn, the "Tassel" .... 509 
325. Pistillate Flowers of Corn 510 
326. Violet Plant with Cleistogamous Flowers . . . .511 
327. Flower of Salvia ......... 512 
328. Flower of Dandelion ........ 513 
329. Lady-slippers 514 
Moccasin Flower. Colored facing 514 
330. Pink Lady-slippers . . . . . . . .515 
331. A Rare Orchid ......... 516 
332. Dehiscent Capsule of Poppy 517 
333. Dry Fruit of Dandelion, the Akene ..... 517 
334. Explosive Capsule of Violet ...... 517 
335. Dry Fruits .......... 518 
336. Chestnut, a Dry Fruit ....... 518 
337. Cross Section of Orange . . . . . . .518 
338. Diagram Showing the Stem End Attached to the Orange; 
Under Side of Stem End; Pit in Orange after Removal of 
Remains of Stem ........ 519 
339. Samara of Maple 519 
340. Diagram of Fruit of Rose ....... 520 
341. Cross Section of Cucumber 520 XVIII 
LIST OF ILLUSTRATIONS 
FIGURE PAGE 
342. Cross Section of Apple ....... 521 
343. Vertical Section of Apple, a Pome . . . . .521 
344. Clotbur or Cocklebur ........ 522 
345. Fruit of Wild Carrot ........ 522 
346. Fruit of Avens ......... 523 
347. Fruit of Hound's Tongue ....... 523 
348. Fruit of White Mustard ....... 524 
349. Cattails .......... 526 
350. Bean Seed, Showing Parts ....... 531 
351. Seeds of Bean and Pea ....... 532 
352. Unsprouted Grain of Corn . . . . . . 532 
353. Plumule Ready to Break Out ...... 532 
354. Growth of Bean Plant ........ 533 
355. Diagram of Grain of Corn ....... 534 
356. Plumule Free but Bent by Accident ..... 534 
357. Plumule Unfolded ........ 535 
358. Advanced Corn Seedling ....... 536 
359. What Deforesting Did in China ...... 545 
360. What Deforesting Is Doing in the United States . . 546 
361. Fire Slash 548 
362. Sign Containing Warning about Fires ..... 549 
363. The Result of Hurricane and Fire in Idaho .... 550 
364. Castle Peak Fire Lookout ....... 551 
365. Nursery Where Young Trees Are Started .... 552 
366. Airplane View of Evergreen Forest ..... 553 
367. Hemlock Twigs and Cones ....... 556 
368. White Pine Cone ......... 557 
369. Twigs and Cone of Norway Spruce ..... 558 
370. A Group of Redwood Trees ...... 559 
371. Pollen Grain of Pine ........ 560 
372. Young Ovule-bearing Organ (Cone) ..... 560 
373. Young Pollen-bearing Organ of Pine ..... 561 
374. Mature Cone of Pine ........ 561 
375. Evergreen Tips, I ........ 562 
376. Evergreen Tips, II ....... . 563 
377. Sections of Wood ........ 564 
378. Diagram Showing How Logs Are Quarter-sawn . . . 565 
379. Yeast Plants ......... 572 
380. Fermentation Tubes ........ 573 
381. Bread Mold ......... 574 
382. Cpmmoji Field Puffball ....... 575 LIST OF ILLUSTRATIONS 
XIX 
FIGURE PAGE 
383. Shaggy-mane (Coprinus Comatus) in Perfect Condition 
for Picking 576 
384. Oyster Mushroom ........ 377 
385. Potato Wart ......... 579 
386. A Diseased Head of Wheat ....... 581 
387. Diagram of Life History of Red Rust of Wheat . . . 582 
388. Peach Orchard on Reclaimed Mesa Land .... 585 
389. Irrigating Ditches ........ 587 
390. A Field of Corn ......... 590 
391. Field Sown in Drills 591 
392. A Desert Scene ......... 592 
393. Nodules on Roots of Bean Plant ...... 593 
394. Nodules on Roots of Peanuts ...... 594 
395. Desert Land ......... 595 
396. Irrigating Ditch ......... 596 
397. Grapes Grown on Irrigated Desert Land .... 597 
398. Apricot Tree in Arizona ....... 598 
399. A Balanced Aquarium ........ 603 
400. Diagram of the Body of an Earthworm .... 606 
401. Gonium 614 
402. Volvox .......... 614 
403. A Simple Sponge 615 
404. Sponge Spicules ......... 615 
405. A Branching Sponge . . . . . . . .616 
406. Diagram of Body of Hydra . . . . . . .617 
407. Hydra 618 
408. One of New York City's Reservoirs ..... 626 
409. A Poor Reservoir ........ 627 
410. Timothy Heads ......... 650 
411. Bundles of Timothy Raised under Identical Conditions from 
the Same Amount of Seed . . . . . .651 
412. Heredity in Wheat 652 
413. Leaf Galls on Grape Caused by Grape Phylloxera . . 653 
414. Heredity Shown by Comparison 656 
415. Gregor Mendel ......... 658 
416. Diagram to Illustrate Simple Mendelian Inheritance , . 659 PORTRAITS OF PROMINENT BIOLOGISTS 
FACING PAGE 
Huxley 52 
Howard 88 
Jordan ........... 126 
Agassiz 142 
Audubon 180 
Harvey 354 
Pasteur ........... 396 
Smith ........... 406 
Koch ' ... . 430 
Bessey . . . 498 
Burbank 598 
Sedgwick ........... 628 
Darwin 652 
XXI NEW BIOLOGY 
PART I 
THE IDEA OF BIOLOGY 
CHAPTER I 
THE LIFE OF THE APPLE TREE 
As the twig is bent, the tree's inclined. 
- Pope 
1. A Study of Living Things. - Biology is the study of 
living things - plants and animals. In our study we are 
going to see : (1) how these things live; (2) what their rela- 
tions are to one another; (3) how they depend on the physi- 
cal world about them ; and (4) man's power to control them. 
But before we take up this regular work, we can illustrate 
much that we wish to know, by studying the life of something 
we are all familiar with, for instance, an apple tree. 
2. The Seed and the Seed-leaves. - When the seed of 
an apple sprouts, a tiny plant comes through the ground 
bearing two green seed-leaves. There is a little stem that 
joins the leaves and there are small roots that reach down into 
the ground. In a few days two more leaves appear. These 
are thinner and of a deeper green color than the seed-leaves. 
3. The Plant and the Soil. - The little seed that we began 
with is now a well-developed plant. It has all the parts that 
a small plant needs. The roots take up food in the form of 
solutions, that is, water in which parts of the soil are dis- 
1 2 
THE LIFE OF THE APPLE TREE 
solved. These roots must grow in soil. They cannot live 
if they are exposed to the sunlight. And the soil must be 
of the right kind if the plant is to grow well. Then too, 
there must be considerable water in the soil to dissolve parts 
of the soil for the root to absorb. 
As the plant grows older, it sends out a greater number of 
roots. These branch and subdivide and almost fill the soil 
Figure 1.-The Apple Tree in Blossom. 
with their tiny rootlets. They take up about as much space in 
the ground as the branches do in the air. If we could take a 
tree from the ground and not break off any roots, it would be 
something like a dumbbell with our hand grasping the stem 
and at either end the cluster of branching parts. 
4. The Leaf and the Gall Fly. - The leaf of the apple 
tree has a big work to do. It is the principal factory of the 
tree. With the help of the sun it takes the water that comes THE LEAF AND THE GALL FLY 
3 
up through the trunk from the root and combines it with 
some parts of the air so as to form nearly all the material 
that the plant uses. The wood and starch that is in the stem 
and the sugar that is in the apple, as well as the material of 
the leaves themselves, are all made by the thin green leaf. 
Not only must the leaf do this work but it must put up 
with many annoyances, 
at least we should call 
them annoyances if we 
were leaves and they 
happened to us. Leaves 
are tender and, as we 
know, many kinds are 
good to eat. There are 
insects that like to feed 
upon the apple leaf. One 
of the insects is called the 
gallfly, which lays its eggs 
on the leaf. These hatch 
into little worm-like crea- 
tures, which so irritate 
the leaf that it grows a 
little house around them 
to shut them in. Instead 
of harming the gall fly, 
however, this affords him 
food and shelter so that 
even the sharp-eyed birds 
cannot find him. 
There are some other insects, such as the leaf-cutting wasps, 
that cut out portions of the leaves and take them away to 
make nests. Perhaps there are a hundred kinds of insects 
(Figure 2) that feed upon the leaves of apple trees, and, 
of course, the leaf is not able to do its work when it is weak- 
ened by the attacks of insects. 
Figure 2. - Leaf-miners Destroying 
an Elm Leaf. 4 
THE LIFE OF THE APPLE TREE 
5. The Stem and the Borer. - The stem, or trunk, of 
the apple tree supports the leaves, the branches, and the 
fruit, and its strength keeps pace, as a rule, with the added 
burden imposed upon it. In addition to this work it provides 
a path for carrying materials from the roots to the leaves and 
other materials from the leaves back into the roots. The 
trunk is also used for the storage of food. It contains the 
starch which the leaves have manufactured. This is food for 
some animals. 
Figure 3.-The Fallen Apple Tree Undergoing Decay. 
The borer is one of the insects which gnaws its way through 
the trunk of the tree, getting food from the parts it gnaws 
away, and at the same time hiding from the birds that might 
otherwise feed upon it. When many borers eat their way 
through a trunk, it is so weakened that it cannot do its work 
and the tree breaks off and crashes to the ground. Thus, 
the stem, like the leaf, is not able to do its work properly if 
it is attacked by insects. 
6. The Root and the Grub. - Roots distribute themselves 
in proportion to the raw materials in different parts of the THE BLOSSOM AND THE BEE 
5 
soil. Where these substances are abundant, the roots are 
numerous, but where the soil is poor, the roots will not de- 
velop. Strong, numerous roots tend to produce a heavy, 
thick trunk which in turn tends to support strong, vigorous 
leaves. 
Some roots discharge a substance which dissolves mate- 
rials in the soil and thus use materials that otherwise they 
could not use. Roots hunt out the water in the soil and 
sometimes develop a large root system especially for the 
purpose of taking up water. Such a root system may de- 
velop in a water pipe if the root can find a break in it. 
Roots, also, are attacked by animals and insects. The 
woody materials of which roots are composed are a good 
food for some animals that burrow in the soil. Certain 
insects lay their eggs in the branches of trees, and when the 
young hatch, they burrow through the stems, causing them 
to die and drop off, the young insect falling with them. 
When the twig dries up the young insect leaves it, burrows 
into the ground and feeds upon the roots there. The root, 
like the leaf and the stem, cannot function properly under 
these conditions. 
7. The Blossom and the Bee. - When the apple tree is 
seven or eight years old and has a well-developed root sys- 
tem, a fairly strong trunk, and a good showing of branches, 
it begins to blossom. A blossom is the first step in the pro- 
duction of a fruit. 
The blossom contains several parts: The pinkish-white 
color is limited to the small leaf-like parts (petals) which 
serve to attract attention; there is also a sweet fluid (nec- 
tar) ; and numerous minute stamens that produce a yellow 
dust (pollen). 
The nectar serves no direct use for the apple blossom, but 
it attracts bees, which use the nectar to make their honey. 
Bees visit many flowers before they have all the nectar 
they can carry, and in going from flower to flower they carry 6 
THE LIFE OF THE APPLE TREE 
pollen from one to another. This pollen is necessary to the 
proper fruiting of the plant. The bee, therefore, renders 
a real service to the apple tree, for without this transfer of 
pollen from one blossom to another (pollination) very few 
apples would form. In this case we have an insect that is 
not an enemy to the tree but a most necessary friend. The 
blossom is able to do its work much better because it has 
insect friends which use it for their own advantage and in so 
doing render a service to the tree. 
8. The Fruit and the Life Cycle. - When the work of the 
bee is done well and the weather is favorable the base of 
the flower develops into the fruit with seeds inside. The 
apple is green like the leaves, while it is young. It does not 
show color until it begins to form sugar, which makes it 
edible. We might say that the apple was advertising its 
sweetness, so that some animal would eat it and throw away 
the core. As the core contains the seeds, these may then 
find a favorable place to 
grow and may, in time, 
form new plants. This 
brings us back to our 
starting point, and we 
may say the tree has 
completed its life cycle. 
9. The Story of the 
Codling Moth. - The 
material of the apple is 
food for large animals 
that eat it and drop the 
core. It is also food for small animals that live inside of it 
for a time. They not only eat it but they use it for a shel- 
ter and as a protection from their enemies. The "worm" 
so often seen in apples (Figure 4) is the young of the codling 
moth that laid its egg there just as the fruit began to form. 
This worm is called a larva. The larva hatches from the 
Figure 4. -The " Worm " in the Apple. THE STORY OF THE CODLING MOTH 
7 
egg which the moth laid in the little fruit of the apple. Then 
it bores its way into the core and here it eats and grows and 
sheds its skin (molts) un- 
til it is full grown. In- 
side the apple it molts 
three times. Just before 
it is ready to molt again 
it bores its way through 
the side of the apple and 
makes its way to some 
protected spot, where it 
spins a silk-like nest (co- 
coon) around itself. 
After staying in the co- 
coon for a time, it sheds 
its skin once more, but 
this time we do not have 
a larger larva as in previous molts, but a new stage in the 
life of the codling moth begins that is called a pupa (Figure 
5). In this pupa stage, it can take no food, for it has no 
mouth parts and it cannot move about, for it has neither 
legs nor wings. But it can wiggle and can take in air 
through the openings in the sides of its body. The length 
of time it remains in the 
pupa state depends on 
the temperature. Even- 
tually, the fifth molt oc- 
curs, the adult moth 
emerges from the pupa 
(Figure 6), and in a few 
days the females are 
ready to lay eggs in fav- 
ored places. This brings 
us back to our starting point, and we may say the codling 
moth has pnmnlptpd its life cvclp. 
Figure 5. - Pupa of Codling Moth. 
Figure 6.-Adult Codling Moth. 8 
THE LIFE OF THE APPLE TREE 
10. The Story of the Apple Tree Continued. - The ma- 
ture apple tree bears fruit for many years. But insects 
continue to infest it until finally some of its branches decay 
and openings are formed in them where birds find a place 
for a nest. As time advances the branches weaken and the 
winds break off many of them. Decay progresses and even- 
tually the tree weakens and falls. The wood is probably 
saved by the owner, who cuts it up into firewood and pos- 
sibly burns it in a fireplace. 
If we could see it burning, and could understand all that 
takes place during this operation, we should find that the 
work that the leaves did during years of patient labor is 
being rapidly undone by the flame. The substance that 
the leaves took from the air is going up the chimney and 
returning to the air in the same form as the leaves received 
it. This substance is a gas called carbon dioxide. The 
water that the leaves received through the trunk, which in 
turn was taken from the soil by the rootlets, is also going up 
the chimney in the form of water vapor to be returned to the 
earth again when it has been condensed into rain. The 
mineral substances that the rootlets took from the soil in 
solution are found in the ashes. 
We might say that the elements involved in these proces- 
ses have " completed their cycle." For example, the car- 
bon which forms a part of the gas carbon dioxide was com- 
bined with other elements to make the starch in the leaves. 
This was converted into wood and served for a time in the 
trunk or branch or root until the tree decayed and was 
burned. Then through the action of the flame, it was re- 
duced for a time back to carbon and further action of the 
flame joined the carbon and oxygen and it went up the 
chimney as carbon dioxide. All of the carbon, oxygen, and 
other materials of this tree are now in the air and soil, where 
the young apple tree found them. 
When the trunk and limbs are cut into firewood, a short MAN AND BUDDING 
9 
stump is left in the field. The changes that begin to take 
place in the stump are similar to those that occur in the 
fireplace. The wood in the stump is attacked by the ele- 
ments and small plants, the bacteria, and a slow decay be- 
gins (Figure 3). 
After many years, the wood in the stump becomes soft 
and crumbles. In these changes all of the carbon, oxygen, 
and other materials locked up in the stump have been re- 
leased and returned to the air and soil. This would have 
Figure 7. -• Picking Apples. 
Photographed by C. C. Carpenter. 
happened to the entire tree, if man had not wanted the wood 
to burn. 
The apple tree, then, uses oxygen, carbon, water, and other 
substances in order that it may live. The codling moth does 
the same thing except that it obtains its food by eating the 
apple. When the codling moth dies, it decays like the 
stump and the materials in its body break up in a similar way. 
11. Man and Budding. - When we told how the apple 
seed grows into a tree we did not speak of the kind of fruit 10 
THE LIFE OF THE APPLE TREE 
that this tree would bear. As a matter of fact the apples 
from this seed would probably be what is called " native 
fruit," small and sour and wholly undesirable as human 
food. 
Man has found this out and he knows how to avoid it. 
When the tree is small he cuts a bud from an apple tree tha 
he knows to be good. The favorite apples have names t 
distinguish them in the market. Some of the best known 
are the Baldwins, Greenings, Northern Spies, McIntosh 
Reds, Wealthy, Fameuse, Gilliflowers, and Spitzenberg. 
If we wish our little seedling to bear Baldwins, we go to a 
Figure 8.-Successive Steps in Budding. 
Baldwin tree and take a leaf bud and place it in a slit in the 
bark of our seedling (Figure 8). This is called budding. 
If we have been careful, this bud will live and unite with 
the stock upon which we have budded it. Then all the rest 
of the tree above the bud is cut off and we have a tree bearing 
only one kind of fruit. We say it is common stock below 
the bud and Baldwin above. In nurseries thousands of 
these little seedlings a year or two old are budded to pro- 
duce the well-known varieties we have mentioned above. 
These are then distributed to fruit growers throughout the 
country. 
12. Grafting. - There is also another way in which the 
fruit may be changed. This is called grafting. We take MAN AND HIS COMPETITORS 
11 
small branches of the desired tree and cut them wedge- 
shaped. Then we saw off a branch from the tree to be 
grafted, split the end that remains on the tree, and set our 
little branch in the edge of this wedge-shaped opening. If 
the cut parts are covered with grafting wax to keep out the 
water and prevent decay, the little branch will grow and bear 
apples like the tree from which it was cut. Many kinds of 
apples can be grafted on one tree so that one could pick early 
apples, medium ap- 
ples, and late apples 
off the same tree. 
This is possible, but 
impractical. (See 
Figure 9.) 
13. New Varieties. 
Cross-pollination. - 
From time to time 
experimental fruit 
growers seek to im- 
prove the kinds of 
apples that are popu- 
lar. Some apples have unusual flavors that are well liked 
but they do not ship well because they are tender and will 
not stand the jar and shaking of transportation. It is neces- 
sary to cross-pollinate in order to get new varieties. By 
this we mean taking the pollen from the blossom of one 
kind of a tree and putting it on the productive part (stigma) 
of a blossom of another kind. By so doing we try to combine 
the desirable qualities of both kinds of apples. 
14. Man and His Competitors. - As we have seen, man 
is not the only animal that feeds upon the apple. We have 
mentioned the enemies of the leaf, stem, root, and fruit. 
Man must match his wit against these competitors if he is to 
secure a large crop of apples. Against the enemies of the 
leaves he uses a poison spray which kills the larvae and 
Figure 9. - Successive Steps 1-5 in Grafting. 12 
THE LIFE OF THE APPLE TREE 
other enemies of the leaf. At the time the young fruit is 
forming, another kind of poison spray is put on the tree to 
kill the small larvae that would enter the apple. Other 
Figure 10.-High-Power Spraying Machine Used in Orchards and 
City Parks. 
enemies of man and the apple attack the buds before they 
have developed and these must be subdued by a poison 
spray. Even after the apples are picked and stored, there 
is danger of injury to them by insect enemies. These are BIOLOGY DEFINED 
13 
held in check by putting the apples in cold storage, which 
prevents these insects doing further damage. 
We have now seen through our study of the apple tree and 
its various associates just what we outlined in the opening 
paragraph of the book. We have noted (1) how apple trees 
live, (2) how they are related to one another, (3) how they 
depend on the physical world about them, and (4) how man 
can control them. These are the four central ideas in our 
study of biology, which we are now ready to define. 
15. Biology Defined. - Biology is the science that tells 
how animals and plants live. No plant or animal is able 
to live unless it can go through all the changes we have 
just studied in connection with the apple tree. It must 
build up its body, provide for more plants or animals like 
itself, and finally break up into the very materials that origi- 
nally united to form the substance of its body. 
Now that you have gained an introduction to the idea of 
biology through your study of the apple tree, select some 
animal or plant and make a special study of its relation to 
the seasons, to water, to air, to soil, to food, and to man. 
These results should be written up and reported to the class 
from time to time during the year. At the end of the year, 
the observations which each one has been making should be 
turned in. In this way much interesting biological infor- 
mation about the living things in your immediate com- 
munity will be collected. 
PROJECT 
OUTLINE 
Biology, a study of living things 
The story of the apple tree 
The sprouting seed 
The plant and its roots 
The leaf and its enemies 
The stem and the borer 
The root and the grub 
The blossom and the bee 
The fruit and the life cycle 
The story of the codling moth 14 
THE LIFE OF THE APPLE TREE 
Man's work 
Budding 
Grafting 
Cross-pollination 
Man's competitors 
Biology defined 
SUMMARY 
Biology is the study of living things. Most of the important things 
in the world are alive, so it is interesting to see how they live. In study- 
ing this we learn their relations with one another and with the world 
about them, and how we can control them. 
We chose the apple tree for this study because it is so familiar. We 
see how the seed sprouts and the plant sends its roots into the ground 
and its stem into the air to put forth leaves, blossoms, and finally fruit. 
In the fruit is the seed, which starts the life cycle all over again. 
During this growth we see how the apple tree has a constant struggle 
with various insects and how man helps it in this fight by spraying. 
Man also controls the fruit by budding, grafting, and cross-pollination. 
In this way we see the four central ideas of biology: (1) how things 
live; (2) how they are related to one another, and (3) to the world 
about them; and (4) man's control over them. 
QUESTIONS 
Define Biology. What are its four central ideas? How is each of 
these illustrated in the story of the apple tree? What is the chief 
function of the root; the leaf; the stem? Name an enemy of the root; 
the leaf; the stem; the fruit. What insect is helpful to the apple tree ? 
What do we mean by the life cycle 2 Describe the life cycle of the apple 
tree. In what ways does man control the enemies of the apple tree? 
In what three ways does man control the kind of fruit ? 
REFERENCES 
Gager, Fundamentals of Botany, Chapter XI. 
Sinnott, Botany, Principles and Problems, pages 17-20; 23-35. 
Transeau, General Botany, Chapter II. 
Apple Insects and Their Control, Bulletin No. 475, New York. 
Agricultural Station, Geneva, N. Y. CHAPTER II 
IMPORTANT LIFE FUNCTIONS 
It matters not how long we live, but how. 
- Bailey 
16. Life Functions. - We have just studied in a general 
way the life of an apple tree and some of its functions. When 
we inquire more carefully into the way plants and animals 
live, we see that they have several other features or func- 
tions in common. These are called the life functions or 
processes of all living things. They are sensation (irrita- 
bility), motion, respiration, food-taking, nutrition (diges- 
tion, absorption, circulation, assimilation) excretion, and 
reproduction. 
a. Sensation (Irritability). - Animals are sensitive to 
heat, to pain, to light, and to other outside influences which 
we call stimuli. Plants, too, respond to light and other 
stimuli. The response of animals and plants to stimuli is 
called sensation or irritability. It is an important life process 
or function, for it enables them to make the most of their 
location. Because of this function animals and plants are 
able to adapt themselves to their surroundings. 
b. Motion. - All animals can move from place to place or 
move parts of their bodies. The higher animals move with 
ease as a result of highly developed muscular and nervous 
systems. The lower animals are more limited in their move- 
ments. The simpler plants move about in the water and 
at least the leaves of many of the higher plants move toward 
the sunlight, while some, like the hop-vine and morning-glory, 
not only grow but move in a certain definite direction. 
15 16 
IMPORTANT LIFE FUNCTIONS 
Movement, then, in animals and plants is unlike the motion 
of the wind or of a flowing stream, because each living thing 
has to supply from its own body the energy required to 
move. Living things can change the direction and speed 
of their movements, but non-living things cannot. In 
biology motion is defined as the ability of living things to 
change their position without employing the force of the 
wind, or gravity, or similar outside agencies. 
c. Respiration. - All animals and plants require energy 
in order to live. Part of this energy comes from food and 
part from the oxygen used in the process known as respira- 
tion. As a result of respiration the needed energy is ob- 
tained and a gas called carbon dioxide is formed. Respira- 
tion is the introduction of oxygen into cells and the giving off 
of carbon dioxide. Carbon dioxide is made up of carbon and 
oxygen. 
Respiration, which takes place in every living cell, should 
not be confused with breathing. Breathing occurs only in 
the higher animals that have lungs. In breathing, air is 
taken into the mouth or through the nostrils and passes into 
the lungs, and the air in the lungs escapes through the 
mouth or nostrils to the outside. Breathing, then, is merely 
an adaptation to bring the oxygen of the air in contact with 
the blood vessels of the lungs. 
d. Food-taking. - We eat in the morning, at noon, and 
again at night. If we have pets, we feed them regularly. 
The farmer has to feed his cattle, horses, and sheep when they 
are confined in the stables. In summer, when they are 
turned out to pasture, they secure their own food and eat 
at irregular intervals. The fox hunts at night or early morn- 
ing as he captures mice or occasionally steals a chicken. All 
these illustrate another life function, food-taking. 
There are a few plants, like the Venus fly-trap, that can cap- 
ture insects and use their bodies as food. But this is not 
the usual way that plants take food. Food-taking is really LIFE FUNCTIONS 
17 
true only of animals, for the green plants manufacture their 
own food, chiefly in their leaves. 
e. Nutrition. - This function includes first the prepara- 
tion of food so that the animal or plant may have it in the 
form of a solution (liquid). This is digestion. Next, the food 
must be taken into the veins of the animal or plant. This is 
absorption. Then the food must be moved to all parts of the 
animal or plant. This is circulation. And, lastly, each part 
of the animal or plant must take from the blood or the sap 
the food that it needs. This is assimilation. Nutrition is 
the term under which are described the changes through 
which food passes from the time it enters into solution until 
it becomes a part of the living body of an animal or plant. 
f. Excretion. - In a previous paragraph (c) the gas, 
carbon dioxide, was named as a product of respiration. Car- 
bon dioxide is a waste product and is removed from the 
body of higher animals through the lungs and skin. It may 
pass directly into the air from the leaf of a plant or through 
the skin of the earthworm. The manifold activities of living 
things result in the production of other worthless products. A 
worthless or waste product to an animal or plant is one that 
does not yield it energy. Excretion, then, is the elimination 
of the waste products in the bodies of animals and plants. 
The foregoing life processes have to do with the life of the 
animal or the plant itself. There is another life process that 
is important in keeping alive the races of animals and plants, 
namely, reproduction. 
g. Reproduction. - All animals produce young or become 
extinct. It is common knowledge that all living things grow 
old and eventually die. And unless there were some pro- 
vision for producing young, there would be no such thing as 
life. Before the bodies of animals and plants grow old, 
preparation is always made to produce more animals and 
plants like them. This has been the story since the begin- 
ning of life so far as science can determine; and it is the 18 
IMPORTANT LIFE FUNCTIONS 
only means by which there can be any increase in the total 
number of living things. Reproduction, then, is the process 
by which life continues from generation to generation. 
17. Adaptation. - The fundamental functions tell us 
what the parts do in the life of the plant or animal. Adap- 
tation shows how the 
structure responds to ex- 
ternal conditions by 
means of changes in its 
form. 
Every animal and plant 
is particularly adapted 
to its mode of life. 
There are countless ex- 
amples of adaptation. 
The squirrel is a good 
illustration. His toes are 
provided with sharp, 
curved nails that make it 
easy for him to hold fast 
to the rough bark of 
the tree; and, when he 
jumps from branch to 
branch, his tail acts as a 
parachute, so that his 
front feet alight first. 
If a squirrel has more 
food than he can eat at 
once, he takes the nuts 
and buries them in the 
earth. In doing this he uses his front feet for digging a hole 
in the ground while holding the nut in his mouth. Name 
three different ways that the squirrel uses his front feet. 
When you use a fountain pen in what ways is the hand 
adapted to the use of this instrument? First, you take it 
Figure 11.-Squirrel. 
Notice how the squirrel holds the nut 
with his front feet. What use is made of 
the hind feet at this time ? Are his front 
feet being used as hands or feet ? Com- 
pare the tail of the squirrel with the tail of 
a mouse. Of what use to a squirrel is a 
big bushy tail ? Would such a tail be 
useful to a mouse ? Would it be a detri- 
ment ? Why? ADAPTATION 
19 
from your pocket. Then you take the cap from the pen 
with one hand, while you hold it with the other. You place 
the cap on the top of the pen, the fingers exerting just the 
right pressure in removing it and forcing it on the pen. 
Notice how the thumb and first two fingers hold the pen securely. The 
flat wrist gives a good sliding surface and the muscles are so controlled 
that the letters are uniform in size and shape. The nails of the fingers are 
adaptations and can be used to pick up small objects. The numerous joints 
in the fingers make the hand more serviceable. How many adaptative 
features of the hand can you think of ? 
Figure 12. - Adaptation of the Hand. 
Then you take the pen in your right hand and begin to write. 
The pen point is moved in the proper direction to make 
letters, forming accurate loops and curves because the hand 
has been trained to make these lines as you wish. It has be- 20 
IMPORTANT LIFE FUNCTIONS 
come especially adapted to do this work. In all this the 
thumb plays such an important part that man is sometimes 
called the " thumbed animal." 
The various shapes of our teeth permit us to eat a great 
variety of food. In front are the chisel-shaped teeth for 
cutting; then come the tearing teeth on each side; these 
in turn are followed by broad crown teeth that crush and 
grind the food. Most fishes, frogs, and alligators have all 
Figure 13. - Milkweed Seed. 
Distributed by wind. 
their teeth conical in shape. Teeth of this shape serve 
only to hold the captured prey from escaping or to tear the 
flesh. The teeth of such animals do not show as much adap- 
tation as those of man. 
An extreme form of adaptation of the teeth is found in the 
elephant, which has two tusks, often several feet long. These 
tusks are really overgrown teeth and are used for protection. 
The trunk of the elephant is another unique adaptation. It 
is really the nostrils and upper lip greatly drawn out, and 
is used in browsing and in drinking, because the elephant's ADAPTATION 
21 
huge bulk and short neck prevent him from reaching down 
to graze or to drink. 
Did you ever think of the seeds of the maple tree that 
grow large wing-like vanes on the side (Figure 13)? The 
wind carries these seeds away from the parent tree and thus 
they have a better chance to grow. The dandelion and milk- 
weed have downy tufts that carry the seed miles away from 
the place where the parent plant grew. 
Figure 14. - Head of Eagle. 
This shows the adaptation of the beak. 
Many plants have special adaptations that help them to 
climb. The tendrils of the common pea and grape are such 
an adaptation. 
The coconut has a buoyant husk that causes it to float 
in the currents of the ocean perhaps a hundred miles away 
till the waves carry it up on the shore, where it grows into 
a coconut tree. Some plants, like the wild geranium, hold 
the seeds by a spring that throws them several feet. All 22 
IMPORTANT LIFE FUNCTIONS 
these are adaptations that plants employ in distributing 
their seeds. 
The main adaptations that have to do with the individual 
are: (1) those that assist in food-getting, such as the cutting 
teeth of the squirrel or the sharp curved beak of the hawk 
or the eagle (see Figure 14); (2) those that aid in self-protec- 
tion, such as the rapid running of the fox or the color of 
a moth; and (3) those that have to do with their surround- 
ings, such as the fins of the fish, for moving through the 
water, or the wings of the bird, for flying through the air. 
OUTLINE 
Life functions or processes 
Sensation (irritability) 
Motion 
Respiration 
Food-taking 
Nutrition 
Digestion 
Absorption 
Circulation 
Assimilation 
Excretion 
Reproduction 
Adaptation 
Specific illustrations 
The squirrel 
Paws 
Tail 
The human hand 
Teeth of animals 
Wings of seeds 
General principles 
Food-getting 
Self-protection 
Surroundings or environment 
SUMMARY 
In this chapter we learn that all living things have certain life pro- 
cesses or functions in common. Two of these, sensation and motion, 
may seem at first less vital than respiration, food-taking, nutrition, and 
excretion, but really all are essential, for without the power to feel and to 
move the other processes could not be carried on. 
While these functions have to do with the life of the plant or animal 
itself, reproduction continues that life from generation to generation. 
Adaptation is not a life process, but it is a very important phase of life, 
for everything in life is adapted in one way or another to the work it 
has to perform. This we see in the paws, teeth, and tail of the squirrel, 
the human hand, and even in the wings of some seeds, which are adapted 
to distribute them over wide areas. Most adaptations are to help in 
food-getting or in protection, or else in adjusting the plant or animal to 
its surroundings. REFERENCES 
23 
QUESTIONS 
What are the life processes or functions? Do some seem more 
important than others? Are they in reality more important? What 
are the four processes of nutrition? Is reproduction a life process? 
Is adaptation? What adaptations has the squirrel for food-taking? 
For motion? What special adaptations has the human hand for the 
enormous variety of things it can do? Give other examples of adap- 
tation in plants and animals. What are the three main objects of the 
various adaptations of plants and animals? 
REFERENCES 
Coulter, Plant Relations, Chapter I. 
Smallwood, Man - The Animal, Chapter XI. 
Woodruff, Foundations of Biology, Chapter I. CHAPTER III 
COMPOSITION OF LIVING THINGS 
The dust we tread upon was once alive. 
- Byron 
18. Matter, Organic and Inorganic. - We have seen 
that all living things carry on certain life functions. In this 
respect plants and animals are alike. These life functions 
are carried on by means of certain organs. For this reason 
all living things are called organisms, and are said to be 
composed of organic matter. 
We cannot say this about water, rocks, soil, air, or iron. 
These substances are all non-living and are called inorganic. 
Wood, sugar, meat, oil, and coal are likewise dead, but each 
of them was part of some living organism before it became 
wood, sugar, meat, oil, or coal. How many other kinds of 
organic matter can you name ? 
Plants and animals each take into their bodies inorganic 
matter and make it a part of their bodies. These inorganic 
materials are then in the living substance and as long as 
they remain there, they are properly described as organic. 
The story of the apple tree and the codling moth revealed 
that all of the material in the bodies of these two organisms 
was eventually returned to the soil and air. 
We shall have more to say about the terms organic and 
inorganic in the discussion of elements, compounds, and the 
materials of which organisms are composed. 
19. Elements and Compounds. - The bodies of plants 
and animals as well as the earth and air are composed of a 
24 FORMS OF MATTER 
25 
great variety of elements and compounds. An element is a 
form of matter which cannot be broken up into simpler 
substances. Iron, carbon, oxygen, copper, and gold are 
elements. 
A compound is a chemical combination of two or more 
elements in which each loses its distinctive properties. 
Water, sugar, olive oil, the white of an egg are compounds 
because each contains two or more elements united ac- 
cording to the laws governing chemical combinations. The. 
starch found in wheat, potatoes, and corn is a compound of 
three elements, namely, hydrogen, carbon, and oxygen. 
Water is a compound made up of hydrogen and oxygen. 
Compounds are more numerous in nature than the elements. 
In fact, there are many thousands of compounds, while 
there are fewer than ninety elements. 
A mixture is a blending of materials, in which each keeps 
its own nature and properties, as in lemonade. A mixture 
differs from a compound in that it is not formed by chemical 
action, and the elements of which it is composed do not 
lose their special properties. 
20. Forms of Matter. - The elements and compounds 
which have just been discussed exist either as a gas, a fluid, or 
a solid. Each of these forms of matter has a technical mean- 
ing but for our purposes in understanding life processes, the 
following simple definitions are sufficient. A gas has neither 
definite size nor shape. There are no limits to the amount 
of expansion that may take place in it. The minute par- 
ticles of which it is composed can move in any direction. If 
gas is confined in a glass bottle, the limits of its expansion 
will be the sides of the bottle. Air, steam, and hydrogen 
are gases. 
A liquid has definite size, but takes the shape of the vessel 
containing it. The particles of which it is composed move 
over one another without any apparent resistance. It is 
not capable of indefinite expansion, and if placed in a bottle 26 
COMPOSITION OF LIVING THINGS 
it would not fill the entire bottle as would a gas. Water, 
milk, and oil are liquids. 
A solid has definite size and shape and offers resistance 
to any change of these. In solids the particles are so firmly 
united that they are not easily separated. Such bodies 
retain their form independently of their surroundings. Sugar, 
wood, or rock are illustrations of solids. 
21. Elements in Organisms. - Of the twenty-nine differ- 
ent elements that have been found in organisms, sixteen 
occur infrequently. The remaining thirteen are commoner 
and are believed to be essential to life. They are ox'ygen, 
carbon, hy'drogen, nitrogen, calcium, phos'phorus, sulphur, 
potas'sium, magne'sium, iron, sodium, chlorine, and sil'icon. 
It is interesting to note that these same elements are also 
the most numerous in lifeless things such as rocks, water, 
and the atmosphere. 
22. Oxygen. - Oxygen is a gas which makes up a large part 
of the air. It is the element in the air which sustains life 
in animals and plants. Without it they cannot live. When 
given an undue amount of it, they develop at an abnormal 
rate. It forms about seventy per cent of the bodies of 
plants and animals. 
The most striking property of oxygen is the ease with 
which it unites with other substances. Practically all cases 
of burning are caused by oxygen uniting with paper, wood, 
coal, or some other material. If a piece of glowing charcoal 
is placed in a jar of oxygen, it bursts into flame. This is 
the test for oxygen. 
23. Carbon. - Carbon is, next to oxygen, one of the most 
important elements in biology. It combines with hydrogen 
and oxygen to form sugar, starch, fat, and wood. It is usu- 
ally black and solid and is best seen as the charred remains 
of certain foods that have been overheated but not burned 
up, as when toast or meat is " burned." Carbon forms about 
fourteen per cent of the body of plants and animals. NUTRIENTS 
27 
24. Hydrogen. - Hydrogen gas is the lightest of all sub- 
stances. It is found in nature combined with other elements 
entering into the composition of water, animals, and plants. 
It forms a little less than ten per cent of the bodies of organ- 
isms. It is an odorless, colorless, and tasteless gas. 
25. Nitrogen. - Nitrogen is a gas which - unlike oxygen 
and hydrogen - does not burn. It dilutes the oxygen of the 
air and so makes it less active. Nitrogen forms less than 
three per cent of the body of plants and animals. Calcium, 
sulphur, phosphorus, iron, potassium, chlorine, silicon, and 
magnesium are the other important elements found in living 
things. None of these elements forms as much as one per 
cent of the body of plants or animals. 
The human body is made up of: 
oxygen 72. parts 
carbon 13.5 parts 
hydrogen 9.1 parts 
nitrogen 2.5 parts 
calcium 1.3 parts 
phosphorus 1.15 parts 
sulphur .147 parts 
potassium .026 parts 
iron .01 parts 
26. Nutrients. - The elements above, while forming the 
body structure, are not taken directly as food. The foods 
we commonly use have these elements in combination with 
other materials. The foods that contain the proper ele- 
ments are spoken of as nutrients or food compounds. These 
nutrients are starches, sugars, proteins, edible fats, and 
mineral matter. 
a. Starch. - Starch is a nutrient that occurs in many of 
our foods. Potatoes, corn, wheat, rye, rice, and most of the 
vegetable foods contain large amounts of starch. Starch 
is easily changed to glucose by the digestive fluids. It fur- 
nishes some of the energy of heat and motion for the body. 
6. Grape Sugar. - Grape sugar or glucose is a nutrient 
that occurs in grapes and in most other fruits. It is slightly 
different in composition from cane sugar or beet sugar. 28 
COMPOSITION OF LIVING THINGS 
Starch is always changed into glucose by the digestive fluids 
and never into cane sugar. The food value of both glucose 
and cane sugar is high. They are used by the body to fur- 
nish the energy of heat and motion. 
c. Enzymes. - In the preceding paragraph it was said 
that the digestive fluids change starch into glucose. For 
many years it was not known what substances in the digestive 
fluids cause them to do this work. Now it is known that cer- 
tain chemicals called enzymes, secreted by living cells, are 
the real active agents in digestion. The enzyme that 
changes starch to glucose is called diastase. Pepsin is an 
enzyme that digests protein. There are many other en- 
zymes. An enzyme is not changed by digestion, so that a 
very small amount of it. digests a large amount of food. 
d. Proteins. - Proteins are nutrients that are found in 
great variety in our food. The proteins differ from starch 
and sugar in having nitrogen in combination with other 
elements. The characteristic element of protein is nitrogen. 
Each kind of protein has its own name. The protein in 
wheat is gluten; in beans it is legumin. Casein is the protein 
in milk and myosin is the protein in meat. The proteins are 
necessary in building and repairing the cells of animal bodies. 
If more proteins are eaten than necessary for this work, the 
surplus may be oxidized to furnish the energy of heat and 
motion or stored as fat. 
e. Edible Fats. - The term edible fats is used to include 
both fats and oil. These nutrients are almost wholly energy 
producers. They are used chiefly to produce heat. As 
we go north or south from the equator, we find the native 
people adding ever greater amounts of fats to their diet, 
until we come to the Eskimos, who eat large quantities of 
pure fat with relish. Large amounts of fat are necessary 
to keep the body warm in the very cold zones. 
27. Water. - This inorganic substance is not a food in 
the sense that it is broken up and digested as are real foods. MINERAL FOODS 
29 
Because of its power to dissolve almost everything that is a 
part of animal or plant life, it is called a universal solvent 
and all foods are put into the form of solutions by the use 
of water. Blood is water in which are floating red and white 
cells and a great variety of foods and wastes. The tissues 
of animals and plants are soft in large part because of their 
water content. Our bodies consist of over seventy per cent 
water; there is some water even in bones. Water is nec- 
essary in the distribution of foods in all living things and in 
the removal of liquid wastes. The habits of wild animals 
which frequently travel long distances for water, and the 
severity of human suffering when water gives out as it some- 
times does in the crossing of a desert, indicate how necessary 
water is in the daily life of higher animals. Animals are 
killed when the water in their tissues is frozen or when it is 
withdrawn in extreme evaporation. 
Water is so familiar to us all that no special tests are 
necessary to identify it. It is easily resolved into the two 
gases, oxygen and hydrogen, which are united in the propor- 
tion of two parts of hydrogen to one of oxygen. 
28. Mineral Foods. - In addition to the nutrients al- 
ready mentioned which were starches, sugars, proteins, and 
edible fats, there are many minerals, that are necessary for 
the proper development and growth of animals and plants. 
The essential elements of these mineral foods are: iron, 
sodium, potassium (potash), calcium, sulphur, and phos- 
phorus. 
Iron is necessary as a part of the red blood cells to enable 
them to carry oxygen from the lungs to all parts of the body. 
Sodium is needed to help the cells of the body to perform 
their work properly. Potassium (or potash as it is com- 
monly called) is particularly necessary for the growth of 
plant cells and to a less extent animal cells. Calcium is a 
prominent part in the make-up of bones for animal skeletons, 
including the shells of clams and oysters. Phosphorus con- 30 
COMPOSITION OF LIVING THINGS 
tributes to the growth of cells of animals and is an im- 
portant plant food. 
Many foods that are deficient in starch, sugar, or protein 
are valuable because of the mineral foods they contain. 
For example, prunes contain iron, sodium, potassium, and 
phosphorus. Spinach has iron and sodium. Carrots have 
sodium and calcium. Peanuts have phosphorus and cal- 
cium. The foods just mentioned, along with many others, 
are necessary foods because of their mineral content and 
also because they are rich in what we call vitamins. 
29. Vitamins. - The terms proteins, fats, carbohydrates, 
water, and mineral food do not completely describe all of the 
conditions that are necessary in a satisfactory diet for living 
things. There has recently been discovered a series of sub- 
stances which are known as vitamins. Just what these sub- 
stances are no one has found out but they can be proved 
to be present in our ordinary foods like milk, tomatoes, 
fruit, and lettuce. They will be discussed more in detail on 
page 304. 
30. Organic Ash. - When coal is burned in the furnace, 
or wood in the stove, there remains a grayish product known 
as ash. In a similar way we should understand that in the 
burning of fuel in the body of organisms there are waste 
products which we might include under the comprehensive 
term of organic ash. 
31. Physical and Chemical Change. - If a solid piece 
of ice is melted, it becomes liquid water. If the liquid water 
is boiled, it becomes steam or vapor, a gas. If the steam is 
condensed, it becomes water, which in turn may again be 
frozen into ice. Any change in a substance, which does not 
alter the material of which it is composed, is called a physical 
change. 
On the other hand, when oxygen unites with wood, the 
wood burns, giving off heat and smoke, and ash remains. 
But this ash cannot be united with heat and smoke to form ENERGY 
31 
the original wood. Such a change as is seen in the burning 
of wood is called a chemical change. 
32. Energy. - Heat results from the burning of a candle 
or from the burning of fuel in the body of organisms. In 
this burning energy is set free. The heat from the burning 
candle is due to a rapid movement in the particles of the 
candle that is burning. The heat in organisms is due to a 
similar movement in the particles of pro'toplasm.1 All of 
the material of our physical universe is in constant motion. 
These movements may be large enough to be seen or so 
small that we recognize them as heat only. They are also 
the source of light. 
Energy is defined as the power to do work. It exists in two 
forms; active or kinetic, and stored or potential energy. 
Kinetic energy is the energy which a body has on account of 
its being in motion. Kinetic energy may be used in starting 
matter in motion, or in raising its temperature, or in altering 
the position of a body, or in producing chemical changes. 
Potential energy is inactive energy such as the water 
stored or restrained by a dam, or the fuel properties in wood. 
The stretched watch spring in a watch has potential energy. 
An object cannot have potential energy except as the result 
of the previous expenditure of energy upon it. 
The movements in animals and plants, the heat utilized by 
them, the growing of new parts, in short, all of the life pro- 
cesses depend upon energy. Not only are living things 
dependent upon energy to sustain life, but they are influenced 
by such forms of energy as heat, light, mechanical energy, 
and gravity acting upon the entire organism from without. 
a. Temperature is an important factor in the life of organ- 
isms because in nearly all instances their life functions are 
possible only within rather narrow ranges of temperature. 
1 The word protoplasm comes from two Greek words meaning first form. 
It is the original, simple material of which the cells (see page 44) of plants 
and animals are made up. 32 
COMPOSITION OF LIVING THINGS 
In general, life is possible only between freezing and boiling 
temperatures. Some living things can be temporarily 
frozen, for example the frog and certain fish, and later be 
revived, while a few of the lower plants live in the hot springs 
in Yellowstone National Park. But for most organisms 
these extremes are fatal, and we find them living best within 
a limited range of temperature. 
The effect of temperature on life may be readily seen in the 
case of hens' eggs. In cold storage they will keep for months, 
but at the proper temperature they hatch into chicks in a 
few weeks. 
b. Light has a direct influence on many plants, though 
not all parts of the higher plants respond to light. As a 
general rule the stem turns toward the light and the roots 
away from it, while the leaf will turn so as to expose its 
broad surface to the direct rays of light. It is important 
to remember that many living things are active only in the 
absence of light, or, as we commonly say, at night. It is 
hard to separate entirely the influence of light from that of 
heat because the two are constantly present, to a greater 
or lesser degree. 
A striking illustration of the effect of light on the growth 
of living things is found in our dense forests. Spruces sur- 
rounded by large trees, thirty to fifty feet high which com- 
pletely shut off the sunlight have been found to grow only 
six or eight feet in fifty or sixty years. 
c. Motion. - The influence of motion or mechanical 
energy on the life of organisms is easily demonstrated to 
those who have an opportunity of studying the life in a 
rapidly flowing brook or observing isolated trees growing on a 
wind-swept hill. If the winds are largely in one direction 
such trees will have reduced the size and number of their 
limbs on the side from which the prevailing wind comes and 
will have much longer and more numerous limbs on the 
opposite side. The normal growth of plants can be greatly CONSERVATION OF ENERGY 
33 
altered if they are placed upon artificially moving platforms. 
The extent of the alterations will depend on the rate at which 
they are artificially moved. 
d. Gravity. - Gravity is the attraction of the earth for 
all bodies. It is a form of energy that acts all the time and 
does not vary in amount. In this respect it differs from 
temperature, light, and motion. Stems tend to grow away 
Gravity pulled this spruce tree down, but it did not uproot it. Its stem still 
tends to grow away from the force of gravity. 
Figure 15. - The Force of Gravity. 
from the force of gravity and roots to grow towards the cen- 
ter of the earth. 
33. Conservation of Energy. - Every time that we wind 
a watch, we transfer the kinetic energy of our hand into the 
potential energy of the watch spring; and this potential 
energy in the watch spring in turn passes into kinetic energy 
in moving the hands of the watch. Thus energy is passed 
on and conserved. Let us see if we can apply this same idea 
to living things. 34 
COMPOSITION OF LIVING THINGS 
The light of the sun enables plants to grow and store up 
food in the form of sugar and starches. Ages ago there was 
a very luxuriant growth of plants in certain districts where 
coal is now' found. These plants shed their numerous 
leaves, w'hich were gradually changed into peat, and later 
covered by sand and clay and subjected to great pressure 
and heat. Under these conditions this organic plant mate- 
rial was transformed into coal. The ways in which this 
potential energy in the coal can be used serve as an illustra- 
tion of the conservation of energy. 
The light of the sun made plants grow which were later 
transformed into coal. The coal is burned under the boiler, 
making the steam which runs the engine. The engine turns 
a dynamo and produces electricity. The electricity is 
passed through a small wire in an electric bulb and fur- 
nishes light. Thus the light of ages ago is again made into 
light by this long process. 
It has traveled in a circle so to speak. Energy may be con 
verted into various forms. Electricity may be changed to 
heat, as in the electric flat-iron; into light, as in the electric 
bulb ; or into motion, as in the trolley car. One form may 
thus be converted or changed into another form of energy. 
If energy is used in one form, it will appear in some other 
form. Energy cannot be created or destroyed. This is the 
law of the conservation of energy. 
34. Conservation of Matter. - There is a similar law in 
regard to matter. That, too, cannot be destroyed. When 
a paper burns, it disappears as paper, but the matter of 
which it consisted still exists in the form of the ash w'hich is 
left and the gases which passed off during the burning. 
OUTLINE 
Matter 
Kinds 
Organic 
Inorganic 
Composition 
Elements 
Compounds 
Mixtures QUESTIONS 
35 
Forms 
Gas 
Liquid 
Solid 
Important Elements 
Oxygen 
Carbon 
Hydrogen 
Nitrogen 
Nutrients 
Starch 
Grape sugar 
Enzymes 
Protein 
Fats 
Mineral foods 
Water 
Vitamins 
Organic Ash 
Physical and Chemical Change 
Energy, Kinetic and Potential 
Temperature 
Light 
Motion 
Gravity 
Conservation 
Of energy 
Of matter 
SUMMARY 
In this chapter we have seen how all matter, whether organic or in- 
organic, is made up of certain elements. There are a great many of 
these elements, but the most important ones in our study are oxygen, 
carbon, hydrogen, and nitrogen. These four make up a large part of 
the human body. Elements and compounds may be gases, liquids, 
or solids. 
Food is required to maintain these elements in the body. The nu- 
trients contained in food are the starches, sugars, edible fats, proteins, 
and mineral matter. Besides these there are certain body-regulators 
that are not classed as nutrients. These are water, vitamins, and or- 
ganic ash. 
These nutrients must go through certain physical or chemical changes 
to produce energy in the body. Active energy is called kinetic, stored 
or latent energy is called potential. There are many forms of energy 
such as heat, light, motion, and the pull of gravity, but energy can be 
neither created nor destroyed. And the same thing is true of matter. 
QUESTIONS 
What is the difference between organic and inorganic matter? 
Illustrate each. What is an element? Name several important ones. 
What is the difference between a compound and a mixture? In what 
forms is matter found ? Is air a gas ? Is steam ? What four elements 
make up the bulk of the human body? Name the chief nutrients. 
How is starch changed into grape sugar? What is the chief function 
of proteins? Of fats? How does water help the nutritive processes? 36 
COMPOSITION OF LIVING THINGS 
What is the value of mineral foods? Name some foods containing 
vitamins. 
What is the difference between physical and chemical change? 
What is energy? What is the difference between kinetic and potential 
energy? Is life dependent upon energy? Why? Name four impor- 
tant forms of energy. How does each one influence life? Explain 
the conservation of energy. Of matter. 
Cockerell, Zoology, Chapter I. 
Snyder, Chemistry of Plants and Animals, Chapters I-IX. 
REFERENCES CHAPTER IV 
THE GREEN PLANT AS A FOOD FACTORY 
Man is dependent upon plants, which alone are able to manufacture 
food from the inorganic world. 
- Atwell 
35. Introduction. - We have studied the life functions 
(Chapter II) and the composition of living things (Chap- 
ter III). But all life is dependent on food, and all food 
comes originally from the green plant. For this reason we 
are now to take up the study of the green plant, and to see 
just how it manufactures food. 
36. The Green Plant. - Plants and animals require 
food for warmth, growth, movement, and the other life 
functions. laving things are continually using up the ki- 
netic energy which they get from foods or nutrients. If life 
is to continue, there must be somewhere in nature a place 
where food is manufactured. This place is the green plant. 
To illustrate this any green plant is satisfactory. The 
leaves of the apple tree which we studied in the first chapter 
will do. This process or function of manufacturing food 
is not present in animals or in the colorless plants. It is 
different from all the life functions defined in paragraph 
15 and must not be confused with any of them. 
37. Photosynthesis. - The primary activity of the green 
apple tree leaves is to manufacture food. In order to dis- 
tinguish this process from all other life functions a special 
term is applied to it, that is, photosynthesis. This word is 
from the Greek, phos, light, synthesis, composition, and 
means putting together through the influence of light. 
37 38 
THE GREEN PLANT AS A FOOD FACTORY 
The raw materials which are used in this activity are water 
and carbon dioxide,1 which are the waste products of oxida- 
tion. (Paragraphs 21-22.) The energy required to unite 
these two compounds is derived from the sun. 
The water enters the roots of the apple tree, passes up the 
stem, into the branches and finally into the leaves. No 
water is obtained directly from the atmosphere. Only a 
relatively small portion of the water 
actually taken up by the roots is 
used in food manufacture as the 
greater part passes off from the 
leaves. 
The carbon dioxide used is de- 
rived almost entirely from the air 
where it is always present. The 
supply in the atmosphere is con- 
stantly being augmented as the re- 
sult of oxidation in animals and 
plants, as well as in the non-living 
world, as, for example, in the rust- 
ing of iron. 
The means by which these mate- 
rials are combined is a green pig- 
ment, called chlorophyll, which is 
located in a special body or struc- 
ture called the chloroplast (Greek, 
chloros, green; plastic, form). In the leaves of the apple tree 
these tiny green bodies (Figure 16) are numerous and round 
in shape. 
Figure 16. - Cell from Fern 
Showing Chloroplasts (c) 
and Nucleus (n). 
1 When a fuel is burned, the chemical element, oxygen, unites either with 
the chemical element, carbon, or with the chemical element, hydrogen. 
When there is as complete a union of the oxygen and carbon as is possible, 
a gaseous product, carbon dioxide, is formed. This product is also known 
under the name carbonic acid gas and you are familiar with it in the bubbles 
of soda water. The oxygen that unites with the hydrogen forms water. 
Carbon dioxide and water, two of the products resulting from the burning 
of fuel, are described as inorganic. CARBOHYDRATES 
39 
38. Carbohydrates. - Foods consisting of carbon, hydro- 
gen, and oxygen are called carbohydrates. One of the first of 
them that is manufactured is grape sugar, which is the basis 
on which the plant builds the remaining food nutrients. In 
the manufacture of sugar the oxygen which is not needed 
is released and given off to be used by either animals or 
plants in respiration. 
It requires energy to combine water and carbon dioxide 
into sugar. Before this new combination can be made each 
of these substances must be separated, for in the new com- 
bination not all of the oxygen is needed. The energy for 
this process is derived entirely from light. 
The importance of photosynthesis can hardly be over- 
estimated. Through this special life process in green plants, 
pdtential energy is again made available in food. The 
green plant uses in its life processes some of the food which 
it has manufactured. This is the reason why the term 
food-taking does not apply to the green plant. The green 
plant manufactures a great deal more food than it needs for 
its own life processes, and this excess is stored in various parts 
of the plant. 
The insects feeding on the leaf, the stem, and the root 
of the apple tree were absorbing some of this extra energy 
which the apple tree had manufactured and stored in leaf, 
stem, and root. Man and other animals eat the apple 
which could not grow without the food-factories in the 
leaves. 
Demonstration of Photosynthesis. - To show that light is necessary 
for photosynthesis, fasten thin discs of cork to the upper and under 
sides of a leaf with clips, completely shutting off the light. Stand the 
plant in the bright light for half a day, then remove the corks from the 
leaf and the leaf from the plant. 
Heat enough 60% alcohol to cover the leaf in a shallow glass dish. 
This may be done by setting the dish in hot water. Keep hot for half 
LABORATORY WORK 40 
THE GREEN PLANT AS A FOOD FACTORY 
an hour, or until the chlorophyll is removed from the leaf. Turn off 
the alcohol and put drops of weak iodine on the leaf. Note that the 
circle covered by the cork discs shows little starch or none, as indicated 
by the faint blue color or by lack of color. 
Make a similar test by comparing a leaf from a plant that 
has been in the dark twelve hours with one that has stood 
in the bright light for the same time, using alcohol to remove 
the chlorophyll and iodine as a test for the presence of 
starch, as before. 
39. Oxidation. - Oxidation means burning. It is the 
uniting of oxygen with any substance, and the giving off of 
carbon dioxide. We are all familiar with physical oxida- 
tion, as in the burning of a match or paper, where it is ac- 
companied by flame, smoke, and heat. 
Physiological oxidation takes place in all active organisms. 
It is a slow process without flame or smoke, but there is 
always heat, although this may not be apparent. Carbon 
dioxide and water are set free in this process much as they 
are when coal burns in a furnace. 
We burn coal to keep us warm, to prepare our food, or run 
our machinery. We light a candle or an electric lamp to 
give us light. In all such cases the object is secured through 
the release of energy. When this energy has been released, 
we speak of it as heat or light. Oxidation in organisms is 
similar. In animals it is the source of heat and muscular 
power. An organism cannot carry on its life processes with- 
out using energy, but some very simple forms of life can 
stop using energy for months or even years. Thus some 
seeds of plants can be kept for two or three years but the 
statement that some seeds can live for hundreds of years is 
not true. These forms of life that temporarily cease carrying 
on their life functions are much like a clock that is wound 
up but not running. The potential energy is there and is 
only waiting for the necessary forces or conditions to re- 
lease it. DIGESTION 
41 
LABORATORY WORK 
Demonstration of Oxidation. - Take equal parts of potassium 
chlorate and manganese dioxide and fill a test tube half full. Hold 
the test tube over an alcohol or gas flame by means of test-tube holder. 
As soon as gas seems to be coming off from the mixture, insert a glow- 
ing match into the end of the test tube. Notice what happens. 
Take a piece of picture wire and, after heating it, dip it in powder 
of sulphur. Heat it again until it burns and then place the burning 
end in the test tube containing the heated mixture. What happens ? 
Each of these operations illustrates oxidation in a striking manner. 
40. Digestion. - The food energy which the codling moth 
larva secured by eating part of the apple would never be of 
any advantage unless it was digested. The energy stored 
in the leaf, the stem, and root of the apple tree, likewise, has 
to be digested before it can be utilized by the apple tree. 
Digestion is the process of converting an insoluble food into 
a soluble form. The common nutrients all need to be made 
soluble before their energy can be used in a living organism. 
These changes are brought about by certain substances 
called enzymes or ferments. In plants they are produced by 
the living cells and in higher animals by the digestive glands. 
Their importance may be better understood from the illustra- 
tion in the following paragraph. 
Starch is a common food that requires digestion. It is 
easily changed to glucose (grape sugar) by the digestive fluids. 
Cducose is an easily absorbed nutrient of high food value, 
that occurs in grapes and in most other fruits. The enzyme 
that changes starch to glucose is called diastase. There are 
many other enzymes; pepsin is the one that digests pro- 
tein. An enzyme is not changed by digestion, so a very 
small amount of it digests a large amount of food. 
LABORATORY WORK 
Demonstration of Digestion. - Artificial pancreatic juice is made by 
mixing 10 grains (1 gram) of commercial pancreatin and 20 grains 
(2 grams) of baking soda in 200 cubic centimeters of water. 42 
THE GREEN PLANT AS A FOOD FACTORY 
lake 10 cubic centimeters of the artificial pancreatic juice in a test 
tube and to it add corn-starch paste. Set for two hours in a place 
where body temperature can be maintained. Test for grape sugar. 
This is done as follows: Add to the fluid in the test tube twice as much of 
Fehling's solution.1 Gently heat the test 
tube until the contents turn first yellow 
and then brick-red. Grape sugar is the 
only substance that gives this color reac- 
tion. 
Apply Fehling's solution to some corn- 
starch paste. Do you get the same color 
reactions? The changes which the arti- 
ficial pancreatic juice caused are the same 
as those that take place in digestion. There 
are other digestive juices each of which 
acts on a definite kind of food. These 
changes are presented in detail in later 
sections. 
41. Osmosis. - All foods and 
gases that man, animals, and plants 
require enter the cells in the form 
of solutions. Foods of the higher 
animals are held in the stomach or 
intestine until they are able to pass 
through the lining membrane and 
eventually into the blood. Plant 
roots take from the soil minerals in 
solution to be used by the plant. 
In both cases the process is the 
same. Solutions pass through these animal or plant cells 
before they can be used. In the case of plants, for example, 
Figure 17. -Osmosis. 
The water in the glass 
passes through the egg- 
membrane and forces the 
egg-white up in the glass 
tube; while the egg-white 
does not pass out into thesur- 
1 Fehling's solution is made by taking 
(1) Copper sulphate 34.5 grams 
Water 500 cc. 
Set aside until completely dissolved. This is solution number 1. 
(2) Rochelle salts 173 grams 
Caustic soda 50 grams 
Water 500 cc. 
This is solution number 2. 
Do not mix until ready to use, then take equal parts of each. REFERENCES 
43 
absorption of water and minerals and also of gases takes 
place in the root hairs. There is a transfer or movement of 
these substances through the cell wall from the soil, and this 
process is called osmosis. 
In addition to the passage of water and minerals through 
a membrane in animals and plants there is also the passage 
of the dissolved gases, foods, and wastes. To summarize, 
osmosis is the passage of solids and gases in solution through 
a membrane. 
OUTLINE 
The Green Plant 
Photosynthesis 
Carbohydrates 
Demonstration 
Oxidation 
Demonstration 
Digestion 
Demonstration 
Osmosis 
All life depends on food, and all food comes originally from the green 
plant. In fact the chief function of the green plant is to manufacture 
food, which it does by a process known as photosynthesis. 
These food products, largely carbohydrates, are digested by means 
of enzymes. They are then absorbed by the process of osmosis, after 
which the fats and sugars are oxidized or burned in the body. 
SUMMARY 
QUESTIONS 
Why is the green plant so important to us ? What is photosynthesis ? 
Describe the process in detail. How is carbon dioxide formed? Of 
what are the food products called carbohydrates composed? What 
is oxidation? What other process does it resemble? How is food 
digested? Describe osmosis. 
REFERENCES 
Gager, Fundamentals of Botany, page 33. 
Sinnott, Botany, Principles and Problems, page 69. 
Stiles, Human Physiology, Chapter XI. 
Transeau, General Botany, Chapter V. CHAPTER V 
THE PHYSICAL BASIS OF LIFE 
For men to tell how human life began 
Is hard; for who himself beginning knew? 
- Milton 
In the previous chapters we have studied the important 
life functions and the composition of living things. We 
have also seen how food is manufactured in the green plant 
so that life may continue. We have referred to cells, but 
without giving a detailed explanation. We are now to take 
up a careful study of the 
cell, the unit of both struc- 
ture and function in all 
living things. 
42. The Cell. -When 
we take apart a plant or 
an animal we find that we 
can separate the parts 
until we come to a unit 
so small that it can be 
seen only through a 
microscope. These tiny 
units are called cells and 
are alike in the following respects: each one has a clear 
outer portion called the cell wall which incloses a mass of 
substance known as protoplasm (see page 31, footnote, and 
section 44, page 46). The protoplasm is made up of two 
parts. These are the cy'toplasm (Greek, kitos, hollow place; 
plasma, form), which is surrounded by the cell wall and 
Cell Wall 
Cytoplasm 
Nucleolus 
Nucleus 
Figure 18. - A Cell. 
44 TISSUES AND ORGANS 
45 
contains a sac-like body, the nucleus (nu'kle-us: Latin, 
nucleus, kernel, nut). The nucleus usually contains one or 
more separate bodies called nucleoli (nu-kle'6-li). A cell is 
defined, therefore, as a mass of protoplasm composed of cyto- 
plasm and nucleus (Figure 18). Cells are so small that 
there are probably several hundred million of them in every 
human body. 
The first man to give the name cell to a definite structure 
was the Englishman, Robert Hooke, who in 1667 made a thin 
slice of cork and placed it under a lens. He saw minute 
cavities in the cork 
which he called cells. 
What he really saw was 
the dead cell wall, and 
it was nearly a hundred 
years later before the liv- 
ing material in a cell 
was recognized and de- 
scribed as protoplasm. 
43. Tissues and Or- 
gans. - The cells are of 
many shapes and sizes, 
and in the bodies of all 
but microscopic plants 
and animals they are 
united to help the plant or animal carry on its life processes. 
This union of cells to do a certain work is called a tissue, 
which is usually defined as a group of similar cells that do a 
similar work (Figure 19). 
In all the higher animals the tissues are united into skin, 
arms, stomach, liver, lungs, kidneys, teeth, hair, and so on, 
or in plants into leaf, branch, stem, root, or flower. Such 
structures are called organs. An organ is a group of tissues 
that do a given work in the animal or plant. Organs form 
the parts of organisms (see page 24). 
Figure 19. - Similar Cells United to 
Form a Tissue. 
Compare these cells with the one shown in 
Figure 18. 46 
THE PHYSICAL BASIS OF LIFE 
44. Protoplasm. - We have referred in section 42 and 
in the footnote on page 31 to protoplasm. This is the word 
used to describe the living material in all cells, in all living 
things. Protoplasm does not exist except in cells. One 
would expect that a substance so universally present in living 
things would be easy to describe. But it is hard because 
the living organism has to be killed before it can be studied. 
Protoplasm may best be described by comparing it with 
a familiar object, like the white of an egg, which is not proto- 
plasm. 
Protoplasm is a jelly-like substance that is neither a solid 
nor a liquid. It is usually colorless or slightly yellow. It 
can be stretched and when released, will, like rubber, con- 
tract. In appearance it is often clear though it may be 
opaque, and it may have either a fine granular appearance or 
a foamy structure like soap bubbles. 
It is in the protoplasm that all of the life functions occur 
and for this reason it is called the physical basis of life. 
When we analyze it by chemical methods, we find the chem- 
ical elements already described as present in organisms. 
You should not think of protoplasm as a simple compound 
but rather as a mixture of several compounds that are or- 
ganized to carry on the life processes. There is no chemical 
compound or mixture of chemical compounds that man 
has been able to put together that can be made to do just 
what the organized compounds in protoplasm have been 
doing ever since life began. 
Living organisms were known for a long time before either 
the cell or protoplasm was discovered. In earlier times 
there was no instrument by which one could see these 
minute bodies that each of you now can see by simply looking 
through the microscope. The identity of the inventor of the 
microscope is in dispute. Hooke and Grew in England, Mal- 
pighi in Italy, and Swammerdam and Leeuwenhoek, both in 
Holland, are the names especially associated with early micro- ENVIRONMENT 
47 
scopic observations. Leeuwenhoek became an expert lens 
grinder and made many different microscopes during his long 
lifetime. He possessed no less than 247 complete microscopes. 
From this very simple beginning in the seventeenth century, 
by men who liked to try experiments, we have developed the 
modern microscope. No single invention has contributed so 
much to our knowledge of the structure of organisms as the 
perfected microscope. 
45. Environment. - The life functions which we have 
been discussing are processes present in every form of life 
at its very beginning. \s soon as the apple tree's seed be- 
comes a small plant, this small plant has them and just as 
soon as the egg of the codi ng moth hatches into a larva the 
larva exhibits each of them These life functions, then, 
are passed from parent to offspring in the plant, in the animal, 
and in man. In marked contrast to these fixed factors of 
living protoplasm, there is a varying factor, the surroundings 
or environment in which organisms live. 
A certain environment is necessary for the manifestation 
and continuance of life. Land animals, like the dog, die 
when kept under water; fishes cannot survive in the air; 
plants perish from lack of moisture; and nearly every living 
thing requires moderate heat and light. 
Polar bears flourish in the extreme north, but would die 
in the Sahara Desert. Camels, on the other hand, can cross 
large stretches of desert without water, but would hardly 
survive a trip to the far north. Fish which are used to the 
pressure of the depths of the ocean burst wrhen brought to 
the surface. Cotton will not grow in the north, but given 
a proper environment, the climate and soil of the south, it 
becomes one of our best crops. Thus we see that the de- 
velopment of every organism is dependent upon its environ- 
ment. Man's superiority over the other animals is due in 
large measure to his greater ability to control his environ- 
ment. 48 
THE PHYSICAL BASIS OF LIFE 
OUTLINE 
The cell 
Wall 
Cytoplasm 
Nucleus 
Nucleoli 
Organs 
Tissues 
Protoplasm 
Environment 
Contrasted with Life Processes 
Illustrated 
SUMMARY 
The cell is the unit of both structure and function for all living things. 
It is composed of protoplasm which is surrounded by a ceil wall. This 
protoplasm is made up of cytoplasm and a nucleus, which in turn con- 
tains one or more nucleoli. All the tissues and organs of the body are 
made up of cells, which are the units of the life functions. These life 
functions are fixed, as distinguished from environment, which is variable. 
QUESTIONS 
Describe the cell. Of what is it the unit? Of what is it composed? 
What goes to make up organs and tissues ? Are the life processes fixed ? 
Is environment uniform? Illustrate your answer. 
REFERENCES 
Cockerell, Zoology, Chapters II, III, IV. 
Gager, Fundamentals of Botany, Chapter II. 
Sinnott, Botany, Principles and Problems, Chapter IX. 
Smallwood, Man - The Animal, Chapter III. 
Transeau, General Botany, Chapters III and IV. PART II 
APPLICATION OF BIOLOGIC PRINCIPLES TO ANIMAL LIFE 
CHAPTER VI 
THE GRASSHOPPER, AN INTRODUCTION TO THE 
STUDY OF INSECTS 
And the grasshopper shall be a burden. - Ecclesiastes, xii, 5. 
46. The Great Variety of Animal Life. - In the world 
there are about one million kinds of animals and more than 
one half of them are insects. These are so widely dis- 
tributed, have such a great variety of form and color, and 
are so numerous that the age in which man lives is some- 
times called the age of insects. While insects do not have 
any representatives that are large, compared with dogs or 
horses, they make up in number what they lack in size. 
It is not the lions, rattlesnakes, or other large enemies that 
compete most with man for the domination of the earth, 
but the hosts of small animals of which the insects form the 
largest class. The building of the Panama Canal was as 
much a triumph over the disease-carrying mosquito as it was 
an engineering feat. Even to-day, many parts of the earth 
are uninhabitable because of mosquitoes. 
The grasshopper, the potato beetle, the chinchbug, the 
scale insects, the codling moth, the gypsy moth, the army 
worm, and many others are taking a heavy toll each year 
from the world's food crops. The activities of these insects 
make food prices higher and it is in the interest of food con- 
49 50 
THE GRASSHOPPER 
servation that more people should be aware of the common 
facts about insects. To do this it is necessary to get an idea 
of how they grow, how they get their food, what they eat, 
where their eggs are laid, how they reproduce, and how they 
may be controlled. 
When we study rather closely the life history, structure, 
and activities of one insect, we have a fairly good idea of the 
great class of insects, for they are all much alike in many 
ways. All the fundamental life functions are performed by 
insects. All must have food, all must get oxygen, all have 
some way of self-protection, all reproduce, and all sooner 
or later die of accident, disease, or old age. Certain in- 
sects live as adults but a few hours, while elephants may 
live a hundred years or more. But all die in time and the 
young must come to take the places of the old if their par- 
ticular race is not to become extinct. 
Insects are always doing something. Some are flying 
from flower to flower, and you can watch to see what they 
are doing; others are busy on the leaves or the stems, and a 
few minutes of observation will show you whether they are 
friends or foes of the plant upon which you find them. The 
most interesting way to study insects is to watch them in 
their home life, but when this cannot be done, they can be 
well studied in the laboratory. Even in the city a sur- 
prisingly large number of kinds of insects can be collected 
by a class and brought alive to the laboratory. 
47. The Grasshopper. - The typical insect chosen to 
begin our study is the grasshopper. When during mid or late 
summer we walk into the fields or along paths lined with 
grass, we are often surprised at the number of grasshoppers 
which jump away as we approach. They are of various sizes 
and kinds. Some are small and without wings, while others 
have small but well-formed wings. The difference in the 
wings and in the shape of the body tells us that there are 
various kinds of grasshoppers. LIFE PROCESSES OF THE GRASSHOPPER 
51 
Figure 20. - Female Grasshopper. 
Notice the position and shape of the modified legs at the end of the 
abdomen. 
FIELD STUDY 
Study living insects. Collect insects, such as grasshoppers, crickets, 
beetles, bees, wasps, flies, moths, butterflies, etc. Place some under 
tumblers and complete your report as follows : 
Where Found 
0 
® * 
Number of 
Wings 
Size of 
Wings 
Size of 
Third Leg 
Mouth Parts 
Strong 
Weak 
Separate 
Fused 
House fly . 
On food in the home 
6 
2 
Small 
Grasshopper 
On grass in the field 
6 
4 
Medium 
Moth . . 
On flowers in the park 
6 
4 
Large 
48. Life Processes of the Grasshopper. - The young 
grasshopper must escape being eaten, must find food, must 
have oxygen to breathe, must be able to rid the body of waste 
substances, must be able to see, feel, and taste, must develop 
into an adult, and must do its part in providing for another 
generation of grasshoppers. If the grasshopper fails in any 
one of the first three of these it is unable to live, and conse- 52 
THE GRASSHOPPER 
quently the last and most important work, that of providing 
for the next generation, is not possible. 
LABORATORY STUDY 
Examine a live grasshopper. What are its means of locomotion? 
Compare its jump with its length. If in the same proportion, how far 
could a man six feet tall jump? How does the grasshopper obtain 
food? What protection from enemies does it gain from its color? 
Notice the division of the body into three regions: head, thorax (tho- 
r&ks), which has wings and legs, and abdomen (ab-do'm6n). How large 
is the head compared with the thorax and abdomen? The body is 
covered with a skin-like substance, known as chitin. This is called 
the skeleton of the grasshopper and because it is on the outside of the 
body it is termed an exoskeleton. How does it protect the grasshopper ? 
When the living grasshopper is held between the thumb and finger, it 
" spits molasses." This is the partially digested food from its crop. 
49. Protection. - When we look closely at the grass- 
hopper, we find that it is provided with many adaptations 
which prevent its being caught and eaten. The most im- 
portant of these are its color and markings. When a grass- 
hopper jumps into the grass and remains quiet, its color so 
closely resembles the grass and the sticks that many of its 
enemies overlook it. The grasshopper is further protected 
by a pair of large eyes and by simple ears, which are located 
on the side of the body. By means of these sense organs, it 
becomes aware of the presence of enemies. The quickness of 
grasshoppers in jumping also helps them to escape being 
eaten. 
50. Food-getting. - The grasshopper has little difficulty 
in finding its food. It eats leaves, and particularly the blades 
of grass. It does not need a keen sense of smell, as does the 
bee, which must search for flowers. However, the grass- 
hopper has special smelling organs located in its antennae 
(an-ten'e), those long feelers which grow out from the head 
like soft horns. 
The mouth parts which cut and chew the food consist 
of an upper lip and two teeth (mandibles, man'di-b'ls). The Thomas Henry Huxley (1825-1895) was the father of the 
modern method of studying biology. Up to 1850 information 
about plants and animals was imparted only by lectures. Hux- 
ley found that science of his day contained many errors due to 
lack of first-hand information on the part of the writers. He 
corrected many of these errors by personal study of plants and 
animals, and devoted years to developing methods of laboratory 
study which enabled the student to gain his information directly. 
To-day these methods are accepted wherever the subject of 
biology is studied. This great English biologist made many 
important discoveries and was awarded numerous honors by his 
countrymen. Huxley showed great skill in putting the conclu- 
sions of science into simple language. BODY REGIONS 
53 
teeth are moved by powerful muscles which nearly fill the 
head. These mandibles work from side to side, instead of 
up and down as our teeth do. They are so effective that 
sometimes when grasshoppers become numerous they strip the 
grass of all its leaves, and even destroy growing fields of grain. 
51. Respiration. - All animals have some way of getting 
oxygen to every portion of their bodies and of getting rid 
of carbon dioxide. The 
grasshopper has no lungs 
such as ours, nor does 
it breathe through its 
mouth. On either side 
of the abdomen are eight 
regularly arranged, small 
openings, spiracles (spirz- 
a-k'ls), which lead into 
branching tubes, tracheae 
(tra'ke-e). There are 
also two spiracles on 
the mesothorax. The 
branching tracheae are 
kept open by means of 
skeleton-like rings so that 
the pressure of the mus- 
cles and other organs cannot flatten or close them. The 
tracheae continue to branch until the subdivisions are so 
small that they can be seen only by aid of the microscope. 
These fine branches extend to the minute cells of which the 
body of the grasshopper is composed. Here the oxygen 
passes to the living protoplasm of the cells and carbon dioxide 
is given off to the air which is in these breathing tubes. This 
use of the oxygen by the protoplasm and the giving off of the 
carbon dioxide is respiration. (See Respiration, page 16.) 
52. Body Regions. - The grasshopper has three body 
regions: the head, the thorax, and the abdomen. Each 
Figure 21. - The Lips and Teeth of the 
Grasshopper. 
These show special adaptations which 
explain their peculiar shape and position. 
See if you can find out how each part is 
used when the grasshopper is eating. 54 
THE GRASSHOPPER 
of these regions is adapted to particular kinds of work. The 
head structures are adapted to food-getting, seeing, and feel- 
ing. The thorax has appendages for locomotion: walking, 
Metathorax 
Prothorax 
U%sothoraxj£\__ 
Head 
; .Eye 
t Antenna 
Abdomen 
Auditory sac 
.Ocellus 
-Mandible 
-Upper lip 
AMaxilla 
\\Lower lip 
Spiracles 
Spiracles 
Figure 22.-'Important Parts of the Grasshopper. 
There are eight spiracles in the abdomen and two on the thorax. 
jumping, and hying. Ihe abdomen is adapted to breathing, 
hearing, and reproduction. 
The Head. - On the front of the head are three simple 
eyes and on the sides of the head two compound eyes. Near 
the simple eyes are two antennae for feeling. The mouth 
has several special parts 
for food-getting. (See 
Figure 21, page 53.) 
These parts are an upper 
lip (labrum), and a lower 
lip (labium) for moving 
the food into the mouth. 
Inside the mouth is a pair 
of mandibles for cutting 
food and a pair of maxillae 
with palps for carrying the food. The hypopharynx, a sort 
of tongue, is useful in handling the food. 
The Thorax. - This is the second body region and it is 
composed of three parts. The prothorax, separate from the 
Ferfur. 
Tibia-j 
Trochahterlj 
Figure 23. - The Jumping Leg of the 
Grasshopper. 
Why is the femur in this leg so much 
larger than in the one just in front of it ? 
Tarsus BODY REGIONS 
55 
rest of the thorax, is provided with the first pair of legs. 
The mesothorax, provided with a second pair of legs and the 
first pair of wings, is not clearly separated from the third 
part of the thorax, the metathorax. This supports the 
jumping legs and the second pair of wings (the flying wings), 
which of all these appendages are the most serviceable. 
FORE-WING 
HIND-WING 
Figure 24. - Fore- and Hind-Wings of the Grasshopper. 
How does the grasshopper use each wing ? What becomes of the hind- 
wing when the grasshopper is not flying ? 
The Abdomen. - This third body region is clearly divided 
into ten segments. The first segment, a partial one, con- 
tains the two auditory sacs, and two abdominal spiracles, 
one on either side. Fourteen other spiracles are found on the 
next seven segments, seven spiracles on each side. The 
last two segments have no spiracles. Instead they are 
modified for reproduction. The spiracles are used for breath- 
ing and the auditory sac, possibly, for hearing. In the 56 
THE GRASSHOPPER 
female the last segment of the abdomen is provided with 
two pairs of blunt spines that serve as an egg-laying organ 
called ovipositor. 
LABORATORY STUDY 
Work out the divisions of the body of the grasshopper: head, thorax, 
and abdomen; the position of eyes. How are the antenna; related to 
the eyes? How many distinct mouth parts are there? The teeth or 
jaws are the most useful in getting food. How do the jaws work? 
Sketch the head to show these parts with the mouth open. 
Notice the attachment of the head to the thorax. The head fits into 
the thorax. The loose anterior (front) portion of the thorax is the pro- 
thorax (forward thorax). The first pair of legs is attached to it. 
Sketch the prothorax to show it and its legs. The portion of the thorax 
back of the prothorax is divided into two regions: the mesothorax 
(middle thorax) and the metathorax (back thorax). The line between 
them is not clear. Sketch these parts together with the legs and the 
wings. The jumping legs are attached to the metathorax; the outer 
wings to the mesothorax; the inner wings to the metathorax. The 
inner wings are used in flying. The leg of the grasshopper consists of: 
(1) a small section close to the body (the trochanter); a long muscular 
part free from spines (femur); a slender spiny part (tibia); and three 
segments of the foot (tarsus). The last segment of the foot is furnished 
with hooks which help the grasshopper in climbing, while the spines 
on the tibia prevent slipping as the grasshopper jumps. The large 
muscles in the femur of the last pair of legs, the spines on the tibia, and 
the hooks on the tarsus, are special adaptations which help the grass- 
hopper in various ways. 
Notice the tapering abdomen, composed of ten segments (rings), or 
parts of segments. Notice the depression and membrane in the first 
segment. This is the auditory organ, but it is not a true ear. Sketch 
the abdomen to show its features. The spiracles are located on the 
sides of the abdomen and thorax. 
53. Excretion. - The gaseous waste, carbon dioxide, 
passes from the body into the spiracles and escapes into the 
air. The liquid wastes are collected by tubes that open 
into the intestine. If the grasshopper could not get rid 
of the waste substances that form in the body, it would be 
unable to live. But it has organs of excretion which remove REPRODUCTION AND LIFE HISTORY 
57 
all these wastes from the body. If the grasshopper could 
use up entirely all the substances taken into the body, there 
would be little or no waste products. As the various nutri- 
tive substances become a part of the body of the grasshop- 
per, some of the energy which they contain is so combined 
that it cannot be used by the living cells of the insect. 
54. Nervous System. - The fundamental life process of 
irritability (sensation) in the grasshopper is performed by 
the nervous system. It consists of nerves and ganglia (a 
cluster of nerve cells) arranged in a row beneath the digestive 
canal and in the head. Nerves connect this central chain of 
ganglia, which are masses of nerve cells, with all parts of 
the body. On the head are found compound and simple 
eyes, special organs for feeling, the antennse, and organs of 
taste on the mouth parts. By means of all these specialized 
nervous organs, the grasshopper is able to see, feel, and 
taste with a high degree of efficiency. Through these 
senses and that of hearing, it is made aware of food and 
enemies. 
55. Reproduction and Life History. - In the autumn the 
female lays from 25 to 100 eggs in shallow holes which she 
makes in the ground. Some grasshoppers lay their eggs in 
decayed logs. The following spring the eggs hatch into 
small, wingless grasshoppers called nymphs (nimfs). (See 
Figure 25.) The nymph has a firm outer covering called an 
exoskeleton, which stretches but little with the growth of the 
nymph. Accordingly, at stated periods, the nymph sheds 
this exoskeleton, and grows until it fills its new exoskele- 
ton. This shedding or molting continues until the fifth and 
last molt, when the nymph becomes an adult provided with 
wings and mature in every sense. 
Adult grasshoppers may be found during the summer in 
meadows, flying and crawling and feeding on the leaves of 
grass, grain, and other crops. The adults mate and the 
females lay eggs to provide for the next generation, 58 
THE GRASSHOPPER 
56. Metamorphosis. - All animals which pass through a 
marked change in external appearance as they become full 
grown are said to undergo a metamorphosis (met-a-mdr'fo-sis : 
Greek, meta, change; morphe, form). These changes are 
more marked in such insects as the ants and bees than in the 
grasshopper. For this reason we speak of two forms of 
metamorphosis - complete and incomplete. 
57. Incomplete Metamorphosis. - The newly hatched 
grasshopper, while very small, looks enough like a wingless 
grasshopper to be identified as belonging to the grasshopper 
family. Its form does not change materially from the time 
Figure 25. - Incomplete Metamorphosis in the Grasshopper. 
it is hatched until it is full sized. Thus the grasshoppers 
become adult by a growing process termed incomplete meta- 
morphosis, showing no marked change in form (Figure 25). 
Complete metamorphosis will be discussed in connection 
with the butterfly or moth on page 94. 
58. Structure and Classification of the Grasshopper. - In 
order to understand the grasshopper more fully it is neces- 
sary to find its place in the classification of animals. All 
known animals have been grouped into classes for con- 
venience in study. The grasshopper belongs to the large 
class of animals called Insecta (in-sek'ta: Latin, in, in; 
sectum, cut). 
The insects, as a class, have their bodies divided into three 
regions - head, thorax, and abdomen. (See Figure 22.) 
All have three pairs of legs, and most of them two pairs of 
wings. They breathe by means of air tubes (trachece). In 
becoming adult, all pass through metamorphosis, either ECONOMIC PHASES OF THE GRASSHOPPER 
59 
complete or incomplete. The insect group is subdivided 
into fifteen smaller groups or orders. 
The grasshopper belongs to the order known as Orthop- 
tera (or-thbp'ter-a: Greek, orthos, straight: pteron, wing). 
In the Orthoptera we find three common families: grasshop- 
pers, crickets, katydids. 
With permission of Nature Magazine. 
Figure 26.-The Katydid. 
The males of this insect serenade at night by rubbing the edge of one of the 
fore-wings against a file on the other. This gives the familiar chirping noise. 
59. Economic Phases of the Grasshopper. - The grass- 
hopper eats the leaves of plants, and if there are many grass- 
hoppers they cause a serious loss of crops. The plague of 
locusts mentioned in the Bible refers to grasshoppers. In 60 
THE GRASSHOPPER 
some of the Western States years ago the grasshoppers came' 
in great swarms year after year and destroyed annually 
crops estimated to be worth $200,000,000. But ordinarily, 
owing to the activities of their natural enemies, the number 
of grasshoppers does not become alarming. 
Among the natural enemies of these insects that do much 
toward reducing their number are the birds. Some of the 
greatest destroyers of grasshoppers are the quail, bluebird, 
sparrow hawk, butcher bird, crow, red-winged blackbird, 
and kingbird. 
There are other closely related insects that are harmful, 
as the cockroaches, the nuisances of the pantry, and the 
crickets that eat the roots of plants. There are also tree 
crickets which frequently lay their eggs in raspberry canes, 
killing the cane above the place where the egg is laid. 
60. What Has an Animal Like the Grasshopper Accom- 
plished by Living? - (1) It has used plants as food to build 
a complex body. (2) It has produced more grasshoppers. 
(3) It has used some stored-up food which might have been 
useful to cattle or sheep. (4) It has set free waste carbon 
dioxide which can be used by green plants to assist them in 
making food. (5) When it dies and decomposes, its chemical 
substances are returned to the soil and air to be used again 
by other living things. 
OUTLINE 
Animal Life 
Large animals 
Insects 
Variety 
"Age of insects" 
Grasshopper 
Life processes 
Food-getting 
Respiration 
Excretion 
^engation 
Body regions 
Head 
Thorax 
Abdomen 
Metamorphosis 
Incomplete 
Classification 
Orthoptera 
Economic phases 
Accomplishment QUESTIONS 
61 
SUMMARY 
The vast variety of animal life makes advisable the study of types. 
For the insects, which are so numerous, we choose the grasshopper, 
which has life processes corresponding to those of other insects. The 
grasshopper has three body regions: head, thorax, and abdomen. 
Through these the life processes are carried out. 
The grasshopper undergoes incomplete metamorphosis. It belongs 
to the class of insecta and to the order Orthoptera. It is of great eco- 
nomic importance as a destroyer of crops. 
Which is the most numerous kind of animal ? Are the large animals 
or the insects more important to man? Why? What divisions has 
the body of the grasshopper? In what way is he protected from his 
enemies? How does he get food? How breathe? How reproduce? 
Describe his nervous system; his life history. What is metamor- 
phosis? What kind of metamorphosis does the grasshopper undergo? 
To what class and to what order of insects does the grasshopper belong? 
What is his economic importance ? 
QUESTIONS CHAPTER VII 
INSECTS IN GENERAL 
The careful insect midst his works I view, 
Now from the flowers exhaust the fragrant dew. 
- Gay 
We have just learned how the grasshopper lives. These 
facts about the life of this common insect are true about 
the lives of all other insects, for each one must have food, 
breathe, give off waste, and produce more insects. 
61. What Is an Insect? -We have seen that the grass- 
hopper is divided into head, thorax, and abdomen, has three 
pairs of legs, and air tubes for breathing. These same fea- 
tures are present in all insects. Most insects have two pairs 
of wings, but this is not true of flies or of some of the simpler 
forms which lack wings. While there are many differences 
in the size of these parts, the fact that an animal has this 
combination of structures defines it as an insect. 
The numerical superiority of insects is due in large meas- 
ure : (1) to their power of flight which helps them to 
escape from their enemies; (2) to their remarkable adapta- 
tions in color and habits which prevent them from being 
eaten, and enable them to live in every conceivable place 
and on every variety of food, some even eating tobacco and 
certain insecticides; and (3) to the production of large 
numbers of young, often several thousand in a single season. 
Because of their reproductive activity, even minute in- 
sects become more destructive than the largest animals that 
62 WHAT IS AN INSECT? 
63 
Figure 27.- Cotton Plant. 
Cotton cloth is made from the fibers which cover the seeds of the cotton 
plant. These are formed in the fruit, a kind of capsule known as a boll. 
The boll weevil, which is a beetle, is the worst insect enemy that has ever 
attacked the cotton plant. 64 
INSECTS IN GENERAL 
have ever lived. Insects eat the food that the plant has 
made which man needs, and a few of them are intimately 
associated with such destructive diseases as malaria, typhoid 
fever, and yellow fever. Thus they not only destroy the 
food and economic products of man but directly cause his 
death. However, the argument is not wholly against insects 
for some of them produce such useful products as honey and 
silk. Thus owing to their universal distribution over the 
surface of the earth, and their importance to man, whether 
for harm or good, we are said to be living in the Age of In- 
sects. 
62. Economic Insects. - Economic insects are those 
which, because of their activities, are either helpful or harmful 
to man. By saying that an insect has no economic impor- 
tance we mean that it does not harm us by eating things use- 
ful to us and that it does not help us in any way. 
The struggle to live is a problem for all animals, for man 
as well as for the grasshopper. All insects must eat, and 
some eat the same things we wish to eat. Such insects we 
call harmful. Others aid the plants by carrying the pollen 
dust from one flower to another; others make honey. 
Such insects are useful. Certain other insects, like the fly, 
carry the germs of disease. These insects are particularly 
harmful, for they cause sickness and death. 
Certain beetles eat dead flesh or bury dead animals by 
tunneling under them. Such insects are helpful. We 
should study insects in order to find out which are our friends 
and which our enemies. It would not do to kill all kinds 
of insects, for in many cases we should harm ourselves. 
63. Classification of Insects. - So far we have avoided 
the technical names for the different classes of insects. But 
a knowledge of these terms will help us to find out more 
about insects in various reference books. For this reason 
we are giving below the most recent classification of the 
different groups or orders, as they are called. These need CLASSIFICATION OF INSECTS 
65 
not be memorized, but they will be found convenient for 
reference. 
Order 
Pronunciation 
Derivation 
I 
Common 
Representatives 
Orthoptera 
or-thop'te-ra 
orthos, straight+ 
pteron, wing 
grasshoppers, 
katydids, 
crickets 
Hemiptera 
he-mip'te-rd 
hemi-, half + 
pteron, wing 
bugs 
Coleoptera 
kol-e-bp'te-ra 
coleos, sheath+ 
pteron, wing 
beetles 
Thysanura 
thl-sd-nu'rd 
thysanos, fringe + 
ura, tail 
fish-moths 
Blattoidea 
blat-to-i'de-d 
blatta-Vike, blatta 
an insect that shuns 
the light, a cock-- 
roach (Latin) 
cockroaches 
Siphunculata 
si-fun'cu-ld,-ta 
having a little tube 
(siphunculus, dimin- 
utive of sipho) 
sucking lice 
Hymenoptera 
hi-m^n-b p' te-ra 
hymen, membrane + 
pteron, wing 
ants, bees, 
wasps, saw-flies, 
gall-wasps 
Odonata 
o-dbn-a'ta 
toothed {odontos, 
of a tooth) 
dragon flies 
Ephemerida 
e-fem-er'i-du 
short-lived 
{ephemeras, daily) 
May flies 
Plecoptera 
plek-op'te-ra 
plectos, plaited + 
pteron, wing 
stone flies 
Trichoptera 
trik-bp'te-ra 
trichos, genitive of 
thrix, hair + 
pteron, wing 
caddis flies 
Lepidoptera 
ISp-i-dop'te-ra 
lepidos, genitive of 
lepis, scale + 
pteron, wing 
butterflies and 
moths 
Diptera 
dip'te-ra 
di-, twice + 
pteron, wing 
flies, mosquitoes 
Suctoria 
siik-to'ri-d 
sugere, suctus, to 
suck (Latin) 
fleas 
Homoptera 
ho-mop'te-rd 
homos, similar-|- 
pteron, wing 
cicadas, aphids, 
scale-insects 
In the preceding chapter we studied the grasshopper, a 
typical member of the Orthoptera. We shall now take up 66 
INSECTS IN GENERAL 
several other orders of insects, with most of which we are 
already familiar. 
64. Hemiptera. - One of the commonest orders of insects 
is the Hemiptera (he-mip'ter-a: Greek, hemi, half; pteron, 
wing). To this order belong such common insects as the 
cicadas, plant lice, the woolly aphis, and the bane of the 
These insects, commonly called locusts, were abundant in the early sum- 
mer of 1919 in the Eastern and Middle Western States. Did you see any 
of them ? If you did not, you will have to wait seventeen years before you 
have another chance. There may be other breeds in the vicinity. 
Figure 28. - Adult Seventeen-year Cicada and Nymph. 
orchard, the San Jose (san h<5-sa') scale. Some of these are 
very harmful. When the San Jose scale is allowed to feed 
freely, whole orchards may be destroyed. Plant lice injure 
apple, cherry, and peach trees, and the cabbage plant. The 
several kinds of scale insects which harm orchards may be 
killed by spraying the trees with a solution of lime and 
sulphur. The Hemiptera include the true bugs. BEETLES 
67 
65. Cicada. - The seventeen-year cicada (si-ka'da), com- 
monly called the "seventeen-year locust," is one of the most 
interesting insects of the Hemiptera. The name is given 
to it because the nymphs (nim'fs), the immature stage, 
remain in the ground, actively feeding on roots, for seven- 
teen years. There is another kind of cicada that remains 
in the ground for thirteen years. It lives in the Southern 
States. 
Every thirteen or seventeen years, generally in the month 
of May, the nymphs crawl out of the ground, climb trees 
or fences, and molt into adult cicadas. The adult females 
lay their eggs in tender shoots of trees, causing the shoots to 
die. The young cicadas, after hatching in the shoot of the 
tree, go into the ground and begin their long period of larval 
existence which lasts thirteen or seventeen years. These 
cicadas are usually found in limited areas, but in these areas 
are very numerous. 
The cicadas which we hear every summer are another kind, 
whose nymph lives in the ground for two years. As there 
are two broods of this species that appear in alternate years, 
the number does not seem to vary from year to year. Birds 
do much towards destroying them, the kingbird, sparrow- 
hawk, butcher bird, and great-crested flycatcher being their 
most common enemies. 
66. Beetles. - These are hard-winged insects (Coleop- 
tera) and generally noisy fliers. The first pair of wings is 
homy and meets in a straight line down the back. The 
second pair of wings consists of thin membranes. The 
mouth parts are for biting. Among the harmful beetles are 
many wood borers, the May beetles, potato beetles, as- 
paragus beetles, and weevils. Some of the beneficial beetles 
are the ladybug, which feeds on destructive and harmful 
insects, and the carrion beetle, that feeds on dead animals. 
The ladybugs are decidedly beneficial. Their larvae run 
over leaves and feed on other insects. Even as adults they 68 
INSECTS IN GENERAL 
continue this good work. Hop growers appreciate the 
value of both the larvae and the ladybugs on their vines, as 
the ladybugs destroy the harmful hop lice. 
The bird enemies of the beetle are numerous. Among the 
most important are the ring-necked pheasant recently intro- 
duced, the rose-breasted grosbeak, and the quail, which 
feed particularly on potato beetles. The English sparrow, 
cuckoo, and kingbird feed on the weevils. Robins, black- 
With permission of Nature Magazine. 
Figure 29.- Beetles. 
birds, and crows eat the white grubs, the larval stage of the 
May beetles. The woodpeckers destroy great numbers of 
borers by digging holes in the trees where the borers are 
tunneling. 
67. Potato " Bug " or Potato Beetle. - Originally the beetle 
was found in Colorado feeding on wild plants of the potato 
family, whence its name of Colorado beetle. It gradually 
made its way east from one potato patch to another, being 
helped by the wild plants of the potato family that grew LIFE HISTORY OF THE POTATO BEETLE 
69 
where there were no potatoes. These beetles were also 
carried by trains that in a few hours took them hundreds 
of miles. They arrived in New York State in 1872. 
68. Damage. - The potato beetle feeds on the foliage of 
the potato plant, thus injuring the size and quality of the 
tubers. This is due to 
the fact that most of the 
starch stored in the tuber 
is produced in the leaves 
and when the leaves are 
destroyed the amount of 
starch available for the 
tuber is lessened. Spray- 
ing must be carried on 
wherever potatoes are 
grown, to insure a good 
crop. 
69. Life History of the 
Potato Beetle. - The 
adult potato beetle 
passes the winter in the 
ground. In the spring 
the adults crawl out of 
the ground and the fe- 
males lay their orange- 
colored eggs on the under 
side of the leaves of the 
early potatoes. In about 
a week or ten days the 
eggs hatch and the larvae eat ravenously. In two or three 
weeks the larvae reach their full size. They make their way 
into the ground, where they pupate for two weeks or longer, 
depending on the temperature. At the end of the resting 
stage, they emerge as adults and the females lay their eggs 
on the late potatoes for a second generation. The eggs hatch 
Figure 30. - This Beetle is the Fastest 
Flying Animal Known. 70 
INSECTS IN GENERAL 
into larvae, the larvae pupate in the ground, and the adults 
emerge in the fall. At the beginning of the cold weather 
the adults enter the ground and hibernate through the 
winter. 
70. Natural Enemies. - Fortunately the potato beetle 
has many natural enemies. Adult lady beetles, popularly 
called " ladybugs," and their larvae kill many of them. The 
tachina-flies lay eggs on 
the potato beetle larvae 
and the young tachina- 
flies in the form of larvae 
burrow into the bodies of 
the beetle larvae, killing 
them in great numbers. 
Toads and snakes are 
enemies of the potato 
beetle and they take a 
heavy toll of them. The 
skunk is another enemy 
of the potato beetle, while 
crows, rose-breasted gros- 
beaks, pheasants, and 
quail destroy them in 
great numbers. 
71. The Codling Moth. - Probably the most destructive 
of the Lepidoptera is the codling moth already mentioned 
in the first chapter. The larvae spend the winter in the 
cocoon, pupate in the spring, and emerge as adults at about 
the time early apple trees bloom. The eggs are laid on the 
young apples about the time the petals of the blossoms fall 
and the larvae begin to eat the growing apples, causing 
many of them to drop to the ground, or in any event, in- 
juring the quality of the apple. 
In one year the injury done by the codling moth to the 
apple and pear industry in New York State alone amounted 
Figure 31. - Eggs of Ladybug (greatly- 
enlarged). 
You will need sharp eyes to find them 
in nature. TENT CATERPILLARS 
71 
to $3,000,000. By applying a spray containing some poison 
just after the petals have fallen, the codling moths may be 
destroyed. The spray should not be used while the blossoms 
are fresh because then the helpful bees which visit them are 
killed and no harm is done to the destructive codling moths 
that come later. 
72. Clothes Moths. - These are small moths with pointed 
and fringed wings. The adults emerge from May to August. 
They take no food and, after depositing their eggs on woolen 
material, soon die. It takes three weeks for the transfor- 
mation of the pupa into the adult. More than one genera- 
tion a season may arise. 
The white, naked larva is about a half inch long and feeds 
on furs, feathers, hair, woolen materials, and museum speci- 
mens. The extensive destructiveness of these larvae has 
resulted in many remedies. A full discussion of these will 
be found in Farmers' Bulletin No. 1353. A few of the 
more important are the following: (1) Constant watchful- 
ness, for no treatment that kills the larva already in fabrics 
will have any lasting effects in keeping other clothes moths 
from depositing their eggs if the material is left exposed; 
(2) thorough brushing and beating if possible and placing 
the clothes in the sun before any treatment is applied; 
(3) careful wrapping in unbroken paper; (4) naphthalene 
and camphor for use in tight chests and trunks; (5) car- 
bon disulphid. This chemical is excellent for the fumiga- 
tion of closets which can be tightly sealed, and for trunks, 
chests, and other tight containers. When gaseous it is in- 
flammable. 
73. Tent Caterpillars. - There are several different kinds 
of caterpillars that spin webs in the trees in the spring and 
early summer. These are known as the tent caterpillars 
(Figure 32). The larvae grow to maturity in about a 
month and during this' time they feed on the leaves of the 
trees. 72 
INSECTS IN GENERAL 
The details connected with the place and time of pupation 
vary with each kind of tent caterpillar. Some of them pass 
the winter in the pupa stage while others hatch in the spring 
from the fall batch of 
eggs. 
Here are found the 
apple-tree tent caterpil- 
lars and several kinds of 
tussock moths. The lat- 
ter are very destructive 
to the leaves of shade 
trees. 
74. Silkworms. - The 
silkworms belong to the 
same general group of 
spinning moths as the 
tent caterpillars. The 
larvae feed preferably on 
mulberry leaves, although 
they will eat the leaves 
of the osage orange. 
The larvae feed for 
about a month before 
spinning their cocoons. 
The material for the co- 
coon is manufactured in 
the silk glands which 
open just beneath the 
mouth. It takes three or 
four days for the larva to 
make its cocoon, which 
is constructed of a smooth thread usually more than one 
thousand feet long. In a week or two pupation ends and 
the adult escapes from its silken home by moistening the 
cement that holds the silk threads on one end of the cocoon. 
They are seen resting during the hotter 
part of the day on the trunk of the apple 
tree. Later in the day they go out and 
eat the foliage. Note the great blankets 
of silk that they have spun on the side of 
the tree. Fortunately most of these cater- 
pillars were attacked by ichneumon-flies, 
tachina flies, and chalcis-flies so that very 
few matured. The year following these 
destructive insect pests did very little 
damage owing to the successful campaign 
of their numerous insect enemies. 
Figure 32. - Tent Caterpillars. SILKWORMS 
73 
This insect is most valuable to man. It usually takes about 
three thousand cocoons to make a pound of raw silk and 
about ninety cocoon fibers are required to make a thread of 
sewing silk. Twenty-five to fifty thousand cocoons are 
used in securing enough material for a silk dress. 
The silk-raising industry requires the detailed under- 
standing of the habits of this domesticated insect. The 
cocoons from which the silken threads are secured are baked 
or steamed two or three days after the larvae have completed 
them. This process 
kills the pupa, for co- 
coons from which the 
adults have escaped are 
unsatisfactory for the 
manufacture of silk. 
Three thousand six 
hundred years ago the 
wife of the third Em- 
peror of China dis- 
covered the value of 
the silkworm. The 
method of making silk 
was a Chinese secret 
for two thousand years. 
About 555 a.d. two 
monks were induced by the Roman Emperor Justinian to 
bring the silkworm eggs out of China. This they did by 
concealing the eggs in cavities in their staffs. After this 
date the silkworm industry spread rapidly throughout Europe. 
Figure 33. - Wingless Female of Tussock 
Moth. 
She is laying eggs on the cocoon from 
which she has just crawled. After the eggs 
are laid she moves around for a time and 
soon dies of starvation, if some bird does not 
eat her in the meantime. 
FIELD, LABORATORY, OR HOME STUDY OF MOTHS 
AND CATERPILLARS 
These insects are easily collected and are interesting to study. From 
late in the spring until October you can find larvae and pupae. Some 
of the leaves upon which the larvae are feeding should be collected. 74 
INSECTS IN GENERAL 
The larvae should be placed in jars provided with moist soil and some 
leaves. Arrange the cocoons and pupae which you find as suggested 
in the following table. 
Cocoon 
Pupa 
Spun with Spun with Spun with 
silk only a leaf hair 
Without Suspended Suspended Parasit- 
cocoon from one end from one loop ized 
Tent caterpillars spin cocoons and form small brown moths. Celery 
"worms" hang in a loop and form a black, swallowtail butterfly which 
feeds on the nectar of lilacs and the rhododendrons of city parks. 
The black spiny caterpillars of the willows and elms hang free from 
the knot of silk and form the mourning cloak butterfly. 
Tomato "worms" burrow into the ground and form a large-bodied, 
small-winged moth, a sphinx moth. 
75. Lice. - Lice are small, wingless insects which were 
formerly classed with the true bugs. The mouth parts are 
adapted for piercing and sucking while in the bird lice there 
are nipper-like mandibles for biting instead of sucking. 
The bird lice feed only on the hairs and feathers and not 
on the blood as do the head and body lice. The feet of lice 
are armed with a very large curved claw which enables them 
to cling to the animal on which they feed, which is called 
their host. 
The head louse of man deposits the eggs, which number 
about sixty, on the hairs of the head. These eggs usually 
hatch in six days. The head lice, notwithstanding the 
progress of civilization, are the most important of the ex- 
ternal human parasites. They are commonly found in 
logging camps, jails, ships, in fact, wherever there is close 
association with people who are dirty. This was conspic- 
uously true in the recent war. LICE 
75 
The body louse is a different kind of insect from the head 
louse. It lives on the clothing and deposits its eggs on the 
clothing. 
The eggs of lice are oval, whitish objects, commonly called 
" nits." The eggs of the body louse are glued to the 
fibers of the cloth and number about two hundred. They 
hatch in about six days. When the young hatch, they 
are like the parent, for there is no metamorphosis as in 
butterflies and moths. It has been conclusively proved 
that the body louse is 
an important carrier of 
the germs . of typhus 
fever, relapsing fever, 
and trench fever. It 
is possible that as fleas 
move from one rodent1 
to another they may 
carry the germs of the 
dreaded bubonic plague, 
if their host harbors 
these germs. 
Prevention consists 
largely in cleanliness, but this will not prevent temporary 
lousiness if there is association with unclean and careless 
companions. Lice are spread by contact such as the general 
use of combs and brushes or borrowed hats and caps. Body 
lice are scattered from person to person through the clothes 
and bed linen. 
Head lice can best be destroyed by a thorough washing 
of the head with a two per cent carbolic acid solution or 
equal parts of kerosene and olive oil. When one of these 
remedies has been thoroughly rubbed into the hair it should 
remain for several hours, then be washed with warm water 
Figure 34. - Male and Female Cooties. 
These vermin greatly annoyed the sol- 
diers in the trenches and are carriers of 
disease. (Much larger than in life.) 
1 Rodents are gnawing animals such as rats, mice, ground squirrels and 
so on. 76 
INSECTS IN GENERAL 
and soap. The dead lice and nits must be removed with a 
fine-tooth comb. Repeat this treatment after ten days to 
kill those that may have hatched in the meantime. Body 
lice are killed by sterilizing the clothing by such methods 
as baking, steaming, or fumigating. 
76. An Immigrant Pest. - The European corn borer was 
introduced into the United States in 1909 and 1910 in broom 
corn imported from Hungary and Italy. This insect is a 
member of the moth family and is injurious in the cater- 
pillar stage. Since its introduction it has spread over more 
than 7,696 square miles, and has been found in one hundred 
and eighty-five species of plants in the United States. In 
addition to corn, this pest is destructive of beans, beets, 
cotton, dahlias, hops, potatoes, sunflowers, swiss chard, and 
many other of the food plants of man and animals. 
The European corn borer spends the winter in the tunnel 
made in the plant upon which it has been feeding. In April 
or May the borer, which is a caterpillar, spins a cocoon in 
the tunnel and in about nineteen days develops into the 
adult moth. After mating, the female deposits her eggs in 
small masses, each egg overlapping the adjoining egg in the 
manner of shingles. The females deposit about 350 eggs, 
on an average, but some lay more than a thousand. These 
eggs hatch in about seven days. The young borer soon 
begins to eat its way into the inside of the plant and within 
fifty days has again grown into an adult. Thus a second 
brood is ready to be hatched. 
The females of this later generation lay more eggs, usually 
about 450 which are frequently deposited on or near the 
forming ears of corn. These eggs hatch in seven days and 
the borers begin their destructive feeding. The caterpillars 
of this second generation are the ones that pass the winter 
in the tunnels of the corn or other plant on which they have 
been feeding. 
The name corn borer is given to the larva of several differ- AN IMMIGRANT PEST 
77 
ent kinds of insects that burrow into the stalks and ears of 
com as well as in flowering plants and weeds. Among these 
should be mentioned the corn-ear worm, the stalk borer, 
smartweed borer, celery-stalk worm, and larger corn-stalk 
borer. All of these have habits similar to the European 
With permission of Nature Magazine. 
Figure 35. - Larv/e of Destructive Insects. 
They are exposed by cutting open the bundle of roots. This is one of the 
ways that insect pests are introduced in the United States. 
borer and the larvae are so similar that they cannot be dis- 
tinguished, except by experts. 
The seriousness of the destruction caused by the European 
corn borer has led the United States Department of Agricul- 
ture to place strict regulation on the importation from for- 
eign territory of plants likely to contain this insect. 78 
INSECTS IN GENERAL 
Control Measures. - Up to the present it has been found extremely 
difficult to control the spread of this pest. The following is taken 
from the Report of the New York State Entomologist, 1921: 
It is advisable to emphasize the fact that special attention should be 
given to early planted corn because this is the most likely to be se- 
riously infested and it appears probable that a very considerable re- 
duction in the numbers of pests may be secured in single-brooded areas 
at least by concentrating effort upon the early corn. 
1. Cut corn close to the ground, since many of the borers winter 
in the stubble. 
2. Put as much of the corn into silos as possible because the borers 
are killed by the fermentation of the ensilage. This also applies to 
waste from canning factories. 
3. Cut or shred corn stalks fed to cattle in order to promote their 
consumption. In any event keep the uneaten parts, the "orts," out 
of the manure and provide for the destruction by May 15 of the borers 
contained in all such materials whether in field, lot, or barn, by burn- 
ing, plowing under, or submerging in water for some 40 days, unless 
the stalks are worked into piles containing considerable horse manure 
which will heat to such an extent as to destroy the borers. 
4. Fall plowing, especially early and thorough, destroys many 
borers. It is considered advisable to encourage the practice in the 
infested areas. Heavy rolling prior to plowing has been suggested as a 
valuable aid, because many borers are killed by crushing the butts 
and it is then easier to turn the stubble under. 
5. Weeds and other plants growing in or near badly infested corn 
may be invaded by borers in late August or September; consequently 
clean culture is of service in reducing the number of stems in which 
the pests may winter. Burning over in late fall or early spring of waste 
or weedy areas in or adjacent to corn fields, especially badly infested 
ones, is advised. 
6. Corn stalks, cobs, and almost any thick part of all herbaceous 
plants may contain these borers under certain conditions and their 
shipment or removal from the infested area is dangerous and in many 
cases a violation of quarantine regulations. 
7. Crops particularly likely to carry the borer, such as celery, beets, 
dahlias, etc., should not be grown in the infested areas within 50 feet of 
corn because the borers, deserting the corn for one reason or another, 
may crawl 30 feet or more before entering some other plant. 
8. Where conditions permit, the probabilities of a general and pos- 
sibly serious infestation may be considerably reduced by planting small 
areas of early corn, particularly near previously infested fields or ad- GENERAL METHODS OF CONTROLLING INSECTS 
79 
jacent to sources of infestation, such as scattered corn stalks, for the 
purpose of attracting the moths. In case a serious infestation results, 
the borers in these small plantings may be destroyed by feeding the 
corn, or in some other manner. The main crop, if planted a little 
later, would largely escape the pest, if one may judge from conditions 
the last three seasons in the infested areas in both New York State and 
Ontario, Canada. 
77. General Methods of Controlling Insects. - The 
details just given for the control of the European corn borer 
indicate that in this book, we can deal only with general 
measures for the control of insect pests. To simplify the 
consideration of the various methods they are discussed 
under (a) environmental factors, (b) poisoning, and (c) natural 
enemies. 
(a) Environmental Factors. - Before any definite plan can 
be formulated for getting rid of insects, it is necessary first 
to understand their habits in detail. Insects that live in 
the ground and feed on the roots cannot be killed by the 
same method as those that feed on wheat and other cereals; 
and, in turn, those that feed on the leaves of fruit trees re- 
quire a different treatment from those that live in the fruit. 
It is also important that one understand thoroughly the 
influence of the environmental factors and their importance 
in the growth and number of insects. It is necessary only 
to mention such environmental factors as temperature 
changes, rainfall, winds, food supply, natural enemies, 
parasites, and preventive measures to realize that each of 
these plays an important part. 
One preventive measure employed in controlling the num- 
ber of insects consists in changing the crops so that insects 
that feed on corn, for example, will not be able to get suit- 
able food if clover is sown after the corn crop. The expert 
farmer gives careful study to the proper rotation of crops 
in an effort to prevent the destructive insects from gaining too 
great headway. 80 
INSECTS IN GENERAL 
(b) Poisoning. - Such measures as the above are ap- 
plicable only to insects that live in the soil. Artificial 
methods must be used for the insects that live on and in 
plants. These consist in the application of poisons, the 
use of repellent substances, traps, and high and low tem- 
perature. The various insect poisons are known as in- 
secticides. A good insecticide must be one that is effective, 
cheap, and a harmless poison to the insect host. The follow- 
ing poisons are most important in killing the biting insects: 
Paris green, arsenate of lead, arsenate of lime, hellebore. 
For sucking insects lime-sulphur wash, whale-oil soap, kero- 
sene emulsion, tobacco decoction, and carbolic acid emul- 
sion are used as contact insecticides. 
Poisonous gases are used also in the control of insects. 
Here are employed carbon bisulphide, hydrocyanic acid 
gas, sulphur dioxide, tobacco. 
A number of substances are known to act as " repellents " 
to insects and are frequently used to great advantage in pre- 
venting insect attack. Among such substances are: Bor- 
deaux mixture, tobacco dust, carbolic acid emulsion, kero- 
sene, turpentine, coal tar. 
The common tangle foot, and various traps are successful 
in capturing flies. 
Cold storage is very successful in preventing insects from 
developing, especially in fruit. Flour and meal are protected 
by raising the temperature sufficiently to kill the eggs or in- 
sects that may have gained access to them. 
(c) Natural Enemies. - The natural enemies of insects 
are the birds and insects that prey upon them and the in- 
sects that live as parasites in them. 
Through the investigations of the United States Depart- 
ment of Agriculture, a certain kind of ladybug (Novius) was 
found in Australia, which is the natural enemy of an insect 
pest {cottony cushion scale) that was destroying the orange 
trees grown in California. This scale is a plant insect which GENERAL METHODS OF CONTROLLING INSECTS 
81 
was imported into the United States on young trees. Being 
freed from their natural enemies (Novius) which were not 
imported, they had increased rapidly. The prompt im- 
portation of novius put an end to the increase of the cottony 
cushion scale which is now of no great importance to Cali- 
fornia orange growers. 
Entomologists throughout the world are working in the 
war against insects. Parasites which prey upon and damage 
insects and keep their 
numbers down in one 
country are constantly 
being drafted by scien- 
tists for use in the fight 
against the imported 
pests of another country. 
Many of the insects 
which have found their 
way into this country 
from other lands, left 
their natural enemies 
behind them. In conse- 
quence, they have been 
able to increase in great 
numbers, resulting in ex- 
tensive damage to the 
plants and animals that 
they infest. In order to 
restore the balance of 
nature, the entomologist studies the life and habits of these 
insects in their own homes. He discovers what parasites 
prey on them. These are then collected and introduced into 
this country . 
The United States now has an expert in Mexico in search 
of parasites of the Mexican bean beetle and the Mexican 
fruit fly. Two experts are in Japan seeking the parasites 
Figure 36. - Cedar Waxwing. 
Feeding its young a flying insect. One 
of our most beneficial birds. 82 
INSECTS IN GENERAL 
of the Japanese beetle and the gypsy moth. Others have 
been in Hungary, India, and France. The experts of all 
these countries are also studying insect pests, and they 
place their information in books, scientific papers, and gov- 
ernment bulletins so that all the world may take advantage 
of their discoveries. This practice of publishing scientific 
information on these subjects is a great help in combating 
insect pests. 
78. House-flies and Mosquitoes. - This group (Diptera) 
includes also the bot-fly, stable-fly, and cheese-skipper; also 
the beneficial bee-fly, wasp-fly, and tachina-fly. 
Figure 37. - Eggs and Larvae of Mosquito (Culex). 
Center, egg-mass and larvae. Left top, enlarged eggs. Right, enlarged 
larva. 
One of the most important members of this group is the 
common mosquito, which lays from two hundred to four 
hundred eggs in a raft-like cluster on the surface of the water 
in any stagnant pool or rainwater barrel. These eggs are 
usually laid early in the morning and, in favorable weather, 
hatch within twenty-four hours. The wigglers (larvae) HOUSE-FLIES AND MOSQUITOES 
83 
keep to the surface when breathing but swim freely in the 
water for food. Food is brought to the mouth by vibrating 
cilia, which keep a cur- 
rent of water passing 
near them. From this 
water the wiggler col- 
lects his food. After 
seven days of this life 
it becomes a pupa, 
which, unlike most 
other pupae, can move 
about. The pupae re- 
main at the surface of 
the water for air but 
descend by swimming 
when disturbed. The pupa stage lasts for two days, when 
the adult emerges and flies away after its wings are dried. 
The time of these changes from egg to larva, from larva 
to pupa, and from pupa to adult depends on the temperature. 
Warm weather shortens the time and cold weather lengthens it. 
In the United States there are three distinct kinds of mos- 
quitoes. (1) The common mosquito is 
known by the technical name of Culex 
(ku'leks). It is not known that the 
Culex carries in its body any disease 
germs harmful to men, therefore it is 
regarded as harmless, although a source 
of great annoyance to those who fre- 
quent the woods or seashore during the 
summer. (2) Anopheles (a-nbf'e-lez) is 
the scientific name of a second kind of 
mosquito, which is also generally dis- 
tributed, but is not so numerous as the 
Culex. The Anopheles often carries in its body the germs 
that cause the disease called malaria. (3) Aedes, formerly 
Figure 38. - Larva of Culex in Breath- 
ing Position. 
Figure 39.- Pupa of 
Culex. 84 
INSECTS IN GENERAL 
known as Stegomyia (steg-o-mi'ya) is a mosquito common in 
the southern part of the United States. It is the insect 
which carries the germs of yellow fever from one person to 
another. 
It is fortunate that the mosquitoes have so many enemies. 
The " wigglers " are preyed upon by the larvae of dragon 
flies, by small fish, and by water beetles; while the adults 
are eaten by nighthawks, martins, bats, and dragon flies. 
Figure 40. - Positions of Culex (left) and Anopheles (right), when 
at rest on a vertical surface. 
Certain diseases caused by plants attack the adults and kill 
them in great numbers. (See Chapter XXIII.) 
The number of mosquitoes can be greatly reduced by 
destroying their natural breeding places in old rain barrels, 
watering troughs, boxes that may hold water, pails, eaves- 
troughs, and sink holes. The larger breeding places are 
sluggish streams and swamps. Draining these is the most 
effective method of preventing mosquitoes from laying their 
eggs in such localities. When this is not possible, the surface 
of the water may be covered with kerosene, which kills HOUSE-FLIES AND MOSQUITOES 
85 
With"permission of Nature Magazine. 
Figure 41. - The Dragon-fly. 
One of the insects that feed on adult mosquitoes. 86 
INSECTS IN GENERAL 
the larvae by preventing them from getting oxygen from 
the air. Frequent applications of oil greatly reduce the 
number of mosquitoes. 
79. The House-fly. - Because of its filthy habits of 
breeding and living and because it comes to the dining room 
and kitchen crawling over food, the house-fly has come to 
be recognized as a dangerous disease carrier. 
Life History. - Each female lays from one hundred to 
one hundred and sixty eggs in stable filth or other refuse. 
The eggs hatch in a day or so into legless larvae. In five to 
seven days, depending on the temperature and the food 
supply, the larvae are full grown. 
They then pupate for another five to 
seven days. At the end of this time 
the adults emerge as mature flies ready 
to lay eggs for another generation. 
This continues until cold weather puts 
an end to their activities. Enough 
generations are produced every year 
so that a single female in the spring 
could have a million descendants by 
October if numerous enemies did not 
make this impossible. 
Methods of Control. - Every one should support the "swat 
the fly " campaign and help reduce the number of flies. 
The few house-flies that survive the winter are responsible 
for the millions that swarm about in the summer. Their 
numbers may be reduced by several methods : 
1. Begin early to kill the flies that are seen. 
2. Remove all manure piles and make a general cleaning 
up of all refuse, thus destroying their breeding places. 
3. Put fly traps on the covers of garbage cans to entrap 
all those that hatch as well as adults that go in to feed. 
4. Keep many fly traps in operation in or about the house 
during the time of year that flies are active. 
Figure 42. - The Com- 
mon House-fly. PARASITIC FLIES 
87 
5. Poison those that do come in the house and keep 
fly paper ready for them at all times. 
80. Tachina-fly. - This fly is beneficial to man. While 
it resembles the house-fly in appearance it has differences 
that may be clearly seen. It has long bristles on the abdo- 
men and the bristles of the antennae are bare. The tachina- 
fly lays its eggs on such larvae as tent caterpillars, army 
worms, and many other destructive caterpillars. After these 
eggs are hatched the tachina larvae bore into the bodies of 
the army worms or tent caterpillars and there feed until 
they consume them. Many kinds of caterpillars are held 
in check by the activities of these tachina-flies. 
81. Parasitism. - If a plant or an animal feeds on a 
living plant or animal, it is an example of parasitism. In the 
above, the tachina-fly is the parasite and the tent caterpillar 
is the host. The animal on which the parasite feeds is called 
the host. If it feeds on the outside of an animal, like the 
mosquito, it is called an external parasite. If it feeds on 
the inside of an animal, as in the case of the tachina-fly 
larva, it is called an internal parasite. Lice and fleas are 
external parasites. In some cases parasitism is helpful 
to man, as in the case of the tachina-fly; in other cases, it 
works harm to man, as in the case of the anopheles mosquito. 
82. Parasitic Flies. - This group of insects is decidedly 
beneficial. As an illustration we may use one of the larger 
ones known as Thalessa or the ichneumon fly (Figure 43). 
With long, thread-like drills this parasitic insect bores holes 
in trees and lays an egg at the bottom of the hole. The 
egg is usually laid near the burrow of one of the larger 
tree borers, Tremex (Figure 44). 
The larva of the Thalessa makes its way along the burrow 
of the Tremex borer and fastens itself to the body of the 
borer, upon which it feeds. In time the adult Thalessa 
emerges, ready to lay eggs which will destroy more of these 
enemies of the tree. But if the Thalessa parasites kill the 88 
INSECTS IN GENERAL 
Tremex borer before it has eaten its way through the hard 
wood, all die together, because the Thalessa cannot cut 
an opening for itself. 
83. The Work of the National Government in Insect 
Control. - During the past forty years Dr. L. O. Howard 
has been either assistant director or director of the Bureau 
of Entomology, United States Department of Agriculture. 
He and his numerous 
associates have been 
making discoveries about 
insects and applying to 
human welfare not only 
the new things that they 
have been learning about 
insects, but the new dis- 
coveries made all over 
the world. 
We may gain some 
idea of the amount and 
kind of work done in this 
Bureau by simply read- 
ing over the following 
subjects, each of which 
receives special study. 
Work on the gypsy moth 
and brown-tail moth; 
deciduous-fruit insect investigations ; southern-field-crop in- 
sect investigations; investigations of the insects affecting the 
health of man; insects affecting the health of domestic ani- 
mals ; cereal and forage insect investigations ; investigations 
of insects affecting forest and shade trees, forest products, and 
hardy shrubs; investigations of insects injurious to vege- 
tables and truck crops; stored-product investigations; in- 
sects affecting tropical and subtropical fruits; bee-culture 
investigations. 
Figure 43. - Thalessa Laying Eggs. 
The tree is infested with Tremex. Dr. L. 0. Howard was born at Rockford, Illinois, 1857, and is 
still living. The year following his graduation from college, he 
became assistant entomologist in the Department of Agriculture 
at Washington. He remained in this official position until 1894, 
at which time he was made chief of the Bureau of Entomology. 
This position he still holds. He prepared definitions in entomology 
for the Century and Standard dictionaries. He is the author of 
Mosquitoes - How They Live; The Insect Book; The House-Fly; 
and many government publications. For many years he acted 
as the permanent secretary for the American Association for the 
Advancement of Science, the largest body of scientific workers 
in America. 
Dr. Howard has devoted his main energies for the past forty 
years to applying the technical discoveries in entomology to 
human welfare. PROTECTIVE RESEMBLANCE AMONG INSECTS 
89 
The extent to which man can control the multitude of 
insect pests and utilize the beneficial insects is an important 
factor in human progress. 
84. Insect Control in New York State. - The New York 
State entomological work is conducted as a part of the New 
York State Museum. There is a specially trained man in 
charge of the Department of Insects who is known as the 
State Entomologist, having his 
headquarters at Albany. 
It is his duty to keep as com- 
plete a record as possible of 
the insects in New York State. 
Annual reports are issued describ- 
ing in detail each year's work, 
for the nature of the work va- 
ries from year to year. 
In a recent report the follow- 
ing insects are studied in detail: 
European com borer, other com 
insects, small-grain pests, insects 
affecting other field crops, the 
codling moth, shade-tree insects, 
and forest insects. 
85. Protective Resemblance 
among Insects. - Every one who 
has tried to catch grasshoppers 
appreciates how difficult it is to 
see them when they are not in 
motion. The colors of the wings and upper part of the 
body blend with the grass on which they feed. These colors 
are said to protect the grasshopper and the expression pro- 
tective coloration or protective resemblance is used to describe 
this condition. 
Butterflies and moths show protective resemblance (Fig- 
ure 45) especially in those forms that have the upper sur- 
Figure 44.-Tremex. 
Just after laying eggs in a tree. 
The larvae of this insect do much 
damage to trees. 90 
INSECTS IN GENERAL 
face of the wings colored similarly to the trunks of trees on 
which these insects rest. Such dull colors are effective in 
obscuring them. The contrast in color is striking in all 
of these if we compare the brilliant colors seen on the hind 
wings when the insect is flying. 
The exact interpretation of the meaning of the colors 
in insects is partly theoretical, and so we find authorities 
differing over the use and value of color. An insect whose 
Figure 45. - A Moth (Catocala) Showing Protective Coloration. 
colors enable it to hide and lie in wait, making it more 
successful in catching its prey, is said to exhibit aggressive 
coloration. 
In contrast to this form of coloration, we find insects that 
are believed to be unpleasant to taste and have bright colors 
on their bodies to warn the animals that prey on them that 
they are unsuitable as food. The conspicuous bands of 
color on wasps are said to warn animals that these insects 
have a dangerous sting. Such insects show warning col- 
oration. HOME PROJECTS 
91 
These conspicuously colored insects often have imita- 
tors but those insects in turn are not unpleasant to taste 
nor do they have a dangerous sting. This is known as 
mimicry. 
HOME PROJECTS 
How Insects Pass the Winter. All forms of life must 
adapt themselves to the winter season. If they are unable 
to do this, they perish. 
Insects have adapted themselves in such a way that they 
pass the winter in some form or other. Certain insects live 
over the winter in the egg stage, as in the case of the tent 
caterpillar. Others like the Isabella caterpillar pass the 
winter as a larva. The cicada passes the winter deep in 
the ground as the nymph, while the cecropia moth is safe 
in a cocoon as a pupa. The mourning cloak butterfly is 
hanging in some protected place, in a barn or shed. The 
monarch butterfly has migrated to the southern states and 
thus escapes our severe winter weather. 
How many other examples, such as we have illustrated 
above can you find? Favorable places for these various 
groups are old board piles and lumber piles, old buildings, 
fence rows, hedges, and vine tangles. Bring into class all 
cocoons, egg masses, chrysalids, spider cases, larvse, and in 
fact anything that may prove to be alive in the insect line. 
Individual members of the class may select one of the 
following problems to be studied and written up. 
1. What do you find in searching the leaves of hollow 
stumps and logs in the woods ? 
2. What do you find in searching the lilac trees and 
tangles ? 
3. What do you find in searching the hedgerows and 
vines that climb on buildings ? 
4. What do you find in searching lumber piles and 
board piles? 92 
INSECTS IN GENERAL 
5. What do you find in searching old buildings, bams, 
sheds, and other protected spots ? 
6. Make a terrarium for confining all the specimens 
that are brought in but keep it outside on the window 
ledge. 
7. Sketch a landscape, roughly, which will show the 
area you covered and on it locate the position of the forms 
you found. 
8. Identify and classify with the aid of insect books, 
government and state college reports. 
OUTLINE 
Insects 
Defined 
Economic 
Classification 
Hemiptera 
Cicada 
17-year 
13-year 
2-year 
Coleoptera 
Beetles 
Potato bug 
Damage 
Life history 
Enemies 
Lepidoptera 
Codling moth 
Damage 
Clothes moth 
Remedies 
Tent caterpillar 
Tussock moth 
Silk worm 
History 
Economic importance 
Lice 
Head 
Body 
"Cooties" 
Corn borer 
History 
Economic importance 
Control measures 
General methods of control 
Environmental factors 
Poisoning 
Natural enemies 
Mosquitoes 
Culex 
Anopheles 
Aedes (Stegomyia) 
House-flies 
Life history 
Methods of control 
Tachina-fly 
Parasites 
Thalessa 
Tremex 
Insect Control 
National 
State 
Protective resemblance 
Coloration QUESTIONS 
93 
SUMMARY 
The number and variety of insects is so great that this is called the 
Age of Insects. Many that destroy our food-products are harmful, 
but some, like the bee, are helpful. Scientists have made an elaborate 
classification of insects, but the orders we are most interested in are the 
Hemiptera (locusts), Coleoptera (beetles), Lepidoptera (moths and but- 
terflies), Suctoria (lice and fleas), Orthoptera (grasshoppers), and Hy- 
menoptera (bees and ants). 
The potato bug, codling moth, tent caterpillar, and corn borer are 
among the insects which do the most damage. It is hard to estimate 
the loss caused to our food-products each year by these insects. The 
clothes moth ruins thousands of dollars' worth of clothing and furs each 
year. Lice and fleas are an annoying pest. On the other hand silk 
worms furnish us with valuable clothing. Mosquitoes and house-flies 
are common carriers of disease. The tachina-fly and certain parasitic 
flies are beneficial to man. Many insects escape their enemies because 
of their protective coloration. 
There are many ways of controlling insects. The Federal and State 
governments spend huge sums each year in this work. Rotation of 
crops helps to keep the pests from increasing. There are also many 
poisons, spread usually by spraying. Birds are natural enemies of 
insects. 
QUESTIONS 
What is an insect? Are insects helpful or harmful to man? Illus- 
trate your answer. What is meant by economic insects? What are 
some of the best known orders of insects? Name some common rep- 
resentatives under each. What insects do our food most harm ? Our 
clothes? Are mosquitoes and flies dangerous or merely annoying? 
What are cooties? Name two kinds of lice. What methods have the 
Federal and State governments adopted to control the spread of insect 
pests ? 
Crary, Field Zoology, Chapter X. 
Fabre, The Life of the Fly. 
Fabre, The Life of the Caterpillar. 
Hewitt, House-fly. 
Hodge, Nature Study and Life, Chapter XV. 
Howard, House-fly; Disease Carriers. 
Kellogg, Animals and Man, Chapter XV. 
Ross, The Reduction of Domestic Mosquitoes. 
Smith, Our Insect Friends and Enemies. 
REFERENCES CHAPTER VIII 
MOTHS AND BEES 
The white moth to the closing vine, 
The bee to the open clover, 
And the gypsy blood to the gypsy blood, 
Ever the wide world over. 
- Kipling 
86. Moths and Butterflies. - There are more harmful 
insects among the moths and butterflies than in any other 
group. In the preceding chapter we studied some of them, the 
codling moth, clothes moth, tent caterpillar, and corn borer. 
But there are also many others, including tussock moths, 
gypsy moths, brown-tail moths, cut-worms, canker worms, 
and cotton-boll worms. 
Butterflies are among the commonest and most attractive 
of insects. Many develop from larvae that do no particular 
harm, and many of them, like the bees, help in pollination. 
As the butterfly goes from flower to flower, its head brushes 
against the pollen, which is thus distributed, making it 
possible for flowers to grow seeds. Among the more strik- 
ingly colored butterflies are the black swallow-tail, the 
larvae of which feed on celery, parsley, and carrots; and 
the milkweed or monarch butterfly. 
87. Life History of the Monarch Butterfly - Complete 
Metamorphosis. - The monarch butterflies arrive in the 
Northern States from the South, usually in June. Very 
soon the females lay eggs on the different kinds of milkweeds. 
The eggs hatch in a few days - the time depending on the 
temperature - into caterpillars that feed on the leaves of 
94 LIFE HISTORY OF THE MONARCH BUTTERFLY 
95 
With permission of Nature Magazine. 
Figure 46. - Monarch Butterfly Showing Successive Stages in Its 
Metamorphosis. 96 
MOTHS AND BEES 
the milkweeds. Each caterpillar has three pairs of jointed 
legs near the head and five pairs of leg-like structures along 
the posterior region that serve for clinging. The caterpillar 
(larva) molts and each time grows larger but does not show 
any signs of wings like the grasshopper. It is merely a 
larger caterpillar. 
Just before the fourth molt it attaches itself to a leaf or 
stem and hangs by a knot of silk with its head down for a 
few days until it molts for the fourth time. After this molt 
it is a pupa without legs or mouth parts. It is yellowish 
green in color, with golden spots. During this stage there is 
a striking change taking place inside the green covering. 
Wings, new legs, different mouth parts with a long-coiled 
tongue, and a nervous system of a different form are growing 
into working order while this pupa hangs so quietly. After a 
few days the green pupa case breaks open and the adult 
crawls out with the wings crumpled. Within a few hours the 
wings expand and smooth out their wrinkles, and the moth is 
ready to fly away to feed on the nectar of flowers. This de- 
velopment is called complete metamorphosis. 
Complete metamorphosis may be defined as the series of 
changes through which the insect passes from egg into 
caterpillar, then into pupa, and finally into full-grown moth. 
Ants, bees, butterflies, beetles, and certain other insects 
undergo a complete metamorphosis. 
LABORATORY STUDY 
The adult monarch butterfly has the body divided into head, thorax, 
and abdomen. How do these parts compare in size with the same 
regions in the grasshopper? Compare the legs and wings with those 
of the grasshopper. Which of these two insects is better adapted to 
flying? To jumping? Draw the entire animal. Draw wings and 
legs. 
Gently rub the finger on the wing, and as the dust comes off, the 
wing looks more like the wing of a fly or bee. The lines that run length- 
wise of the wing are the veins. Draw the wing. ENEMIES OF THE MOTHS AND BUTTERFLIES 
97 
Observe the mouth parts of the caterpillar to see how they are adapted 
to obtaining food. Notice the antennae or feelers and the upper and 
lower lips. Compare these with the corresponding parts of the grass- 
hopper. 
The mouth parts of the butterfly are united into a single long tube 
which is the coiled tongue-like structure, called the proboscis (pro-bbs'Is). 
Unroll it and see how its length compares with the length of the body. 
The butterfly uses the pro- 
boscis to suck nectar from 
flowers. Compare these 
mouth parts with those of 
the grasshopper. 
88. Enemies of the 
Moths and Butterflies. 
- Butterflies would be- 
come a scourge were it 
not for their numerous 
enemies. Chief among 
these enemies are the 
parasitic flies (§80), the 
females of which lay their 
eggs on the bodies of 
many kinds of caterpil- 
lars. When these eggs 
hatch into small larvae, 
they burrow their way 
into the body of the large 
caterpillar, feeding upon 
the juices and tissue of 
their host. These larvae are called parasitic because they get 
their living directly from another animal. 
The parasitic fly larvae grow rapidly and before the cater- 
pillar dies they reach the stage at which they turn into pupae. 
When they are ready to pupate, they eat their way out of the 
body of the caterpillar and spin a cocoon which in some 
cases remains attached to the body of the caterpillar (Figure 
Figure 47. - Young Tobacco Worm, a 
Caterpillar. 
One of its insect enemies has laid eggs 
in its body, which have hatched into cater- 
pillars. These caterpillars, in turn, have 
fed upon the tobacco worm until it was 
time for them to pupate. They then ate 
their way out of the body of their host and 
spun their cocoons, which are attached to 
the surface of the body. What will hap- 
pen to the tobacco worm? 98 
MOTHS AND BEES 
47). These parasitic larvae so weaken the caterpillar that it 
dies. 
Other enemies of insects are the birds. Many birds live 
entirely upon caterpillars and we find birds that seek them 
as food in all stages of their development and growth. The 
eggs laid on the twigs and trunks of trees are eaten by chick- 
adees, nuthatches, brown creepers, and woodpeckers. The 
larvae are eaten by many birds, notably by cuckoos, blue- 
birds, wrens, blackbirds, orioles, blue jays, crows, and house 
sparrows. The cocoons and pupae are sought by the chicka- 
dees, woodpeckers, nuthatches, and brown creepers. The 
adult insects are preyed upon by house sparrows, chipping 
sparrows, and the whole group of flycatchers, including the 
kingbirds and phoebes. 
89. Bees. - In contrast to the moths and butterflies 
which are probably the most destructive order, we find the 
Figure 48. - Honey-bees (twice natural size). 
a, worker; b, queen ; c, drone. 
bees, which are the insects of greatest value to man. The 
honey-bee and the bumblebee are economically the most 
important of the group. The honey-bee is valuable for its 
honey and wax and as a distributor of the pollen (Figure 48) 
which is necessary to produce seed. The bumblebee is val- 
uable mainly as a distributor of pollen. BEES 
99 
Honey-bees afford a splendid example of community 
life among insects. In the wild state they live in trees and 
caves. All wild honey-bees in this coun- 
try have escaped from hives. In a honey- 
bee colony there are three classes of bees 
- the perfect females or queens, the 
males or drones, and the imperfect fe- 
males or workers (Figure 48). There are 
generally one queen, a few hundred 
drones, and twenty to fifty thousand 
workers. 
In a normal colony the queen alone 
lays eggs. She can lay an unfertilized 
egg which hatches into a drone or she 
can lay an egg which is fertilized. This 
fertilized egg hatches into a queen or 
worker, according to the food and the 
size of the cell which are provided by 
the workers. Thus the decision as to whether the young 
bee shall be a queen or a worker rests with the workers 
themselves. They also have the 
power to supersede the queen, or 
to raise a new queen in case of 
the sudden death of the old one. 
These powers are rightly intrusted 
to the workers - the great ma- 
jority. 
The eggs are placed by the queen 
in cells (Figure 49), and after 
hatching are fed by the young 
workers, called nurses. The larva 
(Figure 50) is fairly bathed in 
food. In a few days it is full 
grown and then pupates. The 
workers now cap over the cell with 
Figure 49. - Three 
Queen Cells. 
In the brood comb of 
the honey-bee. 
Figure 50.-a, Honey-bee Egg ; 
b, Young Larva; c, Old 
Larva ; d, Pupa. 100 
MOTHS AND BEES 
wax, and in about twenty- 
one days the young bee 
cuts away the cap and 
crawls out-an adult pro- 
vided with the four wings, 
mouth parts, antennae, and 
the six legs of the honey- 
bee (Figures 51 and 52). 
Workers are provided 
with the sting which is a 
weapon of both defense 
and offense (Figure 53). 
The queen has a small 
sting and the drones have 
none. When bees sting 
large animals like men, 
horses, and dogs, their 
sting is pulled out and 
with it parts of the internal organs, thus causing the death 
of the bee. When bees sting other insects or even one 
another the sting is not 
lost. 
Sometimes swarms 
which have few bees and 
little honey are attacked 
by bees from other colo- 
nies. It is a pitched bat- 
tle until the " robber 
bees " are beaten back or 
the defenders are them- 
selves killed. The sting 
is used in these battles. 
Bees are instinctively 
sanitary. If a large bum- 
blebee enters the hive, the 
Femur 
Coxa 
Tibia , 
Tarsus 
/ 
roehanter 
Wax I 
pincers^ 
Figure 51. - Inner Surface of Left 
Hind Leg of Worker. 
A. 
Femur 
Coxa 
\ 
xTibia 
Pollen 
by basket 
M/^ax 
pincers 
.Tarsus 
Trochanter 
Figure 52. - Outer Surface of Left 
Hind Leg of Worker. BEES 
101 
bees kill the intruder and usually, finding him too large to be 
taken out, embalm him by injecting the sting repeatedly 
into his body. The result of this operation is to make the 
bumblebee harmless to the 
colony. Sometimes they 
cover the body of a small, 
dead animal with a case 
made of propolis (prbp'o- 
lis), a substance the bees 
gather from certain buds. 
This serves to protect the 
colony from the effects of 
the decomposition of the 
body. 
At irregular intervals 
during the early spring 
and summer, bees have the 
peculiar habit of swarming 
(Figures 54 and 55). Sev- 
eral reasons for swarming 
are given by bee-keepers 
but no one pretends to be 
certain that he really 
knows the cause. It is a 
sort of revolt of the bees 
against their condition. 
Two of the commonest 
reasons given to explain 
swarming are the lack of 
room for the growing col- 
ony and lack of food. 
When bees swarm, they usually alight on the limb of a 
tree and form a dense cluster. Here they hang from fifteen 
minutes to an hour before leaving for the woods. In a few 
cases bees have remained in this " cluster " state overnight, 
It is provided with barbs and a small 
amount of formic acid as an adaptative 
feature. Being located at the end of the 
abdomen, it can be turned in any direc- 
tion. Notice the barbs on the sting. 
These point backwards and are adapted 
to cling to the surfaces through which it 
is forced. 
Figure 53. - The Bee's Sting. 102 
MOTHS AND BEES 
but usually they are lost unless they are collected inside of 
three hours. The swarm consists of a large number of 
adult bees, workers, and drones, and usually a single queen. 
With permission of Nature Magazine. 
Figure 54. - Honey-bees Clustering at Swarming Time. 
Various devices against swarming have been invented 
but the most effective is to clip the wings of the queen in 
order that she may be kept at home because the other bees 
usually follow her. This is done after the queen has taken BEES 
103 
her weddmg-night. Her wings are clipped close to the 
body. The bees that then swarm soon come back and are 
easily controlled. While the bees are still in the air, a clean, 
empty hive is placed where the old one was. Bee-keepers, 
during the swarming period, always have a number of empty 
hives in position ready 
for the swarm to occupy. 
The returning bees en- 
ter the new hive in 
search of the queen. As 
they are rushing in, the 
queen with clipped wings 
is released and she, in 
turn, joins the proces- 
sion and enters with the 
others. Having found 
the queen and plenty of 
room, the colony is usu- 
ally content to remain. 
Sometimes swarming be- 
comes a mania with cer- 
tain colonies and it is 
difficult to get them to 
settle down contentedly 
in a hive and make honey. 
Runaway swarms have 
to be watched with great 
patience. Bees that 
have been raised for many 
bee generations in man-made hives (Figure 56) sometimes 
leave suddenly and seek out a hollow tree in the forests. 
The length of the bee's life varies. The drones are usually 
killed at the end of their first season. Queens live for five 
or six or even ten years. Workers live three or four weeks 
in the working season and several months in the fall or winter. 
Figure 55. - Capturing a Swarm. 104 
MOTHS AND BEES 
The honey and wax produced annually in the United States 
are valued at $25,000,000. 
90. Adaptation Shown in the Honey-bee. - The honey- 
bee offers a fine example of adaptation. The tongue is 
adapted to getting nectar from certain flowers like apple 
blossoms, lindens, white clover, and sweet clover. It is too 
short to get nectar from red clover blossoms. The mandibles 
Figure 56.---Model Apiary. 
are adapted to gathering propolis from buds, also for knead- 
ing the wax and for polishing surfaces. The wings are 
adaptations for the particular life of the honey-bee. In the 
first place they are small, and are not likely to be injured 
when the bees are packed closely together as in swarm clus- 
ters. Then, to compensate for the small size, they are 
vibrated with great rapidity to carry the bees through the 
air with a load of nectar and pollen. Sometimes they vibrate 
440 times per second. INTERESTING BEHAVIOR 
105 
The rear pair of legs is adapted not to jumping, as in a 
grasshopper, but for carrying loads of pollen and propolis. 
These legs are flat and thin and 
provided with bristles to keep the 
load from sliding off. 
91. Ants. - Many interesting 
facts about the honey-bees are 
well known, but less attention 
has been paid to the ants, al- 
though these seem to be even 
more wonderful insects. 
They live in large families with 
many workers, and a number of 
queens and males. Some have, 
in addition, soldiers with strong 
mouth parts (mandibles) to do 
the fighting for the colony. 
92. Interesting Behavior. - 
Ants act more like human beings 
than perhaps any other animal. 
Here are some of the things 
they do. 
1. They build beaten roads with tunnels under brushpiles. 
2. They keep plant lice for the sweet fluid they exude 
which suggests the keeping of 
cattle by man. 
3. They carry these plant lice 
into their tunnels and care for 
them over the winter season. In 
the spring they carry them out 
and place them on food plants. 
4. If a nest is attacked by 
enemies, the soldiers rush around 
and stroke the workers with their antennae. This seems to 
inform them of the attack and they hurry to the rescue. 
Sidej of 
"Tongue 
Labial 
palps 
"-Tongue 
Figure 57. - Tongue of 
Honey-bee. 
Notice the numerous hairs of 
the tongue and palps. 
Figure 58. - Worker Honey-bee 
Laden with Pollen. 106 
MOTHS AND BEES 
5. They wrestle and play and sometimes carry one another 
around. It looks like a football game. 
6. They have battles with other colonies. Before a 
battle starts they send out scouts. They await the return of 
the scouts before they begin the battle. 
7. When one colony subdues another in battle, the victors 
take home the larvae and pupa? of the vanquished and bring 
them up to be slaves. The slaves seem to be loyal to their 
conquerors and to take great interest in the welfare of the 
victorious colony. 
8. Among certain kinds of ants the slaveholders harce 
depended so long on the slaves that they are unable to build 
nests or even feed themselves. If the slaves are taken away, 
the slaveholders starve. The slaveholders are able to fight, 
however, to get more slaves. 
93. Life History of the Ant. - In most ant colonies there 
are several queens. Unlike the honey-bees, several queens 
live in harmony in an ant colony. The ant eggs are so small 
that they are scarcely visible to the unaided eye. The leg- 
less larvae hatch in a few days, being full grown in about 
two weeks. Pupation lasts about two weeks. The cocoons 
are the white objects which are commonly called 11 ant-eggs." 
The adults guard these cocoons which contain the pupae, 
carrying them away to places of safety when the colony is 
disturbed. Sometimes the adult workers remove them to 
warmer quarters. 
The males and females have wings while the workers are 
wingless. 
OUTLINE 
Moths and butterflies 
Monarch butterfly 
Life history 
Complete metamorphosis 
Enemies 
Parasites 
Birds 
Bees 
The Colony 
Workers QUESTIONS 
107 
Queen 
Eggs 
Development 
Swarming 
Adaptations 
Ants 
Interesting behavior 
Eight habits like men 
Life history 
SUMMARY 
Among the commonest and most interesting insects are monarch 
butterflies, bees, and ants. The life history of the monarch butterfly 
gives us a good illustration of complete metamorphosis. The chief 
enemies of this moth as of most insects are parasites and the birds which 
prey upon them. 
Of all insects the bees are among the most valuable to man. They 
live in colonies under the command of a queen who alone lays the 
eggs from which new bees are hatched. Fertilized eggs can result in 
queens or workers according to the food the workers give it. When 
a colony becomes crowded bees usually swarm. They are remarkably 
well adapted for making honey. 
Ants are more like people in their behavior than any other insects. 
They build roads, keep other insects for food, have soldiers and slaves, 
make war on each other, and sometimes even seem to play games. 
QUESTIONS 
What are some of the most harmful moths? Some of the most 
beautiful? Describe the life history of the monarch butterfly. What 
does it illustrate? What are two of the chief enemies of moths? 
What three kinds of honey-bees are there? How does each come into 
being? Give the life history of a bee from egg to fully developed 
worker. Why do bees swarm? How is a swarm handled by the bee- 
keeper? What adaptations has the bee? In what different ways do 
ants act like human beings? Do they have queens? Workers? 
Describe the life history of the ant. 
REFERENCES 
Langstroth, Hive and Honey Bee. 
Lutz, Fieldbook of Insects. 
Mitchell, Mosquito Life. 
Osborne, Economic Zoology, Chapter XII. 
Phillips, Bee Keeping. 
Root, A. B. C. and X. Y. Z. of Bee Culture. CHAPTER IX 
THE CRAB FAMILY AND HOW THEY LIVE 
You cannot make a crab walk straight. 
- Aristophanes 
94. Crustaceans.-The Crustaceans (krus-ta shuns : Latin, 
crusta, crust) are so called because of their hard outer 
covering. This family is 
closely related to the in- 
sects. The similarity is 
most easily seen in the 
external skeleton and the 
several hinge-joints in the 
legs which they have 
in common with insects. 
Crabs, lobsters, and 
shrimps are among the 
most familiar crustaceans. 
The body consists of a 
limited number of seg- 
ments, each of which usu- 
ally bears a pair of jointed 
appendages. The appen- 
dages are variously modi- 
fied ; some aid in swim- 
ming, others in securing 
food, and others are used 
in walking. On the walk- 
ing legs are located most of the gills that aid in respiration. 
The others are on the thorax. 
Figure 59. - Crayfish, Showing Eggs 
108 BODY 
109 
The jointed appendage is the distinctive characteristic of 
the group to which crabs and lobsters belong. For this 
reason this group is given the technical name Arthropoda 
(ar-throp'o-da: Greek, arthron, joint; pod, root of pous, 
foot). 
95. Crayfish. - Those who live inland can study the 
common crayfish or " crab " as a typical crustacean, while 
those who are near the 
seashore can observe the 
lobster. They are so 
similar that a description 
of either one will serve to 
indicate the chief char- 
acteristics of both. 
96. Body. - The body 
is covered with a hard 
outside skeleton called an 
exoskeleton (from ex, out). 
In animals like frogs or 
fishes the skeleton is with- 
in the body and the flesh 
is on the outside, so it is 
customary to refer to such 
a skeleton as an endoskele- 
ton (from endo, inside). 
The lime which com- 
poses the skeleton is fur- 
nished by the food the crayfish eats. As this substance is nec- 
essary to its growth, we find the crayfish living only in streams 
where lime may be secured. The exoskeleton is mainly for 
the protection of the crayfish against the animals that eat it. 
The color in the shell also helps to protect it because this 
color usually resembles that of its natural surroundings. 
The crayfish is divided into two regions, the head-thorax 
region and the abdomen. The segments of the abdomen are 
Figure 60. - Moulted Exoskeleton of 
Lobster. 
One can tell just what kind of an ani- 
mal this is simply by studying this cast- 
off shell. 110 
THE CRAB FAMILY AND HOW THEY LIVE 
clearly defined, but those of the head-thorax, technically 
termed the cephalothorax, are so fused that they can be made 
out only with difficulty. 
Molting. - An interesting feature in the study of the 
crayfish is the shedding of the external skeleton. As it is 
covered by a firm exoskeleton it must get rid of this occa- 
sionally, in order to grow. Molting, in the case of the cray- 
fish, is a serious and dangerous operation, as it is followed 
Sternal Artery.. 
Ovary. Abdominal Artery 
Circum-esophayeal y//e 
^dssares^ gostrum 
Intestine 
Train 
Bladder 
-..Green Gland 
'..Mouth 
Cardiac Stomach 
Pyloric Stomaci 
Duct 
Plao/Muscles\ 
, Oviduct 
PosteriorVe/dral'Artery 
. AnieriorVenlmlArtery 
Hepato pancreas 
..Telson 
Figure 61. -Body of Crayfish. 
by a period during which the crayfish is without means of 
offense or defense. The crayfish usually hides until a new 
exoskeleton is partially formed. In the molting process the 
covering of the eyes and part of the lining of the digestive 
tract, as well as the whole exoskeleton, are shed. The cray- 
fish molts every year of its life and several times during the 
first year (Figure 60). 
The last abdominal segment and the appendages next 
to the last are broad and form a tail fin (uropod). 
97. Appendages. - The crayfish has nineteen pairs of ap- 
pendages located on the lower or ventral surface of the body. 
They are used for swimming, walking, protection, capturing 
prey, crushing food, and as special sense organs. APPENDAGES 
111 
The swimming appendages on the abdomen are very 
simple, two-parted feet, known as swimmerets (Figure 62). 
The last appendage on the abdomen is much enlarged, with 
each part greatly flattened. (See uropod in Figure 62.) 
This flattened foot is an adaptation Jhat helps the crayfish 
in swimming back- 
wards. 
On the thorax re- 
gion, the feet have 
changed into large, 
many-jointed struc- 
tures that are strong 
enough to support 
the body in walking. 
(See walking leg, 
Figure 62.) The 
first walking leg is 
much larger than 
any of the others 
and terminates in a 
strong pincer (chela, 
Figure 62). The 
chela is used in fight- 
ing, in defense, and 
in capturing food. 
On the basal joints 
of these walking legs are found gills that absorb oxygen from 
the water. 
Just in front of the walking legs are located six pairs of 
appendages that assist in bringing food to the mouth after 
it has been crushed and tom to pieces. There are three 
pairs of maxillipeds, two pairs of maxillae, and one pair of 
mandibles (Figure 62). 
The mandible is short and hard and has a broad surface 
on the end. When the two mandibles come together, their 
Figure 62. - Appendages of Crayfish. 112 
THE CRAB FAMILY AND HOW THEY LIVE 
action is mainly to crush food but this broad surface is also 
rough so that they have a grinding action. 
The two pairs of appendages just back of the mandible 
are very thin, almost leaf-like, and covered with sensory 
hairs. These hairs are supplied with nerves and are classified 
as taste and touch hairs. The second maxilla supports a 
special fold, scoop-shaped, which extends into the gill cham- 
ber. Its function is to help in respiratory movements by 
keeping the water circulating in the gill chamber. The water 
is drawn in from the back edge of the gill chamber and 
passes out near the mouth. We may show this by placing a 
few drops of red ink at the back edge of the gill chamber of a 
live crayfish, being sure to have the water cover its back. 
The three remaining pairs (maxillipeds, Figure 62) are 
similar to the abdominal appendages with the parts marked 
" en " and " ex " much enlarged. 
The crayfish has two pairs of antennae that are used for 
feeling and possibly tasting. Special students of the sense 
organs in the crayfish and similar animals doubt very much 
if the word " taste " is the best one to use in describing the 
responses which a crayfish gives when a drop of meat juice 
is placed in the water near the mouth parts or an antenna 
and the crayfish begins to move the mouth parts as it does 
when eating. 
In the basal joint of the small antennae is located a sac 
which is covered with a plate. The edge of this plate is 
furnished with hairs. The sac communicates with the water. 
It is the " ear " of the crayfish but is more correctly termed 
the " balancing organ." The crayfish does not hear with 
this organ but is unable to swim naturally when the " ears " 
are removed. 
In Figure 62 the parts of the appendages are marked " en " 
and " ex " to indicate just which one becomes enlarged or 
reduced in comparison with the other. There is no better 
illustration in zoology of the extent of adaption in the same NECESSITY OF ALL LIFE PROCESSES 
113 
structure than that shown in this study of the appendages 
of the crayfish. 
It seems very strange to include the eye of the crayfish 
in the list of appendages. Some scientists insist that it is a 
very much reduced appendage while others reject this in- 
terpretation. This is the reason that the number of append- 
ages is sometimes given as twenty. 
The eye is on the end of a movable stalk. It is compound 
because it consists of more than 2,500 distinct parts. It is 
hardly correct to say that the compound eyes represent 
2,500 simple eyes fused into one but so far as the action of 
each is concerned this might be said. For each one " sees " 
only the object directly in front of it. Thus the crayfish does 
not have a continuous complete picture of an object as we 
do but rather numerous partial and incomplete views that 
resemble a mosaic floor. Such vision is hence termed mosaic 
vision. 
LABORATORY STUDY ON THE APPENDAGES 
Examine more fully than in the above and report the work of each 
pair of appendages. Compare one of the abdominal appendages with 
those used in walking and feeling. What is the work of the large pin- 
cers? How many fin-like appendages are found in the mouth region? 
Notice that one of the mouth appendages has a flat part that extends 
in front of the gills. This part of the appendage is called the gill scoop 
or bailer. Describe how the appendages show at least three useful 
adaptations in the life of the crayfish. 
98. Necessity of All Life Processes. - As in the case of 
the grasshopper and other insects we have studied, the life 
processes of the crayfish are interesting enough to be taken 
up in some detail. 
Food and Food-getting. - The crayfish feeds on plants 
and animals, living and dead. One of the simple water 
plants, Chara (ka'ra), furnishes the crayfish with lime for its 
skeletons. Shells of snails and their own shed skins also 
help to supply lime. Crayfish seize food with their pincers 114 
THE CRAB FAMILY AND HOW THEY LIVE 
and move it towards the mouth. Small food particles are 
also carried towards the mouth by currents of water pro- 
duced by the mouth parts and the abdominal appendages. 
Particles of food are torn loose by the teeth or mandibles. 
Digestive System. -The mouth of the crayfish is just back of 
the mandibles, and connects with the stomach by a short esoph- 
agus. The stomach is divided into front and back parts. 
The front part possesses a grinding structure known as the 
Figure 63. - Organs of Crayfish. 
Note that the gills are outside of the body. In the posterior part of the 
abdomen, the muscles have been removed to show the nerve ganglia which 
extend the entire length of the body. 
gastric mill, which serves to shred and crush the food and 
make it ready for digestion in the back part. The liver, 
or digestive gland, pours a fluid into the stomach, which 
prepares the food for absorption by the walls of the stom- 
ach and intestine. The intestine begins at the back end 
of the stomach and extends to the last segment. 
Respiration. - Crayfish obtain oxygen from the water 
by means of gills which are well covered by the overhanging LIFE HISTORY 
115 
skeleton of the head-thorax region, but are really outside of 
the body. Most of the gills are plume-like in shape and are 
attached to the appendages, but some of them are attached 
to the thorax. Water is made to circulate through the gill 
chamber by means of the gill scoop or bailer. The finely 
branched gill affords a large amount of surface for the ab- 
sorption of oxygen. 
Excretion. - The organs for excretion of waste are the 
green glands that are found at the base of the antennae. 
Blood going to these glands loses some of the waste which 
it has gained in its course through the body. The method 
of purification of the blood in these glands is much the 
same as in the kidneys of the higher animals. 
Circulatory System. - The crayfish has a well-developed 
heart from which extend several arteries that carry blood 
to the various parts of the body. The blood returns to the 
heart through veins and through several irregular ducts 
called sinuses (si'nus-es). As the blood flows through the 
body it loses oxygen and receives carbon dioxide. Fresh 
oxygen is absorbed by means of the gills, which, at the 
same time, pass off carbon dioxide from the blood into the 
water. 
The Nervous System. - In the crayfish this is made up 
of a brain, ventral nerve chain, and many nerves. The 
eyes are borne on a pair of short movable stalks. The 
special senses are well developed, and the sense of taste is 
keener than that of most lower animals. 
99. Life History. - The sexes are distinct. The males 
may be distinguished from the females by the larger tubular 
appendages on the first and second segments of the abdomen. 
The eggs of the female become glued to the hairs of the 
swimmerets where they remain until hatched. In fact, 
young crayfish remain for about a fortnight after hatching 
grasping the hairs with their pincers. During this time 
they have fed for the most part on the yolk that was in the 116 
THE CRAB FAMILY AND HOW THEY LIVE 
Figure 64. - Nervous System of Crayfish. 
esoph, esophagus ; gs, " brain " ; gi, gth, ventral ganglia of thorax ; 
ga, abdominal ganglia; nc, nerve collar. ECONOMIC IMPORTANCE TO MAN 
117 
egg stalks and case. The young now begin to look like the 
parent. 
The common crayfish breeds annually and those that 
hatch from the eggs laid in the spring may, in turn, lay 
eggs the following spring. 
LABORATORY STUDY 
Place several crayfish in jars or aquaria and observe their behavior. 
Fill out the following report: 
DW™kY Do they Use Do they Make^Cub- 
Antennas? Forward? Ba™D? TailFin? Move Eyes? rent in 
W AT ER; 
100. Economic Importance to Man. - Shrimps, lobsters, 
and crabs are crustaceans of much economic importance, 
because of their food value. The trade in these animals 
amounts to millions of dollars each year. In order that 
these important food 
animals may not become 
exterminated by careless 
and excessive fishing, 
the state and national 
governments have at- 
tempted to control the 
numbers taken. 
The common crayfish 
has been used for centu- 
ries for food in Europe, 
while in France crayfish farming to increase the supply has 
been successfully practiced for some time. For many years 
crayfish have found their way to the markets of American 
cities which possess a large foreign population. Crayfish 
Figure 65. - Soft-shelled Crab Used 
for Food. 118 
THE CRAB FAMILY AND HOW THEY LIVE 
may also be harmful. They often burrow and may cause 
serious damage to dams and levees. At one time they were 
very destructive to the cotton planter 
by burrowing in the soil and feeding on 
the roots of the cotton plant. 
As a source of food the American 
lobster is widely used, as its body con- 
tains a large supply of meat. White men 
caught lobsters in Massachusetts Bay 
early in the seventeenth century. In 
1630 the English settlers were well ac- 
quainted with lobsters as food. From 
that time until now they have been re- 
garded as a delicacy. They are in such 
great demand that the states of the 
northern Atlantic coast have placed a size regulation to pre- 
vent small lobsters from being legally taken. 
The total value of the lobster fisheries in the United 
States is over a million dollars. About 
three fifths of the catch comes from the 
coast of Maine. The lobster fisheries of 
Canada are also important, ranking next 
to the codfish and salmon. 
In order to keep up the supply of 
lobsters, state and national governments 
have established hatcheries where the 
eggs are hatched artificially. During 
this process the eggs are protected from 
the animals that naturally feed on them. 
After the young lobsters are hatched, 
they are placed in the ocean. Lobsters 
come to maturity when about ten and 
one-half inches long. Young lobsters 
lay about 10,000 eggs, while an older one may have over 
90,000 eggs attached to its body. 
Figure 66. - Cyclops 
Figure 67. - Pill-bug 
One of the common 
crustaceans found un- 
der boards. MYRIAPODS 
119 
Shrimps and the blue crab (Figure 65), are also an im- 
portant food for man, while the minute crustaceans are an 
important food for fish and whales. 
101. Other Crustaceans. - Crustaceans of less economic 
importance than shrimps, crabs, and lobsters are the bar- 
nacles which cling to rocks, wharves, and ships; the hermit 
crabs that live in the shells of mollusks (mol'lusks) ; and the 
smaller fresh-water crus- 
taceans such as the Cy- 
clops (si'klbps), Daphnia 
(daf'ni-a), and Cypris 
(sl'pris), which are barely 
visible to the unaided eye. 
102. Arachnids.-The 
spiders, scorpions (skor'- 
pi-uns), ticks, and mites 
are arthropods that are 
grouped together under 
the name Arachnida 
(a-rak'ni-da: Greek, ar- 
achne, spider). The spi- 
ders and scorpions have 
eight walking appen- 
dages. The forward pin- 
cers of the scorpions are 
mouth parts, and not 
walking appendages. The harvestman {daddy-long-legs') is a 
harmless arachnid which does good by destroying injurious 
insects. Spiders catch insects either by pouncing upon them 
or by entangling them in their webs. Scorpions sting se- 
verely, but the wound, although painful, is rarely fatal. Some 
ticks and mites are parasitic on man and beast, and may 
transmit dangerous diseases such as the Texas fever of cattle. 
103. Myriapods. - Another group of arthropods is the 
Myriapoda (mir-i-a'po-da: Greek, myrioi, ten thousand; 
Photograph by J. H. Comstock. 
Figure 68. - Spider. 120 
THE CRAB FAMILY AND HOW THEY LIVE 
pous, foot, root, pod), a group which includes animals of 
many legs such as the centipedes (sen'ti-pedz) and 
" thousand-legged worms." Centipedes are provided with 
poison glands, hence their bite is fatal to some of the 
smaller animals and painful to man. The thousand-legged 
worms or millipedes 
are harmless. 
104. Importance 
of the Mollusks to 
Man. - There is an- 
other group of ani- 
mals, the mollusks, 
that have had an in- 
timate relation to 
man from his earliest 
appearance in this 
country. Huge piles 
of shells of clams and 
oysters remain as 
records of his earliest 
feast celebrations. 
They were made be- 
fore he had learned 
to write. From this 
ancient time until to- 
day, when the oyster 
industry is valued at 
815,000,000 and the 
clam industry at $1,000,000, these animals have held an im- 
portant economic place in the life of man. 
These animals differ from the crustaceans in having an 
unsegmented body which is usually covered by an exoskele- 
ton. This external skeleton consists of a single piece in snails 
and of two parts or valves in clams. When the clam moves 
naturally, the hinge between the two valves is uppermost 
With permission of Nature Magazine. 
Figure 69. - Web of Spider. IMPORTANCE OF THE MOLLUSKS TO MAN 
121 
while the opening between the valves allows the foot to 
be extended into the mud (Figure 71). The foot is a thick, 
muscular mass, not at all foot-like 
in appearance, but it enables the 
clam to move slowly and at an even 
rate. 
The great majority of buttons used 
by mankind to-day are made from 
the shells of clams and mussels. The 
Pearl Button Industry in the United 
States has developed until in 1914 
the manufacturing plants were valued 
at 84,900,000. In 1921 over 8700,000 
worth of pearl buttons were exported. 
Only the shell is used, the flesh of the 
clam being sold as fertilizer, or used 
for poultry food. 
A few years ago this industry prom- 
ised to fail because the life history 
of the fresh-water clams was not understood. Two well- 
known biologists were employed by the United States Gov- 
ernment to work out 
the breeding habits and 
methods of hatching and 
conditions of growth. 
They found that the 
newly hatched clam (Fig- 
ure 73) consists of two 
parts with teeth on the 
edge. This young clam 
swims about opening 
and closing what looks 
like an animated pincer. 
As it opens and closes it may come in contact with either 
the fins or gills of a fish. Here it remains for some time, 
Figure 70. - a, Milli- 
pede ; b, Centipede. 
Figure 71. - Clam, Showing Foot. 
Water enters through i.s., inhalent siphon, 
and leaves the body of the clam through 
e.s., exhalent siphon. 122 
THE CRAB FAMILY AND HOW THEY LIVE 
finally dropping off into the water, still a very small clam. 
If it does not attach itself to a fish, it dies. Just as soon as 
these facts in the life history of clams were well understood, 
it was possible to formulate regulations governing the time 
Figure 72. - Inside of Clam Shell. 
Showing anterior(a.a) and posterior (p.a.) 
adductor muscles. Buttons are made from 
this shell, which is the external skeleton of 
the clam. 
Figure 73. - Embryo of Clam. 
At this stage it becomes at- 
tached to the gills or fins of a 
fish. Here it remains for some 
weeks, gradually transforming 
into a clam. 
when clams could be properly taken and the kinds of fish 
best suited to their development. 
OUTLINE 
Crustaceans 
Crayfish 
Body 
Skeleton 
Cephalothorax 
Abdomen 
Appendages 
Legs 
Swimmerets 
Walking 
Others 
Maxillae 
Mandibles 
Antennae 
Eye-stalk 
Life processes 
Life history- 
Molting 
Economic importance 
Arachnids 
Spiders 
Scorpions 
Ticks 
Daddy-long-legs 
Myriapods 
Centipedes 
Millipedes 
Mollusks 
Clams 
Oysters 
Mussels QUESTIONS 
123 
SUMMARY 
The crustaceans are so called because of their hard outer shell. Of 
the division called Arthropoda, crabs, lobsters, and shrimps are the best 
know varieties. All three are of economic importance to man as food. 
They have a body consisting of cephalothorax and abdomen, while 
their many appendages include legs, mandibles, antennae, and others. 
They have the same life processes as all animals and an interesting life 
history. They molt in order to allow for growth. 
The mollusks and arachnids do not belong to the crustaceans. The 
former include clams, lobsters, and mussels, while to the latter division 
belong the spiders, scorpions, and ticks. 
With what crustaceans are you most familiar? Describe the cray- 
fish. How many parts has its body? What kind of appendages does 
it have? How does it take food? Respire? Excrete? Describe its 
circulatory and nervous systems. Where do the eggs remain until 
hatched? What is molting? How are crabs and lobsters important 
to man ? 
What are mollusks? How many kinds do you know? Of what use 
are they to man? Name some crustaceans. To what group do 
spiders belong? What is their value to man? Which of the myria- 
pods are harmful and which harmless? 
QUESTIONS 
Calkins, Biology, Chapter VII. 
Cockerell, Zoology, Chapter XXXV. 
Jordan, Kellogg, and Heath, Animal Studies, Chapter IX. 
Pearse, General Zoology, Chapter XI. 
Smallwood1, Textbook of Biology, Chapter XVII. 
United States Fisheries, Bulletin, Vol. XV, 1895, American Lobster. 
Study of its habits and development by F. H. Herrick. 
REFERENCES CHAPTER X 
A SIMPLE VERTEBRATE, THE FISH 
0 scaly, slippery, wet, swift, staring wights, 
What is't ye do ? what life lead? 
- Leigh Hunt 
105. Vertebrates. - All the animals which we have 
studied so far are called Invertebrates, because they have 
no backbone. We are now to study the Vertebrates, animals 
with a backbone, such as fishes, frogs, snakes, birds, and 
mammals. 
The most conspicuous characteristic of vertebrates is the 
presence of a backbone. The formation of the backbone is 
always preceded by the growth of an embryonic group of cells 
that do the work of a skeleton. This embryonic group of cells 
forms a structure which is called the notochord (nb'tb-kdrd: 
Greek, notos, back; chorda, cord). In all the true verte- 
brates (such as fishes, frogs, etc.), the notochord is gradually 
absorbed and the backbone takes its place, but between the 
vertebrse it remains as cushions. But in the fish-like 
vertebrate called Amphioxus (am-fi-bks'us), the notochord 
persists and there is never a true backbone. The notochord 
is always found above the food tube and below the spinal 
cord. 
Another characteristic common to all vertebrates is the 
presence of gill-slits. In the fishes these are external open- 
ings on each side of the neck that allow the water to pass 
over the gills. Such structures are of use only to aquatic 
124 FISHES 
125 
animals, and yet all vertebrates have them at some time in 
their development. 
The skeleton of most vertebrates is composed of bone. 
There are usually two pairs of appendages (legs, wings, or 
fins) attached to the body at the shoulder and hip. Here 
special bones join the limb to the body. The bones in the 
shoulder are known as the pectoral (pek'tb-ral) girdle ; while 
those in the hip are termed the pelvic (pel'vik) girdle. In 
the snakes, only traces of legs are found. 
Figure 74.- Perch, an Important Food-fish Common in Nearly All 
Freshwater Ponds. 
A further distinguishing feature of all vertebrates is the 
well-developed nervous system, with its large brain. The 
sense organs, eyes, ears, and the like, are also better de- 
veloped than in any of the invertebrates. 
Oxygen is obtained by external or internal gills in most 
aquatic animals and by lungs in all other vertebrates. In 
many vertebrates the skin is an active agent in the inter- 
change of oxygen and carbon dioxide and particularly in 
those animals which have a thin, moist skin like frogs. 
106. Fishes. - The fishes are vertebrates, that is, they 
have a notochord which, as they develop, gives place to a 126 
A SIMPLE VERTEBRATE, THE FISH 
vertebral column. There are four large divisions of fishes: 
(1) the lampreys (lam'priz) and their relatives, (2) the 
sharks and their kin, (3) the bony fishes, and (4) the small 
-Caudal Fin 
Figure 75. - External Parts of Fish. 
group of fishes with lungs. The bony fishes constitute the 
most important group in numbers and economic importance. 
This group includes the salmon (sam'un), trout, bass, white- 
fish, pike, shad, menhaden (men-ha'd'n), cod, mackerel, 
herring, sardine, etc. Typical bony fishes are the goldfish, 
perch, and sunfish (Figures 74 and 77). 
107. External Parts of a Fish. - The external parts of a 
fish consist of a well-marked head attached directly to the 
trunk; a trunk region, the largest part of 
the body; and a tail region which is some- 
times as long as the trunk. 
In a bony fish the eyes are well-developed 
and the mouth is at the front end of the 
head. The jaw bones, bearing many small, 
needle-like teeth, are not firmly attached to 
the skull. The side of the head next to the 
trunk is protected by a piece of bone that 
covers the gills (gill cover or operculum, 
6-per'ku-lum). 
The trunk bears a number of appendages 
called fins. Each fin is furnished with several bony fin-rays 
covered by a thin fold of skin. On the shoulder and hip 
Figure 76. - 
Scales of Fish. David Starr Jordan was born in Gainesville, N. Y., 1851, and 
is still living. He took his master's degree from Cornell in 1872, 
his medical degree from Indiana Medical College in 1875, and his 
doctor of philosophy degree from Butler University in 1878. Since 
then he has received the honorary degree of doctor of laws from 
four of the leading American Universities. 
In addition to teaching biology for many years, he has written 
numerous technical and popular books on various phases of biology. 
From 1885 to 1913 he was President first of Indiana University 
and then of Leland Stanford University. During all this time he 
continued his scientific studies. He is one of the most eminent 
authorities on fishes in the United States. Dr. Jordan's life and 
attainments are striking examples of what an American boy can 
accomplish by his own efforts and individuality. LOCOMOTION 
127 
regions of the trunk, the fins occur in pairs and are called 
the pectoral and pelvic fins. Several fins are found that are 
not in pairs. These are the median fins of the trunk. 
The caudal or posterior region of the fish ends in a large 
median fin. The tail region is chiefly important in locomo- 
tion, but the fins also help in balancing and steering. 
Scales cover the trunk and tail, each one overlapping the 
next like the shingles of a house. The skin is full of mu- 
cous glands that keep the fish covered with slime. Both 
the slime and the scales protect the fish (Figure 76). 
LABORATORY STUDY 
Study living fish, such as goldfish or perch. Place one or two in an 
aquarium and observe their behavior. Fill out the report below. 
M_ wt. Number of Number of Which are Used to Do the 
Paired Unpaired Eyes 
Fins Fins Advance? Stop? Balance? Move? 
Note the shape and relative position of the head, trunk, and tail 
region. The gills are covered by a bony shield, the operculum. What 
is its size and how attached? Where are the eyes located? Do they 
move ? Can the eyes be closed ? How is the body covered ? Of what 
use is this covering to the fish? 
108. Locomotion. - The bodies of such fishes as are 
shown in Figures 74 and 77 are adapted to swimming. The 
tapering head offers but little resistance to the water and 
the general spindle-shape of the whole body enables it to 
move easily when completely surrounded by water. Not- 
withstanding that there are paired fins which are similarly 
placed to the paired legs of a frog or dog, these fins are not 
important in giving speed to the fish's movements. They 128 
A SIMPLE VERTEBRATE, THE FISH 
act as brakes when the fish desires to stop, the brake being 
applied by simply straightening out these paired fins at 
right angles to the body. The median fins on the back and 
lower surface of the body keep the fish from tipping over and 
are chiefly for balancing, the paired fins also assisting in this 
process. The tail of a fish is supplied with a large terminal 
Figure 77.- Sunfish or Pumpkinseed. 
The one usually caught by the small boy fisherman. 
fin. This fin and the tail which is often one third of the 
entire length of the body of rapidly swimming fish, is the chief 
organ of locomotion. Movement is produced by a rapid 
sidewise motion of the tail. 
109. Food-taking. - Fishes eat insects, worms, crayfish, 
snails, and other fish. The teeth of fish serve to seize, tear, 
and hold food. None of the fish have teeth which are 
adapted to chewing the food, as is the case among the 
higher vertebrates, like the dog, horse, and man. FOOD-TAKING 
129 
The insects which form the principal diet of many fish 
are so well known that anglers select special ones for bait. 
However, not all water insects are eaten by fish. Con- 
trary to the usual order of things, there are insects that kill 
fish. The fish-killing insects spend all of their time in the 
With permission of Nature Magazine. 
Figure 78. - Fish-eating Insect. 
water except when migrating from pond to pond or during 
the mating period. They conceal themselves beneath stones 
or lie partly buried in the mud. From these places of hiding, 
they dart out and seize their victims with their jaws or 
claws. The water-tiger, a larva of one of the water beetles, 
is equipped with curved, sharp, hollow jaws with which it 130 
A SIMPLE VERTEBRATE, THE FISH 
pierces its prey and sucks the juices of the body. The 
largest and most destructive of these fish-killing insects is 
a true bug (Figure 78) which grasps the fish with its curved 
fore-legs, plunges its large, sharp beak deep into the fish 
and then slowly sucks its blood. These and other insects 
feed on the eggs of fish so that, when artificially hatching 
fish, man has to protect the eggs and young fish from insects 
which we used to think were only a source of food to the 
growing fish. 
In fishes which eat minute animals and plants the four 
pairs of gill arches are adapted to support many sharp- 
pointed projections on the inside. These act as strainers and 
gather quantities of this small food as the water passes over 
the gills. These projections are called gill rakers (Figure 79). 
Their development seems to vary in proportion as they are 
needed for service. Fishes that feed on crayfish and on 
small fish have no use for gill rakers or strainers and ac- 
cordingly their gill rakers are undeveloped. 
The food captured by the teeth of the fish or caught in 
the gill strainers passes at once into a short esophagus which 
expands into the thick-walled stomach. Here the various 
plants and animals that have been swallowed undergo 
partial digestion, the remainder of the process being com- 
pleted in the intestines. The dissolved foods are absorbed 
through the walls of the stomach and intestine by osmosis 
and pass into the blood. The main parts of the digestive 
system and their adaptation to digestion are the same as 
in all the higher vertebrates. 
110. Gills and Respiration. - Water is taken in through 
the mouth and passes out through two openings, one on 
each side of the neck. In each opening four or five gills 
are found. The gills are a series of vascular arches made 
up of numerous, small, very short, fleshy threads or fila- 
ments (Figure 79). Into each filament a blood vessel pene- 
trates and here the blood throws off carbon dioxide and takes CIRCULATION 
131 
oxygen from the water by osmosis just as the blood of the 
crayfish does. The thin-walled gill filaments are adapted 
to respiration in the water. The water is drawn into the 
mouth and forced out over the gills in much the same way 
as water is pumped from a well. When a fish opens its 
mouth, the water rushes in. As the mouth is closed, the 
..Gill Filaments. 
^Gill Rakers 
Gill of file Fish 
Gill of White Fish 
Figure 79.- Gills of Fishes. 
floor of the mouth and throat is raised slightly, pushing the 
water against the side of the neck and through the gill open- 
ing. The mouth is thus emptied of water so that when it 
is opened again more water flows in. 
111. Circulation. - The blood of fishes is carried in well- 
defined blood vessels and a heart of two chambers. The 
blood is sent from the heart to the gills, where it is purified 
of carbon dioxide and receives oxygen. It is then carried 132 
A SIMPLE VERTEBRATE, THE FISH 
by means of arteries to other parts of the body, where the 
oxygen in turn is given up and carbon dioxide is received. 
The blood from the gills and other parts of the body is re- 
turned to the heart through veins. Because the tempera- 
ture of the blood of fishes is lower than that of man and 
changes with the seasons, they are called cold-blooded ani- 
mals. 
112. Excretion. - The waste produced in all parts of the 
body as a result of the use of oxygen in the process of oxida- 
tion is in the form of a gas known as carbon dioxide. This 
gas is carried in the blood to the gills where it passes by os- 
mosis through the thin walls of the gill filaments into the 
water. In addition to oxidation, there are other vital pro- 
cesses taking place in all the cells of the body of the fish. 
These vital processes produce waste substances that exist 
in the form of liquids which are gathered up by the small 
blood vessels and carried to the kidneys of the fish. Here 
these liquid wastes are extracted from the blood and are 
cast off from the body. 
113. Nervous System. - The nervous system of a fish 
consists of a spinal cord and a well-developed brain. There 
is no structure in the nervous system of a crayfish that can 
be compared to the brain of a fish. Many nerves connect 
the brain and spinal cord with all parts of the body and 
these nerves belong to the nervous system. Associated 
with better development of the brain are special sense 
organs. 
Special Senses. - The eye is well developed. It is glob- 
ular and projecting, and it is believed to be near-sighted. 
The organs of smell are usually located in the nasal cavity. 
In the bullhead, they are found in the feelers, on the head, 
and even in the skin of the tail. The ear is under the skin, 
and there is no external opening. As water conducts sound 
vibrations more readily than air, no device for gathering 
sound waves is necessary. REPRODUCTION 
133 
114. Reproduction. - The sexes of fish are distinct. At 
certain seasons many fish migrate upstream to lay their 
eggs (to " spawn "). Eggs are laid in large numbers by 
Figure 80. - Eggs of the Land-locked Salmon. 
the females, and in the same locality sperm cells are dis- 
charged into the water by the males. The sperms unite 
with the eggs. The fertilized eggs hatch after thirty or 
forty days, or longer, depending on the kind of fish and 
the temperature of the water. The yolk of the eggs is 
Figure 81. - Young Fish Just at the Hatching Stage. 
The large mass under the neck is the yolk or food used by the young fish 
before it is able to capture its own food. Note that there are no fins and 
that the gills are not well developed. 
attached to the young fishes for many days after they are 
able to swim, and supplies all the food they need during this 
time (Figure 81). 134 
A SIMPLE VERTEBRATE, THE FISH 
The spawning habits of fish must be understood thor- 
oughly if they are to be raised artificially, as is done in the 
many fish hatcheries. Most states have scientific game 
laws which protect the fish during their egg-laying period 
when they are easily caught and when the destruction of 
even a few fish means the loss of thousands of eggs. 
Spawning habits vary greatly. Some fish, like the sal- 
mon, make long journeys from the sea to the head waters 
of rivers and streams to deposit their eggs. The Columbia 
River is famous for the number of salmon which spawn 
there. Other fish, like shad, go up a river only a short dis- 
tance to lay their eggs. Many shad, for instance, go up the 
Hudson River in New York State. 
Figure 82. - Young Fish Seventeen Days after Hatching. 
It has absorbed the large mass of food and the fins and gills are large 
enough to be used by the young fish which must capture its own food 
from now on. 
115. Care of Young. - Some fish, like the sticklebacks, 
build nests of sticks and leaves in which the eggs are placed 
and guarded. Bass and sunfish make a circular depression 
several feet in diameter near the shore and lay their eggs on 
these so-called " beds." These beds are guarded zealously 
by the males, who drive off or carry away crayfish and small 
fish which feed upon such eggs. In former times men sought 
for these " beds " and by dropping a baited hook caught the 
bass while defending their eggs. Fortunately this practice 
is now illegal. Generally, adult fish pay no attention to 
their young and in many cases they devour young of their 
own kind as quickly as fish of other sorts. 
116. Life History of the Eel. - This well-known fish of 
the inland streams and lakes has had so many stories and 
myths in connection with its development that much effort COMMON FOOD-FISHES 
135 
has been made to learn the facts. Eels migrate down- 
stream to the larger rivers and eventually to the ocean in 
the fall of the year. Here in the region of mud banks the 
females lay their eggs in great numbers and the sperm cells 
of the males fertilize them. In some cases the females lay 
as many as 10,000,000 eggs at one time. After the eggs are 
laid the adult eels remain in the ocean a few weeks and die. 
The young eels pass through the larval stage in about three 
weeks after the eggs start to hatch. 
At the beginning of the second spring the young eels start 
on their trip back to fresh water. Great numbers of them 
may be seen in the spring at the foot of Niagara Falls where 
they are blocked by the great cataract. By crawling over 
stones and along the banks, young eels are able to get above 
ordinary falls in the streams and rivers. 
The eel is a food-fish. The commercial value of the eel 
is well known to fishermen. They are rich in oil and highly 
nutritious. Eels vary in weight from three and a half to 
six and a half pounds and often exceed three feet in length. 
117. Importance to Man of the More Common Food-fishes. 
- The United States, including Alaska, takes from the water 
about 2,000,000,000 pounds of fish, annually. Alaska pro- 
duces about one fourth of this total. The hatcheries of the 
United States have an output of 4,500,000,000 eggs, fry, and 
small fish. 
Some of the fish have been caught in such great numbers 
that they are growing rather scarce. Some are holding to 
their normal numbers and a few others are increasing. In 
the last class belong the carp, kingfish, whiting, Pacific 
shad, and Pacific herring. Many edible fish are not eaten 
merely because people do not know about them or perhaps 
are prejudiced. Examples of such fish are sharks, toadfish, 
skates, grayfish, burbot, and menhaden. 
The Carp. - This is one of our most abundant fishes in 
the lakes and inland streams. About 43,000,000 are sold 136 
A SIMPLE VERTEBRATE, THE FISH 
each year in this country. Since this species is hardy, easy 
to raise, easy to catch, and has high food value it is desirable 
that more of them be eaten. 
The Grayfish. - The grayfish is found along the Atlantic 
coasts. Although its food value and flavor are equal to that 
Figure 83. - The Grayfish Belongs to the Shark Family. 
It is very destructive in its food habits, eating the highly prized food-fish. 
How will the use of this fish for food help the fish industry ? 
of the tilefish and other food-fishes, it has not been market- 
able until recently. Unfortunately, when the fish was first 
named it was called " dogfish " from its biting habits. With 
that name people would not buy it. Now that it has a 
better name it is coming into use as a food-fish. Its abun- 
dance enables fishermen to offer it for a relatively small price. 
Figure 84.---The Whiting or Eulachon. 
A food-fish recently placed on the market 
The Whiting. - This is another good food-fish that has 
only recently been in demand as a food. In 1898 less than NECESSITY OF FISH PROTECTION 
137 
50,000 pounds were sold, while in 1908 more than 10,000,000 
pounds were marketed. Since that time there has been a 
constant increase in the consumption of this fish. In Eng- 
land during 1913 about 70,000,000 pounds were sold at a 
price higher than haddock. The whiting occurs off the coast 
from New York northward. It can be bought fresh, canned, 
salted, and smoked. 
118. Necessity of Fish Protection. - As the human race 
increases in number it requires more and more food. Since 
This is the most highly prized fish among fishermen. It is rapidly be- 
coming extinct except where protected by law. 
Figure 85. - Brook Trout. 
most people are fond of fish, these animals are caught in 
ever-increasing numbers by the men who supply the fish 
markets. These men pay little attention to the necessity 
of giving the fish an opportunity to lay their eggs undis- 
turbed ; so the government has made laws to protect the fish. 
During the past twenty-five years in particular the breed- 
ing habits of fish have been thoroughly studied, and the 
breeding period has been the basis for all of the protective 
laws. This is the reason that the closed season for one kind 
of fish is different from that for another. 138 
A SIMPLE VERTEBRATE, THE FISH 
Fish are subject to disease just as men are, and they must 
be protected from certain disease germs. Also fish which 
harbor parasites in their flesh are unsuitable for food, and 
for this reason we should find some way of destroying these 
parasites. When large numbers of fish are found dead, the 
state department in charge of fish tries to discover the 
cause. 
The Bureau of Fisheries is one of the subdivisions of the 
United States Department of Commerce. The original 
work of this bureau was to inquire into the causes of the de- 
crease of food-fish in order to find means of checking these 
decreases, and of increasing the supply whenever possible. 
During the year 1922 the following studies on fish were 
carried on : Alaskan and Pacific coast salmon investigation; 
the fishes of Chesapeake Bay; experimental investigations 
in fish culture; a study of the diseases and parasites of fish. 
119. Fish Hatcheries. - In the natural state, many eggs 
are laid that never hatch because the sperm cells do not 
come in contact with them; and of the fishes that are 
hatched only a small proportion reach maturity. As it is a 
matter of great economic importance that fishes be saved 
from extermination and their numbers largely increased, the 
governments of the world have established hatcheries where 
fish are raised in great numbers. 
In these hatcheries the eggs are taken from the female 
and placed in a jar, and the mass of minute sperm cells or 
" milt " is taken from the male and poured over the eggs, 
so that practically all the latter hatch. Then by giving the 
developing eggs protection, and the young fish sufficient 
and proper food, nearly all these eggs develop into active 
fish and the great loss that comes to the fish developing in 
their natural environment is prevented. When they are 
able to take care of themselves, these fry, as the young 
hatchery fish are called, are taken to natural feeding grounds. 
In New York State and most other states there are state HUMANE METHODS OF CATCHING FISH 
139 
hatcheries where such fish as shad, pike, lake trout, salmon, 
and brook trout, are raised by millions. 
The fish that are most useful as food are taken by hooks, 
nets, and seines, under certain restrictions. Those like 
brook trout which are caught as much for sport as for food, 
can be taken only by a hook and line and in certain seasons, 
the season of the year depending upon the time of spawning. 
The brook trout spawns in August and September, while 
the rainbow trout does not spawn until February or March. 
120. Humane Methods of Catching Fish. - Every one 
who has ever been fishing knows that many of the fish 
caught are too small for use. The protective fish regulations 
make it illegal to keep them. They should be put back 
into the water. What is the proper way to remove them 
from the hook? When taking any undersized fish off the 
hook, always wet your hand before grasping the fish ; other- 
wise, the dry hand will remove the slime from the back of the 
fish. This slime is a protection to the fish, for the numerous 
microscopic plant spores that thrive on fish are unable to 
gain a foothold except where the slime has been removed. 
If these spores do get a foothold, they may kill the fish. 
The fish that are large enough to keep should be killed 
as soon as taken from the hook. This can be done by hitting 
them with a stick on the head, back of the eyes. It will 
avoid all suffering and make the fish far better for table use. 
These two simple things that every one can do are rec- 
ommended by all of the fish and game commissioners 
throughout the United States. 
OUTLINE 
Vertebrates 
Distinguished by 
Backbone 
Gill-slits 
Lungs 
Nervous system 
Fishes 
Body 
Head 
Trunk 
Tail and Fins 
Scales 140 
A SIMPLE VERTEBRATE, THE FISH 
Life Processes 
Locomotion 
Food-taking 
Respiration 
Circulation 
Excretion 
Nervous system 
Special senses 
Reproduction 
Spawning 
Care of young 
Kinds of fishes 
Eel 
Life history 
Carp 
Grayfish 
Whiting 
Fish protection 
Hatcheries 
Humane methods of catching 
fish 
Vertebrates are distinguished from invertebrates by having back- 
bone, gill-slits or lungs, and a well-developed nervous system. Fishes 
are a good illustration. They have head, trunk, tail, fins, scales, 
and have all the life processes of the other animals which we have 
studied. There are many kinds of fishes, most of which are or may 
be, used as food. Their economic importance is enormous. Because 
of this there are laws for fish protection and the various governmental 
bodies have established fish hatcheries, where the young may be 
brought to maturity under protection from their natural enemies. 
SUMMARY 
QUESTIONS 
What are the chief differences between vertebrates and invertebrates ? 
What do land vertebrates have to correspond to the gill-slits of a fish ? 
Of what three parts does the body of a fish consist? What are the 
fins? the scales? Describe the life processes of the fish. Have they 
any special senses? What is "spawning"? How do fishes care for 
their young? How many kinds of fishes do you know? Are they 
all good to eat? How important is the fish industry to man? What 
methods of fish protection are practiced and by whom? 
REFERENCES 
Fish Manuals of the U. S. Commission of Fish and Fisheries. 
Harris, Salmon and Trout. 
Henshall, Bass, Pike, Perch and Others. 
Jordan, Fishes. 
Jordan and Evermann, American Food and Game Fishes. CHAPTER XI 
FROGS AND THEIR WAYS OF LIVING 
When by night the frogs are croaking, kindle but the torch's fire; 
Ha! how soon they all are silent! 
- Longfellow 
121. Amphibians. - Frogs and toads are the best known 
animals of this group ; but here belong also the Salamanders 
(sal'a-man-ders), frequently miscalled lizards (see page 1(>4). 
The amphibians (am-fib'I-ans: Greek, amphi, both ; bios, 
Figure 86. - Some Common Salamanders Found on Land. 
life) are all small, the largest one found in America being 
a salamander (Cryptobranchus), which is rarely more than 
two feet long. This term amphibian is used to explain the 
habit which frogs, toads, and certain salamanders have of 
141 142 
FROGS AND THEIR WAYS OF LIVING 
spending their larval (tadpole stage) life in the water and 
their adult life on land, or partly on land and partly in the 
water. 
LABORATORY STUDY 
Place one or two frogs or toads in a small jar or box and observe the 
points mentioned in the report below. 
Do They CPro™ctY HThe?° Can They How Do How Do They 
Wink? The™ Eyes? GetaIr? Walk? Hop? They Swim? Catch a Fly? 
122. Frogs. - The general form of the body, the shape 
of the head, the long hind legs adapted for jumping, and the 
webbed toes for swim- 
ming are much the same 
in all frogs. There are 
several kinds, one of 
which, the leopard frog, 
is found generally distrib- 
uted throughout the 
United States. It can 
be recognized by the 
presence, on the back, of 
many brownish or green- 
ish spots, edged vzith 
white, which help the frog to escape the notice of his enemies 
as he squats among the water weeds. These colors form 
rather definite bands on the hind legs, though there is much 
variation. • 
Figure 87. - Leopard Frog. 
Compare the general shape of fish and frog. How do the colors 
differ? Show how the legs and feet are adapted to the way the frog 
LABORATORY STUDY Jean Louis Rudolphe Agassiz was born in Switzerland, in 1807, 
and died at Cambridge, Massachusetts, in 1873. Agassiz intro- 
duced the laboratory method in zoology to students of America 
and trained many who have become prominent in biology. His 
motto, " Study nature, not books," has been taken as a motto by 
thousands of students all over the world. He was the founder 
of the summer laboratory method of study now so common, the 
first such laboratory having been held at Penikese Island off 
the coast of Massachusetts. He was Professor of Zoology and 
Geology at Harvard and curator of the museum that now bears 
his name. His scientific contributions covered a wide range of 
subjects in zoology and geology. RESPIRATION 
143 
lives. Is the frog sensitive to touch in various parts of the body ? Ex- 
amine the eyes. Open the mouth and see that the frog can draw in 
its eyes. The ear membrane is on the side of the head back of the eyes. 
Pass a probe through the ear membrane of a dead frog and see where 
it comes out in the mouth. This is the opening of the Eustachian tube. 
How far can the living frog see? Notice the method of breathing. 
See the throat move up and down. Hold the frog under the w7ater 
and gently rub its sides. It will usually croak. Thus we can prove 
that the frog is able to make the air travel from his lungs to his mouth 
and back again while under water. 
123. Food-taking. - Frogs are greedy creatures. They 
will eat almost any animal small enough to be swallowed, 
such as insects, worms, snails, tadpoles, and small frogs. 
These are caught alive and when in motion. The frog has 
a sticky tongue with a forked end for catching small insects. 
124. Respiration. - The lungs are hollow sacs that lie 
back of the stomach, one on each side. In the freshly killed 
animal, these can be filled with air by inserting a blow-pipe 
into the windpipe and blowing air into them. The empty 
lungs are about as large as the blunt end of a lead pencil. 
The oxygen of the air passes through both the skin and the 
lungs into the blood of the frog, and the carbon dioxide of the 
blood is thrown off through these same two organs. The 
frog has large blood vessels close to the skin, especially along 
the back. These send many fine branches into the skin. 
This explains why the frog can " breathe " through its skin. 
When the frog remains under the water for a long time, as 
during the winter, all the oxygen used enters the blood 
through the skin. When the air is taken into the mouth, 
it is forced into the lungs by the muscles on the floor of the 
mouth. In a way, the air is swallowed into the lungs rather 
than breathed in as in the case of mammals. Experiments 
have been made which show that the frog can get oxygen in 
sufficient quantities to maintain life, even if it has not the 
use of its lungs. The frog thus possesses two organs of respi- 
ration, the skin and lungs. 144 
FROGS AND THEIR WA YS OF LIVING 
125. Digestion. - The mouth is large. Short lips cover 
the short teeth in the edge of the upper jaw. The tongue, 
which has two fleshy horns at the back end, is attached by 
the front end to the floor of the mouth. The frog can 
aortic arches 
- trachea 
auricle 
- ventricle 
lung 
pulmonary artery 
dorsal aorta 
testis- 
adrenal - 
- kidney 
-ureter 
-large intestine 
bladder- 
Figure 88. - Diagram Showing Organs of Frog. 
throw its sticky tongue over the tip of the lower jaw and 
use the forked end to catch insects which are then carried 
into the back of the mouth. Two groups of little curved 
teeth in the roof of the mouth aid in preventing the escape 
of the prey. The food is swallowed whole. The esophagus DIGESTION 
145 
(the tube connecting the mouth cavity and stomach) of the 
frog can be stretched so that a comparatively large animal 
can be swallowed. There is no sharp limit between the 
esophagus and the stomach, which is a long, spindle-shaped 
sac (Figure 89), larger than the rest of the digestive tube. 
mouth cavity 
oesophagus 
liver - 
gall bladder^ 
silver 
bile duct 
stomach 
pancreas 
pyloric valve 
small intestine - 
- large intestine 
Figure 89. - Digestive Tract of Frog. 
The small intestine begins at the back end of the stomach 
as a small tube which makes several turns, and finally en- 
larges into a region called the large intestine, the last part 
of which is termed the cloaca (clo-a'ca) or common sewer. 
Two glands of importance belong to the digestive organs - 
the liver and the pancreas. The liver is a large, dark red, 146 
FROGS AND THEIR WAYS OF LIVING 
three -lobed organ that covers the ventral (lower) surface of 
the stomach. The pancreas is a whitish, small, irregularly 
shaped body attached between the stomach and the intes- 
tine. Both these glands drain into the intestine just beyond 
the stomach. The bile secreted by the liver is at first col- 
lected in a sac called the gall bladder. 
All these parts of the alimentary canal are held in place 
by a thin membrane, the mesentery (mes'en-ter-y), one edge 
of which is attached to the dorsal wall along the line of the 
backbone and the other to the stomach and intestine. A 
small gland (the spleen) is found in this mesentery. The 
spleen has no duct connecting it with 
any other organ in the frog. Blood 
vessels run through the spleen, a fact 
which scientists believe is important 
in making new blood corpuscles. 
126. Excretion. - This fundamen- 
tal life process is performed in the 
frog as in all other vertebrates. Like 
the fish, it has a pair of kidneys that 
remove the wastes from the blood in 
the form of liquids; while the skin 
and lungs allow such wastes as the 
gas, carbon dioxide, to be discharged 
from the blood. 
The kidneys are small red bodies 
lying close to the back. Each one is 
connected with the cloaca by a minute duct (ureter or urino- 
genital duct). The urinary bladder is attached to the cloaca 
(Figure 90). 
127. Reproduction. - The fundamental process of repro- 
duction in the frog family is the same as in all other animals, 
but there is introduced the tadpole stage which makes the 
reproduction of the amphibians different from that of any 
other vertebrate. 
Figure 90. 
Diagram to show the 
relations of the testes to 
the kidneys and the rela- 
tion of the kidneys to the 
intestine( cloaca). NERVOUS SYSTEM 
147 
The male frog has a pair of spermaries (sper'ma-riz), one 
attached to the front (anterior) end of each kidney (Figure 
90). Each spermary (testis) is yellow in color. The sperms 
escape through the kidney. In the female frog, ovaries, 
sometimes filled with eggs, are easily seen. A long, closely 
coiled pair of oviducts (o'vi'dukts) opens in front near the 
forward end of the stomach and in the back into the cloaca. 
The eggs break through the wall of the ovary and enter the 
oviducts. As the eggs pass down through the oviducts, they 
are coated with a jelly-like covering that swells in the water. 
This jelly covering protects the eggs. 
At the anterior end of each kidney in both the male and 
female frog is to be seen an irregular mass, the fat body, 
which contains stored energy that the frog uses as it begins 
to grow eggs or sperms in the early spring before there is 
plenty of food. 
128. Irritability. - In all vertebrates this life process is 
limited to the nervous system, which includes brain, spinal 
cord, nerves, and sense organs described below. Animals 
with definitely developed nervous organs and a specialized 
brain as in vertebrates are able to do more things than a 
worm, for example. The brain of a frog is really a very 
simple organ when compared with the brain of a dog. This 
is the main reason why a dog can be taught to do so many 
more things than a frog. 
129. Nervous System. - The nervous system of the frog 
is more highly developed than that of the crayfish. It con- 
sists of a central part inclosed in the backbone and cranium 
(braincase). This central nervous system in all vertebrates 
is always found above the digestive tube, and is divided into 
the brain and the spinal cord, from which numerous nerves 
arise and extend to all parts of the body. 
The parts of the brain are the same as in man and much 
easier to study. Beginning at the front (anterior) end of 
the brain the parts are as follows : (1) small olfactory (dl-fac'- 148 
FROGS AND THEIR WAYS OF LIVING 
t6-ry) lobes, which are not sharply marked off from the rest 
of the brain, and, as shown in Figure 91, connect with (2) the 
cerebral (ser'A-bral) hemispheres, which are oval in out- 
line. (3) A short mid-brain region, partly covered by the 
back part of the cerebral hemispheres, connects the front 
and back part of the brain. (4) Two large optic lobes, the 
widest part of the brain, 
are just back of the mid- 
brain. (5) The cerebellum 
(ser-e-bel'lum) of the am- 
phibians is small and 
easily overlooked (Figure 
91). The last region of 
the brain is the (6) medulla 
(mS-dul'la), which is oc- 
cupied by a large triangu- 
lar cavity called the fourth 
ventricle. 
The work which each of 
these regions of the brain 
does is not sharply defined. 
The olfactory lobes receive 
the smell stimuli. The 
cerebral hemispheres con- 
trol muscular action. 
When the latter are re- 
moved, the frog loses all 
power to initiate any 
movement and will sit still 
in a dry, warm room for hours unless disturbed. This he 
never does when the cerebral region of the brain is unin- 
jured. The mid-brain region is the passageway for all nerve- 
pathways that travel to and from the brain. The mid-brain 
and optic lobes explain to the frog the sight stimuli. In the 
frog, the cerebellum, which is poorly developed, is less im- 
•nerve to nose 
-Olfactory Lobe 
--Cerebrum 
■■•nerve to eye 
•-Optic Lobe 
Thalamencephalon 
Medulla- 
Cerebellum 
■Nerve to ear 
.4th Ventricle 
-nerve to arm 
v nerve 
w'to leg 
Figure 91. - Central Nervous System 
of Frog. NERVOUS SYSTEM 
149 
portant than in man. The medulla gives off more nerves 
than any other region of the brain. Here are found the 
nerves leading to the face, tongue, ear, heart, and lungs. 
While there is a great difference between the shape of the 
parts of the frog's brain and those of man, yet the work done 
by each region is of the same kind. 
The brain joins the spinal cord, without any external sign 
to indicate where one begins and the other leaves off. A 
definite number (ten pairs) of nerves leaves the brain proper. 
These are devoted to the special senses of the head and to 
moving the muscles of the throat and head. The frog has 
ten other pairs of nerves joined to the spinal cord (Figure 
91). In a long salamander there are twenty or thirty pairs 
of nerves on the spinal cord. 
LABORATORY STUDY 
In connection with the study of the frog, the following additional lab- 
oratory work should be done in order that the several organs of man 
which are discussed in Part III may be better understood. Frogs that 
have been preserved in formalin can be easily dissected. Wash them 
well in water to which ammonia has been added. Examine the di- 
gestive organs: first the mouth, then the esophagus, stomach, small 
and large intestine, and cloaca. For convenience, the liver will have to 
be removed. The pancreas can be seen as a small whitish structure in 
the loop between the stomach and the intestine. The spleen is a round 
red organ usually found near the large intestine. 
A pair of narrow kidneys lies close to the back and is connected by 
ducts with the cloaca. The spermaries are found attached to each kid- 
ney near the front end and the sperm cells escape to the exterior by the 
kidney ducts. In the female frog the large ovaries occupy most of the 
space of the body cavity. A pair of oviducts opens into the body cavity 
just back of the stomach. The eggs escape from the ovary into the body 
cavity. 
The nervous system is inclosed in bone that is easily removed from 
the dorsal surface. The brain should be studied and the following 
divisions recognized: cerebral hemispheres ending in front in the ol- 
factory lobes, which are not clearly marked. Just back of these are the 
two large roundish optic lobes which are attached to the mid-brain 150 
FROGS AND THEIR WAYS OF LIVING 
thalamencephalon (thal-a-m6n-c6plTa-16n). The cerebellum is small and 
the medulla passes into the spinal cord without any sharp dividing line. 
130. Life History of the Frog. - Late in March and early 
in April the frogs gather in ponds to lay their eggs. The 
eggs are surrounded by a jelly-like substance which holds 
them together. As the eggs are being laid by the female 
frog, the male frog spreads a large number of sperm cells 
over the whole mass. These sperm cells make their way 
Figure 92. - Frog Eggs. 
through the soft jelly and one of them must enter each egg 
or it cannot grow into a tadpole. 
Fertilization of the Egg. - As soon as the sperm cell enters 
the egg (Figure 93), it begins to change from a solid, pointed 
body into a round nucleus which is so much like the nucleus 
already in the egg cell that none but experts in this study 
can tell which came from the sperm cell and which from the 
egg cell. These two nuclei come in contact and unite, leav- 
ing but one nucleus in the egg (Figure 93). This last change 
is -fertilization, which is defined as the union of the contents LIFE HISTORY OF THE FROG 
151 
of the egg and the sperm nucleus. After this union is com- 
pleted the egg begins to divide into cells, as shown in Figure 
94, and finally a tadpole is grown. 
Egg Nucleus Sperm cell 
Egg Nucleus Sperm Nucleus 
Fused Nucleus 
a, The sperm cell is penetrating the cytoplasm of the egg; b, the head of 
the sperm cell has become transformed into a nucleus ; c, the egg-nucleus and 
the nucleus derived from the sperm head fusing. This fusing is fertilization. 
Figure 93.- Diagram Illustrating Fertilization in Frog Egg. 
Growth of the Tadpole. - As soon as the young tadpole 
hatches, it attaches itself to plants and lives for the first 
few days upon the food-yolk within its own body ; the mouth 
forms, and horny jaws 
develop. Then the tad- 
pole begins to feed upon 
minute plants and be- 
comes dependent upon its 
own skill to get food and 
escape its enemies. 
For a time the tadpole 
breathes through gills. 
Two sets are used. The 
first ones are on the out- 
side of the body and 
last for only two or three 
days, when internal gills 
form in the throat and the 
tadpole breathes much 
like a fish. 
Figure 94.-D.vid.ng Egg of Frog. 
After the has been fertilized as 
shown in Figure 93, the embryo begins to 
divide in a regular manner, a, Two-celled 
embryo; b, four-celled embryo; c, eight- 
celle^ emby°; d' thirty-^° t0 forty-eight- 
celled embryo; e, many celled stage; 
embryo beginning to form central nerv- 
OUS system. 152 
FROGS AND THEIR WAYS OF LIVING 
The Tadpole Becomes a Frog. - In the growth of the 
tadpole into a frog the hind legs appear first. Later the 
front ones begin to show and as they develop the tail is grad- 
ually absorbed. While 
these external changes 
are going on, there are 
many complicated internal 
changes taking place; in- 
ternal gills are disappear- 
ing and lungs, nerves, 
blood vessels, and muscles 
are being formed to give 
the new legs life and ac- 
tion. The internal lungs 
take the place of the gills 
in the throat before the 
legs are fully grown, and 
such tadpoles must rise to 
the surface to breathe air. 
Explain in Figure 96 which 
tadpoles breathe by lungs, 
and which by gills. This 
complicated way of grow- 
ing into a frog is called 
metamorphosis and this 
term has the same gen- 
eral meaning as when used 
to describe the growth of 
insects (page 58). 
The tadpoles of leopard 
frogs become small frogs 
in a single summer, but 
the tadpoles of bullfrogs and green frogs require two sea- 
sons to complete their development. These latter tadpoles 
hibernate in the. mud with adult frogs and toads. 
Figure 95. - The Embryo Becoming 
a Tadpole. 
a, first stage ; b, second stage; c, third 
stage. FROG'S HABITS AND MEANS OF PROTECTION 
153 
131. The Frog's Habits and Means of Protection. - 
Frogs are seldom found far from some pond or stream on 
the bank of which they are usually seen. When disturbed, 
they jump into the water, swim to the bottom, stir up the 
mud, and quietly come to rest a short distance from the 
place where they entered. They are protected also by their 
color, which usually resembles the grass and rocks among 
The smallest tadpole, black, on the bottom of the aquarium jar is a toad 
tadpole about three months old. The other two tadpoles on the bottom are 
frog tadpoles about three months old; while the two tadpoles with legs are 
frogs. The larger is about one year old and the smaller three months old. 
This marked difference in size and growth is natural, as each kind takes a 
different length of time to go through metamorphosis. 
Figure 96. - Tadpoles. 
which they live. When away from water frogs often escape 
their enemies by their remarkable leaping ability. As the 
frog's hind legs are considered a delicacy, man is the worst 
enemy of the frog. Next come the snakes, birds, and fish. 
The leech kills frogs by sucking their blood. Fish eat many 
of the tadpoles, and, strange to say, some water beetles eat 
tadpoles also. 154 
FROGS AND THEIR WAYS OF LIVING 
As the nights in the fall grow cool, frogs make ready to 
spend the winter in a state of inactivity. During the warmer 
part of the day they may be seen sunning themselves on a 
bank, but as soon as ice forms on the water they remain on 
the bottom or buried in the mud. The lungs are emptied 
of air, the heartbeats decrease, and all the usual life processes 
take place more slowly. This habit of passing the winter in 
a state of inactivity is known as hibernation (hl-ber-na'shun). 
All the Amphibia, reptiles, and several of the mammals 
hibernate during the 
winter. 
132. The Toad. - 
While there are several 
different kinds of frogs 
in the United States, 
except in the southwest, 
there is but one kind of 
toad that is at all com- 
mon. This homely ani- 
mal is one of our best 
friends, for he lives on 
insects and slugs that 
destroy the plants in our 
gardens. He captures 
his food by throwing out a sticky tongue just as the frog does. 
One often hears the expression, " Don't touch a toad, 
you will have warts." Of course this is not true, nor is it 
true that they are found alive in solid rocks. Sometimes 
they fall into crevices and are released when the rock is 
blasted away. If they have been in this crevice-prison only 
a short time, they are often alive, but we must remember 
that they require food like all other animals and soon starve 
unless they can secure it. 
133. Life History of the Toad. - In many respects the 
toad's life history is similar to that of the frog. The eggs 
With permission of Nature Magazine. 
Figure 97. - Toad. LIFE HISTORY OF THE TOAD 
155 
of the toad are laid in stagnant water in strings of a jelly-like 
substance. (Figure 98.) The eggs hatch in from five to ten 
days into wriggling tadpoles, which feed on the microscopic 
plants that are found in water. They swim by means of 
their tails. Respiration is accomplished by means of the 
outside gills, which allow the oxygen from the water to reach 
the blood and the carbon dioxide to enter the water. Later 
the inside gills take over the work of the outside gills and the 
outside gills disappear. Still later, as lungs begin to develop, 
the tadpoles come to the surface for air, so that for a time they 
Figure 98. - Different Stages in the Life History of the Toad. 
are getting the oxygen both from the air and the water. (See 
Figure 96.) 
About this time the hind legs begin to appear, the tail 
shortens and, soon after, the front feet may be seen. By 
the first of July the tail has entirely disappeared and the 
small toad begins to hop around on the bank, having the 
form, attitude, and habits of the toad as we see him in the 
garden. From the bank they begin to travel away from the 
water and scatter over the country in all directions. After 
a rain or during a shower, thousands of them are sometimes 
found hopping along a ravine or highway. Here they are 
run over by man and beast and fed upon by crows and other 
enemies. Of the hundreds that leave the pond but very 
few ever live to be a year old. Since toads feed on a great 
variety of harmful insects they are recognized as beneficial 156 
FROGS AND THEIR WAYS OF LIVING 
animals. Although slow-moving, the toad is able to feed 
upon many flying insects, which he strikes with his quick- 
moving tongue as they rest on plants or crawl over the 
ground. 
134. Evolution. - The study of the changes through 
which the egg of the frog grows into a tadpole and then into 
Figure 99. - A Group of Fossil Animals. 
These were once abundant, but they are now extinct. 
a frog tells us much about the way frogs may have developed 
or evolved from fishes. The tadpole breathes and eats like 
a fish; but as soon as lungs and legs are formed, it 
breathes and eats like a frog. This same study of the tad- 
pole also illustrates how animals may gradually have come 
to live on land, and suggests a natural explanation for the 
origin of land vertebrates. In the early history of the earth 
there were hundreds of animals and plants which are no HEREDITY 
157 
longer known to science. The skeletons, footprints, and 
whole bodies of many of these are preserved in the rocks. 
Such remains are called fossils. 
If all the animals, or one of each kind, had been preserved 
in the rocks, it would be easy to investigate these earlier 
animals and their relation to the living animals of the present. 
But in our information there are great gaps, which we are, 
however, gradually bridging. Apparently unrelated ani- 
mals have resemblances, so that in time we may come to see 
that all animals are really 
related forms, varying 
only in complexity of 
structure. One thing 
that we must always 
keep in mind is that the 
plants and animals which 
live now are but a small 
fraction of those which 
have lived. The rocks 
have preserved the re- 
mains of only a small 
part of the forms of 
the past. Many of the 
records of extinct ani- 
mals and plants have 
been destroyed by decay and heat so that much that would 
be valuable in solving the question can never be found. 
Evolution thus means that all of fossil and modern animals 
and plants have had a continuous history. 
The study of the development of the frog also illustrates 
two other general subjects, heredity (he-red'i-ty) and the 
influence of environment (en-vi'run-ment) if reproduction is to 
be successful. 
135. Heredity. - The tendency of all young animals to 
grow and live like their parents is called heredity and may 
Figure 100. - A Fossil Leaf. 158 
FROGS AND THEIR WAYS OF LIVING 
be defined as the transmission of physical and mental traits 
from parent to offspring. There is no difficulty in recog- 
nizing the young frog as a certain kind of frog. The color 
markings on the skin are like those of the parents; it grows 
to about the same size; it eats the same kind of food, and 
lives in the same region. 
Every species of living 
thing is able to produce 
new forms like itself, and 
heredity is always at 
work when new plants 
and animals are being 
produced. Thus hered- 
ity determines that 
leaves of the right shape 
and size occur in the 
proper place or that fins 
in the fish or legs in the 
frog shall form in their 
normal position. 
A detailed statement 
of the laws of heredity is 
beyond the province of 
an elementary book, but 
it is now well established 
that certain traits of 
parent plants and animals are reproduced in their offspring 
in regular and definite amounts and proportions. This is 
more fully discussed in Part V. 
136. Environment. - This word is used in two ways. 
First, it refers to general surroundings such as temperature, 
moisture, and seasons, as they vary from year to year; and 
secondly, to immediate surroundings. The frog responds 
to the first by hibernating in the winter; while the second 
phase of environment may be illustrated as follows: the 
Note the discs at end of toes. Com- 
pare the environment of leopard frog and 
tree frog. 
Figure 101. - Tree Frog. ECONOMIC VALUE OF AMPHIBIANS 
159 
tadpole can live only in water, and if the pond dries up be- 
fore the frog stage is reached, the environment has become 
unsuited to the tadpole. This often happens when the eggs 
are laid in a temporary roadside pond which evaporates long 
before the tadpole becomes a frog. All such tadpoles die 
unless they are able to swim to some other body of water. 
The birds that are able to fly avoid hibernating in the 
winter. They are able to adapt themselves to the change 
in the seasons without burying themselves in the mud as 
the frogs do. 
Some of the birds do not migrate, but remain all winter 
in the north. They have become so well adapted to condi- 
tions that they are able to get their food where birds that mi- 
grate would starve. 
Man is the only animal that is able to live anywhere on 
the face of the earth under the most varied conditions. To 
realize this fully we have but to think of the different sur- 
roundings of the Eskimo, Indian, Bushman, and of ourselves. 
Each animal and plant is directly dependent upon its 
environment for food and a home. 
137. Economic Value of Amphibians. - The toad is the 
only member of the amphibian group that is of any great 
value to man. It destroys many insects. Frogs eat a few, 
but hardly enough to entitle them to high rank as beneficial 
animals. Their chief value is as food and as convenient 
forms for dissection in biology courses. 
OUTLINE 
Amphibians 
Defined 
Salamanders 
Frogs 
Life processes 
Food-taking 
Respiration 
Digestion 
Excretion 
Reproduction 
Irritability 
Nervous system 
Spinal cord 
Brain 
Olfactory lobes 
Cerebral hemispheres 160 
FROGS AND THEIR WA YS OF LIVING 
Mid-brain 
Optic lobes 
Cerebellum 
Medulla 
Life history 
Fertilization of egg 
Growth of tadpole 
Tadpole becomes frog 
Metamorphosis 
Habits 
Jumping 
Protection 
Swimming 
Hibernation 
Toads 
Life history 
Similar to frog 
Evolution 
Heredity 
Environment 
Economic value of amphibians 
SUMMARY 
The amphibians live both on land and in the water. The best known 
are frogs, toads, and salamanders, commonly called lizards. The frog 
is so well known that it is here taken as a type to study. It has all the 
life processes of the other animals we have studied, though of course 
these vary in the way each is carried out. The brain and nervous sys- 
tem of the frog are much more highly developed than those of the cray- 
fish. The parts of the brain are the same as in man. 
The life history of a frog begins with the eggs, which are laid in ponds 
early in the spring. After fertilization the egg develops into a tadpole, 
which gradually grows legs and loses its tail. Meanwhile complicated 
changes take place inside. Frogs have protective coloration, and in 
winter they hibernate. 
The toad has practically the same life processes and life history as the 
frog. It is of greater economic importance to man because of the large 
number of insects it eats. 
Our study of the life and development of the frog helps us to under- 
stand what the scientists call evolution. It also illustrates heredity 
and adaptability to environment. Heredity is the tendency of the 
young to be like the parents. Environment refers to the surroundings 
of life and the conditions under which animals live. 
QUESTIONS 
What are amphibians? Why are they so called? Name three 
classes. Which is the most suitable for detailed study? Which is of the 
most importance to man? How does the development of the brain of 
a frog compare with that of a crayfish? How about the nervous 
system? Describe each of the life processes of the frog. Has the QUESTIONS 
161 
brain of a frog the same parts as that of a man? Name these parts. 
How do frogs reproduce? What does the egg become? What is the 
next stage in the frog's life history? 
Does the toad have the same life processes as the frog? The same 
life history? Why are toads economically important to man? In 
what way does our study of the frog illustrate evolution? What is 
meant by heredity? By environment? 
Dickerson, The Frog Book. 
Hodge, Nature Study and Life. 
Holmes, Biology of the Frog. 
Marshall, The Frog. 
Morgan, Embryology of the Frog. 
Smallwood, Textbook of Biology. 
REFERENCES CHAPTER XII1 
But the trail of the serpent is over them all. 
- Moobe 
A GROUP OF VERTEBRATES THAT HAVE 
BECOME NEARLY EXTINCT 
138. Reptiles. - When one examines the fossils of the 
ancient group of reptiles in any of the great museums one is 
impressed by their huge size and strength. This enabled 
them to kill in combat all other kinds of animals of that 
This animal is known only through its fossil remains. Modelled from a 
restoration by C. W. Gilmore. This extinct reptile was probably 87 feet 
long and 15 to 16 feet high at the hips. One of the largest animals known 
to science. Photograph furnished by the United States National Museum 
and published with their permission. 
Figure 102. - Dinosaur. 
period and is the reason why we call the time when .these 
large animals were living the " Age of Reptiles." There 
was a time when reptiles were not only much larger than 
they are to-day but more numerous. For some reason that 
we have not been able to discover, the reptiles of this ancient 
1 If desired, this chapter may be omitted without affecting the sequence in 
the book. 
162 LIFE HISTORY 
163 
period became largely extinct. A few, however, were able 
to adapt themselves to changing conditions and their descend- 
ants are the lizards, snakes, alligators, turtles, and crocodiles 
of the present. The Reptilia (Latin, repere, to crawl) are char- 
acterized by a covering of bony plates, or scales, in the skin, 
With permission of American Museum of Natural History. 
Figure 103.- The Oldest Living Animal. 
Said to be 150 years old. 
by the absence of gills in the adult stages, and by the presence 
of lungs. 
139. Life History. - Unlike the amphibians, the reptiles 
hatch directly into their adult form, only much smaller. 
The young snake just out of the egg or the young alligator 
just hatched is recognized by its resemblance to its parents. 
There is no metamorphosis, as in the frog. The reptiles 164 
VERTEBRATES NEARLY EXTINCT 
lay their eggs in protected places and exhibit no parental 
care for the eggs or for the young. Some snakes hatch their 
young in the body of the parent and the offspring are born 
alive. 
140. Turtles. - Turtles are easily recognized by their 
outer skeleton. This skeleton is unlike the skeleton of the 
starfish or crab, or of any other group of animals. The skele- 
ton of the turtle, composed mostly of skin plates, is something 
like a box with a cover, the upper portion corresponding to 
the box itself, and the lower portion to the cover. The box 
Witn permission of Nature Magazine. 
Figure 104. - Lizard. 
does not fit closely all the way around, for there are places 
where the head, the tail, and the four legs stick out. When 
the turtle is disturbed, the legs, the head, and the tail are 
drawn inside, and the box is pulled down tightly by muscles 
to meet the cover. 
The term turtle is often applied to aquatic forms, and the 
term tortoise to those living on land. Sea turtles attain a 
length of six or eight feet and weigh sometimes as much as 
a thousand pounds. The flesh of the green turtle and of the 
terrapin (ter'ra-pin) is used for food. 
141. Lizards. - There is a great variety of lizards. A 
common lizard is the chameleon (ka-me'le-un), which has the SNAKES 
165 
power of changing the intensity of the color in the skin by 
moving the color material nearer the outer surface or draw- 
ing it away. The horned toad of the Western United States 
is a lizard with scales of varying length which give it a horny 
appearance. Horned toads, instead of laying eggs, have the 
eggs hatched while yet in the oviducts and the young horned 
toads are born alive. A poisonous lizard is the Gila (he'la) 
monster that occurs in New Mexico and Arizona. It has 
the poison glands in its lower jaw. 
142. Snakes. - Snakes are legless vertebrates with long, 
cylindrical bodies covered with scales. They move by 
means of the scales (scutes) on the under side of the body. 
Since snakes eat insects, 
frogs, mice, rats, and 
rabbits, they should be 
considered beneficial. 
Rattlesnakes1 and 
copperheads are the 
most common poisonous 
snakes of our country. 
Their jaws are provided 
with fangs (Figure 105), 
by means of which a 
poison is injected into their prey. Large snakes like the 
boa constrictor of South America, and the python (pi'thdn) 
of Asia are constrictors. They are able to wind their bodies 
around their prey and to crush it to death. The most 
deadly snake in the world is the cobra (ko'bra) of India, 
where thousands of the natives die annually from its bite. 
Snakes swallow their food whole, and as the teeth are 
used merely for holding their prey, they point backwards. 
Fear of Snakes. - In the case of many grown-up people 
there is a senseless fear of even the smallest snake. Small 
muscle 
tongue 
This shows the poison gland and its con- 
nection with the fangs which are special- 
ized teeth. 
Figure 105.- Head of Rattlesnake. 
1 The two most common rattlesnakes are the mountain rattler and the 
massasauge (m&s-sa-sa'ge). 166 
VERTEBRATES NEARLY EXTINCT 
Figure 106. - Rattlesnake - Poisonous. 
Notice the triangular shape of the head and the small pit on each side of 
the nose. Compare with Figure 110. 
children are seldom afraid of snakes until some older person 
tells them that snakes are poisonous or that they will be 
bitten if they handle them. As a matter of fact the com- 
mon snakes of the garden will not bite when carefully handled 
but rather seem to like to be handled. When one stops to 
think that snakes are cold-blooded while the hands are warm 
it is not strange that they might come to enjoy the human 
hand. Some people are so frightened when they see a snake 
that a whole day of pleas- 
ure may be spoiled on 
this account. It is un- 
wise to put fear where 
there should be none and 
it is unwise to imagine 
that a harmless snake will bite. Fear takes a toll of our 
nervous energy and if we can learn to banish senseless fear 
Figure 107. - Rattles of Rattlesnake. SNAKES 
167 
we have done something towards prolonging life and making 
our lives more efficient. 
Figure 108.-Bull Snake with Hen's Egg in Mouth. 
We need to learn about snakes enough to tell the harm- 
less ones from the poisonous ones and also enough to 
overcome our fear of the little snakes. If one does not fear 
Figure 109.- Bull Snake after Swallowing Egg. 
snakes and can handle them without minding, it is not wise 
to run after others with a snake in hand. People cannot 
be frightened out of their fears. A better way is to show 168 
VERTEBRATES NEARLY EXTINCT 
them by handling a snake gently that it will not bite and 
that it enjoys being handled. 
143. Alligators and Crocodiles. - Crocodiles are found in 
the Southern United States, South America, Africa, and 
India. Alligators are found in stagnant pools in the Southern 
With permission of Nature Magazine. 
Figure 110. -Garter Snake and Seventeen Young. 
This snake is harmless. 
United States. Crocodiles resemble alligators but have 
narrower mouths. 
144. Adaptations. - Reptiles are peculiarly adapted to 
their environment. Snakes that live in trees are some- 
times the color of leaves or bark. Some that are harmless are 
colored much like poisonous snakes. An adaptive feature 
of the crocodile is a fold of skin which shuts off the mouth 
from the throat and prevents water from entering the throat 
while the crocodile is drowning its prey. The old world chame- 
leons have their feet modified for clasping branches. In ADAPTATIONS 
169 
the case of the turtles, those that live in the sea have paddle- 
like feet for swimming, while those that live partly on land 
and partly in the water have toes with webs. Lizards are 
almost always of about the same color as their surroundings. 
With permission of New York Zoological Society. 
Figure 111. - Alligators. 
SUMMARY 
The reptiles always use lungs for breathing. They usually have 
scales or bony plates in the skin and have either two pairs of appendages 
(turtles, lizards, alligators, crocodiles) or none (snakes). It is impor- 
tant to learn to recognize poisonous reptiles, as their bite is dangerous. 
LABORATORY DIRECTIONS 
From models or preserved specimens the difference between the harm- 
ful and harmless reptiles should be worked out. The living turtle can be 
studied easily. Its special skeleton is an illustration of protective 
adaptation. Notice how the nostrils of the aquatic turtle can be closed. 
How does this help the turtle? 
QUESTIONS 
What are the most common snakes in your vicinity? Are they 
poisonous? How can you tell? Where do they live? What do they 
eat ? How many kinds of turtles do you know ? Where do they live ? 170 
VERTEBRATES NEARLY EXTINCT 
REFERENCES 
Ditmars, The Reptile Book. 
Jordan, Kellogg and Heath, Animal Studies. 
Linville and Kelly, General Zoology. 
Reese, The Alligator and Its Allies. 
Reese, Alligators as Food. CHAPTER XIII 
BIRDS 
Ye call them thieves and pillagers; but know 
They are the winged wardens of your farms, 
Who from the cornfields drive the insidious foe, 
And from your harvests keep a hundred harms; 
Even the blackest of them all, the crow, 
Renders good service as your man-at-arms, 
Crushing the beetle in his coat of mail, 
And crying havoc on the slug and snail. 
- Longfellow 
145. Classification of Birds. - Birds are usually divided 
into groups according to their structure. The shape and 
size of the beak and of the feet and wings are the charac- 
teristics most used in the general classification. This is 
illustrated by a single group of birds, the hawks, owls, and 
vultures, which are given the technical name of Raptores 
(rap-to'rez : Latin, rapere, to seize), birds of prey. The 
bird books describe the Raptores as follows : toes four, three 
in front and one behind, except in the vultures; all toes 
armed with strong, sharp, curved talons (taTimz); bill with 
a cere (ser: Latin, sera, wax) or covering of skin at its base 
through which the nostrils open, very stout and strong, the 
upper mandible tipped with a sharp-pointed hook. 
In addition to this classification by structure, which is 
essential for a careful study of birds, they are also classi- 
fied by their habits. For example, birds are divided into 
four classes based on their migratory habits. Birds like 
the downy woodpecker and English sparrow are permanent 
residents throughout their range, that is, they can be found 
171 172 
BIRDS 
within given limits at any time of year, while bobolinks 
and humming birds are summer residents, migrating south- 
ward at the end of the season. Birds like wild geese, fox 
sparrows, and the like, are transients, stopping along their 
migratory route for rest or food or to escape unfavorable 
weather; while such 
birds as the snowy owl, 
northern shrike, and 
evening grosbeak are 
winter visitants which 
migrate to us from the 
North when the cold 
becomes excessive and 
the food supply is di- 
minished. 
Birds are classified 
also by their nesting 
habits. Some birds, like 
the meadow lark and 
bobolink, nest in the 
open field, and their 
nests are made incon- 
spicuous rather than in- 
accessible ; other birds, 
like certain hawks and 
eagles, build their nests 
in tall trees, making 
them conspicuous, but 
inaccessible. Still others 
build like the oriole at the end of slender branches where 
they are out of reach of animals. Birds like the kingfisher, 
sand swallow, and puffins build their nests at the bottom of 
a burrow in the ground. 
146. Nest-building. - Birds show great variation in nest 
building. Some build a large nest with materials loosely 
Figure 112. - Shrike. 
A small bird of prey. NEST-BUILDING 
173 
put together; others build small nests of neatly woven ma- 
terial, and some birds, like cowbirds, build no nest at all, 
but lay their eggs in the nests of other birds and leave the 
work of caring for their young to the foster parents. 
Forehead 
Upper mandible 
Lower mandible /S 
Chin' 
Throat' 
,Nape of Neck 
lAnal region 
/Heel joint 
Inner Toe 
Middle Joe 
Hind Toe 
(Hallux) 
Outer Toe- 
Figure 113. - Diagram of Bird. 
The number of eggs that birds lay in their nests varies 
from one to as many as thirty or forty. The time required to 
hatch the eggs varies from ten days to six weeks. Birds 
Figure 114. - Prairie Horned Larks. 
whose eggs hatch in ten days or two weeks are called altricial 
(al-tri'shal: Latin, altrix, nurse), for such young are hatched 
helpless, blind, and with little down. Eggs that hatch in 
First spring arrivals in the North. 174 
BIRDS 
Figure 115. - Nest of Goldfinch. 
An altricial nest. 
The nest is merely a depression in the leaves with no lining. The young 
leave the nest within a few hours after hatching, so that a nest to hold the 
young would be useless. Young that leave the nest soon after hatching are 
called praecocial. 
Figure 116.--Eggs of the Woodcock. NEST-BUILDING 
175 
from three to six weeks develop well-formed young, able to 
run around within ten to twelve hours after hatching. These 
are known as praecocial (pre-ko'shal: Latin, prae, before; 
coquere, ripen). Such birds have little need for a substantial 
nest and only a few of them build one. The robin is altricial, 
and the domestic fowl prsecocial (Figures 115 and 116). 
STUDY OF BIRDS 
Study of a Living Bird 
Have a member of the class bring a canary or other caged 
bird to school for observation. Questions about the bird 
may be asked and answered by members of the class. The 
following are typical questions that may be used : 
1. How many toes has the bird ? 
2. Are these toes grouped, two in front and two behind, 
or three in front and one behind? 
3. Are the toe nails long or short? Are they used for 
taking food, for holding food, for perching, or for what? 
4. How are the feathers distributed? 
5. Where are the long feathers? The short feathers? 
6. Does the bird walk or hop ? 
7. Are the feathers evenly colored ? Examine the molted 
feathers in the cage. 
8. Examine the beak. Is it adapted for crushing seed, 
tearing flesh, catching insects, drilling, etc.? 
9. Examine the feet. Are they adapted for tearing 
flesh, scratching, wading, etc. ? 
10. Examine the eyes. Does the bird wink? 
11. Does the bird have eyelashes? Describe them, if 
any are found. 
12. Can you find a third eyelid? Describe it if found. 
13. What are the colors of the head, back, tail, breast, 
throat ? 
14. Are there any special markings, such as head bands, 176 
BIRDS 
shield spots, splashes of color, or any other striking color 
features ? 
15. How many kinds of sound does the bird make, such as 
different songs, alarm notes, call notes, etc. ? 
16. How does the bird drink? 
17. How does the bird eat? 
18. What and how much does it eat? 
19. How does the bird bathe? 
20. How does the bird " dust "? 
147. Economic Importance of Birds. - The chief food 
of some birds is insects and in this they are beneficial to man 
for they kill the insect pests that destroy the crops espe- 
cially in the South and West. Other birds, however, that 
eat the food needed by man, or that destroy the small and 
more useful birds, may be termed harmful. 
Beneficial Birds. - Birds such as quails, crows, red-winged 
blackbirds, kingbirds, shrikes, bluebirds, blue jays, pheasants, 
and many others feed on grasshoppers. Army worms which 
are harmful, almost without exception, are food for quails, 
vesper-sparrows, song-sparrows, and pheasants. The flicker 
eats ants by the thousands. Cuckoos are the enemies of 
caterpillars and canker worms. 
Among the hawks and owls are found many beneficial 
birds, for the screech owls, red-tailed hawks, red-shouldered 
hawks, together with shrikes destroy such harmful rodents 
as mice, shrews, moles, prairie dogs, woodchucks, and rab- 
bits. The hawks prey upon them during the day and at 
night the owls continue the slaughter. The shrikes feed 
upon mice to a great extent. 
Doctor A. K. Fisher gives an interesting illustration of 
the work done by a pair of owls that lived in the Smithsonian 
Institution at Washington. He found in examining the 
pellets that were scattered about their roosting place 450 
skulls of small animals, of which 250 were meadow mice. ECONOMIC IMPORTANCE OF BIRDS 
177 
Aside from their value in destroying insects, birds are 
valuable as scavengers. The buzzards and vultures of the 
South and West eat dead animals. The gulls of the sea 
This is an example of protective coloration. The pattern of the sitting 
bird blends with the surroundings so that it is difficult to see the bird as long 
as she remains quiet. Note that this bird can see directly behind her with- 
out turning her head. The eyes are placed well back in the head. This is 
an adaptive feature and serves to protect her. 
Figure 117. - Woodcock on Nest (incubating). 
and lakes destroy refuse thrown upon the water. The eagle 
eats the dead fish that float on the surface of the water, or 
small dead animals lying in the open on the land. Crows 
also eat dead fish. 178 
BIRDS 
There is a group of birds that lives largely on seed and 
these birds, for example the tree-sparrow, red polls, song- 
sparrows, juncos, pheasants, and quails, destroy tons of weed 
seed during the fall, winter, and spring. In doing this they 
have a distinct value to agriculture. 
Figure 118.--Nest of Chipping Sparrow with Cowbird's Egg. 
Harmful Birds. - Not all birds are beneficial to man. 
Some birds are beneficial a part of the year, and more or less 
harmful at other times. Whenever the taste of a bird is 
like our own, they take our foods. For example, a robin 
will eat cherries and berries which we are raising for our- 
selves. 
Some of the smaller hawks, such as the sharp-shinned 
hawk and cooper hawk, are fond of small insect-eating birds 
and the young of our domestic fowls. This classes them as 
harmful. The house (English) sparrow is likewise in bad 
repute because of its attitude towards more useful birds. NECESSITY OF BIRD PROTECTION 
179 
It uses the nesting places and even the roosting places of 
more beneficial birds and thus drives them away. In ad- 
dition, the house sparrows are noisy and generally annoying, 
but they seem to be here to stay as it is practically impossible 
to exterminate them. 
Figure 119. - Male and Female Cowbirds. 
Notice the difference in shade of the two birds. The female at the right 
is gray. What advantage would a dull color be to her while she was in the 
nest of another bird? 
148. Necessity and Methods of Bird Protection. - As 
the population increases it encroaches on the forest areas, 
waste land, and other favored nesting sites of birds. To pre- 
vent the extermination of desirable birds, we must protect 
them against the losses caused by advancing civilization. 
The available agencies for this work of conservation may 
be divided into three classes: (1) National, (2) State, and 
(3) private. 
Work of the Government. - The government of the United 
States has passed laws that have greatly aided conser- 
vation. 180 
BIRDS 
The Lacey law as amended in 1909 prevents the shipping 
of birds from a state where it is illegal to kill them. 
The Weeks-McLean law passed in 1913 gave authority to 
certain departments to extend better protection to migratory 
game birds and insect-eating birds. A closed season is pro- 
vided for ducks, geese, swans, rails, sandpipers, and others. 
Thrushes, orioles, swallows, wrens, woodpeckers are always 
protected and cannot be taken at any season. For example, 
the robin, which is a thrush, must not be killed anywhere in 
the United States under any circumstances. A state law 
making an open season on robins would be a violation of the 
federal law. 
In the case of the Weeks-McLean law there is a double 
protection, for even though it should be declared unconsti- 
tutional by a court its provisions are secured by a treaty 
between the United States, Canada, and Great Britain. 
Another aid to conservation is a section of the tariff act 
of 1919 by which " the importation of aigrettes, egret plumes 
or so-called osprey plumes and the feathers, quills, heads, 
wings, tails, skins, or parts of skins of wild birds, either raw 
or manufactured and not for scientific or educational purposes 
is hereby prohibited. This act does not apply to ostrich 
feathers or feathers or plumes of domestic fowls." 
Work of the States. - Besides the national protection 
which the birds are given each state has the power to extend 
additional protection through laws which aid in the propa- 
gation of birds. 
New York has a splendid conservation law on its books, 
known as the Bayne-Blauvelt law. This law forbids the sale 
of all native wild game birds in New York State no matter 
where they are taken. This is a distinct advance over the 
Lacy law. How ? 
Most of the states have special officers to enforce the game 
laws. 
The laws passed by the national government and the vari- John James Audubon (1780-1851), self-trained naturalist, sup- 
ported his family by drawing portraits. His father was a French 
naval officer and his mother partly Spanish. He spent a few years 
in France where he gave his main energy to music, drawing, and 
natural history during the period when he was in training for the 
navy. 
After his return to America about 1800, he became a wandering 
naturalist, ever seeking for new birds to study. As he went from 
place to place, he would pay for his lodgings or a new pair of 
shoes by making a portrait of some local celebrity or even the 
shoemaker himself. 
His most famous work consists of one thousand and sixty-five 
natural sized, colored figures of American birds, the publication 
of which alone took ten years and cost $100,000. Whenever you 
visit a large library, ask to be shown Audubon's Birds, the most 
noted book on American birds. NECESSITY OF BIRD PROTECTION 
181 
ous states have originated and have been pushed by organi- 
zations of citizens interested in conservation. 
Work of Private Organizations. - The National Associa- 
tion of Audubon Societies is one of the most energetic and 
powerful of these organizations. It was founded in 1902 
and in 1906 was endowed to the extent of $322,000. It now 
has an annual income of more than $70,000, which is ex- 
pended in education, propagation of birds, and in the pro- 
tection of various bird refuges throughout the United States. 
This organization is a monument to its founder, William 
Dutcher. 
The American Ornithologists' Union is a national organi- 
zation, composed primarily of bird students. Most of the 
ornithologists of the country are members. They study 
problems pertaining to birds, for example, their distribution, 
migration, economic importance, etc. The Auk, a quarterly 
magazine contains the latest facts and news items on birds. 
A committee from this union drafted the so-called Audubon 
law in 1886. This law legally defines game birds, gives pro- 
tection to useful non-game birds and provides for permits 
to be issued to bird students for the purpose of collecting 
birds for scientific study. It is now in force in nearly all the 
states of the Union. 
Work of Individuals. - While the government at Wash- 
ington and the various states at their capitals may pass 
conservation laws, it is public sentiment that compels their 
enforcement. In other words it goes back to the individual 
to do his part in supporting and respecting the various laws. 
Some individuals of means have purchased lands suitable 
for breeding grounds, where ample protection is afforded 
either by state officials or privately hired protectors. 
The Ward-Mcllheny Bird Preserve of 13,000 acres in 
Louisiana is an example of such an area. Here thousands 
of ducks, geese, herons, and egrets are allowed to breed and 
to feed without being disturbed in any way. 182 
BIRDS 
Marsh Island Preserve was made possible by a gift of 
$150,000 by Mrs. Russell Sage. This island is close to the 
Ward-Mcllheny Bird Preserve and gives additional protec- 
tion over a wider area. 
National Game Preserves and Bird Refuges. - Yellowstone 
National Park contains more then 2,000,000 acres. This 
is a famous game preserve and all animals are protected 
there. Glacier National Park contains over 800,000 acres. 
The Witchita National Game Preserve in Oklahoma contains 
57,000 acres. Yosem- 
ite National Park 
in California contains 
719,000 acres. No 
hunting is allowed in 
any of the parks and 
preserves. 
Throughout the 
United States includ- 
ing Alaska and various 
islands in the Atlantic 
and Pacific, there are 
more than 100 other 
bird refuges and game 
preserves. 
State Parks and Game 
Preserves. - In Pennsylvania several of the counties have 
game preserves containing 2,000 or 3,000 acres each. In New 
York State there is the large Adirondack State Park which 
contains more than 1,500,000 acres in the northern part of 
the state. In the southwestern part is located Allegheny 
State Park, which contains more than 7,000 acres. There 
is also the Palisade Park, Letchworth Park, and many 
other smaller ones scattered through the state. In Wyo- 
ming, the Teton State Preserve which adjoins the Yellowstone 
National Park contains 576,000 acres. In Louisiana there 
Figure 120 -Bluebird. RECOGNITION OF COMMON BIRDS 
183 
is a state Wild Fowl Refuge on Vermillion Bay of 13,000 
acres which joins the Warcl-Mcllheny tract. 
149. Recognition of Common Birds. - In most of the states 
of the Union, there are probably between 200 and 500 kinds of 
birds found during the year. California with its great extent 
from north to south and its varied topography offers the great- 
est variety of environments of any state in the Union. No 
doubt, it leads in the num- 
bers of birds found there. 
More than 500 have been 
identified in this state. In 
New York State not more 
than half that number 
have been recorded. 
We may select from 
these large lists certain 
representative birds for 
study. 
Bluebird. The bluebird 
is found in yards, on the 
roadsides, and in second- 
growth woods throughout 
the greater part of the 
United States. It is about 
seven inches long. The 
upper part of the male, in- 
cluding wings and tail, is 
bright blue. The breast and throat are cinnamon color. The 
female is grayish blue above and paler than the male below. 
This bird nests in holes in trees and fence posts and is readily 
attracted by nesting boxes put up in orchards and woods. Its 
food consists of caterpillars, grasshoppers, crickets, and, in cold 
weather, of some flying insects that are benumbed by the cold. 
The Catbird is nearly nine inches long and of a slate-gray 
color. The crown and tail are black. This bird is friendly 
Figure 121. - Catbird. 184 
BIRDS 
and builds its nest near human habitations quite as often as 
in the woods. Catbirds are merely summer residents in 
the North, arriving latest in the spring and leaving earliest 
in the fall. They devour large numbers of insects and some- 
times take berries and cherries. This privilege they have 
earned by their services in destroying insects. They are 
fine musicians and clever mimics, and are often called the 
mocking birds of the North. 
The Crow. " Black as a crow " is sufficiently accurate 
for a color description. Crows have bluish and purplish 
With permission of Nature Magazine. 
Figure 122. - Crow Feeding on Fish and Corn. 
lights on their black feathers. A mature crow is nearly twenty 
inches long. They are usually classed as permanent residents 
in the Northern States. It is quite likely however, that the 
crows that nest in Northern States go South in the winter 
and their places are taken by winter visitants from Canada. 
These winter crows usually roost together in rookeries where 
thousands are sometimes seen. They live in the deep woods, 
roadsides, orchards, and parks. They feed upon grass- RECOGNITION OF COMMON BIRDS 
185 
hoppers and other insects, and young birds. They have been 
known to eat the eggs of some of our valuable song birds. 
The crow, therefore, is partly 
helpful and partly harmful. 
The Chickadee is only 5| 
inches long but its great ac- 
tivity makes it valuable out 
of proportion to its size. It 
eats the eggs, larvae, the 
pupae, and the adults of a 
long list of insects. Being 
a permanent resident within 
its range, it does most ef- 
fective work every month of 
the year. The bird is attrac- 
tively marked with black 
and white. The top of the 
head has a black cap. It comes to the yards and or- 
chards freely in the winter time where its spirited notes 
of 11 Chickadee-dee- 
dee-dee " make it a 
conspicuous visitor. 
It nests in a hole of a 
tree or stump and 
sometimes in a nesting 
box. 
The Baltimore Oriole 
is about 7| inches long 
and is very noticeable 
because of its plumage. 
The colors are black 
and orange, striking in 
the male but duller in 
the female. The head, neck, and back are black while the 
lower back and under parts are rich orange. The tail is 
Figure 123. - Chickadee. 
Figure 124. - Baltimore Oriole. 186 
BIRDS 
orange and black. The bird is almost wholly limited to road- 
sides, villages, and parks where it builds substantial hanging 
nests from the branches of elms and maples. It feeds 
mainly on caterpillars 
but eats other insects, 
now and then taking 
cherries. It is a welcome 
summer resident in the 
Northern States. 
Robins are rather large 
birds, 10 inches in length 
and rated as summer 
residents in the North. 
A few remain over the 
winter in favorable locations and probably are the so-called 
early arrivals reported in the spring. Robins are black, 
gray, and white in color. In the male the top of the head is 
black. Above and below the eye are white spots. The 
tail is dark with the 
tips of the outer tail 
feathers white. The 
females are of lighter 
color. Robins are 
found widely scattered 
in yards and orchards, 
along the roadside, in 
the parks, and the 
second-growth woods. 
Usually two broods 
are raised each season. 
They feed upon cater- 
pillars, crickets, and 
other insects. They also eat earthworms. In some regions 
they are unpopular because they eat the smaller fruits but 
this damage they more than pay for by destroying insects. 
Figure 125. - Robin. 
Figure 126. - House Sparrow. RECOGNITION OF COMMON BIRDS 
187 
The House (English) Sparrow like its European cousin, 
the Starling, is an imported product, brought over from 
England about 1851 for the purpose of destroying certain 
insects. It has now spread to the Pacific coast. There is 
reason to believe that in time the bird will become a valuable 
addition to our bird life. It now feeds on many weed seeds 
and destroys such insects as the cut worms, tussock moths, 
Photograph by Dr. G. S. Britton. 
Figure 127. - Downy Woodpecker and Song Sparrow. 
some weevils, cabbage worms, and white grubs. The male 
has a gray crown while the back is streaked with black and 
chestnut. A part of the throat and breast is black while 
the under parts are whitish. The bird is a little more than 
6 inches long. The chief fault found with this bird is that 
it uses the nesting sites of other more desirable birds and as 
a result these exiled birds are driven away. 
The Downy Woodpecker is the best known and the smallest 
of all woodpeckers in the United States. The principal 188 
BIRDS 
markings are in black and white. The adult male has a 
scarlet band on the nape of the neck while the female lacks 
this mark. The under parts are white and there is a white 
stripe above the eye and another below it. In the winter 
season the downy woodpecker becomes a frequenter of our 
orchards and yards cleaning the trees of insects. He is 
also often found in the woods. Being a permanent resident, 
he renders a 365-day 
service. Every day in 
the year he must pro- 
cure food enough to 
support his active body 
and by so doing he 
renders an important 
service to us. Some 
one has remarked that 
each of these birds is 
worth $10, measured 
by the good they do. 
The Song Sparrow is 
a permanent resident 
in the Northern states. 
It is widely distributed 
in North America and 
shows great variation in 
color and size through- 
out the continent. It 
is usually a little more than 6 inches long and is a valuable 
bird because it destroys weed seeds and various insects. It 
keeps to the lower levels and frequents brush lands, hedges, 
and marshes. Occasionally it nests in holes of trees. More 
frequently, however, it nests in the grass or shrubs along 
ravines, brooks, hedgerows, and open fields. It is generally 
gray and brown in color. Its breast has wedge-shaped 
streaks of black and brown with a large blotch in the center. 
Figure 128. - Barn Swallow. RECOGNITION OF COMMON BIRDS 
189 
The Barn Swallow is nearly 7 inches long. Its food is ex- 
clusively flying insects which it gets close to the ground. 
Unlike other fliers it seems to skim the ponds and roadways 
for its main supply of food. It is known to feed on grass- 
hoppers, flies, gnats, and mosquitoes. The lower parts are 
chestnut color and the upper part steel blue. The tail is 
deeply forked. This is a summer resident and its stay in 
the North is brief. The 
nest which is made of 
mud and lined with 
feathers, is usually placed 
on the rafters of old 
barns, sheds, or grana- 
ries. 
The Flicker is a large 
woodpecker about 12 
inches long and is classed 
as a summer resident in 
the North. Equally at 
home in the woods or on 
the lawns, it has come 
to have a wide circle 
of acquaintances. No 
other bird has so many 
aliases. More than a 
hundred other names 
have been given it, of 
which the commonest are yellow hammer, yarup, and 
golden-winged woodpecker. Its colors are striking. There 
is a scarlet band across the neck and a black crescent on its 
breast. The under parts are white, thickly spotted with 
black. The upper parts are gray barred with black. Its 
food consists largely of ants but it feeds also on wood borers, 
like other woodpeckers. As many as 3,000 ants have been 
found in the stomach of one flicker. 
Fl GU RE 129. Fu CKER. 190 
BIRDS 
The Goldfinch is a permanent resident that is seldom seen 
in the winter. The bird is about 5 inches long and its strik- 
ing colors of gold and black make the male- conspicuous as 
he feeds in gardens and lawns. The brilliant dress of summer 
is lost in the winter time and the duller colors that succeed 
it make the bird less easily recognized. Another reason 
for their being seldom seen in the winter is that these birds 
go in flocks and keep to the swamps and woodlands. Nest 
building is delayed un- 
til June or July in the 
North. The principal 
foods of goldfinches 
are seeds of thistles, 
dandelions, and wild 
sunflowers. They also 
eat the seeds of culti- 
vated sunflowers. 
The Phoebe is due 
in the Northern States 
when the pussy-wil- 
lows show their fuzzy 
blossoms. This sum- 
mer resident is dull 
colored and its note is 
all that gives it fame. 
The colors are grayish brown above and white or yellowish 
below. It bears distinct wing bars. Now and then conserva- 
tive individuals build nests on ledges and overhanging banks 
but for the most part their nests are built on man-made 
structures such as houses, barns, sheds, bridges, trestles, and 
viaducts. The phoebe is a fly catcher and for this reason 
man needs to encourage its presence. Among the insects it 
catches may be mentioned the click beetles, weevils, and 
numerous kinds of flies and moths. The nests are frequently 
overrun with lice to such an extent that the young are killed, 
Figure 130 -Phoebe. RECOGNITION OF COMMON BIRDS 
191 
The Herring Gull is a water bird. It nests on islands 
and the shore of the mainland and gets its food largely 
from the water. Our inland streams and lakes are frequented 
in certain seasons by these birds. As its name indicates it 
feeds on fish but it is not limited to that diet. Gulls are 
scavengers and they are found in large numbers near garbage 
dumps. In the lower harbor of New York Bay, gulls follow 
Figure 131.- Herring Gulls. 
the scows which are carrying garbage. Mr. Frank M. Chap- 
lin estimates the number he saw here at one time as three 
hundred thousand. The herring gull is 24 inches long. The 
colors of the male in summer are deep pearl gray and white 
with spots of black. In winter, the male has many spots of 
gray. 
The Screech Owl is one of our smallest owls having a length 
of only 9| inches. The bird has two color phases, a rufous 
and a gray. In the former phase the colors are rufous above 192 
BIRDS 
with streaks of black and white below. In the gray phase 
the rufous is replaced by gray. These color phases do not 
depend on age, sex, or season. There are many gradations 
between the two phases. Screech owls are permanent resi- 
dents and mostly beneficial as they feed largely on mice and 
insects. They sometimes eat earthworms. During the day 
they rest in hollow trees, 
conifers, old buildings, 
and caves. They also 
nest in hollow trees or 
bird boxes. 
The Yellow Warbler is 
one of our smallest war- 
blers and measures about 
5 inches in length. The 
male is greenish yellow 
above and bright yel- 
low beneath. The lower 
parts are streaked with 
rufous. It courts man's 
company and keeps well 
to the yards, gardens, 
and roadsides. The nest 
is compactly built of fine 
grass and fibers and lined 
with plant down or hair. 
It is a summer resident. This bird is frequently victimized 
by the parasitic cowbird. The eggs of the cowbird are 
sometimes buried beneath another nest which the yellow 
warbler builds in an effort to avoid hatching a cowbird's egg. 
Wrens. - There are some 150 kinds of wrens known to 
science. These are found mostly in the tropics, only about 
one dozen species occurring in the United States. They 
frequent stubby growths and bushes. The house wren is 
5 inches long. The upper part is brownish, the back gener- 
Figure 132. - Screech Owl. ADAPTATIONS OF BIRDS 
193 
ally has indistinct bars, the wings and tail are finely barred, 
and the under parts of the body are whitish with numerous 
blackish bars on the sides. It breeds as far north as 
Manitoba and winters in the South. In our climate they are 
nearly always found around dwellings and when they become 
attached to a nest return year after year. They are one 
of the friendliest birds and most easy to attract to our homes. 
150. Adaptations 
of Birds. - The front 
legs of birds are 
modified into wings. 
Among some birds, 
like the penguins 
(pen'gwinz) of the 
Antarctic region, the 
wings are not used 
for flying but to as- 
sist in swimming. In 
others, like the eagles 
and condors, the ex- 
panse of the wings 
is sufficient to enable 
them to fly away 
with young lambs 
and large fish. Be- 
tween the small 
wings of the penguin 
and the expanse of the wings of the eagle and condor there 
are many variations. 
Bird wings are adapted to the needs of their owners. 
Sailing birds, like the gulls, have long, slender wings, while 
ground birds, like the partridge and pheasant, have short 
wings capable of rapid, short flights. Those birds that make 
the most use of wings have them best developed. An 
example of underdevelopment, which has been increased by 
Photograph by Dr. G. S. Britton. 
Figure 133. - Yellow Warbler. 194 
BIRDS 
domestication, is seen 
in the domestic fowl, 
a ground bird, which 
makes little use of its 
flying powers, and is 
incapable of sustained 
flight. 
The legs of birds also 
have many variations. 
In the case of the eagles, 
hawks, and owls there 
are powerful claws for 
seizing and holding prey, 
while ducks and geese 
have long and webbed 
toes, adapted to swim- 
ming. Seed-eating birds 
have weak toes which 
serve merely for perch- 
ing. Chimney swifts, 
that spend most of their 
time in flight searching for food, have well developed wings, 
and feet used for clinging. Study Figure 137. 
The beaks of birds show great variation and adaptation 
for defense and food- 
getting. Hawks, owls, 
and eagles have the 
upper jaw curved over, 
hooked, and adapted for 
tearing their food; her- 
ons and bitterns have 
the beak modified into a 
long, pointed weapon of 
offense and defense; 
grosbeaks (grbs'beks) 
With permission of Nature Magazine. 
Figure 134. - House Wren. 
Figure 135. - Kingfisher. 
A fish-eating bird. ADAPTATIONS OF BIRDS 
195 
and finches have a short, stout beak for crushing seeds and 
other hard foods; while humming birds have a long, slender 
beak which in some kinds is curved so that they may reach 
the bottom of certain 
flowers. Study Figures 
118, 129, 135, and 138. 
The birds show a num- 
ber of other interesting 
adaptations which are of 
use to them. These are 
hollow bones, a keeled 
sternum (breastbone), 
and a high body tem- 
perature. 
The skeleton of a bird 
shows a prominent ridge on the breastbone. This is the 
keel of the sternum, which serves as a place of attachment 
for the large wing muscles 
(Figure 139). The lungs 
of the bird are small, but 
air tubes extend into the 
bones, so that the body 
of the bird is relatively 
lighter than that of animals 
with solid bones. 
Birds lead an active life, 
which means that they use 
a great deal of energy. 
This energy comes from 
the oxidation going on in 
the body. In birds, oxida- 
tion is more rapid than in 
other vertebrates, owing to 
the fact that they almost 
completely change the air 
Figure 136. - Junco. 
.A seed-eating bird. 
A, Ostrich s foot adapted for run- 
ning; B, ducks foot - adapted for 
swimming; C, hen's foot - adapted for 
scratching; D, plover's foot - adapted 
for wading; E hawks foot adapted 
for tearing; F, crows foot -adapted 
for perching; G, woodpecker's foot- 
adapted for climbing. 
Figure 137. - Birds' Feet. 196 
BIRDS 
with each breathing movement and thus secure a greater 
supply of oxygen. The rapid oxidation requires that a large 
supply of food be digested and assimilated rapidly and it 
makes the normal body 
temperature of birds 
higher than that of other 
vertebrates. 
Plumage. - Birds are 
the only vertebrates hav- 
ing feathers, and their 
plumage shows great 
variety in form and 
color. In some species 
there are certain colors 
which always predomi- 
nate on the males, while 
the females have little color; in other species it is hard to 
distinguish between the sexes. The brilliantly colored males 
are supposed to attract the females at the mating season, 
while the dull-colored females are in- 
conspicuous and less likely to be at- 
tacked by enemies while hatching their 
eggs, or caring for their young. We may 
say, therefore, that they are protectively 
colored. The color of birds varies during 
the first two or three years of life. 
151. Migration of Birds. - Many 
strange ideas have been entertained about 
bird migration. At one time it was 
thought that some birds migrated to the 
moon. Some thought that one kind of 
bird changed into another kind. The 
European cuckoo was said to change into a hawk. Swal- 
lows and swifts were thought to go into the mud with the 
frog to pass the winter. In recent years more attention 
Figure 138 - Rose-breasted Grosbeak. 
Figure 139. - Skele- 
ton of a Mallard 
Duck. MIGRATION OF BIRDS 
197 
has been paid to this subject. Records have been kept, 
and the bird students of different continents have compared 
their discoveries. At the present time the movements of 
practically all of our birds are known. Some of the flights 
that our birds make are almost beyond belief. For example, 
the golden plover, which nests on the shores of the Arctic 
Ocean, winters in Argen- 
tina, 8,000 miles away. 
The Arctic tern may travel 
11,000 miles between its 
winter and summer 
homes. The black poll 
warbler flys 7,000 miles 
to the place where it rears 
its young. The Baltimore 
oriole winters in Central 
America, while the bobo- 
link winters in Brazil. 
The red-eyed vireo and 
kingbird spend the winter 
in Bolivia, and the yellow 
warbler in Peru. At least 
one of our North Ameri- 
can birds, the wheatear, 
which nests in the Arctic 
regions, passes the winter 
in West Africa, migrating 
through the British Isles. 
The recent studies of 
starlings are very sugges- 
tive in explaining a possible origin of the migration habit in 
birds. The English starlings of the Northern States, after 
more than 30 years of residence, have finally learned to mi- 
grate. Huge flocks of these birds now go South in the fall, 
and return with the coming spring. They may truly be said 
Photographed by Abril Cahn. 
Figure 140. - Young Pelican. 
A fish-eating bird. 198 
BIRDS 
Figure 141. - Canadian Wild Geese. 
Photographed while migrating to their northern breeding grounds. 
to have been naturalized. Until recently, through sheer 
ignorance, they have had to adapt themselves to a climate 
wholly unnatural in its 
severity, for at home in 
northern Europe the 
species migrates regu- 
larly to southern Europe, 
and even to northern 
Africa, it is said. 
Many of them have 
managed ordinarily to 
survive even the rigors 
of the New England 
winter, but only because 
they possessed much re- 
sourcefulness in snatch- 
ing a living under most 
adverse circumstances. 
Many of them are still 
ignorant of the milder 
Figure 142. - Ring-necked Plover. 
Seen in New York State only during 
May and August. MIGRATION OF BIRDS 
199 
climate southward, in a land where food is plenty, and per- 
sist in making their night winter quarters in the belfries of 
the steeples of cities and towns or more rarely in a country 
barn. 
The starling has been a resident of the United States since 
about 1890, when half a hundred of them were released in 
Photographed by Abril Cahn. 
Figure 143. - Pelican Feeding Young. 
Central Park, New York. They multiplied rapidly, and 
drifted into the surrounding country, and, as years passed, 
spread farther and farther into the country, until now they 
are common all through the East and the Central States. 
Their first knowledge of migration, ornithologists believe, 200 
BIRDS 
probably came from their contact with the flocks of black- 
birds and bronze and purple grackles, with which latter 
species they are confused by many people, though they are 
easily distinguished by their yellow bills. They mingled 
with flocks of these and other species, and doubtless began 
to drift southward with them in the fall and back again in 
the spring. 
Photographed by Parke Struthers. 
Figure 144. -Common Booby, Young and Adult. 
A fish-eating tropical sea bird which nests in isolated islands. 
How Do Birds Find Their Way? - The long distances 
that birds fly, the unerring course they follow, and the regu- 
larity of their appearance - all lead us to ask: How is it 
done? 
The senses of birds are like our own. They see, they 
feel, they hear, they smell and taste. But these senses do 
not seem adequate to account for all they do. METHODS OF ATTRACTING BIRDS 
201 
In theory, we assume that it must be done by other senses 
than those we have mentioned. They must have an un- 
usual sense of direction and the instinct known as the hom- 
ing instinct developed to a high degree. 
At certain seasons of the year an impulse from within 
arouses the homing instinct and they start for the place 
where they were hatched and reared. It may be east, or 
west or in the tropics. It may be north, northeast, north- 
west, or south. In addition they are guided by a sense of 
direction. 
Experiments have been performed by Professor Watson 
of the Johns Hopkins University which prove that birds 
have this sense of direction to a remarkable degree. 
152. Methods of Attracting Birds. - For the purpose of 
study and of appreciation, it is advantageous to bring the 
birds near the windows of a home, where we may look upon 
them at odd times and study them at close range. There 
are several ways of getting the birds to come near a building. 
A common method is by feeding them. Foods such as suet, 
bread crumbs, hemp, canary seed, sunflower seeds, and raisins 
are attractive to birds. They should be so placed that cats 
cannot strike down the birds while they are feeding. Unless 
some care is exercised in selecting these feeding places, the 
birds will be lured into the claws of the ever waiting cat. 
Suet may be placed on the side of a tree trunk three or 
four feet from the ground in a wire loop or in a hole bored 
in the tree. Bird seed and crumbs may be placed on the 
ground, but a better method is to put the seeds and crumbs 
in a box, with a cover a few inches above to keep out the 
snow. This box should be placed on a post or on the side 
of a tree trunk a few feet from the ground. Food placed 
on the ground is likely to be eaten by stray dogs or cats, 
and in the winter time it will be buried by the snow. Sun- 
flower heads may be hung from the sides of a tree trunk or 
put on the end of a post. 202 
BIRDS 
During the winter the chickadee, white-breasted nuthatch, 
downy woodpecker, hairy woodpecker, red-headed wood- 
pecker, brown creeper, flicker, and many other birds may 
come to the suet. Juncos, tree-sparrows, house-sparrows, 
pheasants, crossbills, evening grosbeaks, song-sparrows, and 
prairie horned larks will come to the bird seed and crumbs. 
Sunflower seeds will attract chickadees, house-sparrows, 
crossbills, goldfinches, and evening grosbeaks. 
Figure 145. - Bird Photography. 
A photographic outfit for taking pictures of birds. 
Nesting Boxes. - The putting up of nesting boxes in 
the yards is another way of attracting birds. In locating 
these nesting boxes it is essential to success that the place 
selected should be safe from cats. Cats will climb to the 
boxes if they can and strike the birds as they leave the nest. 
When birds are given a choice between several boxes put 
up in a small area, they seem to select those that afford them 
the best protection from their enemies. Boxes put up on 
the ends of posts and away from trees seem to be preferred 
to those put up in the trees. Poles and posts may be covered 
with tin or sheet iron to keep the cat from climbing them. 
The size of the opening and the inside space determine 
what birds will be likely to use the boxes. The table at 
the end of this chapter (see page 204) will give an idea BIRD BATHS 
203 
of the size of the opening 
and the cavity and loca- 
tions that are considered 
proper for some of our 
town birds. 
Bird Baths. - During 
the dry weather of July 
and August, the supply 
of water is greatly re- 
duced. Sometimes the 
water that is available is 
in a place where the birds 
have no chance of escap- 
ing a cat that is lying in 
wait for them. A shallow 
plate of water placed on 
a stump or post in the 
shade is frequently used 
by the birds. Sometimes 
a dozen or more kinds of 
birds will come to these 
drinking places. At one 
such bath the following 
birds came during one 
summer: robin, oriole, 
catbird, yellow warbler, 
song-sparrow, pewee (to 
catch insects at the 
water), red-headed wood- 
pecker, black-throated 
blue warbler, and gold- 
finch. Birds will bathe 
in drinking fountains if 
they are shallow enough 
to allow them to wade. 
Figure 146. - Nest of the Yellow 
Warbler in Which a Cowbird's Egg 
Has Been Laid. 
The warbler first built the nest at the 
bottom. When this nest received a cow- 
bird egg, a second nest was built on top. 
Again it was visited by a cowb'rd and a 
third nest was made. When the cowbird 
egg hatches, the young is larger and grows 
faster than the small warblers. After a 
time this large bird crowds the small 
warblers out of the nest and they die. 
What should you do when you find an 
egg of a cowbird in a warbler's nest ? 
From Zoological Museum, University of 
Minnesota. 204 
BIRDS 
153. Public Museums. - As man came to occupy the 
land, the forests were cleared away and the ground used 
to produce food for man and domestic animals. This 
tended to drive the wild life, native to such regions, into 
the mountain fastnesses, where they were free to live. 
This resulted in many of them becoming extinct even when 
they were of great use to man. The bison and brook-trout 
are two good examples (Figure 85). The expense of collect- 
ing and properly housing the preserved skins and skeletons 
of such animals is beyond the means of most people. The 
public museum is the proper place for all such collections, 
as it is much better to have a few specimens which can be 
seen by all than to have many specimens in private col- 
lections. The men in charge of museums never indulge in 
useless slaughter, as is so frequently done by hunters. 
Every student in such a course as this should plan to visit 
the public museum or zoological park or botanical garden in 
his city as the different parts of the course are taken up. 
Pictures and drawings can never take the place of seeing the 
actual specimens. Going to the museum is like going into 
the laboratory for first-hand study of the facts. It is study- 
ing nature as she is. 
TABLE -SIZE OF NESTING BOXES 
Bird 
Diameter of 
Opening 
Size of 
Cavity 
Location 
Chickadee 
h" 
4X4 
In protected spots 
House wren .... 
it" 
4X4 
Trees and arbors 
Nuthatch 
u" 
5X6 
On buildings or trees 
Bluebird 
u" 
5X6 
On buildings or trees 
Tree-swallows . . . 
u" 
5X6 
In trees near ponds 
Red-headed woodpecker 
2J" 
6X7 
On posts or trees 
Flicker 
3" 
6X8 
On posts or trees 
Wood-duck .... 
6" 
10 X 18 
Trees or stumps OUTLINE 
205 
OUTLINE 
Classification of birds 
By structure 
Raptores 
By migratory habits 
Wild geese 
By nesting habits 
In fields 
Meadow lark 
In trees 
Hawks 
Orioles 
In sand 
Kingfisher 
Nests: Building 
Altricial 
Robin 
Precocial 
Domestic fowl 
Economic importance 
Beneficial 
Quail 
Bluebirds 
Harmful 
Cooper hawk 
House sparrow 
Bird protection 
Federal government 
National preserves 
State government 
State parks 
Private organization 
Individuals 
Recognition of common birds 
Bluebird 
Catbird 
Crow 
Chickadee 
Oriole 
Robin 
Sparrow 
Downy woodpecker 
Song sparrow 
Barn swallow 
Flicker 
Goldfinch 
Phoebe 
Herring gull 
Screech owl 
Yellow warbler 
Wren 
Adaptation of birds 
Wings 
Penguin 
Gull 
Pheasant 
Legs and feet 
For seizing 
For perching 
Beaks 
Curved for tearing 
Sharp for pecking 
Stout for crushing 
Breastbone 
For attaching wings 
Plumage 
Males brilliant 
Females protected by color 
Migration of birds 
Distances traveled 
Golden plover 
Arctic tern 
Starling 
Sense of direction 
Attracting birds 
Feeding 
Nesting boxes 
Bird baths 
Public museums 206 
BIRDS 
SUMMARY 
Birds are classified according to their structure and also according 
to their migratory and nesting habits. They are of enormous economic 
value, chiefly because of the large number of insects they destroy. For 
this reason the government protects them and they are also taken care 
of by private organizations and individuals. Bird study is a fascinat- 
ing subject and a great deal of pleasure may be derived from the ability 
to recognize common birds. 
Birds are peculiarly adapted to the work they have to do. Their 
wings, legs, feet and beaks vary according to their mode of life and the 
kinds of food they live on. The brilliant plumage of the male is sup- 
posed to attract the female during the mating season, while the duller 
feathers of the female afford protective coloration, when nesting and 
caring for the young. 
Birds migrate with the seasons, sometimes going thousands of miles. 
Some winter with us, spending the summer farther north. Others are 
here in the summer and go south for the winter. It is pleasant to get 
them to stay with us, for they are delightful companions. This may 
be done chiefly by feeding, and also by putting up nesting boxes and 
arranging bird baths. 
QUESTIONS 
In what ways are birds classified? How are they economically im- 
portant to man? In what ways and by what agencies are they pro- 
tected? How many common birds can you recognize by sight? 
Name them. What are the different adaptations of birds? For what 
purposes is the beak used? The claw? The wings of a penguin? 
What are the advantages and disadvantages of the plumage of the 
average male bird? Of the female? Why do birds migrate? What 
birds go north in summer? Which ones go south in winter? Do you 
know any that spend the year here? What summer bird do you 
usually see earliest in the spring ? What are the best ways of attracting 
birds? Have you ever tried any of them? CHAPTER XIV 
MAMMALS, THE PRESENT RULERS OF THE 
UNIVERSE 
A righteous man regardeth the life of his beast. 
- Proverbs, XII, 10 
154. Mammals Defined. - When the great reptile animals 
became extinct in late geological history, the hairy-coated 
animals took their place as rulers of the animal world. This 
place they have main- 
tained because they have 
the best developed brains 
of all animals. They are 
warm-blooded (the body 
temperature remaining 
the same in winter and 
in summer), breathe by 
means of lungs, give birth 
to young, and are pro- 
vided with milk glands 
(mamma, hence the word 
mammal) to suckle thei 
young. Mammals are 
covered with hair wholly or in part at some period of their 
lives. A muscular wall (diaphragm) subdivides the body 
cavity into two parts. The anterior contains the four- 
chambered heart and lungs and the posterior contains the 
stomach, intestines, liver, and other organs. At birth the 
young resemble the parent in having the same parts. 
Figure 147. - Skeleton of a Dog. 
207 208 
MAMMALS 
All the animals that you have studied in this course were 
able to live because they secured food which nourished their 
bodies, exercised the function of respiration, excreted waste, 
were adapted to their environment, and reproduced their 
kind. You have be- 
come so familiar with 
these life functions that 
it is necessary only to 
say that they apply in 
the same way to mam- 
mals. 
155. Kinds of Mam- 
mals. - There are some 
800 different kinds of 
mammals in New York 
State, but even this large 
number does not repre- 
sent all of the larger 
groups. The following- 
classification gives you 
a general idea of most 
kinds of mammals, 
to which the names 
"beasts," "quadru- 
peds," " animals," are 
commonly applied. This 
list is for reference and 
need not be memorized. 
1. Pouched mammals (Marsupials), Kangaroo, opossum. 
2. Insect-eating mammals (Insectivora), Hedgehog, mole, 
shrew. 
3. Flesh-eating mammals (Carnivora), Cat, dog, civet, 
mink, raccoon, bear, seal. 
4. Toothless mammals (Edentata), Sloth, anteater, 
antbear. 
Photographed by courtesy of E.N. Sanborn. 
Figure 148. - Giraffe. KINDS OF MAMMALS 
209 
5. Gnawing mammals (Rodenha), Rabbit, squirrel, rat, 
porcupine, mouse. 
6. Hoofed mammals (Ungulata), Cattle, deer, giraffe, 
horse. 
7. Trunk mammals (Proboscidia), Elephant. 
8. Flying mammals (Chiroptera), Bat. 
9. Mammals adapted to marine life (Cetacea), Whale. 
10. Mammals with 
nails (Primates), Lemur, 
monkey, ape, man. 
In the following para- 
graphs the four large 
orders, Carnivora, Ro- 
dents, Ungulates, and 
Primates are discussed 
in some detail. 
Carnivora. -The term 
Carnivora means " flesh- 
eating "; in this order 
we find the canine teeth 
well developed and the 
jaws strong. The feet 
are usually provided with 
claws which may be 
withdrawn, as in cats, or 
which cannot be with- 
drawn, as in the dog 
family. There are the 
aquatic carnivora, sea- 
lion, walrus, seal; and 
the land carnivora, which in turn are divided into three 
well-known groups: (1) bear and raccoon which walk flat- 
footed ; (2) coyote, wolf, tiger, lion, hyena, cat, dog, etc., 
which walk on their toes only; (3) weasel, otter, skunk, 
and mink that walk partly on the toes. 
A nocturnal rodent that is seen moving 
the wire that set off a flash light and 
snapped the camera. 
Figure 149. - Deer Mouse. 210 
MAMMALS 
Rodents. - 1 he Rodents are the gnawing mammals which 
have the incisor teeth chisel-shaped and much enlarged. 
These gnawing teeth of the rodents keep growing so that 
they are not worn out and they also keep sharp because the 
front edge is harder than the back. Rodents lack the canine 
teeth of the carnivora. It is only necessary to name the 
more common members of this order to realize how very 
destructive the rodents are, for here are included the rat, 
mouse, rabbit, porcupine, chipmunk, squirrel, beaver, and 
woodchuck. 
Ungulates. - The Ungulates, commonly known as the 
hoofed mammals, live on vegetables and thus have the molars, 
their back teeth, adapted 
for grinding. Hoofs pro- 
tect the feet, while the 
whole limb is specialized 
for swift locomotion. 
They are divided into 
two groups, according to 
whether they have an 
even or odd number of 
toes. 
1. Odd-toed; horse, tapir, rhinoceros. 
2. Even-toed; 
(a) the non-ruminants, hippopotamus, pig. 
(6) the ruminants, deer, sheep, cow, etc. 
The term ruminant refers to the habit of chewing the 
" cud," which really means that the food, hastily swallowed, 
is forced again into the mouth and thoroughly chewed. Such 
animals have a specialized stomach (Figure 150). 
Primates. - The Primates represent a distinct group of 
mammals with the brain especially well developed. This is 
the main reason why we think of the animals in this group 
as the highest mammals. The lemurs and monkeys are 
mostly tree-inhabiting animals, with nails in the place of 
/Psalterium 
Oesophagus 
Rumen 
\ AbomasumReticulum 
intestine ' 
Figure 150. -Stomach of Sheep. SPECIAL ADAPTATIONS 
211 
claws on the fingers and toes. The body is completely hairy. 
Fore-feet are grasping hands as a rule, and the hind-feet walk- 
ing as well as grasping. 
Our chief interest is in the generally ac- 
cepted conclusion that this is the place 
where man as an animal should be classed. 
In the refinements of classification man is 
placed in a distinct family, the Hominidos. 
Here are grouped the interesting extinct 
races of men as well as all modern races. 
156. Special Adaptations. - Most mam- 
mals have two pairs of limbs; the fore- 
limb may be variously modified for different 
uses, as for walking in animals like the 
horse, for climbing and for food-getting in 
the squirrel, for burrowing and for locomo- 
tion in the moles, for flying in the bats, 
and for swimming in the seals. In all fore- 
limbs of mammals even those as different as 
the leg of the squirrel, the flipper of the whale and seal, and 
the wing of the bat, the arrangement of the bones is the same. 
The hind-legs of 
mammals do not show 
so much variation as 
the fore-limbs, but in 
some cases, as in the 
whale, the hind-legs 
have almost disap- 
peared through disuse 
and there is no exter- 
nal evidence of them. 
Some animals, like the 
bears, walk on the soles 
of their feet, and some, 
like the cats and the 
Figure 151. - Fore- 
arm and Hand of 
Mole. 
Permission of Nature Magazine. 
Figure 152. - Mole. 
Notice how short the legs -are and the large 
size of the " hand " adapted for digging. 212 
MAMMALS 
dogs, walk on their toes only. In some animals there is a 
variation in the number of the toes; for example, the cow 
walks on two toes, the horse on one toe, the hoof being a 
modified toe nail. In such cases the other toes are entirely 
lacking or rudimentary (not perfectly de- 
veloped). 
The skeleton of mammals is built on a 
similar pattern in all cases. Even ap- 
parently marked differences are found, on 
examination, to be only modifications of 
similar parts. In the vertebral column 
(Figure 147) there are several regions, such 
as neck, rib, back, hip, and tail. It happens that the 
number of the separate vertebrae in the neck region is the 
same in the dog, horse, mouse, giraffe, bat, man, etc., but 
Figure 153. - Arm 
(Wing) of Bat. 
American Museum of Natural History, New York. 
Figure 154. - Flipper of Balaenoptera Borealis. 
Note the resemblance to fingers. 
the neck region is not of the same length. This is conspic- 
uously evident in the giraffe (Figure 148), but when one ex- 
amines this very long neck there will be found only the regu- 
lar seven neck vertebrae. Each of these vertebrae in the 
neck of the giraffe is very large, and this is an adaptation ADAPTATIONS FOR PROTECTION 
213 
that helps the giraffe in securing its food, which consists of 
the leaves of trees. 
Some strange modifications, the pouch of the kangaroo 
and the trunk of the elephant, should also be mentioned. 
The kangaroo is one 
of the simpler animals. 
The young are helpless 
at birth and are carried 
around in a special pouch 
(Figure 157) until they 
are able to take care of 
themselves. The milk 
glands are located in the 
pouch so that the young 
are easily nourished and 
protected. The trunk of 
the elephant is composed 
of the nostrils and upper 
lip drawn out into a long muscular organ (Figure 159), and is 
used in bringing food to the mouth. The web of the flying 
squirrel is another strange adaptation which enables it to 
sail more easily through the air. 
157. Adaptations for Protection. - Mammals are found 
widely distributed over the surface of the earth, living in 
Figure 155. - Flying Squirrel. 
The skin is stretched between the fore- 
and hind-legs and acts like a parachute. 
Does the animal really fly ? 
American Museum of Natural History, New York, 
Rgure 156. - Skeleton of Ziphioid Whale. 214 
MAMMALS 
Photographed by Meyer and Widma.. 
Figure 157. - Kangaroo with Young in Pouch. 
the frozen North and the humid tropics or roving over plains 
and mountains. Everywhere they show adaptations in 
habits and form. 
The color of the white polar bear and Arctic fox renders 
them inconspicuous against the ice and snow. Deer are 
among our swiftest runners and the possession of such speed 
helps them to escape when being chased. In marked con- 
trast to the habits of the deer, when in danger, is that of the 
opossum (Figure 158) which often rolls up into a ball and ADAPTATIONS FOR PROTECTION 
215 
feigns death. After the animal which has been annoying the 
opossum withdraws, it deliberately and slowly begins to move. 
Whales are aquatic mammals that have lost most of their 
protective coat of hair but have developed instead a thick 
layer of protective fat beneath the skin. This is whale 
blubber. The porcupine has its hair enlarged and special- 
ized into spines. These special hairs effectively protect the 
porcupine from lynx and wildcats when they try to feed on 
With permission of Nature Magazine. 
Figure 158. - American Opossum. 
it. These spiny hairs, in turn, are in marked contrast to 
the protective coat of wool of sheep, which is modified hair. 
There are as many habits and adaptations for escaping 
from enemies in mammals as there are for fighting. Burrow- 
ing in the ground like the woodchuck, or nesting in the tree 
like the squirrel, protects the young as effectively as the 
adaptation of the tusks (modified teeth) of the elephant, 
or the enlarged canine teeth of the dog or bear which are 
used in fighting. 
There are many more examples of protective adaptation 
in mammals. How many can you name ? 216 
MAMMALS 
158. Humane Methods of Care and Protection. - Wild 
animals are valuable for food and especially for the fur they 
furnish to man. Those who hunt these animals are usually 
not in sympathy with any restrictive measures. The early 
stories of the Hudson's Bay Fur Company tell us of the 
men who set their traps over a large area, visiting them pos- 
sibly but once a week. Animals that were caught in these 
Figure 159.'-Elephant with a Highly Adaptive "Trunk." 
strong steel traps were unable to escape. There was a long 
period of suffering that should have been avoided. This 
can be done by requiring trappers to visit their traps often 
in the cases where traps are the only means of capturing the 
animal. In some instances the trap can be set under water, 
and the captured animal is drowned as it struggles in the 
water. This is a humane method. CONSERVATION OF USEFUL MAMMALS 
217 
From the earliest times it has been customary to make 
pitfalls where animals are caught in a deep hole and cannot 
escape. Here there is no suffering, but all such traps require 
constant attention, and so are frowned upon by trappers. 
The S. P. C. A.- The Society for the Prevention of 
Cruelty to Animals was organized primarily to protect 
domestic animals : to keep horses from being beaten or over- 
loaded, and to furnish proper care to neglected cats and dogs. 
But it also provides for the humane killing of strayed or 
old animals, and takes over the care of pet animals while 
their owners are away. 
Mammal Sanctuaries. - Yellowstone National Park in 
the state of Wyoming is the main sanctuary for large mam- 
mals. Here the bison, moose, elk, mule and white-tailed 
deer, black and grizzly bears are protected during the entire 
year. Even such predatory mammals as the timber wolf, 
coyote, and mountain lion are partially protected in this 
park. The number that are killed is determined by their 
relative destructiveness to the other animals in the park. 
As soon as these predatory animals become too numerous, 
a few are killed in order to keep them from becoming a seri- 
ous menace. This is one of the first instances in our country 
where destructive animals are being preserved in a wild 
state for educational purposes. 
159. Conservation of Useful Mammals. - With the 
steady growth of population, more and more wild animals 
have been killed to supply the increased demand for food 
and clothing. In fact, so great has been the slaughter of 
some of the most valuable animals that laws have been 
passed to protect them from total extinction. Some of these 
laws make it illegal to kill certain kinds of mammals at any 
time of the year; others protect them only while rearing 
their young. In the first class in New York State, we have the 
elk and beaver, and in the second the deer, fox, and raccoon. 
The laws protecting mammals are not uniform throughout 218 
MAMMALS 
the United States, and this is one of the reasons why an extra 
effort should be made by lovers of animals. 
These regulations were fairly satisfactory until fashion 
decreed that furs should be worn summer and winter. In 
order to supply this whim more than one hundred million 
hides were sold in the markets of the United States during 
the years 1919 to 1921, inclusive. This is an enormous 
increase in the use of the skin of mammals. 
Photographed by Byron Harmon. 
Figure 160. - Bison or American Buffalo. 
In 1860 there were 5,000,000 buffalo in America, in 1903 there were 
only 1753; but now, owing to the protection which they receive, there are 
over 10,000 of these animals. 
Many of our common mammals were not extensively 
killed for their fur until 1919. During the three years for 
which there is a record, over fourteen million muskrats were 
sold as Hudson seal, nearly twenty-four million insect-eating 
moles, and over thirteen million hides of the American and 
Australian opossums were marketed. These are but four 
of the nineteen kinds of fur bearers recently introduced by 
the fur trade to replace the original fur bearers whose supply Red Foxes. 
The red fox is one of the few wild animals that have survived as man has 
come to occupy the land. The secret of his success lies in his skill in out- 
witting man and dogs. This skill and his remarkable swiftness in running 
aid him also in capturing his food. NECESSARY DESTRUCTION OF MAMMALS 
219 
is diminishing. The entire world is being searched to meet 
this abnormal demand. Many regions have no protective 
laws, so that the extinction of the fur-bearing animals in- 
habiting them is imminent, unless we are willing to forego 
the gratification of our desire to wear furs as ornaments. 
The facts just given indicate that in a very few years the 
great group of fur-bearing animals will be largely found only 
in the museums and zoological parks unless there is a change 
in the sentiment of the American people. A great amount 
of pleasure may be derived from watching these animals in 
their natural surroundings or even from seeing pictures of 
them. Let us be willing to share this pleasure with the boys 
and girls of future generations. It will be a moral and 
spiritual loss to them that is worth much more than the 
immediate monetary gain to a few fur dealers. The present 
abnormal destruction is artificial and unnatural. 
We should extend to mammals the same kind of protec- 
tion that we have to birds, wild flowers, and trees. As we 
have refrained from destroying these beautiful living things, 
we have come to have a deeper love for Nature. This deeper 
love for Nature has helped as nothing else can do to make 
us happy as we go to the parks or woods for rest and recrea- 
tion. 
160. Necessary Destruction of Mammals. - During the 
year 1922, the United States Bureau of the Biological Survey 
employed more than 250 expert hunters who killed, trapped, 
and poisoned approximately 80,000 of the dangerous and 
predatory mammals. These included 687 timber wolves, 173 
mountain lions, 114 bears, 2,827 bobcats and Canada lynxes, 
and 77,185 coyotes. The extensive grazing areas for horses, 
cattle, sheep, and goats are in the western mountain and 
prairie states, where these mammals are numerous. 
The president of the State Agricultural College of New 
Mexico estimates that during recent years 34,350 cattle, 
165,000 sheep, and 850 horses were killed by these predatory 220 
MAMMALS 
mammals in his state alone. These losses meant the sacri- 
fice of 16,000,000 pounds of meat and 1,320,000 pounds of 
wool, worth all together over $2,716,000. A similar report can 
be made for each of the fifteen states where numerous herds 
of domestic mammals are pastured, so that the statement 
that the United States Biological Survey has effected a sav- 
ing of more than $75,000,000 in the animals that it has 
With permission of Nature Magazine. 
Figure 161. - Wolf. 
protected in the past six years seems reasonable. This great 
saving has cost the people only $6,080,846. 
The Rat, the Worst Mammalian Pest. - Early in our life 
as a nation the black rat was introduced from Norway. For 
a time it spread rapidly and soon became a nuisance. Some 
time after the brown rat came from Europe, escaping from 
the boats. This animal exhibited from the first great versatil- 
ity in its habits and food. It was so much more pugnacious ECONOMIC IMPORTANCE OF MAMMALS 
221 
than the black rat that it was but a few years before the 
earlier immigrant was almost completely exterminated by 
this later arrival. 
These troublesome brutes may possibly do some good as 
scavengers, but it is so small in comparison to the damage 
wrought that it is completely overshadowed. The brown 
rat causes damage to cereals and grains estimated at more 
than $200,000,000 annually in the United States. In this 
connection you should read " The Brown Rat in the United 
States," by David Lantz, Bulletin No. 33, Biological Survey, 
United States Department of Agriculture. 
A new and more successful method for wholesale killing 
of rats consists in mixing barium carbonate with flour dough 
which is then made into small round cakes less than an inch 
in diameter and about one fourth of an inch thick. Barium 
carbonate is a deadly poison to rats but only slightly poison- 
ous to human beings, livestock, and poultry. 
161. Economic Importance of Mammals. - Man finds 
some animals helpful, some harmful, and some neither. The 
domesticated mammals, especially the horse, cow, sheep, 
goat, and pig, are of the greatest use to man in this part of 
the world. In cold regions, reindeer are the main source of 
food and clothing, and are also used for beasts of burden. 
In desert regions, the camel is the most useful, and in hot 
regions elephants are of great value as beasts of burden. 
Dogs and cats have long been man's companions. Of the 
wild mammals, seals and walruses, which live in the water, 
furnish food, fur, and leather. The whale furnishes whale- 
bone, food, and oil. 
Man is learning to make use of the habits of other mam- 
mals ; for example, we build roosts in the vicinity of swamps 
and marshes to furnish shelter for bats by day. At night 
the bats fly about, catching the insects which annoy man 
and animals. There are harmful mammals, too, such as 
gophers (gb'ferz), prairie dogs, and rabbits, which injure 222 
MAMMALS 
man's land and his crops. Rats and mice consume much food 
and destroy much that they do not eat, besides carrying dis- 
eases. Red squirrels damage beds and furniture if they gain 
access to the house, and out of doors they destroy the 
eggs and young of birds and the seeds of evergreen trees. 
Rats, mice, and guinea pigs have proved of great use in 
laboratories where the causes and effects of diseases are 
studied. Their reaction to diphtheria, tuberculosis, cancer, 
and other diseases is similar to that of man. As a result 
of these studies the skillful physician is more successful in 
relieving sufferings. 
Various mammals of economic importance such as the 
rabbit, skunk, and beaver will be discussed more in detail 
in the following sections. The Report below should be 
begun now and kept up to date during the year. 
REPORT ON MAMMALS 
TO BE FILLED OUT FIRST FROM GENERAL KNOWLEDGE, LATER EXTENDED 
BY TRIPS TO FIELDS, WOODS, OR PARKS 
Where Kind of Life in Life in .. tr. 
Kinds Found Food Food Winter Summer Benepicial Harmful 
162. Bats. - This word was applied a long time ago to 
animals that " fluttered at night," and indicated their chief 
distinction from all other mammals. Bats all have the bones 
of the fingers greatly elongated, but there are no more joints 
or bones in each finger than in your own hand. Over these 
greatly lengthened fingers is stretched a thin, rubbery wing- 
membrane which is double in thickness. It is also attached 
to the side of the body, hind-legs, and tail. In this mem- 
brane are found special sense organs that enable the bats BATS 
223 
to detect objects as they fly rapidly in the dim evening light. 
When their eyes are covered with wax so that they cannot 
see and they are set free, they fly about freely, never touching 
objects, even avoiding and passing between silken threads. 
The sense organs that permit the bats to fly so rapidly with- 
out injury are numerous hairs that are supplied with nerves. 
With permission of Nature Magazine. 
Figure 162. - Bat with Expanded Wing. 
These hairs are stimulated by the rebound of the air from 
the objects which the bat is approaching. 
Their food consists of insects which are captured both 
with the mouth and the wing-membrane where it is attached 
to the body. The feeding time varies with the kind of bat, 
some seeking their food in the early evening, others early 
in the morning. All of the bats destroy so many insects 
that we regard them as highly beneficial. 224 
MAMMALS 
Bats are particular about keeping their bodies clean, lick- 
ing all parts which they can reach and washing their faces 
with part of the wing. While they have their own parasites, 
the widespread idea that bats carry around bedbugs, and 
are thus undesirable visitors to a house, is not true. 
The young are born in early summer and among some 
kinds are carried around by the mother for the first two or 
three weeks as she flies at night. After this they are left 
11 hung up " in some re- 
treat while the mother 
gathers her evening meal. 
When three months old 
they are able to fly and 
forage for themselves. 
163. Rabbits. - They 
are the most widely 
known of the wTild ani- 
mals and are hunted as 
game everywhere. There 
are three kinds of rab- 
bits : the snow-shoe 
rabbits of the Northern 
States, the large hares 
of the western plains, 
and the cottontails of the 
eastern United States. 
Among the most serious pests in orchard and tree planta- 
tions are rabbits. These animals also do considerable dam- 
age to garden truck and other farm products. 
The cottontail rabbit breeds several times each year dur- 
ing the warmer months, with litters averaging five or six 
young. The nest is placed in a hollow or depression in the 
ground and is composed of dead grass lined with fur which 
the mother pulls from her own body. These animals breed 
so fast that in spite of their many enemies and the fact that 
With permission of Nature Magazine. 
Figure 163. - Bat Sleeping. RABBITS 
225 
they are hunted for food they often become so numerous as 
to constitute a serious menace to food production. 
Cottontail rabbits eat leaves, stems, flowers, and seeds of 
plants and grasses, and the leaves, buds, bark, and fruit of 
woody plants or trees (Figure 165). 
Natural Enemies. - The carnivorous birds and mammals 
are usually successful in keeping rabbits from becoming a 
Photograph by E. N. Sanborn. 
Figure 164. - Rabbit. 
menace. The hawks, owls, and eagles are the chief birds 
which destroy them, while foxes, minks, weasels, skunks, 
dogs, and cats are the mammals that prey upon them. 
Protection of Trees. - Many devices for protecting apple 
trees and other fruit trees from rabbits have been recom- 
mended. The majority of these consist of paints, smears, 
or washes, supposed to be distasteful to the rabbit. Some 226 
MAMMALS 
of these are detrimental to the tree, such as coal tar and 
pine tar, while carbolic acid affords only temporary protec- 
tion. Bitter substances are useless against rabbits. 
A poisoned wash of starch and glycerin, tried during the win- 
ter of 1913-1914 in Idaho by a field agent of the Biological 
Survey, gave excellent results in protecting young orchards 
from jack rabbits, and would probably be equally effective 
where cottontails are 
concerned. The wash is 
prepared as follows: 
Dissolve 1 ounce of strych- 
nine (sulphate) in 3 quarts 
of boiling water. Dissolve J 
pound of laundry starch in 1 
pint of cold water. Pour the 
starch into the vessel con- 
taining the strychnine and 
boil the mixture a short time 
until it is clear, adding 6 
ounces of glycerin and stirring 
thoroughly. When it is cool 
enough apply with a paint 
brush to the tree trunks. 
The glycerin and 
starch adhere well and 
form a thin coating on 
the bark. Rabbits at- 
tacking such trees are 
quickly killed. In the Idaho experiments none of the trees 
were damaged badly enough to affect their growth and all 
the rabbits in the orchards were destroyed. The method is 
well worth trying; but care should be taken not to endanger 
domestic animals. 
164. Skunks and Weasels. - The skunk is the most 
common of the wild, flesh-eating animals. It has, as close 
relatives, the minks and weasels. All of these animals are 
Figure 165. - Tree Girdled by Rabbits. SKUNKS AND WEASELS 
227 
capable of discharging a strong and almost suffocating odor 
when annoyed or angry. 
This offensive odor is manufactured in glands located 
near the tail and is an adaptation that has a decided influ- 
ence on the habits of the skunk. The skunk is no longer 
required to be alert to escape its enemies and so has become 
fat and lazy. Its muscles are soft, and rapid exertion ex- 
hausts it sooner than any other member of this group. 
The food of the skunk consists of grasshoppers, crickets, 
snakes, eggs, the young of birds, and field mice. It is only 
occasionally that a hen is 
captured, and the general [|^ 
habits of this animal ' 
are decidedly beneficial. 
Skunks hibernate in the qr 
winter in the holes of 
other animals, and it is not 
unusual for more than one 
family to occupy the same Figure 166. - Skunk. 
winter quarters. They 
usually come out in February and seek what food may 
be found. At this time there are no insects, so their food 
consists of such animals as rabbits. 
By May the young are able to begin foraging for their 
own food, and it is not unusual in the early evening to see 
the mother and her brood slowly wandering about as they 
capture insects. 
For many years the skin of skunks was sold in the fur 
market as " Alaskan sable," but at the present time it is 
more often known as skunk fur. This fur is made up chiefly 
in muffs and neck pieces, and the demand for it has become 
so great that regular skunk farms are conducted at a profit, 
due to the increased price of fur during the past 15 years. 
Weasel. - Closely related to the skunks are the weasels, 
which are very destructive of birds, rabbits, and poultry. 
Figure 166. - Skunk. 228 
MAMMALS 
Their thin, muscular bodies enable them to move with great 
rapidity and their endurance carries them many miles in a 
single night. It is interesting to contrast the difference in 
habits between skunks and weasels. 
165. The Beaver. - The beaver is one of our most in- 
teresting mammals because of its social habits and archi- 
tectural ability. The demand for its fur and oil has led to 
As the water in the pond recedes, the muskrats dig canals that enable 
them to reach water from their lodges in the bank without going over land. 
How does this show adaptation in the behavior of these animals ? These 
canals are often mistaken for beaver runways. 
Figure 167. - Runways of Muskrat. 
its extermination in many parts of the country. In the 
Adirondacks beavers were trapped and hunted with such 
vigor that for a few years previous to 1905 none was to be 
found. In 1905 several pairs were obtained from Yellow- 
stone National Park and liberated near the old beaver haunts 
in the Adirondacks, and at the same time laws were passed 
protecting them. Now they are numerous throughout the THE BEAVER 
229 
Adirondacks wherever natural conditions are favorable. 
The beaver is frequently selected as an emblem of industry. 
Some of the interesting facts in connection with the life of 
the beaver follow. 
1. With their strong teeth they are able to cut down trees 
more than a foot in diameter. 
2. They cut up the trees into lengths which they can 
handle in the water (Figure 168). 
Figure 168. - Young Poplar Trees Cut Down by Beaver. 
Notice the top of the stumps. 
3. If the trees are large and there is no water near, they 
dig canals leading back to the fallen tree. 
4. They build dams that are eight or ten feet high and 
twenty or thirty feet wide. These dams frequently raise 
the level of lakes so that the shore line is changed (Figure 169). 
5. If the stream is large and the pressure on their dam 
becomes too great, they build a secondary dam below the 
first one, which provides slack water and thus protects the 
main dam. 230 
MAMMALS 
6. Their houses are built of mud and sticks on the margin 
of the ponds after the dam is finished. They live in these 
houses and enter them from below the surface of the water. 
The purpose of the dam is to provide a pond with deep water 
for their protection and use (Figure 169). 
Beavers live in colonies and work industriously in building 
dams and houses. Some damage is done by their cutting 
Figure 169. - A Beaver House. 
What is it used for ? 
trees and damming up streams. The great popular interest 
in beavers and their works more than outweighs the little 
harm they do. 
166. The Horse. - The horse is interesting because it has 
been associated with man since the pre-historic period known 
as the Stone Age. It has been suggested that man " first 
hunted horses for food, then drove them, and finally used 
them for riding and as beasts of burden." The fine animals THE HORSE 
231 
which we see to-day have gradually developed through this 
long time from a small animal about the size of a fox terrier. 
The earliest remains of the feet of the ancient horse show 
that it had four toes and the remains of a fifth in the front 
foot, while the hind foot had three toes and the remains of 
a fourth. The horse and the deer, which also has many 
stages preserved in the rocks, afford examples of the manner 
in which some of our present animals have developed. 
Figure 170. - A Standard Breed of Trotting Horse. 
The domesticated horses were developed in the old world. 
In the warmer regions, where food was plentiful, the largest 
horses developed, while in the north, where food was less 
abundant and the conditions were more severe, the Shetland 
pony appeared. Most breeds of horses were developed 
in France and England. There are three general types: 
namely, draft horses, which are the largest and heaviest, 
with short, strong limbs and thick necks, of which the Per- 
cheron, Belgian, and Clydesdale are common types; coach 
or carriage horses, which are graceful and plump but not so 
heavy as the draft horses; and roadsters or trotting horses, 232 
MAMMALS 
which are the lightest and slimmest of the horses. Roadsters 
have long legs, a thin neck, and are noted for their intelli- 
gence. Saddle horses belong in this third class (Figure 170, 
a fine specimen). 
The mule has been known for many centuries. Even in 
the days of ancient Greece and Rome mules were used in 
agriculture. They are stronger, more patient, live longer, 
and are surer footed than horses. Because of their great 
endurance and adaptability, they are more widely used than 
horses. 
167. The Cow. - Cattle are descended from the wild ox 
of Europe and Asia, and practically all our popular breeds 
have been developed in Europe, mainly in the British Isles. 
There are two chief types of cattle : the beef type used for 
food and the dairy type most valuable for the milk, butter, 
and cheese that they produce. The beef type is character- 
ized by " blocky " bodies, a form which yields the greatest 
quantity of meat. The beef cow is not expected to produce 
much milk. Shorthorns and Herefords, English breeds, 
also Angus and Galloway, Scotch breeds, are good repre- 
sentatives. The dairy type presents a different appear- 
ance from the beef type, having a much less regular body 
and a very large udder (Figure 171). The Island breeds, 
Jersey and Guernsey, are among those most famous for the 
production of butter fat rather than for the quantity of 
milk. Jerseys are especially valuable as family cows. 
Guernseys, larger and heavier then Jerseys, yield more milk 
and more meat. The Ayrshires, a Scotch breed, are known 
for the superiority of their milk for cheese, for the large pro- 
portion of butter fat, and for the fact that they yield more 
beef than any other dairy breed. Dutch cattle, the Hol- 
stein-Friesian breed, are famous for the quantity of milk 
that they produce. The milk is superior for cheese-making 
and, on account of the large quantity they produce, these 
cattle rank foremost in supplying cities with milk. Oxen SHEEP 
233 
of this breed grow to large size and are much prized as work 
animals. 
168. Sheep. - Sheep have been domesticated for ages, 
being possibly the first mammals domesticated by man. 
They thrive in nearly all climates and can find food where 
other mammals can scarcely live. Sheep furnish wool and 
Figure 171. -Cow and Calf. 
This cow gave 653 pounds of milk in seven days and 101 pounds in one 
day. The 653 pounds of milk yielded a little over thirty-three pounds of 
butter. The great food value of milk is better appreciated when one re- 
members that a cow giving 8000 pounds of milk supplies as much food as 
four 1200 pound steers, or sixteen 200 pound hogs, or thirty-two 135 pound 
sheep. Several cows have a record of producing 10,000 pounds of milk in 
one hundred days. 
meat. There are three classes, based on the quality of the 
wool. These are the fine wool breeds like the Merino, 
which had its origin in Spain, whence they have been carried 
to all countries where sheep raising is an important industry ; 
the medium wool breeds like the Southdown; and the long 
wool breeds like the Leicester, both of which are English 
breeds. The fine wool breed is raised principally for the 234 
MAMMALS 
wool, the meat value being a secondary consideration. The 
medium wool breeds are raised principally for the meat, and 
wool is a secondary consideration; while in the long wool 
breeds the mutton and the wool are of equal importance. 
Closely related to the sheep are the goats, which are the 
main dependence for milk and meat in the Island of Malta, 
Switzerland, and Asia Minor. 
Figure 172. - Hampshire Sheep. 
Excellent for mutton and wool. 
169. Pigs. - The pig has been developed from the wild 
boar of the old world. Meat is obtained more cheaply 
from the pig than from any other animal, because it adds 
more weight for a certain amount of food than either sheep 
or cattle and does it in a shorter time. There are two 
types in our markets, the lard type and the bacon type, 
which are produced largely through the methods of feeding. 
The well-known Berkshires, an English breed, whose color 
is black, are regarded by many as the aristocrats among OTHER PRODUCTS 
235 
pigs. America is famous for the breeds of pigs developed 
here, of which the Poland-China, originating in Ohio, the 
Chester White, first produced in Chester County, Penn- 
sylvania, and the Duroc-Jerseys, of New Jersey, are among 
the most popular. 
170. Other Products for Which Mammals Are Valuable. - 
Many of the animals we have just been studying supply us 
with food, fur, and wool. But mammals also furnish us 
with various other things, such as leather, oil, and buttons. 
Figure 173. - Sow and Pigs. 
Leather. - The skin of mammals consists of two general 
layers, the outer (epidermis) and inner (dermis), a study of 
which introduces us to some interesting biological problems 
connected with one of our commonest possessions - shoes. 
The skin of man is built upon the same plan as the skin of 
the animals from which the leather used in shoes, harnesses, 
grips, and gloves is manufactured. 
From the skin of the porpoise is secured a leather which can 
be used for the uppers in the manufacture of boots. From 
deerskin, gloves and the so-called " chamois " are made. 236 
MAMMALS 
The leather used in bookbinding comes chiefly from sheep 
and calfskin. Enameled leather and heavy work-aprons 
are made from horse hides. Most of the good shoes and 
boots are made from calfskin, while pocket-books, hat bands, 
and leather gloves come from sheepskin. Even sealskin 
when not suitable for furs is used to make the uppers of rid- 
ing boots and enameled leather, and pigskin is made into 
portmanteaus and footballs. 
This large industry depends upon the structure of the skin, 
especially the arrangement of the fibers in the dermis. In 
the skin of a fish or an alligator, the fibers of the dermis 
run parallel and at right angles in the several layers, while 
in the hairy animals these same fibers do not follow any order 
of arrangement, which results in the production of a felt- 
work of interlacing fibers producing a strong skin which 
resists tearing or flaking. 
Most of the leather that is used in shoes to-day comes 
from the hides of cattle. Great numbers of these animals 
are slaughtered each year for food. Their hides must be 
removed with care to avoid cutting, as all such injuries de- 
stroy the fibers of the dermis. These hides are then sent to 
tanneries where each is made into a certain grade of leather, 
such as sole leather or the leather for the upper part of the 
shoe. This difference in thickness and firmness is produced 
largely by the method employed in tanning. When a vege- 
table tan is used, such as hemlock bark, oak, or sumac, sole 
leather results ; and when a mineral tan is employed, leather 
suitable for the upper part of the shoe is secured. 
Two common parasites, the white grub and the southern 
cattle tick, live in the skin and render it unfit for leather, 
so that it is to the advantage of the cattle breeders to keep 
their cattle free from these parasites. The United States 
Department of Agriculture has greatly assisted cattle raisers 
in exterminating these destructive parasites. The effort 
to exterminate the parasites, especially the southern cattle OTHER PRODUCTS 
237 
tick, was so successful that in 1918 hides valued at many 
millions of dollars were added to the general supply in the 
United States. 
Another biological factor in the production of good leather 
has reference to the care that the cattle receive. If they 
are well fed and properly housed during the winter and keep 
free from disease, their hides have a better texture and are 
finer grained. The coarser grades of leather are made 
from older cattle and those that have little or no shelter 
in winter. 
Man has never been able to originate or create leather. 
It must be first grown as the skin of some animal. Man's 
skill consists in his manipulations of the hide after a living 
animal has grown it. 
Mammals Valuable for Oil. - Oil is the name for fat in liquid 
form. The edible animal fats are butter, lard, and marga- 
rine. Whales supplied in 1922 nearly seventeen million 
pounds of oil in this country alone. Mutton tallow is used 
in the manufacture of candles. Tallow, bone fat, horse 
fat, and the fat squeezed from the skin of animals is used 
in the dressing of leather. Animal oils serve as a chief source 
of fats in the manufacture of soap, while a large amount of 
grease is of animal origin. In 1923 the animal and fish oils, 
fats, and greases, produced and used in the United States, 
exceeded one billion pounds and were valued at $118,432,275. 
Mammals and Buttons. - In addition to the immense num- 
ber of buttons manufactured from clams and mussel shells, 
there is a very considerable industry manufacturing other 
sorts of buttons. In expensive tailoring real horn buttons 
are used, sliced from the horns of cattle. However, many 
of the buttons used on clothing are made from " vegetable 
ivory," which is a nut and not an animal product. Great 
numbers of so-called bone buttons are made from the casein 
in skim-milk. The casein is coagulated, colored, and com- 
bined with certain chemicals which give it solidity. These 238 
MAMMALS 
buttons are made by compression. Not only are buttons 
made by this process but umbrella handles, hair brush han- 
dles, and similar products. 
Many interesting studies can be made of the life of this 
group. The different kinds of mammals can be detected by 
their tracks, the distance between footfalls, claw marks on 
trees, logs, or ground, tooth marks on wood or bone, their nests, 
shelters, runways, holes, trails, and dust paths, all tell some- 
thing about each kind. Where do they live? In the soil, 
among the rocks, in the water, or the air? What effect do 
unusual climatic conditions such as storms, floods, and for- 
est fires have? Which ones are active in the winter and 
which inactive? How is the particular mammal you are 
studying related to other animals? Who are its enemies 
and its friends? Does it have the same enemies in youth, 
middle age, and old age? When does it begin to be active 
each day ? How long is it active and when does its activity 
cease ? Does the animal spend the entire year in one locality 
or does it migrate? If it migrates, in which direction and 
how far does it go? Can you find out any of the'causes of 
migration, such as food supply, and changes in climate? 
For those animals that hibernate the time of entering and 
emerging from hibernation should be observed. Are they 
completely inactive during this period? As these animals 
move about during the active season what is their method of 
locomotion? Do they run, jump, climb, dig in the ground, 
swim, or fly ? What foods do they eat ? Do these foods differ 
at different seasons ? Do they store up any food ? Are they 
dependent on water ? What are the various sounds and calls 
made? Do they have warning calls and alarm calls? The 
calls of mammals may be described under barking, baying, 
screaming, howling, squeaking, squealing, singing, roaring, 
bugling. 
Home Studies on Mammals SUMMARY 
239 
These are a few of the natural history studies which you 
can undertake. They should be made in connection with 
the Report on Mammals given on page 222. 
OUTLINE 
Mammals 
Defined 
Kinds of 
Carnivora 
Rodents 
Ungulates 
Primates 
Special adaptations 
Fore-legs 
Hind-legs 
Vertebrae 
For protection 
Color 
Hair 
Teeth 
Tusks 
Protection 
S. P. C. A. 
Sanctuaries 
Conservation 
Laws 
Regulations 
Restrictions 
Destruction 
Of dangerous mammals 
Of mammals for food 
Of rats 
Economic Importance 
For food 
For clothing 
Typical mammals 
Bats 
Rabbits 
Skunks and Weasels 
Beavers 
Horses 
Cows 
Sheep 
Pigs 
Other Products 
Leather 
Oil 
Buttons 
SUMMARY 
Mammals are animals that are to some extent covered with hair and 
that suckle their young. There are nearly always two pairs of append- 
ages that undergo a wide range of adaptations. The wild mammals 
still furnish us with our furs, some food, leather, and oil. The impor- 
tance of this group of animals is so great that regulations governing 
the killing of them during the breeding season have been made, as well 
as special efforts to destroy the predaceous ones. Our domestic ani- 
mals which serve us in so many ways have gradually developed into 
their present form and usefulness. Man had to learn first how to use 
the fur and skin of wild animals, then how to improve the quality of 
the fur and skin by careful feeding and breeding of the domesticated 
animals. 240 
MAMMALS 
QUESTIONS 
How do you tell a mammal from a bird? From a frog? From a 
fish ? What products of mammals do you use daily ? Which mammals 
live near your home? Are they beneficial or harmful? How do you 
know? Where do they live during the summer? During the winter? 
What is being done to protect the beneficial mammals in your county? 
REFERENCES 
Davenport, Domestic Animals and Plants. 
Linville and Kelly, Zoology. 
Plumb, Types and Breeds of Farm Animals. 
Stone and Crane, American Animals. CHAPTER XV 
THE SIMPLEST ANIMALS - PROTOZOA 
A fire-mist and a planet, 
A crystal and a cell, 
A jelly fish and a saurian 
And caves where the cave-men dwell; 
Then a sense of law and beauty 
And a face turned from the clod - 
Some call it Evolution, 
And others call it God. 
- Carruth 
171. Cells. - In our study of the grasshopper and its 
insect relatives we considered their behavior and life pro- 
cesses. If we had studied the minute structure of any of 
these insects, the grasshopper, for example, and had used 
a microscope to aid us, we should have found that every 
organ was made up of numerous small parts joined together 
in a definite manner. These small parts are called cells. 
Any book on biology uses the word cell again and again. 
The name was first used by the Englishman, Robert Hooke, 
over two hundred years ago, when, with his crude micro- 
scope, he examined a piece of bark and found it to be made 
up of little rooms which looked like the cells of the honey- 
comb. These spaces he named cells. When better micro- 
scopes were made, the living parts of the cell were discovered, 
and it was found that Hooke had seen only the walls of dead 
cells. 
All plants and animals are composed of cells. A cell may 
exist alone, carrying on all the life processes itself, or it may 
241 242 
THE SIMPLEST AN1 MALS - PROTOZOA 
exist in connection with a great many other cells, as in all 
large animals and plants. In every case each cell is pro- 
duced from another cell. 
There are certain animals that are never more than one- 
celled even when they are full grown. These animals are 
called protozoa (pro-to-zo'a: Greek, protos, first; zoon, 
animal). 
The Protozoan Cell. - The protozoan cell is a single mass 
of living matter called protoplasm. In a general way it 
carries on the same life processes as the grasshopper, or any 
other animal. When this living cell comes in contact with 
heat, cold, electricity, chemicals, or other stimuli, it moves, 
and we say that it is irritable. The term irritability, used 
with a scientific meaning, is defined as the power of being 
aware of a stimulus. When this living cell is brought into 
contact with cold, for example, it makes a definite movement. 
It is aware of the cold stimulus. 
The living cell grows by using food. It takes in oxygen 
from the water or from the air, according to where it happens 
to live. It gives off waste substances. It can grow and 
reproduce other cells of the same kind. The cell is the unit 
of structure and function in all animals. 
Many protozoan cells have no limiting wall between the 
living substance and the water in which they live. Yet 
the protoplasm and the water do not mix, though we do not 
understand why. Other Protozoa living in the ocean are 
surrounded by extremely thin skeletons of lime. When the 
animals die their skeletons sink to the bottom and become 
massed in a sort of rock. The famous chalk cliffs of England 
were formed in this way. 
Habitat. - The habitat of any animal is the place where 
it lives. The Protozoa are small, usually microscopic, ani- 
mals common in stagnant pools and in swamp water. They 
are also common in salt water. In fact, Protozoa are likely 
to be found in nearly all ponds of water that contain food AMCEBA 
243 
for them. Often, in the summer time, our attention is called 
to the activities of Protozoa when the water from lakes or 
reservoirs has a fishy taste. This peculiar taste may be due 
either to animals or plants, or to both. When it is due to 
animals, it is caused by a disagreeable oil formed by a certain 
kind of Protozoa. 
172. Amoeba.1 - The name Amoeba (a-me'ba) is given to 
several different Protozoa, but all represent the simplest form 
of animal life known to us. 
For this reason they are 
always studied in biology. 
In order to describe cor- 
rectly the structure of 
even so simple an animal 
as the amoeba a few new 
words are necessary. 
Structure of Amoeba. - 
It is difficult for inexperi- 
enced students to see the 
living amoeba through the 
microscope, because the 
whole cell has a faint, 
grayish appearance, and 
in a strong light is transparent. But if this grayish appear- 
ance of protoplasm is once seen, it is always remembered. 
Figure 174. - Photomicrograph of 
an Amceba. 
1 No suggestion can be made which will always enable the teacher to 
secure amcebse. They are more frequently found in the slime and mud of 
stagnant water than anywhere else. Paramecia and other infusoria can 
usually be secured in abundance by placing a handful of hay or leaves in a 
jar and covering them with the ordinary water used in the laboratory. This 
is called a protozoan culture, and should be started about four weeks before 
the material is wanted for class study. The length of time that the culture 
should stand can be lessened by adding a little beef-extract and by keeping 
the jar near a radiator. Water sufficient to keep the hay or leaves covered 
must be added from time to time. When a good culture of Paramecia is 
once secured, the jar should be kept from year to year, simply adding water 
to the dried hay left in the jar when Protozoa are desired. 244 
THE SIMPLEST ANIMALS - PROTOZOA 
There is no well-defined cell wall; therefore the amoeba 
is an illustration of a living, naked cell. Near the center 
of the cell is a spherical mass of denser protoplasm called 
the nucleus. In many amoebae the nucleus is not easily seen 
except by means of specially stained preparations. The rest 
of the protoplasm in the cell is called cytoplasm (si'tb-plazm). 
This does not appear the same in all parts of the amoeba. 
On the outside, there is a thin, almost transparent layer, 
called ectoplasm (ek'tb-plazm: Greek, ecto, outside; plasma, 
form). The larger part 
of the cytoplasm is filled 
with numerous small 
granules and contains 
several vacuoles (vak'u- 
bl) or tiny cavities. This 
inner mass of cytoplasm 
is call endoplasm (en'do- 
plazm: Greek, endo, 
within; plasma, form). The vacuoles in the endoplasm 
may contain food, water, or waste products. The food and 
water vacuoles are temporary structures, but the vacuole 
which collects the liquid waste is always present. 
The living amoeba is continually changing shape and 
pushing out from the surface of its body blunt, finger-like 
projections of the protoplasm called pseudopodia (su-do- 
pb'di-a : Greek, pseudo, false ; pod, root of pous, foot), which 
give an irregular outline to the body (Figure 175). Some- 
times the pseudopodia branch out, and therefore the scien- 
tific name Rhizopoda (ri-zop'b-da: Greek, rhizos, root; pod, 
root of pous, foot) is the technical name for all amoeba-like 
Protozoa. 
173. Vital Functions of the Amoeba. - The amoeba has 
the same vital functions as the higher animals which we have 
already studied, but of course they are much simpler in this 
one-celled organism. 
Feeling pseudopodium 
Ectoplasm 
Endoplasm 
Nucleus : . 
Walking pseudopddium 
Figure 175. - Diagram of an Amceba. VITAL FUNCTIONS OF THE AMCEBA 
245 
Motion. - When the amoeba sends out a pseudopodium 
in any direction, the rest of the body flows gradually, by a 
rolling movement, in the same direction. This creeping- 
rolling motion of the protoplasm enables the amoeba to move 
through the water. 
Nutrition. - When the pseudopodium comes in con- 
tact with a minute plant upon which the amoeba feeds, the 
protoplasm of the pseudopodium surrounds the plant and 
takes it into the cell. The microscopic plant thus eaten 
by the amoeba is inclosed, with a small amount of water, 
in a tiny globe called the food vacuole. The food vacuole 
is to be thought of as a stomach in which digestion can take 
place, for the plant is digested in it. Digestion is accom- 
plished by means of an enzyme (see page 28). The nu- 
tritious parts are absorbed into the protoplasm, the un- 
digested parts are cast from the cell, and the food vacuole 
disappears. 
Food vacuoles are not always round (Figure 177), but take 
their shape from the form of the plant eaten. If a filament 
of a simple plant is taken as food, the food vacuole is much 
elongated. 
Respiration. - From the oxygen dissolved in the water, the 
amoeba obtains by osmosis the oxygen necessary to its life, 
and it gives off carbon dioxide from the cell. 
Excretion. - The term contractile vacuole is given to a vac- 
uole which is always present in the protoplasm of amoeba. 
This vacuole can be seen to increase slowly in size, then 
suddenly contract. As it contracts, the fluid in it is forced 
to the outside of the body of the amoeba. The filling out of 
this vacuole is due to the collection of excretory wastes from 
the surrounding protoplasm. It is called a contractile vac- 
uole because it contracts and expands, and an excretory 
vacuole because it collects waste products. 
Reproduction and Encystment. - The chief method of 
reproduction in the amoeba is simple (Figure 176). The 246 
THE SIMPLEST ANIMALS - PROTOZOA 
living cell divides into two equal parts, foiming two new cells. 
This process is known as fission(fish'un : Latin, fissio, cleft). 
When the food or water becomes unsuited to supply the 
needs of the cell, in order to live the amoeba often secretes 
(makes for itself) a thick wall completely surrounding the 
protoplasm. This process is termed encystment (en-sist'- 
ment: Greek, en, in; kystis, bladder). After the wall has 
been formed, the amoeba is able, for a long period, to resist 
cold, the drying up of the pond, or the lack of food. 
Figure 176. - Amceba Dividing by Fission. 
174. Paramecium. - One of the most common forms of 
Protozoa is the slipper-shaped Paramecium (para-me'-si-um), 
which is more active than the amoeba. It is abundant in 
stagnant water and in the hay infusions prepared in the 
laboratory. (See footnote, p. 243.) 
LABORATORY STUDY 
There are certain kinds of Protozoa that are usually found in pro- 
tozoan cultures. The most abundant form is the paramecium. With 
a microscope make repeated examinations of drops of water from the 
protozoan culture, until you are able to find the paramecium. Notice 
its shape, rate of movement, behavior on meeting obstacles, and the 
like. Report on what you can make out. Compare the paramecium 
with any other protozoon you can find, as to shape, rate of movement, 
size, color, etc. If available, examine slides which show the nucleus of 
a protozoon. Make sketches that illustrate the above features. LIFE PROCESSES OF PARAMECIUM 
247 
Structure of Paramecium. - The paramecium, like the 
amoeba, is a single cell, but it has both a large nucleus and 
a small one. It has an 
endoplasm, an ectoplasm, 
and a cuticle (ku'ti-kl), or 
cell wall. Through the 
cuticle there extend great 
numbers of cilia (sil'i-a), 
or threads of living pro- 
toplasm. The ectoplasm 
contains many thread- 
like darts known as 
trichocysts (trik'o-sists). 
These can be discharged. 
Within the cell are found 
food and water vacuoles 
as in the amoeba; but 
there are two contractile vacuoles, one at either end, and the 
food and water vacuoles are more numerous than in amoeba. 
175. Functions and Life Processes of Paramecium. - 
The life processes of the paramecium are not quite so simple 
as those of the amoeba, 
but are far less compli- 
cated than those of most 
of the animals we have 
studied. 
Locomotion and Defense. 
- The animal moves by 
the action of the cilia, the 
direction depending upon 
the angle at which the 
cilia are held. It can be 
observed that the animals 
move backward and for- 
ward, and that they also 
-C ilia 
Contractile.. 
Vacuole 
Nucleus-- 
■C uticle 
-Trichocysts 
Mouth- 
Food 
Vacuole' 
•Contractile 
Vacuole 
Figure 177. - Diagram of Paramecium. 
Figure 178. - Paramecia Stained to 
Show the Nucleus (Photomicrograph). 248 
THE SIMPLEST ANIMALS - PROTOZOA 
rotate on the long axis. Paramecia defend themselves by 
discharging their trichocysts. This discharge occurs either 
as a result of certain strong artificial stimuli, such as elec- 
tric currents or chemicals, or naturally because of collision 
with certain other Protozoa. If attacked by some animal 
which feeds upon them, they discharge the trichocysts in the 
region of the attack (Figure 179). 
Figure 179. - Paramecium. 
Being attacked by another protozobn that feeds upon it. The trichocysts 
are discharged, and they force the foe away. 
Nutrition. - The paramecium, like all other living things, 
requires food, which consists mostly of bacteria. These 
are collected by means of the cilia located on each side of 
the fold or depression called the gullet. At the inner end 
of the gullet is the mouth (Figure 177). The food thus col- 
lected passes into protoplasm in the form of food vacuoles. 
Digestion is accomplished by the aid of enzymes which put 
into solution the available parts of the food it eats, and the 
indigestible parts are cast off from the body. OTHER PROTOZOA 
249 
Respiration. - As in amoebae, the oxygen which is neces- 
sary to respiration is obtained directly from the water and 
passes into the protoplasm 
at all points. 
Excretion. - Excretory 
wastes are first collected 
in each of the two con- 
tractile vacuoles and then 
cast from the body. 
Gases escape from the en- 
tire surface. 
Irritability. - Both the 
amoeba and paramecium 
respond to jars, food, and 
their enemies in a definite 
manner. In each of these 
simple cells there is no 
structure which can be 
compared to the nerve 
cells or brain of higher 
animals. The ability to 
respond to stimuli in Protozoa seems to be a condition that 
is present in the whole protoplasm of the cell. 
Reproduction. - Paramecia reproduce by fission, i.e. an 
animal divides, producing two; these 
divide and produce two more. The pro- 
cess of fission goes on indefinitely (Figure 
180). Unlike the amoeba these forms 
cannot encyst when conditions of life 
become unfavorable. 
176. Other Protozoa. - If we examine 
stagnant water, we shall find a large 
number of other kinds of Protozoa. The 
more common forms are much like the 
paramecium and have many cilia on the 
Figure 180 - Paramecium before and 
after Dividing. 
Figure 181. Mala- 
RIAL PrOTOZOON IN 
_ „ 
Blood Corpuscle. 250 
THE SIMPLEST ANIMALS - PROTOZOA 
body. Several of these large, ciliated Protozoa feed on the 
smaller Protozoa. Some of the common forms are shown 
in Figures 182, 183, and 
184. 
All these various Pro- 
tozoa can be grouped 
into classes, each with 
certain distinct charac- 
teristics. For instance, 
all Protozoa that have 
pseudopodia are called 
Rhizopoda. In this 
group, the cells may be 
naked or may possess a 
hard mineral covering; 
a second group of Pro- 
tozoa are provided with 
one or more long, waver- 
ing threads called flagella 
(fla-jel'la: Latin, flagellum, whip), and have the name 
Flagellata; the flagella are longer than cilia and show 
more complicated movements. A third class, known as 
Infusoria (in-fu-so'ri-a), 
includes most of the 
common Protozoa found 
in protozoan cultures. 
Many of this class are 
provided with cilia. 
Economic Importance 
of Protozoa. - By far the 
greater number of Pro- 
tozoa are harmless, and 
many are helpful in that 
they serve as food for 
fishes. Others, however, 
Figure 182. - Vorticella. 
This protozoon is supported on a stalk 
which can contract and expand. Of what 
use is this ? 
Figure 183. - Some Flagellate Pro- 
tozoa. REVIEW OF THE VITAL FUNCTIONS OF ANIMALS 
251 
may become parasitic in our bodies and so cause such dis- 
eases as malaria, yellow fever, and sleeping sickness. These 
disease-producing Protozoa are of great economic importance 
to man, because they prevent him from carrying on his 
work. 
Paramecia consume considerable quantities of bacteria, 
but we do not know whether most of these are helpful or 
harmful. For this reason the 
economic value of paramecia is 
uncertain. 
177. Review of the Vital 
Functions of Animals. -Now 
that we have studied various 
forms of animal life and have 
seen that all have practically 
the same functions and life 
processes, it is interesting to 
review and compare these. In 
making this comparison we 
should observe especially the various adaptations which 
they use to perform these'functions. Prepare a table on the 
plan suggested by the following outline, giving the adapta- 
tion of each animal so far studied. 
Figure 184. - One of the 
Foraminifera. 
LIFE PROCESSES 
Animals Respiration Locomotion Food-taking Reproduction, etc. 
Grasshopper 
Bee .... 
Caterpillar . . 
Fish .... 
Frog .... 
Bird .... 
etc 252 
THE SIMPLEST ANIMALS - PROTOZOA 
LABORATORY STUDY OF THE EFFECT OF ALCOHOL 
AND TOBACCO ON PARAMECIA 
An experiment demonstrating the effect of narcotics on paramecium 
may be performed with very simple apparatus, - two pipettes or medi- 
cine droppers, a piece of black paper or cloth, and a dissecting lens, hand 
lens, or powerful reading glass. The necessary solutions consist of a 
good paramecium culture, a six per cent solution of alcohol, and a third 
solution prepared by bubbling tobacco smoke through about one ounce 
of water until a light amber color is produced. This solution keeps 
well and may be prepared several days in advance. Fill one of the 
medicine droppers about half full of water and make an ink mark on 
the glass at the water level, then force the water out of the dropper and 
determine the number of drops. Again fill the dropper to the level of the 
ink mark, force out one half the number of drops already determined 
and make a second ink mark at the level of the water remaining in the 
tube. 
1. To show the effects of alcohol upon paramecium fill the graduated 
medicine dropper to the level of the lower ink mark from the six per cent 
alcohol solution, and then, before relieving the pressure on the rubber 
bulb, draw into the pipette enough of the paramecium culture to raise 
the water level to the second ink mark. Place the dropper on the black 
paper and examine with the magnifier. The organisms will appear as 
small, white, rapidly moving objects. If the second pipette is filled 
with paramecium culture and placed beside the graduated pipette the 
observer can compare the paramecium, being affected by alcohol, with 
normal paramecium. Note that the organisms in the alcoholic solution 
are distinctly more active than those in water. This condition soon 
becomes reversed and within ten minutes those subjected to alcohol 
die. The actual strength of the alcohol in the pipette is about three 
per cent, because of the dilution with water containing paramecium. 
This percentage of alcohol is much lower than that found in many 
patent medicines and flavorings. 
2. To show the effect of tobacco smoke on paramecium fill the grad- 
uated medicine dropper to the first ink mark, from the solution pre- 
viously prepared by treating water with tobacco smoke, and then draw 
into the tube sufficient water from the paramecium culture to raise the 
level to the second ink mark. Examine as in part one. At first the 
paramecium will show about the same amount of activity as those in 
the normal media, but their activity will gradually decrease until at 
the end of ten minutes all movement will cease and the organisms will 
be seen lying on the lower side of the tube. OUTLINE 
253 
LABORATORY STUDY OF PROTOZOA 
Take a drop of water from an infusion rich in Protozoa; place on a 
slide and examine with a 16 mm. or j objective. Answer the questions 
suggested by the report. 
How Many Kinds- How Many Kinds Have - 
Number of 
Kinds 
Observed are free oftnnhod even zigzag constant varying 
swimming? by threads7 motion? motion? form? forms? 
OUTLINE 
Cells 
Protozoan Cell 
Protoplasm 
Habitat 
Amoeba 
Structure 
Nucleus 
Cytoplasm 
Ectoplasm 
Endoplasm 
Vacuoles 
Pseudopodia 
Vital functions 
Motion 
Nutrition 
Respiration 
Excretion 
Reproduction 
Paramecium 
Structure 
Endoplasm 
Ectoplasm 
Trichocysts 
Cuticle 
Functions 
Locomotion and defense 
Nutrition 
Respiration 
Excretion 
Irritability 
Reproduction 
Other Protozoa 
Rhizopoda 
Flagellata 
Infusoria 
Economic importance of Protozoa 
Review of vital functions of ani- 
mals 254 
THE SIMPLEST ANIMALS - PROTOZOA 
SUMMARY 
Protozoa are the simplest group of animals. They are found mostly 
in water, yet some are parasitic in higher animals. They are small and 
usually consist of only one cell. They reproduce mostly by fission. 
Some produce diseases in man and beast, such as malaria and the sleep- 
ing sickness of Africa. But the great majority of Protozoa are not 
harmful. 
QUESTIONS 
Compare the body of a protozobn with the body of a grasshopper. 
In what are they alike? In what different? 
Compare the amoeba and paramecium. 
Explain how the Protozoa eat, digest food, produce more Protozoa, 
and protect themselves. 
How do these vital processes compare with the similar vital processes 
in the grasshopper? 
In what ways are Protozoa injurious to man? Are they parasitic? 
REFERENCES 
Galloway, First Course in Zoology, Chapter X. 
Hegner, Introduction to Zoology, Chapters IV, V, VI. 
Jordan and Kellogg, Animal Life, Chapters II, III. 
Kellogg, Animals and Alan, Chapter V. 
Osborne, Economic Zoology, Chapter II. PART III 
THE APPLICATION OF BIOLOGIC PRINCIPLES TO THE 
HUMAN BODY 
CHAPTER XVI 
RESEMBLANCES BETWEEN MAN AND OTHER 
ANIMALS 
Man is a tool-making animal. 
- Franklin 
178. Man as an Animal. - In studying animals and plants, 
we have emphasized the life processes. We have found 
that each living thing can be analyzed according to its food 
habits and the place where it lives; its structures used in 
securing life-giving oxygen and removing wastes ; its organs 
for responding to light, heat, cold, sound, etc.; and finally 
its methods of producing more living things like itself. We 
also found in plants an additional life process, the ability 
to manufacture their own food from the uncombined and 
non-nutritious elements m the air and soil. As we approach 
the study of man, we naturally ask how all these facts that 
we have learned about animals and plants help us to under- 
stand how man lives. 
Perhaps the best way to learn about man is to study his 
life processes just as we did the grasshopper's and the frog's. 
In such a study we may omit the comparison with plants 
except incidentally, because man is an animal in all the 
points in which our comparison is to be made, and the simi- 
larities between animals and plants have already been em- 
255 256 
MAN AND ANIMALS 
phasized on page 211. This does not imply that man is 
nothing more than an animal, but simply that in many 
features of his life he lives as animals live. 
179. Antiquity of Man. - Many men who have made a 
special study of the fossil remains of man in the rocks believe 
that man began living in Europe about 25,000 years ago. 
This is their estimate of the length of time that has passed 
Figure 185. - Reindeer. 
This figure was carved on stone in a cave in Southern France, where the 
reindeer has been extinct for many thousand years. 
since the rocks were formed in which are found jaw bones 
or the bones of the legs and arms. In all*such cases so far 
there has been no difficulty in recognizing these fossil bones 
as belonging to man, although the races of people who lived 
fifteen or twenty thousand years ago no longer exist. 
Man's earliest homes must have been the shelter of trees 
and an occasional cave, and it is in certain caves in Spain 
and France that many early records of man are to be found. MAN'S ADAPTABILITY 
257 
There is no record of when man first began to use fire or to 
build definite shelters. In fact, both these necessities in 
our cold climate were not as important to early man, be- 
cause he appears to have wandered about in tropical and 
sub-tropical regions. This was even true of the climate 
of Spain and France in the period when he lived in the caves 
which have become famous for their many records of the 
early life of man. With the coming of the glacial period, the 
climate of all northern Europe and northern America be- 
came much colder, and the men who lived in regions that 
were influenced by the southward movement of the ice 
sheets had to adopt some means of keeping warm or perish. 
180. Man's Adaptability. - As soon as men became so 
numerous that they needed to go farther afield for the neces- 
sary food, protective measures were gradually introduced. 
Moreover, the same forces that compelled early man to 
migrate have continued to impel man to move out into un- 
known parts to see if he can find a place to live more easily. 
We shall see how this has come to have a vital influence 
upon our own lives as we examine more fully into man's life 
processes. 
We have lived so long in heated houses that we feel that 
it would be impossible to get along without a furnace fire; 
but we have all read how whole sections of France during 
the war had no heat and that our American soldiers were 
able to adjust themselves to what seemed to most of us an 
almost impossible change. This teaches us two important 
lessons: first, it shows something of how early man lived; 
and secondly, the wide range of adaptation in the body of 
modern, civilized man. This second lesson is very impor- 
tant because it encourages us to undertake physical diffi- 
culties which we had thought impossible; because we now 
realize that we can overcome them after having the heroic 
examples of the men, women, and children of Belgium and 
France. 258 
MAN AND ANIMALS 
It is also easier now than ever before to realize how man 
can live in all parts of the earth. When we described 
where frogs, fish, and grasshoppers were to be found, certain 
limits had to be made. Not so with man. He possesses 
something that no animal has - the power to rise above the 
limitations of his surroundings. This he does by building 
a house of ice in the northlands and spreading a tent of cloth 
in Arabia. His constructive ability has led man to invent 
various devices for his protection such as stone, brick, wood, 
or concrete houses, something that no animals are able to do 
in a manner that justifies their being compared with man in 
this respect. It is true that birds build nests, but they are 
always built in the same fashion; and it is true that beavers 
build dams, but they are always made of wood. The reason 
that man is able to do more different things than animals is 
because he has a better mind, a mind that can adapt itself 
to many different kinds of work, such as that done by car- 
penters, engineers, lawyers, teachers, etc. 
Tell what you can about the range of adaptation in 
animals that have not been domesticated by man. These 
simple and well-known comparisons give you some indica- 
tion of the sense in which man and animals are similar, and 
it is in this sense that we wish you to work out the com- 
parison of the life processes of man with those of animals. 
Scientists give four reasons in explaining why certain ani- 
mals and plants are not adapted to living in all parts of the 
world : (1) lack of suitable food ; (2) failure in adapting their 
lives to the peculiarities of climate; (3) too many enemies ; 
(4) inability to raise their young. All these man has been 
able to overcome. 
STUDENT REPORT 
The following table points out some of the common adaptations 
in animals. How are they related to the animal's success in life? 
Name some other habits which help to protect animals. YOUTH, MATURITY, OLD AGE 
259 
Active in Summer 
Active in Winter 
Earth 
Water 
Air 
Nest 
Night Feeding 
Day Feeding 
Color 
External Skeleton 
Method of Escape 
Home Protection 
Earthworm 
Fly . . . . 
House Sparrow 
Dog 
Man . . . . 
etc. . . . 
181. Youth, Maturity, Old Age. - The life of man is 
divided into three general periods, which are youth, the 
period of maturity, and the period of old age. These same 
terms are given when describing the life of animals«and plants. 
Youth is the period when living protoplasm always grows, 
if furnished with proper food. This is the time when boys 
and girls grow taller and heavier each year; when the tree 
grows new leaves and the limbs become longer; and when 
the small puppy is turning into a full-grown dog. During 
this period of change the boys and girls, the tree, and the 
puppy are all nourished by food, and this makes it possible 
for them to grow. 
Maturity is the period when man ceases to grow taller, 
although he continues to eat food as he did during the period 
of youth. The living protoplasm in his body does not in- 
crease in amount. The same can be said of the tree, for 
it does not grow taller; and the puppy of last year has 
become a full-grown dog. During this period of maturity, 
each living organism is able to repair its body as fast as the 
body wears out. The period of maturity varies with differ- 260 
MAN AND ANIMALS 
ent things; in some butterflies lasting but twenty-four hours, 
in man continuing for about twenty-five years. 
Old age in man begins when the body wastes faster than it 
is repaired, and in the tree when growth is over and decay 
begins. During this period of old age all living things use 
food as they did in youth and maturity, but it cannot build 
up the body as fast as it is worn out and death is the final 
result. Old age occurs in different ages in different individ- 
uals ; and the same is true of animals and plants. 
SUMMARY 
Man has the same life processes as the animals. He is able to live in 
all climates and localities in the earth. No plant or animal can do this. 
Civilized man has learned to control his surroundings. Animals and 
plants are controlled by their surroundings. Man like all other living 
things passes through periods of growth, known as youth, maturity, 
and old age. 
QUESTIONS 
What have you learned about plants and animals that will help you 
to understand how man lives? Where are the earliest records of man 
found? Why do men migrate? Why can man control his environ- 
ment? How do you understand the terms youth, maturity, and old 
age? CHAPTER XVII 
GENERAL STRUCTURE OF THE HUMAN BODY 
Know then thyself, preszcme not God to scan, 
The proper study of mankind is man. 
-■ Pope 
182. Superiority of Man. - In the last chapter, we saw 
how man came to live in all parts of the world in well-made 
houses to protect himself from the cold and rain. In this 
respect he is superior though similar to all other animals. 
As we studied his use of food, there was seen also to be a 
fundamental similarity between man and animals. Now 
as we take up the next life process of movement the same 
relationship will appear. 
We usually think of man as walking or running, and it is 
only when we witness an acrobatic performance that the wide 
range of movements possible to man is realized. That man 
can do so many more things with this body than any other 
animal is due to the greater development of his nervous 
system. The structures by means of which he moves and 
which are described in this chapter are the skeleton and the 
muscles. 
183. Regions. - The body of man like that of all the 
other higher animals is divided into the head, trunk, and 
limbs. These are the regions of the body. The limbs are 
built on the same general plan as the fore- and hind-legs in 
mammals. The trunk is divided into the chest, or thorax, 
and the abdomen. 
In the body of man there are three important cavities; 
namely, the cranial or brain case, the thoracic, and the ab- 
261 262 
GENERAL STRUCTURE OF THE HUMAN BODY 
dominal. In the cranial cavity is found the brain, the base 
of which passes through a large opening (Figure 187) to con- 
tinue as the spinal cord of the nervous system (Figure 246). 
The thoracic cavity contains a pair of lungs and the heart. 
This cavity is separated from the abdominal by the muscular 
diaphragm (Figure 
186). In the ab- 
dominal cavity are 
found the stomach, 
intestine, liver, 
kidneys, and re- 
productive organs 
(Figure 186). 
184. Skeleton. 
- The skeleton of 
the crayfish is al- 
most entirely on 
the outside of the 
body. In the fish 
and the frog you 
were introduced to 
the internal skele- 
ton ; the position 
of the skeleton in 
the fish, .frog, bird, 
mammal, and man 
is the same, and is 
one of the impor- 
tant ways in which we recognize that an animal belongs to 
the vertebrates. The skeleton of man, because of his erect 
position, seems at first sight to be quite different from that 
of the dog or horse, but as we examine the parts more fully, 
we shall see that they are really quite similar. 
There are more than two hundred separate bones in the 
adult human skeleton. For convenience we will describe 
Figure 186. - Thoracic and Abdominal Cavities, 
A, lungs; B, trachea; C, esophagus; D, stom- 
ach ; E, diaphragm; F, liver; G, intestine ; H, 
heart; /, spleen ; J, bladder. SKELETON 
263 
the skeleton under the following divisions: skull, spinal 
column, ribs, sternum, long bones of arm and leg, pectoral 
and pelvic girdles. 
Skull. - The bones of the skull are usually described 
under (1) the cranium proper, which is the bony case that 
Photographed by Henry W. Stiles. 
Figure 187. - View of Skull from Below. 
surrounds the brain, and (2) the bones that form the skeleton 
of the face. In the adult skull the bones have become fused 
and their outline is recognized often with difficulty. In 264 
GENERAL STRUCTURE OF THE HUMAN BODY 
early youth the joints between the bones are movable and 
allow for growth. The general shape of the skull is such 
- cranium 
,malar (cheek) bone 
- superior maxillary bones 
-inferior 
-cervical region of 
soinal column 
nasal bones- 
clavicle (collarbone) 
shoulder blade 
humerus 
d. 
radius- 
^sternum 
^ribs 
--lumbar region of' 
spinal column 
innominale bone 
-pelvic cavify 
-femur 
Ina 
carpus 
r-pha lances 
- patella (kneepan) 
-libia 
-hi hula 
--tarsus 
-phalanges 
that it gives very complete protection for the brain, and its 
arched surface is of great strength. The deep sockets in 
the front, protect the eye. The important parts of the ear 
Figure 188. - Skeleton of Man. SKELETON 
265 
with all of its delicate portions are inclosed by bones of 
the cranium and are thus completely out of danger. 
Photographed by Henry W. Stiles. 
Figure 189. - Front View of Skull. 
The bones of the face are mostly paired. The prominent 
cheek bones are just below the eye sockets and are separated 
by the bones of the nose. The upper and lower jaws con- 266 
GENERAL STRUCTURE OF THE HUMAN BODY 
taming teeth constitute the remaining important bones of 
the skull. 
Spinal Column. - The spinal column consists of thirty- 
three segments, or vertebra; (Latin vertere, to turn, because 
these bones turn more or less on each other). You can easily 
recognize the bones in the spinal column by running the 
fingers along the neck and down 
the middle of the back. The 
spinal cord is protected by the 
several vertebrae so that the en- 
tire nervous system is almost 
fully surrounded by bone. The 
different vertebrae permit a limited 
amount of movement which en- 
ables us to turn and bend the 
trunk in various directions. At 
the same time these vertebrae 
piled one on top of the other con- 
stitute a strong support for the 
weight of the body and the head. 
Ribs. - There are twelve pairs 
of ribs. These are slender curved 
bones with one end attached to 
the vertebrae of the back and the 
other end attached, directly or 
indirectly, to the sternum (Figure 
190). The attachment of the ribs 
to the sternum is in part by flexible cartilage. This permits 
the freedom of movement necessary in breathing. 
Sternum. - The breast bone or sternum in man consists 
of a single piece and serves for the attachment of the ribs. 
In childhood this bone consists of several distinct parts. 
Long Bones of Arm and Leg. - The arm and the leg of 
man are built upon the same plan. In the arm there is the 
long bone, the humerus, which extends from the shoulder to the 
a.-Oesophagus 
b.-Diaphragm 
Figure 190. - Diagram to 
Show the Relation of the 
Diaphragm to the Ribs. 
Between the ribs are shown 
some of the intercostal muscles 
that assist in respiration. SKELETON 
267 
elbow ; the two bones in the fore-arm, the row of small bones 
in the wrist which move freely upon each other, and the bones 
of the fingers. Similarly, there is the long upper part of 
the leg, the thigh bone or femur, that extends from the hip 
to the knee and corresponds to the humerus of the arm; 
then, there are the two bones that go from the knee to the 
Figure 191.- Diagram 
to Show the Struc- 
ture of Bone. 
The large circle, H, is a 
branch of the Haversian 
canal where the blood 
vessels are found. The 
spaces between the lines 
and oval black masses are 
bone. 
Figure 192. - Cartilage. 
Note that the living cells are separated by 
spaces represented by small dots. 
ankle, the several bones in the ankle, and the bones of the 
toes. The knee cap is an extra bone. 
Pectoral Girdle. - The pectoral girdle consists of the two 
bones which join the humerus at the shoulder. One of these, 
the collar bone, clavicle, connects the upper end of the sternum 
with the shoulder. The second bone is the shoulder blade 
or scapula. This is a large flat bone on the back of the 
shoulder and serves as a most important surface for the 
attachment of the powerful muscles that are partly respon- 
sible for the movements of the arm. 
Pelvic Girdle. - This is frequently known as the hip girdle, 
and really consists of six bones which in the adult are firmly 268 
GENERAL STRUCTURE OF THE HUMAN BODY 
united into a complete girdle. The pelvic girdle joins a 
number of the vertebrae which have become fused into the 
sacrum. The union of the bones in the pelvic girdle fur- 
nishes a firm base of support for the body and at the same time 
permits a large range of 
movement in the legs. 
185. Functions and 
Adaptations of the Skele- 
ton. - From the preced- 
ing paragraphs we see 
that the chief functions 
of the human skeleton 
are to support the various 
parts of the body and 
to protect the delicate 
organs. To this it is 
especially well adapted, 
almost the only impor- 
tant portion of the body 
which is not so protected 
being the abdominal 
cavity. 
186. Bone and Carti- 
lage. - Unlike the rest 
of the body the skeleton 
proper is hard. It con- 
sists of bone and a com- 
paratively soft substance 
known as cartilage, or 
gristle. There are cells in the bones just as there are cells 
in the liver, the muscles, and in the nervous system. Like 
the other parts of the body, the bones grow because the in- 
dividual cells are supplied with food from the blood. 
Cartilage occurs near the ends of the bones, in the ear, and 
in the nose. It is especially prominent in the wrists and 
Figure 193. - X-ray of Hand of Child. 
The bones in the wrist are forming. 
Between the joints of the fingers are seen 
small bones that later unite with the bones 
of the hand. Compare with Figure 194. BONE AND CARTILAGE 
269 
ankles of children. Therefore children should not be lifted 
by their hands or allowed to stand until a certain amount of 
bone has taken the place of this soft cartilage. This is readily 
appreciated when one examines an X-ray of the wrist of 
a child, which is almost entirely composed of soft cartilage, 
Figure 194. - X-ray of Hand of Adult. 
What changes have taken place since 
childhood ? 
Figure 195. - X-ray 
of Dislocated Finger. 
while the adult wrist has well-formed bones. The transition 
from soft cartilage to hard bone is due to the formation of 
mineral matter that takes the place of the cartilage. Adult 
bones have more mineral matter than the bones of children. 
187. Joints. - The numerous bones in the skeleton allow 
the body to move although giving a certain amount of rigidity 270 
GENERAL STRUCTURE OF THE HUMAN BODY 
and permanence of shape. Wherever two bones meet and 
allow movement, the term joint or, more technically, articula- 
tion, is applicable. The joints are divided into three classes : 
immovable joints, movable joints, and mixed joints. Im- 
movable joints (sutures) are found in the skull of the adult. 
The bones of the skull do not become firmly united until 
the head has reached full 
size, after which no move- 
ment takes place between 
these bones. 
Figure 196 a. - X-ray of the 
Same Bone after Healing. 
Notice the large "callus" 
of newly formed bone which 
makes this bone stronger than 
before it was broken. 
Figure 196. - X-ray of 
Broken Femur. 
Movable joints are the ball-and-socket joint in the shoulder 
and the hip and hinge joint in the elbow, wrist, knee, and 
ankle. 
The mixed joints are those of the spinal column, which 
allow only a limited movement. 
The movable joints are bound closely together by strong 
bands of connective tissue. These bands are called ligaments. 
The tearing or stretching of these ligaments is called a sprain. 
188. Broken Bones. - When the bones of a limb are 
broken, the physician sets them, i.e. places the broken ends STRUCTURE OF BONE 
271 
together, and puts splints on the limb to keep the parts from 
slipping until the new bone has formed (grown) and hardened. 
In Figure 196 is shown an X-ray pho- 
tograph of a recently btoken femur. In 
Figure 197 the same bone is shown. A 
large " callus " of new bone has formed 
around the broken ends, which gradually 
hardens, making this part of the bone 
stronger than ever. 
189. Structure of Bone. - One of the 
long bones from the arm or leg illustrates 
best the several parts. There is the long 
shaft with knobs on each end. These 
enlargements are the heads of the bone. 
The outer surface is covered with a tough 
membrane. If such a bone is sawed 
lengthwise, the following additional 
parts can be recognized: the long cen- 
tral cavity of the shaft filled with mar- 
row ; the hard bone of the shaft; the 
spongy bone toward each end; and the 
thin layer of cartilage covering each head. 
LABORATORY STUDY 
Study the skeleton, and examine long, flat, 
and irregular bones. How is the bone modi- 
fied to do its work? 
By means of a manikin, models, or organs 
of an animal, observe the general structure of 
the principal organs of the body. 
If one compares such a bone with a rib or shoulder blade, 
the central cavity is greatly reduced, having the marrow 
mostly confined to the spongy portion of the bone. 
The frame of a bicycle is a practical application of the 
principle that a hollow cylinder, like a hollow bone, gives the 
greatest amount of strength with the least weight. 
Figure 197. -Longi- 
tudinal Section of 
Femur, Showing the 
Compact and Spongy 
Tissue of Bone. 272 
GENERAL STRUCTURE OF THE HUMAN BODY 
STUDENT REPORT 
Make a report on the skeletal structures of animals as follows: 
Absent Jointed jo^^,d Horny Bony | Internal External 
Paramecium 
Crayfish 
Clam 
Frog 
Man, etc. 
190. Muscles. - The muscles are the lean parts of the 
flesh of animals. They are covered by the skin and are usu- 
ally dark in color. Birds are an excep- 
tion, for their breast meat is generally 
white. Muscles are of two kinds : volun- 
tary (governed by the will), such as those 
which we use in walking, or in moving 
the arms, Figure 198; involuntary, such 
as those which move the food along the 
digestive tract or assist in breathing. 
The voluntary muscles consist of many 
long muscle cells (fibers) bound together 
by connective tissue into a distinct bun- 
dle. Usually the muscle bundle is at- 
tached at each end to the bones through 
the tendon of connective tissue. A single muscle moves 
the arm in one direction only, and in order to lift the arm 
from the desk to the 
head, for instance, several 
muscles must act to- 
gether. 
The cells of the invol- 
untary muscles are unlike 
the cells of the voluntary muscles. Involuntary muscle cells 
occur in layers in the walls of the digestive tube, blood vessels, 
Figure 198. - Vol- 
untary Muscle 
Cells. 
Showing how the 
cells are bound to- 
gether with connec- 
tive tissue. At the 
end of the muscle 
the cells of the con- 
nective tissue form 
the tendon. 
Figure 199.-Involuntary Muscle 
Cells. ACTION OF A VOLUNTARY MUSCLE 
273 
the bladder, and the like, and they are not under the control 
of the will. 
The muscular tissue of the heart has characteristics of both 
the voluntary and involuntary muscles, so that it may al- 
most be said to belong to a 
special class. 
191. Importance of the Mus- 
cles. - When we remember 
that 40 per cent of the weight 
of the human body is in the 
muscles alone and that one 
fourth of the blood is found in 
these same muscles, their importance is appreciated. But 
this great mass of tissue so richly supplied with blood is 
solely for the purpose of producing movement. In addition 
to the movements that we are accustomed to see, such as 
the motion of the arms, legs, and the head, there is the con- 
tinued beating of the heart, the rhythmical contractions 
of the stomach and intestines, as well as movement in other 
organs. To all these should be added the wide range of 
movements in facial expressions. To accomplish these varied 
motions man uses more than five hundred muscles. 
192. Action of a Voluntary Muscle. - By placing the 
hand on the front of the forearm and raising the hand toward 
the shoulder, the muscle under the hand becomes shorter, 
thicker, and firmer. At the lower end of this muscle, a 
strong cord can be felt as the forearm is lowered. This cord 
is the tendon that attaches the muscle to one of the bones 
of the forearm. The upper end of the muscle is covered 
by other muscles, but we know that it is attached to the 
shoulder blade by two tendons. This muscle is the biceps, 
and like all other arm and leg muscles consists of a central 
part, the belly. It has its origin on the shoulder blade by 
two tendons and is inserted on the radius bone by one tendon. 
When a voluntary muscle produces motion, the two ends of 
Figure 200. - Heart Muscle 
Cells. 274 
GENERAL STRUCTURE OF THE HUMAN BODY 
Photographed by Henry W. Stiles. 
Figure 201. - Hip and Thigh Muscles. 
To show the parts of a muscle and its attachment. FOOD OF MUSCLES 
275 
the muscle are drawn closer together and the belly becomes 
shorter, thicker, and firmer. The living muscle cells are the 
only parts that undergo any change in shape, while the living 
cells in the connective tissue sheaths 
and in the tendons remain unchanged 
in shape. 
The voluntary muscles exist in the 
body, especially in the arms and legs, 
in bundles. One muscle is attached 
to the front surface of the arm, while 
a second muscle is attached to the 
back surface. The movements of the 
arm are brought about by the shorten- 
ing of a muscle in every case, conse- 
quently a muscle which straightens the 
bent arm is one of several of the mus- 
cles that are known as extensors. The 
bending of the arm is accomplished by 
one or more muscles which are known 
as flexors. This same general classifi- 
cation of muscles applies to the leg and 
to the muscles of the trunk. 
193. Nerve and Blood Supply of 
Muscles. - The muscles are richly sup- 
plied with numerous large and minute 
blood vessels and it is the blood that 
gives the deep red color to muscles. In 
recent years scientists have discovered 
that each muscle fiber is supplied with 
a fine branch of the main nerve that 
enters the muscle. This important 
fact enables us to understand how the 
nervous system is able to control the actions of our muscles. 
194. Food of Muscles. - The blood flowing through the 
muscles carries food to the muscle cells. The most important 
Figure 202.- Muscles 
of Upper Leg. 
Note how they are ar- 
ranged in bundles, which 
is an adaptation that en- 
ables the leg to be moved 
in various directions. 276 
GENERAL STRUCTURE OF THE HUMAN BODY 
of the food substances used in the contraction of a muscle is 
grape sugar, or glucose. This sugar is formed in the body in 
digestion from starch and cane sugar. Glycogen, the stored- 
up sugar in the liver, is also used to furnish energy in con- 
traction, but not until after it has become transformed into 
protoplasm. A small amount of fat is present in muscles 
and may be used up during their contraction. Under ordi- 
nary circumstances the protein foods do not furnish energy 
for contraction, but are used to repair the actual wastes that 
take place in the muscle cells as they do work. 
195. Fatigue of Muscles. - After you have played hard 
for a time, you become tired and want to rest. You are 
tired or, to express it more scientifically, your muscles are 
fatigued. When you are taking your physical exercises, 
some of the movements make your arms ache, and you do 
not do them in good form. You are using muscles that do 
not get much exercise and they become quickly fatigued. 
You may continue to move your arm until it is impossible 
to move it any longer. In such cases of extreme fatigue 
not only are the muscles tired but also the nerve cells. Two 
things are involved in the fatigue process of a muscle: first, 
there is the using up of the food energy necessary for mus- 
cular contraction; and secondly, there is the accumulation 
of waste substances produced by the activity of the muscles. 
196. Recovery from Fatigue of Muscles. - It is difficult 
to separate entirely a consideration of the muscles from the 
nervous system, as already explained, but some facts indicate 
in part what probably happens in the muscles as they are 
again made fit to do work. If the exhausted soldier is given 
a small amount of sugar while on the march, his fatigue is 
lessened. This is because sugar is quickly absorbed and 
is used by the muscles as a source of energy for contraction. 
This indicates that food will restore muscles. A second 
factor in relieving fatigue is rest, which gives the muscle 
cells time to recuperate by gradually building up the muscle IMPORTANCE OF EXERCISE 
277 
protoplasm, and removing wastes. As the energy required 
for the action of a muscle is mainly in the muscle protoplasm, 
there are changes that take place in it. Not all the energy 
of the muscle can be used in the contraction, and what re- 
mains is a waste substance that has to be removed. The 
removal of this waste is a large factor in relieving fatigue 
in muscles. 
Under unusual conditions the muscles exhibit a remarkable 
endurance. A fast walker, taking 152 steps a minute, raises 
his body about twenty-three feet a minute. If he continues 
to walk at this rate for twenty-four hours, it is equivalent 
to lifting his body 33,120 feet. During the war there were 
many instances where men remained active for longer than 
twenty-four hours, but in the end there had to be a period 
of rest that was correspondingly long in order to permit the 
removal of all of the accumulated wastes and to restore the 
used-up parts. The principle,thus remains the same whether 
the work done by a muscle is little or much. The muscle 
utilizes energy in contracting, and this energy must be supplied 
if the muscle is to work. 
197. Importance of Exercise. - We are now in possession 
of the facts that enable us to understand the reason for phys- 
ical training and some of the benefits to be derived from it. 
It is true that walking and running are forms of exercise, 
but they are both limited to but a part of the muscles of 
the body. People unaccustomed to a full set of " setting-up" 
exercises find themselves lame and sore after the first few 
times. This is because they exerted muscles that had been 
unused for a long time, and these muscles are not so strong 
as they ought to be. In a short time this lameness disap- 
pears and the morning exercises then give vigor and zest to 
the body. 
These exercises thus serve to keep the bulk of our body, 
our muscles, in a healthy state. Such a condition has an 
important bearing upon our ability to do good work with 278 
GENERAL STRUCTURE OF THE HUMAN BODY 
our brains because the mind works best when the rest of the 
body feels fit and full of energy. It is our duty to take our 
physical exercises seriously in order that we make our bodies 
as strong and vigorous as possible. 
The recreative forms of exercise such as basket ball, tennis, 
baseball, football, and rowing are valuable for the general 
health and are good for the development of muscle. But 
we should not indulge in violent exercise except after care- 
ful training, which should always be preceded by a careful 
physical examination. 
198. Use and Abuse of the Muscles. - All who have 
read about the results of the physical examination of the 
pick of the young men in America, during the recent World 
War, were startled by the large number that were declared 
physically unfit. This has caused us to inquire into the 
reasons why so many young people show such defects. Stu- 
dents planning to enter West Point are frequently rejected 
because their bodies are not well developed. And in any 
large group there are only a few who have their bodies suffi- 
ciently developed to enable them to qualify for our athletic 
teams. 
In all of these cases of physical unfitness, each person has 
the same number of muscles, more than 500, attached to 
the same part of the skeleton. The deficiency then must 
consist in the training which each individual has given to 
these muscles. 
The human body is not only very delicately adjusted or 
balanced but permits of a great variety of movements in 
the work performed. The muscles are subjected to varying 
degrees of strain, which have their influence not only on the 
organs of the chest and thorax, but upon the higher mental 
processes as well. Less energy is required in the correct 
use of the muscles than in the incorrect use of them. With 
the endless number of adjustments constantly taking place 
and in the wide variety of activities, everything that relieves USE AND ABUSE OF THE MUSCLES 
279 
friction and strain upon the body is of great benefit. It is 
possible to refer only briefly to the use and abuse of the 
muscles in sitting, standing, and walking. 
Sitting. - More and more of peoples' time is being devoted 
to work which is carried on in a sitting position, so that any 
suggestions leading to the saving of energy and lessening 
the fatigue of the muscles is very important. The correct 
sitting position is that with the trunk of the body straight, 
resting squarely on the hips, and not sliding down into the 
seat. The trunk should be kept at right angles to the long 
bones of the leg. It is easier to sit correctly in a shallow 
than in a deep seat. One can also sit correctly so far as the 
trunk is concerned and still become fatigued by bending the 
head too far forward at the neck. 
Simple corrective exercises for improper posture in sitting 
can be taken with the body in proper sitting position by 
moving the trunk forward and backward, bending only at 
the hip. 
Standing. - The correct positions of the body in standing 
and walking are similar, and the gain from the correct use 
of the muscles in these two natural movements is greater 
than that on sitting. The head should be well back, the 
chin drawn in, the chest raised, the abdomen flat, and the 
weight of the body borne on the balls of the feet. In such 
a position the head is nicely balanced with the least strain 
upon each of the muscles. The defects which incorrect 
position of the body causes require very definite exercises, 
as the weakness of the muscles is more pronounced in one 
region of the body than in another, such as the muscles of 
the back, neck, etc. To correct the standing posture the 
exercises known as standing at attention and standing re- 
laxed are the most frequently used. 
Walking. - Walking is a pleasurable form of exercise 
when the whole body is in correct position and the weight 
thrown forward on the ball of the foot. The feet should 280 
GENERAL STRUCTURE OF THE HUMAN BODY 
point forward instead of at any angle. It is easy to practice 
correct walking by simply holding the body in proper standing 
posture, and then walking forward along a line, each step of 
the foot directed forward with the front foot close against 
the toes of the rear one. 
199. Mental Attitude. - Every one who has witnessed 
well-trained men executing gymnastic or military drill has 
had his admiration stirred by the efficient manner in which 
they are using their muscles. And if we are really honest 
with ourselves, we will admit that we cannot handle our 
bodies as well. Just as soon as you acquire the correct 
use of your muscles, there is a feeling that you are in control 
of your body, and it affords a mental stimulus that no one 
should ignore. 
Our mental attitude has much to do with our posture. 
How much straighter we stand when we are cheerful than 
when we are dejected! And our posture also reacts on our 
mental attitude. When we are gloomy and downcast, we 
can often make ourselves more cheerful by standing erect 
and taking a brisk walk in the fresh air, breathing deeply 
and throwing out our chests. 
200. Hygiene of the Foot. - The human foot is an in- 
genious arrangement of bones, muscles, and tendons, whose 
function is to support the weight of the body. There are 
two arches in the foot, one located in the forward part, the 
anterior metatarsal, and the other running lengthwise and 
known as the longitudinal arch (Figure 203). Both of these 
act as shock absorbers and their perfect condition is essential 
to good feet. If, as often happens, one arch is depressed or 
broken down, we get what is called flat foot. Flat foot may 
be prevented by using a little care. It usually causes a 
feeling of unusual fatigue and weariness at night. 
The proper method is to walk with the feet parallel, as if 
you were on snowshoes, not with the toes pointed out. 
Walking with the toes pointed straight ahead strengthens HYGIENE OF THE FOOT 
281 
the muscles and prevents flat foot. The exercises described 
in the following paragraphs can be taken for the purpose of 
correcting this deformity, for flat foot is a real deformity. 
With the feet parallel, rise on the toes fifteen times the 
first night, sixteen the next night, and so on until you are 
doing the exercises fifty times. When you have reached 
Figure 203. - X-ray of the Foot of a Girl Wearing a High-heeled Shoe. 
The many layers of leather in the heel were fastened by means of glue. 
Notice the effect of raising the heel so high. It weakens the muscles on 
the back of the heel and places an unusual strain on the muscles of the 
arch of the foot. The wearing of such shoes is the source of much dis- 
comfort and is just one illustration of what one should not do who wishes 
to keep well. Compare with Figure 204. 
fifty, decrease one a day until you are back to fifteen and 
then begin again. 
The second exercise is to raise the toes off the floor so that 
you are standing on the heel. Do this fifty times. 
The third exercise consists of standing on the outside of 
the foot, and while in this position trying to curl the toes back- 282 
GENERAL STRUCTURE OF THE HUMAN BODY 
ward to meet the heel. Another excellent exercise is to pick 
up marbles with the toes. One or two days' trial of these 
exercises will convince you that there are muscles in your 
feet which you did not know were there. Keep at them, 
however, and you will soon be cured. 
Arch supports do not cure flat foot. They act only as 
temporary splints, filling the shoe so that the foot is bound 
Figure ,204. - X-ray of the Foot of a Girl Wearing a Sensible Shoe. 
Note how differently the pressure comes on the parts of this foot as 
compared with that shown in Figure 203. 
together and pinched. This often results in corns and cal- 
louses. 
Corns, callouses, and bunions are caused by the use of too 
tight or too short shoes or stockings. It is not an uncommon 
experience when buying new shoes to have the clerk fit you 
to a short or narrow shoe. Right there your troubles begin. 
Demand a shoe which does not pinch your foot. Especially 
in the case of growing children, new shoes should be large 
enough to allow for natural growth. SUMMARY 
283 
OUTLINE 
Regions 
Head 
Cranial cavity 
Brain 
Trunk 
Thoracic cavity 
Lungs 
Heart 
Diaphragm 
Abdominal cavity 
Stomach 
Intestine 
Liver 
Kidneys 
Reproductive organs 
Skeleton 
Skull 
Spinal column 
Ribs 
Sternum 
Long bones 
Arm 
Leg 
Pectoral girdle 
Clavicle 
Scapula 
Pelvic girdle 
Sacrum 
Functions and adaptations 
Bone and cartilage 
Joints 
Immovable 
Sutures 
Movable 
Mixed 
Broken bones 
Structure of bone 
Muscles 
Importance 
Voluntary 
Involuntary 
Extensor 
Flexor 
Nerve and blood supply 
Food 
Fatigue 
Recovery 
Exercise 
Use and abuse 
Sitting 
Standing 
Walking 
Mental attitude 
Hygiene of foot 
Flat foot 
Prevention of 
Exercises 
SUMMARY 
Man is able to move about as other animals. This he does by means 
of his muscles and skeleton, under the direction of the nervous system. 
The skeleton is covered by muscles and skin. Bones grow and are fed 
just like muscles or any other tissue in the body. The bones of the 
skeleton move by means of joints which are held in place by ligaments. 
Bones grow new bone, as is seen in the broken femur. There is a defi- 
nite plan of structure to all bones. 
The muscles are the flesh covered by the skin. The muscles are both 
voluntary and involuntary. Muscles are important both in the total 284 
GENERAL STRUCTURE OF THE HUMAN BODY 
weight of the body and in the numerous movements that they produce. 
Each muscle causes movement through the action of its individual 
cells, which are supplied by nerves and blood vessels. The muscle pro- 
toplasm is supplied with food for contraction purposes and food to 
repair the wastes. Muscles become fatigued and require food, rest, and 
the removal of wastes in order to recover from this fatigue. 
Physical training is valuable in helping to develop properly all the 
muscles of the body, in keeping the body well, and in making it the best 
body possible. Correct posture is important to health and depends 
partly upon mental attitude. Care should be taken of the feet, espe- 
cially in the selection of proper shoes. 
QUESTIONS 
How does the skeleton of man compare with that of the crayfish? 
How do bones grow? Why do they grow? Where is there the most 
cartilage in our skeletons? What are joints? What is a sprain? 
How do broken bones heal? How does muscle differ from bone? 
How many kinds of muscles are there? What is the work of each? 
Why are muscles important? What is the relation of the nervous 
system to muscles? What is the importance of the blood vessels to 
the muscles? Explain how the different foods are used by muscles. 
What is the value of physical training? Why does good posture help 
you? CHAPTER XVIII 
RESPIRATION 
Choke the air out of the lungs, and all is soon stagnation, cold and 
darkness. 
- Oliver Wendell Holmes 
201. Respiration is the life process in which oxygen is 
used in the cells of the bodies of plants and animals, and 
carbon dioxide eliminated from them. All animals carry on 
respiration, and in all the process is alike, although the vari- 
ous animals use different structures to secure the interchange 
of oxygen and carbon dioxide. The fish has special organs, 
the gills, while the frog and man have lungs. 
Student Report on Respiration 
Get Oxygen Breathe Through 
Water Air Water Air Skin Gill Lung Tybes 
Amceba 
Crayfish 
Fly 
Toad 
Bird 
Man 
202. Human Organs of Respiration. - In man air enters 
the nose and passes into the windpipe or trachea (tra'ke-a). 
The opening into the windpipe is covered by the epiglottis 
(Greek, epi, upon; glotta, tongue), which is raised during 
285 286 
RESPIRATION 
breathing and closed when food is swallowed. The windpipe 
divides into two branches, one entering each lung. Each 
branch is called a bronchus. The windpipe and bronchi are 
the air passages which carry air to the lungs. These pas- 
sages are kept open by numerous stiff cartilage rings, which, 
in the trachea, are not entirely complete on the side of the 
esophagus, and in the smaller tubes even less so. 
As each bronchus enters the lung, it divides into branches 
which in turn branch out again and again, until the entire 
lung is penetrated in all its parts 
by these passages. Finally each 
branch ends in a small pouch- 
like sac called an air cell or air 
sac. The walls of the air cells 
are thin, and the cells them- 
selves are surrounded by minute 
branches of the blood vessels. 
It is estimated that the highly 
folded condition of the walls of 
the bronchi make a surface larger 
than the entire surface of the 
body. All these thin walls of 
the lungs and blood vessels are 
adapted to the passage of oxygen 
into the blood. 
The lungs of man, then, consist of two large bronchial 
air tubes, many branches of the bronchi, air cells, blood 
vessels, and a few nerves, all bound up into two definite 
bodies (Figure 205). 
The voice box or larynx (lar'inks) is found just below the 
opening into the windpipe and is called " Adam's apple." 
The larynx is formed by several large pieces of cartilage 
lined with a mucous membrane. On the inside of the larynx 
project two folds of elastic tissue which are called the vocal 
cords. 
Figure 205. -The Lungs and 
Heart. 
Note the branches of the 
bronchus and blood vessels on 
the right side. BREATHING 
287 
203. Breathing. - The lungs are elastic and can be 
squeezed like a sponge. Inspiration is the term applied to 
the taking of air into the lungs, and expiration to the forcing 
out of air. 
When air is drawn into the lungs, the chest expands by 
pulling the ends of the ribs upward and outward and by pull- 
ing down the diaphragm, the horizontal muscle which divides 
the lung cavity from the abdomen (Figure 186). Thus the 
chest cavity is enlarged and air is sucked into the lungs. 
The process of inspiration requires that the muscles of the 
Figure 206. - Voice Box or Larynx. 
chest do a considerable amount of work, as the cartilages 
attached to the ribs must be bent and the walls of the abdo- 
men stretched. 
In expiration the air passes out gently. The muscles that 
have caused the expansion of the chest relax and the ribs 
sink back into their former position. As the muscles of the 
abdomen contract, the organs in the abdominal cavity press 
upward and the diaphragm arches forward into the chest 
cavity. 
When we breathe naturally only a small part of the air in 
the lungs is exchanged at each inspiration and expiration, but 288 
RESPIRATION 
by breathing deeply a few times we can remove the larger 
part of the air from the lungs and replace it with fresh air. 
The natural rate of breathing is about eighteen times a 
minute, but the rate is higher in persons with a small lung 
capacity. Exercise increases the rate of breathing. Ex- 
plain why exercise out-of-doors is better for us than that 
taken indoors. 
All the air passages are lined with cells bearing numerous 
cilia (Figure 207), and these cilia are constantly in motion. 
Their work is to carry toward the mouth the particles of dust 
and other foreign materials brought in by the air. This 
foreign matter is removed when we cough 
or clear our .throats. Explain why clean 
air is better for us than foul air. 
The purpose of respiration is to take 
the air, rich in oxygen, into the lungs, 
where the oxygen passes into the blood 
as the capillaries penetrate the walls of 
the lungs, and to give off the waste car- 
bonic acid gas that has come from the 
cells of the body. Thus respiration is a 
twofold process, the supplying of the 
living cells of the body with oxygen and the removal of 
wastes from the blood. The air that is inhaled contains 
a small amount of carbonic acid gas, but the proportion 
is much smaller than in the exhaled air. It is well to keep 
in mind that green plants are constantly, during the daytime, 
using carbonic acid gas in manufacturing starchy foods and 
giving off oxygen so that the air is being made better for 
animals and man to breathe, while at the same time these 
green plants are storing up food for animals, including man. 
204. Hygienic Habits of Breathing. - The passages of 
the nose occupy a much larger space than one would suppose. 
This subdivided surface in the nasal passages is covered 
with a mucous membrane. The cells in this membrane are 
Figure 207. - Cili- 
ated Epithelium. 
Such cells line our 
bronchial tubes. Ex- 
plain their work. SYSTEMATIC EXERCISE 
289 
richly supplied with blood, which enables them to secrete 
a liberal supply of moisture. We become more conscious of 
their work when we first come down with a cold and the nose 
" runs." When we have a cold, these cells are more active 
than usual. 
As the aii passes through the nasal passage three things 
usually happen: First, a large proportion of the dust par- 
ticles in the air are deposited; second, the air is warmed 
nearly to blood heat; and third, it receives moisture from 
the mucous membrane. Each of these three changes is 
important. If we breathe through the mouth, these changes 
have to take place in the passages of the lungs, where the 
accumulation of dust particles and disease germs is injurious. 
205. Systematic Exercise. - If we keep our bodies in 
correct posture, but little need be said about breathing exer- 
cises. A great deal has been written about the value of deep 
breathing, but we all know that it is not necessary to con- 
tinue to do this all the time. There is no question that it is 
desirable to be able to breathe deeply and to have a large 
chest if for no other reason than that it gives the heart more 
room to do its work. Lazy habits of breathing tend to 
weaken the muscles of inspiration, and the result is that only 
a part of the lungs is used. Regular exercises, then, which 
develop the chest muscles are valuable in breathing. In a 
well-developed body, involuntary breathing suffices for every- 
thing but unusual activity, such as running and similar 
strains, which demand that the body be supplied with more 
oxygen. 
The effect of proper exercises on the chest, then, is to de- 
velop the muscles thus used. The chest is larger under such 
conditions and there is more room for the lungs to expand. 
They are able to hold more air. This in turn renews the 
air more frequently in the air sacs, which are not supplied with 
muscles but consist of a very simple layer of cells. Exercise 
has no effect on their size and activity. Muscles, also, are 290 
RESPIRATION 
present in the walls of the lungs, tracheae, and bronchi and 
indolent breathing leaves parts of the lungs inactive so that 
the muscles in these portions become sluggish. Here again 
exercise plays an important part in helping the lungs do 
their best work. 
206. Tight Clothing and Breathing. - The normal move- 
ments in breathing permit the ribs to be elevated as air is 
pumped into the lungs. Anything that interferes with these 
normal movements makes it more difficult to get the re- 
quired amount of oxygen into the lungs. Wearing tight 
clothing around the chest retards these natural movements 
and prevents the strong development of the muscles of this 
region. The continued practice of wearing such clothes 
makes one short of breath and prevents any great amount of 
muscular activity. Unless loose clothing is worn during ex- 
ercise, the muscles used in respiration are not benefited by 
the exercise. 
207. Suffocation and Artificial Breathing. - When the 
body is deprived of a sufficient supply of oxygen, suffoca- 
tion results. This may be brought about by confining a 
person to a small, air-tight inclosure, by inhaling poisonous 
gases, and by drowning. Whatever may be the cause of 
suffocation, the person should be at once brought into 
fresh air. 
Persons suffering from suffocation can often be revived 
by artificially moving the muscles of the chest so as to imi- 
tate as closely as possible the normal breathing movements. 
There are several well-known methods, of which the Schaefer 
method of artificial breathing is regarded as one of the best. 
The patient is placed with his face downward, having the 
forehead resting on one arm. The person attempting to 
stimulate natural breathing should get astride of the patient's 
legs and place his hands on each side of the patient's body 
opposite the lower ribs. He should press down and in and 
then relax the pressure. This simple series of movements USES AND NECESSITY OF OXYGEN 
291 
should be repeated about fifteen times a minute. The pres- 
sure thus exerted will help to force the water from the lungs 
in the case of drowning. It imitates, as well as one can, the 
natural breathing movements, and should be continued, if 
necessary, for several hours. 
208. Uses and Necessity of Oxygen. - It has been re- 
peatedly stated in describing the life functions of animals, and 
will be repeated in the description of the life of plants, that 
oxidation is one of the fundamental and vital processes. The 
life activities of man conform to those in animals and plants. 
His body is composed of millions of cells, each one of which 
must have oxygen in order to live. The blood vessels (see 
page 349) carry the oxygen to the cells. In the lungs, the 
taking up of oxygen is important only to supply the 
blood with enough oxygen to furnish the necessary amount 
for these numerous cells. When we undertake excessive 
exercises, the oxygen in the tissues becomes exhausted and 
we have to stop and rest - in fact, we wait for a fresh supply 
of oxygen to be carried to the cells. At the same time one 
must keep in mind the importance of getting rid of the waste, 
carbon dioxide, as its accumulation in the body is a large 
factor in fatigue. 
We get an idea of the value of oxygen if we study moun- 
tain sickness. The amount of oxygen at high elevations is 
much less than on lower levels, and is especially noticed by 
those who go to great heights either on lofty mountains or in 
airplanes. This lack of oxygen usually tends to lessen the 
amount taken in by the lungs and the result is felt in the 
nervous system. When there is a deficiency in the supply 
of oxygen there is one outstanding result, the formation of 
lactic acid. This is usually followed by nervous irritation, 
sickness, and pain in the head. The result is similar to that 
produced by excessive indulgence in alcohol. People who 
undertake to see how high they can go in an airplane take a 
supply of oxygen with them. 292 
RESPIRATION 
209. Ventilation. - Associated with the question of 
breathing is the problem of supplying our homes with fresh, 
pure air. Every one feels better after a walk in the open air. 
To have plenty of fresh air in our rooms and to remove the 
carbon dioxide is a hard problem. One of the difficulties is 
to get the air down to 
the breathing line and 
not stir up the dust on 
the floor. Figures 208 
and 209 show the best 
plans for ventilating a 
room. They are adapted 
to the two common meth- 
ods of heating, hot air 
and steam or hot water. 
They show the course 
taken by the currents of 
fresh air entering the 
room at night with the 
window open, and in the 
daytime with it shut. 
210. Air Currents, 
Temperature, and Hu- 
midity. - The biological 
explanation of air cur- 
rents and humidity cen- 
ters in our understanding 
of temperature. Wher- 
ever man is found, whether he lives in the icebound North or 
the Tropics, in winter or summer, his temperature remains 
the same, independent of external conditions; in short, he 
is warm-blooded. All of the life processes contribute to 
maintaining this condition, and it is not correct to say 
that oxidation alone is responsible. When we speak of 
the temperature of man, reference is made to the internal 
Room w-Dayt/MR 
/mmect n^r/f/6. 
Figure 208. - Hot-air Heating. 
By Earl Hallenbeck. AIR CURRENTS, TEMPERATURE, HUMIDITY 
293 
temperature and not to that of the surface of the skin. 
The temperature of the skin is influenced by the varying 
changes in the air, and does not approach that of the blood 
except when the blood vessels beneath the skin become en- 
larged and the heat is prevented from escaping into the air. 
The temperature of 
the body is measured by 
the clinical thermometer. 
Some such instrument is 
necessary because we 
cannot tell by our feel- 
ings what our tempera- 
ture really is. In the 
case of such diseases as 
typhoid and other fevers, 
the normal temperature 
of 98.6 degrees Fahren- 
heit, or 37 degrees Centi- 
grade, is increased. Our 
bodies are burning up 
more energy than they 
should, so that it becomes 
very important to know 
their exact temperature. 
There is a slight daily 
fluctuation in the tem- 
perature of a well person. 
It is lowest early in the 
morning and usually highest sometime in the afternoon or 
early evening. 
We are constantly giving off heat from our bodies. We say 
that the brick wall or stone steps are cold, that iron is colder 
than wood, but we really mean that heat passes more rapidly 
from the skin to one substance than to another. Heat also 
passes from the body into the air. One of the conditions 
RooM/A/myr/Me 
D/^cr 
Figure 209 -Steam Heating. 
By Earl Halienbeck. 294 
RESPIRATION 
that hinders this escape of heat is the amount of moisture in 
the air, its humidity. If the air that comes in contact with 
the skin holds all of the water that it can, then it will not 
take up any more water unless it becomes somewhat heated. 
When there is a great deal of water in the air, we speak of 
high humidity. If the humidity is high and at the same time 
the temperature is above normal as sometimes happens in the 
summer, then we are very uncomfortable. Under such a com- 
bination of conditions, the relief from the high temperature is 
hindered because we do not give off as much heat from our 
bodies, that is, the saturated air does not take up heat as fast. 
The perspiration that escapes from the body usually 
evaporates so rapidly that we are not aware of it. This is 
one means by which our feeling cold or warm is regulated. 
Air currents coming in contact with the skin assist in remov- 
ing the heat of the body. In a smaller way, the same re- 
sults are brought about in exercise of all kinds. When we 
are resting, the air close to the skin and under our clothes is 
warm and heavily laden with moisture. Just as soon as the 
parts of the body are moved in running, riding, and even 
walking, a breeze is felt. One can stand still and swing the 
arms and the air next to the skin is changed. The air next 
the body, which has become warm and moist, is replaced a 
moment later by cooler and drier air. 
211. Clean Air. - A great deal has been written about 
11 clean air," " bad air," 11 stuffy air," and many experiments 
have been made to see just what makes us uncomfortable. 
When a room seems stuffy or close our discomfort is usually 
due to overheating of the skin. The surface of the body is 
generally kept comfortable by the air currents which pass 
over it and aid in the evaporation of perspiration. In a 
confined space, where there is a lack of movement in the air 
it tends to become warm and humid. Thus moisture is not 
taken promptly from the skin and its temperature rises. 
The most effective precaution to be taken is to keep a room DISEASES OF THE RESPIRATORY TRACT 
295 
comfortably cool and to have some circulation of the air. 
This is the reason that an electric fan adds to our comfort 
though the air has not been changed so far as the oxygen and 
carbon dioxide are concerned. 
212. Diseases of the Respiratory Tract. - The most 
common of these diseases is a cold located in the nose and 
throat. The nasal passages become clogged with mucus 
which contains many germs. These germs are widely dis- 
tributed in sneezing. 
Diphtheria is a germ disease which is .located in the throat 
and nose. For many years diphtheria was one of the most 
deadly of our diseases, but through the use of the diphtheria 
antitoxin the danger has been greatly reduced. 
Bronchitis and pneumonia are germ diseases located in 
the bronchial tubes of the lungs. Pneumonia is a frequent 
cause of death, especially among aged people. 
Tuberculosis of the throat and lungs is a widely distributed 
disease which causes many deaths each year. See page 408. 
Adenoids are the result of an enlargement of the pharyn- 
geal tonsil. The commonest result is the stopping of the 
nasal passage. Almost all mouth-breathing children have 
adenoids. These should be removed not only because they 
prevent the natural use of the nasal passage but because they 
often cause deafness. 
OUTLINE 
Respiration defined 
Human organs 
Nose 
Windpipe 
Lungs 
Breathing 
Inspiration 
Expiration 
Hygienic habits 
Exercise 
Tight clothing 
Suffocation 
Artificial breathing 
Schaefer method 
Necessity of oxygen 
Mountain sickness 
Ventilation 
Air currents 
Temperature 
Humidity 
Clean air 
Diseases 
Of throat 
Of lungs 296 
RESPIRATION 
SUMMARY 
All living things require oxygen, which in man and the higher animals 
is carried by the blood to the cells of the body. The parts which man 
uses in breathing are more highly developed than in any other animal. 
The voice box, the larynx, by means of which he is able to make a wide 
variety of sounds, is located at the top of the trachea. Oxygen plays a 
most important part in keeping the body of man warm through oxida- 
tion. Proper ventilation enables the body to secure sufficient oxygen 
and so assists in fighting the various diseases of the respiratory tract. 
QUESTIONS 
Compare the organs of respiration in the animals that you have 
studied such as crayfish, fish, frog, and man. In what important point 
do all agree? What is the difference between gills and lungs? Where 
do air-breathing animals get their oxygen? Where do water-breath- 
ing animals get their oxygen? What is the importance of exercises in 
developing our chest muscles ? In making us more comfortable ? CHAPTER XIX 
FOODS, STIMULANTS, AND NARCOTICS 
For what can powergive more than food and drink ? 
- Dryden 
213. What Makes Us Go? - One of childhood's earliest 
questions suggested by the first mechanical toy is, " What 
makes it go? " Later the same query is applied to his own 
body. We are still asking, " What makes us go? " Nearly 
every magazine has a patented food preparation that guar- 
antees to make man go better than do the ordinary foods. 
There is but one method of approaching this problem, and 
that is through a study of the relation of energy to life 
processes. What are our resources? Under what limita- 
tions and regulations can we use these resources? 
The body goes because it is furnished with energy from 
the food eaten. The source of the energy for bodily move- 
ment, growth, and repair of tissue is in the food molecules, 
which in turn derive their energy from the process by which 
they are manufactured. Review the significance of photo- 
synthesis (page 37) in this connection. 
214. Nutrients in Common Foods. - The nutritive ma- 
terials produced and consumed fall into the following classi- 
fication : 
(a) Primary Foods. - These include (1) all plant materials 
used as human foods (potatoes, corn, berries), and (2) all 
animal products (fish, oysters) where the animal gets its 
nourishment from some source other than primary feeds and 
fodders. 
297 298 
FOODS, STIMULANTS, AND NARCOTICS 
Primary feeds and fodders are the plant materials used 
for the nourishment of domestic animals and derived from 
harvested grains and manufactured feeds. 
(&) Secondary Foods. - These consist of all edible parts and 
products of animals which have been nourished with the 
primary feeds and fodders (honey, eggs, milk, meats). 
Figure 210. - School Children Raising Primary Foods. 
215. Food. - Food may be defined as that which when 
taken into the body builds up tissue or yields energy. Foods 
are classified as proteins (pre'te-ms), carbohydrates (kar- 
bo-hi'drats), fats, mineral matter, and vitamins (vi'-ta-mms). 
This classification is made whether we study the foods of a 
plant, an animal, or of man. Scientists are able to tell to 
which class meat, bread, oatmeal, milk, and all other foods 
belong by finding out the chemical composition of each. 
Definite chemical tests tell us to which of these classes 
any given article of food belongs. In general the proteins and 
minerals are necessary for the growth and the repair of the FOOD 
299 
body; the carbohydrates and fats furnish heat to keep the 
body warm and energy for muscular work; the vitamins are 
body-regulators. The unused fat is stored up as fatty tissue. 
All classes of food are found in the various foods obtained 
from plants. Some, like honey, are nearly pure carbohy- 
drate, while the English walnut contains, in addition to fat, 
a large quantity of plant protein. Animal foods can furnish 
us with only proteins and fats. In primitive times man used 
a restricted diet and led an active out-of-door life. To-day 
man spends much of his time indoors and lives on a mixed 
and varied diet. The question of how much to eat is a 
modern problem, and on its solution depend our health, 
length of life, and energy for work. 
Edible portion 
e.g.,flesh of meat, yolk and 
white of eggs, wheat, flour, 
etc. 
Water. 
Protein. 
Food as 
purchased 
contains 
Nutrients 
Fats. 
Carbohydrates. 
Mineral matter. 
Vitamins. 
Refuse 
e.g., bones, entrails, shells, brain, etc. 
Alcohol is made up of carbon, hydrogen, and oxygen. All 
proteins contain nitrogen in addition to these three. Because 
alcohol contains no nitrogen, it cannot be used as a food. 
USES OF NUTRIENTS IN THE BODY 
Protein Forms tissue 
e.g., white (albumen) of eggs, 
curd, casein (ka'sS-In) of milk, lean 
meat, gluten of wheat, etc. 
Fats Are stored as fat 
e.g., fat of meat, butter, olive 
oil, oils of corn and wheat, etc. 
Carbohydrates Are transformed into fat 
e.g., sugar, starch, etc. 
All serve as 
fuel to yield 
energy in the 
form of heat 
and muscular 
power. 
Mineral matter (ash) 
e.g., phosphates of lime, 
potash, soda, etc. 
Shares in forming bone, 
assists in digestion, etc. 
Vitamins found in 
milk, eggs, meat, fruit, 
vegetables, and whole grains 
Help keep people 
well and promote the 
growth of children. 300 
FOODS, STIMULANTS, AND NARCOTICS 
DAIRY COWS 
NUMBER ON FARMS AND RANGES, 
APRIL 15. 1910 
I DOT = 1.000 
Figure 211. - Distribution of Dairy Cows in the United States. MILK 
301 
Economy in the Purchase of Foods. - Of course it is expen- 
sive to buy fresh peaches or strawberries at Christmas time. 
But by purchasing fruits and vegetables which are " in 
season," and by studying the local markets to see what is 
raised in the neighborhood, it is possible to secure fresh ma- 
terials for a well-balanced diet at a reasonable price. 
216. Milk. - Milk and cream make up about one sixth 
of the weight of all of the food eaten by the average American 
family. Wherever conditions are favorable for cattle raising 
we find the inhabitants using cow's milk, but in those regions 
of the world where cows do not thrive, such as in the hilly 
districts of Europe, goat's milk is used. In some parts of 
India buffalo's milk is common, while in South America the 
llama furnishes the milk. Camel's milk in desert countries 
and mare's milk on the steppes of Russia are as natural to 
the inhabitants of these places as cow's milk is to us. 
Average Composition of Milk of Various Kinds 
Kind of Milk 
Water 
Protein 
Fat 
Car- 
bohy- 
drates 
(Milk 
Scgar) 
Min- 
eral 
Matter 
Fubl 
Value 
per 
Pound 
Casein 
Albu- 
min 
Total 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Per ct. 
Calories 
Woman . . . 
88.3 
- 
- 
1.2 
3.3 
7.0 
0.3 
285 
Cow .... 
87.0 
2.8 
0.5 
3.3 
4.0 
5.0 
.7 
315 
Croat .... 
85.7 
3.5 
1.0 
4.5 
4.7 
4.4 
.8 
355 
Sheep .... 
81.9 
- 
- 
5.3 
7.3 
4.7 
.9 
480 
Buffalo (Indian) 
82.2 
4.3 
.5 
4.8 
7.5 
4.8 
.8 
480 
Camel.... 
87.1 
3.5 
.4 
3.9 
2.9 
5.4 
.7 
285 
Llama .... 
86.6 
3.0 
.9 
3.9 
3.2 
5.6 
.8 
305 
Reindeer . . . 
67.2 
8.4 
1.5 
9.9 
17.1 
2.8 
1.5 
930 
Mare .... 
90.6 
1.3 
.8 
2.1 
1.1 
5.9 
.4 
190 
Ass 
90.1 
.8 
1.1 
1.9 
1.4 
6.2 
.5 
205 
From U. S. Department of Agriculture, Farmers' Bulletin No. 1359. 
The milk from all these animals is similar except in taste. 
There is a large per cent of water in milk. On the average, 
commercial milk contains 87 per cent of water and 13 per 
cent solids. The solids consist of proteins, carbohydrates, 302 
FOODS, STIMULANTS, AND NARCOTICS 
fats, and a variety of mineral substances. The amount of 
these several products is well shown in the previous table. 
Milk is unlike most of our foods because it contains no 
refuse or indigestible material. Milk is valuable, then, 
because, first, it contains materials that children need for 
growth ; second, materials that young and old alike need for 
the repair of the body machinery, and third, materials that 
all need for fuel, to provide them with heat and with the 
energy necessary for work. We should not make the 
mistake, however, of thinking that because milk has these 
valuable ingredients that it can serve satisfactorily as the only 
food for a grown person or even a child after the nursing age. 
One would need to drink five or six quarts a day to meet the 
needs of school age, and this quantity would supply too much 
protein. Iron also is needed in greater abundance than is 
furnished by milk. Other foods, therefore, are necessary to 
supplement milk. 
217. Green Vegetables and Fresh Fruit. - While milk is 
especially valuable for the variety of nutrients it contains, 
the importance of vegetables and fruits should not be over- 
looked. Green vegetables contain a large proportion of 
mineral matter. For very young children, spinach, as- 
paragus tips, string beans, and peas, when well cooked and 
mashed, are highly nutritious. For older children and 
grown-ups, potatoes, beets, carrots, cauliflower, and squash 
are valuable. 
Fresh fruits are especially good for children. There is 
much truth in the old saying, " an apple a day keeps the 
doctor away." It is now possible to secure apples, oranges, 
bananas, and many other delicious fruits at almost any sea- 
son of the year. 
218. Meaning of Calorie. - Heat is a form of energy, and 
one of the reasons for taking food is to keep up the supply of 
this energy. The more work a person does the more energy 
he uses, but even a resting body uses some energy, for the DIET FOR DIFFERENT OCCUPATIONS 
303 
heart beats and the muscles of the chest move. The amount 
of this form of energy a person uses is measured by a unit 
of heat named the Calorie (kal'Ori).1 A Calorie represents 
the amount of heat required to raise the temperature of a pint 
of water about four degrees Fahrenheit. A man in rising 
from a chair, walking eight feet, and returning to the chair 
uses about one Calorie of energy. 
The term Calorie just defined is now used throughout the 
civilized world as the common unit of measurement for food 
energy. Through the studies of experts it has been deter- 
mined how many Calories are necessary to keep the human 
body from starvation, how many more must be added if 
the body is to do light physical work, and how many more 
if heavy manual labor is done. 
219. Diet for Different Occupations. - Man's food re- 
quirement varies according to occupation and climate. 
One must keep in mind that our bodies require energy to 
grow new cells and to keep the old ones in repair; to keep the 
body at a constant temperature winter and summer; and 
to furnish energy for muscular activity, which often requires 
more energy than to carry on growth and maintain a constant 
temperature. To meet these needs of every human being 
a variety of foods is needed. 
More energy is required in an active occupation and more 
heat in a cold climate. The Calorie is the unit for measuring 
the heat which is a form of energy. The daily Calorie needs 
for certain persons are approximately: 
For a workingman 3500 to 4000 
For an active woman 2800 to 3000 
For a sedentary man 2200 to 2800 
1 Note that this Calorie should always be spelled with a capital C. This 
is to distinguish it (the greater Calorie) from the lesser calorie, which is used 
in physics as the unit of heat. The lesser calorie is the amount of heat that 
will raise one gram of water one degree centigrade. The greater Calorie is 
equal to 1000 lesser calories. 304 
FOODS, STIMULANTS, AND NARCOTICS 
For a sedentary woman 1800 to 2300 
Youth 14 to 16 years 1500 to 3200 
Active soldier 4000 
220. Vitamins. - This word is so new that it is found only 
in recently published dictionaries. From 1917 on there 
have been numerous scientific contributions and a few books 
on the subject of vitamins. The heralded importance of 
Courtesy Omaha Chamber of Commerce. 
Figure 212. - Flouring-mill Where Wheat Is Turned into Flour. 
One of these large mills in Minneapolis has the equipment to turn out 
sixteen thousand barrels of flour every twenty-four hours. 
these substances as a necessary part of our foods and as a 
protection against certain diseases was quickly taken up by 
the manufacturers of special food-products, until one hears 
this technical term used on every side. 
The word vitamin was coined by a Polish scientist, Casimir 
Funk, who believed that there was a special vital substance 
in foods that was related somehow to the proteins. As we 
have come to learn more about these mysterious bodies, the VITAMINS 
305 
word vitamin has ceased to have its first meaning but is re- 
tained because no better term has been suggested to take 
its place. So for the present we will use the expression vita- 
min A, vitamin B, and vitamin C for the three best known 
vitamins. 
"A" 
"B" 
"C" 
"A" 
"B" 
"C" 
Bread, white (water) 
? 
t 
Tomatoes (raw or 
canned) 
tt 
ttt 
ttt 
" " (milk) 
t 
t 
? 
Beans, kidney . 
* 
ttt 
* 
" whole wheat 
(water) .... 
t 
tt 
? 
" navy . 
" string (fresh) 
* 
tt 
ttt 
tt 
tt 
Bread, whole wheat 
(milk) .... 
tt 
tt 
? 
Cabbage, fresh, raw 
" cooked 
t 
t 
ttt 
tt 
t? 
t? 
Barley (whole) . . 
t 
tt 
- 
Carrots, fresh, raw 
tt 
tt 
tt 
Corn, yellow . . . 
t 
tt 
- 
" cooked . 
tt 
t 
t 
Oats 
t 
tt 
- 
Cauliflower . 
t 
tt 
t 
Meat, lean . . . 
- to + 
t? 
t? 
Celery 
* 
t 
* 
Beef fat .... 
t 
- 
- 
Cucumber 
* 
t 
* 
Mutton fat . . . 
t 
- 
- 
Dandelion greens . 
tt 
tt 
t 
Pig kidney fat . 
tt 
- 
- 
Eggplant, dried . . 
* 
tt 
* 
Oleomargarine . 
t 
- 
- 
Lettuce . . . . 
tt 
tt 
ttt 
Liver 
tt 
tt 
t 
Onions 
♦ 
tt 
tt 
Kidney .... 
tt 
tt 
t? 
Parsnip . . . . 
- ? 
tt 
* 
Brains 
t 
tt 
t? 
Peas 
tt 
tt 
t? 
Sweetbreads . 
Fish, lean .... 
t 
t 
t 
* 
* 
Potatoes (boiled 15 
min.) . . . . 
* 
tt 
t? 
" fat .... 
" roe .... 
t 
t 
t 
tt 
* 
t? 
Potatoes (boiled 1 
hour) . . . . 
* 
tt 
t? 
Milk, fresh 
ttt 
tt 
tv 
Potatoes (baked) . 
* 
tt 
t 
" condensed 
ttt 
tt 
tv 
Sweet potatoes . . 
tt 
t 
* 
" dried (whole) 
ttt 
tt 
tv 
Radish 
* 
t 
* 
" skimmed 
t 
tt 
tv 
Rutabaga .... 
- ? 
tt 
ttt? 
Buttermilk 
t 
tt 
tv 
Spinach, fresh . 
" dried . 
ttt 
ttt 
* 
Cream 
ttt 
tt 
tv 
ttt 
tt 
* 
Butter 
ttt 
- 
- 
Squash, Hubbard . 
tt 
* 
* 
Cheese 
tt 
* 
* 
Turnips . . . . 
-? 
tt 
* 
Cottage cheese . 
t 
* 
* 
Apples 
t 
t 
t 
Eggs 
tt 
t 
t? 
Bananas . . . . 
t? 
t? 
t 
Almonds .... 
t 
t 
♦ 
Grape juice . . . 
* 
t 
t 
Coconut .... 
t 
tt 
* 
Grapefruit 
* 
tt 
tt 
Hickory nuts . . 
* 
tt 
* 
Lemon juice . 
* 
tt 
ttt 
Peanuts .... 
t 
tt 
* 
Orange juice . . 
t 
tt 
ttt 
Pecans 
* 
t 
* 
Prunes 
* 
t 
- 
Walnuts .... 
* 
tt 
* 
Raspberries (fresh 
or canned) . . . 
* 
* 
ttt 
Vitamins in Foods 
t contains the Vitamin 
tt good source of the Vitamin 
ttt excellent source of the Vitamin 
- no appreciable amount of the Vita- 
min 
1 doubt as to presence or relative 
amount 
* evidence lacking or insufficient 
V variable 306 
FOODS, STIMULANTS, AND NARCOTICS 
In our regular diet these several vitamins are always 
present, for beef, mutton, liver, milk, germinated cereals, 
fresh cabbage, tomatoes, string beans, carrots, and lettuce 
contain all three vitamins; while eggs, whole wheat, beans, 
spinach, and nuts are especially rich in vitamins A and B. 
Onions, lemons, oranges, raspberries, and apples contain 
vitamin C. This list of common foods which contain an 
adequate supply of vitamins for all ordinary conditions, 
should convince us that patented preparations are wholly 
unnecessary. 
What is the use of vitamins in our diet? This question 
cannot be answered satisfactorily. Three possible explana- 
tions have been offered: (1) that vitamins aid in digestion; 
(2) that they stimulate activity in the cells; (3) that they 
supply certain chemical groups that the body needs but can- 
not itself manufacture. 
Two diseases are now believed to be definitely identified 
with the deficiency of vitamins in the diet. Beriberi, a 
disease involving a general paralysis of the system, is due to 
the lack of vitamin B; while scurvy is caused by lack of 
vitamin C. 
The previous table gives a list of our principal articles of 
food and shows the different vitamins present in them. 
221. Food Groups. - In the classification of foods given 
on page 27 into proteins, carbohydrates, fats, mineral matter, 
and vitamins, the arrangement is made upon their chemical 
composition because foods do not grow as proteins or fats. 
The foods that we eat are often composed of all these. There 
are five food groups which are arranged chiefly on the pro- 
portionate amounts of proteins, sugars, or fats. These are 
shown in the table on the following page. 
A well-balanced diet contains a proper proportion of these 
five food groups. One food from each of these groups should 
be used each day. It is impossible to prescribe an exact 
diet for every one, as it should vary with the age, weight. FOOD GROUPS 
307 
health, occupation, and location of the individual. The 
variation, however, is largely in the quantity rather than in 
the kind used. 
The following table shows the food groups and their rela- 
tive importance, together with the daily amount needed by 
the average man. 
Food Groups 
Purposes 
Amount Needed Daily 
by a Man at Moderate 
Muscular Work 
No. 1. - Fruits and 
vegetables. 
To give bulk and to 
insure mineral and 
body-regulating 
materials. 
14 to 3 pounds. 
No. 2. - Medium-fat 
To insure enough pro- 
8 to 16 ounces (4 
meats, eggs, cheese, 
dried legumes and 
similar foods, milk. 
tcin. 
ounces of milk count- 
ing as 1 ounce). 
No. 3. - Wheat, corn, 
oats, rye, rice, and 
other cereals, pota- 
To supply starch, a 
8 to 16 ounces (in- 
cheap fuel, and to 
creasing as foods 
supplement the pro- 
from Group 2 de- 
toes, sweet potatoes. 
tein from Group 2. 
crease). 
No. 4. - Sugar, honey, 
sirup, and other 
foods consisting 
chiefly of sugar. 
To supply sugar, a 
quickly absorbed 
fuel, useful also for 
flavor. 
H to 3 ounces. 
No. 5. - Butter, oil, 
and other foods con- 
sisting chiefly of fat. 
To insure fat, a fuel, 
which also adds to 
the richness of food. 
14 to 3 ounces. 
It is difficult for some of us to realize that our foods fall 
into such few groups as in the table above, since nearly every 
magazine that we examine is advertising some new break- 
fast food or some special brain food. For many of us a 
variety in our daily menu has become almost a necessity and 
we think ourselves restricted if limited to five groups. This 
is equally true of those who claim to be vegetarians as well 
as those who are accustomed to derive their protein energy 
and carbohydrate energy from animal as well as plant foods. 308 
FOODS, STIMULANTS, AND NARCOTICS 
The following table 1 shows the consumption of proteins in 
the United States. Why should the large number of statis- 
Group 
Average for Six Years, 
1911-12 to 1916-17 
For 1917-18 
Absolute 
Consump- 
tion of 
Protein 
(Metric 
Tons) 
Per- 
centage 
Con- 
sump- 
tion 
Cumu- 
lated Per 
Cent 
Absolute 
Consump- 
tion of 
Protein 
(Metric 
Tons) 
Per- 
centage 
Con- 
sump- 
tion 
Cumu- 
lated Per 
Cent 
Grains . . . 
1,316,140 
36.01 
36.01 
1,303,348 
34.44 
34.44 
Meats .... 
964,117 
26.38 
62.39 
945,277 
24.98 
59.42 
Dairy products . 
744,784 
20.38 
82.77 
788,969 
20.85 
80.27 
Poultry and eggs 
246,178 
6.74 
89.51 
285,413 
248,772 
7.54 
87.81 
Vegetables . 
214,404 
5.87 
95.38 
6.57 
94.38 
Fish .... 
84,852 
2.32 
97.70 
102,022 
2.69 
97.07 
Oils and nuts 
57,839 
1.58 
99.28 
85,021 
2.25 
99.32 
Fruits .... 
24,965 
.69 
99.97 
23,621 
.62 
99.94 
Oleomargarine . 
838 
.02 
99.99 
1,808 
.05 
99.99 
Sugars. . . . 
455 
.01 
100.00 
439 
.01 
100.00 
Total . . . 
3,654,572 
100.00 
- 
3,784,690 
100.00 
-- 
Figure 213. - Table of Protein Consumption. 
tics in Figures 213 and 214 and those in the tables on pages 
310 and 311 be included in an elementary text-book of biol- 
ogy? If any one had been confronted with the question, 
"How much corn, or oats, or molasses, or fish, or milk, or 
nuts, or fruit is consumed each year in the United States as 
food, " no one could have given more than a rough guess until 
Professor Raymond Pearl of the New School of Hygiene of 
the Johns Hopkins University made this exhaustive study. 
The question is a fair one and it is very important that we 
be able to give a correct answer. The study of all the foods 
used by man has not been made; but for some twenty of the 
great groups we are in a position to present such tables as 
these, which are more accurate than any others ever compiled. 
1 The following four tables are taken from the Proceedings of the Ameri- 
can Philosophical Society, Volume LVIII, November 3, 1919. FOOD GROUPS 
309 
On the basis of such figures it is possible to discuss intelli- 
gently the relative importance of the great groups, like the 
Group 
Average for Six Years, 
1911-12 to 1916-17 
For 1917-18 
Absolute 
Consump- 
tion of Fat 
(Metric 
Tons) 
Per- 
Cent- 
age 
Con- 
sump- 
tion 
Cumu- 
lated Per 
Cent 
Absolute 
Consump- 
tion of Fat 
(Metric 
Tons) 
Per- 
Cent- 
age 
Con- 
sump- 
tion 
Cumu- 
lated Per 
Cent 
Meats .... 
2,591,613 
50.66 
50.66 
2,602,187 
47.48 
47.48 
Dairy products . 
1,405,918 
27.49 
78.15 
1,505,129 
27.46 
74.94 
Oils and nuts 
623,385 
12.19 
90.34 
781,461 
14.26 
89.20 
Grains . . . 
203,585 
3.98 
94.32 
227,807 
4.16 
93.36 
Poultry and eggs 
173,349 
3.39 
97.71 
175,220 
3.20 
96.56 
Oleomargarine . 
57,965 
1.13 
98.84 
125,024 
2.28 
98.84 
Vegetables . . 
21,126 
.41 
99.25 
27,864 
.51 
99.35 
Fruits .... 
20,242 
.49 
99.65 
17,866 
.33 
99.68 
Fish .... 
18,096 
.35 
100.00 
17,381 
.32 
100.00 
Sugars .... 
0 
0 
100.00 
0 
0 
100.00 
Total 
5,115,279 
100.00 
- 
5,479,939 
100.00 
- 
grains and the vegetables, in the nutrition of a people. We 
can now calculate the total national food bill. 
One of the important conclusions is that the annual con- 
sumption is quite uniform from year to year. No matter 
how much production, nor how much variation there is in 
the exports and imports, the people of the United States 
eat about the same amount each year. 
If these and the other statistics in this remarkable contri- 
bution are studied, it is easily shown just where the proteins, 
fats, and carbohydrates come from. Thus the American 
people get over one half of their protein from animal sources 
exclusive of fish. Such a conclusion indicates the great im- 
portance of maintaining our animal herds intact. Eighty- 
two per cent of the fat comes from animal source; while 
but five per cent of the carbohydrates are of animal origin. 
Figure 214. - Table of Fat Consumption. 310 
FOODS, STIMULANTS, AND NARCOTICS 
The table below shows the consumption of carbohydrates 
in the United States. 
Group 
For the Six Years, 1911-12 
to 1916-17 
For 1917-18 
Absolute 
Consu mp- 
tion of Car- 
bohydrate 
(Metric 
Tons) 
Percent- 
age Con- 
sumption 
Cumu- 
lated Per 
Cent 
Absolute 
Consump- 
tion of Car- 
bohydrate 
(Metric 
Tons) 
Percent- 
age Con- 
sumption 
Cumu- 
lated Per 
Cent 
Grains . . 
9,208,939 
56.1073 
56.1073 
9,291,445 
54.2224 
54.2224 
Sugars . . 
4,193,095 
25.5473 
81.6546 
4,374,194 
25.5266 
79.7490 
Vegetables . 
Dairy 
1,421,851 
8.6629 
90.3175 
1,844,682 
10.7651 
90.5141 
products. 
899,691 
5.4815 
95.7990 
917,169 
5.3524 
95.8665 
Fruits . . 
Oils and 
627,487 
3.8231 
99.6221 
601,350 
3.5093 
99.3758 
nuts . . 
57,097 
.3479 
99.9700 
102,231 
4,717 
5966 
99.9724 
Meats . . 
4,907 
.0299 
99.9999 
0275 
99.9999 
Fish . . . 
Poultry and 
20 
.0001 
100.0000 
25 
.0001 
100.0000 
eggs . . 
Oleomar- 
0 
0 
100.0000 
0 
0 
100.0000 
garine 
0 
0 
100.0000 
0 
0 
100.0000 
Total . . 
16,413,087 
100.0000 
- 
17,135,813 
100.0000 
- 
From time to time in the history of man there have been 
famines. Pharaoh of old directed Joseph to lay up grain 
during the years of plenty for the famine that was to follow. 
In modern times the needs of famine-stricken groups are 
relieved by sending supplies from nations that have plenty 
in their granaries. China grew enough wheat during the 
year of their recent famine to feed every Chinese, but many 
starved because of inadequate transportation facilities. 
During the Great War and in the years immediately follow- 
ing, the world was called on to feed those in need. The first 
question was "How much food is needed?" No one 
knew. Scientific experts had to compile such tables as these 
on pages 308-311 before the question could be answered. FOOD SUBSTITUTES 
311 
The following table shows the consumption of foods in the 
United States, in terms of Caloric value. 
Group 
For the Six Years, 1911-12 
to 1916-17 
For 1917-18 
Absolute 
Consumption 
(Million 
Calories) 
Per- 
centage 
Con- 
sump- 
tion 
Cumu- 
lated 
Per 
Cent 
Absolute 
Consumption 
(Million 
Calories) 
Percent- 
age Con- 
sumption 
Cumu- 
lated 
Per 
Cent 
Grains 
45,057,265 
34.68 
34.68 
45,569,323 
33.31 
33.31 
Meats .... 
28,104,069 
21.63 
56.31 
28,122,722 
20.55 + 
53.86 
Dairy products . 
19,834,010 
15.26 
71.57 
21,010,397 
15.36 
69.22 
Sugars 
17,196,595 
13.24 
84.81 
17,939,129 
13.11 
82.33 
Vegetables . 
6,910,026 
5.32 
90.13 
8,999,132 
6.58 
88.91 
Oils and nuts 
6,269,270 
4.82 
94.95 
8,104,157 
5.92 
94.83 
Fruits .... 
2,862,540 
2.20 
97.15 
2,722,604 
1.99 
96.82 
Poultry and eggs 
2,620,311 
2.02 
99.17 
2,648,262 
1.93 
98.75 
Oleomargarine . 
542,719 
.42 
99.59 
1,170,593 
.86- 
99.61 
Fish .... 
534,509 
.41 
100.00 
533,419 
.39 
100.00 
Total . . . 
129,931,314 
100.00 
- 
136,819,738 
100.00 
- 
222. Food Substitutes. - Foods that can be used in place 
of those that we wish to save are known as food substitutes. 
For example, the substitutes for wheat are corn, oats, rice, 
barley, white and sweet potatoes; while the following can 
be used in place of meat: fish and other sea food, milk, cheese, 
eggs, nuts, legumes, and cereals. Honey, maple sirup, corn 
sirup, sorghum, and molasses are used in place of sugar; 
the substitutes for butter and lard are olive oil, corn oil, 
cotton-seed oil, meat drippings, etc. 
In the study of food substitutes a great deal is said about 
new foods, but there are really no new foods. The use of 
rye flour, corn meal, and such foods, while new to many 
people of this generation, were the most common foods with 
our ancestors as they pioneered and settled the land. We 
are in reality returning to the simpler forms of food rather 
than adding new foods. Find out all that you can about the 312 
FOODS, STIMULANTS, AND NARCOTICS 
different kinds of foods that were used by the early settlers 
in your community. 
223. Food Shortage. - Keeping in mind the important 
fact that all foods have to be grown, it is easy to understand 
how there may be a food shortage. If the men who are 
skilled in raising food were all removed from the farms, the 
storehouses would in a short time be emptied of their supplies, 
Courtesy Omaha Chamber of Commerce. 
Figure 215. - Huge Grain Elevator. 
Here wheat and grains are stored before being made into flour and 
other foods. 
and none would be growing to replace them. This would 
result in a food shortage. With the growth of cities, more 
food has to be collected and transported for the use of their 
populations, none of whom are engaged in the production of 
food, but all of whom require food. 
Some appreciation of the magnitude of this phase of our 
food problem can be gained by learning from your local INCREASING THE FOOD SUPPLY 
313 
dealers where the food used for one day in your home was 
grown. The problem of giving all the people in our country 
enough to eat at reasonable prices is one of very great impor- 
tance and one that you can well afford to study. 
224. Increasing the Food Supply. - Whenever an in- 
creased demand is made upon the total supply of food in a 
nation, as was made upon the United States during the years 
of 1916-1919, attention is directed to two important facts: 
(1) that we are not using all the available foods, as is noted 
by a study of food substitutes; and (2) that measures must 
be employed to increase the total production of food. To 
show that biological principles are the foundation for all 
such studies, three examples only will be given. 
(a) Fish Production. - The first food chosen to take the 
place of meat is fish, because the food value of fish is similar 
to that of meat. In America there are nearly 70 kinds of 
edible salt-water fish and more than 30 fresh-water varieties, 
yet most of us know hardly a dozen. How many different 
kinds of fish have you ever eaten ? It is said that every year the 
fishermen of the Atlantic coast throw away about 10,000,000 
pounds of fish that have a higher nutritive value than the 
famous cod. We are far behind other countries in our use of 
fish. We use about 18 pounds of fish per person each year, 
while England uses about 65 pounds and Canada 57 pounds. 
We should not only eat more fish but study the conditions 
under which fish live in order that fish may become more 
abundant in our fresh-water streams and lakes. Fish freshly 
caught is a great delicacy. Many of our fresh-water lakes 
and ponds could be made to supply an abundance of fish 
food if some intelligent care were taken to supply these ponds 
with the varieties best adapted to live in them. 
Perch, pike, bass, and bullheads have a wide range of adap- 
tation and will thrive in most of our fresh-water ponds. We 
have not as yet begun to utilize properly the larger streams 
of our country, which can be made to support a great number 314 
FOODS, STIMULANTS, AND NARCOTICS 
of food-fish if the water in them is reasonably pure. Where 
the streams are utilized to carry away the sewage of cities 
and towns, the water becomes so polluted that fish cannot 
live in it. 
(6) Improving the Varieties of Animals and Plants. - If we 
compare the domesticated animals and plants in common 
use 20 years ago with those of to-day we note many improve- 
ments. These are due to a large number of experiments that 
have been carried on largely by the United States Depart- 
ment of Agriculture and the many state experiment stations. 
Here new varieties are tested and old varieties improved for 
the benefit of man. The net result of all these experiments 
has been to increase greatly the usefulness of our many 
domesticated animals and plants. The up-to-date farmer 
is thoroughly familiar with the latest discoveries in this field 
and often pays high prices for improved seed or stock in order 
that he may obtain a larger yield or better results. By 
keeping in touch with such improvements, the farmers have 
greatly increased the total food supply. 
(c) War Gardens. - A " war garden " is a garden in a back 
lot or other hitherto waste land which is used for increasing 
food production. In addition to the large number of adults 
who cultivated war gardens during the years of 1917-1918, 
there were approximately one million and a half school 
children enlisted in the United States School Garden Army 
during the summer of 1918. It is believed that an average 
of one fifteenth of an acre per pupil is a conservative esti- 
mate. This would make a total of one hundred thousand 
acres. The average production per acre under intensive 
cultivation at a low estimate ought to be $50, which would 
give a total of fifty million dollars in value. Experienced 
truck gardeners expect to make from $1,000 to $1,200 per 
acre. 
In addition to increasing the general food supply, there are 
two other reasons why the War Garden idea should be per- THE PREPARATION OF FOODS 
315 
petuated. In the first place, the vacant lots of a city or town 
present a more attractive appearance when under cultivation 
than when occupied by weeds and rubbish. Secondly, they 
furnish a splendid opportunity for boys and girls to learn how 
many of their food plants grow and the meaning of labor. 
What other ways can you suggest that will help to increase 
the general food supply? 
225. Public Markets. - These are the places where those 
who raise garden truck, chickens, and other food products can 
bring them and the people can buy directly without paying 
the middleman or the retailer for his services. There is the 
further advantage that such foods are usually fresh. It is 
necessary to regulate the public markets in order that the 
food shall be properly prepared, and correctly weighed or 
measured. These markets are of great advantage to the 
poor people in cities, as they can get more good food at less 
cost than anywhere else. Is the market in your city well 
regulated? What are the rules governing it? 
226. The Preparation of Foods : Cooking. - Some foods, 
such as milk, fruit, and nuts, may be eaten without being 
cooked, but most of our food has to undergo this process 
before it is suitable for eating. As no two kinds of vegetables 
or meats are best cooked in exactly the same way, attention 
should be given to the preparation of food for the table. 
Successful cooking accomplishes three ends. (1) Changes 
are brought about to make the food more digestible, such 
as softening or dissolving it. (2) The nutritious parts are 
carefully saved. (3) The food is made attractive in appear- 
ance and taste, " good to eat." 
Every woman who wishes to have a happy, healthy 
family should make a serious study of cooking. Many of 
the facts about the nutritive elements which foods contain, 
and the many changes which they undergo in cooking, are 
found out by chemists who study them in laboratories. 
It is not necessary for us all to know all these facts, but 316 
FOODS, STIMULANTS, AND NARCOTICS 
a good cook follows the rules and recipes which have been 
made as a result of scientific laboratory studies. 
Bread. - To illustrate the principles involved in cooking, 
let us see what it means to produce a loaf of wholesome bread. 
Flour contains much starch, some sugar, some mineral 
substances known as phosphates, a large quantity of gluten 
(a protein), and some bacteria (tiny plants, see Chapter 
Figure 216. - Raising Wheat for Flour. 
XXIV) which may or may not be of value in making bread. 
When water is added to the flour, it becomes tough and sticky, 
this being a characteristic of gluten, and the most important 
one, so far as the making of bread is concerned. A small bit 
of yeast (a small plant, see Chapter XXXIII) is added to the 
water used in making bread, and the dough is placed where 
it will be neither too hot nor too cold (70°-80° F.). 
The yeast begins to grow rapidly, feeding on the proteins 
of the flour, and as the yeast grows, it acts on the sugar. ADULTERATION OF FOODS 
317 
An enzyme called zymase (zim'as), secreted by the yeast 
plant, breaks the sugar up into carbon dioxide, alcohol, and 
a small quantity of glycerin. The gas tries to escape, but is 
held in by the sticky dough. If the yeast plant is well dis- 
tributed, the gas collects in many small bubbles, and the 
loaf is fine-grained. The alcohol keeps other plants from 
growing there, and also helps to soften the gluten. 
When the loaf is put into the oven, the heat kills the 
yeast plant, drives off the carbon dioxide, and causes the 
alcohol to evaporate. The heat changes the gluten into 
a substance more easily digested and of a more pleasant 
taste. In " salt rising " bread, bacteria from the air, instead 
of yeast cells, form the gas which makes the bread light. 
When a batch of bread " sours," it is usually because harmful 
bacteria get into the dough and grow more rapidly than the 
yeast plants. Sometimes other kinds of yeasts than the 
helpful ones employed in bread-making accidentally get into 
the batch of bread and it spoils as a result. 
During the war we used substitutes in our wheat flour 
with the result that many good cooks were not able to make 
as good bread as usual. This was not the fault of the cooks, 
but was due to the following facts. Although corn, barley, 
and wheat flour contain nearly equal amounts of similar 
proteins, the proteins of corn, barley, and rye do not react 
the same to water and the acids produced during fermenta- 
tion. The dough made from these substitute flours does not 
hold together and is not so distensible as that made from 
wheat flour. These unfavorable conditions of the dough 
can be improved by adding a small amount of what is known 
as the " proteins of serum," a special preparation that is 
in the form of a dry powder. 
227. Adulteration of Foods. - Foods are adulterated 
either by subtracting some of the nutritious parts and sub- 
stituting less valuable parts, or by adding materials which 
cannot act as a food. 318 
FOODS, STIMULANTS, AND NARCOTICS 
The food formerly subject to the most adulteration was 
milk. This adulteration was accomplished by adding water 
to make the milk go farther when being measured out, and 
adding formalin (fdr'ma-lin) to make it keep sweet. 
For a time many of the cereals were adulterated with saw- 
dust, peanut shucks, or bran. Many of the special foods put 
up in packages used to be adulterated, and it would require 
a long description to enumerate all that have been found 
unsatisfactory for food by the Department of Agriculture. 
Pure Food Laws. - The Food and Drugs Act passed 
by the United States Congress on June 30, 1906, requires of 
manufacturers of foods and drugs that a definite statement 
be made as to their composition. A number of regulations 
and rules have been issued from time to time. The last 
was issued June 15, 1917, and related to the marking of 
the quantity of food in packages. Here we find that when 
food is in package form, it must be plainly marked in terms 
of weight, measure, or numerical count on the outside of the 
package. The quantity of the contents so marked shall 
be the amount of food in the package. 
This Act established high standards for many of the com- 
mon and necessary foods of man. Before its adoption there 
was no standard for the manufacturers to go by. One of 
the reasons why it has been so valuable is because it includes 
so many different products. Food standards have been 
established for the following: meats, meat extracts, milk, 
cream, butter, cheese, ice cream, grains, meals, flour, fruits, 
vegetables, flavoring extracts, of which there are twenty- 
four, tea, coffee, cocoa, vinegar, and salt. 
The wide range of patent medicines and drugs comes under 
the influence of this act and we can now read their composi- 
tion on the label. This is a great protection against mis- 
branding and cheating. 
228. Impurities in Water and Milk. - The utmost care 
is taken to protect the water supplies of our cities. The STIMULANTS AND NARCOTICS 
319 
sources are watched and filthy streams are not permitted 
to drain into the reservoirs. If this were not done the water 
might become contaminated with various disease germs, 
notably those of typhoid. If there is any doubt about the 
purity of your drinking water, it should be boiled for thirty 
minutes and cooled before being used. 
The same food substances in milk that render it one of the 
best foods for man make it equally valuable to the large 
number of domestic animals that man uses as his sources of 
meat. On the other hand, there are certain plants, the 
bacteria, that find milk one of the best of foods for their 
growth. Some of these bacteria, such as the typhoid fever 
and diphtheria germs, are very dangerous to our health when 
they chance to be introduced into milk. This is the reason 
that such stringent laws have been passed regulating the 
care of milk that is sold. But these laws which are made to 
give us a high grade of clean milk do not follow the milk into 
the home, where it is often left exposed to contamination. 
The same care that is taken in keeping the milk clean before 
it is bottled should be exercised after the bottle reaches our 
homes. 
229. Stimulants and Narcotics. Drug Habits. - There 
are several substances that are taken in with the food that 
are not regarded as foods in the proper sense. Tea and coffee 
are common stimulants. If correctly made, they are not 
harmful to adults but because of the stimulation are un- 
desirable for children. These common drinks are called 
stimulants because they increase the general activity of the 
body, but they neither build tissue nor release energy, so 
cannot be regarded as foods. Cocoa contains some nutritious 
material. 
Before studying this subject further we must understand 
the meaning of the terms poison, anesthetic (an-es-thet'ik), and 
narcotic. A poison is a substance which when taken into the 
body tends to cause death. Aconite, opium, carbolic acid, 320 
FOODS, STIMULANTS, AND NARCOTICS 
and mercury are all poisons, and when taken in sufficient 
quantities cause death. 
An anesthetic is a substance like ether or chloroform, 
which when breathed into the lungs causes a temporary 
loss of sensation. Unless anesthetics are administered 
properly, they may cause death. 
A narcotic is a substance which causes dullness or stupor, 
and even a temporary relief from pain. 
The narcotics often have a quieting effect which is some- 
times associated with a pleasurable feeling. The common 
narcotics are opium, chloroform, cocain, laudanum, chloral 
hydrate, alcohol, and various patent preparations. 
Many preparations are taken by persons ignorant of the 
fact that they generally contain these harmful drugs. It 
should be sufficient to know that no reputable doctor will 
ever give any of these preparations except in a mild form, and 
in case of extreme pain. No person except a trained physi- 
cian has a right to prescribe drugs; and he only after a knowl- 
edge of the patient's symptoms. Many of these preparations 
affect the heart and blood, and none of them has any bene- 
ficial effect. 
In most cases these drugs are taken at first to narcotize or 
deaden the pain in the nerves. Then their use continues, 
until in a short time a habit is developed. The drug habit is 
more difficult to stop than the alcoholic. None of these 
narcotics has a remedial effect on the cause of the pain. 
They are being used very sparingly nowadays by the best 
physicians because of the lurking danger of the drug habit. 
230. Alcohol.1 - To understand why alcohol is classed as 
a narcotic, we must learn about a substance called lipoid 
1 Those who are interested in making a more critical study of the relation of 
alcohol to the various forms of activity of man and animal should consult the 
two volumes, Physiological Aspects of the Liquor Problem, edited by John S. 
Billings, Houghton Mifflin Co., Boston ; also, The Action of Alcohol on Man, 
by Ernest H. Starling, Longmans Green & Co., 1924; The Defenses of the 
Body against Alcohol, Daniel- Popular Science Monthly, page 159, 1924. ALCOHOL 
321 
(lip'oid: Greek, lipos, fat; eikos, like). Lipoid is very like 
fat except that it contains nitrogen and phosphorus, which fats 
do not. It also mixes with water, and it can make certain 
bodies soluble which are otherwise not soluble. While there 
is no part of any cell in the body that is without this material, 
perhaps the largest accumulation of lipoid is that in the 
nervous system, especially the brain. Each nerve fiber that 
conveys messages into or out of the brain is insulated with 
lipoid and thus the stimuli are prevented from scattering. 
A few years ago scientists discovered that any substance 
that dissolves lipoid, or is dissolved in lipoid, is an anesthetic. 
Chloroform, ether, and all the agents used in modern surgery 
to produce unconsciousness are dissolvers of lipoid. Besides 
acting as anesthetics these substances act as poisons to 
every cell in the body as well. The brain, because of its high 
percentage of lipoid, is more sensitive than other organs to 
the action of chloroform. 
The fact that lipoid is soluble in alcohol, makes alcohol 
rank as a narcotic poison. 
Alcohol Shortens Life. - In 1909 forty-three of the leading 
insurance companies in the United States and Canada 
agreed to make an impartial study of all their records for 
the past twenty-five years. This involved an examination 
of 2,000,000 insured lives. The insured were divided into 
many classes, such as railroading, mining, manufacturing, 
and users of alcoholic liquors. The two following statements 
are made by Arthur Hunter, the chairman of the committee, 
in a study covering a period of three and one half years. 
" Habits as to Alcoholic Beverages. - Nothing has been more conclu- 
sively proved than that a steady, free use of alcoholic beverages, or 
occasional excesses, are detrimental to the individual. In my judg- 
ment, it has also been proved beyond peradventure of doubt that totsl 
abstinence from alcohol is of value to humanity; it is certain that ab- 
stainers live longer than persons who use alcoholic beverages. The 
low mortality among abstainers may not be due solely to abstinence 322 
FOODS, STIMULANTS, AND NARCOTICS 
from alcohol, but to abstinence from tobacco, and to a careful regard 
for one's physical well-being. 
"Among the men who admitted that they had taken alcohol occasion- 
ally to excess in the past, but whose habits were considered satisfactory 
when they were insured, there were 289 deaths, while there would have 
been only 190 deaths had this group been made up of insured lives in 
general. The extra mortality was, therefore, over 50 per cent, which 
was equivalent to a reduction of over four years in the average life of 
these men. If this meant that four years would be cut off the end of the 
average normal lifetime of each man, there are many who would con- 
sider that ' the game was worth the candle '; but it means that in each 
year a number of men will die at an earlier age than they should. For 
example, at age 35, the expectation of life is 32 years : in the first year 
after that age, instead of, say, 9 persons dying, there would probably 
be 12 deaths; that is, three men would each lose 32 years of life; in 
the next year probably four men would each lose 31 years of life, etc. 
As a matter of fact, many immoderate drinkers would live longer than 
32 years, but not nearly so many as would live if they had been moderate 
drinkers, and far fewer than if they had been total abstainers from al- 
cohol." 
Structural Changes Due to Alcohol. - Definite changes are 
found in the protoplasm of nerve cells after the use of alcohol. 
These consist in a shrinking of the nucleus, the loss of the 
spindle-shaped (Nissl) bodies (Figure 247), the swelling of 
the cell, and the presence of vacuoles in the cytoplasm. It 
is also probable that some of the nerve cells are actually 
destroyed. These physical changes explain why the results 
are so great and why complete recovery of mental efficiency 
in the drunkard is so doubtful. The modern point of view 
and the one which is becoming firmly established in the treat- 
ment of drunkards by physicians is that alcoholism is a 
disease. 
Anything which can destroy all the higher and finer emo- 
tions, take away ambition, destroy shame, modesty, pride in 
personal appearance, render one especially liable to common 
diseases, or lead unerringly to insanity is to be avoided. 
231. Tobacco. - " Training starts to-morrow, no more 
smoking," is part of the athletic coach's orders at the begin- TOBACCO 
323 
ning of each season. He knows that the boy who smokes 
cannot reach his highest efficiency or be relied upon at critical 
times in the contest. He would rather have boys who do 
not smoke, because they are stronger, larger, and steadier 
than those who smoke. The cigarette habit has spread until 
it threatens the health of thousands of boys of America to- 
day. How is it known that their health is not good ? The 
charts on " smoker's heart " prove this point. 
Haw the Smoker's Heart Is Affected. - The following illus- 
trations on the rate of the heart beat and the strength of 
the pulse, by W. A. Mc- 
Keever, for thirteen years 
professor of Philosophy in 
Kansas University, show 
w hat really happens when 
we smoke. There is much 
in these illustrations to 
warrant the conclusion 
that the heart of the 
habitual cigarette smoker 
is weak and feeble, except 
for the few minutes during 
which he is indulging the 
habit, and that the pulsations at this time are unduly ex- 
cited. Figure 217 shows three records of a young man nine- 
teen years old who began smoking cigarettes at the age of 
fifteen and who inhaled the fumes. The three records were 
taken without removing or readjusting the instrument, as 
follows: No. I, immediately before smoking, No. II, during 
the indulgence of the habit, and No. Ill, fifteen minutes 
later, after the effect of the narcotic had become apparent. 
Now, by reference to Figure 218, No. Ill, we may observe 
how this young man's heart should record itself, for the 
latter is the tracing of the heart pulsations of a normal young 
man of the same age and temperament. Nos. IV to VI 
Figure 217. 324 
FOODS, STIMULANTS, AND NARCOTICS 
(Figure 217) are representative of another inhaler twenty 
years old, who began the practice at thirteen. He now uses 
a strong pipe. 
In Figure 218, Nos. I and II, taken respectively before 
and after smoking, are 
tracings of a sensitive 
youth of eighteen who 
has been smoking only 
two years. Observe the 
skip of his heart beat at 
x and the corresponding- 
partial skip under the 
stimulus of smoking in 
No. II. No. Ill (Fig- 
ure 218), as mentioned 
above, is a tracing of a 
strong healthy heart of a young man of somewhat excitable 
temperament. No. IV represents the phlegmatic tempera- 
ment; that is, a person who is not excitable. No. V is 
the heart tracing of a strong and healthy young woman. 
In Figure 219, Nos. I 
and II are the pulse 
records of a man of splen- 
did physique, thirty-six 
years old and weighing 
230 pounds. No. I was 
taken before and No. II 
after smoking a cigar. 
He does not inhale. His 
pulse responded readily 
to the stimulus, but as 
the first tracing indicates 
he does not seem to suffer from any heart prostrations between 
indulgences. No. Ill is the record of a person whose vitality 
is temporarily low from nervous fatigue. No. IV is the 
Figure 218. 
Figure 219. TOBACCO 
325 
record of a young woman who was on the verge of nervous 
prostration. No. V is representative of a heart weakened 
by long indulgence in the smoking habit. The young man 
in question began early and continued the practice till his 
physician convinced him of the extreme danger threatening 
his life. The pulse wave is nearly normal in length, but is 
entirely too weak. Under such conditions of heart action 
a man is capable of little courage or aggressiveness. 
Says Mr. McKeever: 
" From the foregoing evidence we are led to the conclusion, that in 
the case of boys and youths, cigarette smoking is very deleterious to 
the physical and mental well-being. Moreover, my investigations in- 
dicate that it makes very little difference in the effects whether the vic- 
tim uses pipe or cigarettes, provided he inhales the fumes; and with 
few exceptions the young smokers are inhalers. The ordinary case 
exhibits about the following type of conduct: (1) While the craving is 
at its height the victim manifests much uneasiness and often much ex- 
citation. (2) During the indulgence the cheek is alternately flushed 
and blanched, the respiration considerably increased, and the hands 
tremble. (3) About twenty minutes after smoking the muscles become 
relaxed, the respiration slow and shallow, the skin on the face dry and 
sallow, and there is an apparent feeling of unconcern about everything." 
Smoking and Scholarship. - Several thousand boys have 
been studied and classified according to age and whether 
they were smokers or non-smokers. In all cases the non- 
smokers had a higher average grade of scholarship. The 
experience of city superintendents and principals is that they 
can usually tell a cigarette boy by his general attitude, poor 
scholarship, and disregard of personal appearance. 
When cigarettes are burned, three distinct poisons are 
produced, which cause serious effects on the boys who use 
tobacco in this form. These poisons are absorbed in small 
quantities by the mucous membrane which lines the nasal 
passages and in larger quantities when the smoke is inhaled 
into the lungs. 
A simple way to prove that cigarette smoke contains a 326 
FOODS, STIMULANTS, AND NARCOTICS 
poison is by blowing the smoke through a glass tube into 
an aquarium containing goldfish. Only a small amount of 
smoke will kill the fish. 
While we all can gradually adapt ourselves to small 
amounts of poison, poisons are never beneficial unless pre- 
scribed by a physician to try to remedy some bodily defect. 
The poisons which arise from the burning of a cigarette 
are never prescribed even as medicines, and have never 
been found in any way beneficial to the human body. 
232. Quacks and Patent Medicines. - The term quack is 
applied to a person who pretends to skill or knowledge which 
he does not possess. Technically, a patent medicine is a 
medicine whose composition is a matter of public record, and 
for which letters-patent have been granted which give 
the patentee the exclusive right to the manufacture and 
sale of this product for seventeen years. Colloquially, 
however, a " patent medicine " is a remedy, usually secret 
in composition, to which a fancy name has been given and 
that name trade-marked. Such a trade-mark gives to the 
owner a perpetual monopoly on the name, while it imposes 
no restrictions on the composition of the product that goes 
under that name. Most so-called patent medicines are of 
the latter type and are really not patented at all. Many 
millions of dollars are spent annually in advertising special 
" cures " and mechanical contrivances guaranteed to cure 
diseases for which they can do nothing, or even to cure such 
diseases as cancer, tuberculosis, epilepsy, etc. 
Nostrums and Cure-alls. - Many people who do not under- 
stand the causes of disease are reluctant to consult a well- 
trained physician, but read and believe the carefully worded 
advertisement of some quack doctor or of some patent medi- 
cine. The untrained sufferer cannot interpret the meaning 
of his distress and is incompetent to select the proper medi- 
cine. As real medicine is given for specific symptoms asso- 
ciated with a specific disease, it is apparent that a patent QUACKS AND PATENT MEDICINES 
327 
medicine advertised to cure from six to forty diseases is 
worthless. Furthermore, real medicine is given to relieve a 
certain set of symptoms at a given stage of the disease, and 
is frequently changed. This is, of course, impossible when 
using a patent medicine. If every one would consult regular 
physicians, and cease patronizing the quacks and patent 
medicines, one of the sources of much sickness and suffering 
would be removed. 
Our government through its enforcement of the Food and 
Drugs Act is doing a great deal to protect those who do not 
understand about disease and its cure. This Act is too 
limited and should be revised and its scope broadened; for 
we find since its passage that there has been an increase in 
the number of remedies sold as " cures " for epilepsy. The 
main drug in these fakes is bromide of potassium, which is 
harmful to the patient, especially in the large doses recom- 
mended. While this drug has the power to suppress tem- 
porarily the epileptic attack, it leaves the sufferer in a worse 
condition. 
Deafness Cures. - The number of " deafness cures " is 
legion. The middle and inner ear, where all diseases of the 
ear are located, is separated from the brain by a thin partition 
of bone and it is extremely dangerous to permit quacks to 
tamper with such a delicate organ as the ear. At the present 
stage of our scientific information, very little can be done to 
cure deafness. By writing to the American Medical Asso- 
ciation, Chicago, Ill., you can secure much information about 
alleged cures for deafness as wTell as about patent medicines 
and mechanical contrivances. 
Obesity Cures. - Woman's fashions during the past few 
years gave a wonderful stimulus to the exploiters of " obesity 
cures." The desire to be slender - often far beyond what is 
compatible with good health - caused thousands of women 
to waste their money on so-called reduction treatments that 
were either dangerous or worthless or both. 328 
FOODS, STIMULANTS, AND NARCOTICS 
Thyroid extract was the basis of many of the "fat re- 
ducers " first put on the market, and this drug is still some- 
what in use. We are all beginning to realize that this is a 
dangerous drug, so that other things have had to be sub- 
stituted. A very common sea-algae, the kelp, has been used 
in many of the fat-reducing preparations. It is difficult to 
find out why this plant is so popular because in some localities 
farmers have used it as food for their hogs in the belief that 
it makes them fat. Overeating and too little exercise are 
the chief causes of obesity. Remove the causes and stop 
buying fakes. 
Pimples. - Between the ages of twelve and eighteen 
usually, nearly all children have pimples, especially on the 
face. There is no remedy that will prevent them. The 
same can be said about the tendency of those of light com- 
plexion to sunburn or freckle, only here there is no age limit. 
Catering to the ignorance and pride of girls especially, fakirs 
advertise numerous cosmetics and lotions for the skin and 
hair. Many of these have been analyzed by the chemists 
of the government and found to consist of borax, starch, 
epsom salts, soap, and other common substances which 
cost from one to three cents a bottle and for which the 
user pays fifty cents a bottle. 
Testimonials. - Testimonial letters stating that the writer 
has been greatly benefited by a given patented preparation 
or mechanical contrivance are abundantly used by all fakirs. 
An official of the United States Post Office once wrote: 
" Speaking generally it may be said that in all my experience 
in this office never has a medical concern, no matter how 
fraudulent its methods or worthless its treatment, been unable 
to produce an almost unlimited number of these so-called 
testimonial letters." An investigation by the American 
Medical Association has shown that some of these letters are 
purchased, some written in the office of the " patent medi- 
cine " concern, and some actually written in good faith. QUACKS AND PATENT MEDICINES 
329 
Those who write the letters in good faith are relatively few in 
number and nearly always ignorant and unable to judge 
accurately of the cause of their trouble. Many of them 
after writing of the benefits are found to be just as deaf or 
epileptic as before. In the case of consumptives who write 
of being helped, it is only necessary to wait a few months 
and the death certificates are available as silent testimonial 
to the fake. 
As the United States Government has been more and more 
successful in prosecuting the ordinary frauds, the propa- 
gators of fakes have become more skillful, especially in the 
false-scientific manner of advertising. 
The following is from 11 The Nostrum and the Public 
Health^ an article published in the Journal of the American 
Medical Association, May 24, 1919, written by Arthur J. 
Cramp, M.D.: 
" The physician, of course, is opposed to the average 
' patent medicine ' because it is exploited in such a way as to 
cause the public to magnify its trivial ailments, to drug 
itself unnecessarily and in cases in which something serious 
is the matter to lose vitally valuable time in seeking medical 
aid. . . . 
" Unfortunately, the home remedies of to-day are, generally 
speaking, ' patent medicines '; and the methods of promoting 
the sale of patent medicines make those products a menace 
to the public health. This not altogether for what the 
remedies themselves contain, although in many instances 
that is distinctly bad, but because of the way such products 
are exploited. ... So to advertise as to make well men 
think they are sick and sick men think they are very sick, 
for the sole and only purpose of causing them to purchase 
drugs to pour down their throats, is more than an economic 
offense; it is a crime against the public health. Yet this is 
the principle on which the average ' patent medicine ' of 
to-day is sold." 330 
FOODS, STIMULANTS, AND NARCOTICS 
Students of even such an elementary course of biology 
as this, possess the needed information to enable them to 
tell the difference between fakes and real remedies. This 
is one of the important results that you should obtain from 
this study. Learn to seek for the real cause of disease by 
consulting the family physician, and pay no attention to 
testimonials for fake cures. 
Alcohol in Patent Medicine. - Many patent medicines 
contain a considerable amount of alcohol. Since the passage 
of the national Food and Drugs Act, which went into effect 
January, 1907, the presence and quantity of alcohol in 
" patent medicines " has to be declared on the label. This 
alone tended to reduce the amount of alcohol in many of 
them but there still remained a large number of preparations 
whose most active and powerful drug was alcohol. Some 
of these were so slightly medicated that the United States 
Government would not permit them to be sold except under 
a liquor license. Since the advent of prohibition, of course, 
these can be sold only under the strict regulations governing 
the prescribing of alcohol. 
Some patent preparations contain also cocain or opium, 
and should not be taken for this reason. 
Alcohol and Disease. - It is unnecessary to make an 
elaborate series of quotations from eminent men to prove 
that alcohol is not useful and necessary as a medicine in 
the cure of disease. There is no evidence that alcohol has 
any effect on the destructive course of a disease, or any bene- 
ficial effect upon the person suffering from disease. This last 
phase of the problem has been under critical study long 
enough to show that the earlier claims of the helpfulness of al- 
cohol in disease are not supported by the facts. The reverse 
is true. Alcohol is known to decrease the power of the body 
to withstand disease and does not assist in destroying the 
poisons which arise in the case of bacterial diseases. It should 
never be used unless definitely prescribed by a physician. OUTLINE 
331 
OUTLINE 
Common nutrients 
Primary foods 
Secondary foods 
Food classification 
Proteins 
Carbohydrates 
Fats 
Mineral matter 
Vitamins 
Economy in purchasing 
Milk 
Universal food 
Of various animals 
Composition of 
Vegetables and fruit 
Variety 
For young children 
For older children 
Meaning of Calorie 
Unit of heat 
Greater Calorie 
Lesser calorie 
Use in measuring diet 
Vitamins 
Different kinds 
A, B, and C. 
Uses 
Aid digestion 
Stimulate cells 
Manufacture chemicals 
Table of vitamins 
Food groups 
Tables 
Proteins 
Fats 
Carbohydrates 
Caloric value 
Substitutes 
Food supply- 
Shortage 
How prevented 
Increase 
Fish production 
Improving 
Animals 
Plants 
War gardens 
Public markets 
Preparation of foods 
Cooking 
Bread 
Substitutes 
Adulteration 
Pure food laws 
Impurities 
In water 
In milk 
Stimulants and narcotics 
Anesthetic 
Ether 
Chloroform 
Poison 
Carbolic acid 
Mercury 
Narcotic 
Alcohol 
Shortens life 
Changes structure 
Tobacco 
Affects heart 
Hurts scholarship 
Quacks and patent medicines 
Nostrums 
Deafness 
Obesity 
Pimples 
Testimonials 
Alcoholic content 332 
FOODS, STIMULANTS, AND NARCOTICS 
SUMMARY 
The energy which enables the human body to move, to grow, and to 
repair tissue comes from the food eaten. These foods fall into three 
classes, proteins, fats, and carbohydrates. Water, vitamins, and min- 
erals are necessary for health. 
All of these foods in the last analysis depend on the activity of green 
plants as they manufacture food out of the raw or unusable compounds, 
water and carbon dioxide. These foods are digested before they can be 
absorbed into the blood. The blood carries the absorbed food to all the 
cells of the body. 
The fact that man cannot live without food has made it imperative 
that he be protected from food adulterations which are harmful to him. 
It is a very rare patented preparation that has a greater food value than 
the regular foods of our diet. 
The use of stimulants is wholly unnecessary for young people, and 
never beneficial, as they do not contain food that is of any importance. 
Cocoa is an exception because it is a food as well as a stimulant. 
Alcohol is a dangerous stimulant, and when taken in large amounts is a 
definite narcotic. 
There is no experimental evidence that tobacco is helpful to growing 
boys and girls. All of the evidence indicates just the reverse. No 
person under twenty years of age should use it. 
QUESTIONS 
Define foods. How many kinds are there? Describe them. How 
do they form in nature? Can man make food out of the raw com- 
pounds? What living things can? What is digestion? Absorption? 
What are stimulants ? What are narcotics ? What is the experimental 
evidence against the use of tobacco by boys? CHAPTER XX 
DIGESTION AND ABSORPTION 
Man is a carnivorous production, 
And must have meals, at least one meal a day; 
He cannot live, like woodcocks, upon suction, 
But, like the shark and tiger, must have prey; 
Although his anatomical construction 
Bears vegetables, in a grumbling way, 
Your laboring people think beyond all question, 
Beef, veal, and mutton better for digestion. 
- Byron 
233. The Digestive Organs. - Man's digestive organs 
consist of the same parts as those already studied in the frog. 
But each region of his digestive organs is more complete and 
the biological principle, the division of labor, reaches its 
highest development in man. The parts of the alimentary 
canal in man are : the mouth, containing the teeth, tongue, 
and glands; the throat or pharynx; the esophagus; the 
stomach ; the small and the large intestine. These several 
parts form a continuous tube, and each does a particular 
work in digestion (Figure 220). 
The Mouth. - The mouth is lined with a soft membrane, 
kept moist by the saliva secreted by three pairs of glands, and 
poured into the mouth in sufficient quantities to moisten 
the dry food and thus assist in swallowing. The tongue is 
a muscular organ and bears on its upper surface many small 
fleshy projections called papillce (pa-pil'le: Latin papilla, 
bud), some of which are fairly large and are arranged on the 
back of the tongue in the form of a V (Figure 221). 
333 334 
DIGESTION AND ABSORPTION 
Our power to taste sweet, sour, bitter, and salt, which are 
the four fundamental tastes in man, is due mainly to certain 
nerve cells located on the larger papillae. The food stimuli 
circumvallate papillae 
fungiform papillae 
Figure 221. - Tongue of Man, 
Showing Two of the Three 
Kinds of Papilla. 
The circumvallate papillae are 
at base of tongue and about five 
or six in number; the fungiform 
papillae are numerous, round, 
mushroom-like projections scat- 
tered over the surface of the 
tongue. The third type of 
papillae, the filiform, are the 
most numerous and like coarse 
hairs. You can recognize these 
papillae on your own tongue. 
Figure 220. - Alimentary 
Canal of Man, with Its Two 
Chief Digestive Glands, the 
Liver and Pancreas, Con- 
nected with the Small In- 
testine. 
The spleen is not a digestive 
gland. The salivary glands con- 
nect with the mouth and are not 
shown. 
received by the special sensory cells of the papillae are carried 
to the brain by the taste nerves. In the brain the food stim- 
ulus is interpreted as sweet, sour, or bitter (Figure 222). 
LABORATORY STUDY 
Blindfold in turn several members of the class and have each hold his 
nose while a small amount of some highly flavored food is placed on the 
tongue. Such common foods as maple sirup, vanilla extract, mar- THE DIGESTIVE ORGANS 
335 
malade, jams, etc., are admirable for this test. Make a record of each 
test. This experiment will prove that we do not taste flavors. Re- 
move the hand from the nose and again taste the same substances. This 
time there will be no difficulty in telling the name of the substance be- 
cause it has been smelled as well as tasted. 
The roof of the mouth is called the palate. The front 
part contains supporting plates of bone and is therefore 
called the hard palate. The back part (the soft palate) is a 
thin sheet of muscle covered 
by the mucous (mu'kus) lining 
of the mouth. The soft palate 
separates the mouth from the 
nasal cavity. Beyond the soft 
palate is the throat cavity, 
called the pharynx. This is a 
funnel-shaped cavity, having 
two openings at its lower end, 
the front one being the open- 
ing into the windpipe which 
leads to the lungs, and the 
rear one, the opening into the 
esophagus. In the upper part 
of the pharynx, on each side, 
is the opening of a Eustachian 
(u-sta'ki-an) tube which passes 
to the middle ear. 
TheEsophagus.- The esoph- 
agus is a nearly straight tube connecting the mouth with 
the stomach. It passes through the diaphragm (Figure 186), 
enlarges, and becomes the stomach. As soon as one swallows, 
control of the food is lost, and further action becomes invol- 
untary. Two sets of muscles, one extending lengthwise, the 
other around the esophagus, act together in forcing the food 
or water into the stomach. This explains why we can drink 
from a brook when the head is much lower than the stomach. 
Figure 222. - Diagram of Taste 
Cells in the Tongue. 
The taste cells are much longer 
than the surrounding cells. The 
nerve which carries taste stimuli to 
the brain ends among these long 
cells. 336 
DIGESTION AND ABSORPTION 
The Stomach. - In man the stomach is the largest section 
of the digestive tube, and it has a capacity of about three 
pints. It is usually described as pear- 
shaped, although there is much variation 
in its form (Figures 223 and 224). At 
the point where the esophagus joins the 
stomach there is a muscular ring (cardiac 
valve, kar'di-ak) which ordinarily prevents 
the food from passing again into the 
esophagus. In vomiting, this valve becomes relaxed. The 
opening at the larger and lower end of the stomach is guarded 
by a similar valve (pyloric, pi-lbr'ik), which serves to retain 
the food in the stomach until certain di- 
gestive changes have taken place. 
The intestine has two parts, a small, 
much coiled tube about an inch in di- 
ameter and about twenty feet long 
called the small intestine, and a large 
section about five feet long and four 
inches in diameter, bent in a rough A 
shape and called the large intestine. At 
the junction between these two regions 
projects a short sac, the vermiform ap- 
pendix (ver'mi-form ap-pen'diks). The 
disease called appendicitis (append-i- 
s/tis) affects this organ. The large in- 
testine ends in a special region called the 
rectum. The opening of the rectum to 
the outside is the anus (a'nus). 
The esophagus, stomach, and intes- 
tine are each lined with a membrane 
that is similar to that found in the mouth cavity. This 
membrane is called the mucous membrane. In the esoph- 
agus, the mucous membrane is smooth and moist, thus 
furnishing an easy passage for the food; in the stomach this 
Figure 223.- Pear- 
shaped Human 
Stomach. 
Figure 224. - X-ray 
Photograph of 
Human Stomach. 
This is a shape 
familiar to physicians 
and is just as normal 
as the shape shown in 
Figure 223. THE DIGESTIVE ORGANS 
337 
membrane is in folds except when the stomach is full of food; 
and in the intestine, it has a velvet appearance due to pro- 
jections called villi (Figure 
225). The numerous 
glands of the stomach and 
intestine are located in the 
mucous membrane. 
Glands. - A gland is 
a group of special cells 
which secrete a fluid. The 
glands which produce the 
digestive fluids are (1) the 
three pairs of salivary 
(sal'i-vS,-ry) glands, lo- 
cated below the ear, and 
beneath the tongue and 
lower jaw; (2) the nu- 
merous gastric (gas'trik) 
glands found in the lining 
of the stomach, possibly 
5,000,000 in number (Fig- 
ure 226); (3) the pan- 
creas ; (4) the liver, the largest gland in the body; and 
(5) numerous intestinal glands in the small intestine. 
-Epithelium 
•Blood vessel 
-Lymph or 
lacteal vessels 
'•Wall 
Intestine 
Figure 225. - Diagram of a Villus from 
the Inner Wall of the Intestine. 
STUDENT REPORT 
Fill out the following table and describe the digestive system of the 
animals studied in Part I. This will help you to understand better the 
parts of the digestive system of man and the work that each part does. 
jjo NoWell- Which 
One Cell ^any Dioestive Digestive defined Ones 
Ceuls rp Tube Digestive Require 
iUBE Glands Food? 
Paramecium 
Frog . . . 
Man . . . 
etc. . . . 338 
DIGESTION AND ABSORPTION 
234. Digestion. - Digestion begins in the mouth. The 
teeth break up the food and mix it with the fluid of the 
mouth, the saliva which contains the enzyme,1 ptyalin. Dur- 
ing this process, sugars and starches are changed into soluble 
sugars. The fluids of the mouth are usually 
slightly alkaline (al'ka-lin or lin, a chemical 
term, thse opposite to sour or acid), but as 
soon as the food passes into the stomach it 
enters an acid (sour) medium, and the di- 
gestive action of the saliva is destroyed in a 
short time by the stomach fluid. For this 
reason, the sugar and starch undergo no 
further digestive changes until they reach 
the intestine. 
Into this acid medium of the stomach, 
the gastric glands (Figure 226) pour out 
the gastric juice (a digestive fluid), and 
the enzyme pepsin in this juice acts on the 
proteins so that they can later pass through 
the walls of the intestine. In the stomach 
the heat of the body dissolves some of the 
fats into oils, but many of the fats used as 
food remain solid at body temperature and 
are unchanged in the stomach. 
After one or two hours the food passes 
into the intestine and undergoes further 
changes in another alkaline medium. Here 
the pancreatic juice, which is made in the 
pancreas, comes into contact with the di- 
gested and partly digested food, causing 
three different changes. One is to complete the change of 
proteins into simpler products; a second is to finish con- 
Figure 226. - Hu- 
man Gastric 
Gland. 
The lining cells 
of the inner wall of 
the stomach pro- 
ject into the tissues 
of the stomach as 
minute pockets. 
The cells shaded 
in this drawing are 
the ones that are 
at the end of the 
pocket and are the 
ones that secrete 
the gastric juice. 
1 The enzymes (en'zim: Greek enzymos, ferment) or ferments, are the 
chemical bodies which digest the food. All plants and animals digest their 
.food by means pf enzymes. THE TEETH 
339 
vertmg starches mto sugar; the third is to assist the bile 
(the digestive juice made in the liver) to digest the fats. 
The digestion of the food is practically completed in these 
three regions of the digestive tube, although digestion con- 
tinues to some extent after the food is passed into the large 
intestine. 
There are three different enzymes in the pancreatic juice 
(trypsin, amylopsin, and steapsin), none in the bile, and one 
in the saliva. 
Inorganic foods, such as water, oxygen, and salts, man 
takes into his body, making them part of his living proto- 
plasm, or using them in oxidation. There is a large amount 
of water in man, enough to make up nearly two thirds the 
total weight of his body. All of his food contains water. 
Oxygen is breathed in from the air, and the various salts, 
such as common salt, sodium chloride (so'di-um klb'rid, or 
rid), calcium (kal'si-iim), magnesium (mag-ne'zhi-um, or 
-shi-), potassium (po-tas'si-um), and phosphorus (fds'for-tis) 
are taken in with our 
food. They are useful 
to the body. A small 
amount of iron is also 
contained in food and 
water and becomes a 
part of the red blood 
cells. 
235. The Teeth. - In 
the mouth cavity just 
back of the lips are the 
teeth. These are especially adapted to the different kinds 
of work each has to do. In adults there are thirty-two, six- 
teen in each jaw, belonging to four classes according to 
shape. In front are the eight incisors (in-si'zers) with sharp 
cutting edges; next the four sharp-pointed canines (ka/nins), 
and back of the canines the eight pre-molars (pre-mo'lers), 
Figure 227. - Permanent Teeth. 340 
DIGESTION AND ABSORPTION 
shaped for tearing and crushing, while the remainder of the 
teeth, twelve in number, are the flat-topped molars which 
do most of the grinding of the 
food. 
Care of the Teeth. - We all know 
' that the teeth are hard. That, 
however, does not prevent them 
from becoming broken by careless- 
ness or accident, or from decaying 
because of neglect. When the 
teeth are not cleaned, a substance 
called tartar forms on them, which 
prevents the bacteria from being 
rubbed off and sometimes pushes 
the gums away from the teeth. 
In 1923 bacteria were isolated 
that cause decay in teeth. These 
bacteria manufacture their own 
acid, which softens the enamel of 
the tooth, causing it to turn dark in color; then these same 
bacteria penetrate deeper into 
the parts of the tooth, where they 
cause a more rapid and extensive 
destruction. The action of bac- 
teria is hastened by the formation 
of acids from the particles of food 
which remain in the mouth after 
eating. The activity of these 
bacteria results in toothache, a 
foul breath, and the imperfect 
chewing of the food. The teeth 
should be brushed after each 
meal to remove particles of food, 
particularly sugar, which fer- 
ments easily. At least once a 
_ 
Ln am ©I 
Den+ine 
Pulp 
Root 
Figure 228. - Vertical Sec- 
tion of Tooth. 
Figure 229. - X-ray of Two 
Teeth. 
Note how firmly the bone fits 
around the roots. These teeth 
are in good condition. The 
white blotches are the places 
where the teeth have been filled. 
This is the new way of examin- 
ing teeth. IMPORTANCE OF MASTICATION 
341 
year there should be a visit to the dentist, who will remove 
those portions of teeth that are decayed and fill cavities, thus 
preventing further decay. 
Poor teeth cannot be made good by brushing, but they 
can be greatly helped by daily care, if aided by the dentist. 
The teeth of children often come in on the outer or inner 
side of the jaw instead of 
on the middle. This 
results in an irregular 
row of teeth. Such teeth 
do not meet the opposite 
teeth as they should (Fig- 
ure 230). Dentists know 
how to straighten such 
teeth, and produce better 
results if they can begin 
their corrective treatment 
before the teeth are fully 
grown. This is very important, not only for one's looks, but 
especially for one's health, as without such treatment proper 
mastication is often impossible. 
Figure 230. - Milk Teeth. 
Age 3| to 4 years. Notice the perma- 
nent teeth deeper in the jaws. 
LABORATORY WORK 
Experiment on Starch Digestion. - Place some starch paste in a 
test tube. Add saliva and mix. Keep warm, and after twenty minutes 
test with Fehling's solution (page 42). The reaction will show that 
the starch has been turned into grape sugar. The starch has been 
digested by the digestive ferment or enzyme in the saliva called ptyalin. 
236. Importance of Mastication. - It is hard to over- 
estimate the importance of chewing the food. Probably 
more bodily ailments come from hasty eating than from any 
other cause. Some years ago Dr. Fletcher started a nation- 
wide campaign for more thorough chewing, and the word 
" fletcherize " was coined to indicate complete mastication. 342 
DIGESTION AND ABSORPTION 
All food should be chewed till it slips from the mouth with- 
out effort. 
Only by chewing can we mix saliva with our food. This 
secretion of the salivary glands keeps the mouth moist and 
aids in digestion and in swallowing. Saliva contains the 
enzyme, ptyalin, which changes starches into soluble sugars. 
For this reason food should be thoroughly chewed, so that it 
may be well mixed with saliva and thus partly digested be- 
fore it reaches the stomach. 
STUDENT REPORT 
Where the Food Is Digested 
T Tkt Primitive Digested 
Digestive Stomach Mouth by 
Cell Leaf Tube Enzymes 
Paramecium 
Hydra . 
Frog . . 
Man, etc. 
Bean . . . 
Yeast.- . . 
LABORATORY STUDY 
Digestion of Proteins and Fats. - Study food and food tests. Artifi- 
cial gastric juice is easily prepared by taking | gram of pepsin, Ay cc. 
of strong hydrochloric (hi-dro-klo'rik) acid and adding 50 cc. of water. 
Take white of egg that has been cooked and subject it, in a test tube, 
to the above mixture. A variety of tests should be made, with and 
without heat (100° F.), with and without the acid. Pancreatic juice 
is made by uniting 15 grams sodium (sb'di-tim) carbonate (kar'bbn-at), 
5 grams pancreatin (piln'krg-a-tln), and 100 cc. water. The action of 
this fluid may be tested as above on the fats, as olive oil; on starch, 
as flour; and on proteins, as raw lean meat or milk. Also examine 
several of the common articles of food to determine to what class of 
foodstuffs they belong. 
237. Absorption of Food. - The absorption of food in 
man and animals is the process of taking the digested foods ABSORPTION OF FOOD 
343 
from the alimentary canal into the blood. Practically no 
food is absorbed in the mouth or esophagus, and but little 
in the stomach. 
The absorption of food from the intestinal canal is done 
by small folds in the lining of the small intestine. To the 
naked eye, these folds appear as a covering of minute hairs, 
called villi (vil'li). Their structure is shown in Figure 225. 
The process of osmosis, which has been so frequently 
referred to in Part I, is the chief factor in the passing of the 
food into the blood vessels. This process is assisted by the 
action of the living cells in a manner not well understood. 
The digested proteins and sugars pass directly into blood 
vessels which lead to the liver. In the liver, these blood 
vessels unite to form the portal vein, which is divided into 
minute branches that distribute the blood to the cells of the 
liver. As the blood thus passes among the liver cells, the 
larger part of the sugar is changed into glycogen (gli'ko-jen), 
an animal starch, and stored temporarily in the liver cells. 
This stored-up starch, glycogen, does not yield energy to the 
body. It is given out gradually from the liver and changed 
back into sugar and is built into protoplasm and thus yields 
energy to the body. This work of the liver results in keep- 
ing a uniform amount of sugar in the blood. 
The fats pass into certain distinct vessels, lacteals (lak'- 
t6-als), which in turn open into larger ones. Eventually 
these vessels unite to form a large duct - the thoracic - 
which empties into one of the veins near the heart. This 
food is now in the blood stream and is carried to the individ- 
ual cells of the body. Each cell takes the kind of food which 
it needs, and by a series of changes, as yet only partly known, 
makes the food into living protoplasm. Circulation is 
given in more detail in the following chapter. 
The indigestible part of the food is not absorbed, but con- 
tinues to move through the small intestine into the large in- 
testine, and on through the rectum. During this progress 344 
DIGESTION AND ABSORPTION 
much moisture is absorbed, especially in the large intestine, 
which leaves the 11 undissolved food " harder and harder. 
The regular removal of the unused part of the food, foeces 
(fe'sez), is of much importance in maintaining health, be- 
cause the bacteria living in the digestive tract cause the 
waste material to decay, and the 
poisonous substances thus formed 
are injurious when absorbed into 
the blood. 
Foods normally remain in the 
stomach from one to five hours, 
and in the small intestine about 
four hours; while they may be 
from six to twenty-four hours in 
passing through the large in- 
testine. 
LABORATORY STUDY 
Demonstration of Necessity for Di- 
gestion of Starch. - To make this 
demonstration it will be necessary to 
have an apparatus to demonstrate 
osmosis. There are several kinds. 
One of the simplest consists of a thistle tube with a piece of parchment 
tied over one end. This can be suspended in a dish of water. Place 
some starch paste in the tube, and after several hours test for starch 
with iodine. If your parchment is tight, no starch will have passed 
through and into the water. This experiment shows that starch cannot 
be absorbed until digested because materials that will not pass through 
such a parchment will not pass through the mucous membrane of the 
intestine. 
238. The Hygiene of Eating. - We become hungry each 
day and feel relieved only after eating. A person frequently 
eats a large meal because of an extra amount of work that is 
to follow. But is he helped to do the extra work? Probably 
not, for the strength to do the work of to-day comes from the 
Figure 231. - X-ray Photo- 
graph of Large Intestine of 
Man Showing Appendix. 
The constrictions are natural. INDIGESTION 
345 
food eaten yesterday, or possibly the day before yesterday. 
The food, even after digestion is completed, must pass 
through many changes before it is built up into protoplasm. 
The actual building of the food into protoplasm is the process 
for which the word nourishment is used, and it should not be 
confused with absorption. 
Students and professional men use their brains more than 
their muscles, but they require protein to repair nerve waste 
just as laborers require proteins to feed their tired muscles. 
Unless students and professional men exercise their muscles, 
they do not feel vigorous and eager for their work. On the 
other hand, unless the laboring men exercise their brains, 
they do not do their work as well as they might. The proper 
amount of exercise varies with the individual. The best 
way to prevent indigestion is to have regular habits of eating 
and exercising. 
239. Indigestion. - Few children who have an opportu- 
nity to romp and play out-of-doors and have plenty of simple 
and plain food ever experience any ill feeling in the digestive 
canal. However, as children grow older, exercise less, and 
eat richer food, they may suffer much inconvenience from 
indigestion. 
Indigestion is a condition which rarely extends to all parts 
of the digestive canal; it is located either in the stomach or 
in the small intestine. This may indicate that certain kinds 
of food are not properly digested. Indigestion may be 
caused by eating the wrong kinds of foods or by overloading 
the stomach. If the food is chewed thoroughly, the appetite 
is usually a safe guide as to the amount needed by the body. 
Moreover, food thoroughly chewed is more easily acted upon 
by the digestive fluids. 
To some people certain foods are indigestible at all times, 
while other foods are indigestible only at special times. We 
should learn to understand our bodies in this particular. 
Some of the causes of indigestion are : lack of sufficient regu- 346 
DIGESTION AND ABSORPTION 
lar exercise, too much rich food, and the failure to drink 
enough water. 
There are in the market many tablets and remedies for 
indigestion, which may, for example, contain pepsin and 
pancreatin. Now we know that these substances when 
found in the pancreatic fluid act in an alkaline medium. As 
these tablets must first pass into the stomach, which is an 
acid medium, the action of the pancreatin is probably de- 
stroyed long before the remedy reaches the intestine, where 
it would naturally act. This means that such tablets are 
largely useless, and it is one of the reasons why many doctors 
believe that digestive tablets are doing more to cause indiges- 
tion than they do to help it. There are only a few commer- 
cial tablets made which act on the undigested foods of the 
intestine. No medicine, in fact, can give permanent relief 
to indigestion. Predigested foods, an attempt to relieve in- 
digestion, serve a useful purpose in cases of sickness, but in 
our regular life should be used sparingly, because they do not 
give the digestive organs the proper amount of work to do. 
240. Effect of Alcohol and Narcotics on Digestion. - 
The lining (mucous membrane) of the stomach and intes- 
tine is delicate and tender, and it contains thousands of cells 
which secrete the gastric juice, and many more thousands 
that help to digest the food. When alcohol comes in con- 
tact with these delicate cells, it prevents them from doing 
their normal work. The result is that food is not properly 
digested. 
Indigestion Disguised by Alcohol but Not Cured. - It is a 
serious error to regard alcohol as a genuine remedy for indi- 
gestion or abdominal pain. It is true the sense of pain is 
sometimes abolished by alcohol and other narcotics, and as 
a result of this many a man believes that such substances aid 
his digestion, whereas they merely exert a numbing effect on 
the stomach nerves, and his indigestion is disguised rather 
than removed. In fact, instead of being cured the mischief EFFECT OF ALCOHOL ON DIGESTION 
347 
is increased, since digestion is retarded. Some digestive med- 
icines contain enough alcohol to be injurious. Alcoholic 
drinks taken with meals make the food hard to digest be- 
cause the alcohol makes the food tough. No narcotic is 
known to be beneficial to digestion. 
Digestive organs 
Mouth 
Esophagus 
Stomach 
Intestines 
Large 
Small 
Glands 
Salivary 
Gastric 
Pancreatic 
Liver 
Intestinal 
Digestion 
Mouth fluids 
Alkaline 
Saliva 
Stomach fluids 
Gastric juice 
Pepsin 
Intestine fluids 
Pancreatic juice 
Bile 
OUTLINE 
Teeth 
Care of 
Brushing 
Bacteria 
Mastication 
Saliva 
Absorption 
Intestinal 
Villi 
Liver 
Portal vein 
Glycogen 
Lacteals 
Thoracic duct 
Hygiene of eating 
Nourishment 
Indigestion 
Cures 
Chewing 
Exercise 
Effect of alcohol on digestion 
Man has a definite set of digestive organs that are more highly devel- 
oped than those of any other animal. These digestive organs prepare 
proteins, carbohydrates, and fats so that they pass into the blood. The 
blood is forced by the heart through definite blood vessels. The study 
of food is important because we require food in order to live. The 
cost of food and the amount needed are problems that science is helping 
to solve. 
SUMMARY 348 
DIGESTION AND ABSORPTION 
QUESTIONS 
What do man and other animals require in order to grow? Name 
the kinds of foods. What is the value of protein? Of carbohydrates? 
What is a Calorie ? What are food substitutes ? Name several ways in 
which the supply of food can be increased. What does cooking do to 
foods? Why is this important? What is digestion? What is indiges- 
tion ? Absorption ? How are the cells of the body fed ? CHAPTER XXI 
CIRCULATION AND ASSIMILATION 
The brain may devise laws for the blood. 
-Shaksperb 
241. Blood. - The blood is the fluid which circulates 
through the heart, arteries, and veins, supplying nutritive 
material to all parts of the body. Blood is made up of a 
fluid (plasma) which contains cells or corpuscles (Latin, 
corpusculum, little body). The blood 
cells or corpuscles are of two kinds, red 
and white. 
The red corpuscles are colored with 
a substance called hemoglobin (he-mb- 
glb'bin: Greek, haima, blood; globus, 
ball). When a few of these corpuscles 
are examined through a microscope, they 
appear yellowish instead of red; but 
when a large number of them are seen in 
a mass, the red color is apparent. When 
the red cells are first formed, they have a 
nucleus which gradually disappears. As a result, the mature 
red corpuscles, unlike all the other cells we have studied thus 
far, have no nucleus. Red corpuscles are about °f an 
inch in diameter and °f an inch thick. 
The red corpuscles carry oxygen from the lungs to the 
cells of the body. As soon as the oxygen in the respired air 
enters the blood, it unites chemically with the haemoglobin 
contained within the red blood corpuscles. Here it remains 
Figure 232. - Photo- 
micrograph of Hu- 
man Blood. 
Compare with Figure 
233. 
349 350 
CIRCULATION AND ASSIMILATION 
until it reaches cells that are deficient in oxygen, when it 
passes from the blood by osmosis to such cells. These cells 
take the oxygen and use it in the process of oxidation, which 
goes on continuously in every living cell. A good supply 
of red blood corpuscles is, therefore, necessary, if the cells of 
the body are to have a sufficient supply of oxygen. The 
feeding of the cells with oxygen is one part of respiration. 
At the same time that oxygen is received from the blood 
by the body cells, carbon dioxide is given off. Again osmosis 
explains the method of this transfer. 
Most of the carbon dioxide is carried 
by the plasma, although some of it 
unites with the haemoglobin. 
The white blood corpuscles are a little 
larger than the red and are much like 
the amoeba in that they are colorless 
and can change their form. They 
move about in the body and often 
leave the blood vessels and collect at 
one place to aid the body in destroying 
disease germs. The white blood cells 
eat these disease germs in just the 
same manner that the amoeba or 
paramecium eats bacteria. 
The blood plasma has its source in the liquids taken into 
the body. It is straw-colored' and varies in composition 
from day to day, and hour to hour. It contains the foods 
on their way to the cells, and waste products on their way 
to the kidneys, lungs, or skin. The volume of blood in the 
average person is about six quarts. 
242. Clotting of Blood. - When the blood is exposed to 
the air it forms a clot. This is a peculiarity of blood. If it 
were not for this property of blood, animals would bleed to 
death from even a slight cut. In some warm-blooded ani- 
mals, the blood clots more quickly than in man. Man is 
Figure 233. - Photomi- 
crograph of Blood of 
Frog. 
The minute black spot 
in each corpuscle is the 
nucleus. The nucleus is 
absent in human red 
blood corpuscles. TEMPERATURE OF THE BLOOD 
351 
able by pressing upon the blood vessels or by tying them to 
assist the process of 
clotting and prevent 
hemorrhage (hem'or- 
raj). Naturally the 
blood does not clot ex- 
cept when exposed to 
the air, when fibrin 
threads are formed 
from the fibrinogen 
(fi-brin'b-jen) of the 
plasma of the blood. 
These threads hold the 
red and white cor- 
puscles. After a short 
time the whole mass 
shrinks, squeezing out 
the fluid part of the 
blood, and the semi- 
fluid mass that remains 
is the clot. 
243. Temperature of 
the Blood. - The nor- 
mal temperature of the 
body of an adult is 
about 98.6 degrees, al- 
though there are a few 
healthy persons who 
regularly have a tem- 
perature either below 
or above this average. 
This is known as blood 
heat, since it is main- 
tained evenly through- 
out the body by the 
Figure 234. - Organs of Circulation. 
Veins, black; arteries, with transverse 
lines. Left side of figure shows superficial 
vessels while right side shows deeper vessels. 352 
CIRCULATION AND ASSIMILATION 
blood. Of course this temperature may be lowered in the 
ears, fingers, toes, and so on by exposure, and it may be 
raised by fever. But normally the temperature (usually 
taken under the tongue with a clinical thermometer) should 
be about 98.6 de- 
grees. When it is 
higher than this, 
the patient is said 
to " have a tem- 
perature," and it is 
a sign that some- 
thing is wrong. 
244. Heart. - 
The blood is car- 
ried from the heart 
to all the cells of 
the body and back 
to the heart again 
and again. This 
organ serves as a 
pump to force the 
blood along. It is 
about the size of 
the fist and has 
strong muscular walls. In a healthy person, it contracts 
about seventy times a minute. It is obvious, therefore, 
that the work which the heart does is very great.1 
Figure 235. - The Human Heart. 
A, aorta; PA, pulmonary artery; PV, pulmo- 
nary vein; RV, right ventricle; LA, left auricle; 
DV, descending vein; AV, ascending vein; LV, 
left ventricle. 
1 "The work the heart does during the day is about equal to the energy 
expended by man in climbing to the top of a mountain 3,600 feet high. 
Assuming that the man weighs about 150 pounds, this would be equal to 
an amount of energy sufficient to lift 90 tons to a height of three feet. The 
work of the left side is greater than that of the right, since the former has 
to drive the blood all over the body, while the latter has only to force it to 
the lungs, which are near by. For this reason the muscle walls of the right 
ventricle are much thinner than those of the left ventricle."-Conn and 
Buddington. HEART 
353 
The heart is located in the thoracic, or chest, cavity, a 
little to the left side and between the lungs. It is a cone- 
shaped organ, inclosed in a membranous bag called peri- 
cardium (per-I-kar'di-um: Greek, peri, around; cardia, 
heart). It has four chambers: two ventricles and two 
auricles (see Figure 235). A strong wall running vertically 
separates the right ventricle from the left ventricle, and a 
partition with valves or gates separates the ventricles from 
the auricles above. The auricles are virtually reservoirs in 
which the blood is stored until the ventricles, which are the 
strong walled divisions of the heart, are ready to propel the 
blood either to the lungs or through the rest of the body. 
Before we follow out the 
circulation of the blood, 
the meaning of three 
words must be clearly de- 
fined. Artery is the name 
given to the blood vessels 
which carry blood from 
the heart. Vein is the 
term applied to the vessels which return blood to the heart. 
There is little structural difference between the veins and 
arteries except that the walls of the arteries are thicker, 
and there are no small valves as in the veins. As the 
branches of the arteries become minute, the walls are much 
thinner, thus allowing the food and oxygen to pass more 
easily to the individual cells. These minute branches are 
called capillaries (Latin, capillus, hair). (See Figure 236.) 
The Pulse. Every time the heart beats the blood is forced 
into the arteries in waves which can be felt in the wrist or 
neck by placing the finger over an artery. The wave is 
called the pulse. By counting the number of waves each 
minute, the rate at which the heart beats is determined. 
When a person runs or takes violent exercise, the pulse rate 
increases. A similar increase in the pulse rate occurs when we 
Figure 236. - Diagram of Capillaries. 
The artery breaks up into minute 
branches, the capillaries, which in turn 
unite to form veins. 354 
CIRCULATION AND ASSIMILATION 
become angry or excited. It is advisable to know what our 
usual pulse rate is, for an increased pulse rate is sometimes 
an indication of approaching illness. 
Closely associated with the pulse is the additional condi- 
tion known as blood pressure. Blood pressure is the force 
with which the blood pushes against the walls of the arteries 
with every heart beat. Special 
appliances have been devised 
which accurately measure the 
amount of this pressure. The 
information thus revealed to the 
skillful physician is often very 
important. 
HOME PROJECT 
Experiments on Pulse Rate. - 
Count the number of beats per minute 
by placing the fingers on the wrist. 
You will need to repeat this count 
several times because you are not ex- 
perienced in such observations. It is 
best to make the count on some one 
other than yourself. After you have 
been able to get about the same num- 
ber of pulse beats per minute in two 
counts, have the person run upstairs 
or hop on one foot fifty times, then 
make your count again. The number 
will be increased as a result of the exer- 
cise. Compare the rate of the pulse when standing, after sitting a 
short time, when lying down, and the first thing in the morning. If 
you were to have your pulse taken just after getting angry or excited, 
you would also find that it has increased over its regular rate. What 
conclusions do you draw from these observations on your pulse ? 
245. Pulmonary Circulation. - The right ventricle, after 
it receives the blood from the right auricle above, contracts 
and forces the blood into a pulmonary artery which has at 
its farther end two branches. One of these goes to the right 
R.V., right ventricle; L.V., 
left ventricle; R.A., right auri- 
cle; L.A., left auricle. The 
arrows indicate the direction that 
the blood takes. Describe its 
course through the heart. 
Figure 237. - Heart. William Harvey (1578-1667) began his studies at a period 
when science was not in good standing. The study of the struc- 
ture of the human body was just being undertaken anew after 
a period of nearly twelve hundred years of neglect. 
He was a very industrious student and his great classic was the 
result of many years of painstaking dissections. A free translation 
of the title of his remarkable book gives us the following: "An 
Anatomical Disquisition on the Movement of the Heart and Blood in 
Animals." 
Harvey was the first one to describe the blood as moving in a 
circuit in the body and to state that the beating of the heart supplies 
the propelling force. After his brilliant dissections, man learned 
for the first time the difference between a vein and an artery and 
learned how to stop bleeding. He also made notable contributions 
to knowledge about the development of animals and their activities. 
True ideas about secretions, respiration, and the distribution of 
food in the body began as soon as the exact course of the blood 
was known. This is the reason why Harvey's discoveries are of 
such historical importance. SYSTEMIC CIRCULATION 
355 
lung and the other to the left lung. These two branches 
subdivide in the tissues of the lungs until the blood is forced 
into minute capillaries which everywhere occupy the lungs. 
It is in these small capillaries in close contact with air spaces 
that the blood receives its new supply of oxygen and gives 
off its carbon dioxide. Finally these capillaries flow into 
veins which unite eventually 
and return to the left auricle. 
The blood is now ready to 
enter the left ventricle and be 
pumped through the system. 
To.head 
To Arm 
Auricle-- 
To Arm 
^•-Ventricle 
-To Brain 
•To Skin 
»-To Artn 
''-To Lung 
>AII to Back 
as-To Stomach 
*-To small intes- 
tine 
"To Kidney 
/To Reproductive 
" organs 
ssTo Large 
Intestine 
.--To Stomach 
•To Small 
Intestine 
To Kidneys? 
To Back 
/To Large Intestine 
To Legs 
.-'To Leg 
Figure 238. - Main Arteries 
of Man. 
Compare with Figure 239. 
Figure 239. - Main Arteries 
of Frog. 
This is the pulmonary circulation, and by it the blood is 
purified, i.e., it has lost much of the carbon dioxide and se- 
cured a fresh supply of oxygen. Its color has changed from 
a bluish red to a bright red. 
246. Systemic Circulation. - From the left ventricle 
the blood is forced by its contraction through the aorta, 356 
CIRCULATION AND ASSIMILATION 
the largest artery in the body, the aorta divides at its 
base into two small arteries which carry the blood through 
the heart tissue and supply this with food and oxygen. Far- 
ther up the aorta branches into other arteries, some leading 
to the arms, some to the head, some to the trunk of the body, 
and others to the legs, so that all of the body is supplied with 
blood from the subdivisions of the arteries. The small 
arteries subdivide into capillaries, which penetrate to all 
the cells of the body and supply them with oxygen and foods 
in solution. These capillaries are so very numerous that in 
a piece of muscle with a 
cross section the size of 
an ordinary pin, there 
are about eight hundred 
of these microscopic 
blood vessels. A recent 
investigator states that 
the blood vessels of an 
average-sized man, if 
placed in a continuous 
straight line, would reach 
around the globe two and 
one half times. Because 
of their great numbers 
and consequent large sur- 
face, the capillaries can carry nourishment and oxygen to 
the tissues, and readily remove the waste. The capillaries 
conduct the blood from the arteries toward the smaller 
veins, which then become larger after the manner of the river 
system which is filled up by numerous tributaries. Eventu- 
ally these veins carrying the blood toward the heart reach 
the right auricle through two main veins. This is the sys- 
temic circulation, and during the movement of the blood 
it has given up much of its supply of oxygen and lost much 
of its food value, which has been taken from it by the cells. 
Figure 240. - Diagram of Artery, 
Capillary and Vein. 
As the blood flows through the capillaries 
of a voluntary muscle, for example, oxygen 
and other food products are given off to 
the muscle cells, and carbon dioxide and 
other wastes pass off from these same 
muscle cells into the capillaries on the 
way into the veins. LYMPH 
357 
Portal Circulation. - The portal circulation includes the 
portion of the systemic circulation which courses through 
the liver and digestive regions and then returns to the heart. 
In the liver the blood takes up foods in 
solution. 
Thus it will be seen that the composition 
of the blood changes as it passes through the 
various organs of the body, such as the 
skin, muscles, and stomach. The capillaries 
supply the substance necessary for the secre- 
tions of the glands; in the small intestine 
they absorb the elements of digested food; 
in the lungs they take up oxygen and give 
off carbon dioxide ; and in the kidneys they 
throw off the waste products they have 
collected. 
The process by which each part of the 
body takes from the blood the food ele- 
ment that it needs is called assimilation. 
247. Lymph.-As the blood flows through 
the capillaries, part of the plasma passes through the thin 
walls into the spaces between the cells and bathes the cells. 
This fluid which escapes from the capillaries is called lymph 
Figure 241. - Dia- 
gram of a Vein 
Showing the 
Valves. 
In which direc- 
tion does the blood 
flow in this dia- 
gram ? 
Lymphafic gland 
Figure 242. - Superficial Lymphatics of Arm and Hand. 
(limf). It is composed of digested food, water, and other 
substances. The cells assimilate the food which they need 
and cast back into the lymph the wastes which they have 358 
CIRCULATION AND ASSIMILATION 
formed in the process of growth and repair. These spaces 
between the cells are small and irregular in shape. The 
spaces, however, form a sort of mesh, or net, the parts of 
which join, forming larger vessels, and finally all the lymph 
is collected into two large vessels which open into veins. 
Thus there is the lymphatic circulation, which differs from 
that of the blood in several ways. (1) There is no special 
organ for forcing the lymph along, the circulation depend- 
ing mainly upon the movement of the muscles. (2) The 
lymphatic vessels are imperfect in the beginning, being only 
irregular spaces. (3) The lymph contains no red corpuscles 
and only a few white corpuscles. 
248. Cuts. - Since every part of the body inside the skin 
is traversed by blood vessels, we cannot injure any part 
without breaking some blood vessels. A small cut causes 
the blood to flow only from capillaries, and it flows slowly 
and in small quantities. If a vein be cut, the blood will be 
dark in color, and will flow in larger quantities, but steadily. 
A severed artery sends out bright red blood in waves corre- 
sponding to the beat of the heart. To stop the flow of blood 
from a vein, compress the vein beyond the cut; from an 
artery compress the artery between the cut and the heart. 
In either case remain quiet to aid the blood to form a clot. 
249. Exercise. - The object of a circulatory system and 
of a circulatory fluid is to supply every cell in the body with 
food and to carry away the waste. The more active the pro- 
cess of circulation, the more perfectly is this object accom- 
plished. It is the common experience that the heart beats 
more rapidly, the lungs work harder, and the body becomes 
warm after a few minutes of vigorous exercise. These 
changes have a decidedly beneficial effect upon building up 
the body and removing the wastes. 
Fainting. - Fainting is due to an insufficient supply of 
blood in the brain. This lack of blood may arise from 
several causes, but the most common is some disturbance DUCTLESS GLANDS 
359 
of the digestive processes, which causes the heart to beat 
too slowly. A fainting person should be placed flat on his 
back, if possible, with his head slightly lower than the rest 
of his body, and should be given plenty of fresh air. A dash 
of cold water in the face, or a bottle of ammonia held to the 
nostrils, is often helpful in restoring consciousness. 
250. The Effect of Drugs and Alcohol. - Some drugs 
cause the blood to flow more rapidly, others more slowly. 
Coffee makes the heart beat faster and also makes some 
of the arteries smaller. That is why it is called a stimulant. 
While alcohol may increase the activity of the heart, the 
effect of taking large amounts is to weaken the heart action. 
If taken only in small amounts, the heart sometimes shows 
a slight increase in its rate of beating, but this occurs only 
when the brain becomes excited, and if the person is kept 
quiet no change in the heart beat is noticeable. Thus the 
primary action is on the brain. 
Another effect of alcohol is to enlarge the small blood 
vessels in the skin. This produces a flushed skin, and a 
feeling of warmth, and gives a false sensation of increased 
circulation. It sends more blood through the skin with 
consequent extra loss of heat. This action is due not so 
much to stimulation, as to the relaxation of the muscles. 
Thus there is a decrease of activity rather than an increase, 
even though the blood does flow a little more rapidly through 
the skin. For these reasons alcohol cannot be properly 
called a stimulant to the circulation. 
When alcohol is introduced into the blood, the forming 
of the clot takes place more slowly, though alcohol taken 
in the usual beverages will not entirely prevent the clotting 
of blood. 
251. Ductless Glands. - There are a number of glands 
in the body that discharge their secretions directly into the 
blood and not into the intestinal cavity as the pancreas and 
liver do. Such glands are commonly described as the duct- 360 
CIRCULATION AND ASSIMILATION 
less glands, or the glands of internal secretion. The best 
known of these are thyroid, adrenal, thymus, and pineal. 
There is a considerable number of these glands and all play 
an important part in the normal growth and activity of our 
bodies. We are just beginning to understand, in part at 
least, their importance, but a great deal more must be dis- 
covered before we can accurately describe the influence of 
these glands. Sometimes they manufacture more secre- 
tions than they normally should, and sometimes they fail 
to set free the usual amount. Excessive growth such as 
we find in giants and excessive fatness are attributed to an 
oversupply of certain of these internal secretions; while 
dwarfishness and some forms of imperfect growth in children 
are believed to be due to an inadequate amount of these 
secretions. 
The thyroid gland is found in the neck just below the voice 
box. It consists of two parts, that are united by a thin 
strip passing across the front of the air tube. The nor- 
mal thyroid is small and inconspicuous. When it becomes 
greatly enlarged the swelling is known as goiter. 
The adrenal glands are two small bodies which are situated 
just in front of the kidneys. It has long been known that 
they are necessary to life. If they are destroyed, as some- 
times happens in one of the many forms of tuberculosis, seri- 
ous consequences follow, and the skin takes on a dark color. 
That, with other symptoms, gives rise to what is known as 
Addison's bronze disease. 
252. Hormones. - The glands of internal secretion pro- 
duce substances which have been described as chemical 
messengers or hormones (hor'mo-nez). Such bodies are 
produced in some definite gland but have to be carried to 
other parts of the body before they can produce any effect. 
These chemical messengers are very important in stimu- 
lating the flow of gastric juice and the secretions of the pan- 
creas, as well as aiding in the activity of the thyroid gland. OUTLINE 
361 
A great deal of emphasis is placed to-day upon the impor- 
tance of the chemical messengers of the body in regulating 
its normal activities. 
OUTLINE 
Blood 
Corpuscles 
Red 
White 
Clotting 
Fibrinogen 
Temperature 
Heart 
Location 
Chest 
Parts 
Auricles 
Right 
Left 
Ventricles 
Right 
Left 
Pulse 
Blood pressure 
Circulation 
Pulmonary 
Right auricle 
Right ventricle 
Lungs 
Capillaries 
Left auricle 
Left ventricle 
Systemic 
Left ventricle 
Aorta 
Arteries 
Capillaries 
Veins 
Right auricle 
Portal 
Liver 
Digestive organs 
Lymph 
Circulation 
Cuts 
Treatment 
Arteries 
Veins 
Exercise 
Effects 
Fainting 
Reason for 
Treatment 
Effects of alcohol 
Weakens heart 
Enlarges blood vessels 
Relaxes muscles 
Ductless glands 
Thyroid 
Goiter 
Adrenal 
Bronze disease 
Hormones 
SUMMARY 
The blood of man consists of corpuscles and plasma. The haemo- 
globin in the red corpuscles unites with the oxygen in the lungs and car- 
ries the oxygen to all parts of the body as the blood flows through the 
numerous arteries and capillaries. The waste gas, carbon dioxide, is 
also carried by the blood from the cells to the lungs, where it is released 
to the air. 362 
CIRCULATION AND ASSIMILATION 
The heart of man is highly developed and consists of four chambers, 
those in the same side connected by valves. The work that the heart 
does in pumping the blood is very great. It is easy to modify the pulse 
rate by lessening or increasing your natural activities. The ductless 
glands pour out their secretions into the blood. These secretions are 
known as hormones or internal secretions. We are just beginning to 
realize that they play a very important role in our normal activities. 
QUESTIONS 
What is blood? What are its parts? Which of its parts are dead? 
Which are alive? Explain the work of the blood. What is the relation 
of the lungs to this work ? Why is it important to know about the way 
blood flows in arteries and veins? What are ductless glands? What 
do some of them do for us? CHAPTER XXII 
EXCRETION 
The kidneys are the filters of the blood. 
- Bacon 
253. Excretion. - Every animal uses energy in carrying 
on its work. During this process a certain amount of waste 
substance is produced, which has to be removed from the 
body. The kidneys, lungs, intestines and skin are the chief 
organs which assist the body in getting rid of this waste. 
When any part of the living cells is broken down in the simple 
act of living, a waste product results. By osmosis these 
waste products enter the blood and are removed by the 
lungs, which give off carbon dioxide, by the sweat glands 
in the skin, and by the kidneys, which remove the wastes 
that contain nitrogen. 
The sweat glands and kidneys are usually regarded as the 
excretory organs of man. These organs remove from the 
blood the wastes which have been excreted by the cells of 
the body. The excretion from the living cells is one of 
the fundamental life processes of all plants and animals. 
254. Kidneys. - The kidneys are two bean-shaped or- 
gans located in the abdominal cavity, one on each side of 
the " small " of the back. Each is about four inches long, 
two and a half inches wide, and half an inch thick. The 
color is a dark red. The kidney is made up of two layers, 
the outside or cortical, and the inside or medullary. Each 
layer is composed of many small tubes (tubules) which open 
into an area called the pelvis, the space within the kidney. 
363 364 
EXCRETION 
The pelvis continues into a duct (ureter'), and from each 
kidney the ureter passes into the bladder. A small duct 
(urethra) (u-re'thra) connects the bladder with the exterior 
of the body. 
Each tubule in the kidney is in close relation with the 
blood capillaries. At the place where this close relation is 
found, glomerulus (glb-mer'u-lus), the walls of the capillary 
and the walls of the kidney 
are very thin. Through 
these thin walls a large 
amount of water filters out 
of the blood into the tubes. 
At the same time waste 
material which contains 
nitrogen, salts, and other 
organic wastes is removed. 
If these wastes are not re- 
moved, they create toxins 
which poison the body. 
255. Lungs. - The car- 
bon dioxide that passes 
from the blood by osmosis 
into the lungs is a waste 
product. Associated with 
this waste there is found 
a rather large amount of 
water, sometimes as much as a pint in twenty-four hours. 
The importance of the lungs in giving off water vapor which 
is a waste product is regarded by some physiologists as 
greater even than that of the skin. 
256. Intestine. - The excretion wastes from the intestine 
are not easily defined. The several digestive secretions which 
are not absorbed may be regarded as waste products after 
they have caused the different digestive changes. Of these 
a small portion remains in the intestine. The bile pigments 
Figure 243. - Longitudinal Section 
of Kidney. SKIN 
365 
may be especially mentioned as excretions that pass from 
the body through the intestine. The real excretions of 
the body should not be con- 
fused with the indigestible 
part of the food which is 
not taken up by the blood 
and which passes out 
through the large intestine 
as faeces. 
257. Skin. - The skin 
covers and protects the vol- 
untary muscles, regulates the 
body temperature, gives off 
waste matter, and acts as a 
general sense organ. Thus 
we see that it is incorrect to think of the skin simply as an 
organ of excretion. In order to understand just how wastes 
are removed by the skin, 
it is necessary to study its 
parts. The outer layer 
of the skin is called the 
epidermis (Figure 245) 
and is chiefly composed 
of dead cells. These 
outer cells are constantly 
breaking off, a process 
which is most apparent 
in the case of sunburn. 
Whatever pigment or 
coloring matter there is 
in the skin is located in 
the inner cells of the epi- 
dermis. The amount and 
kinds of pigment determine whether a person is of light or 
dark complexion, white, black, or yellow. These inner cells 
Showing relation of artery and 
vein to portion of minute kidney 
tube (uriniferous tubule). 
Figure 244. - Diagram. 
Figure 245. - Diagram of Skin. 366 
EXCRETION 
are constantly growing new cells to replace the cells which 
scale off. 
The nails and the hair arise in the outer layer of the 
skin. 
Other structures which arise in the same way are the scales 
of fishes and snakes, the hoofs and horns of cattle, and the 
feathers of birds. 
The inner layer of the skin is the dermis; it contains blood 
vessels, nerves, connective tissue, the sweat glands, and sense 
organs of touch, pain, heat, and cold. It is estimated that 
there are over two million sweat glands in the skin of man. 
These are the excretory organs of the skin, and their work 
is to eliminate waste substances from the blood and to keep 
the body temperature normal (98.6° F.) by regulating the 
amount of perspiration excreted. The amount of perspira- 
tion is influenced both by the temperature of the body and 
of the air. The evaporation of perspiration keeps the body 
at the normal temperature. 
The skin is attached to the body by a loose layer of con- 
nective tissue in which fat is deposited. This is known as 
the subcutaneous layer of fat. This layer becomes very 
thick in corpulent people. 
258. Importance of Bathing. - "A clean skin is a healthy 
skin," and we may add that a clean skin is the only skin that 
can properly carry on all of its activities. Bathing and 
exercise serve to keep the skin clean and healthy. 
No exercise is really complete unless it is followed by a 
bath, for during exercise the pores of the skin have been 
opened and it has been active and perspiring. The best 
time to take a bath is in the morning on rising or as soon 
as exercises have been taken. A cold bath which does not 
last more than five or six minutes is best. Hot baths are 
weakening and depressing. Regular habits of bathing, as 
also of eating, sleeping, and exercising, are indispensable 
hygienic measures and help to keep us well. IMPORTANCE OF EXCRETION 
367 
259. Adaptations in Excretory Organs. - You have only 
to review what has been said about the structure of the kid- 
neys, sweat glands in the skin, and the minute air sacs in 
the lungs to recall that in each of these organs the cells are 
especially adapted to carry on the work it does. The thin 
layers of cells in the lungs permit the gas, carbon dioxide, to 
pass through readily. The cells in the sweat glands are 
adapted to removing water from the blood, while the kidney 
cells act largely as filtering cells. This adaptation in the 
kidney cells is more evident, if we recall that the cells of the 
liver manufacture urea, which consists of a large amount 
of the nitrogenous wastes of the body. The urea is dis- 
charged from the liver into the blood and removed from the 
blood by the kidneys. 
260. Importance of Excretion. - Unless the several or- 
gans of excretion do their work properly the wastes of the 
body accumulate. These wastes are poisonous, and harm- 
ful results must follow if they are allowed to remain in the 
system. A skin which is not healthy cannot be expected to 
hold healthy nerve endings nor to do its work as it should. 
Overeating or eating too much meat places an extra burden 
on the kidneys because the body absorbs only as much 
nutriment as is needed and can be stored as fat. The rest 
has to be removed. This makes the work of the kidneys 
especially hard. Regularity and moderation in eating, as in 
all habits, are two excellent rules to follow. The removal of 
wastes from the body is influenced by the amount of water 
taken daily. There are few who drink enough water and 
very few who ever drink too much. 
SUMMARY 
Excretion is one of the fundamental life processes in all living things. 
In the higher animals special organs are present which remove these 
wastes. These are the kidneys, lungs, intestines, and skin. Unless the 
body is kept clean and healthy, the excretory organs do not do their 
work well. Each organ is adapted to removing the different kinds of 368 
EXCRETION 
wastes. The best hygienic rule to follow is to eat with moderation, to 
eat and sleep regularly, to take sufficient exercise, to keep the body clean, 
and to drink plenty of water. 
QUESTIONS 
What is the meaning of excretion? Is this process present in the 
frog? In the crayfish? What are the special organs of excretion in 
the frog? In man? How are they adapted to doing their work? 
How may they be hindered from doing their best work ? CHAPTER XXIII 
THE NERVOUS SYSTEM OF MAN 
Back of the sound broods the silence, 
Back of the gift stands the giving ; 
Back of the hand that receives, 
Thrill the sensitive nerves of receiving. 
- Realf 
261. The Parts of Man's Nervous System. - The nerv- 
ous system of man consists of the same general parts as the 
nervous system of the frog (see page 148). There is a brain 
and spinal cord, from which nerves extend to the special 
senses, the muscles, the heart, and the stomach. When the 
brain of man is compared with that of the frog, it is obvious 
that the cerebrum of man is proportionately larger. Al- 
though some of the other parts of the brain appear unlike 
the corresponding regions in the frog, scientists tell us that 
they are really the same. 
262. Nerve Cells or Neurons. - The nervous system of 
man consists of many thousands of nerve cells or neurons 
which differ from all other cells in having more parts and 
branches (Figures 247, 248, 249). Examination shows that 
the nerve cells have a prominent nucleus surrounded by 
cytoplasm, which grows out into a number of branches called 
fibers. The shorter branches divide and form, together with 
the branches from the neighboring nerve cells, a mass of 
tangled fibers. There is usually one unbranched fiber, 
perhaps several feet long, which ends either in the skin, in 
some muscle, or in the spinal cord or brain. When this 
long fiber reaches the muscle or skin, it divides into several 
369 370 
THE NERVOUS SYSTEM OF MAN 
fine branches. All these branches belong to the cell, so in this 
connection the word neurons includes all the branches, the 
nucleus, and the cyto- 
plasm. It is the unit 
of the nervous system. 
263. The Location 
of the Nerves. - The 
nerve fibers which have 
the same work to do 
occupy certain definite 
places in the brain and 
spinal cord. A student 
of the nerves can tell 
the route which the 
stimulus arising from 
feeling a pencil must 
travel before reaching 
that part of the brain 
where it is interpreted 
as a pencil-; or the route 
over which the stimulus 
arising from tasting 
candy must pass before 
it is known to be that 
of candy. When we 
see the pencil or the 
candy, the route over 
which the sight stimuli 
of these two objects 
travel is not the same 
as that of the feeling of 
the pencil or tasting the 
candy. The nerve cells 
which interpret the stimulus arising from feeling the pencil 
or from tasting the candy or seeing the pencil and the candy 
Figure 246. - Nervous System of Man. THE LOCATION OF THE NERVES 
371 
are probably not the same. We may say, therefore, that 
the spinal cord and brain are made up of many special nerve 
pathways which end in nerve cells that interpret stimuli. 
The nerves which connect the central nervous system, 
that is, brain and spinal cord, with all parts of the body, 
consist of many long nerve fibers. Each 
nerve looks like a small white thread and 
is covered with a thick, fatty sheath 
(medullary sheath). In the living animal, 
this fatty sheath is white and the nerve 
fibers so covered are found to occupy a 
certain part of the spinal cord and brain. 
Thus, we get the name white substance. 
Other of the nerve fibers and cell bodies 
are not covered with a sheath and so have 
a gray appearance. Thus we have the 
term gray substance in connection with 
the nervous system. 
The Central Nervous System. - In Fig- 
ure 246 the nerves of the legs, arms, and 
trunk are all seen to be united to a cen- 
tral body, the spinal cord. There are 
nerves in the upper part of the neck and 
in the head region that unite with the 
large mass at the upper end of the spinal 
cord, the brain. The brain and spinal 
cord are known as the central nervous 
system. The brain is divided into the 
following parts: cerebrum, the most an- 
terior ; the mid-brain, to which the optic 
nerves join; the cerebellum; and the medulla oblongata, to 
which the nerves of hearing, tasting, and the facial nerves 
belong. 
The cerebrum is the most important of the several regions 
of the brain. It regulates and controls all our nervous activ- 
Figure 247. - Nerve 
Cells. 
Stained to bring 
out the minute parts 
in addition to the 
nucleus. 372 
THE NERVOUS SYSTEM OF MAN 
ities. The cerebellum gives tone and vigor to the contrac- 
tion of the muscles and helps us to know when we are prop- 
erly balanced and is hence known as the equilibration center. 
The remaining parts of the brain give off and receive nerves 
and transmit nerve stimuli to the cerebrum and cerebellum. 
Thus each part of the nervous system has a definite func- 
tion, and is adjusted to its environment by means of the 
different senses. These 
we shall study more in de- 
tail later in this chapter. 
The Sympathetic Ner- 
vous System. - This is 
made up of a double 
chain of ganglia (Greek 
ganglion, a knot), which 
are connected with each 
other by nerves and with 
the central or cerebro 
spinal system by fibers. From these ganglia many fibers run 
to the blood vessels of the heart and to the organs of the 
alimentary canal. When people die of shock, this is caused 
by the serious disturbance of the sympathetic system. 
264. Growth of the Nervous System. - The nervous 
system of man, like all other parts of the body, has a definite 
beginning and grows in an ordered manner. Not only is 
this true in man, but also in the frog and fish. The tissue 
of the embryo, which is to grow into brain and spinal cord, 
gradually changes until the adult parts are formed. Dur- 
ing this early period of growth, the nerve cells send out 
processes which become nerve fibers, so that at birth the 
nervous system is ready to go to work. Indeed, nearly all 
the nerve cells which the human being is ever to use are made 
before birth. These cells gradually become more active 
and the different parts of the brain work more perfectly as 
we go through the periods of childhood, youth, and maturity. 
Figure 248. - Nerve Cells 
Stained by the silver process which 
blackens all the parts. This is an excel- 
lent stain to show the branching processes. REFLEX ACTION 
373 
The brain becomes a more perfect working organ by making 
the brain cells do their specific work over and over and over, 
until each group of cells can be relied upon to do a definite 
thing. 
While the nervous system grows naturally, its training is 
also important, for it may be said to be the organ of the 
mind. Habits may be formed as in the case of the rest of 
the body, by the selection and control of certain impulses 
and sensations. 
265. Reflex Action. - Reflex action is the simplest form 
of nervous activity in man. For example, when the finger 
Figure 249. - Diagram to Show Reflex Action. 
The stimulus comes in contact with the skin and is carried to the spinal 
cord. It then passes to the motor cells which carry the order to the muscle. 
The same skin stimulus goes to several other parts of the spinal cord. 
is placed on a hot stove and suddenly withdrawn the follow- 
ing actions take place. The heat stimulus affects the nerve 
endings in the finger and that stimulus is carried to the spinal 
cord. If this were all that occurred, the finger would burn, 
because this stimulus and the nerve fibers over which it 
travels have no control over the muscles. The removal of 
the finger is brought about by another set of nerve cells - 
the cells which have their fibers ending in the muscles of the 
hand and arm. 
All these changes take place involuntarily, and the re- 
action to the stimulus is known as reflex action. Specific 374 
THE NERVOUS SYSTEM OF MAN 
names are used in describing these several changes; the 
nerve fibers which connect the skin with the spinal cord 
and brain are called afferent (af'fer-ent: Latin, ad, to; fero, 
carry) fibers because the stimulus always travels towards 
the brain. 
Their function is sensory, for they carry the stimulus to 
the brain. The fibers which connect the muscle with the brain 
or spinal cord are the efferent (ef'fcr-ent: Latin, ex, from; 
fero, carry) or motor fibers, because they carry their mes- 
sage away from the central nervous system. Their function 
is to produce motion. In the special instance we are study- 
ing, the heat stimulus causes the spinal cord to send a special 
message to the muscles of the finger, so that the latter is 
removed from the stove. 
This is a typical illustration of the simplest way in which 
the nervous system works, but in most reflex actions there 
are other results. After the finger has been removed from 
the hot stove by reflex action, we soon realize that the skin 
is burned, the realization coming through the smarting sensa- 
tion. This second stimulus has been carried to the brain, and 
we are now conscious of the stove, heat, burn, etc. If there 
were no afferent nerve fibers, the individual could not ex- 
perience any pain when hurt. 
The afferent and efferent nerves, whether in reflex or in 
general nervous action, never vary in the work which they 
do. The sensory afferent nerves form the only paths over 
which our information of the outside world travels to the 
brain. The stimuli which cause the different sensations, 
such as taste, sight, etc., have their individual paths and re- 
ceiving organs. This is indicated by the fact that no other 
nerves than those of the ear are ever affected when we hear. 
Reflex Action in the Frog. - The frog, like man, is able to 
act in a definite way. If any one approaches a frog while it 
is sitting on the edge of a pond, it jumps into the water, 
stirs up the mud, and then returns to the shallow water near REST AND RELAXATION 
375 
the place where it entered. The frog, in this case, acts as if 
it, or its ancestors, had learned that this is the best way to 
escape enemies. While this series of acts is called a habit, 
it is really a series of reflex acts which are similar to the reflex 
action described for man, and require the same nerve struc- 
tures. 
Reflex action is similar in all animals. The stimulus must 
be received by an afferent nerve, or some structure which 
can do the same work, and it must be transformed into a 
series of purposeful movements. 
266. Rest and Relaxation. - We frequently read of some 
famous man who is able to do his work with but a few hours 
of sleep. But for the great majority of us, cutting short 
the hours of sleep soon renders us unfit to do our work. 
Sleep is nature's method of resting the body. The muscles 
even in their correct use have been under a long strain. The 
natural waste products caused by the varied activities have 
accumulated faster than they have been removed and the 
entire body is fatigued. Some people have urged that a 
change of activity is a rest, but this is only true in a very 
limited sense. 
We spend about one third of our lives regularly in sleep, 
and this is the most complete form of rest. During the 
period of sleep the nervous system and muscles are in a re- 
duced form of activity. We usually sleep more soundly 
during the early hours of the night. 
It is customary to describe the accumulated wastes of our 
bodily activity as fatigue toxins. This means that these 
waste products, unless removed, act as poisons to the body. 
Whenever fatigue is severe and clearly defined we have to 
do with a loss of power. The usual fatigue is relieved by a 
single night's rest, but when it is not, the conditions soon 
become more serious and require medical advice. 
Anticipation is a word that suggests either joy or fear to 
most of us. Under the usual conditions we look forward to 376 
THE NERVOUS SYSTEM OF MAN 
the pleasures of the day in school and, if happy, the work 
passes off with little difficulty. On the other hand, an un- 
happy state of mind produces just the opposite result, and 
the day's work is poorly done, with a marked increase in the 
amount of fatigue. The natural anxiety and fear that arises 
in the case of sickness in one's family may be so great as to 
disturb an otherwise good digestive system or prevent the 
proper concentration on study. .It is unfortunate to yield 
to anticipated fear and anxiety, and we should cultivate the 
habit of thinking about the pleasures and the duties of each 
day. 
Amount of Sleep. - Different amounts of sleep are required 
in the periods of youth, of maturity, and of old age. Youth 
requires more sleep than maturity because two requirements 
must be met: first, the restoration of the tissues that have 
been broken down during the day; second, the growth of 
new tissue as the body is increasing in size during youth. 
The mature person has only the first requirement to meet. 
In old age tissues are repaired more slowly and, therefore, 
more rest is necessary. 
It is unwise to try to establish an exact law in regard to the 
requirements of sleep, for some individuals need more daily 
sleep than others. The statement is generally made that 
eight hours of sleep is sufficient for anybody. There are 
some who need more and some who are better off with less. 
A simple rule is to ask the question: How do you feel when 
you get up ? Does the world look bright and full of promise ? 
Are you anxious to be " up and doing " ? If so, then you have 
had enough sleep. 
267. Brain Efficiency. - While the efficiency of the brain 
depends upon mental training, in order properly to exercise 
the many functions of this organ at least three things are 
necessary: good food, sufficient sleep, and abstinence from 
alcohol and tobacco. We have already discussed the ques- 
tions of food (page 298). BRAIN EFFICIENCY 
377 
At a baseball game, you have noticed a boy catch a " fly " 
when it looked like a " home run," or how enthusiastic 
the crowd became when the pitcher struck out the last man 
with the bases full. The nervous system of each player 
was efficient in a critical test. 
We all ride on street cars or railroads, but do you know 
that most of the men who run the street cars and trains have 
to pass an examination to determine whether they can be 
Efficiency Centers 
Word Centers 
Balancing Centers 
Breathing Center 
Heart Center 
Nerve to Heart 
Figure 250. - Brain Control. 
trusted to do their work properly and well; i.e., whether 
their nervous systems will stand the test ? 
The question of brain efficiency is illustrated by Figure 250. 
Long before birth the heart in the embryo begins to beat 
and is under the control of the nervous system. The part 
of the brain which superintends the heart is located in the 
medulla, where a special cluster of cells sends out nerve 
fibers which enter the heart nerve. These nerve cells are 
called the heart center. 378 
THE NERVOUS SYSTEM OF MAN 
The next nerve center to begin work is the breathing 
center, located close to the heart center, which controls the 
breathing. This does not become active until after birth. 
About a year after birth, several more nerve centers be- 
come active in the child's brain. These are the ones which 
help him to walk. The cerebellum contains nerve centers 
which play an important part in walking and in learning to 
balance. The muscles which move the arms and legs are 
regulated by nerve centers in the cerebrum. 
Soon after the child learns to walk, he begins to talk and 
learn words. The several nerve centers which now become 
active are all located in the cerebrum. These are the nerve 
cells which are necessary in speaking, hearing, reading, and 
writing words. 
After the age of fifteen years the brain goes through impor- 
tant structural changes and the young person begins to do 
hard tasks well. It is difficult to locate the exact spots in 
the cerebrum where the nerve centers are that now become 
active, for they are widely distributed. These nerve centers 
may be called the efficiency centers and they are the last to 
develop. But as they become active, every one becomes 
skillful in respect to some one thing, although many years 
of training are necessary before the maximum of efficiency 
is reached. 
The efficiency centers which are the last to become active 
and which require so much energy to train properly are the 
first to be affected by alcohol. 
268. Structural Changes Due to Alcohol. - Definite 
changes are found in the protoplasm of nerve cells after the 
use of alcohol. These consist in a shrinking of the nucleus, 
the loss of the spindle-shaped (Nissl) bodies (Figure 247), 
the swelling of the cell, and the presence of vacuoles in the 
cytoplasm. It is also probable that some of the nerve cells 
are actually destroyed. These physical changes explain 
why the results are so great and why complete recovery of STRUCTURAL CHANGES DUE TO ALCOHOL 
379 
mental efficiency in the drunkard is so doubtful. The mod- 
ern point of view and the one which is becoming firmly es- 
tablished in the treatment of drunkards by physicians is 
that alcoholism is a disease. 
In order to judge the success of a piece of work we must 
consider the quality and speed with which it is done. Krae- 
pelin made the following experiment, the results of which 
show that both these ele- 
ments in mental work are 
influenced by the use of 
alcohol. 
Several men who were 
allowed to drink no alcohol 
utilized half an hour daily 
for six days in adding fig- 
ures. Their ability to add 
increased each day. On the 
seventh day the work was 
begun under the influence 
of alcohol. In spite of the 
skill gained in the previous 
practice, their accuracy did 
not increase, but on the 
contrary began to decrease 
rapidly. On the nineteenth 
day the use of alcohol was 
stopped, and immediately 
an improvement in the work manifested itself; but on the 
twenty-sixth day, when the use of alcohol was resumed, a 
decided decrease in the power of adding manifested itself. 
It is difficult to estimate how efficient each of us may 
become in our life work, but one thing is certain, that if we 
use alcohol, we shall lose that perfect control over our nerv- 
ous systems which enabled the two players in the preceding 
section to be so efficient in the ball game. It is also equally 
SKILL ANO ENDURANCE IMPAIRED 
BY DRINK 
Tests in Target-Shooting in Swedish Army 
I. SKILLED TESTS 
Thirty shots fired in quick succession 
Non-Drinking Days: Average 24 hits out 
of 80 shots 
Drinking Days: Average 8 hits out of 
80 shots 
Alcohol taken equal to amount in 1% to 2 
pints of 5 per cent beer, 20 to 80 minutes 
before shooting, and an equal amount the 
night before 
II. ENDURANCE TESTS 
Non-Drinking Days: 860 shots fired be- 
fore exhaustion 
Drinking Days : 278 shots fired before ex- 
haustion 
Alcohol taken 30 minutes before test was 
amount contained in about iy4 pints of 
4 per cent beer 
Figure 251.- Effects of Alcohol. 380 
THE NERVOUS SYSTEM OF MAN 
certain that if we use alcohol, we shall find fewer men willing 
to employ us in places of responsibility, not only because 
of our lowered efficiency, but because of our unreliable 
judgment. 
269. Sense Organs. - All the higher animals have eyes, 
ears, a nose, and a tongue. Each of these organs contains 
nerves specialized to respond to a certain definite kind of 
stimulus. The result of this specialization is that not only 
are these special sense organs complex in structure, but also 
the region of the brain which receives their messages. The 
ear nerve responds to a stimulus of air-waves of a certain 
length, and we say we hear a sound. The eye nerve is stimu- 
lated only by light. Each nerve and the brain cells to which 
it sends its messages have become so specialized that prac- 
tically only one kind of reaction takes place. For example, 
all stimuli acting upon the eye nerves are interpreted as 
light. 
The skin is a simpler sense organ than the eye or ear, 
and tells us of pain and touch and the difference between 
heat and cold. 
Smell and Taste. - These two senses are closely related. 
The sense of smell is located in the nose, and the organs of 
smell are minute nerve cells scattered among the regular 
cells that line the nasal passageway. The olfactory nerve 
which carries smell stimuli to the brain is the shortest nerve 
in man. 
Taste has already been described in connection with the 
digestive system on page 334. 
270. The Eyes. - The eyes of all vertebrates have the 
parts arranged in a similar manner. The eyeball is roundish 
and is located in the eye sockets of the skull, which are 
termed orbits. There is an upper and a lower eyelid, and 
the remains of a third eyelid in the corner next to the nose. 
The front of the eye is covered by a transparent membrane, 
the cornea (kor'ne-a); and the rest of the eye is surrounded THE EYES 
381 
by a tough membrane, the sclerotic coat, or the white of the 
eye. Within the combined covering of the cornea and sclera 
are a number of structures which take part in receiving and 
transmitting the rays of light to the brain. 
A cross section of the eye shows two more membranes 
in close relation to the sclerotic coat (Figure 252). The 
membrane in direct contact on the inside with the sclerotic 
layer is the choroid (kb'roid). The choroid coat is filled with 
blood vessels and pigment. Through this layer the food 
in the blood is distrib- 
uted to the eye. The 
third layer or coat is 
the retina, which is com- 
posed of nerve cells and 
is nearly transparent. 
The cornea and these 
three layers inclose two 
chambers which are 
separated by the lens 
(Figure 252). In front 
of the- lens a curtain- 
like membrane, the ins, 
partly covers the lens, 
except for a round open- 
ing in the center which is called the pupil. The color of the 
eye, gray, black, blue, or brown, is due to the presence of 
pigment in the iris. The small front chamber is filled with a 
transparent fluid which is composed principally of water and 
is known as the aqueous (a'kwe-us) humor. The large back 
chamber is filled with a thin, transparent, jelly-like fluid, 
the vitreous (vit're-us) humor. 
In order that we may see any object, a pencil in our 
hand, for example, two general conditions must be present. 
The picture (image) of the pencil must be placed on the 
retina, and this picture must be carried to the brain by 
C, cornea; C', choroid layer; I, iris; 
I.C, inner chamber; O.C, outer chamber; 
L, lens; O.N, optic nerve; R, retina; 
5, sclerotic coat. 
Figure 252. - Section of Eye. 382 
THE NERVOUS SYSTEM OF MAN 
the eye (optic) nerve. When these two conditions take 
place, we see. 
As we have learned, the stimulus for the eye is always 
light. In physics we learn that the rays of light travel in 
straight lines. This fact explains why we cannot see around 
a corner. When the rays of light are made to pass through 
a glass lens, the rays which pass through the thin edges of 
the lens are bent and do not travel to the same place they 
would have reached had they not passed through the lens. 
In the same way light rays from an object pass through the 
lens in our eyes and are bent. This results in the image of 
the object, the pen- 
cil in this instance, 
being inverted on 
the retina. The 
light rays from the 
pencil stimulate the 
nerve cells in the retina, and this stimulus, after being carried 
to the brain, is interpreted to us as a pencil, though we do 
not know how stimuli travel on nerves. 
The inverted image of the picture on the retina is due to 
the shape of the lens. When the stimulus reaches the living 
cells of the retina and through them is passed on to the optic 
nerve and the brain, a series of changes takes place in these 
living cells. There is no evidence as to how an inverted 
or upright picture passes through these living cells in the 
retina and brain. We do know that we have to learn the 
meaning of all stimuli. For example, a baby reaches for 
things far beyond the length of its arms and it is only after 
many trials that it eventually acquires precision in reaching 
for an object. It is probable that each one of us passed 
through a similar stage of learning to interpret the stimuli 
that arose from light. In coming to understand light stimuli, 
the sense of touch was of great assistance. Try to explain 
how this would be so. 
Figure 253.- How We See the Pencil. THE EYES 
383 
Care of Eyes. - The eye is our most important source of 
information ; through it we learn to recognize each other and 
understand the appearance of our work. Just as soon as 
we realize that we do not see as readily as our companions, 
we should have our eyes examined, to be sure that there are 
no defects of vision. People with defective vision usually 
fall into three classes: first, those who can see objects near 
at hand, but do not recognize objects at a distance; such 
persons are near-sighted. Second, there are those who 
recognize distant objects but do not see clearly objects close 
at hand ; such persons are far-sighted. These defects are due 
to the shape of the eye and can be corrected only by the use 
of glasses, which should be worn after a careful examination 
by a qualified physician. The third class consists of those 
to whom objects appear hazy. They are said to have 
astigmatism, w7hich can be readily corrected by the proper 
glasses. This common defect is found when we compare 
the two eyes. We see better with one eye than the other. 
This is another defect that can be corrected only by the use 
of glasses. There are people who do not distinguish readily 
the different colors. They are color-blind. This defect 
cannot be corrected by the use of glasses. 
In reading, the light should be sufficient and steady and 
should come over the shoulder. The eyes, like the rest of 
the body, get tired and need to be rested. They give 
us our best service when the entire body is in a healthy 
condition. 
Cigarettes and Eyes. - When cigarettes are burned several 
poisons are produced. Nicotine, carbon monoxide, hydro- 
cyanic acid, puridine, sulphureted hydrogen, picolin, and 
lulidin are some of the toxins that have already been isolated 
from tobacco. These poisons are absorbed in small quanti- 
ties by the mucous membrane which lines the nasal passages 
and in large quantities when the smoke is inhaled in the 
lungs. Many persons, even adults, are made ill whenever 384 
THE NERVOUS SYSTEM OF MAN 
they absorb these poisons, and any competent physician 
can detect the detrimental effect of smoking on young people. 
Some very recent investigations 1 on the influence of smok- 
ing on the eye prove conclusively that the poisonous effects 
are more marked and serious than the earlier studies revealed. 
Inflammation of the optic nerve, which seems to act on certain 
nerve fibers only, is thus produced. This causes a defect in 
the central field of vision first for green, then for red, and 
finally for blue and white. There is also an alteration in the 
size of the " blind spot " in some smokers. When these 
symptoms appear they can be relieved only by completely 
ceasing to use tobacco. If the person who is subject to 
tobacco toxemia does not abstain, then permanent blindness 
may follow. Since this habit of smoking has been taken up 
by girls and women who do not seem to have the resistance 
to these poisons that most men have, these toxic signs develop 
frequently within a few months after the use of tobacco. 
271. The Ear. - The ear is a sense organ for the recep- 
tion of the stimuli which we interpret as sounds. The ear 
of man consists of the outer, middle, and inner ear. The 
first two carry the stimuli to the third, where they are re- 
ceived by nerve cells and carried to the brain. 
The diagram of the ear (Figure 254) shows the several 
parts and their relations. The outer ear leads to the tym- 
panic (tim-pan'ik) cavity; the middle ear is in communica- 
tion with the mouth, and the complex inner ear is partly 
shown. There is a group of small bones in the middle ear 
which conduct the sound vibrations to the delicate inner 
ear. The internal ear receives the various sound waves, 
and transmits them to the brain, where they are explained 
as sounds.2 
1 We are indebted to Dr. David F. Gillette, Syracuse, N.Y., for these 
recent facts concerning the influence of smoking on vision. 
2 When certain parts of the ear (semicircular canals) are injured, one has 
difficulty in standing or in walking erectly. This is because the inner ear 
serves both as a hearing and a balancing organ. THE EAR 
385 
Hearing. - Sound waves strike the ear drum (tympanic 
membrane), which in turn causes the small bones in the 
middle ear to vibrate. The bones cause the water in the 
internal ear to move, thus stimulating the nerves of hearing. 
The pressure of air on each side of the ear drum is nor- 
mally the same. This is due to the entrance into the mid- 
dle ear of air from the mouth, through the eustachian tube. 
Figure 254. - Plan of Ear. 
0-E, outer ear; M.E, middle ear; l.E, inner ear ; Eu, eustachian tube. 
This tube is a trifle more than an inch long. When it 
becomes closed, partial deafness results. 
Defects in hearing may be caused by blows upon the 
ears, by the accumulation of wax in the ears, and by sore 
throat. When there is a continued ringing or hissing sound 
in the ears, consult a doctor at once. 
Care of the Ears. - Next to our eyes the ears are our best 
sense organs, and we should know how to take care of them. 
There are so many harmful things that can be done and done 
so easily that one authority has said that the best treatment 386 
THE NERVOUS SYSTEM OF MAN 
to give the ear is " absent treatment." He means to let the 
ear alone except to keep it clean. To do this, the proper 
use of a wash cloth is all that is necessary. The wax in the 
ear normally moves outward and the cloth on the end of the 
finger will keep the ear sufficiently clean. 
It is important to heed the old saying, " Never pick your 
ear with anything smaller than your elbow." Digging the 
ear with toothpicks, hairpins, and other hard and pointed 
instruments is often the cause of irritation that is followed 
by inflammation. If your ears are not acting right, go to an 
ear specialist. 
Most of our ear trouble comes from infection in the middle 
ear, which is connected with the mouth by the eustachian 
tube. When one has a cold and blows his nose very hard, 
especially pinching the nose, the result is often to force some 
of the germ-laden mucus up the eustachian tube. Here 
the germs grow rapidly, causing a congestion and inflamma- 
tion. The different conditions that arise from such infections 
of the middle ear are the chief causes of deafness. 
The ear drum receives the gentle sound waves and trans- 
mits them through the bones of the middle ear to the internal 
ear. If the ear drum is injured, as it can be even by striking 
the ear with one's hand, it does not vibrate properly. 
Special attention should be paid to getting proper rest and 
relaxation, and the eyes and ears should have particular 
care. In looking after these and the other sense organs, we 
should avoid the use of alcohol and tobacco, as these both 
have an injurious effect on the nervous system. 
OUTLINE 
Nervous system 
Nerve cells (neurons) 
Cytoplasm 
Nucleus 
Fibers 
Location of nerves 
Central system 
Brain 
Spinal cord 
Sympathetic system 
Ganglia SUMMARY 
387 
Growth of nervous system 
Cells 
Fibers 
Reflex action 
Afferent 
Sensory 
Efferent 
Motor 
Rest and relaxation 
Fatigue toxins 
Amount of sleep 
Brain efficiency 
Effect of alcohol 
Shrinking nucleus 
Hurting Nissl bodies 
Swelling cell 
Sense organs 
Smell and taste 
Seeing 
Eye 
Cornea 
Sclera 
Choroid 
Lens 
Iris 
Pupil 
Aqueous humor 
Optic nerve 
Care of eye 
Nearsighted 
Farsighted 
Astigmatic 
Color-blind 
Harm done by cigarettes 
Hearing 
Ear 
Outer 
Ear drum 
Middle 
Eustachian tube 
Inner 
Care of ears 
Cleanliness 
Congestion 
SUMMARY 
The nervous system of all vertebrates consists of a brain and spinal 
cord with nerves passing to all organs of the body. The brain of man 
is the most highly developed. 
All our movements are controlled by means of the nervous system. 
Through our sense organs we gain our information of the world. 
The nervous system is made up of cells which are highly specialized. 
Their main work is to transmit and interpret stimuli. The nerves of 
man are so highly specialized that all stimuli which affect the eye are 
thought by us to be light stimuli; or all stimuli which enter the ear, 
seem to be sounds. The stimulus which passes over any of our special 
sense organs travels over several different nerve cells before it reaches 
the place in the brain where it is interpreted. The highly specialized 
nervous system and sense organs grow and are fed just as muscles or 
skin grow and are fed. There is no special food which we can eat that 
is used exclusively by the nervous system. When the brain is af- 
fected by alcohol, it is the highly developed centers that suffer most. 388 
THE NERVOUS SYSTEM OF MAN 
QUESTIONS 
What is the nervous system ? Of what parts is it composed ? What 
animals have you studied that have a nervous system? Which ones 
lack a special nervous system ? How does the nervous system grow ? 
Describe the nerve cell. How does it differ from other cells in man? 
What are special senses? What kind of information do you receive 
through your eyes? What kind through your ears? Which do you 
remember ? (The well-trained mind remembers equally well the infor- 
mation that comes in through each of its sense organs.) 
REFERENCES 
Cutten, The Psychology of Alcoholism. 
Davenport, Heredity in Relation to Eugenics. 
Guyer, Being Well-Born. 
Horsley and Sturge, Alcoholism and the Human Body. CHAPTER XXIV 
BACTERIA: THE SMALLEST PLANTS 
Why has not man a microscopic eye ? 
For this plain reason: man is not a fly. 
Say, what the use, were finer optics given, 
T'inspect a mite, not comprehend a heaven. 
- Pope 
272. Bacteria. - Bacteria are the smallest of all plants 
- so small that they can be seen singly only through the aid 
of a powerful microscope. We do not know all about their 
life processes, but we have learned much about their effect. 
We constantly hear about these plants, either under their 
correct name, bacteria, or under the names of germs or mi- 
crobes. Two incorrect ideas concerning bacteria are preva- 
lent, - one, that bacteria are animals, and the other, that 
all are harmful. It is definitely known that bacteria are 
plants; that small as they are, they are among the most 
important plants in the world ; that most of them are helpful, 
and only a few harmful. They are, however, so much like 
the one-celled animals (protozoa) that the word germ is not 
unnaturally used to cover both. 
273. Shape and Size of Bacteria. - Bacteria, according to 
their shape, are grouped into three classes: (1) round (the 
cocci); (2) rod-shaped, like a short unsharpened pencil 
(the bacilli); (3) those that are shaped like a corkscrew 
(the spirilla). Most of the names for the different bacteria 
contain one or another of these words, thus indicating the 
389 390 
BACTERIA: THE SMALLEST PLANTS 
shape of the bacterium1 under discussion. The spirilla 
and the bacilli often have on one or both ends tiny thread- 
like hairs called flagella by which they move, giving the first 
observers reason to think that they were animals. 
To show how small bacteria are, fifteen hundred of the 
rod-shaped form will hardly reach across the head of a pin. 
When bacteria are grown in the proper kind of substance, 
there are so many in a cluster that they appear as tiny spots 
or points, often tinged with a faint 
color. When seen alone under the 
microscope, they are clear, almost 
transparent, and colorless, and often 
have a bright, shining spot on the 
inside. 
274. Where Bacteria Are Found. 
- Bacteria are everywhere, - in 
the air, as invisible dust; in the 
upper layers of the soil; and in 
water. We breathe in the microbes 
of the air with every breath, but 
generally with no injurious result. 
Every bacterium has its own work 
to do, and a healthy body gives little opportunity for most 
kinds of bacteria to do harm. 
275. Conditions Necessary for the Growth of Bacteria. - 
Like all other plants, bacteria must have all the proper con- 
ditions before they can grow and multiply. Their food is 
chiefly plant or animal matter, but they cannot make use of 
food except in the presence of warmth and moisture, and 
most of them require oxygen in addition. They get the 
oxygen from the surrounding air. 
276. Life Processes. - In the preparation of their food 
bacteria break up organic substances, that is, decompose 
them, causing the condition known as decay. They use 
Figure 255. 
A, cocci; B, bacilli; C, 
spirilla; D, bacillus with 
flagella. 
1 Bacterium, singular of bacteria. LIFE PROCESSES 
391 
some of the material resulting from decay; some they set 
free in the air; and the remainder is left on the earth to be 
used by more complex plants. In changing dead matter - 
plants, leaves, and animals - to a form which again becomes 
a part of the earth, bacteria perform a service valuable to 
man. 
Reproduction occurs in bacteria through simple fission. 
Sometimes bacteria break entirely apart, while in other 
cases they remain connected, forming a chain. Under 
favorable conditions each cell can grow to full size in half an 
hour and be ready to divide again. It is this ability to 
multiply rapidly which makes them of so great importance, 
for a few hundred bacteria, even of the harmful ones, could 
produce little effect. 
In the process of growth, bacteria produce two substances, 
enzyme (see page 28) and toxin (tbx'in: Greek, toxicon, 
poison). Enzymes produce fermentation, a breaking-up 
process of which man makes use to secure certain flavors 
and odors, as well as to soften hard materials. Toxins are 
usually poisonous to living organisms, including the bac- 
teria which produce them. 
Enzymes cause the pleasant flavor of such articles of food 
as cheese and butter. The quality of tobacco depends largely 
upon the kind of bacteria which have been at work upon it. 
Such bacteria are classed as helpful, as are those which 
gather nitrogen for the plants of the bean family. Other 
helpful bacteria are those which make it possible for man 
to use sponges by ridding them of the soft, slimy substance 
with which they are filled when alive, as well as the bacteria 
which soften the useless parts of the flax plant so that the 
rest of it may be separated and made into linen. 
When food, air, warmth, or moisture is not sufficient, 
bacteria cease to grow and go into a resting state. That 
is, they change their form, and surround themselves with 
a substance which protects the soft protoplasm from being 392 
BACTERIA: THE SMALLEST PLANTS 
harmed by freezing, heating, or drying. The simple plants 
all do this, but the simpler the plant, the more easily does it 
resist. It is this ability to withstand unfavorable conditions 
and to resume growth when conditions change for the better 
that makes bacteria " such good friends and such bad foes." 
Our ability to control them is due largely to a knowledge 
of their habits. 
LABORATORY STUDY OF BACTERIA 
Prepare culture plates of agar-agar from the following formula: 
Agar-agar Formula for 1000 c.c. 
Agar-agar1 15 grams 
Beef extract 3 grams 
Peptone 10 grams 
Salt 5 grams 
Water 1000 grams 
Boil material for the agar-agar formula; add sodium hydrate till the 
color of litmus paper is not changed; cool to about 56° C., and beat 
into this one whole egg, including the shell. Warm slowly to the boiling 
point and continue till the egg is firmly coagulated; then strain the clear 
medium through a cheesecloth on to moist cotton in a filter funnel. 
Work rapidly. Cool, and then boil once more. Filter through cotton 
into test tubes. Each tube should not be more than a quarter full. 
Plug the tubes with cotton. Then sterilize this mixture in the test tubes 
by placing them upright in water and boiling twenty minutes on each of 
three successive days. Let part of the test tubes cool, in a slanting 
position, having the plugged end elevated half an inch. These are called 
slant agar tubes. When petri2 cultures are needed, melt up a sterile 
agar tube and pour into a sterile petri dish. 
1. To show that bacteria are present on one's hands: draw the 
fingers of the unwashed hand across the surface of the agar-agar in petri 
dish; cover and set away for four days at room temperature or two 
days at body temperature. 
2. To show that fewer bacteria are present on freshly washed hands: 
draw the fingers of the washed hand across the surface of the agar-agar; 
cover and set away. 
3. To show that bacteria lodge under the nails, place on culture 
plates scrapings from under finger nails, (1) before washing the hands, 
(2) after washing the hands. 
1 Secured at most drug stores. 3 Flat, round dish with cover. SOIL BACTERIA 
393 
4. To show that heating milk reduces the number of active bacteria, 
sprinkle drops of milk and water mixture on agar-agar petri dish, 
(1) natural milk, (2) pasteurized, (3) boiled. (Use one tenth milk 
and nine tenths sterilized water.) 
5. To show that bacteria change the medium in which they grow, 
note, besides the number, form, size, and color of the colonies, whether 
any change takes place in the agar-agar. 
6. To show that bacteria grow best in the presence of warmth and 
moisture, compare those grown under such conditions with those grown 
in a dry or a cold place. Note the influence (a) of warmth, (6) of cold, 
on the rapidity of growth. 
7. To show that bacteria are in the air, expose the surface of the 
culture plate for a few seconds. 
8. To show that flies distribute bacteria, let a fly walk across the 
surface of the agar-agar in the petri dish. 
9. Expose a growing culture to strong heat; to strong sunlight. 
10. Immerse a growing culture in 10% formalin, in 85% alcohol, or 
any other good germicides. 
The term germicide usually refers to chemical germicides, 
of which the most common are corrosive sublimate, carbolic 
acid, chloride of lime, sulphur, and formalin. These are also 
antiseptics and disinfectants, and all of them are poisonous. 
But germicide may also refer to the methods of destroy- 
ing bacteria. A high temperature of 140 degrees if main- 
tained for half of an hour kills the active bacteria, but those 
that are in the spore stage are killed only after prolonged 
heating. Moist heat is more effective than dry. Sunlight 
is one of the best germicides known. Bacteria cannot with- 
stand the effect of direct sunlight for more than a few hours. 
The practical use of sunlight is limited because it requires 
that objects be fully exposed. 
There are different forms of bacteria, such as soil bacteria, 
dairy bacteria, and the various bacteria whose growth is 
counteracted when food is preserved by canning, salting, 
and so on. These will now be taken up in order. 
277. Soil Bacteria. - The surface soil, especially if it is 
rich in organic matter, contains many kinds of bacteria. 394 
BACTERIA: THE SMALLEST PLANTS 
The bacteria decrease in number as you go deeper below the 
surface. At a depth of ten feet they are usually scarce. 
Ordinary earth may yield from 10,000 to 100,000,000 per 
gram if it has become polluted. Soils which have not been 
cultivated have fewer. The condition which really deter- 
mines how many bacteria will be found in the soil is the 
amount of organic matter. 
The soil bacteria do a most important work in breaking 
down the parts of dead plants and animals and in enriching 
the soil so that living plants can find more nourishment in it. 
The roots of such plants as the clover and the pea (legumi- 
nous plants) become infested with certain bacteria found in 
the soil. These bacteria form bunches or nodules on the 
roots in which they live. Thus protected, they gather nitro- 
gen from the air, use what they need, and store up the rest. 
This surplus is used by leguminous plants in making protein, 
part of which is found in the body of the plant, and part in 
the seeds. When the seeds are used as food, man and the 
animals secure the protein which they need. When the 
plants die, they leave the soil richer in nitrogen in a form that 
can be used by plants which do not have the help of the 
bacteria to gather it. So valuable is this form of fertilizer, 
that in some cases leguminous crops are raised and plowed 
under for the sake of the nitrogen in them, this being called 
" green manuring," a practice which was carried on for a 
long time before the reason for its value was learned. 
The relation which exists between the plants which profit 
by the work of the nitrogen-gathering bacteria and at the 
same time furnish them protection is an illustration of sym- 
biosis (sym-bl-6'sis: Greek, syn, together; bios, life), the 
relation of mutual helpfulness between organisms of different 
kinds. 
Inoculation. - Nitrogen-gathering bacteria are likely to 
be present in all soils in small numbers, but in order to have 
them help plants to an appreciable degree, there must be BACTERIA IN RELATION TO MILK 
395 
many of them. It has been found possible to place them in 
the soil artificially, a process called inoculation. This is 
done either by wetting the seeds with water containing the 
bacteria, or by putting them into the soil in some other 
manner. Care should be taken to secure only pure cultures 
and to have them fresh. By the use of cultures a soil properly 
inoculated will not only produce larger crops of leguminous 
plants, but its quality is 
also improved for crops 
which follow them, as ex- 
plained above. 
278. Bacteria in Rela- 
tion to Milk. - Milk as it 
comes from the healthy 
cow is practically free from 
bacteria of any kind. The 
number of bacteria pres- 
ent, however, is not of so 
much importance as the 
kind. But if a large num- 
ber of bacteria are allowed 
to get into the milk, some 
of them are sure to be 
harmful and may find con- 
ditions so favorable for 
their growth as to make trouble for the person using the 
milk. 
A high grade of milk will not contain more than 500 to 
1000 bacteria per cubic centimeter. Such milk has been 
well cared for and comes from healthy cows. Some cities 
permit milk to be sold that contains as many as 100,000 
bacteria per cubic centimeter and some even more. Such 
milk comes from unhealthy cows or dirty barns, or has been 
kept too long, or has " changed hands " too many times. 
To deliver pure milk to the consumer costs the producer 
Photograph by R. S. Breed. 
Figure 256. - Culture Dish with 
Bacteria (a). 
This culture was made from milk six 
hours old that had been kept in a re- 
frigerator in a clean milk bottle. 396 
BACTERIA: THE SMALLEST PLANTS 
time, care, and money, and consumers should be willing to 
pay more for milk which has had proper care. 
Keeping Milk Sweet. Ice prevents harmful bacteria from 
multiplying sufficiently to make milk dangerous, unless the 
milk is kept too long a time. Preservatives, soda, borax, 
boric acid, formaldehyde, and the like, are sometimes used 
to prevent the growth of bacteria. In some cases no im- 
mediate harm seems to 
come to the persons using 
milk thus preserved, but 
some of these substances 
are poisonous, and pure 
milk, properly cared for, 
does not need them. The 
use of any milk in which 
preservatives are found 
should be avoided. 
P asteurization. - A 
harmless bacterium gets 
into milk kept too long 
and forms lactic acid, thus 
giving the milk a sour 
taste and causing it to 
curdle. Sour milk is per- 
fectly wholesome for food, 
but the taste is disagree- 
able. In 1857 Pasteur dis- 
covered this bacterium. He also found that milk could 
be kept for several days without becoming sour, after it had 
been heated sufficiently to kill this bacterium. 
This process, called after its discoverer pasteurization, con- 
sists in heating milk for twenty minutes at a temperature of 
60° C., or to a higher degree for a shorter time, and then 
cooling it rapidly. This procedure kills nearly all the bac- 
teria in the milk and does not change the taste or make it 
Photograph by R. S. Breed. 
Figure 257.- Culture Dish with 
Bacteria (b). 
This culture contains the same amount 
of milk as that shown in Figure 256. 
It was taken from the same bottle six 
hours later after it had stood in a warm 
place. Louis Pasteur (1822-1895). This distinguished Frenchman was 
trained as a chemist and made a notable contribution to this field 
of knowledge before he began to study germs. Soon after the 
invention of the microscope, germs were found in water and the 
theory of spontaneous generation of life aroused new interest. 
Pasteur made a thorough examination of this problem and showed 
that no spontaneous origin of life took place when the germs were 
excluded. 
Pasteur attained to his greatest success in his study of micro- 
scopic organisms, the "infinitely little," as he loved to call them. 
His first success was in the study of fermentation and diseases 
of wines. This was followed by his investigation of the silkworm 
plague. He then began the study of the prevention of disease, 
making a repeated series of pure cultures which rendered the germ 
less poisonous. This weakened germ he injected into animals 
to protect them from disease. He first tried this experiment on 
fowl cholera; then splenic fever; and after many years of experi- 
mentation he was successful in preventing hydrophobia in a human 
being that had been bitten by a mad dog. 
The Pasteur Institute was established in 1888, an event of great 
scientific importance. More than thirty similar institutes have 
since been established in different parts of the world on the plans 
that he formulated. Pasteur probably made more important dis- 
coveries which were directly beneficial to human welfare and health 
than any other man. BACTERIA IN RELATION TO MILK 
397 
hard to digest. Milk is not rendered absolutely sterile, but 
it is a much safer food, especially for infants. At best pas- 
teurization is only a corrective or precautionary measure, 
and we should demand that milk be kept clean and thus 
free from bacteria. 
Milk Products. - Most raw milk products have their own 
forms of bacteria, nearly all of which are helpful. The flavor 
of June butter is im- 
parted by a bacterium 
different from the one 
in January butter. So 
with cheese, each brand 
or flavor receives its taste 
through the action of a 
special bacterium. At 
every step in the use and 
manufacture of milk, it 
is necessary to know the 
conditions under which 
the helpful bacteria work 
best, and how to keep 
out the harmful ones. 
Sources of Danger in 
Milk. - The cow herself 
may be unhealthy and 
her disease transmitted through the milk. Of the several 
diseases which this animal may give, tuberculosis is the 
most common. Children are more liable than adults to 
take the disease in this way. There is no necessity to 
be in doubt about a cow's being infected with tuberculosis, 
for in 1890 Koch discovered the tuberculin test, which 
enables the dairyman to detect the disease. This test is 
now commonly applied, and in some cities owners of herds 
which have been tested and found free from disease are 
allowed to sell their milk as " certified," though the meaning 
Figure 258. 
The metal cap keeps out dirt which can 
get by the paper stopper. 398 
BACTERIA: THE SMALLEST PLANTS 
of this term varies. Not only is the raw milk from tuber- 
cular cows dangerous, but also the butter and cheese made 
from it. 
Bacteria multiply rapidly and remain active while milk 
is warm, consequently it should be cooled as soon as possible 
after it has been taken from the cow. Milk should not 
be used when it is too old, for in that case the harmless 
bacteria may all have died and harmful ones taken their 
places. Milk should not be left in a metal container, or 
open to the air, or placed in an ice chamber where it can 
absorb the odors of other foods. 
Ice cream should be eaten only when fresh, for poisons 
(ptomaines) are formed by the action of bacteria, especially 
in ice cream which has been melted and then refrozen. Ice 
cream should be made under clean and healthful conditions, 
and should never be exposed to the air of the street. 
279. The Preservation of Food. - The care of food is 
necessary to our health, for some of the germs which live and 
grow in food cause disease when taken into our bodies. After 
studying the habits of the different kinds of bacteria and 
knowing just what conditions are necessary for their growth, 
we can modify these conditions sufficiently to prevent the 
bacteria from growing or to kill them. 
Our aim in preserving food is to keep it from " spoiling." 
We say that food is spoiled or unfit for eating as soon as the 
processes of decay have begun. It is important to keep in 
mind that decay or putrefaction is always due to the growth 
of bacteria and similar organisms. Any device which will 
check the activity of bacterial growth will delay spoiling. 
The problem of keeping our food free from decay becomes 
increasingly difficult with the increase in population. The 
following are some of the methods used in preserving food: 
(a) Canning. - Canning is a simple plan of keeping bac- 
teria away from food products. The food is not treated by 
any chemicals to prevent the growth of bacteria, but reliance THE PRESERVATION OF FOOD 
399 
is placed entirely upon devices for keeping all bacteria from 
it. If this can be done, the food will not be subject to their 
action and will never spoil. 
The process involves, first, removing the bacteria already 
present in the food; and second, preventing all other bac- 
teria from gaining access later to the food. The first need 
is met by heating the food to a sufficiently high tempera- 
ture to destroy the bacteria; while the second is met by 
hermetically sealing the food in a can or jar while it is still hot. 
(6) Preservatives. - Preservatives are of two kinds, poison- 
ous and non-poisonous. The non-poisonous preservatives 
are sugar, salt, vinegar, and spices. The use of such pre- 
servatives is perfectly proper and their success in keeping 
bacteria from growing is due to the fact that bacteria do not 
grow in solutions containing these substances. Fresh fish 
are preserved by rubbing with sugar. Condensed milk 
contains 30% to 40% of cane sugar. Jellies are preserved 
from bacterial action by the large amount of sugar which 
they contain. Raisins, figs, and dates are preserved partly 
by drying and partly by the presence of sugar. These three 
fruits contain so much sugar that it is not necessary to add 
sugar while drying. In recent years housewives have been 
preserving fruit, especially berries, by taking equal parts of 
sugar and fruit and then sealing up the can without heat. 
The large amount of sugar prevents the bacteria from growing. 
Salt is one of the commonest and least harmful of pre- 
servatives and is used in a variety of products of which fat 
pork, corned beef, hams, and fish, are the most common. 
Vinegar is another material that is a well-known preserva- 
tive ; the various kinds of pickles and olives are usually 
thus protected. 
Many kinds of spices are in common use. These are more 
or less useful in protecting our food. This is well illustrated 
in mince-meat, which is a watery mixture of meat and fruit 
which under ordinary circumstances would readily putrefy. 400 
BACTERIA: THE SMALLEST PLANTS 
The spices give the needed protection and when they are 
omitted, the mixture soon decays. The same principle is 
applied in preserving sausage meat. 
All bacteria require a considerable amount of moisture 
for their life processes and cannot develop in moderately 
dry food. Nature has adopted this method of preserving 
the seeds of most plants. We find that the ripened seeds 
of grasses, wheat, corn and many other plants are dry. 
Flour is good food for bacteria only when it is moistened. 
The large amount of baked goods on the market to-day are 
protected largely because they are dry. Just as soon as 
bread is placed in water or moistened, it begins to decay. 
In the past few years a whole new industry has grown up 
around this principle of drying, with dried milk as one of 
the best examples. 
Finally there is the use of low temperatures, such as cold 
storage refrigerators or even freezing. Bacteria cannot grow 
at extremely low temperatures and the food can be preserved 
indefinitely. However, this method does not destroy the 
bacteria that are in the food. It simply checks their growth. 
280. Men Who Made the Study of Bacteria Possible. - 
The inventor of the microscope should be placed at the head 
of the list of men who made the study of bacteria possible, 
for without this instrument we should not know that such 
plants exist. We do not know who the actual inventor 
was, but the microscope was little more than a toy until 
it was improved by a Dutch naturalist, Leeuwenhoek (Lu'- 
wen-hook), in the latter part of the seventeenth century. 
Next in the study of bacteria comes Pasteur, who discovered 
and studied them in their relation to the souring of milk 
and in other fermentations. Then comes Koch, who dis- 
covered a way of separating bacteria so that each kind may 
be studied by itself, a method called getting a " pure cul- 
ture." He also invented the tuberculin test. Most of our 
facts about bacteria have been secured during the past HEALTHY BODIES AND BACTERIA 
401 
thirty-five years, since men have learned how to prepare 
them for study. 
281. Healthy Bodies and Bacteria. - So much has been 
said about harmful bacteria that a word of caution is needed. 
Two facts should make us take a sane view of the situation: 
(1) for every harmful bacterium there are thousands of 
helpful ones; and (2) harmful ones cannot do their work, or 
even live, in a perfectly healthy body, for such a body is 
constantly preparing a substance (antitoxin) which neu- 
tralizes the bacterial poison (toxin). Our chief aim, then, 
should be to keep well, and a few simple rules of hygiene will 
accomplish this. (1) Spend as much time as possible exer- 
cising in the open air. (2) Sleep as many as eight hours out 
of twenty-four in a well-ventilated room or out of doors. 
(3) Eat only food which agrees with you, and not too much 
of that. (4) Wear seasonable clothing. (5) Keep the skin 
clean through frequent bathing. (6) Have a definite occupa- 
tion, work faithfully at it, do your best, and don't worry. 
OUTLINE 
Bacteria 
Size 
Shape 
Round (cocci) 
Rod-shaped (bacilli) 
Corkscrew-shaped (spirilla) 
Where found 
Conditions of growth 
Life processes 
Reproduction 
Fission 
Production 
Enzymes 
Toxins 
Germicides • 
Soil bacteria 
Symbiosis 
Inoculation 
Bacteria and milk 
Pasteurization 
Milk products 
Danger in milk 
Tuberculosis 
Preservation of food 
Decay 
Due to bacteria 
Canning 
Preservatives 
Sugar 
Salt 
Vinegar 
Spices 
Drying 
Freezing 
Bacteriologists 
Pasteur 
Koch 
Healthy bodies and bacteria 402 
BACTERIA: THE SMALLEST PLANTS 
SUMMARY 
The smallest and simplest of all the plants are the bacteria. Most of 
them are helpful, ridding the earth of waste material, giving flavor to 
food, gathering nitrogen from the air for plants. Some bacteria are 
harmful and cause diseases in plants and animals. Bacteria are spheri- 
cal, spiral, or rod-shaped. They are found everywhere, unless special 
pains have been taken to remove them. If they have plenty of food, air, 
moisture, and warmth, they multiply rapidly, and they go into the 
resting state, in which they can remain for a long time if any or all of 
the necessary conditions of growth are lacking. The harmful bacteria 
during their growth secrete a poisonous substance, toxin. When there 
are enough bacteria present to make a large quantity of toxin, the 
animal or plant host is made ill. Some bacteria, especially in the rest- 
ing state, can bear freezing or boiling without being killed. In order 
to make anything "keep," it is necessary either to kill all the bacteria 
by making the substance sterile or aseptic, or to put into it a preserva- 
tive, a substance in which the bacteria cannot grow. We should use 
great care to avoid the bacteria known to produce disease. 
Milk, one of the most important articles of food, is a possible source 
of danger from harmful bacteria, which may get into it in various ways. 
Milk should be kept cold, and should be used before it is too old. The 
harmless bacteria in milk form lactic acid and cause the milk to sour. 
The growth of these bacteria can be checked by pasteurizing the milk. 
Ice cream, if too old, is dangerous, for the slow-growing bacteria have 
had a chance to develop. 
The men who did the most to make the study of bacteria possible 
were Leeuwenhoek, who improved the microscope; Pasteur, who dis- 
covered bacteria in milk, and Koch, who found the way to make a 
pure culture and to test cows for tuberculosis. Many students are 
devoting their lives to the study of the various bacteria. 
Every one should know the main facts about bacteria so that he may 
not have a foolish fear of them, but may be able to take reasonable pre- 
cautions against the harmful kinds. Since a healthy body is the best 
safeguard against harmful bacteria, we should observe the laws of hy- 
giene in order to keep well, and at the same time avoid, when possible, 
the bacteria which produce disease. 
QUESTIONS 
What are the main points of likeness between a bacterium and a 
flowering plant? How can food be protected from harmful bacteria? 
In what respects are bacteria harmful to milk ? In what respects helpful ? REFERENCES 
403 
Why are a few harmful bacteria not injurious in a healthy body? If 
one bacterium divides every half horn1, and all live, how many will there 
be at the end of twenty-four hours? (Solve by arithmetic or by alge- 
bra.) Why does an apple with a broken skin decay more rapidly than 
one in which the skin is not broken? Why should one not put ice into 
water to cool it ? 
REFERENCES 
Calkins, Biology, pages 37-40. 
Conn, Biology, pages 26, 80, 232, 235. 
Conn, The Story of Germ Life. 
Frankland, Our Secret Friends and Foes. 
Prudden, The Story of the Bacteria. 
Radot, The Life of Pasteur. 
Snyder, General Science, pages 209-218. 
U. S. Bulletin No. 56, Hygienic Laboratory Bulletin. Milk and Its 
Relation to Public Health. 
Woodhead, Bacteria and Their Products. CHAPTER XXV 
HEALTH 
Ah, what avail the largest gifts of Heaven, 
When drooping health and spirits go amiss ? 
How tasteless then whatever can be given! 
Health is the vital principle of bliss, 
And exercise of health. 
- Thomson 
282. Importance of Health. - The National Health 
Council estimates that the total loss in the United States 
annually from preventable diseases is $3,000,000,000. Under 
ordinary conditions about three per cent of the people are 
sick. While some of this sickness is due to diseases over 
which we have no control as yet, much of it is caused by 
parasitic animals and plants living in our bodies. Such dis- 
eases can be prevented by vigilance, cleanliness, and whole- 
some living, - in short, by sanitation. 
283. Kinds of Disease. - While there are many causes 
of disease, all of them may be grouped under four headings: 
(1) Inherited diseases, i.e. those transmitted from parent to 
child, as certain forms of insanity and imbecility. (2) Dis- 
eases caused by such poisons as lead, arsenic, mercury, phos- 
phorus, opium, cocain, alcohol, and the like. The dis- 
turbances which these chemical agents set up in animal 
tissues are easily recognized by a good physician. (3) Dis- 
eases which cause certain tissues to take on an abnormal 
growth, as in tumors and cancers. (4) Diseases caused 
directly or indirectly by some definite living plant or animal. 
Such diseases are called " biological diseases," because the 
source or cause is in all instances some definite living plant 
404 KINDS OF DISEASE 
405 
or animal. In our ordinary daily speech we often speak of 
such ills as " germ " diseases. 
Errors in Diet: Indigestion. - Besides these various 
diseases, there are many other ailments, of which the com- 
monest is perhaps indigestion. This is sometimes due 
to errors in diet or to careless chewing, but there are other 
causes. It often happens that we eat too much or are too 
Figure 259. - Tuberculosis Cure, Summer. 
tired when we eat. The fatigue that comes from overwork- 
ing is sufficient at times to hinder the normal digestive 
changes. The same result may follow anxiety or worry. 
Sudden fright may check the flow of gastric juice and thus 
prevent the digestive changes. If the cause of such inter- 
ruptions in the normal process of digestion is not removed, 
we become ill. So we see that unless food is digested, it 
cannot be absorbed. If it remains in the alimentary canal 
undigested, the bacteria which are normally present in the 
intestine begin to feed on it and decay sets in. 406 
HEALTH 
284. Biological Diseases. - The rattlesnake secretes a 
poison which is forced through fangs or hollow teeth into 
the blood of its prey. This poison affects the heart and 
may result in death. One of the common and beautiful 
mushrooms produces a similar poison which is not destroyed 
by cooking. If this particular mushroom is eaten, death 
is almost certain to follow in from twenty-four to forty- 
eight hours. In both these cases the animal or plant is 
large enough to be seen and easily recognized. 
But there are a considerable number of microscopic plants 
and a few microscopic animals that have formed the habit 
of living for at least a part of their life in other plants and 
animals. During this time, as we have seen in the study 
of animal and plant parasites, they usually secure all, or the 
greater part, of their food from the plant or animal in which 
they are living. Two general causes of disease result from 
this parasitic habit. The parasite may destroy certain cells 
of the body, or the material thrown off from the body of the 
parasite may act as a specific poison. 
285. Communicable Diseases. - The term communicable 
disease 1 is used in this book to mean the diseases caused 
by a plant or animal living as a parasite in plants, animals, or 
man. These diseases are communicated in various ways 
from one individual to another, from one animal to another, 
or from one plant to another. 
The following are among the most common communi- 
cable diseases. Diseases caused by bacteria (minute plants) 
are tuberculosis, pneumonia, diphtheria, typhoid fever, 
1 New York State designates the following as communicable diseases: 
anthrax; chickenpox; cholera, Asiatic; diphtheria (membranous croup); 
dysentery, amoebic and bacillary; epidemic cerebro-spinal meningitis; epi- 
demic or streptococcus septic sore throat; German measles; glanders; 
measles; mumps; ophthalmia neonatorum; para-typhoid fever; plague ; 
poliomyelitis, acute anterior (infantile) paralysis; puerperal septicaemia; 
rabies; scarlet fever; smallpox ; trachoma; tuberculosis; typhoid fever; 
typhus fever; whooping cough. Professor Theobald Smith (1859, still living) is a technical 
scientist. Before any physician knew how to prevent disease, 
technical biologists had to discover how the disease germs live. 
Such is the work of Professor Smith, and he is an acknowledged 
authority in his field. 
His best known discoveries are as follows : 1. He discovered 
that the protozoan parasite in the blood of cattle which causes 
Texas cattle fever is also found in ticks. It is carried from one 
cow to another by the infected ticks. This discovery led to simi- 
lar discoveries in Malaria, Sleeping Sickness, and other protozoan 
diseases. 2. His scholarly researches in human tuberculosis 
have been of great value to mankind. 3. Present standards of 
meat inspection are based upon his investigations into the dis- 
eases of cattle and other food animals. 4. He was a pioneer in 
the manufacture and extensive public use of antitoxin. COMMUNICABLE DISEASES 
407 
bubonic plague, and whooping cough. Measles and scarlet 
fever are so similar to these in many ways that it is believed 
that they are caused by bacteria, although the definite bac- 
teria which cause them have not been discovered. Dis- 
eases caused by protozoa (minute animals) are malaria, 
yellow fever, sleeping sickness, possibly smallpox, and others 
less well known. 
Figure 260.- Tuberculosis Cure, Winter. 
Manner of Infection. - The biological diseases are all 
preventable, especially the communicable diseases which 
result from the parasitic habit of some plant or animal. In 
order to prevent people from being infected with these dis- 
eases, it is necessary to know how the different plants and 
animals gain access to the human body and proceed to live 
there. This can be illustrated by describing pulmonary 
tuberculosis, a plant or bacterial disease; and malaria, an 
animal or protozoan disease. 408 
HEALTH 
286. Pulmonary Tuberculosis. - Pulmonary tuberculosis 
is a disease located in the lungs. The cause is a definite 
plant with parts and habits which are easily recognized by 
bacteriologists (students of bacteria). This plant is called 
Bacillus tuberculosis, and was proved to be the cause of 
consumption, or tuberculosis, by Robert Koch, a German 
scientist, in 1882. These tuberculosis bacteria, or germs, 
Photographed by Henry Jones. 
Figure 261. - Bacilli of Tuberculosis. 
in countless numbers are found leading a parasitic life in 
the lungs of a tubercular patient. The bacteria are ex- 
tremely minute, and can be seen only by the use of a micro- 
scope of high power. 
The large number of germs in the lungs grow rapidly, 
and they are set free in the air by coughing. One tuber- 
culosis patient may give off millions of these germs in a 
day. For this reason great care should be taken in destroy- PULMONARY TUBERCULOSIS 
409 
ing the sputum of patients, for if the germs become dry, 
they are carried about as dust particles. 
Tuberculosis and other disease germs are so numerous 
that it is impossible to escape taking some of them into our 
bodies, but they usually do us no harm unless we are in a 
weakened condition. 
Modern methods of cleaning the streets by flushing with 
water, keeping garbage covered, and wiping up the dust 
in our homes instead of using the old-fashioned feather 
duster are doing much to keep down the number of germs 
in the air which we breathe. 
The bacteria that are breathed in from the air may find 
some weak place in the lungs in which to take up their para- 
sitic lives. Those which enter on the food pass from the 
digestive tract into the blood and are eventually carried 
to the lungs. The introduction of tuberculosis germs in 
this way is especially frequent in children. In many cases 
milk from tuberculous cows is the source of the germs. 
The cause of pulmonary tuberculosis is, then, the tubercle 
bacillus, which is taken into the lungs in the air we breathe, 
or through the food eaten, or by personal contact with a 
consumptive patient. These germs cause certain parts of 
the lungs to become diseased. 
Getting Well. - Consumption is not necessarily fatal, 
especially if treated in its earliest stages. But many people 
who have the disease do not consult a regular physician 
until it has made considerable progress, and then it is too 
late to bring about a cure. 
Figures 259 and 260 show the present method used in 
treating tuberculosis. The patients are given tissue-build- 
ing food (protein) and are required to sit and sleep out- 
of-doors as much as possible. Rest, good food, and fresh 
air work wonders in arresting the progress of this disease. 
When the body gains the requisite amount of strength 
the disease and its germs are usually thrown off. Patent 410 
HEALTH 
medicines and alcohol should be avoided, as they reduce 
the power of the body to resist disease and give no aid in 
building up the diseased tissues. In addition, alcohol causes 
serious disturbances in the general circulation. 
In addition to pulmonary tuberculosis physicians recog- 
nize tuberculosis of the throat, intestines, kidneys, brain, 
and joints. 
287. Influenza. - This is a communicable disease that 
killed more than 550,000 people in the United States during 
the fall of 1918 and the winter of 1919, which is about five 
times the number (111,179) of American soldiers officially 
stated to have lost their lives from all causes in the World 
War up to the date of April 30, 1919. This disease is con- 
tracted only by those who come in contact with the secretions 
from the nose or bronchial tubes of one who is affected with it. 
The word contagious is properly used for such diseases, be- 
cause the person suffering from them gives off germs that 
pass to another. In this same sense tuberculosis, diphtheria, 
and typhoid fever are contagious diseases. 
When the disease is of average severity the symptoms are 
a chilly sensation, headache, and " bone ache," or pains all 
over the body, and fever. Coughs usually develop as the 
progress of the inflammation extends into the bronchial tubes. 
The full force of this disease may center in the respiratory 
organs, or in the muscles and nerves, or in the digestive 
tract. It is clear that influenza paves the way for pneu- 
monia, if it does not actually produce it. 
The mouth and nasal passages should be kept clean with 
such washes as salt in water or borax in water in the pro- 
portion of one level teaspoonful to a pint of water. The 
chief value of all nasal washes is the water, and any prepara- 
tion that has a smarting reaction should be avoided. There 
is really no special method of cleaning the nose that excels 
the natural method, i.e. blow it, and blow it into a paper 
napkin and burn the napkin. MALARIA 
411 
This disease spreads in epidemic form about once in a 
generation throughout the earth along the routes of travel, 
and is carried from place to place by man. The name 
Influenza was given to it in Italy about one hundred years 
ago, because it was supposed to be due to the influence of 
some malevolent agent of the air. The French term " La 
Grippe " is given to this same disease; while the expression 
Spanish Influenza simply means that the 1918 epidemic 
started in Spain or was first noticed in epidemic form in 
Spain. 
Home Report. - Look up the ravages of influenza in India, 
Alaska, etc.1 See what you can find out about the total 
number of deaths in the different nations of the world. 
288. Malaria. A Protozoan Disease. - Malaria is a dis- 
ease caused by a protozoan or minute animal which is dis- 
tributed over the greater part of the world. The malaria 
protozoon is a minute simple cell of living matter. It resem- 
bles the amoeba in its form and ability to change. This 
parasite penetrates into the red blood corpuscles and remains 
in them for twenty-four or forty-eight hours, or until the sub- 
stance of the corpuscle is nearly used up. Then the parasite 
escapes into the plasma of the blood and later enters a 
fresh corpuscle. 
Source of the Malarial Parasite. - The word malaria means 
bad air, for it was formerly believed that foul air caused the 
disease. When it was learned that a definite animal was 
the cause both in man and in other animals, the problem 
was to find how the parasite entered the body. It has been 
proved to the satisfaction of scientists that the malarial 
protozoon is injected into the blood by a particular kind of 
mosquito (Anopheles) which carries malaria germs in its 
body. (See page 83.) 
The mosquito sucks the blood from a man or an animal 
1 Influenza Studies by Raymond Pearl. Reprint No. 548, Public Health 
Reports, Treasury Department. 412 
HEALTH 
suffering from malaria. This blood contains some of the 
malarial parasites, which pass into the stomach of the mos- 
quito. They then migrate into the salivary glands of the 
mosquito, so that as soon as the mosquito bites another 
man or animal, it pours out some saliva which introduces 
the parasites into the victim's blood. While in the body 
of the mosquito, these parasites pass through definite stages 
in their life history; 
and when they reach 
the blood of man, 
the remaining stages 
are completed. Thus 
a man, or an animal, 
and a particular mos- 
quito are necessary 
for the complete life 
history of the mala- 
rial parasite. 
This means in ad- 
dition that for the 
prevention of malaria 
all that is necessary 
is to prevent the 
Anopheles mosquito 
from breeding, or in 
case this cannot be 
done, to screen ade- 
quately the houses, 
tents, and bedrooms 
in the regions where the mosquitoes live. It is interesting to 
note that the methods for the prevention of malaria were 
more than anything else responsible for the successful com- 
pletion of the Panama Canal. The construction of this im- 
portant work thus became a health as well as an engineering 
problem. 
Courtesy Bureau of Fisheries. 
Figure 262. - Mosquito-destroying Fish. MALARIA 
413 
The cause and prevention of malaria is easily understood 
now that scientists have found out just how this protozoan 
animal lives. Each of us can protect himself from mos- 
quito pests wherever we live. This blessing we can better 
appreciate when we study the importance of these animals 
in determining the history of ancient peoples. In ancient 
Egypt, for example, the natives in the marshy regions built 
towers in which to sleep because the mosquitoes did not fly 
so high. Records show that at least three kings were com- 
pelled to withdraw their troops when they were besieging 
ancient cities because of the prodigious number of " gnats." 
The history of Rome records periodic outbreaks of malaria, 
and the " deadly Campagna " was a marshy region that 
was more destructive than war to those who lived near it. 
It is not strange, then, that the Romans had a goddess of 
fever which they tried to propitiate. 
As long as mosquitoes were regarded merely as pests, little 
effort was made to exterminate them, but as soon as it was 
discovered how destructive they are of human life, men 
everywhere began to study methods to eradicate them. In 
the numerous experiments that have been made to learn 
the true relation of mosquitoes to disease, men instead of 
animals have been used. Living mosquitoes which had 
bitten men with malaria were allowed to bite men who did 
not have this disease. These men then came down with 
malaria. In the 'same way yellow fever was proved to be 
caused by the mosquitoes technically known as Aedes but 
formerly named Stegomyia. 
The moral courage exhibited by these men is equal to 
the bravery of heroes in battle. This small group of less 
than a dozen men who permitted themselves to be experi- 
mented upon has saved thousands of lives and enabled man 
to make regions, formerly uninhabitable, places where man- 
kind can live in safety and freedom from the fear of these 
diseases. 414 
HEALTH 
289. Quarantine.1 - When a person or a group of persons 
is suffering from a communicable disease, or when any one 
has been exposed to the germs of any such disease, the 
Board of Health may place him under quarantine. The 
nature of the quarantine depends on the specific disease 
and the laws of the town or state in which the disease is 
prevalent. 
The New York law2 on this subject is typical of the best 
state laws on quarantine. It says : 
" The Board of Health shall prohibit and prevent all 
intercourse and communication with or use of infected 
premises, places, and things; and require, and, if necessary, 
provide the means for the thorough purification and chang- 
ing of the same before general intercourse with the same 
or use thereof shall be allowed." 
This means if an individual is suffering from scarlet fever 
or diphtheria, or some other communicable disease, he shall 
not associate with the general public until he has ceased to 
be a source of infection. His liberty is temporarily restricted 
by quarantine because he may be the cause of sickness and 
even death to others by spreading the germs of communicable 
disease. 
It is interesting to know that the more highly civilized 
a nation, state, or city becomes, the more specific and exact- 
ing are the quarantine regulations. There is every reason 
to believe that in the near future the present laws of quaran- 
tine will be extended. In addition to individuals being 
quarantined in a dwelling, all the inhabitants of a city or 
state may be quarantined in case of severe epidemics; or 
the transportation of stock from one state to another may 
be prohibited in the case of a serious communicable disease 
1 When practicable, it is well to have the local health officer discuss such 
subjects as disinfection and quarantine. 
2 The Sanitary Code of the Public Health Council of the State of New 
York defines the health officer's duties in detail and may be had by writing 
to the State Department of Health at Albany. THE WORM GROUP 
415 
existing in cattle or sheep. The quarantine laws, for ex- 
ample, order from time to time that all dogs in the town or 
county shall be muzzled as a protective measure against 
rabies. 
Immigrants suffering from certain diseases are prohibited 
from landing in the United States. This means that there 
are national as well as state and city quarantine laws. The 
present quarantine laws are the most effective protective 
measures against the spread of disease known to man and 
are the product of a high degree of civilization. 
Violation of quarantine and of the various health regu- 
lations, such as the pollution of water and improper care 
of refuse and sewage, should be reported to the local health 
officer. In case no satisfactory results are obtained from 
the local health officer, the question may be referred to the 
State Board of Health, which gives prompt and efficient 
attention to all questions concerning the health of the people 
of the state. 
290. The Worm Group. - The word " worm " is an old 
term which properly describes such animals as the earth- 
worm, sea-worm, leech, tapeworm, flatworm, and a few 
Figure 263. -• Flatworm. 
others. The word " worm " cannot be correctly used for 
such larvae of insects as the " apple tree worm " or " currant 
worm." 
The worm group is divided into two classes: those whose 
body is composed of numerous segments (seg'ments) or rings, 
such as the earthworm, and those whose body is not seg- 
mented, such as the tapeworm and flatworm. The first 
class comprises the true worms, which are known as Annelida 
(a-nel'i-da). The second class, the unsegmented worms, 416 
HEALTH 
have no single technical name, and are not believed by 
scientists to be true worms. They comprise a number of 
worm-like animals which have hardly any features in com- 
mon. Here are found the fresh-water planarians, the para- 
sitic tapeworms, liver flukes, hookworm, and numerous 
round worms, of which the hair worm is an example. 
Figure 264. -Hair Worm Living as a Parasite in the Body of the 
Grasshopper. 
291. Tapeworm. - In their structure and habits tape- 
worms are all much alike. (See Figure 265.) A mature 
tapeworm consists of numerous segments, often many hun- 
dred. Its " head " is armed with hooks or suckers or both, 
by means of which it holds on to the wall of the intestine. 
The remainder of the body floats freely in the digestive 
fluids and absorbs such nourishment as the worm requires. 
The segments at the free end of the body become ripe and 
drop off. The word ripe is used here to mean that the eggs 
have matured and are ready to give rise to more tapeworms. 
Each of these eggs, which has already begun to develop, is 
surrounded by a tough sac. This is as far as it can go in its 
growth unless it is eaten by another animal. The young 
tapeworms in their sac do not search for the animal that is 
necessary for their further growth and, unless accidently 
eaten, they die. As soon as the young tapeworm enters the TRICHINA 
417 
intestinal tract of the second animal (the second host), the 
tough sac is lost and the young worm begins to migrate into 
the tissues. In the tissues, it passes through more changes 
in growth but is still small and unlike its parent. 
Here it must remain until finally discharged and eaten by 
an animal similar to the one from which the eggs escaped. 
As it enters the intestinal tract of the first host, the strange 
young worm transforms into a 
worm like the parent. A single 
adult tapeworm may discharge 
millions of eggs. 
Such parasitic worms injure 
the mucous membrane lining 
of the intestine, permitting the 
entrance of bacteria and some- 
times causing ulcers. They ab- 
sorb much food, usually causing 
a ravenous appetite, and may 
even have a poisonous effect. 
Prevention is secured by abstaining from eating raw meat, 
which is the only source of infection for human beings. The 
commonest tapeworms found in man are the beef tapeworm 
and the pork tapeworm. 
292. Trichina. - Another unsegmented worm that is of 
economic importance is the Trichina (tri-ki'na), now gen- 
erally called Trichinella (tri'ki-nel'la). This worm lives in 
the intestine of mammals and from the intestine migrates 
into the muscles of its host. In the muscle it becomes en- 
cysted and remains until the flesh is eaten by some other 
mammal. When pork, infected with this parasite and in- 
sufficiently cooked, is eaten by man the cysts are dissolved 
by the digestive fluids and the worms are freed. 
These worms then develop eggs and sperms, which after 
uniting mature into young worms and migrate through the 
intestine into the muscles. The activity of the worms at 
Figure 265. - Tapeworm. 
Showing hooks in head. 418 
HEALTH 
this stage causes a serious inflammation of the tissues and 
a disease known as trichinosis (trik-in-o'sis), which is often 
fatal. Hogs contract trichinosis by eating refuse that con- 
tains the encysted worms. 
Government inspectors examine pork which is to be ex- 
ported or sold in large quantities to see that it is free from 
these parasites. The 
smaller sales of pork by 
local dealers are not in- 
spected, and the only way 
to be sure of the harm- 
lessness of the meat is to 
cook it thoroughly. 
293. Hookworm Dis- 
ease. - This disease is 
caused by a parasite which 
is classified as one of the 
worms. Hookworm dis- 
ease belts the earth in a 
zone which extends thirty- 
three degrees each side of 
the equator. This dis- 
ease is important because 
of its enervating effect 
upon the people suffering 
from it. It makes them incapable of work, and in the bodies 
of children results in a pitifully stunted growth. Great 
progress is being made in the United States in curing those 
suffering from this disease. The wearing of shoes and the 
use of a sanitary closet are usually sufficient preventives to 
protect the people who live in a hookworm district. 
294. Immunity. - Immunity is a technical term which 
means that the body resists or is not susceptible to the germs 
of biological diseases. Many persons do not become sick 
when there is an epidemic of typhoid fever, measles, malaria, 
Trichinella 
Cljst 
Muscle 
A picture of this parasitic worm in the 
muscles of man. Note the membranous 
sac which incloses it. This is the form 
of the sac after the worm comes to rest 
in the muscles. The worm is then said 
to be encysted. 
Figure 266.-Trichinella. VACCINATION 
419 
or the like. Such persons are said to possess a high degree 
of natural immunity to disease germs. Healthy people will 
frequently take germ diseases when the body happens to be 
exhausted by care or work. In such cases the immunity of 
the body has been weakened. In contrast with natural 
immunity is acquired immunity. This is usually secured 
through the use of antitoxins (serum therapy), although 
many of the germ diseases confer immunity against a second 
attack of the same disease, but this does not hold true for 
all persons or for all germ diseases. Vaccination against 
smallpox, in the case of most persons, confers immunity for 
about seven years. Inoculation with the typhoid serum 
confers immunity for possibly two. Immunity, then, is a 
relative term, and depends in a large measure on the state 
of health of the individual and on his power of resisting the 
poisonous effects of disease germs. 
Student Report 
Fill in the blanks below. In cases which you do not know about, 
consult medical books or the encyclopedia. 
Due to Some Plant or Animal Treatment by Prevented by 
In the water 
From contact 
Nature 
Medicine 
Antitoxin 
Personal care 
Quarantine 
Boiling the water 
Fumigation 
Killing flies 
Cold 
Measles . . . . 
Whooping cough . 
Typhoid fever . . 
Tuberculosis . . 
Add others . . . 
295. Vaccination. - The success which has attended the 
efforts of man to overcome disease is well illustrated by 420 
HEALTH 
smallpox. For centuries this disease was responsible for 
many deaths throughout the world. It is said to have ex- 
isted in China centuries before Christ. Later it swept over 
Europe again and again. A famous French physician wrote 
in 1754 that every tenth death was due to smallpox, and 
that one fourth of mankind was either killed by it or dis- 
figured for life. Smallpox was brought into the Western 
Hemisphere soon after the discovery of America, and killed 
thousands of the Indians. It also affected the colonists. 
In 1721, Boston was ravaged for the sixth time by this dis- 
ease. Out of the 10,567 inhabitants, 5989 had the disease 
and 894 died. 
In 1796, Jenner, an Englishman, demonstrated the fact 
that by inoculation of a person with cowpox, a disease pecul- 
iar to cows and in some way allied to smallpox, the patient 
would become immune to the dreaded disease. This was 
one of the greatest and most beneficial discoveries about 
disease which has ever been made. 
As the result of vaccination and sanitation smallpox has 
become a rare disease in the civilized nations of the world, 
and is least prevalent where the vaccination laws are the 
most stringent. 
Vaccination for smallpox consists in the inoculation of 
the human patient with vaccine, a substance secured from 
a cow suffering from cowpox. This usually causes a slight 
illness, but during the illness the patient acquires a power 
which enables him to resist the germs of smallpox. This 
acquired power of resistance is called immunity. Im- 
munity secured through vaccination or through having a 
disease, such as whooping cough for example, is described 
as acquired immunity to distinguish it from that form of im- 
munity to all diseases or to certain diseases which many 
people possess. This latter is natural immunity. Those in 
the class who have not had measles may be said to have a 
natural immunity against measles. Those in the class who ANTITOXIN 
421 
have had measles once have an acquired immunity against 
measles. 
Many people do not understand the theory of vaccina- 
tion and its advantages, and have opposed its use through 
fear of acquiring lockjaw from the vaccine. It has been 
established that proper vaccine matter never contains the 
germs of lockjaw, and if this disease then occurs, it is due 
to failure in keeping the arm clean during the period when 
the vaccination scar is forming. 
Immunity to disease is now being produced through 
inoculation. The patient is inoculated, that is, there is 
introduced into his circulatory system a virus, or serum. 
Each disease has its own virus, as the vaccine in smallpox, 
and this virus produces a mild form of the disease. This 
causes the cells to become resistant to the germs or microbes 
of the specific disease. Inoculation is being widely used for 
the prevention of typhoid fever. All soldiers are required 
to take this treatment. It would be desirable for all people 
to become immunized against this disease, but those who 
travel extensively and thus have to drink all kinds of water 
and milk should certainly undergo this treatment. 
Vaccination and immunization reduce the liability of 
death in case the disease is acquired, but they do not abso- 
lutely prevent the disease. If a vaccinated or immunized 
person gets an overwhelming number of germs, he may have 
an infection of a slight kind. But the liability of contagion 
is reduced to a minimum. 
296. Antitoxin. - We cannot say definitely why vaccina- 
tion and immunization act as they do. It is known that 
if a poison (toxin) produced during a case of diphtheria is 
gradually introduced into the blood of a horse, a substance 
is produced which destroys the injurious effects of the diph- 
theria poison. The serum from the blood of the horse is 
called antitoxin, and may be preserved for use at any time 
to destroy the influence of the diphtheria poison. A given 422 
HEALTH 
amount of this antitoxin is introduced into the blood of the 
patient suffering from diphtheria, and usually counteracts 
the poison of the disease. This treatment has saved count- 
less lives. It is estimated that in the ten years following 
the discovery of the diphtheria antitoxin the lives of a million 
children were saved in France alone. State boards of health 
usually furnish antitoxin for diphtheria and lockjaw. 
297. Sanitation in the Home. - All of these wonderful 
discoveries about the cause and the prevention of disease 
fail to help us much unless we do our part. This we can 
do by first, becoming intelligent about the facts which 
scientists have discovered; and second, by applying proper 
sanitary measures in our homes. It is a fact that the health 
conditions in the country in recent years are not as satis- 
factory as those in our cities where stringent laws require 
the proper disposal of all wastes. 
Our food must be protected from rats, mice, and flies, as 
each of these animals carries disease. The presence of any 
of these three animals about your home is an indication that 
there is plenty of exposed food for them. You cannot ex- 
pect to have a clean home under such conditions. 
The study of bacteria reveals that they are carried about 
on dust particles. It is a common experience that colds 
and influenza spread more rapidly when there are strong 
winds and no snow in late fall and early spring. These 
are conditions that we cannot control, but excessive amounts 
of dust in the cleaning of our homes may be prevented by 
using proper methods of sweeping and dusting. 
We are coming more and more to use vacuum cleaners for 
all public places and there is no better method of removing 
dust from our homes. If a vacuum cleaner cannot be 
afforded, the room should be dusted with a damp cloth 
after it has been swept. In this case, it is necessary to wait 
until the dust has settled. Rugs and draperies hold a great 
deal of dust and should be taken out of doors and well ANTISEPTIC LOTIONS AND GARGLES 
423 
cleaned. Hard-wood floors are more hygienic than carpets 
because they can be cleaned more easily. 
298. Disinfection and Disinfectants.1 - The time when 
disinfectants shall be used and the manner of disinfection 
have been considered important factors in preventing the 
spread of communicable diseases. The purpose of disin- 
fection is to destroy the germs lodging on clothes, floors, 
carpets, and curtains. People who care for the sick should 
know where the germs are likely to be and how to disinfect 
places where they have found lodgment. The term disin- 
fectant is sometimes incorrectly applied to deodorizers, sub- 
stances which are used to destroy odors, but the word should 
be applied only to substances which destroy germs or bac- 
teria. 
Disinfectants are not expensive, and few of the patented 
preparations are as satisfactory as the common ones used 
by boards of health. Weak solutions of carbolic acid and 
bichloride of mercury are chiefly used for killing the germs 
on the hands and clothing, or for cleaning the woodwork in 
the sick room. Chloride of lime is used to kill the germs 
in the discharges of the body, and sulphur dioxide and 
formaldehyde gas for the final killing of the germs in the 
room or the whole house before it is occupied again. 
Never use any methods of disinfection unless they have 
been personally recommended to you by a physician or an 
expert in the details of room disinfection. 
299. Antiseptic Lotions and Gargles. - This is a subject 
about which there is a difference of opinion. Let us examine 
the scientific facts involved and then see to what extent such 
preparations are beneficial. The germs which are causing 
a sore throat, for example, are living on the membrane which 
1 It takes five pounds of sulphur to disinfect a room which contains 1000 
cubic feet of air. Three ounces of forty per cent formalin, to which is added 
two and one tenth ounces of potassium permanganate, will also disinfect 
the same sized room. Compare the cost and ease with which each is used. 424 
HEALTH 
lines this passage. The cells in this tissue are delicate and 
easily injured. In our study of bacteria, it was shown that 
only extreme poisons or prolonged heat was sufficient to 
kill them. Any poison that is powerful enough to kill the 
germs when used as a gargle will cause very serious injury 
to the cells in the tissues of the throat. When we use one 
of the many so-called antiseptic gargles, then, we do not 
kill the germs. What does happen? 
These germs are washed free to some extent from the sur- 
face of the throat but not from the folds of the tissue as in 
the tonsils. Is there any remedial property to these gargles? 
In nearly all cases, there is not. What is the proper gargle 
to use? The one most employed now is salt and water. 
Such a gargle is cleansing and stimulating. These are the 
two important results to be obtained by a gargle. 
The same principle applies to lotions which are used in 
the cases of bruises especially. None of the lotions have 
any more cleansing effect than soap and water. Camphor 
and witch hazel are old-time lotions that are still used. Both 
of them contain a large amount of alcohol. It is the alcohol 
that is the stimulating agent in these two lotions. It causes 
the skin capillaries to expand and thus permit the blood to 
flow more freely. 
Any antiseptic which will actually kill the germs is really 
a disinfectant (already discussed on page 423). 
300. Emergency Treatments. - We often have minor 
accidents to which we can give temporary care. 
Cuts and Hemorrhages. In the case of serious bleeding, 
the skin will be broken and we already know that the wound 
must be kept as clean as possible. As a rule you will not 
have at your command sterile dressings, so it is better not 
to wash, touch, or put anything into a serious wound unless 
a doctor cannot be found. 
The small veins and capillaries when injured do not cause 
serious bleeding or hemorrhages, but when the blood spurts EMERGENCY TREATMENTS 
425 
out or flows in a stream, then it is necessary to apply the 
tourniquet. This is a device which exerts a heavy pressure 
on the blood vessel and thus stops the bleeding. As it must 
be long enough to tie around a limb, a big handkerchief, 
towel, or wide bandage may be used. There must be a pad 
to make the pressure over the artery or vein greater than on 
the rest of the limb. The tourniquet must be put on tight 
enough to stop the bleeding and is rarely made too tight. 
Usually this should not be left on for more than an hour. 
Bruises. The best cure for bruises is rest. Sometimes 
the application of a soothing lotion helps to relieve the pain, 
but only time can replace the injured cells. 
Burns. The usual burns are accidents that injure the 
skin only. If the burn is deeper than this, it will require 
medical attention, and the best care that you can give is to 
do nothing. The smarting and burning sensation from super- 
ficial burns can be lessened by applying olive oil or a paste of 
baking soda. If the burn is kept free from dirt, it will readily 
heal without any special treatment. 
Fractures. - In the case of fractures the injured part should 
be kept as quiet as possible. Any movement in the broken 
limb is likely to increase the difficulties of healing. The 
best treatment is to try to keep the part unmoved until a 
physician arrives. If it is necessary to move the injured 
person, a temporary splint should be applied. Anything 
that is stiff and rigid may be used, such as shingles, limbs of 
trees, umbrellas, or wire netting. In applying the splint, 
it must extend if possible beyond the joint below and the 
joint above the break in order to prevent movement in the 
broken parts. Such splints can be tied in place with hand- 
kerchiefs, strips of clothing, or bandages. Do not tie di- 
rectly over the break. There must be an inner and outer 
splint when the break is in the arm or leg. 
Poisons and Neutralizing Agents. - It occasionally hap- 
pens that some one by accident takes poison, and it is im- 426 
HEALTH 
portant to know what to do until a physician can be secured. 
The first thing to do is to empty the stomach by an emetic. 
A glass of warm water with as much common salt as will 
dissolve in it or a teaspoonful of mustard in a large quantity 
of warm water will usually start vomiting. As soon as the 
stomach has been emptied, some neutralizing agent should 
be swallowed. In case an acid or corrosive sublimate has 
been swallowed, its action causes injury to the mucous 
membrane. Epsom salts, soap, or white of an egg followed 
by castor oil is beneficial. Young children may eat match- 
heads which contain phosphorous. This substance is also 
in some rat poisons. In this case use an emetic, preferably 
sulphate of copper, one to three grains in solution every 
ten minutes. After the patient has vomited use epsom 
salts, but no oil. 
Prevention is the best neutralizing agent, and this can be 
accomplished by leaving nothing of a dangerous nature in 
easily accessible places. 
301. Keeping Well. - The object in studying the pre- 
ceding material in this chapter is to teach us to keep well. 
Our best doctors are spending much effort in showing how 
to avoid disease, for no one is benefited by illness. The old 
notion that children should be exposed to measles, scarlet 
fever, and whooping cough is wrong, for none of these child- 
hood diseases is necessary. The time will come when our 
homes and surroundings will be so sanitary that the common 
diseases caused by germs will be eliminated, or at least de- 
creased in number. 
Government inspection of meats is lessening the amount 
of disease contracted from eating diseased pork, other meat, 
and fish. The United States Department of Agriculture is 
making every effort to inspect such products, and the de- 
partment is fairly successful in inspecting the larger estab- 
lishments. Many cattle and hogs, however, are killed and 
sold locally, and they escape inspection, so that buyers of this SAVE THE CHILDREN 
427 
meat have no protection against a general condition of 
disease. 
Another danger to health is from the people known as 
" carriers " of disease, as such people give no evidences of 
illness. Typhoid and diphtheria are the two diseases most 
likely to be carried in this way. Many of these carriers 
serve as cooks, and as they give no evidence of being in 
other than perfect health, they often spread the germs 
through the food they prepare. If habits of absolute clean- 
liness are insisted upon, much of the danger of the dissemi- 
nation of germs in this way may be removed. 
Many hotels, public institutions, and well-run house- 
holds insist that a prospective servant shall be examined 
by a competent physician before being engaged for work. 
In this way carriers may be detected, and persons with 
germ diseases, like tuberculosis, for instance, are prevented 
from spreading disease either in the food or in the air. 
Children in the schools frequently have diphtheria germs 
living in their nasal passages or throats, but are not ill. 
After a time a number of children are stricken with the dis- 
ease. A doctor then takes a sample of the contents of the 
throat and nose of each child. The bacteria in the mucus 
from the nasal passages are allowed to grow for twenty-four 
hours in a special preparation called a culture. At the end 
of that period the cultures are stained and examined with a 
high power microscope, and if diphtheria germs are present, 
they are easily seen. If one of the well children has these 
germs, he is treated until they disappear. 
302. Save the Children. - The care which animals take in 
the protection of their young is one of the most fundamental 
instincts of their nature. But in civilized man his instinct 
is broadened and controlled by the power of reason and a 
knowledge of the laws of hygiene. Until man came to 
understand these laws, many of his efforts to protect his 
young were of no more avail than the brave fluttering and 428 
HEALTH 
plaintive cries of a bird when a red squirrel is robbing 
her nest. 
During the last decade there has been an attempt to re- 
duce the death rate among children. It is lower in America 
than in most countries of the world, and in this fact we take 
pride. The state of New York has the lowest death rate 
among children of any state in the world of which we have 
accurate knowledge. Yet there are communities in this 
state where the waste of infant life is a disgrace to civiliza- 
tion. The centers where this high death rate exists are 
largely populated by foreigners whom we permit to live in 
unhygienic conditions. 
In a study of 9912 deaths among infants in New York 
State for the year 1916, over 55 per cent, we find, died from 
measles, whooping cough, bronchitis, pneumonia, broncho- 
pneumonia, and infantile diarrhea. All of these are due in 
large part to parental ignorance concerning the elementary 
facts of sanitation and the proper care and feeding of infants. 
The infantile mortality among the foreign-born mothers is 
much greater than in the native white mothers. Particularly 
high death rates prevail among the Polish, German, and 
Austrian mothers. 
It is difficult properly to measure the value of health to 
the community. When the wage earner is sick and is placed 
in quarantine, the loss of money is the amount he might 
have earned. In the case of a typhoid fever epidemic the 
total loss is many thousands of dollars. Further, there is 
no adequate measure of the sufferings of those who die and 
the heartaches of those who survive. But both the suffering 
and the financial loss can be greatly lessened by improving 
our sanitary laws and aiming at a better state of health for 
all the people. An increase in taxes to provide cleaner 
streets, public playgrounds, proper sewage disposal, and 
adequate inspection of milk, meat, and water, is really an 
economy. For although such improvements cost money, EPIDEMICS AFTER WARS 
429 
they are not so expensive as epidemics of disease and the 
maintenance of hospitals and of orphan asylums. 
303. Epidemics after Wars. - The return of two million 
men from Europe after living there for several months, to 
scatter throughout the United States, raised public health 
questions of great interest. After the Crimean War (1854- 
1856), cholera was epidemic in France and England ; after the 
Franco-Prussian War (1870-1871), smallpox was epidemic in 
IF 
THESE CASES 
MAD BEEN REPORTED 
THESE CASES 
WOULD NEVER HAVE OCCURRED 
Figure 267, - Story of the Epidemic of Septic Sore Throat at Rock- 
ville Centre, Long Island. 
England, Germany, and Austria; after the American Civil 
War (1860-1864), typhoid fever spread to many of the 
northern cities; and after the Spanish-American War (1902), 
typhoid and smallpox were very common. These historical 
facts show that there has been great danger in the past from 
returning troops. 
The officials in the army and navy thoroughly under- 
stood the dangers and tried to take proper precautions 
against the spread of disease; but the task was very great. 430 
HEALTH 
Some of the epidemic diseases in Europe were of the types 
which, once well started, might produce great havoc. They 
included trench fever, typhus, relapsing fever, cholera, and 
plague. Most of these are transmitted by vermin, most 
commonly the louse. In general the conditions are not favor- 
able in the United States for the transmission of disease 
by lice, although in certain congested quarters they are 
common. 
The term epidemic as used in this paragraph refers to the 
widespread occurrence of a disease in which a large number 
of people in a community are affected at the same time. 
This is the usual sense in which it is used by physicians. 
All American troops were detained in Europe at foreign 
ports for two weeks, during which time they were deloused. 
After the troops had embarked, they were inspected a second 
time for lice. On landing in the United States, all the troops 
were sent to debarkation camps, where universal delousing 
was practiced. 
Many people think that Americans take so many pre- 
cautions and are so well trained in ordinary questions of 
personal and civil hygiene that epidemics are impossible. 
While many are familiar with the ordinary rules which science 
has deviled for their protection, it is necessary for all to 
observe them. Those of us who understand the real meaning 
of communicable disease must take upon ourselves the re- 
sponsibility of helping to explain the cause of all such disease 
to those who have not been so fortunate as to have had a 
course in biology. 
Prevention of Epidemics. - The first measure to be adopted, 
and the one of greatest importance, is educational. Under 
this heading is included the knowledge: (1) that all germ 
diseases are due to a specific germ, plant or animal, living 
in an intimate relation on or in the human body; (2) that 
all germ diseases are preventable; (3) that keeping our bodies 
clean, eating clean food, well cooked, and taking plenty of Robert Koch (1843-1910) attained great renown when in 1883 
he discovered the germ which causes tuberculosis. In 1883, he 
announced that he had found the germ of Asiatic cholera. For 
several years after he advanced the science of disease by making 
other discoveries. For some time before his death, he was the 
director of the Institute for Infectious Diseases in Berlin. 
In all of his investigations he applied strictly scientific methods 
some of which have become a part of the procedure every time 
a new germ disease is studied. Four steps must be taken before 
one can be certain that the cause of a germ disease has been 
discovered. These are : First, a microscopic organism of a par- 
ticular type must be found in abundance in the blood or tissues 
of the sick organism; second, a pure culture must be made of the 
suspected organism; third, this pure culture, when introduced into 
the body of another similar organism, must produce the same 
disease; and, fourth, there must then be found in the blood or 
tissues of the diseased organisms large numbers of these introduced 
germs. BOARDS OF HEALTH 
431 
exercise will do more to prevent germ diseases than any- 
thing else. 
The second important measure to be adopted to prevent 
an epidemic after the communicable disease has appeared is 
the prompt quarantine of the first cases and immediately 
putting into operation the regulations of the Board of Health 
for communicable diseases. 
304. Heredity of Disease. - The term heredity of disease 
is one which has been misunderstood by many people. By 
the term heredity we mean that which is handed on from 
parents to their offspring. In the case of biological diseases 
which are caused by some definite plant or animal, it is 
evident that they cannot be inherited. But when the 
parents are afflicted with a biological disease, their bodies 
become weakened and their offspring may have a poor con- 
stitution, so that they are more easily affected by disease. 
305. Boards of Health. - Communities and physicians 
have endeavored to prevent the spread of communicable 
diseases by the formation of boards of health, by quaran- 
tine, vaccination against smallpox, immunization against 
typhoid fever, the use of antitoxin in diphtheria, disinfectants 
and fumigants. 
The term Board of Health is applied to a number of in- 
dividuals, appointed or elected by a nation, by a state, or 
by a municipality, to enforce the national, state, city, or town 
health laws and regulations. The local officer of this board 
is a physician, and in some states, New York for example, 
is appointed according to the regulations governing the 
city or town in which he is to serve. The New York state 
law defines his work as follows: 
" Every such local officer should guard against the intro- 
duction of such communicable diseases as are designated 
by the State Department of Health by the exercise of proper 
and vigilant medical inspection and control of all persons 
and things infected with or exposed to such diseases, and 432 
HEALTH 
provide suitable places for the treatment and care of sick 
persons who cannot otherwise be provided for." 
306. Unsolved Problems in Disease. - In our description 
of diseases and their prevention a careful distinction was made 
between those whose cause was known and those whose cause 
was unknown. In this latter class are placed cancers, tumors, 
infantile paralysis, scarlet fever, and influenza. In some of 
these experts believe that they have discovered the cause but 
are not yet able to control it. The first thing to note about 
this list is that the number of diseases is very small in com- 
parison with those whose cause is understood. The second 
fact of great importance is that we cannot take effective 
steps to prevent these diseases until the causes are known. 
How is this to be accomplished ? 
Eventually these diseases will yield their secrets to man 
just as the others have through his studies on animals. We 
have become so familiar with the modern ideas of sanitation 
that the terror and hopelessness of our grandparents as they 
faced epidemics of smallpox, typhoid fever, yellow fever, 
malaria, and bubonic plague do not occur to us. These 
terrible maladies have been conquered, and we today do not 
know the pests that used to devastate the world at intervals. 
All of this triumph is due to successful experimentation with 
animals. Although there are a few people who object to 
scientific workers using animals for experimental purposes, 
the great majority agree that, in order to save thousands of 
human beings from premature death and great suffering, it 
is necessary to sacrifice a small number of animals. 
Ernest Harold Baynes writes on this phase of the subject 
as follows: "As president of a humane society and as one 
whose life is spent chiefly in studying animals and in working 
for their conservation, it is my business to know something 
about this. I have visited physiological laboratories and 
medical schools in most of the large cities and many of the 
smaller ones from Boston to San Francisco, and I can testify UNSOLVED PROBLEMS IN DISEASE 
433 
that I have never seen anything in the nature of cruelty in 
one of them. Since beginning my investigations I have 
become intimately acquainted with many of our foremost 
physiologists - vivisectors, if you like - and there are no 
men or women I should consider more humane, in the broad- 
est and best sense of the word. They treat the animals in 
their care with kindness and consideration and they reduce 
to a minimum such discomfort as it is sometimes necessary 
to inflict in experiments made for the sole purpose of pre- 
venting suffering and death. I have witnessed experiments 
on monkeys, horses, dogs, cats, sheep, goats, rabbits, guinea 
pigs, rats, mice, poultry, frogs, and fish. Whenever an 
operation is likely to cause more discomfort than would be 
experienced in taking an anesthetic, the animal receives an 
anesthetic and is kept completely under its influence. If the 
operation is a routine procedure, designed to perfect the 
skill of medical students, the animal is killed with extra 
ether at the close of the experiment. The only possible dis- 
comfort such an animal can experience is in taking the ether 
at the beginning." 
OUTLINE 
Importance of health 
Cost of illness 
Kinds of disease 
Inherited 
Poisonous 
Growths 
Biological 
Ailments 
Indigestion 
Communicable diseases 
Manner of infection 
Tuberculosis 
Germs 
In air 
In food 
Getting well 
Influenza 
Symptoms 
Preparation for pneumonia 
Malaria 
Source of parasite 
Anopheles mosquito 
Yellow fever 
Source 
Aedes mosquito 
Quarantine 
National 
State 
Local 
Worm diseases 
Tapeworm 
Trichina 
Hookworm 434 
HEALTH 
Immunity 
Vaccination 
Antitoxin 
Sanitation 
At home 
Disinfection 
Carbolic acid 
Chloride of lime 
Antiseptic lotions 
Emergency treatments 
Cuts 
Bruises 
Burns 
Fractures 
Poisons 
Neutralizing agents 
Keeping well 
Doctors 
Government inspections 
Avoiding "carriers" 
Saving children 
Hygiene 
Sanitation 
Parental ignorance 
Community improvements 
Epidemics 
Prevention 
Heredity of disease 
Boards of health 
Unsolved problems 
SUMMARY 
Disease prevents us from working as we do when we are well. Most 
diseases are unnecessary and preventable, especially those which are 
caused by plants or animals living as parasites in our bodies. In most of 
the biological diseases some definite poison produced by the parasite is 
taken into the body, and this is the chief cause of disease. Tuberculosis, 
the " great white plague," is caused by a plant named Bacillus tubercu- 
losis and often referred to by physicians as " Tb." One can get well if 
the body is able to overcome the poisons secreted by these minute plants. 
Each disease caused by bacteria has its own special history and the 
symptoms of the disease are definite and distinct. Influenza is probably 
a germ disease, but the exact kind of bacteria is still unknown. It was 
epidemic over nearly the whole world in 1918 and 1919. Malaria is a 
disease due to a protozoan parasite living in the blood corpuscles of 
man. These parasites are introduced into the blood through the bite 
of Anopheles mosquitoes. 
As a physician knows the nature of a disease and its effect upon the 
body, he can aid materially in overcoming the illness. Each biological 
disease is distinct and must have special treatment. Many of these 
diseases are taken from some one who has the disease. Vaccination, 
antitoxin, quarantine, and disinfection are measures which help to 
prevent the spread of germ diseases. It is our duty to keep well, and 
we can do much toward this by understanding how to avoid the biologi- 
cal diseases. REFERENCES 
435 
QUESTIONS 
What are the biological diseases? How are these diseases caused? 
How many kinds of tuberculosis are there? Is diphtheria a germ 
disease? Are colds germ diseases? Describe malaria. What effect 
has malaria had upon the settlement of our country? This is a home 
study question. What is vaccination? What is quarantine? For 
what diseases are people quarantined? What is the work of the Board 
of Health? What is the purpose of disinfection? What are the chief 
disinfectants? What is the danger from epidemics? Name some 
epidemics. How can they be prevented? What are some of the 
values of public parks and public baths ? What are the powers of health 
officers ? What is your state doing to prevent disease ? 
REFERENCES 
1. Celli-Eyre, Malaria 
2. Chalmers, The Beloved Physician Edward L. Trudeau. 
3. Chapin, Sources and Modes of Infection. 
4. Conn, Bacteria in Milk. 
5. Cornell, Health and Medical Inspection of School Children. 
6. Edelman, Mehler, and Eichorn, Meat Inspection. 
7. Knoff, Tuberculosis, A Preventable and Curable Disease. 
8. Rosenau, Disinfection and Disinfectants. 
9. Stiles, Prevalence and Geographical Distribution of Hookworm 
Disease. Hygienic Laboratory, Bulletin Number 10, Washington. 
10. Trudeau, Edward L., An Autobiography. PART IV 
APPLICATION OF BIOLOGIC PRINCIPLES TO PLANTS 
CHAPTER XXVI 
STUDY OF A LIVING GREEN PLANT 
Come forth into the light of things. Let Nature be your teacher. 
- Wordsworth 
307. Introduction. - In Part II we have studied some 
of the most important facts about how animals live and their 
relations to one another. In Part III we have studied how 
man lives and how he resembles the other animals in his 
dependence on conditions around him and in having relation- 
ships with other living things. In Part IV we shall study not 
only how plants live but also how necessary they are to the 
existence of all forms of animal life. 
We have every reason to believe that plants were here ages 
before man appeared and that animals were using them for 
food. For a long time man's greatest interest in plants was 
their use as food. In fact the very word botany comes from 
the Greek botany, fodder. Savage peoples used the plants 
they found growing wild around them. In the course of 
time certain plants were cultivated and improved for food. 
Another interest which primitive man had in plants was 
their use as medicine. Curiously enough this interest led 
finally to the first attempts to describe plants accurately. 
The physicians in one part of the world wanted to be sure 
that they were talking or reading about the same kind of 
436 GENERAL STRUCTURE OF PLANTS 
437 
plant as some other physician in some other part of the world. 
So a careful study was made of plants used for medicine by 
the physicians who were also botanists. One of these men 
invented the system of naming plants (and other organisms) 
which is still in use. 
Naming and describing plants, collecting and pressing 
them, became a fascinating study. The more they were 
studied the more likenesses were found between them and 
animals - for example, that they need the same conditions 
to live, that they perform the same vital processes, that they 
have organs for these processes. The discovery that green 
plants give out oxygen and use carbonic acid gas was an 
important one. It emphasized the fact that plants help 
animals by keeping the air pure. It had long been known 
that certain animal wastes in the soil helped plants to grow. 
The latest great discovery about plants is that they are 
the only food-makers in the world, - the only means known 
by which energy from the sun can be gathered, locked up, 
and stored. Plants make food for themselves and their 
offspring, and also for animals which eat the plants them- 
selves in some cases and the stored food in others. 
This food supplies the energy necessary to plants. They 
need it for movements, such as climbing, and to overcome ob- 
stacles, as when a seedling has to push up through the earth 
or pierce a layer of leaves to get to the light. It takes energy, 
too, to make and transport food and to divide cells. 
The study of plants at the present time is chiefly biological. 
We wish to learn how a plant lives as an organism among 
other organisms and how its organs, roots, stems, leaves, 
etc., carry on its vital processes. (Review Introduction 
and Chapter IV.) 
Our study will consist largely in observing the adaptations 
which plants have for living under varied conditions. 
308. General Structure of Plants. - Plants, like animals, 
are made up of organs, - the roots, the stem, the leaves, the 438 
STUDY OF A LIVING GREEN PLANT 
flowers, and usually the fruit. The organs are made up of 
tissues, and the tissues of cells. Cells vary greatly in size 
and shape even in the same tissue and even more so in differ- 
ent plants. Separate cells of a unicellular alga, Pleurococcus, 
are nearly spherical, and so small as to be invisible without 
the aid of a microscope. Others, like root hairs, are large 
enough to be seen by the naked 
eye and very long and slender in 
shape. 
309. Parts of the Cell. - 
Whatever their size, shape, or 
function, all cells have certain 
main parts. These are, first, the 
wall. The wall in a plant cell is 
usually thicker and firmer than 
the wall in animal cells, owing to 
the presence in plants of a sub- 
stance resembling wood and known as cellulose. The wall 
in every cell incloses a mass of cytoplasm, the second main 
part of a cell. In the cytoplasm is imbedded the nucleus, 
the third main part of a cell. The nucleus is darker than 
the surrounding cytoplasm, being composed of a slightly 
different substance. Besides the wall, the cytoplasm, and 
the nucleus, a plant cell usually contains spaces filled with 
cell sap, and if the cell is green, it contains small green 
particles called chlorophyll bodies or chloroplasts. In the 
plant, as in the animal, the cell is the unit of both structure 
and function of all living parts. 
310. Protoplasm. - The entire cell is composed of proto- 
plasm. This has one form in the wall, another in the cyto- 
plasm, and still another in the nucleus. Protoplasm is a 
living substance which has definite characteristics. It is 
semi-liquid, like the white of an egg. It is transparent or 
translucent like cooked starch or ground glass. It is mostly 
water. It absorbs, digests, and assimilates food. It re- 
Figure 268. - Pleurococcus. 
a, single plant; b, plant divid- 
ing ; c, d, groups of plants. CELL GROWTH AND DIVISION 
439 
spires and excretes. It repairs its own wastes. It grows. 
It reproduces. It is irritable to stimuli, - warmth, light, 
contact, chemicals, electricity. 
Cytoplasm is that particular kind of protoplasm which 
fills the cell wall. The vital processes are carried on by it 
for the most part. The nucleus is still another particular 
kind which governs and controls the processes of the cyto- 
plasm. 
Protoplasm is made up chiefly of four substances, carbon, 
oxygen, hydrogen, and nitrogen, with small quantities of 
Figure 269. - Cells in Different Stages of Division. 
M, nuclear matter ready to divide; A, nuclear matter dividing; P, nucleus 
divided, and new cells formed. Note other new cells (small). 
iron, sodium, phosphorus, potassium, magnesium, calcium, 
and other chemicals (see page 26). The amounts of these 
different substances vary from second to second, making it 
very difficult to describe the chemical composition accu- 
rately. However, hydrogen and oxygen in the form of water 
make up the largest part, as has already been said. 440 
STUDY OF A LIVING GREEN PLANT 
311. Cell Growth and Division. - Cells grow, yet they 
do not grow on indefinitely, for there is a limit to the size 
which any kind of cell attains. When this limit has been 
reached, the cell divides into two smaller ones each of which 
then grows to full size and divides again. The size of an 
organism depends largely upon the number of cells it con- 
tains. An elephant is larger than a mouse or a horse because 
it contains more cells than either, just as a business block 
is larger than a garage or 
a house because it has 
more bricks in it. A 
plant grows, therefore, 
by adding to cells already 
there. 
Cells divide by forming 
a new wall through the 
middle or by a process 
of pinching in two, called 
fission, or by a more com- 
plicated process, which 
is shown in Figure 269. 
The method of division 
depends on the kind of 
cell and the function it 
performs. 
Photographed by Paul J. Sedgwick. 
Figure 270. - Photomicrograph of 
the Cells Shown in Figure 269. 
Structure. - Examine a bit of the thin skin between the layers of an 
onion, using a prepared slide if possible. Study first under low, then 
under high, power of a compound microscope. Note that it is com- 
posed of cells. Are they all the same size? The same shape? Draw 
a small group as they appear under high power. Label (1) the wall, 
the inclosing portion, (2) cytoplasm, the substance within the wall, 
(3) nucleus, a dark portion imbedded in the cytoplasm. Is there a 
vacuole (this appears as an empty space) ? What is the greatest number 
of cells that touch any one cell? 
LABORATORY STUDY OF CELLS LIFE NEEDS AND FUNCTIONS 
441 
Compare the drawing you have made with other parts of plants 
(Figures 268-269), and with organs of animals. (See Figure 281.) 
Try to find out how many times the microscope has magnified the cells 
you drew. Try to compute the number of cells there must be in a 
square millimeter of onion skin; in a square inch. 
The cytoplasm of a cell of Spirogyra can be condensed and drawn 
from the walls by soaking it for a few seconds in salt water or in sugar 
and water. This also shows the wall clearly as separate from the cyto- 
plasm. A hair from a squash seedling shows vacuoles well. Use the 
high power of a compound microscope. 
Protoplasmic Activity. - Place the tip of a leaf of elodea, nitella, or 
chara, or a hair from a squash seedling on a slide, in water. Support 
a cover glass with bits of pith or glass so that the cells will be free from 
pressure. Place under high power of a microscope. Gently warm the 
slide by laying on it one that is slightly warmer. Examine cells for 
circulatory movement of protoplasm, especially near the walls of the 
cells. Note the direction of the motion. 
312. Comparison of the Life Needs and Life Functions of 
Plants and Animals. - It is a matter of common knowledge 
that an animal deprived of food and water will die in a short 
time, and that it will smother if it has no air, and freeze to 
death if exposed to too great a degree of cold. In other 
words, an animal cannot live without food, water, air, and a 
moderate degree of warmth. This being so, we speak of them 
as the life needs of animals. Plants have exactly the same 
life needs, for they, too, are organisms, composed of cells 
made of protoplasm. 
An animal, to live and thrive, needs to secure food, then 
to digest it, to circulate the digested food, assimilate parts 
of it, cast off wastes formed, and respire. These processes 
of animals are their life functions, all of them necessary for 
the carrying on of their individual lives. In addition they 
must reproduce in order that the race may not die out. 
Plants have exactly the same life functions and in addition, 
green plants have a life function which no other organisms 
have; namely, photosynthesis (see page 37). This is the pro- 
cess of making carbohydrates, one of the classes of foods (see 442 
STUDY OF A LIVING GREEN PLANT 
page 27), from raw materials, taken from the soil and from 
the air, under the influence of sunlight. Green plants are, 
then, the only means in the world of keeping up the supply 
of food, a fact which makes them, fundamentally, the most 
important organisms in the world, since all life, even their 
own, depends on their being able to furnish the food needed 
for existence. The more we think about this fact, the more 
wonderful it seems; and the more we study about the re- 
lations of green plants to other organisms, the more deeply 
we appreciate what a delicately adjusted and marvelous place 
the earth is. 
In many ways, flowering plants are more intricate organ- 
isms than animals. Without the ability to change their 
environment, they must depend upon the soil as they find 
it, rich or poor, wet or dry, soft or hard, to furnish them 
water and such food materials as come to them in liquid form. 
Without being able to seek shelter, they must take sun or 
shade, heat or cold, rainy weather or dry, pure or impure 
air just as each comes. Lacking organs of offense or defense 
against other plants they must contend with them for mois- 
ture, air, and light, besides being subject to the attacks of 
organisms which injure them. In addition to making of 
themselves the best plants possible under the conditions, 
they must produce numerous offspring, furnish each new 
plant with a supply of food, and send them all out into the 
world to meet and to make use of such conditions as they 
may find. 
An examination of the plants in any garden or yard will 
show that varying degrees of success have been attained. In 
every case, however, it represents the best that could be 
done under the circumstances. When we consider that 
plants have not intelligence such as animals possess, it ap- 
pears all the more remarkable that they can accomplish so 
much, often under very adverse conditions. The biologist's 
great interest in plants is in the ways they adapt themselves QUESTIONS 
443 
to carry on their life processes under all sorts of conditions, 
as well as in the processes themselves. Those who raise 
plants can expect success only as they are able to supply the 
conditions under which each plant thrives best, and to con- 
trol conditions and organisms which may be unfavorable. 
SUMMARY 
The green plant is an organism which consists of root, stem, leaves, 
flowers, and later, fruits. Plants are composed of cells, the main parts 
of which are wall, cytoplasm, and nucleus. Plant cells have firmer walls 
than animal cells, due to the presence of cellulose. Protoplasm is the 
living substance of which the cells are composed and by which the life 
processes are carried on. A cell is a bit of organized protoplasm, the 
unit of structure and function of all living parts of the plant. 
Plants, like animals, require food, air, water, and warmth. Like 
animals, they digest, circulate, and assimilate food, cast off waste, 
respire, and reproduce. In addition, green plants have a life function, 
photosynthesis, which is peculiar to them. Photosynthesis is the 
process of combining into foods, under the influence of sunlight, raw 
materials from the air and the water obtained from the soil. Since this 
is the only way that food is made in nature, it follows that everything 
that requires food is dependent upon plants to make it. 
QUESTIONS 
How are plants and animals alike in their needs? In their struc- 
ture? What is photosynthesis? What organisms perform it? Why 
is it so important a function ? CHAPTER XXVII 
LEAVES -THE PLANT'S WORK-SHOP 
I sing the first green leaf upon the bough, 
The tiny kindling flame of emerald fire. 
The stir amid the roots of reeds, and how 
The sap will flush the briar. 
- Clinton Scollard 
313. General Structure and Parts of a Leaf. - The leaf 
is the most important organ of the plant, for in it are carried 
on most of those processes 
which pertain to the life of the 
plant itself. Because it is so 
stipules 
Figure 271. - Leaf of 
Oak. 
The blade, though deeply 
lobed, is simple, i.e., un- 
divided. 
Figure 272. - Leaf of a Straw- 
berry, Showing Stipules. 
important an organ and because it has so many kinds of 
work to do, it has many adaptations in form, position, and 
444 THE ARRANGEMENT OF LEAVES 
445 
structure which fit it to do its various kinds of work, besides 
giving individuality to plants. We shall study the work of 
the leaves first in order that we may more easily under- 
stand how the structure, form, and position of the various 
kinds of leaves adapt each to its work. 
The main part of a leaf is the blade. The petiole (Latin, 
petiolus, fruit stalk) is the part by which it is attached to the 
twig. This sometimes has small pro- 
jections called stipules at the base. 
314. Venation. - The leaf of most 
plants contains ribs or veins which de- 
termine its main form and serve to keep 
it firm. There are two main types of 
arrangement of veins. The first, that 
in which there are a few veins of about 
the same size which run side by side 
without branching from the base of the 
leaf to the tip. These are the parallel- 
veined leaves found in grasses, lilies, and 
most other monocotyledonous plants. 
In the second type, the netted-veined 
leaves, a few main veins branch and 
divide, filling the spaces between them 
with a fine network of small veins. The 
main veins may have a palmate arrange- 
ment, as in the palmately-netted-veined 
maple leaf, or they may branch from 
a central vein, as in the pinnately-netted- 
veined leaf of the elm. In such a leaf, each branch of the 
mid-vein usually ends in a point of the margin, or in a notch. 
315. The Arrangement of Leaves. - In general, leaf ar- 
rangement falls into two groups: (1) small leaves arranged 
all along the length of a branch - the spiral arrangement, 
the simplest form of which is found in the elm, where the 
leaves are in two rows alternating with each other; (2) a few 
Figure 273. - Leaf of 
Elm. 
Simple leaf with a 
serrate margin and pin- 
nately-netted venation. 
Note that the leaf is 
asymmetrical at the 
base. The general 
shape is ovate oblong, 
with a sharp apex. 446 
LEAVES - THE PLANT'S WORK-SHOP 
large leaves at the end of a branch, as in the maple, where 
the leaves are in pairs, each pair alternating with its neigh- 
bors. In the first case the shape of the leaves is such that 
all the space is occupied without much overlapping; in the 
second, every leaf is fully exposed to the light by the lowest 
Figure 274. 
Showing the arrangement by which leaves receive as much light as possible. 
leaves having the longest petioles. The leaves of a maple 
illustrate this. 
A rosette is formed by leaves, arranged spirally on a very 
short stem, with long petioles nearest to the ground, shorter 
ones alternating with them and filling the spaces. The THE ARRANGEMENT OF LEAVES 
447 
dandelion, evening primrose, and thistle show rosettes. 
Light that has passed through one leaf is of little value to a 
leaf below it. Some plants have finely divided leaves, an 
adaptation which prevents any leaf shutting off all the light 
from those below. Angular leaves, round leaves, and leaf- 
lets are all adaptations to use up all the space without over- 
lapping. The leaves of ivy growing on a wall are so arranged 
Figure 275. - Leaves of Young Plants of Pokeweed. 
Note their large size, and their arrangement to prevent shutting off the 
light from those below. 
as to fill all the spaces and not to overlap. They form what 
is called a leaf mosaic. 
Whatever the arrangement of leaves on any particular 
plant, the object is to expose the leaves most advantageously 
to light and air, incidentally preventing their shading one 
another, which sometimes causes a vertical branch and a 
horizontal branch of the same plant to show a different 
arrangement of leaves. 448 
LEAVES- THE PLANT'S WORK-SHOP 
316. Simple and Compound Leaves. - A leaf is said to 
be simple when the blade is all in one part, and compound 
when it is divided into three or more leaflets. The apple 
and the maple have simple leaves, the clover and the horse- 
chestnut have compound leaves. A compound leaf is one 
in which the leaflets branch from the midrib, as in the rose 
or the locust; there are three leaflets, as in the clover 
and oxalis, or one in which there are five or more leaflets, 
as in the horse-chestnut and woodbine. 
Figure 276. - Palmately Compound Leaf of Woodbine. 
There is a reason for these compound leaves. A leaf with 
a blade as large as the combined surfaces of a compound 
leaf would be much more easily torn by the wind, and would 
cut off more light from the leaves below. Some leaves are 
very finely divided, being many times compound, like the 
carrot and the yarrow. 
317. Dropping of Leaves in Autumn. - Before a tree sheds 
its leaves, it withdraws all the food they contain and stores 
it in some other portion of the tree. What remains is largely MODIFIED FORMS OF LEAVES 
449 
the mineral matter that was not needed in the manufacture 
of food. This is waste, and so of no further use to the tree. 
The shedding of leaves thus serves two purposes - to re- 
duce transpiration 1 and to get rid of waste. 
Autumn colors appear to be due to a combination of causes, 
among them the removal of chlorophyll which has covered 
up other colors, and chemical 
changes which take place 
in the leaf after its work is 
done. 
318. Modified Forms of 
Leaves. - Some leaves, like 
the sundew, pitcher plant, 
and Venus's flytrap, are 
adapted for catching insects 
for the use of the plant as 
The petiole is attached at the middle 
of the back of the blade. The blade 
is orbicular, with entire margin. Note 
the twining petiole, a device for holding 
up a weak stem. 
Figure 278. - Leaf of Nasturtium. 
nitrogenous food. In others, 
as clematis, the petioles are used 
to help the plant in climbing. 
In the case of the pea, leaves 
have become modified into 
tendrils which are used in 
helping the plant to climb. 
(See Figure 277.) The tendrils of grape-vines and various 
kinds of ivy are also modified leaves. Still others have their 
leaves modified to thorns for protection, as in the thorny 
locust and barberry. 
Figure 277. - Twining Petiole 
of Clematis. 
1 The act of sending off watery vapor. 450 
LEAVES - THE PLANT'S WORK-SHOP 
319. Leafless Plants. - In plants like the cactus, already 
mentioned, the work usually done by leaves is performed 
by the stem. Asparagus is a plant in which a much-branched 
stem serves as leaves, the true leaves being almost invisible 
scales. Another example is the plant commonly called 
smilax, in which the branches very closely resemble leaves. 
Other plants which have scales instead of leaves are dodder 
and Indian pipe, both of which use food already prepared. 
These leaves, all taken from the same bush, show the transition from 
normal leaves to thorns for protection. 
Figure 279. - Leaves of Barberry. 
320. The Movement of Leaves. - Most movements of 
leaves are due to unequal growth caused by the light being 
brighter on one side than on the other. Some leaves on this 
account " follow the sun." Others, like the compass plant, 
turn their edges to direct sunlight which is too strong for 
them. The clover and oxalis, which fold their leaflets at 
night, illustrate the so-called " sleep movements " of plants. THE MOVEMENT OE LEAVES 
451 
The movements of sensi- 
tive plants are due to 
the effect of the shock 
caused by touching them. 
This causes the cells of 
an organ at the base of 
the petiole to become 
soft and flaccid through 
loss of water which passes 
into the inter-cellular 
spaces, allowing the 
whole leaf to droop and 
the leaflet to fold. 
HOME WORK, MOVE- 
MENTS OF PLANTS 
Place young seedlings in a 
window for a day. Which 
way do they turn? Turn 
the plants around and note 
how long it takes them to be- 
come erect; to become bent 
towards the window again. 
Keep careful records, using 
camera or drawings. 
On a sunny day set a stick 
parallel with the tip of a rag- 
weed or other tall, slender 
weed. Set another stick 
about noon and another 
about three o'clock. Draw a 
diagram, or use your camera 
to show the changes in the 
position of the tip of the plant. Observe leaves of clover, and young 
daisy blossoms. Do they change their positions with the sun? What 
other plants do this? Does the age of the plant make any difference 
with its ability to change position ? 
Bend a grass stem and fasten it flat. After a day or two observe its 
position. What changes have taken place? 
Figure 280.- Indian Pipe. 
This is white. It uses food already pre- 
pared, as it lacks chlorophyll. 452 
LEAVES - THE PLANT'S WORK-SHOP 
Write notes telling what you have been able to observe in the cases 
above, and in any others which you may have noticed without being 
directed to do so. 
321. Structure of a Leaf (Cross Section). - While leaves 
vary greatly in number, size, position, and shape, the work 
that they do is very similar for each plant. A typical leaf 
is covered with a layer of thin cells called the epidermis. In 
"-cutin 
I-epidermis 
-palisade 
cells 
chlorophyll 
spongy 
x layer 
-vein 
end oF 
vein 
I.S. 
y-lower 
' epidermis 
Figure 281. -Diagram of Structure of a Leaf. 
hot, dry regions the epidermis has a heavy coating of cutin, 
a substance which prevents evaporation. The epidermis 
on the under side of the leaf is thinner and has less cutin 
than that on the upper side of the leaf. It is pierced by many 
openings called stomata or air pores (Greek, stoma, a mouth) 
which allows the entrance of air and the exit of water and 
gas. Between these two layers of epidermis is the mesophyll 
(mez'o-fil: Greek, mesos, middle; phyllos, leaf) of the leaf, STRUCTURE OF A LEAF (CROSS SECTION) 
453 
divided into two regions, (1) the upper or palisade composed 
of slender, elongated cells placed side by side in upright 
position, (2) spongy layer consisting of rounded cells, loosely 
arranged with many air spaces between them. It is in this 
spongy layer that the most chlorophyll is found. 
LABORATORY STUDY OF LEAVES 
Draw a leaf of geranium (or other plant). Label (1) blade, (2) peti- 
ole, (3) stipules, if any. Notice the arrangement of the veins as you 
look through it. 
Remove the leaves from an onion. Note the thickened bases and 
how they are attached to the short stem. 
Stand a stalk of celery in water tinted with red ink. Cut across 
it after two hours and observe the position of the vascular bundles.1 
Trace them into the leaf. 
Pull off leaves of dock and plantain and observe the tough vascular 
bundles. 
Study a bit of epidermis with a microscope. Draw. Label stomata, 
epidermal cells, guard cells (2 around each stoma). Study a cross sec- 
tion. Label cuticle, outermost layer, epidermis (upper and under sur- 
faces), palisade layer under top epidermis; spongy layer, body of leaf; 
vein Which cells contain chlorophyll? Where are the air spaces? 
HOME WORK ON LEAVES 
Pull up or cut off a large burdock plant. Measure the area covered 
by the lower leaves. What else grew in this area? What is its condi- 
tion? Why? Do the same with plantain, dock, dandelion, knotweed, 
and other weeds in dooryard or garden. What plants form rosettes 
of leaves in the fall? 
Break off leaves of burdock, plantain, dock, and pieplant. Note 
the strings (fibrovascular bundles)} 
Make a collection of leaves to illustrate the various kinds of shape, 
apex, margin, and base. 
Study the arrangement of leaves on the plants you see to determine 
how it is adapted to secure light for all the leaves. 
What effect does the wind have in helping or hindering leaves to 
get light? 
What happens when you make a "bag" from a leaf of live-for-ever? 
1 Elongated cells or vessels for the circulation of sap. 454 
LEAVES- THE PLANT'S WORK-SHOP 
322. Adaptations of a Leaf. - The cutm of the epidermis 
prevents evaporation of water. The stomata allow air to 
enter and water and gases to pass out. Stomata themselves 
show many adaptations: (1) Position. In a leaf that ex- 
tends horizontally from a plant, most of the stomata are on 
the under side, an adaptation which prevents their being 
closed by water. In leaves which float upon the water, the 
stomata are on the upper 
surface for the same 
reason. In plants with 
erect leaves, the stomata 
are distributed on both 
sides. In the cases of 
desert plants, the stomata 
are sunk below the level 
of the epidermis, or they 
are covered by hairs or 
wax, both of which tend 
to keep them from being 
filled with water and to 
prevent undue tran- 
spiration (evaporation). 
(2) The structure. This 
shows other adaptations. 
The opening is sur- 
rounded by two cells, 
called guard cells, which have the property of absorbing water 
from the atmosphere. When these cells are full of moisture, 
they are plump or turgid; when they have only a little water 
they are flabby or flaccid. The turgid guard cells leave the 
stomata wide open and allow free passage of air into the cell, 
and of water and gas out of it. Flaccid guard cells, on the 
other hand, make the opening small, decrease the amount 
of air that enters, and prevent undue evaporation from the 
inside of the leaf. Although each stoma is very small, they 
Figure 282. - Bit of Epidermis of Leaf. 
The epidermal cells lack chlorophyll. 
The guard cells of the stomata have it. PHOTOSYNTHESIS 
455 
are so numerous that their combined action accomplishes a 
great deal. A square millimeter of the under surface of a 
lilac leaf contains 330 stomata, that of white birch, 237. 
Most of the grasses show adaptations (1) in having very 
narrow leaves, fitted to grow close together; (2) in wavy 
edges if they are long, an adaptation which prevents their 
being torn by the wind; (3) in a clasping base, helping to 
strengthen the stem, and (4) in a collar which prevents water 
from running down between the clasping base and the stem. 
323. Functions of Leaves. - The life processes carried on 
by the leaf are (1) photosynthesis, peculiar to plants having 
chlorophyll, green coloring matter; (2) respiration, common 
to all living protoplasm; (3) digestion, (4) circulation, (5) as- 
similation, and (6) excretion. All but the first are much the 
same as the processes of the same names in animals. Tran- 
spiration which, like photosynthesis, is peculiar to green plants, 
while not one of the life processes, is made necessary by them. 
The work that a leaf does is of greater importance than 
anything else about it. We study its structure in order to 
understand how it is able to carry on this work. For the 
same reason we study the arrangement of the leaves on the 
stem, and their form, which has a close relation to arrange- 
ment. 
324. Photosynthesis. Carbohydrate Manufacture. - The 
word photosynthesis (Greek, phos, light; synthesis, composi- 
tion) means putting together by means of light. It is the 
process of manufacturing carbohydrates from raw materials, 
a vital process performed only by green plants. 
The Process. - Many facts about this process are not well 
understood, but we can state a few with certainty: (1) that 
in the manufacture of carbohydrates by photosynthesis, 
carbon dioxide is used as one of the raw materials, the source 
of this gas being the air, in which it exists 3 or 4 parts in 
10,000, and the waste of the plant's own respiration ; (2) that 
another raw material used* is water, which is taken up by 456 
LEAVES -THE PLANT'S WORK-SHOP 
roots; (3) that some oxygen is left over as a by-product and 
given off as a waste of the process of photosynthesis ; (4) that 
chlorophyll, the green coloring matter of plants, is essential; 
(5) that light is necessary not only to develop the chlorophyll 
but also to enable it to manufacture carbohydrates ; (6) that 
another necessary factor is a moderate degree of warmth. 
The Products. - Carbohydrates are the first visible prod- 
uct of photosynthesis, but proteins and oils result from 
later processes, probably very similar to photosynthesis, 
which take place in the green leaf. 
The Use Made of the Products. - The carbohydrates, 
proteins, and oils thus made are used in three ways : (1) some 
of it is digested in leaves and built up into new protoplasm; 
(2) some of it is stored in the leaves to be used later; (3) an- 
other portion is stored in other parts of the plant, as in the 
potato, in seeds, buds, and roots. 
Comparison. - The process of photosynthesis may be 
compared to any other manufacturing process which requires : 
1. A factory - in this case, green leaves. 
2. Machinery - the plant cells containing chlorophyll. 
3. Power - light from the sun, a form of energy. 
4. Raw materials - carbon dioxide and water, and small 
portions of nitrogen and other chemical substances which 
are dissolved in the water taken in by the roots. 
5. Working hours - daylight. 
In this comparison the products are the carbohydrates and 
other forms of food which are made from them, and the 
by-product, oxygen. This manufacturing process disposes 
of its products (1) by storing them on the premises, the leaf; 
(2) by using them on the premises, digesting them to make 
more protoplasm; (3) by sending them away to other parts 
for storage, or immediate use; (4) by using them to make 
other food substances, namely, proteins, and fats or oils. 
The Importance of Photosynthesis. - The importance of 
photosynthesis cannot be overestimated. It is the only TRAN SPIRA TION 
457 
natural process in the world by which raw material can be 
changed into food and by which energy can be stored up 
for future use. The plant makes use of this stored-up energy 
to produce new leaves, flowers, etc. Animals, which have 
not the ability to manufacture food from raw materials, 
depend directly or indirectly upon green plants for their 
supply of food. Besides making all the vegetable food in 
the world, plants, in using the carbon dioxide produced by 
animals, keep the air free from excess of it and so make it 
safe for animals to breathe. They also, by the same pro- 
cess, keep it well supplied with oxygen. Photosynthesis is 
the most important work of the leaf, as well as the vital 
process on which all other vital processes, both in plants and 
animals, depend. 
325. Transpiration. - This is the process of evaporation 
which takes place in plants, water in the form of vapor escap- 
ing through very small openings in the leaves called stomata. 
It is not one of the vital processes, but closely connected 
with them. Its only similarity to perspiration in animals, 
to which it has sometimes been likened, is that water is 
given off through openings in the outer covering of the plant. 
Transpiration is unavoidable because the roots of a plant 
usually take up more water than is needed for the vital 
processes, and because this excess accumulates in spaces 
which communicate with the outside through the stomata. 
The use of the stomata is to allow air containing carbon 
dioxide to pass into the leaf, and excess oxygen to pass out. 
Incidentally, however, water passes out too. When transpi- 
ration is too rapid, the plant is deprived of needed water. 
Since transpiration is a menace to the well-being of a plant, 
numerous devices have been developed for regulating it. 
1. The surface of a leaf is covered above and below by a 
layer of cutin, a transparent substance impervious to water, 
perforated only where stomata occur. 
2. The stomata are on the under side of the leaves in 458 
LEAVES -THE PLANT'S WORK-SHOP 
most plants, this position being less favorable to transpiration 
than the upper side. 
3. The stomata contain guard cells which regulate the 
size of the opening by absorbing moisture or losing it. When 
the guard cells are full of water, they are plump or turgid, 
leaving the stoma wide open. When they are soft or flaccid 
from lack of water, they collapse, partially closing the stoma. 
4. In addition to this regulating device the stomata may 
be under coverings of hair or wax to make evaporation less 
rapid, or they may be at the bottom of a very thick layer of 
cutin. 
5. A leaf may still further check transpiration by changing 
its position or by rolling its edges together. Corn leaves 
during a very dry period illustrate this. 
6. Another device is seen in cactus plants, which have a 
greatly reduced surface. The stem in these plants is green and 
it contains stomata, thus enabling it to do the work of leaves. 
When the moisture in the air exceeds a certain quantity, 
evaporation does not take place readily, causing too much 
water to accumulate in the plant. To prevent damage 
from this condition, plants have modified stomata, called 
water pores, at the ends of the veins. These contain cells 
which burst under pressure, allowing the water to exude. 
This process is known as guttation, and the drops so formed, 
as guttation drops. These are often seen in the morning 
on the ends of grass blades, and on the points of leaves that 
have serrate margins, like the strawberry. Guttation drops 
are sometimes absorbed by the plant and sometimes they 
evaporate, depending on the needs of the plant and the 
amount of moisture in the air, or, as we say, the degree of 
humidity. 
The amount of water that leaves a plant in a day by 
transpiration alone is very great. For example, a moderate- 
sized sunflower plant will give off a quart a day under ordi- 
nary conditions. CIRCULATION 
459 
PROJECT 
1. By observation, try to find out the conditions of weather 
which produce guttation in plants. 
2. Find out all you can about dew and the conditions 
under which it is produced. 
326. Excretion. - Excretion in plants is the same as in ani- 
mals in this respect, that it is getting rid of material or sub- 
stances which are no longer of use to the plant. It very often 
happens, however, that these are not removed from the plant 
as in the case of animals, but are simply stored where they 
can do no harm. An example of this is the crystals of cal- 
cium oxalate -which give to sorrel, or sour grass, its sour 
taste. The line between excretion and the secretion of 
certain substances, such as the oils in peppermint plants, is 
not easily drawn. In the case of the secretions, however, 
they often serve the purpose of preventing animals from 
eating the plants. 
327. Digestion of Food. - Although the plant manufac- 
tures food from raw materials, it cannot make use of it until 
it has been digested. The process of digestion takes place 
chiefly in the leaf, and the digested food is carried to all 
parts of the plant which need it through the vascular bundles. 
There are many facts about digestion in plants which are 
not so well understood as this same process in animals. It 
is known, however, that the enzyme, diastase, which digests 
starch, is secreted by the protoplasm of the cells and that 
it is very similar to ptyalin, the ferment in the saliva of 
animals which digests starch. 
328. Circulation. - Circulation in plants differs from cir- 
culation in animals in not having any central organ for keep- 
ing the fluids in motion and in the substances which the 
vessels contain. The xylem of a fibro-vascular bundle carries 
water taken up by the roots from the soil to the leaves, 
where it is combined with carbon from the air and built up 460 
LEAVES - THE PLANT'S WORK-SHOP 
into foods. The digested foods are carried from the leaf 
to the parts of the plant which need them in the phloem part 
of the vascular bundle, so that, generally speaking, we have 
an ascending stream of water in one part of the bundle and 
a descending stream of digested food in the other part. 
The term sap is used to include both. Sap is moved by the 
combined influence of 
osmosis (root pressure), 
transpiration, and possi- 
bly other factors. 
329. Respiration.- 
An important life func- 
tion of the leaf is respi- 
ration. Respiration in 
plants is exactly the 
same as respiration in 
animals. That is, every 
living cell requires oxy- 
gen, combining it with 
some of its protoplasm, 
releasing energy for the 
work of the plant and 
forming carbon dioxide 
and other wastes in the 
process. Respiration is 
most easily studied in 
plants like toadstools, 
which cannot perform photosynthesis, and in sprouting 
seedlings, which have not developed chlorophyll. 
330. Assimilation. - This is the actual taking up by the 
plant cells of such parts of the digested food as they need. 
By assimilation the old cells are repaired and new ones 
formed. It is a building-up process which results in the 
growth of the plant till it reaches the stage of maturity and 
in maintaining it at that size. 
Figure 283. - Skeleton of Poplar Leaf 
Note the epidermis still remaining on 
part of the leaf. Poplar leaves skeletonize 
very easily. This was picked up on the 
street. PROTEIN AND FAT FORMATION 
461 
HOME WORK ON PHOTOSYNTHESIS 
Make a list of the plants that are used for food. Look up in an 
encyclopedia the amounts of each produced in a given year. Make 
a list of the industries which are dependent on agriculture. Obtain 
information concerning the number of men employed in each. 
What uses arc made of starch and sugar aside from food ? 
What are the sources of the protein used for food? Which of these 
depend directly upon photosynthesis? Which indirectly upon it? 
LABORATORY STUDY 
Necessity for Light. - To show that light is necessary for photo- 
synthesis, fasten thin discs of cork to the upper and under sides of a 
leaf with clips, completely shutting off the light. Stand the plant in 
the bright light for half a day, then remove the corks from the leaf and 
the leaf from the plant. Heat enough 60 per cent alcohol to cover the 
leaf in a shallow glass dish. This may be done by setting the dish into 
hot water. Keep hot for half an hour, or till the chlorophyll is removed 
from the leaf. Turn off the alcohol and put drops of weak iodine on 
the leaf. Note that the circle covered by the cork discs shows little 
starch or none, as indicated by the faint blue color or by lack of color. 
Make a similar test by comparing a leaf from a plant that has been 
in the dark twelve hours with one that has stood in the bright light 
for the same time, using alcohol to remove the chlorophyll and iodine 
for a test for the presence of starch, as before. 
Necessity of Chlorophyll for Photosynthesis.- The plant known as 
Vinca or the ornamental maple has variegated leaves. If a leaf from 
either of these plants is placed in alcohol, it becomes uniform in color. 
If it is then washed and placed in iodine, the iodine brings out the areas 
where the starch was formed but does not bring the areas that were of 
a light color. Such a leaf shows the necessity of chlorophyll in the 
manufacture of starch. 
The blanching of celery is a practical application of the fact that 
chlorophyll cannot develop in darkness. The stalks are either covered 
with earth, or the rows of celery are shut in from the light by long strips 
of black paper which allow only the top leaves to project into the light. 
The white leaves in the heart of a head of cabbage, lettuce, or in opening 
buds in the spring are also accounted for by the fact that they are shut 
off from light by the leaves which surround them. 
331. Protein and Fat Formation. - Proteins are made 
from starches and sugars, carbohydrates, by the addition of 462 
LEAVES- THE PLANT'S WORK-SHOP 
nitrogen. The process takes place in the leaf, as does photo- 
synthesis, but it does not require light or chlorophyll as 
photosynthesis does. Fats, which contain the same sub- 
stances - elements - as carbohydrates, are made by tear- 
ing them down and building them up again in a different 
relation. In any case, a supply of carbohydrates is neces- 
sary for the formation of other kinds of food. One plant 
family makes most of the vegetable protein in the world; 
that is, the Pulse family, to which bean, pea, and clover 
belong. 
LABORATORY STUDY 
Liberation of Gas. - To test the nature of the gas given off by grow- 
ing algae when making food collect a quantity of algae, elodea, or sagit- 
taria and place it in a deep glass jar in the sunlight. When bubbles 
begin to show, place an inverted funnel over the algae. Fill a test tube 
with water and invert it over the upright stem of the funnel. When 
an inch or more of the gas has collected in the test tube, remove it care- 
fully, and thrust a glowing splinter into it. Increased brightness of the 
glow or bursting into flame shows that oxygen is present. 
Land Plants.- Gather leaves of land plants which have large smooth 
petioles, such as calla, dock, and rhubarb (pieplant). Put them into 
dishes of water and stand the dishes in the light. When bubbles appear 
on the petioles or on the under sides of the leaves, collect the gas. In- 
vert a test tube full of water and pass it gently over the surface of the 
leaf or petiole, inclining both the leaf and the tube to catch the gas 
as the bubbles are dislodged. Test the gas with a glowing splinter. 
Another method, less accurate, but less trouble, is to dislodge as many 
of the bubbles as possible by a sharp blow on the container, causing the 
gas to pass into an inverted funnel, or to be more or less confined under 
a cover. A smoldering splinter will glow more brightly or burst into 
flame according to the success of the experiment. 
LABORATORY WORK ON TRANSPIRATION 
Liberation of Water Vapor. - Turn the under side of a geranium 
leaf or other large leaf so it lies against a cool window pane, holding it 
there in some way if necessary. After half an hour remove it and note 
the drops of moisture which resulted from transpiration. Try other 
leaves in the same way. Fasten a watch crystal to the under side of a ECONOMIC USES OF LEAVES 
463 
leaf, using clips to hold it and vaseline to make the edges air tight. Do 
the same with the upper side of another leaf. Which side gives off 
moisture as shown by drops on the watch crystal ? Plunge a large leaf 
into water and set in the sun. On which side do bubbles appear? 
Wait half an hour. What kind of gas do they contain ? What process 
in the leaf produced them? If you cannot answer this now, try again 
after reviewing photosynthesis. 
Take three leaves from the same plant. Coat one on both sides with 
paraffine or vaseline, one on the upper side only and one on the lower 
side only. Lay them aside till your next laboratory period. Describe 
all three. Which is least wilted? Why? Lay them all aside till all 
are wilted, observing them now and then and making a record of what 
happens. Use an uncoated leaf as a check. 
Hold a leaf up to the light and notice the arrangement of the veins 
and the soft parts. 
Thoroughly water a fern or other plant growing in a jar. Cover 
the earth with tinfoil, oilcloth, or paraffine to prevent evaporation 
from the surface. Weigh it carefully, then let it stand on the scales, 
adding weights from time to time to take the place of the water lost 
by evaporation. If the plant has large leaves, remove them; after 
the experiment is completed, draw their outline on cross section paper 
and find their combined surface. Compare it with the amount of 
water lost. At the same rate, estimate how much would be given off 
by a plant with a leaf surface ten times as great, or as many times as 
great as you please. Describe the whole experiment in writing, illus- 
trating with sketches or photographs, as you please. 
Cover a small fuchsia or balsam overnight with a bell jar. Where 
are the guttation drops found? Why do they form there? Cover 
young plants of oats, wheat, corn, or grass in the same way. Where 
are the drops formed on them? Make drawings of one or more kinds 
of leaves used in this experiment. Write notes telling what you dis- 
covered. 
332. Economic Uses of Leaves. - The leaves of all the 
grasses as well as their stalks are used as food for cattle. 
Man uses for food the leaves of cabbage, lettuce, spinach, 
celery, parsley, kale, kohlrabi, and Swiss chard; and as a 
beverage, the leaves of the tea plant. The leaves of winter- 
green, spearmint, peppermint, and sage are used for flavor- 
ing, and the leaves of some plants, mullein, boneset, catnip, 
peppermint, wintergreen, wormwood, and many others for 464 
LEAVES - THE PLANT'S WORKSHOP 
medicine. In the tropical countries some broad leaves arc 
used for thatching - thus affording shelter. 
HOME STUDY 
Using an encyclopedia, find out all you can about the making of ex- 
tracts. Make a list of plants which are used as flavoring. Make an- 
other list of plants the leaves of which are used as medicine. What 
plants produce essential oils? For what are they used? What is 
meant by a "synthetic oil"? 
What plants are used as perfumes? How are perfumes made? 
Look up in the dictionary the meanings of such terms as decoction, 
infusion, vermifuge, expectorant, soporific, and others you find in con- 
nection with the uses of leaves of medicinal plants. 
OUTLINE 
Structure of leaf 
Blade 
Petiole 
Stipules 
Venation 
Parallel 
Netted 
Palmate 
Pinnate 
Arrangement 
Spiral 
Alternating 
Rosette 
Simple leaves 
Apple 
Maple 
Compound leaves 
Clover 
Horse Chestnut 
Falling leaves 
Reduce transpiration 
Get rid of waste 
Modified forms 
Tendrils 
Thorns 
Leafless plants 
Asparagus 
Smilax 
Movement of leaves 
Follow sun 
Fold at night 
Cross section 
Epidermis 
Cutin 
Stomata 
Mesophyll 
Palisade 
Spongy layer 
Adaptations 
Prevent evaporation 
Allow entrance of air 
Exit of water 
Functions 
Photosynthesis 
Respiration 
Digestion 
Circulation 
Assimilation 
Excretion REFERENCES 
465 
Photosynthesis 
Process 
Products 
Use 
Comparison 
Importance 
Transpiration 
Stomata 
Regulation 
Cutin 
Guard cells 
Wax 
Curling edges 
Protein and fat formation 
Economic uses 
SUMMARY 
The leaf is the organ of greatest use to the plant in performing the 
processes which maintain its own life. In the leaf food is manufactured, 
digested, and assimilated. Its cells carry on excretion and respiration 
to a greater degree than any other cells of the plant. 
The purpose of the shape, size, and arrangement of leaves is to enable 
them to get the greatest amount of light and air possible. 
On the process of photosynthesis depends the whole world's supply 
of food. 
QUESTIONS 
Name the processes carried on by the leaves. Which is of the great- 
est use to man? Why? What is the object of leaf arrangement? 
Describe the structure of a leaf. What two purposes are served by 
veins? Mention at least four plants that have peculiar leaves. De- 
scribe each and tell how it helps the plant. 
REFERENCES 
Bergen, Foundations of Botany, pages 130-177. 
Bergen and Caldwell, Practical Botany, pages 13-20, 39-103. 
Bergen and Davis, Principles of Botany, Chapters X, XI, XII. 
Conn, Biology, pages 114, 129, 135, 218. 
Coulter, Barnes, and Cowles, Textbook of Botany, Vol. I, pages 
250, 319-343. 
Curtiss, Nature and Development of Plants, Chapter I. 
Gager, Fundamentals of Botany, pages 26-46. 
. Gibson, Sharp Eyes, pages 121-127. 
Snyder, General Science, page 193. CHAPTER XXVIII 
STEMS, THE PLANT'S TRANSPORTATION SYSTEM 
Two lovely berries molded on one stem.-Shakspere 
333. Kinds of Stems. - The stem is that part of the 
plant which connects the roots and the leaves. There are 
only two kinds of stems so far as structure is concerned. In 
one kind, the fibro-vascular 1 bundles are scattered through- 
out the pith. In the other, they are arranged around the 
outside of the stem with pith in the center and, in the early 
stages, with pith between them also. Stems with scattered 
bundles are always found in plants that have one cotyledon,2 
as corn, grass, palm. Stems with fibro-vascular bundles 
arranged around the outside are always found in plants that 
have two cotyledons, as the bean, and all woody trees. 
A monocotyledonous stem is covered with a hard rind 
which contains silica, a substance like glass which makes it 
hard and strong. In grasses the stem is hollow, and the 
bundles are around the edges, some of them passing off at 
each node into the leaf which arises from it. 
In a woody stem there are only a few fibro-vascular bundles 
when the stem is young. As the stem grows in thickness 
to support more leaves, new bundles grow between those 
1 Vascular bundles are a part of the conductive system of the plant. 
They are in stem, root, and leaves. In the leaves we call them veins. In 
celery they are the "strings" (see Figure 288). 
2 The rudimentary leaf in the embryo of plants, the lobe of the seed. 
466 POSITION OF STEMS 
467 
already there to carry water to the new leaves. A complete 
ring is thus formed, with a few pith cells crowded between 
the bundles. As the stem grows, the bundles take up most 
of the space, so that a mature stem has a much smaller pith 
than a young one. 
334. Functions and Adaptations of Stems. - The stem is 
of use to the plant for support, in being the place for the 
attachment of leaves, and in providing a path for the vessels 
which carry water from the roots where it is gathered to the 
leaves where most of it is used. A fourth use of stems is 
for the storage of food, as in the potato. A few plants make 
use of stems for propagation, as in the case of the strawberry 
and the black raspberry. (See page 480.) 
It is adapted to its work (1) in being compact and sturdy, 
enabling it to bear weight; (2) in branching, to afford a 
larger number of points for the attachment of leaves ; (3) (in 
some cases) in being provided with thorns or briars, as in the 
blackberry and rose, to protect it from being injured by 
animals; (4) in being covered with a strong epidermis or, 
in woody stems, with bark which protects it from outside 
injury and keeps it from drying up; (5) in plants which 
grow in the water, in having large air spaces to carry air 
to the roots which lie in the mud at the bottom of the water. 
The hard outer rind makes a monocotyledonous stem 
rigid, and the pith makes it light. Monocotyledonous stems 
are usually tall and slender and do not sustain great weight. 
A dicotyledonous stem is usually stouter, and its woody 
structure enables it to bear a heavy load of leaves and fruit. 
335. Position of Stems. - Stems assume a variety of 
positions, but that which serves the purpose of most plants 
best is the upright, independent position. Any tree illus- 
trates this kind of stem. A few which are upright keep that 
position by twining or by clinging to an upright support, 
which may be some other plant. These plants have com- 
paratively weak stems. Creeping or trailing stems lie on 468 
THE PLANT'S TRANSPORTATION SYSTEM 
the ground with only the tip erect. This position is illus- 
trated by the habit of the ground pine and by the running 
blackberry. 
336. The Duration of Stems. - The length of life of a stem 
depends upon its habit in producing seeds. An annual or 
herbaceous stem, like the morning-glory or the lady-slipper, 
dies at the end of the first season, the plant having produced 
its seeds. Other stems, like the trees, last year after year. 
Some of the redwood trees in California are known to be 
more than three thousand years old, and the Cedar of 
Lebanon, growing in Asia Minor, is known to live equally 
long. 
STUDY OF WOODY STEMS 
Draw a twig of horse-chestnut in winter condition. Label rings 
(scars of scales), terminal bud (on end), lateral buds (on sides), leaf scar 
(oval mark below bud), vascular bundles (on leaf scar). How many? 
How are the lateral buds arranged? Remove the scales carefully. 
Count and draw them. Describe them. What do you find inside? 
Draw and describe. 
Compare with twigs of other trees - hickory, elm, maple, basswood. 
What differences do you notice ? 
337. External Appearance of Woody Stems. - If we take 
for an example a twig of the horse-chestnut, we shall find on 
the outside a brownish bark, some scars showing the position 
of last year's leaves, and some rings extending around the 
twig, indicating where the scales were attached that covered 
the bud containing these leaves. Above this scar will be 
found a bud covered with sticky scales, and at the end of the 
twig a large terminal bud. 
The buds which grow above the leaves are called axillary 
buds. If more than one of these is found in an axil the 
additional ones are called accessory buds. The strength of 
the terminal bud determines the kind of branching of a trunk. 
A single very strong terminal bud gives the excurrent (Latin, 
ex, out; curro, run) trunk of the evergreen trees, and a TISSUES IN A WOODY STEM OF DICOTYLEDON 
469 
number of terminal buds of equal strength give the deliques- 
cent (Latin, de, from ; liquescere, to become liquid) branching 
of the elm and other trees. Between these 
extremes there are many intermediate 
forms. 
The buds for next season's leaves are 
formed very soon after the leaves have 
reached their full size in the spring. 
Buds are protected in winter by coverings 
of scales which prevent them from be- 
coming dry. A bud may contain leaves 
only, or flowers only, or both. Small 
markings on the smooth bark are lenticels, 
spots where the outer layer of the branch 
is broken, allowing air to enter the inner 
portions. 
338. Tissues in a Woody Stem of 
Dicotyledon. - The study of a young 
woody stem shows not only the tissues 
of which it is composed but also the use 
which each one is to the stem and their 
relations to each other. The same kinds 
of relations can be seen in the tissues and 
cells which make up the organ of an ani- 
mal. (See page 418.) 
Pith, which occupies the center of a 
stem, is made up of large cells with thin 
walls. In the early stages of the plant's 
life, it serves as a place for the storage 
of food. Later it dies, and in an old stem 
often turns brown. Pith is smaller in an 
old stem than in a young one, as the 
woody layers crowd and compress it. 
Near the outside of the stem are the 
fibro-vascular bundles, which are the con- 
Figure 284. -■ Twig 
of Horse-chestnut. 
A, growth made 
last season; B, ter- 
minal bud; C, lateral 
bud; D, leaf scars; 
E, fibro-vascular bun- 
dles; F, rings^made 
by scales of last 
year's terminal bud; 
G, lenticels. 470 
THE PLANTS TRANSPORTATION SYSTEM 
ductive vessels of the plant. In a young stem, these lie in 
an incomplete ring with broad strips of pith between them. 
As the stem grows, more bundles develop between those 
already there, compressing the pith into narrow strips called 
Figure 285. - Excurrent Stem (Trunk) of Evergreen. 
The large trees in the foreground are redwood, probably hundreds of 
years old. TISSUES IN A WOODY STEM OF DICOTYLEDON 
471 
pith rays. These still serve to store food and to conduct 
water and other substances from the outer to the inner 
portions. 
A fibro-vascular bundle in a woody stem is composed of 
three parts. On the inside is the xylem, consisting of thick- 
walled cells, and serving to convey water upwards. On 
the outside is the phloem, of larger thin-walled cells which 
serve to conduct prepared digested food downwards. Be- 
tween the two is 
the narrow cambium 
layer, which is made 
up of small, thin- 
walled, regular 
brick-shaped cells. 
This is the region 
where growth takes 
place most rapidly. 
The brick-shaped 
cells on the inside of 
the cambium layer 
gradually change to the thick-walled xylem cells, and those 
on the phloem or outside of the bundle turn to larger, but still 
thin-walled phloem cells. As more and more bundles grow 
in the ring, the cambium layers touch and become a contin- 
uous ring. Thus it happens that a woody stem can add a 
layer of wood on the inside of the cambium, and a layer of 
phloem on the outside every year. It is easier to trace the 
woody rings, however, for they are protected and do not 
change, while the bark formed from the phloem cracks and 
falls off in bits, making it difficult to trace the annual 
rings. 
The rays of pith between the fibro-vascular bundles of a 
young woody stem are gradually replaced by the medullary 
rays. These are woody cells of a special kind which arise 
from the cambium layer. Their function is to store food and 
- bark 
- central pith 
^■pith rays 
Figure 286. - Cross Section of Young 
Dicotyledonous Stem. 472 
THE PLANT'S TRANSPORTATION SYSTEM 
to form a connection between the cambium and the inner 
parts of the stem. Only the earliest ones formed extend to 
the pith. Later ones start in the cambium and extend into 
the wood for varying distances. The ones that extend to the 
pith are primary medullary rays, and the shorter ones secon- 
dary medullary or wood rays. 
The bark of the older stem and the epidermis of a young 
stem are its protection against drying out, and against the 
attacks of insects as well as against the entrance of the spores 
of bacteria and fungi. Its porous structure also admits air 
to the interior of the stem. In the epidermis or the very 
thin bark of a stem are irregular openings called lenticels. 
These disappear as such when the bark becomes thick, but 
the air can still get in. All these parts, pith, woody portion, 
phloem, pith rays, and epidermis or bark combine to make 
up the stem, and at the same time each has a definite service 
to perform in the life of the whole plant. 
339. Growth of Stems. - Most woody plants grow 
rapidly in the spring and early part of summer, after which 
they cease increasing in size but continue to add material 
which makes wood, thus enabling the stems to resist being 
killed in the winter. Such plants are said to have a definite 
annual growth. This is illustrated by most woody trees. 
Other plants continue to grow until the end of the season. 
The latest formed wood in such plants is usually killed by the 
frost, with the buds on it. The plant begins to grow next 
season from axillary buds below the point where it was killed. 
Such plants are said to have indefinite annual growth. Ex- 
amples are red raspberry and sumac. 
Advantages of definite annual growth are twofold: (1) it 
enables a tree to grow very rapidly in the spring when con- 
ditions are most favorable for growth, and (2) it does not 
result in the loss of any wood once formed. On the other 
hand, the plant which makes an indefinite annual growth 
can take advantage of favorable growing conditions when- TISSUES IN MONOCOTYLEDONOUS STEMS 
473 
ever they occur, although it may lose some of its youngest 
wood if frost comes before it is hard enough to resist it. 
In the annual growth of woody stems, a new node is added 
to each branch, and a new layer of wood over the wood of 
previous years. This makes it possible to tell approximately 
how many years old a tree is, the growth of each year forming 
a ring more or less distinct according to conditions. When 
the conditions for growth are at their 
best, the cells formed are large. As 
conditions become less favorable, the 
cells become smaller and have thicker 
walls, marking distinctly the end of 
one season's growth from the be- 
ginning of the next. The size of the 
cells varies greatly in different trees, 
producing the " grains " which are so 
characteristic of each kind of lumber. 
340. Monocotyledonous Stems.- 
In the corn stalk, a monocotyle- 
donous stem, the vascular bundles 
are scattered throughout the central 
pith, and the bundles have no definite 
position with reference to the center. 
The outside of the stem is covered 
with a hard rind which often contains 
silica, a substance like glass which 
makes it hard and strong. In grasses, 
the stem is hollow, and the bundles 
are of course around the edges, some of them passing off at 
each node into the leaf which arises from it. 
341. Tissues in Monocotyledonous Stems. - A vascular 
bundle in a monocotyledonous plant is made up of two kinds 
of cells or groups of cells called xylem (zy'lem) and phloem 
(flb'em). The xylem cells are thick-walled, but with thin 
spots in each cell where it touches another cell of the same 
scars of 
-prop roots 
-node 
-vascular 
bundles 
■hard outer 
rind 
-pith 
-vascular 
bundles 
Figure 287. - Broken End 
of Corn Stem. 474 
THE PLANT'S TRANSPORTATION SYSTEM 
kind. Each cell is long and pointed. Some of these cells 
overlap in such a way that they make continuous tubes from 
the root, up through the stem, and into the leaves. The thick 
walls help to give firmness to the plant. 
The phloem cells are the other part of the vascular bundle 
in a monocotyledonous stem. They have thinner walls than 
the xylem cells and they communicate with one another 
through the ends and not 
through the sides. The 
ends of these cells have 
perforated plates through 
which the liquid in the 
cells passes. These are 
called sieve plates. 
342. The Work of the 
Vascular Bundle. - We 
have said that the vascu- 
lar bundles are a part of 
the conductive system of 
a plant, and that some 
of the cells form vessels. 
There is little likeness to 
the vascular system of 
animals, however, for the 
system in plants lacks an 
organ for driving the 
liquid in the tubes, and it has little use as an aid to respiration. 
Water, absorbed from the soil by the root hairs, is passed by 
osmosis to the slender cells in the roots, and from there up 
through the stem and to the leaves, where it is used in photo- 
synthesis. After the food made by photosynthesis is 
digested and thereby made ready for the use of the plant, 
some of it is carried down through the phloem part of the 
vascular bundle to such parts of the plant as need it. There 
is in this a likeness to the circulation of animals in which 
hard rind, 
.fibro-vascular 
bundles J 
Figure 288. - Cross Section of Mono- 
COTYLEDONOUS STEM. 
Showing scattered fibro-vascular 
bundles. PRACTICAL APPLICATIONS 
475 
fresh blood is carried in one set of vessels and blood that 
needs renewing in another set. The liquid which is carried 
in the vessels of plants is commonly called sap, and when 
a plant is broken, and the sap oozes out, we speak of it as 
bleeding. 
HOME WORK -STEMS 
1. Examine the house you live in to learn, if'possible, the kinds of 
lumber used for the floors, for the casings, and for the doors. What 
kinds do you like best? Why? 
2. Examine all the wooden furniture and answer the same questions. 
3. Examine the different kinds of matting. Of what is each made ? 
Examine linoleum. Of what is it made? 
4. Examine the wicker furniture. Of what is it made? What is 
rattan ? bamboo ? 
5. Examine your "straw" hat. Of what is it made? How? 
6. Examine the doormat. Was it made from any part of the stem 
of a plant? 
7. Examine the clothes-basket and the market-basket, and the 
sewing-basket, and try to decide from what each was made. 
8. Examine a trunk, a box, a barrel, a pail, a picture-frame, a har- 
ness, a wagon, an automobile, a fence, telegraph poles, paving blocks, 
corks, and toys of various kinds, to find what parts of them are made 
from wood, and what kinds of wood are used. 
9. Make a fist of all the other things, as spools, that are made of 
wood. 
10. What substitutes for wood do you find? In what respects are 
they better? in what respects inferior to wood? 
11. How is paper made? 
12. What is celluloid? 
13. Where is thatch used? 
14. What is oakum? In what industry is it used? 
15. Why is excelsior a good material for packing fragile articles? 
16. Into which of your garments does linen enter? 
17. What is jute? manila? burlap? 
18. How many trees do you know ? Which do you like best ? Why ? 
343. Practical Applications-Stems as a Means of 
Propagating Plants. - Stems are used in various ways in 
propagating plants. " Slipping " plants is a common prac- 476 
THE PLANT'S TRANSPORTATION SYSTEM 
tice, the success of which is due to the fact that adventitious 
roots grow readily from the cut end of a branch of geranium, 
balsam, ivy, and other plants. Two advantages make slip- 
ping popular: (1) the certainty of securing a new plant 
like the parent plant, (2) the short time required to pro- 
duce blooms compared with that for the same kind of 
plant raised from the seed. Willow twigs root so readily 
that it is often possible to start a hedge by sticking pieces 
of branches into the ground when it is very wet. 
Grafting. - (See page 10.) Grafting is a common method 
of propagating trees. It depends for success upon putting 
the cambium layer of a twig from one plant against the cam- 
bium of another and fastening it there until the two layers 
have grown together, protecting it from moisture, insects, and 
fungi by a layer of wax. Usually a twig from a mature tree 
(the scion) is grafted upon the young stem of a seedling or on 
an inferior tree (the stock), producing fruit several years 
earlier than the seedling tree would. One can be sure, too, of 
obtaining the fruit wanted. If twigs from several kinds of 
trees be grafted upon a " scrub " tree, each twig will bear its 
own kind of fruit. The pome fruits, drupe fruits, and citrus 
fruits are usually grafted. Greenhouse roses, azaleas, and 
other plants are propagated in this way. 
Budding. - Budding is a process similar to grafting except 
that a bud is slipped into an incision in the bark, instead 
of a twig being inserted into the end of a branch. (See 
page 9.) 
Layering. - Layering is a method of obtaining new plants 
by covering a branch with earth some distance from its tip. 
When roots form, the branch is severed from the main plant 
and transplanted. Roses, grapes, and currants are propa- 
gated by layering. All these methods are artificial, and 
seldom found in nature. 
Pruning. - Pruning is advisable for the following reasons : 
(1) to make the tree a better shape and to remove superfluous PRACTICAL APPLICATIONS 
477 
branches and those not well situated to bear fruit; (2) to 
remove broken or dead branches; (3) to make the sap form 
fruit instead of new vines or branches. 
Pruning should be done carefully. Branches should be 
sawed off smoothly as close to the trunk as possible. This 
will enable the wounds 
to heal more quickly 
and be less unsightly. 
Healing is accomplished 
by the growth of a 
special kind of tissue 
which forms from the 
ring of exposed cambium 
and grows inward. 
When a branch is 
sawed off, the wound 
should be covered with 
paint at once to prevent 
the entrance of bacteria 
and spores of fungi. 
Pruning should not be 
done when the sap is 
running freely, for bleed- 
ing weakens the tree or 
vine. 
Girdling. - When a 
tree is " girdled " with 
the purpose of killing it, 
the cut must be deep 
enough to reach and de- 
stroy both xylem and 
phloem. If only the phloem vessels are cut, the tree will 
continue to grow above the incision, since water can ascend 
through the uninjured xylem vessels to the leaves. If 
the supply of water is stopped by cutting out all round the 
Figure 289.-'Giant Cactus. 
The stem is adapted to perform photosyn- 
thesis and to reduce transpiration. 478 
THE PLANT'S TRANSPORTATION SYSTEM 
tree a section of the xylem vessels which carry it up, wilt- 
ing will soon take place owing to the continued loss from 
transpiration. The manufacture of food will cease on ac- 
count of the lack of water, and the tree will die. When 
young trees are girdled by rabbits, as sometimes happens in 
winter, the space can be filled in with split twigs carefully 
adjusted as in a graft, and growth will continue. 
344. Specialized Stems. - In regions where the climate 
is very hot and dry most of the year, the leaf surface is greatly 
reduced to prevent undue evaporation. In this case the 
stem becomes green and performs the work of photosynthesis 
(see page 477), ordinarily done by leaves. The cactus illus- 
trates this. Certain other plants have no leaves, but the 
stem branches in such a way as to resemble leaves. The 
florist's smilax and asparagus fern represent this kind of 
branching. The true leaves are reduced to minute scales. 
LABORATORY STUDY OF STEMS 
Draw a potato. Label the "eyes" buds. On which end are they 
more numerous? Label scale, just below bud. Note end where it was 
attached to the main plant. 
Cut off the stem end and stand in water colored with red ink. After 
two hours examine again and note what part is stained. Cut off slices 
till traces of color disappear. Draw to show where it is colored. Cut 
a thin slice and put a few drops of weak iodine on it. What happens? 
What does it show? 
Cut an onion bulb vertically. Note the condensed stem on which 
the leaves are arranged. 
345. Underground Stems. - An underground stem can 
always be distinguished from a root by the buds of new 
leaves or the scales of old ones, although in some the leaves 
are reduced to mere scales, as in the potato. Underground 
stems usually send up aerial shoots. They often have an 
advantage over an aerial stem in being better protected. 
Some plants make use of the underground stem in propagat- 
ing themselves. UNDERGROUND STEMS 
479 
Canada thistles, quack grass, and devil's paint-brush are 
among the most difficult of weeds to eradicate, owing to their 
branching, underground stems, each piece of which, when 
broken off by cultiva- 
tion, forms a new plant. 
Dandelions, because of 
their greatly reduced 
stems, are not easily 
killed by trampling. In 
digging dandelions from 
lawns, care must be 
taken to cut deeply 
enough to remove the 
whole crown of the plant, 
otherwise the injured stem branches and forms a weed more 
troublesome than the original one. 
Bulbs. - The bulb, a common form of underground stem, 
has a somewhat flat and disc-like appearance. The roots 
sprout from the under side, and above are found tightly 
compressed, fleshy leaves. The 
hyacinth and the onion are ex- 
amples. 
Corms. - In appearance corms 
resemble bulbs but, contrary to 
the leafy structure of bulbs, 
corms are solid, fleshy stems with 
the leaves and buds growing 
from the upper surface and the 
roots from the lower, as for in- 
stance in the cyclamen. In some 
corms, such as the crocus, there is an outer covering or 
sheath of one or two leaves which causes them to be given 
the name of solid bulbs. 
Tubers. - A tuber is usually round or oblong and consists 
of a branch-like body which is much thickened and which 
Figure 290. - Dandelion. 
This plant has no visible stem. 
-Remains of 
Old Leaf 
Bud 
•New Corm 
Roots 
Corm 
Figure 291. - Corm of Indian 
Turnip. 
This shrivels as the stored 
starch is used by the growing 
plant. 480 
THE PLANT'S TRANSPORTATION SYSTEM 
has many " eyes," the modified axillary buds. Usually 
some of these buds produce a new plant the next season, 
the nourishment for which is stored in the 
form of starch in the tuber. The potato 
illustrates this variety of underground 
stem. 
Rhizomes. - This stem has a root-like 
appearance. It may be found lying on the 
ground or under ground. It has scales in- 
stead of leaves. At its apex grows a leafy 
shoot. Rhizomes vary in structure. They 
are sometimes slender with the nodes plainly 
visible, sometimes thick and solid-looking, having the nourish- 
ment stored in them for the new plant. Mints are examples 
of the former, Solomon's seal of the latter variety. 
346. Stolons. - Other plants 
propagate themselves by stems 
naturally, as the strawberry, which 
puts out long, leafless branches 
called stolons or runners, each 
stolon having a bud on the end 
which takes root when it finds 
favorable conditions, especially 
contact with the soil. When a 
new plant is well established the 
stolon ceases to carry nourishment 
from the parent plant and soon 
dies. Black raspberries produce 
long, drooping stems which have 
buds on the ends similar to those 
on the stolons of strawberries. 
New plants are formed when these 
rest on the earth, several sometimes arising from the 
branching end of a parent plant, from which it later be- 
comes separated. 
Grains of potato 
starch, highly mag- 
nified. 
Figure 292. 
Figure 293. - Potato, a Com- 
mon Tuber. 
A form of underground fern 
used for storing food, chiefly 
starch. USES OF THE STEM TO MAN 
481 
A large garden lily has a method of propagating itself 
that is not common, namely by bulblike growths produced 
in the axils of the leaves. 
LABORATORY STUDY: COURSE OF SAP 
Place a living pea seedling in water containing eosin. If possible, 
use one that has been germinated in sawdust in a paper cup. Make 
a hole in the bottom of the cup, and set 
it into a tumbler of water containing 
eosin or red ink. After two or three 
hours note the presence of eosin in the 
stems and leaves. Repeat the experi- 
ment, using a seedling that has been 
grown in the dark. Compare with one 
that has been grown in the light. 
Stand twigs of apple, maple, elm, and 
other trees in water colored with red 
ink or eosin. Examine after two hours, 
also after standing overnight. Split the 
twigs lengthwise, and cut the ends 
squarely and obliquely, to see the path 
taken by the colored water. 
347. Uses of the Stem to Man. 
- Man makes use of the stem for 
food, the potato being one of the 
most familiar as well as important 
examples of such use. Starch is 
also made from potatoes. The stem and buds of asparagus 
are used for food. 
A second use is for shelter. Trees furnish lumber in all 
its varieties. Some parts of houses can be made from stone, 
brick, or other materials, but for the inside finishing we are 
still dependent upon wood. 
A third use is for furniture. No other material has been 
found that is so satisfactory as wood for tables and chairs. 
A fourth use is for clothing. The flax plant which fur- 
nishes the material from which linen is made is one of the most 
Figure 294. -Rhizome of 
Pteris, a Common Fern. 482 
THE PLANT'S TRANSPORTATION SYSTEM 
valuable. Its usefulness depends upon the bast fibers which 
it contains. These are found in the outer part of the slender 
stem and serve to give it stiffness. When separated from 
the other parts of the stem they can be twisted, spun, and 
woven. 
Fifth, the stems as well as the leaves of peppermint, bone- 
set, wormwood, catnip, foxglove, and other plants are used 
as medicine. 
A sixth use is for cordage. This includes all kinds of ropes 
and many kinds of strings. Some cordage is obtained from 
fibers of hemp, and some 
from other plants. 
Seventh, in many 
places wood used as fuel 
is the only source of heat 
for cooking and keeping 
warm in winter. 
Among the many other 
uses of stems in our daily 
life may be mentioned 
poles for telegraph, telephone, and electric light wires, 
for the masts of ships, for the piles of piers, timbers for 
props of mines, lumber for bridge foundations, cross ties of 
railroads, besides parts of implements and tools of daily 
use, vehicles and parts of machines by which many of 
these are made. Add to these the boxes, barrels, crates, 
trunks, pails, baskets, and other common articles which we 
use frequently, and paper in its many forms and numerous 
uses. It is evident from this list, which is far from complete, 
that man has found the stems of plants to be of great use 
to him, and that he could not well do without them. 
Adaptations of Wood. - When we compare the number 
of articles that are made of wood with the same articles made 
of substitutes, we see that there are some good reasons for the 
use of wood. Among these are its lightness compared with 
.epidermis 
mechanical 
tissue 
--conductive 
tissue 
-Fundamental 
tissue 
Figure 295. - Cross Section of Under- 
ground Stem of Pteris, a Common Fern. USES OF THE STEM TO MAN 
483 
iron or steel for use in furniture, trunks, and other articles, 
its elasticity, its toughness, its durability, especially when pro- 
tected from dampness, the ease with which it can be shaped 
by tools, and its beauty, depending on color and grain, and 
on the high polish it can take. 
OUTLINE 
Kinds of stems 
Monocotyledonous 
Dicotyledonous 
Functions 
Support 
For plant 
For leaves 
Water carrier 
Food storage 
Position 
Upright 
Trailing 
Duration 
One year 
Three thousand years 
Appearance 
Scars 
Buds 
Axillary 
Accessory 
Terminal 
Excurrent 
Deliquescent 
Dicotyledon 
Pith 
Pith rays 
Fibro-vascular bundles 
Xylem 
Cambium layer 
Phloem 
Bark 
Medullary rays 
Wood rays 
Growth 
Annual 
Definite 
Indefinite 
Monocotyledon 
Vascular bundles 
Xylem 
Phloem 
Sieve plates 
Work 
Applications 
Grafting 
Budding 
Layering 
Pruning 
Girdling 
Specialized stems 
Cactus 
Smilax 
Underground stems 
Bulbs 
Corms 
Tubers 
Rhizomes 
Stolons 
Uses of stems 
Food 
Shelter 
Furniture 
Clothing 
Medicine 
Fuel 484 
THE PLANT'S TRANSPORTATION SYSTEM 
The stem is the part of the plant which forms the connection between 
the roots, which gather food materials, and the leaves, where food is 
manufactured. It is compact and sturdy because it must bear the 
weight of the leaves and branches, and because the vessels through 
which liquids are conducted in it must be well protected. Most stems 
grow above ground and upright, but some lie on the surface of the 
ground, and some below the soil. The stem of the woody plants is em- 
ployed by man in more ways than any other part, furnishing him shelter, 
fuel, furniture, clothing, paper, parts of many machines and implements 
on which he is daily dependent. Stems are a source of some food for 
man and the stems of the grasses furnish food for many animals. 
SUMMARY 
QUESTIONS 
What is the stem? What is its use to the plant? What positions 
do stems take ? How long do they live ? Name and describe the pecul- 
iar stems. What are vascular bundles? How are they arranged in 
a monocotyledonous stem? In a dicotyledonous stem? What is their 
work? What is meant by definite annual growth? Indefinite annual 
growth? What are annual rings? How are they formed? 
REFERENCES 
Bergen, Foundations of Botany, pages 62-129. 
Bergen and Caldwell, Practical Botany, pages 11-13, 39-103. 
Coulter, Plant Life and Plant Uses, pages 49 and 143-193. 
Gibson, Sharp Eyes, pages 48-51, 240-243. 
Snyder, General Science, page 188. CHAPTER XXIX 
THE ROOT, THE PLANT'S ABSORBING ORGAN 
AND ANCHOR 
The bended twigs take root, and daughters grow 
About the mother tree, a pillar'd shade 
High overarch'd and echoing walks between. 
- Milton 
348. Structure of Roots. - The outer part of the primary 
root is covered with a layer of epidermis which acts as a pro- 
tection layer. Inside of this is 
a region called the cortex which 
surrounds the central cylinder. 
Near the tip at the farther end 
of the central cylinder is the 
Epidermis 
Cprtex 
.Central 
Cylinder 
Vascular 
'Bundles 
/-Central Cylinder 
Epidermis 
-Cortex 
Epidermis 
Cortex 
Central 
Cylinder 
-Meristem 
•Root Cap 
Vascular 
Bundles 
Figure 297. - Vertical Sec- 
tion of Root. 
Figure 296. - Cross and Longi- 
tudinal Section of Root. 
The meristem is the growing 
region. 
main growing region from which the epidermis, the cortex, and 
the central cylinder are formed. At the tip end of the root is 
a root cap which is the protective tip for the growing root. 
485 486 
THE ROOT 
The secondary roots which branch off the mam roots 
start from the central'cylinder. Each of these parts of a 
root adapts it to do its 
work. The epidermis 
keeps it from drying. 
The region of the central 
cylinder contains the 
conducting vessels which 
carry water to the stem 
and digested food back. 
The cortex is the region 
in which most of the 
food is stored. 
The root cap protects 
the tender end of the 
root from injury as it 
pushes through the soil, 
and the growing tip pro- 
vides for renewing all 
the regions of the root 
and increasing their size. 
Besides the main root, there are many smaller roots which 
divide still further into rootlets. The root and its divisions 
Figure 298. - Cross Section of Root with 
Root Hairs. 
These were grown in moist air. Compare 
with those grown in soil. 
nucleus^. 
epidermal 
cells I 
Figure 299. - Bit of Epidermis of Root, Showing Origin of Root Hairs. ROOT HAIRS 
487 
underground may be compared, in a general way, to the stem, 
branches, and twigs above ground. 
349. Root Hairs. - Root hairs are found a short distance 
back from the tip of each rootlet. Each hair consists of a 
projection of an epidermal cell. Root hairs are very nu- 
merous. As the root grows, the hairs farthest from the tip 
die and are replaced by 
new ones nearer the tip. 
Root hairs greatly increase 
the absorbing surface of a 
rootlet. They attach them- 
selves firmly to particles of 
soil from which they take 
almost every trace of mois- 
ture by osmosis (see page 
42). They also serve to 
fix the plant firmly in the 
soil. 
LABORATORY STUDY 
OF ROOTS 
(a) Cut a root of carrot or 
parsnip lengthwise and identify 
(1) the epidermal covering; 
(2) cortex, the region under the 
epidermis; (3) central cylinder. 
Cut it crosswise and identify 
the same regions. Make draw- 
ings of both sections and label 
fully. In both sections look for 
rootlets and note the region from which they arise. Show this in your 
drawing. 
(b) Examine a root hair to determine its structure. Of how many 
cells is it composed? From what does it develop? 
In a vertical section of a root note the root cap. What is its struc- 
ture? Its use? Where is the region of growth? 
(c) Make a cut through the root of a Tradescantia (wandering Jew) 
and observe the various parts, especially the root cap. 
Figure 300. - Germinating Wheat, 
Showing Root Hairs. 
Notice the plumule growing up and 
the roots down. This grain of wheat was 
germinated in moist air, and not in the 
soil. Root hairs are seldom seen in soil- 
grown seedlings, as they are so fragile 
that they break off and remain in the 
soil when the seedling is removed. 488 
THE ROOT 
350. Primary Functions and Forms of Roots. - Roots 
are the part of the plant that (1) gather water and food 
material from the soil; (2) hold the plant firmly in the soil; 
Figure 301. - Root System of Rhubarb, a Medicinal Plant. 
Food is stored in the larger parts. Note many secondary roots. Many 
of the rootlets have been broken off. 
and (3) in plants that live over the winter, store food to be 
used the following year. 
Tap or primary roots are the first ones formed in many 
plants. Secondary roots branch from the primary. Both THE DURATION OF ROOTS 
489 
are adapted to penetrate the soil deeply, enabling them to 
secure water when plants with different roots cannot. They 
are adapted also to the storage of food. 
Fibrous roots are the many thread-like roots which extend 
in all directions through the soil. 
Thickened fibrous roots are a modification of fibrous. 
Fascicled roots are a cluster of thickened roots for the 
storage of food. 
Some plants like the ivy have aerial roots for attachment. 
Note how they grow from side of stem. Aerial roots may 
also absorb water, as in 
the case of certain or- 
chids, tropical plants 
which grow in the air. 
Water roots lack a root 
cap. The duckweed is 
an illustration of this. 
Knees are the projec- 
tions on roots, as in the 
cypress. 
Adventitious roots are 
those that grow in un- 
usual positions, especially 
from the end of a cut 
stem as in the geranium, 
willow, or any " slip." 
351. The Duration of 
Roots. - Roots which live only for a season are called annual 
roots, examples of which are corn, peas, beans, and other 
common garden plants. Those that store the food manu- 
factured one season and use it to produce flowers and fruit 
the next are called biennial roots. The garden furnishes 
examples of these in the fleshy roots of carrots, parsnips, 
beets, turnips, and vegetable oysters. Roots that live from 
year to year, like those of trees, the dandelion, bur- 
Figure 302. - Fibrous Roots of a 
Buttercup (slightly thickened). 490 
THE ROOT 
dock, horse-radish, peony, and " pie plant," are perennial 
roots. 
352. Extent of Root System. - The root system of a tree 
growing in fertile soil is about equal to the parts above the 
ground. An oat plant has a root system the combined length 
of which is about 154 feet; a wheat plant has single roots 
seven feet long; and alfalfa an enormous root system. A 
single root of alfalfa may extend more than 20 feet in one 
direction in a loose soil. 
Figure 303. - Fascicled Roots of Dahlia. 
Fascicled roots occur in clusters. They are used for the storage of food 
353. Specialized Roots. - The roots of the ivy which 
grow for attachment differ from ordinary roots not only in 
their function, but in their position. They can grow from 
any side of a stem, enabling them to attach themselves to 
a surface wherever they may happen to touch it. 
The haustoria by which parasite plants get their food from 
the host are modified aerial roots. They are able to take 
food from the stem of the host by absorbing pads, as is 
well illustrated by dodder. 
The cypress tree, which grows with its roots submerged, 
has peculiar projections which extend above the surface of SPECIALIZED ROOTS 
491 
the water. These so-called " knees " are so modified that 
the roots are enabled to secure the air they need. 
The pendant roots of the tropical orchids, known as vela- 
mens, have a modified outside layer which enables them to 
absorb almost immediately any water which falls on them 
Figure 304. - Root System of Corn. 
Near the end of the growing season. 
and conduct it to the central cylinder for storage. This 
enables the plants possessing them to live outside of the soil 
successfully. 
Prop roots of corn grow from nodes above the soil, which 
they penetrate. This is an adaptation for holding the plant 
more securely than the ordinary roots could do. When 
mature, they branch freely. z 492 
THE ROOT 
Adventitious roots are those which grow from unusual 
places, especially soil roots. It is the ability to form such 
roots that enables us to " slip " plants like geraniums, bal- 
sams, ivy, and wandering Jew. Such garden plants as 
tomato, cucumber, squash, and others, put forth adventitious 
roots where their stems touch the soil, especially at the nodes 
in the case of the vines named. This is an adaptation which 
gives them a greater supply of food material near the leaves 
which use it, and which enables the plant to live even if 
broken from the main portion of the stem. 
Certain cactus plants which live in the desert have roots 
which are twenty times as long as the parts which appear 
above the soil. This enables them to absorb and to store 
up the scanty moisture. 
LABORATORY STUDY 
Osmosis Experiments. - Prepare an egg for a demonstration of 
osmosis. (See page 42.) When the usual demonstration is completed, 
remove the tube, break the upper part of the shell, and empty contents. 
Fill the shell half full of clear water, distilled or from the tap, and set 
it in a beaker containing sugar and water. After four or five hours 
note (1) increase in amount of water in the beaker, and (2) decrease 
in the amount of water in the shell. Account for what you find. 
Place a filament of spirogyra in strong salt and water and observe 
what takes place, using the high power of a compound microscope. 
Note that the protoplasm shrinks from the wall of each cell, and be- 
comes more condensed. Draw out the salt water and replace with 
distilled water, and observe again. After a few minutes the cytoplasm 
again fills the cell wall. Account for what you have observed. 
Demonstration to Show Region through Which Liquids Rise.- 
Stand cut-off roots of parsnip overnight in water tinted with red ink. 
In what region does the color show? Make cross sections of one and 
longitudinal sections of the other. Draw both and describe. 
Look at the roots of seedlings furnished you. How does the extent 
of roots compare with the parts above ground? 
Examine roots grown in a moist chamber for root hairs. Compare 
with one grown in sawdust or soil after it has been carefully washed. SUGGESTIONS FOR HOME WORK 
493 
How do they differ? On what part of the rootlet are the root hairs 
most numerous? Where are they the longest? 
Mark a root with a fine pen dipped in India ink, making the marks 
even and close together (about 1 mm.). Examine from time to time to 
determine where growth is most rapid as shown by increased distances 
between marks. 
Tests for Foods. - Test roots for the presence of starch, sugar, and 
protein, using the tests suggested for seeds, page 537. Make a report 
on what you find. 
In what direction do roots usually grow? Try to make them grow 
in some other direction. Write what you did and show by drawings 
what success you had. 
Draw aerial roots of an ivy stem. 
Draw a cluster of fascicled roots of a dahlia or a buttercup or an 
anemonella. 
Demonstration to Show the Response of Roots to Moisture. - Fill a 
funnel with sawdust and soak it thoroughly. Wrap it with sheets 
of blotting paper. Fit a ring of cork into the top of the funnel. 
Fasten to this a number of seedlings with short roots, taking pains to 
have them extend along the ring, over the sawdust, and over the edge. 
Place the funnel in a dish of water to keep the sawdust and the blotting 
paper moist. After four or five days examine to see what changes have 
taken place in the position of the roots. Have any left the cork ring 
and entered the sawdust? Have any bent over the edge to get to the 
wet blotting paper ? Have any died because they could not get water ? 
What experiment can you devise that will serve as a check on this 
demonstration ? 
Pull weeds and examine the roots. Which have tap roots? Why 
do they flourish better than the plants around them? 
Cut a piece of thick sod with a sharp spade or trowel. How many 
grass plants in a square two inches on a side ? What kinds of roots has 
grass? Wash the dirt away carefully and measure the extent of the 
root system. Compare it with the part above ground. Do the same 
with other plants than grass. 
On how many nodes of a corn stem do prop roots grow ? What is the 
effect of "hilling up" corn on the production of prop roots? 
Place willow twigs in water. Watch the growth of adventitious 
roots, noting especially the root caps. Do duckweed and other floating 
plants have root caps? Account for what you find. 
Examine a large number of roots and report. 
SUGGESTIONS FOR HOME WORK 494 
THE ROOT 
Primary Fibrous Aerial 
Under- All Under- r r r 
GROUND GROUND 
Dandelion 
Plantain . 
Carrot. . 
Dahlia. . 
Corn . . 
Ivy . . . 
354. Uses of Roots to Man. - In some plants the root is the 
most valuable part for food not only for man but also for his 
animals. Examples of this are found in many of the garden 
vegetables, such as carrot, parsnip, turnip, vegetable oyster, 
and beet. The food stored in the beet is rich in sugar, mak- 
ing it one of the sources of the sugar of commerce as well as 
a valuable food for stock. Other roots furnish substances 
used as medicine when they have been extracted, as rhubarb 
and mandrake, while the ground root of ginger is used in 
medicine and in cooking. The vegetable oyster is often 
found growing by roadsides, where its seed has been blown 
from gardens. 
In the case of these roots, a few must always be saved to 
produce seeds for another crop, inasmuch as turnips, beets, 
carrots, parsnips, and vegetable oysters are biennials, requir- 
ing to be planted the second season, when they use food 
stored during the first year to produce fruit and seeds. 
OUTLINE 
Structure of roots 
Central cylinder 
Cortex 
Epidermis 
Root cap 
Root hairs 
Functions 
Gather food 
Hold firm 
Store food 
Forms 
Tap 
Fibrous 
Thickened REFERENCES 
495 
Fascicled 
Water roots 
Knees 
Adventitious roots 
Duration 
Annual 
Biennial 
Perennial 
Extent 
Specialized roots 
Aerial 
Submerged 
Pendant 
Prop 
Uses 
Food 
Medicine 
Propagation 
SUMMARY 
The root is the part of the plant that grows in the soil to gather water 
and food materials for it, to hold it securely, and to store food for it. 
Roots have many forms, the primary or tap root and the fibrous roots 
being the extremes. Small roots have a root cap to prevent injury to 
their tips, and root hairs to increase their absorbing surface. There are 
specialized roots for special purposes, such as aerial roots for support 
and for gathering water. Adventitious roots are those that grow on 
"slips." Roots form an important part of man's food, and food for 
his animals. 
QUESTIONS 
What is the root? What does it do for the plant? Describe the 
structure of a tap root. How do fibrous roots differ from a tap root? 
In which kind of roots is most food stored? What use does the plant 
make of this stored food? What use does man make? What kinds 
of food are stored in roots? 
REFERENCES 
Bergen, Foundations of Botany, pages 62-129. 
Bergen and Caldwell, Practical Botany, pages 5-16, 24-38. 
Conn, Biology, page 112. CHAPTER XXX 
FLOWERS AND FRUITS 
Mourn, little harebells, o'er the lea; 
Ye stately foxgloves fair to see ! 
Ye woodbines hanging bonnilie 
In scented bowers! 
Ye roses on your thorny tree, 
The first o' flowers. 
- Burns 
355. Introduction. -- The plants we all know and like best 
are those that at some time in their lives produce beautiful 
flowers. These flowers, however, are only temporary struc- 
tures which drop off as soon as their work is done. They 
are the special adaptations of the plant for producing more 
plants. A flower is simply a modified branch, the parts being 
modified leaves. Some flowers, for example the water lily, 
show this plainly at all times, and others show it only under 
certain conditions, as in the case of the rose. 
356. Structure of the Parts of a Flower. - The parts of 
a flower are best studied in some particular plant. The 
following are the parts as found in the nasturtium: 
Sepals (Latin, separ, separate). - These are greenish, 
pointed, leaf-like parts on the outside of the flower. Together 
they make up the calyx (Greek, kalyx, cover), which pro- 
tects the rest of the flower, at least while it is in the bud, from 
insects, cold, rain, etc. One of the sepals has a spur, in the 
bottom of which is a drop of nectar. 
Petals (Greek, petalon, leaf). - The larger parts, more 
showy because more brightly colored, are petals, which taken 
together make up the corolla (Latin, corolla, crown). 
496 STRUCTURE OF THE PARTS OF A FLOWER 
497 
Stamens (Latin, sto, stand). - These are the slender organs 
which surround the most central portion of the flower. The 
stamen has two parts, the filament or stalk, and the anther or 
box at the top, which contains the pollen. 
Pistil. - The central portion of the nasturtium is the 
pistil, made up of three 
parts. At the top is (1) 
the stigma (Greek, stigma, 
point); below it (2) the 
style (Greek, stylos, pillar) 
which connects it with the 
lowest part, (3) the ovary 
(Latin, ovum, egg). 
The sepals and the. petals 
are sometimes spoken of as 
floral envelopes or as acces- 
Stamen 
Pistil 
Sepal 
-Spur 
Figure 305. - Flower of 
Nasturtium. 
1. whole flower. A, sepal; B, petal; 
C, stamens; D, pistil; E, spur. 2. 
petals. 
Figure 306. - Flower of Nastur- 
tium with Petals Removed. 
sory parts, in distinction to the stamens and the pistil, the 
essential parts. Only the latter are necessary for the pro- 
duction of seeds. The nasturtium is a perfect flower be- 
cause it has the parts necessary for the production of seeds, 
and it is a complete flower because it has also the accessory 
parts. 498 
FLOWERS AND FRUITS 
Besides the four sets of parts found m nasturtium flowers, 
other parts will be found in certain flowers, the receptacle, 
for example, the expanded top of the stalk on which the 
floral organs are placed. This is sometimes oval as in butter- 
cups, or large and fleshy as in strawberries, or hollow as in 
the rose, where the pistils arise from its 
inner surface. The crown is a projection 
growing from the surface of a petal as in 
narcissus. The spur already mentioned 
is another modification of a petal or a 
sepal. Violets, snapdragons, toad flax, 
and larkspur have spurs. Nectar glands, 
usually found near the base of a flower, 
are commonly found in those flowers 
which are adapted to attract insects. 
LABORATORY STUDY OF A 
NASTURTIUM 
Provide each pupil with a nasturtium flower. 
Draw the flower, and label the parts as follows : 
(1) sepals, the outermost, greenish parts; (2) 
petals, the colored, larger parts; (3) stamens, 
the slender parts inside the petals; (4) pistil, 
the central part of the flower; (5) spur, the 
projection on one of the sepals; (6) peduncle, 
the flower stalk. 
How many sepals are there? Are they all 
the same size and shape ? How many petals are 
there ? Are they all the same size and shape ? 
Have they all furrows, or streaks of color lead- 
ing to the base of the flower? If not, which 
ones have one or the other ? Which ones have a 
hairy fringe on the inside ? Do the hairs all point in the same direction ? 
Open the end of the spur and taste the liquid. Describe the taste. 
How many stamens are there? Draw one and label (1) filament, the 
slender, stalk-like part; (2) anther, the enlarged top which contains 
yellow, dust-like particles, the pollen. If possible, examine pollen 
grains with a microscope. Describe them. 
Figure 307. - Pistil 
and Stamen of Nas- 
turtium. 
1. A, 3-parted stigma; 
B, style; C, 3-parted 
ovary; D, receptacle ; 
E, peduncle. 
2. A, anther, with 
pollen ; B, filament. Charles Edwin Bessey was born in Milton Township, Wayne 
County, Ohio, May 21, 1845, and died at Lincoln, Nebraska, 
February 25, 1915. 
He was educated in the country schools and academy, and at 
the Michigan Agricultural College, from which he graduated in 
1869. In February, 1870, he began his duties as Professor of 
Botany at the Iowa State College at Ames, Iowa. In addition to 
botany, he taught zoology and entomology for the larger portion 
of the fifteen years that he remained at that institution. He as- 
sumed the professorship of botany at the University of Nebraska 
in November, 1884, a position held by him until his death. 
His greatest contributions to botany are: the introduction of 
the laboratory method in teaching the science; his enrichment 
of the whole field of botany by teaching many new aspects of the 
subject; and his profound influence upon students and future 
investigators. STRUCTURE OF THE LILY 
499 
Draw the pistil. Label (1) stigma, the top portion; (2) style, the 
slender part below the stigma; (3) ovary, the enlarged base. Examine 
the stigma with a hand lens. Does it appear sticky? Can you see 
pollen grains on it? Cut across the ovary. How many chambers has 
it? How many ovules (small, white bodies) are in each chamber? 
Draw and label. 
Examine a nasturtium blossom that has stood in water till it has 
withered. What parts of the flower have dried up? Which ones have 
fallen off? What parts remain? What changes have taken place in 
those that are left? 
Figure 308. - Long-spurred Blue Violet. 
All violets have an irregular corolla. 
SUGGESTIONS FOR HOME WORK 
Compare any blossoms you have at home with the nasturtium (ge- 
ranium is a good one). Do you see any indications of irregularity in 
the geranium? Of a spur? Of colors or furrows on the petals? Ex- 
amine other flowers in the same way - apple, violet, lilac, chickweed, 
etc. Make notes and sketches of what you find out for yourself, and 
of questions that occur to you. 
357. Structure of the Lily. - So important are these parts 
of the flower that it is well to review them in another flower, 
the lily. Here the pistil is the central organ and has three 
parts, (1) the expanded, sticky stigma at the top, (2) the style, 500 
FLOWERS AND FRUITS 
the long, slender connecting portion, and (3) the ovary, the 
expanded base. Inside the ovary are the ovules, which con- 
tain the egg cells from 
each of which an embryo 
plant will develop if it 
becomes fertilized. The 
part of the ovary to which 
the ovules are attached 
and through which they 
get their food is the 
placenta. The stamens are 
the parts of the flower 
outside of the pistil and 
surrounding it. Each 
stamen consists of a slen- 
der stalk, the filament, and 
an anther, the part which contains the pollen. Around the 
outside of the stamens and pistil are the colored parts which 
together form the perianth of the flower (Greek, peri, around, 
anthos, a flower). In the lily the perianth 
consists of six parts of the same color, 
size, and shape. Because of the even 
size and regular shape of the parts of the 
perianth of the lily, we speak of it as a 
regular flower. The perianth is an ac- 
cessory part of the flower, for seeds can 
be made without it, the stamens and 
the pistil being the only essential parts. 
LABORATORY STUDY OF A LILY 
Each pupil is to be provided with a lily. 
Draw the flower and label the parts as follows: 
(1) perianth, the large outer parts taken to- 
gether; (2) stamens, the slender parts bearing the yellow, dust-like 
pollen; (3) pistil, the central part of the flower; (4) peduncle, the 
flower stalk. 
A, divisions of perianth ; B, stamens ; 
C, pistil. 
Figure 309. -Flower of Lily. 
Figure 310.- Stamens. 
a, pollen shed by lifting 
of lid ; b, pollen shed 
through holes. FUNCTIONS OF THE PARTS OF A FLOWER 
501 
How many divisions has the perianth ? Are they all the same shape, 
size, and color? Have they all furrows or markings leading to the base 
of the flower ? Are there drops of nectar, a sweet substance, at the base 
of the stamens ? 
How many stamens are there? Draw one and label (1) filament, the 
stalk-like part; (2) anther, the enlarged top which bears the pollen. 
If possible, examine the pollen grains with a microscope. 
Draw the pistil and label (1) stigma, the enlarged upper end; (2) style, 
the slender portion below the stigma; (3) ovary, the enlarged base. How 
many lobes has the stigma ? Is it sticky ? Are there 
pollen grains upon it ? 
Cut across the ovary. How many chambers has it ? 
Are there few or many ovules (small, white bodies) in 
each? Draw. Label the parts to which the ovules 
are attached, placenta. 
Let a lily stand in water till it withers. What parts 
have dried up? What other changes have taken 
place? Cut across the ovary. Compare with your 
drawing and tell what differences you see. Draw the 
ovary as it now appears. 
358. Functions of the Parts of a Flower. 
- The sepals are adaptations for the protec- 
tion of the inner organs while they are de- 
veloping, and the petals are adaptations for 
the purpose of attracting insects to distribute 
pollen. Sometimes one set of these organs is lacking and 
sometimes the other. Very often, sepals are colored and 
serve the purpose of petals, another adaptation. The re- 
ceptacle serves as the place of attachment for the other parts 
of the flower. 
The stamens produce the pollen without which seed can- 
not be formed. Concerning the ways in which they open, 
the kind of pollen they bear, their adaptations for getting 
it to the pistil of another flower and (usually) for keeping 
it from its own, enough has been discovered to furnish text 
for a whole book, although many flowers have not yet been 
studied at all. Many of these facts can be observed by any 
Figure 311.- 
Stamen of Lily. 
A, anther ; B, 
pollen grains; 
C, filament. 502 
FLOWERS AND FRUITS 
boy or girl with keen eyes. To be on the lookout for new 
facts will give zest to the study of botany. 
In the ovary of the pistil are found the ovules which will 
become seeds under favorable conditions (see sections on 
Pollination and Fertilization). The stigma and the style 
are parts which help to fulfill these conditions. The position 
of the ovules in the ovary, the adaptations of the stigma 
for catching and holding pollen, the position of the stamens 
with reference to it, the adaptations of the pistil for the 
passage of the pollen tubes through it, - all these furnish 
the basis for a fascinating study which can be carried on by 
any one who has access to flowers, and who has time and 
patience. 
When a flower has finished its work, namely to secure the 
fertilization of the egg-cell in its ovules, its showy parts, if 
it had any, wither, and the fruit begins to form. Usually it 
is only the ovary which enters into the fruit; but in some 
cases, the receptacle is included. 
Examine vacant lots, waste spots, and gardens for weeds. How many 
of them are composites? See page 505. 
Study flowers in vacant lots, and record the results, using the follow- 
ing table as a guide. 
HOME WORK 
Corolla 
Regular 
Corolla 
Irregular 
Corolla 
Lacking 
Stamens only 
in a Flower 
Pistils only 
in a Flower 
Flower 
Perfect 
Geranium 
Castor bean 
Salvia . . 
Nasturtium 
Pansy . . 
etc. . . TYPES OF INFLORESCENCE 
503 
359. Types of Inflorescence. - This term is used for the 
act of flowering and for the arrangement of flowers on the 
A raceme in which the flowers 
have very short pedicels or none, 
as plantain, Figure 317. 
Figure 312. - Spike. 
Figure 313. - Staminate Flowers of 
Poplar. 
Catkins are a form of raceme. 
stalk. Flowers that grow at the end of a separate stalk, 
like the common blue violet, tulip, daffodil, water lily, and 
hepatica, are solitary flowers. As a rule, they are larger 504 
FLOWERS AND FRUITS 
and more showy than those which are arranged in clusters. 
It is not necessary to learn the types of inflorescence, but for 
those who are interested 
the following brief dis- 
cussion is given. 
Raceme. - This is a 
stem which bears flowers 
on both sides or spirally, 
each flower having a 
bract or reduced leaf at 
its base. The flowers 
may all hang from one 
side of the stem as in 
lily-of-the-valley or cur- 
rant. 
Umbel. - All p edicels 
arise around a central 
point, the outer ones be- 
ing longer. 
Thyrse. - This is a 
compact panicle forming 
an oval or pyramidal cluster, as bunch of grapes, lilac, 
horse-chestnut blossoms. 
Head. - This is a raceme in which the axis is very much 
flattened, or much rounded, as clover. 
Corymb. - This is an inflorescence in 
which the lower pedicels are longer, 
forming a flat-topped cluster, as haw- 
thorn. 
In a raceme, spike, panicle, and head, 
the axis may go on growing and producing 
flowers during an indefinite period. This 
is known as indeterminate inflorescence. In- 
determinate inflorescence has its oldest 
flowers on the lower part of the axis 
Figure 314. - Compound Umbel of 
Wild Parsnip. 
This form of inflorescence is a distin- 
guishing mark of a whole family of plants. 
Pistil 
Corolla 
A kene 
Figure 315. - Disc 
Flower of Daisy. POLLINATION 
505 
(raceme, spike, head) or on the outside of the cluster (corymb). 
The order of blossom- 
ing is centripetal. 
Composite Flowers. 
- This term is applied 
to flowers which are 
closely crowded or 
grouped into a head, 
on a common recep- 
tacle. Such is the 
dandelion or the daisy, 
each group being com- 
monly called a flower. 
Two kinds of flowers 
are to be found in these 
heads, tubular flowers, 
that is, with the corolla 
a tube, and strap- 
shaped flowers in which the corolla is long 
and slender. Some composite flowers, 
like the dandelion, have only the strap- 
shaped, and others, like the thistle, only 
the tubular kind Still others, like the 
common daisy and the sunflower, have 
both kinds. In the daisy, the tubular 
flowers, found only in the middle, are 
called disc flowers. These make up the 
yellow part of the group. Outside of 
them are the white, strap-shaped kind, 
known as the ray flowers. In the sun- 
flower the disc flowers are brown, and the 
ray flowers yellow. 
360. Pollination. - When insects go to 
a plant to get nectar, they are helped by 
adaptations of the flower to become 
region of 
ripe pistils 
Corolla 
-Pistil 
-Akene 
region 
oF ripe 
stamens 
Figure 316. - Ray 
Flower of Daisy. 
developing 
Fruit 
Figure 317. - Spike 
of Plantain, a Com- 
mon Weed. 506 
FLOWERS AND FRUITS 
covered with pollen as they leave the flower. Still other 
adaptations bring it about that when the insect enters a 
flower, some of the pollen from the flower last visited is 
left on the stigma of the one which it is entering. 
This pollination is only the first step in the production of 
seed. Before we can understand 
the use of pollination, we must 
understand the structure of the 
pollen grain which is a cell. 
Figure 319. - Flower 
of Columbine. 
Figure 318. - Flower of Calla. 
Showing spurred petals. 
Only a long-tongued insect 
can reach the nectar. Note 
the bunch of stamens upon 
which the insect alights. 
Both pistils and stamens grow on the 
spadix. This is inclosed by the white 
spathe, a modified leaf. Jack-in-the-Pulpit 
has spathe and spadix. 
Pollen grains present the greatest variety in size, structure, 
and markings, but all have some features in common. They 
all have a double coat or covering, the outer side of which is 
thin in places. When a pollen grain is caught on a sticky 
stigma, it soon sprouts; that is, the inner coat pushes out 
through the thin places in the outer coat, producing a tube. 
This contains the protoplasm of the pollen grain, and two 
nuclei, one of which, the sperm nucleus, will join with that POLLINATION 
507 
found in the ovule, the egg nucleus, to start the new plant 
formed in the seed from the fertilized 
ovule. 
The pollen tube and the style both 
show adaptations. The style is either 
tubular, affording a path for the pollen 
tube, or it is com- 
posed of cells very 
loosely packed, al- 
lowing the tube to 
pass through it 
readily. The adap- 
tations of the tube 
are its ability to 
absorb food from 
the tissues through 
which it passes, and to find the open- 
ing of the ovule. 
Cross-Pollination. - Pollen is neces- 
sary for the formation of seeds, and in 
most cases it is the pollen of 
some other plant of the same 
kind that is used. When 
the pollen of one flower is 
transferred to the stigma of 
another of the same kind, the 
process is known as cross- 
pollination. On the other 
hand, when a stigma gets 
pollen from the stamens of its 
own flowers it is said to be 
self-pollinated. 
The distribution of pollen 
is accomplished by insects and 
by wind more than by other 
Stigma 
\Pollen 
""Grain 
-Tube 
-Nucleus 
Loose Tissue 
of Stvle 
Figure 320. - Pollen 
Grains Sprouting and 
Growing through 
Style. 
Tube Nucleus 
Figure 321. - Pollen 
Grain Sprouted. 
The upper nuclei are 
male or generative 
nuclei. 
Figure 322. - Portion of Pollen 
Tube Dissolving Its Way 
through Loose Tissue of 
Style. 508 
FLOWERS AND FRUITS 
agents. Pollen that is to be scattered by wind has two 
adaptations: (1) it is very abundant, for much of it is sure 
to be lost; (2) it is light, that it may be easily carried. The 
pollen of pines, which is so abundant as to cause the so-called 
11 sulphur showers " in the spring, illustrates this, and the 
pollen of grasses, which 
is extremely light, illus- 
trates the other fact. 
Plants that are wind-pol- 
linated usually lack odor 
and color and floral en- 
velopes (accessory parts), 
but they have adapta- 
tions in the stigmas, 
which are either plumy 
or feathery or broad and 
sticky, the better to catch 
and hold the pollen grains 
brought to them by the 
wind. Seeds formed as 
a result of cross-pollina- 
tion produce a larger 
number of vigorous plants 
than those which grow 
from seeds in self-polli- 
nated flowers. 
Self-Pollination. - 
Some flowers, like the 
cleistogamous flowers of 
the violet, are arranged with a view to securing self-pollina- 
tion. Most flowers, on the other hand, have adaptations to 
prevent it. 
One of these devices is to produce pistillate flowers only 
on one tree and staminate flowers only on another tree or 
plant. The willow does this. A second adaptation is to 
Figure 323. - Flowers of Willow. 
"Willow pussies" are the staminate 
flowers in their early stage. FERTILIZATION 
509 
have the pistil mature first and the stamens last as the plan- 
tain does, or to have the stamens mature first and the pistils 
last as the dandelion does. A third is to have long stamens 
and a short pistil, or short stamens and a long pistil. When 
an insect visits such a flower, one part of its body is apt to 
come into contact with the stamens and another with the 
pistil. For example, in the primrose, an insect which gets 
pollen from short stamens on its body in one flower leaves it 
on the short stigma of 
another flower. 
Artificial Pollination. 
- In artificial pollina- 
tion, pollen from one 
flower is carefully trans- 
ferred by hand to the 
stigma of another flower 
of the same kind. Usu- 
ally this flower had its 
stamens removed before 
the pollen was ripe. It 
must be protected from 
the visits of insects after 
it has been pollinated 
artificially. 
Artificial pollination is 
practiced to develop new varieties of fruits (see page 11) 
and of cereals (see page 651). Luther Burbank has made 
use of this method in many of his experiments on fruits 
and flowers. 
It was formerly thought that cross-pollination was neces- 
sary to produce vigorous plants. Its chief value seems, 
however, to be to produce variations. 
361. Fertilization. - The union of the pollen nucleus with 
the nucleus of the egg cell is called fertilization. Without 
it, the ovule never develops into a seed. (Look in pea or 
Figure 324. - Staminate Flowers of Corn, 
the "Tassel." 
Corn is a wind-pollinated plant. 510 
FLOWERS AND FRUITS 
bean pods for unfertilized ovules; in the seed-case of an apple; 
on an ear of corn.) 
Successful fertilization depends much on thorough pollina- 
tion. For this reason farmers and gardeners should know 
the habits of the insects which pollinate flowers and the best 
way to plant certain 
crops to secure the re- 
sults desired. 
How Fertilization Is 
Accomplished. - When 
pollen grains fall on a 
stigma they are held 
there by a sticky sub- 
stance or by projections, 
and each soon puts forth 
a tube. These tubes 
make their way through 
the style. If the style 
has a channel, the tubes 
pass down the sides of 
that. If the style is filled 
with loose tissue, each 
tube makes a path for 
itself by dissolving and 
living upon the cells that 
are in its way. 
The nuclei are always 
near the end of the tube, 
which may become very 
long compared to the size of the grain which produced it. (See 
Figure 321.) When it reaches the ovary it turns towards an 
ovule, which it enters, usually through the micropylar opening. 
When the tip of the tube containing the male nucleus touches 
the egg cell in the embryo sac, it bursts, and its nucleus unites 
with that of the egg cell, completing the act of fertilization. 
Figure 325. - Pistillate Flowers of 
Corn. 
Each grain had a long green style, the 
"silk." Corn husks are modified leaves. FERTILIZATION 
511 
As soon as the egg cell is fertilized it begins to divide, form- 
ing the new plant. At . the same time other changes take 
place which result in the formation of a seed. (See page 506.) 
Figure 326.-Violet Plant with Cleistogamous Flowers. 
These look like buds, as they grow below the surface and never open. 
Their one or two stamens pollinate the pistil thoroughly. 
SUGGESTIONS FOR DEMONSTRATION BY TEACHER 
Direct the observations of pupils in studying the flowers of a dande- 
lion. Note old (mature) flowers on the outer part of the head, and 
young (immature) flowers in the inner part. Note the notches at the 
end of the long corolla. What does this indicate? Note the number 
of filaments, and the anthers united in a ring, opening on the inside. 
Call attention to the fact that the anthers mature before the pistil does. 
Show how the pistil, with its stigmatic surfaces pressed tightly together, 512 
FLOWERS AND FRUITS 
pushes up through the pollen which fills the tube, becoming covered on 
the outside. Show mature pistil with expanded stigma. If possible 
show dandelions with insects on them. What are the insects doing? 
What happens to the pollen? 
Pollen Grains. - Place a few, preferably large ones, on a slide; cover 
with 5 per cent sugar solution; put under a bell jar and set in a warm 
place for half an hour. Then add a cover glass and examine for pollen 
Stamens 
Pistil 
Stamens 
in position 
■for insect 
.to push 
lower part 
When pushed, -the stamens 
bend down dusting the 
insect with pollen 
Figure 327. - Flower of Salvia. 
A, whole flower. Note the platform where the insect alights 
tubes. Examinations may be repeated at intervals for a number of 
hours. 
Carefully split the style of a large flower, like a lily, noting the passage 
in the middle for the pollen tubes. If the pistil has not a tubular center, 
what is the character of the tissue in the center? 
362. Adaptations for Pollination. - The flower of the 
nasturtium offers a good example of adaptations. You will ADAPTATIONS FOR POLLINATION 
513 
notice that (1) it has a striking color m contrast with the 
foliage. This enables insects to see it readily. (2) It has 
an odor. This enables insects 
that are guided largely by the 
sense of smell to find it. (3) It 
has a long nectar spur on one 
side of the flower. This attracts 
the larger insects for the food 
they can get. (4) The lower 
petals have an inner fringe 
which retards the crawling in- 
sects that are trying to get the 
nectar. (5) The upper petals 
project over the other parts of 
the flower. This keeps the rain 
from running down the nectar 
spur and prevents the pollen 
from becoming wet. (6) The 
lower petals have stripes that 
lead to the opening of the nectar 
spur. This indicates the direc- 
tion that insects should travel 
to find the opening quickly. 
(7) The anthers mature at dif- 
ferent times. This insures a 
supply of pollen on different days 
so that some of the pollen is in 
condition to use, even if some 
has been spoiled by unfavorable 
weather. (8) The anthers and 
stigma mature at different times 
so that the pollen cannot get 
on its own stigma. There are at least eight ways in which 
the nasturtium flower is adapted to the visits of insects and 
to the protection of its pollen and nectar. There are many 
Figure 328. - Flower of 
Dandelion. 
A, strap-shaped corolla; B, 
stigmatic surface covered with 
pollen; C, style covered with 
pollen from its own anthers; D, 
ring of united anthers; E, fila- 
ments of united anthers ; F, pap- 
pus ; G, akene, young fruit. 514 
FLOWERS AND FRUITS 
other aspects of the study of flowers as interesting as the 
study of adaptation, some of which will be mentioned later. 
Let us see what adaptations the lily has. (1) It is a large 
showy flower. Insects can see it easily. (2) It has a strong 
odor, enabling insects to locate it by smell. (3) It has a long 
pistil which protrudes beyond the other parts, affording a 
good place for insects to alight. (4) It has long stamens so 
arranged that when an 
insect alights on the pis- 
til, it is sure to become 
dusted with the pollen 
from them. (5) Its pistil 
has a sticky enlarged 
end which is almost sure 
to catch pollen grains 
from the insect's body. 
(6) It has nectar glands 
around the bases of the 
stamens which yield food 
for the insects. (7) It 
has furrows in the petals 
leading to the nectar 
glands. This helps the 
insect to find the nectar. 
(8) The stamens bear 
the pollen on their outer 
surfaces, a safeguard against self-pollination. (See page 508.) 
Dandelion flowers show many adaptations. The stamens 
are joined in a tube with the anthers opening on the inside. 
The anthers mature their pollen before the pistil of that 
flower is ready for pollen. The pistil, with its stigmatic 
surfaces pressed tightly together, pushes up through the mass 
of pollen filling the tube, becoming covered on the outside. 
Insects crawling over the head drag some of these pollen 
grains to pistils which are mature. When the pistil of 
Figure 329. - Lady-slippers. This beautiful plant is in danger of becoming extinct through ruthless 
picking. 
Wild Moccasin Flower. ADAPTATIONS FOR POLLINATION 
515 
any one flower expands, its own pollen is not likely to get 
on it. 
The closely crowded flowers, the arrangement of their 
parts, the bright color, the abundant pollen, and the certainty 
of cross-pollination are adaptations which make the dandelion 
one of the most successful of plants. 
The composites as a whole show more adaptations than 
Figure 330.--Pink Lady-slippers. 
One of the disappearing orchids. In many places incessant picking has 
exterminated it. It is doomed to extermination unless the boys and girls 
start a crusade to save it from the older men and women who are old- 
fashioned in their way of appreciating wild flowers. Orchids are perennials, 
but they need their leaves to store up food for next year's blossoms and seeds. 
Naturally they fruit every year, and the older plants are surrounded by little 
groups of seedlings, which is nature's way of stocking the woods with these 
delightful flowers. Every one that is picked and brought in tends to make 
the woodland barren and so much less attractive. Spare the wild flowers! 516 
FLOWERS AND FRUITS 
other flowers, so we find among them those which are of most 
interest to the scientist and those which are of greatest an- 
noyance to the farmer, namely, dandelion, paint-brush, 
Figure 331. - A Rare Orchid. 
burdock, and thistles of all kinds. They are most success- 
fully fought by not giving them opportunity to blossom and 
form fruit. 
363. Conservation of Wild Flowering Plants. - It would 
be a poor course in biology that did not emphasize the pleas- CONSERVATION OF WILD FLOWERING PLANTS 
517 
ure which knowing our wild flowers gives all lovers of nature. 
We are coming to feel that animals and plants which give 
us pleasure should be permitted to live. 
Game laws and animal preserves are 
helping to protect some of our rare animals 
that were being de- 
stroyed by man. 
For twenty years 
flower protection or- 
ganizations have been 
urging that the rarer 
wild flowers should be 
protected by law. Dur- 
ing the year of 1923 sev- 
eral states passed laws 
against the indiscrimi- 
nate picking of wild 
flowers. You should do 
your part in helping to 
make this new legislation effective. 
Owing to the limited area of wild tracts, 
particularly near cities, wild flowers will 
soon disappear utterly unless the public 
is educated to enjoy them as they grow. The study of 
plants which you have just 
made tells you about their 
habits so that you may know 
how to deal with them. For 
instance, little harm is done 
by picking the flowers of tril- 
lium, because its thickened 
stem, deep in the ground, 
will put up another flower 
stalk the next year, if it has 
food enough stored to enable 
Figure 332. - De- 
hiscent Capsule of 
Poppy. 
Note the openings 
through which the 
seeds sift. 
Figure 333. - Dry 
Fruit of Dande- 
lion, the Akene. 
Figure 334. - Explosive Capsule 
of Violet. 518 
FLOWERS AND FRUITS 
Figure 336.- Chestnut, a Dry Fruit. 
A, remains of staminate flowers ; B, nuts ; 
C, bur. 
Figure 335. - Dry Fruits. 
1. Beechnut. The seed 
is inclosed in the pericarp 
and the whole sur- 
rounded by the bur (5), 
which was formed from 
the involucre. 
2. Acorn. C, cup formed 
from involucre; D, seed 
inclosed in pericarp. 
it to do so. In the case of arbutus, 
however, it is difficult to pick the 
blossoms without pulling loose from 
the soil the long trailing stem, which 
is then left to die. Picking the 
flowers of dogwood destroys the at- 
tractiveness of this shrub. The 
orchid is another species of wild flower that is rapidly dis- 
appearing because people are incessantly picking it. In 
many places it has been 
nearly exterminated. 
In your study of the 
flower, you have learned 
that the seeds are de- 
veloped in the flower, 
and if you pick all the 
flowers no seeds can be 
formed. Lovers of wild 
flowers are coming more 
and more to enjoy leav- 
ing them where they 
-skin 
oil glands 
PulP 
seeds 
'•-vascular 
bundles 
Figure 337. - Cross Section of Orange, TYPES OF FRUITS 
519 
grow instead of picking them for 
decorating their homes, where 
they last for only a few hours at 
best. 
Photographing wild flowers 
where they are found growing is 
a form of recreation that is be- 
coming popular. 
364. Types of Fruits. - The 
fruit of a plant is the final result 
of the work of the flower. In its 
simplest form it is the ripened 
ovary and its contents, including 
the seed or seeds. In some cases, 
however, it involves accessory 
parts of the flower as well, es- 
pecially the receptacle. The wall 
of the ovary in a fruit is called 
the pericarp. 
Fruits are either fleshy: berry, 
drupe, (stone fruit), or dry. 
Dry fruits are of two kinds, 
(1) those that open (dehiscent), 
bean, poppy, and violet; and (2) 
those that do not (indehiscent), nuts, corn, samara of maple. 
A grain of corn or 
wheat is a typical inde- 
hiscent fruit. The peri- 
carp, though very thin, 
is hard and flinty, fur- 
nishing effective protec- 
tion to the inclosed em- 
bryo and food. 
Function. - The fruit 
is of use to a plant in 
sepals 
•vascular 
bundles 
vascular 
bundles 
■vascular 
bundles 
1. The stem end attached to 
the orange. 
2. Under side of stem end. 
3. Pit in orange after re- 
moval of remains of stem. 
Figure 338. 
Figure 339. - Samara of Maple. 
A dry, indehiscent fruit. 520 
FLOWERS AND FRUITS 
two ways, (1) in protecting the seeds during their develop- 
ment, as in the bean, or during their period of dormancy, as 
in the nut, and (2) in 
helping to distribute the 
seeds after they are ma- 
tured, as in the burdock. 
The fruit of most plants 
is the part that is of 
greatest use to man, fur- 
nishing him most of the 
necessities in the way of 
food, and many of the 
luxuries. 
LABORATORY STUDY 
Study of an Orange. - Ex- 
amine the stem end and note 
the remains of the calyx. How 
many sepals had the flower? 
Remove it. How many dots 
do you see? These represent 
the ends of the vascular bundles which supplied food to the growing 
fruit. Examine the opposite end for scar showing where the pistil 
was attached. Scrape the skin or pinch it, and note the oil which 
shows as a yellow, odorous 
liquid. 
Note. Placeadropofthis 
oil on linen paper. Note the 
spot it leaves. After a day 
examine the paper. Is the 
spot still visible? Oils that 
evaporate, leaving no spot, 
are called volatile or essential 
oils. Place peanut, Brazil 
nut, or castor bean on a linen 
paper. Heat till a clear spot 
shows. Lay aside and ex- 
amine from time to time. Does the spot disappear ? Oils that do not 
evaporate are known as true oils. 
remains of pistils 
remains oF 
( stamens 
'.-sepal 
^-Fleshy wall 
of receptacle 
developing 
seeds 
Figure 340. - Diagram of Fruit of 
Rose. 
Figure 341. - Cross Section of 
Cucumber. 
A fleshy fruit. STUDY OF AN APPLE 
521 
Make a cross section through the middle of the orange. How many 
distinct parts are there ? Where are the seeds ? Note the oil glands in 
the cut skin. Draw and label the 
parts named above. 
Remove the skin from a whole 
orange and separate the parts. 
How many are there ? Look for a 
strand of conductive tissue on each 
one. Where do they come from? 
Compare the number of sections 
with the number of vascular 
bundles on the stem end. 
Study of a Tomato. - Examine 
the whole fruit for traces of parts 
of the flower. On which end are they found? How many sepals 
were there in the flower? Remove the stem and count the number 
of vascular bundles. Make a cross section through the middle. How 
many divisions in the tomato? Where are the seeds? Note the 
mucilage with which each is surrounded. Can you see the vascular 
bundle which entered it ? Note 
the very thin skin. Draw and 
label all. The tomato is a 
berry. 
Note. Canned, unpeeled 
tomatoes will serve. Com- 
pare grape, another berry, 
and peach, plum or cherry, 
drupes. 
Study of an Apple. - Ex- 
amine the whole apple. On 
the blossom end find the old 
sepals. How many? In the 
end of the stem look for vas- 
cular bundles. Draw and 
label. Make a cross section 
through the middle. Draw. 
Label the seeds in the papery 
pod (core). How many divisions has it? How many vascular bundles, 
as shown by dots near the core? 
Make a vertical section. Label vascular bundles when seen, stem, 
Cut Ends of Vascular Bundles 
Figure 342. - Cross Section of 
Apple. 
Fleshy Wall of Receptacle 
Vascular Bundles 
Seed 
I Seed Pod 
'or Core 
Figure 343.-Vertical Section of 
Apple, a Pome. 
Remains of Calyx 
Other pomes are quince and pear. 
The thickened receptacle becomes con- 
solidated with the pericarp. The papery 
endocarp is the core. The fruit of the 
rose, Figure 340, shows the relation of 
parts. 522 
FLOWERS AND FRUITS 
fleshy wall of receptacle, and remains of sepals. Are the remains of 
sepals on the same end in the apple as in the orange? 
HOME WORK 
Draw a pod of bean or pea showing valves, seeds, remains of sepals, 
and place where pistil was attached. Examine fruit of dandelion, milk- 
weed, and other weeds as you find them. 
See how many kinds of fruits you can 
find. Make a list of fruits obtained. 
365. Adaptations of Fruits and 
Seeds for Dispersal. - Before 
any fruit has fulfilled its function, 
it must scatter the seeds it con- 
tains. This is necessary for three 
reasons, at least. (1) There 
would be too much competition 
if all were dropped near together ; 
(2) there would be too slow prog- 
ress, for the soil near the parent 
might be depleted, and the new 
plants could 
not grow as 
well there as 
in fresher soil; 
and (3) there would be too great a chance 
of extermination if all were dropped near 
together, for some one unfavorable con- 
dition might kill them all. 
In order to scatter seeds a plant makes 
use of wind, animals, and water as dis- 
tributing agents, and of such mechanical 
devices as exploding pods. To be dis- 
tributed by the wind, a seed or a fruit must be light. This 
is brought about in some plants by plumes, as in the case of 
the akene of the dandelion, thistle, and clematis, by the down 
Figure 344. - Clotbur or 
COCKLEBUR. 
This is both hooked and buoyant. 
Figure 345. - Fruit 
of Wild Carrot. 
This is distributed 
by wind and by ani- 
mals. ADAPTATIONS OF FRUITS AND SEEDS 
523 
on a milkweed seed, and by the wings on the fruits of the 
maple and elm. (Review § 17.) Special devices for wind 
distribution are found in the Rus- 
sian thistle and in tickle-grass, 
a common garden weed. In the 
former case the whole plant breaks 
off at the level of the ground, and 
is blown about by the wind, fruits 
and seeds being broken off and 
scattered as it rolls along the 
ground. This is one of the worst 
weeds of sections of the western 
states. In tickle-grass, only the 
panicle is broken off, but the re- 
sult is the same. 
To be carried by animals, the 
adaptations may be of two kinds 
- either they must have hooks 
to catch on or they must be edible. 
The burdock and beggar's tick rep- 
resent the first kind of adaptation, 
and the fleshy 
fruits the sec- 
ond. In some 
cases only the 
fruit is eaten, as with peach, plum, etc., 
and the seeds dropped ; and in other cases 
the seeds and all are eaten, but are not 
acted upon in the digestive tract, and so 
are dropped far from the spot where they 
grew, as with berries, apples, pears, etc. 
(Review § 147.) 
To be carried by water, the adaptations 
must be such as will insure buoyancy and the ability to with- 
stand decay. Both are well illustrated by the coconut, and 
Figure 346. - Fruit of Avens. 
' Beggar's tick." 
Figure 347.- Fruit 
of Hound's Tonoue. 524 
FLOWERS AND FRUITS 
the former by the cocklebur. To be distributed by being 
forcibly expelled, the fruits must have elastic tissue. The 
jewel-weed or touch-me-not illustrates this, as does witch- 
hazel, wild cucumber, and violet. 
Besides the distribution of seeds by means of scattering 
the fruit or the seeds, plants have other means of propagating 
themselves which will be spoken of as they occur. The 
main dependence for keeping up the race, however, in most 
plants, especially the wild ones, is the 
distribution of its seeds. The fruit of 
a plant, so far as its relation to the 
plant that bore it is concerned, is 
simply a device for securing the dis- 
tribution of the seeds it contains. 
Dry fruits show many adaptations, 
most of which are based on some 
peculiarity of the pod. Take the 
bean for example. The pod is elastic. 
When it dries this causes it to split, 
then to curl up, throwing the seeds 
out by force. A pod which has elastic 
tissue is the wild cucumber which 
forces its seeds out violently. Still an- 
other is the witch-hazel. A pod which 
explodes violently is that of the jewel-weed, which requires 
only a touch to set it off, scattering the seeds far and near. 
A capsule differs from a pod chiefly in having more than 
one chamber in immature stages. A capsule usually splits 
in several places, one for each chamber of the ovary, an 
adaptation for releasing all the seeds. 
The adaptations of fleshy fruits are (1) a sour or bitter 
taste during development. This prevents their being eaten 
before the seeds are mature. (2) Edibility when ripe. This 
insures their being eaten by some animal, sometimes with- 
out the seeds, which are likely to be dropped some distance 
Figure 348 -Fruit of 
White Mustard 
A modified pod. ECONOMIC VALVE OF FLOWERS AND FRUITS 
525 
from the plant which produced them; or seeds and all, in 
which case the undigested seeds are passed off with other 
wastes, often very far from the parent plant. 
366. Economic Value of Flowers and Fruits. - Many 
plants are cultivated for the pleasure their flowers give us. 
Cauliflower, the buds of which are used as food, is the 
most familiar example of the use of flowers for this purpose. 
A few have been used for medicine, though not so many 
now as formerly. Among them may be mentioned dande- 
lion, the elder, the mullein, and camomile. 
Saffron, a yellow coloring matter, is obtained from the 
stigmas of the saffron crocus. 
As soon as flowers appear observe them closely and note which have 
many insect visitors and which have few or none. Fill out a report as 
suggested below and add any points which interest you besides those 
mentioned. 
SUGGESTIONS FOR HOME WORK 
Color Conspicuous 
Color Not Conspicuous 
Odor Strong 
Odor Not Strong 
Nectar Abundant 
Nectar Not Abundant 
Insects Many 
Insects Few 
Etc. 
Sweet Pea. . 
Dandelion. . 
Hepatica . . 
Buttercup. . 
Examine florists' and gardeners' catalogues, and note the plants the 
flowers of which are used as food and for ornament. Read about the 
use of hops and the process of raising and harvesting them. 
The Uses of Fruits to Man. - In speaking of the uses 
of fruits to man, it must be remembered that all the grains 526 
FLOWERS AND FRUITS 
are fruits and that many so-called vegetables are fruits, 
as the tomato, and squash, and the cucumber. 
The most valuable source of food in the world is found 
in the cereals : wheat, oats, rye, rice, 
barley, and others. Nearly half of 
the population of the globe depends 
on rice for its principal food. Rice is 
the only one of the cereals that is 
commonly eaten entire. The others 
are usually ground and made into 
bread. The importance of bread as 
an article of food is shown by the 
term, " the staff of life," which is 
often applied to it. In the famine- 
stricken regions during the late war, 
the hungry cried for bread more 
than for any other article of food. 
A diet consisting of bread and nuts 
furnishes all the elements of food. 
Not only are the cereals the most 
important article of food, but they 
are the basis of a great part of the 
world's work. The raising of cereals, 
their preparation for food, and their 
distribution give employment to a 
greater number of persons than any 
other industry. Much more atten- 
tion is now given to agricultural 
education than formerly, because 
agriculture as an industry is now 
better appreciated. Besides supply- 
ing man with food directly, many 
cereals are used to feed the animals which he raises for the 
meat, milk, butter, cheese, and eggs which they produce. 
Man's beasts of burden live largely upon cereals too. 
Figure 349. - Cattails. 
The slender tip was once 
covered with staminate 
flowers. The brown " cat- 
tail " is made up of fruits, 
adapted to distribution by 
the wind. ECONOMIC VALUE OF FLOWERS AND FRUITS 
527 
The articles of food commonly known as fruits, - apples, 
oranges, berries, bananas, and others, - are valuable, their 
chief use being to supply variety to the diet. The fruits 
obtained from the vegetable garden, - tomatoes, cucumbers, 
squashes egg-plant, melons, and others, - furnish some 
foodstuffs. 
Uses of the Terms Fruit, Seeds, etc. - It will be evident 
by this time that the words fruit, seeds, and nuts have a 
different meaning in botany from their ordinary use. The 
term " seed corn " and " seed wheat " used by farmers is 
correct in the sense that it indicates the corn or the wheat 
which is planted or sowed to produce a new crop. The so- 
called Brazil nut of commerce is in reality a seed. The fig 
is a " fruit " composed of a thickened and hollow receptacle, 
the end of a branch, on the inside of which are produced the 
real fruits commonly known as seeds. 
HOME WORK 
Cereals. - What articles of food on your breakfast table were cereals? 
Where were they raised? How were they brought to your home? 
What kinds of food were furnished by each? Look up the population of 
China, India, and Japan for the year 1915 or later. Most of these 
people live chiefly on rice. How does that compare with the number 
in the northern countries of Europe and the United States who live 
largely on the other cereals ? 
Fruits. -The raising of fruit is one of the large industries of the United 
States. The Great Lakes region, especially the shores of Lakes Erie and 
Ontario, are famous for grapes, apples, peaches, plums, and cherries. 
California produces large crops of oranges, grape fruit, lemons, prunes, 
figs, and grapes. Florida has long been noted for its oranges and grape 
fruit. Oregon, Washington, and Virginia produce large crops of apples. 
Each kind of fruit requires a special kind of soil and certain conditions 
of climate, and each has certain kinds of enemies. Look up the enemies 
of the apple tree. How is each combated? How does the life history 
of the codling moth differ in eastern states and the western states 
(Oregon and New York) ? How is danger from frost avoided in Florida 
and California ? How is moisture supplied in Oregon and Washington ? 528 
FLOWERS AND FRUITS 
What kinds of birds are especially helpful in orchards ? Why ? What 
insect is helpful in the orange groves of California? Learn the history 
of it in this country. 
What are the advantages of dynamiting the soil in setting out trees? 
How was the loganberry produced? How does grape juice differ from 
wine? Why is it necessary to prune vines and trees? Look up the 
history of grape fruit. How do navel oranges differ from others? 
Look up the history of navel oranges. 
OUTLINE 
Structure of flowers 
Sepals 
Calyx 
Petals 
Corolla 
Stamen 
Filament 
Anther 
Pistil 
Stigma 
Style 
Ovary 
Ovules 
Placenta 
Functions 
Sepals 
Protection 
Petals 
Attraction 
Stamens 
Pollen 
Pistil 
Ovary 
Fertilization 
Inflorescence 
Raceme 
Compound 
Head 
Thyrse 
Corymb 
Composite flowers 
Tubular 
Strap-shaped 
Disc 
Ray 
Pollination 
Sperm nucleus 
Egg nucleus 
Cross-pollination 
Self-pollination 
Artificial pollination 
Fertilization 
Pollen 
Tube 
Style 
Nuclei 
Stigma 
Ovary 
Ovule 
Adaptations 
Color 
Odor 
Nectar 
Protection 
From insects 
From rain 
Conservation 
Arbutus 
Dogwood 
Orchids QUESTIONS 
529 
Types of fruits 
Fleshy 
Dry 
Dehiscent 
Bean 
Poppy 
Indehiscent 
Nuts 
Corn 
Function 
Protection 
Distribution 
Adaptations for dispersal 
By wind 
Thistle 
By animals 
Hooks 
Burdock 
Edibility 
Peach 
By water 
Coconut 
Economic value 
Food 
Pleasure 
Medicine 
Coloring 
Flowers are the organs of the plant which provide for the production 
of seed and the continuance of the race. The pistils and the stamens 
are the essential parts of the flower. Colors, odors, and nectar are 
devices for attracting insects which bring about cross-pollination. 
Wind-pollinated flowers are usually inconspicuous, and they have an 
abundance of light pollen. The pollen grain is a cell which contains the 
sperm nucleus. This is carried to the egg cell in the ovule by a tube. 
The union of the two nuclei of these cells is fertilization. The fertilized 
egg cell develops into an embryo plant and the ovule develops into a 
seed which protects the embryo and contains food for its early life. 
The fruit contains the seeds. It develops from the ovary of the 
flower. Its function is to secure the dispersal of the seeds. Some 
fruits are dry and some fleshy. Some of the dry fruits split open and 
some do not. Fruits are distributed by animals, by wind, and by water, 
and each kind has special adaptations to accomplish its end. Dispersal 
is necessary to give the new plants a better chance to grow. Fruits are 
of the greatest use to man as food. In many cases the quantity and the 
quality of the fruit man uses have been improved. 
SUMMARY 
QUESTIONS 
What is the function of flowers? What are the essential organs of a 
flower? What devices have flowers for attracting insects? What for 
wind pollination? What is the pollen grain? The ovule? What is 
fertilization? In what does it result? What is a fruit? What pur- 530 
FLOWERS AND FRUITS 
pose does it serve? How? What kinds of fruit are there? Describe 
a grape; a peach; a raspberry. What use is the fruit to man ? How 
are fruits distributed? Why is dispersal necessary? 
Bessey, College Botany, page 285; pages 302-313; 321-324. 
Snyder, General Science, pages 200, 201. 
Bergen, Foundations of Botany, pages 186-216. 
Conn, Biology, page 118. 
Bergen and Caldwell, Practical Botany, pages 104-135. 
Gibson, Sharp Eyes, page 115. 
Coulter, Plant Life and Plant Uses, page 58; pages 258-321. 
REFERENCES CHAPTER XXXI 
SEEDS AND GERMINATION 
Read my little fable 
He that runs may read 
Most can raise the flowers now 
For all have got the seed. 
- Tennyson 
367. The Bean from Ovule to Seed. - At the time of fer- 
tilization, an ovule of the bean consists of a mass of tissue 
(nucellus) in which is embedded the embryo sac. The em- 
bryo sac contains an egg cell which, if fertilized by a nucleus 
from the pollen tube, will become a 
young bean plant (embryo). The 
ovule is covered by two coats (in- 
teguments') which do not quite meet 
at one end, leaving an opening, the 
micropyle (mi'kro-pil: Greek, micro, 
small; pyle, gate), a small door 
through which the pollen tube usu- 
ally enters. It is attached to the 
wall of the ovary by a stalk through 
which it gets its nourishment. 
In developing into a seed several 
changes occur. (1) The coverings 
(integuments) become firm and hard, the outer forming 
the testa. (2) The egg cell divides many times, forming the 
embryo. (3) The embryo sac is replaced by two cotyledons 
which contain food for the embryo. (4) The micropyle 
becomes smaller and almost closes. (5) The stalk drops off, 
Raphe- 
\ Hilum 
Micropyle'' 
Plumule,^ 
^Hypocotyl 
-Testa 
Cotyledon 
Figure 350. - Bean Seed, 
Showing Parts. 
531 532 
SEEDS AND GERMINATION 
leaving a scar on the 
bean seed, the hilum 
(hi'lum : Latin, hilum, a 
little body). 
368. Adaptations of the 
Seed. - The bean seed 
is the plant's way of pro- 
viding for a new bean 
plant. It is adapted to 
fulfill that purpose in the 
following ways. (1) A 
ripe seed contains a 
young plant well started. 
(2) It can resume growth 
soon after being formed, 
or it can remain dormant 
for years. This might 
prevent total loss of seed. (3) It is surrounded by a hard 
testa which prevents the embryo from 
drying out during a long resting period. 
This enables it to re- 
main viable (Latin, vita, 
life) for many years. 
(4) It can absorb water 
slowly through the mi- 
cropyle when covered 
with moist earth. This 
softens the testa and 
causes the cotyledons to swell, helping 
to release the embryo. (5) The cotyle- 
dons contain food for the young plant 
till it can make its own. This insures 
rapid growth in the early stages, an 
advantage in competition with other 
seedlings. 
Figure 351. - Seeds of Bean and Pea. 
Upper, split, showing embryo. (Only 
the part showing the embryo was saved.) 
Lower, whole, showing markings. A, em- 
bryo ; B, plumule ; C, root; D, hilum ; 
E, micropyle ; E, embryo ; G, hilum ; 
H, micropyle. 
f-Food 
Scutellum 
-Embryo 
I-Plumule 
Figure 352. - Un- 
sprouted Grain of 
Corn. 
-Root 
Figure 353. Flu- 
•mule Ready to 
Break Out 
Root free and grow- 
ing downward. GROWTH OF THE BEAN EMBRYO 
533 
369. Growth of the Bean Embryo. - When the embryo 
resumes growth after a resting period, the root breaks out 
of the testa first. This is an adaptation, for it at once be- 
gins to absorb water needed for further growth and soon 
becomes firmly embedded in the soil. This primary root is 
followed later by secondary roots. 
The second adaptation is the curving of the hypocotyl 
(hy-pd-kbt''l: Greek, hypo, beneath ; kotyle, cavity). This 
Leaves 
^Bud 
Cotyledons 
Ground Line 
Hypocotyl - 
-Bud 
.Cotyledons 
Root 
- Root 
Root / 
Figure 354.- Growth of Bean Plant. 
Left, root free; center, root branched, hypocotyl developed and showing 
the arch ; cotyledons spreading, plumule showing ; right, young bean plant. 
Note the shriveled cotyledons and the first true leaves. 
forms a loop on top of which is a hard portion, the peg. 
The hypocotyl grows rapidly, causing the arch of the loop 
to turn from side to side, pushing the particles of soil apart 
and working its way to the surface. Then the cotyledons 
are pulled up as the arch straightens. Finally, further 
growth of the hypocotyl causes the cotyledons to spread 
apart, exposing the plumule (plum'ul: Latin, plumula, 534 
SEEDS AND GERMINATION 
feather) to the air and light. At the same time the cotyle- 
dons begin to turn green, thus serving as leaves till the leaves 
of the plumule have developed. 
So the plumule is protected and 
given a chance to grow under 
good conditions. As soon as the 
food in the cotyledons is ab- 
sorbed by the young plant, they 
shrivel and drop off, while the 
leaf-stem and leaves continue to 
grow. The young bean plant is 
known as a seedling while it is 
dependent on the store of food 
in the seed. 
In the course of a few weeks a 
bean plant is large enough to 
produce blos- 
soms which 
develop into 
pods contain- 
ing seeds, 
thus completing the life cycle. The use 
of the seeds to the plant is simply to 
provide for other plants of the same kind, 
and to insure a supply of food for the 
early life of each. Man, however, has 
learned to take advantage of this habit 
of plants, to secure food for himself and 
his animals. He has also found ways of 
enabling the plant under cultivation to 
store up more food than it could do in 
the natural state. 
370. Corn " Seed." - A grain or kernel 
of corn, commonly called a seed, is like a 
bean (1) in containing a young plant, the 
Figure 355. -Diagram of 
Grain of Corn. 
A, hard outer covering; B, pro- 
tein layer ; C, scutellum ; D, plu- 
mule of embryo ; E, hypocotyl; 
F, root; G, conducting vessels 
of scutellum ; H, place of attach- 
ment ; I, digestive cells of scutel- 
lum ; J, K, starch (endosperm). 
Plumule 
-Root 
Figure 356. - Plu- 
MULE Free but Bent 
by Accident CORN "SEED" 
535 
corn embryo; (2) in containing food for the use of the 
embryo when it first begins to grow; and (3) in having 
marks upon it. On one side of the kernel is a depression 
beneath which the embryo lies. Above the depression on 
each kernel is a slight prominence, the 
scar which marks the place where one 
thread of the so-called silks was at- 
tached. This is more prominent in pop 
corn. At the base is a stalk by which 
the kernel is attached to the cob during 
its development (Figure 355). Corn 
differs from the bean in the position of 
its embryo, which is at one side of the 
food supply. The latter is called the 
endosperm (en'do-sperm: Greek, endo, 
within ; sperma, a seed). Another differ- 
ence between the two is that the corn 
has a single modified cotyledon called 
the scutellum (sku-t61'lum: Latin, di- 
minutive of scutum, a shield), the use of 
which is to absorb and digest the food 
and carry it to the embryo (Figure 355). 
The cotyledon of the corn never appears 
above ground. The corn embryo has its 
leaves rolled into a tight, pointed bud, 
an adaptation which enables it easily to 
pierce the earth above. The root is at 
the lower part of a short hypocotyl. 
As the corn has but one cotyledon, it 
belongs to the class of plants known as 
monocotyledons (mSn-o-kbt-y-le'dbn: Greek, mono, one; 
kotyledon, socket). The bean, having two cotyledons, belongs 
to the class dicotyledons (di-kdt-y-le'don: Greek, di, two; 
kotyledon, socket). Review characteristics of these classes, 
page 466. 
^Leaves 
Prop 
'Roots 
Secondary 
^Roots 
Primary 
- Root 
Figure 357. - Plu- 
mule Unfolded. 
Root system devel- 
oping. Compare with 
Figure 358. 536 
SEEDS AND GERMINATION 
LABORATORY STUDY OF BEAN 
Draw a bean in an upright position, holding 
the side towards you that has the hilum (a 
mark) on it. Label hilum. Near one end 
of the hilum is a small dot, the micropyle. 
Around the outside of bean, lengthwise, is a 
band or ridge, the raphe, ending at the hilum. 
Label micropyle and raphe. Split a soaked 
bean along the back. Draw the two parts. 
Label them cotyledons. On one of them is 
the embryo or young plant. Draw and label: 
(1) the pair of small, white leaves, the plumule 
or seed bud of the new plant; (2) the hypo- 
cotyl, below the plumule, from which stem and 
roots will grow; (3) testa, the hard covering. 
Note. - Beans for class work should be 
soaked overnight at room temperature or for 
two hours in warm water. 
^Leaves 
Prop 
Roots 
LABORATORY STUDY OF CORN 
Draw a grain of corn, broad end up, with 
the side showing the depression towards you. 
Label (1) silk scar on one side of top; (2) scu- 
tellum (under depression); (3) stalk by which 
it was attached to the cob (hilum?'). 
Cut lengthwise a kernel that has been 
soaked for half a day. Label (1) embryo, 
young plant; (2) scutellum (cotyledon) lying 
under embryo; (3) endosperm, store of food 
on which scutellum rests; (4) hard outer 
covering. Cut a kernel crosswise. Draw it, 
and label the parts as above. 
Remove the embryo. Draw. Label plu- 
mule and root. Remove the scutellum. 
Draw. 
371. Kinds of Foodstuffs Found in 
Seeds. - In the bean seed, two kinds 
of foodstuffs are stored, namely carbo- 
hydrates and proteins. Carbohydrate 
\Primary 
Root 
-Secondary 
\ Root ' 
-Rootlets 
Figure 358. - Advanced 
Corn Seedling. KINDS OF FOODSTUFFS FOUND IN SEEDS 
537 
(see page 39) is the name of the foodstuff which includes the 
starches and the sugars. Protein (see page 28) is the name 
given to the foodstuff found in such foods as lean meat, 
cheese, and the white of egg. Beans contain more protein 
than any other seeds. 
Corn contains starch, sugar, and oil. Flaxseed and castor 
beans contain much oil. 
LABORATORY WORK 
Foodstuffs in the Bean. - The presence of different kinds of food- 
stuffs may be shown by applying the following (chemical) tests. Boil 
beans until they are soft and then place a small portion of them in a 
test tube. Add water and heat. Put in a drop of iodine. If starch 
is present, the mixture will turn blue in color. Add strong nitric acid 
to a second portion in a clean test tube, boil and cool. If protein is 
present, the mixture will be a clear yellow color which will become 
orange if ammonia is added. To a third portion add Fehling's solution1 
as a test for sugar. If the latter is present, the mixture will become 
dull orange when heated. Test uncooked seed for oil (1) by heating 
it over a lamp on a sheet of linen paper; (2) by soaking it overnight in 
ether. (This must not be near a flame at any time.) If oil is present, 
it will show on the paper as a clear spot, and in the second test the oil 
will appear on the surface of the ether in the test tube. 
To Show that Seeds Contain Water. - Weigh some squash seeds 
very carefully after they have been peeled. Place them in a thin dish 
over a hot radiator for a few hours, then weigh again. Repeat the 
experiment, using other fleshy seeds. What do you learn from this 
experiment about the use of the testa to a seed? 
To Show that Seeds Contain Mineral Matter. - Burn seeds to 
ashes in a crucible over a hot flame. What became of the carbon? 
What became of the water ? What else was in the seed ? Account for 
changes of form. What life process of the embryo uses carbon in the 
same way? 
1 1. Copper sulphate 34.5 grams 
Water 500 cc. 
Set aside until completely dissolved. This is solution number 1. 
2. Rochelle salts 173 grams 
Caustic soda 50 grams 
Water 500 cc. 
Do not mix until ready to use, then take equal parts of each. 538 
SEEDS AND GERMINATION 
372. Where Foodstuffs Are Stored in Seeds. - In the 
bean, we have seen that both carbohydrates and proteins 
were stored in the cotyledons, evenly distributed, so far as 
we can discover. In the endosperm of a corn grain, the 
carbohydrates are under the scutellum, and the proteins 
in a distinct layer outside of the carbohydrates, covered by 
the flinty outside coat of the grain (see Figure 355). 
373. Digestion of the Food in the Seed. - It may appear 
strange that the growing bean plant lives upon the food stored 
in the cotyledons, and yet such is the case. But this food 
must undergo a real digestion before the bean embryo can 
use it. We do not know just how this digestion takes place 
in the bean, but in the corn, as we have learned, there is a 
special structure, the scutellum, which helps to digest the 
food in the endosperm. Digested food is absorbed by the 
cells by osmosis, and passed into the phloem vessels, whence 
it is distributed to all parts of the plant through the vascular 
bundles. When scientists learn more about the digestive pro- 
cesses of plants they will probably find that they are similar 
to the same processes in animals. 
LABORATORY STUDIES IN GERMINATION 
To Teachers. - It is possible to make this one of the most valuable 
parts of biology to the pupils. Instead of making demonstrations it 
is suggested that the pupils be provided with material or asked to get 
it and work out the answers to the questions themselves, making their 
reports for each experiment under headings: Object, Apparatus, Pro- 
cedure, Observations, Conclusions. They should be encouraged to 
think out new experiments when results do not agree, and they should 
be taught to make checks on their work. 
The teacher should, however, perform the experiments at the same 
time, in order that time may not be lost. Each experiment should be 
preceded by a review of the knowledge the pupils already have about 
the topic. 
Beans and corn for class work should be soaked overnight at room 
temperature, or for two hours in warm water. 
Beans should be first soaked for several hours, then planted about a 
week before the lesson on seedlings. LABORATORY STUDIES IN GERMINATION 
539 
To Show the Necessity of Stored Food. - 
1. Remove the embryos from several seeds. Place them in soil 
under favorable conditions for growing. 
2. Plant others under the same conditions except that the embryo 
is still inclosed by the cotyledons. Which grow? Why? 
3. Remove most of the endosperm from a few kernels of corn. Plant 
these and compare the seedlings from time to time with those from whole 
kernels planted at the same time in the same dish. 
4. Remove most of the cotyledons of a bean embryo. Place it in 
the earth or damp sawdust beside one which has whole cotyledons. 
Make sketches at each laboratory period to show the difference. What 
does this experiment show? Repeat the experiment with other seeds. 
To Show that Germinating Corn Seeds Digest Starch. - Remove 
the scutellum from each of several grains of corn when softened by soak- 
ing. Remove some of the white part of the grain. Apply the test for 
starch and decide whether the white part of a corn grain contains much 
starch. Now place a thin layer of moist corn starch in a watch glass 
and upon it lay several scutella. Cover with a bell jar and set in a 
warm place overnight, taking care that it does not dry out. Then test 
with Fehling's solution. What change has taken place? What is the 
name of the process which changes starch to sugar? How is the sugar 
distributed? Invent an experiment to show the same change without 
removing the scutellum from the grain. (Hint, use wheat or oats, 
soaked and mashed) . 
To Show the Necessity for Air. - 
1. Boil a few ounces of water to drive out the air. Cool it. Place 
some seeds in it and pour paraffine or heavy oil over the top to shut out 
air. Set aside and examine from time to time. Use as many kinds 
of seeds as possible, including sunflower and unhulled rice.1 
2. Do the same kinds of seeds sprout in water not boiled and sealed? 
3. Plant some seeds in soil which is several inches deep and pack the 
earth firmly over and around them. 
4. Plant others of the same kind, and pack the soil lightly. Which 
germinate better? Why? 
To Show Production of Carbon Dioxide. - Germinate a handful of 
soaked peas, beans, com, or oats in a wide-mouthed bottle. Fit the 
1 Rice is one of the very few plants that do not need air for germination. 
This is not saying that they do not respire, or that they do not need oxygen, 
however. An interesting adaptation of rice grains is that they have the ability 
to break water up into oxygen and hydrogen, use the oxygen so obtained, 
and set the hydrogen free. Other seeds, and animals that live in the water 
get their oxygen from air which is mixed with the water. 540 
SEEDS AND GERMINATION 
bottle with a rubber stopper with one hole in it. Bend into U-shape a 
glass tube of suitable size to fit the hole, making one arm longer than 
the other. Insert the short arm just through the stopper and let the 
longer one dip into a beaker containing lime water. Set aside over- 
night. What is the appearance of the lime water? What gas causes 
this appearance? Where does it come from? Do dry seeds give off 
carbon dioxide? 
To Show that Germinating Seeds Use Energy. - Fill a small un- 
glazed plant jar with bean or pea seeds which have begun to germinate. 
Fit a cover tightly into the top of the jar and wire it securely. Set the 
jar where growing conditions are favorable and observe what happens 
after a few hours. How do you account for this? 
What causes thistles and burdocks to come up through old asphalt 
pavement ? What causes the roots of trees to make flagstones irregular 
in height? Will a growing plant lift a weight? Look for potatoes that 
have been pierced by the underground stems of quack grass. 
To Show the Necessity for Moisture. - 
1. Place a few dry beans in dry sand in a warm room. 
2. Place others in water near them. 
3. Place others in moist earth near the other two. When any of 
the seeds sprout, decide which of the conditions are best for germination 
and why the others were unfavorable. 
To Show the Necessity for Warmth. - 
1. Plant two sets of seeds in moist earth. Set one dish in a warm 
room, seeing that it does not become too dry, and put the other in a 
refrigerator. Which germinate first? Why? 
To Show that Soil is Necessary for the Normal Development of a 
Plant. - Germinate seeds of pea, bean, squash, and grains of corn in 
damp sawdust, in soil, and on damp blotting paper. Keep them under 
the same conditions of light, warmth, and moisture. Which germinate 
first? Which grow most rapidly? Which stand erect, and which 
droop first? Second? 
Remove the roots of a plant grown in sawdust, and one grown in soil, 
being careful not to break off the rootlets. Compare with a plant 
grown on blotting paper. What differences do you notice? What 
use to the plant is the soil? Which will grow longest? What does 
the plant in the soil get that is lacking in the sawdust and the blotting 
paper? 
To Show that Light is Necessary for the Normal Development of a 
Plant. - Germinate seeds of corn, bean, and pea in the dark and let 
them all remain there for five days after they appear above the soil. 
Compare them with others of the same kind planted at the same time IMPORTANCE OF SEEDS AND SEED PRODUCTS 
541 
and kept under the same conditions except as to light, noting (1) dif- 
ferences in color, (2) in height, (3) in roots. How do you account for 
lack of chlorophyll ? What other young, growing parts of plants lack 
green coloring matter? (See page 461.) Under what conditions were 
they grown as to light? What effect has light on seedlings removed 
from a dark chamber where they have been grown? How long does it 
take for the effects to show plainly? What changes of color do you 
notice in the plumules of young plants in the spring? In the buds of 
trees? In young leaves? 
Turn a pail, box, or other covering that will exclude the light, over a 
patch of sod or a group of seedlings in some waste place. Note how 
many days it takes for them to lose their green color; how many days 
for them to regain normal color after being blanched. 
To Show the Response of Stems to Light. - Place seedlings in jars 
before a window. What direction do they take? Turn some around. 
What happens after a few hours? Try the same experiment with an 
older plant. Which turns more quickly? Describe these experiments 
and invent others to show the same thing. 
To Show the Response of Roots to Gravity. - Plant a seedling in damp 
sawdust with its plumule up and its roots down. Plant others beside 
it in other positions. After a day or two examine them all. What 
direction does the root always tend to take? The plumule? 
To Show the Response of Roots to Moisture. - Plant seedlings in 
two separate boxes of moist sawdust. Keep the sawdust in one box 
moist, but allow that in the other to dry out. After several days, pull 
up the seedlings and examine the roots. What is your conclusion? 
To Study Seedlings in General. - Place a box of soil in a warm room 
and keep it moist. Observe how many kinds of seedlings grow and how 
each gets out of the testa. How many kinds of seedlings do you find 
growing in your yard or garden ? 
Examine seedlings you can find in garden or field and classify them 
as monocotyledons or dicotyledons. 
374. Economic Importance of Seeds and Seed Products. 
- In thinking of the seeds used as food, we must limit the 
term to its botanical meaning. Many articles of food, such 
as the cereal grains, are commonly thought of as seeds. 
Their use as food has already been discussed. (See § 366.) 
The real seeds that are of greatest use to man as food are 
those of the pulse family, especially beans and peas, which 
alone are the source of most of the protein that is obtained 542 
SEEDS AND GERMINATION 
from plants. The soy bean introduced from Asia is very 
valuable. Mature peas and beans contain more food matter 
than do " green peas " and 11 string beans," the latter being 
valuable more for the bulk they furnish than for their food 
content. 
Besides their use as food, seeds can be used as medicine, 
castor oil and mustard being common remedies that are ob- 
tained from seeds. Castor oil is also used as a lubricant in 
airplanes on account of its not being affected by the cold 
of high altitudes. Two valuable products are obtained from 
cotton seeds: one the oil which is used in preparing foods in 
place of lard and butter, animal fats; the other, thread and 
cloth which are made from the fibers covering the outside 
of the seeds. The fibers are removed by a, process called 
ginning, then the seeds are pressed to remove the oil. The 
refuse forms a valuable food for cattle, especially when 
mixed with other foods. The length of the fibers varies on 
different species of cotton, and the uses which are made of 
the fibers depend on their length. 
Linseed oil is obtained from the seeds of the flax. It is 
used in making paint and other substances. After the oil 
is pressed out, a substance known as linseed cake is left. 
This is used as food for cattle. 
OUTLINE 
Development of bean seed 
Embryo sac 
Fertilization 
Pollen 
Ovule 
Micropyle 
Testa 
Embryo 
Cotyledons 
Hilum 
Adaptations of seed 
Resumption of growth 
Hard tests 
Viability 
Water absorption 
Food storage 
Cotyledons 
Growth of bean embryo 
Roots 
Primary 
Secondary 
Hypocotyl 
Peg 
Plumule QUESTIONS 
543 
Growth of Corn 
Embryo 
Endosperm 
Cotyledon 
Scutellum 
Foods in Seed 
Carbohydrates 
Starch 
Sugar 
Proteins 
Fats 
Oil 
Digestion 
In scutellum 
Osmosis 
Economic importance of seeds 
Foods 
Medicines 
Lubricants 
SUMMARY 
The seed is the plant's provision for a new generation. It contains 
the new plant and food for its early growth. Before a seed can grow, 
it must have the right conditions, warmth, moisture, and food. Before 
the embryo can use the food stored up in the seeds, it must digest it and 
distribute it. In getting free from the testa and in forcing its way 
through the soil, a new plant uses energy. Respiration releases the 
energy obtained from the food by oxidizing the carbon in the proto- 
plasm of the young plant. The hypocotyl is the part of the embryo 
and young plant that helps it get out of the ground into the light. 
Although seeds will germinate without either soil or light, both are 
necessary for the healthy growth and development of a land plant. 
QUESTIONS 
What is the function of a seed? What are the parts of a seed? 
What are the conditions necessary for germination? For growth? 
What is a seedling? What kinds of foodstuffs are stored in seeds? 
Why does a young plant (embryo) need energy ? What is the function 
of digestion to the embryo? Of circulation? Of respiration? What 
use does man make of the seeds of plants ? CHAPTER XXXII 
FORESTS AND FOREST PRODUCTS 
The groves were God's first temples. 
-Bryant 
375. The Importance of Forests. - Forests are important 
directly for the lumber, fuel, and other products obtained 
from them, and indirectly in several ways less likely to be 
thought of. For instance, forests prevent floods and freshets. 
They do this in two ways, (1) by holding back the melting 
snow in the spring, thus making it possible for streams to 
carry off the water without overflowing their banks; and 
(2) by forming a soil which contains a large amount of or- 
ganic matter called humus which has the property of ab- 
sorbing water much as a sponge does, and letting it seep out 
gradually, thus maintaining a uniform flow of water in 
streams and a constant supply in springs. 
The water systems of many large cities depend for an un- 
failing supply of water upon streams which have their head 
waters in the mountains which are covered by forests. 
When the trees are removed from a tract of forest and the 
land left uncultivated, the humus is easily washed away by 
heavy rains, for it is lighter than the soil lying underneath, 
and the roots which held it in place have been destroyed. 
This is the most valuable part of the soil for crops. The loss 
of this good soil is not the only evil which follows, however, 
for with the washing away (erosion) of the humus, streams 
form which soon cut channels into the subsoil, deeply erod- 
544 THE IMPORTANCE OF FORESTS 
545 
ing it and making the tract unfit for cultivation. At the 
same time, the large streams and harbors are being filled with 
the soil which is carried down and deposited in them, and 
many of them become impossible to navigate unless they are 
constantly dredged. This is a costly process, and a needless 
one, if the knowledge we have were put into practice. 
Figure 359. - What Deforesting Did in China. 
This represents the appearance of 200 square miles of once wooded moun- 
tains, which a century ago paid rich revenue on their lumber products. 
Erosion can be prevented by planting crops or by refores- 
tation. The roots of plants help to hold the soil, and the 
leaves which fall and decay year after year gradually forming 
a layer of humus make the land productive again in the course 
of a few years. Vast tracts of land which are now worthless 
for cultivation could be brought back to fertility by refores- 
tation, and at the same time produce a crop of valuable 
trees which would regulate the flow of streams. 546 
FORESTS AND FOREST PRODUCTS 
376. Attitude of the Early Settlers towards Forests. -• 
When the settlers came to America, the forest on the eastern 
coast extended for about a thousand miles inland from the 
Figure 360.- What Deforesting Is Doing in the United States. 
A scene in North Carolina showing the rapid removal of soil after the 
forest is cut. 
Atlantic, reaching to the treeless prairies of the central plain. 
On the western coast was a belt even wider extending from 
the prairies across the Rocky Mountains to the Pacific Ocean. LUMBERING 
547 
The first care of the settlers was to provide shelter from 
wild beasts and from the hostile Indians, and their second 
care was to secure a supply of food to last over the winter. 
To accomplish both of these, the destruction of trees was 
necessary. Trees furnished the most abundant and the 
most natural material of which to build houses and to make 
fuel, and they had to be removed before crops could be 
planted. Furthermore, they sheltered the settlers' enemies, 
so it was a matter of safety to have extensive clearings around 
the houses. Besides, trees were so plentiful that there was 
no need to be careful about using them. This attitude has 
been so thoughtlessly maintained that large tracts have 
been cleared for immediate profit or pleasure without thought 
of the future. Now the time has come when forests have to 
be conserved and additions made to them so far as possible, a 
condition which will become even more marked as the popu- 
lation increases and as the needs for wood and lumber be- 
come greater. Conservation does not mean locking up the 
products of forests to prevent their being used, but seeing 
that they are properly used and providing for a future 
supply. Conservation has become necessary on account of 
previous extravagance. 
377. Lumbering. - This includes, primarily, cutting the 
trees, and getting them to the sawmill. Great waste has 
been characteristic of unscientific lumbering. This waste 
assumed two forms, injuring young trees in felling mature 
ones, and making use only of the most valuable part of the 
trees felled. The latter practice not only wastes much wood, 
that might be used in many ways, but it is also a menace to 
neighboring forests to have the dead, dry tops and limbs 
lying about to afford fuel for fire. 
When lumbering is done scientifically, injured young trees 
are pruned and treated so that they may not become diseased 
by the entrance of spores of wood-destroying fungi, and all 
parts of the trees felled are either made use of, or the less 548 
FORESTS AND FOREST PRODUCTS 
valuable are piled and burned under conditions which do not 
menace the safety of the remaining trees and which leave a 
clean floor, one of the best possible protections against forest 
fires. 
378. Methods of Forest Protection. - Young forests, 
and old ones too, have their enemies. Fire, set by lightning 
Figure 361. - Fire Slash. 
The scene of a great destructive fire in 1908. 
or careless smokers or campers, fungal diseases, made pos- 
sible by accidents or careless pruning, and insect enemies, 
require that forests have supervision and attention to pre- 
vent damage and consequent loss to the owners. The persons 
who watch over forests in this way are called forest rangers. 
The Work of a Forest Ranger. - A forest ranger has nu- 
merous duties, chief among which are to look out for fires and METHODS OF FOREST PROTECTION 
549 
to report them when they occur. As a prevention, campers 
and others are cautioned to be careful about letting fire 
spread, stations or lookouts are maintained from which a 
large territory can be surveyed for signs of fire, airplanes are 
also used to this end, telephone lines are kept in repair to 
provide for calling help to fight fire, roads are cut for the same 
purpose, and also with a view of. making it possible to check 
the spread of fire by removing all brush and other material 
which will burn. 
Figure 362. - Sign Containing Warning About Fires. 
When fire occurs, it is fought by clearing paths at intervals, 
across which it cannot travel for lack of fuel. Trenches 
have the same effect. In some cases fires are beaten out 
with damp cloths or with branches of trees, and in rare 
cases, by the use of water. In some states regular trains 
are maintained on which are huge tanks containing water, 
and apparatus for throwing it some distance from the track. 
Prevention has proved more effective than any kind of de- 
vice, however, and most efforts are being made in that di- 
rection. Signs and posters warn persons to be careful. 550 
FORESTS AND FOREST PRODUCTS 
Campers are taught how to select a spot for a fire, how to 
care for it to prevent its being a menace, and how to put it 
out when breaking camp. 
379. Forest Fires. - One of the most useless and unneces- 
sary wastes of forest land is that caused by fire. Not only 
are thousands of dollars lost every year on standing timber, 
but the young growth also is utterly destroyed. 
Figure 363.-The Result of Hurricane and Fire in Idaho. 
Of the forest fires in the United States during 1917, 7814 
in number, 2132 were caused by lightning, and the others 
by human means, nearly all preventable; 952 were incen- 
diary ; 1288 were caused by careless campers; and 1003 by 
sparks from railroad locomotives, in violation of laws which 
call for spark arresters on engines used in or near the forests. 
Forest rangers keep watch to see that fungus does 
not cause the death of trees, and to prevent the spread of NECESSITY OF REFORESTING 
551 
such diseases when they are found. In localities where 
cleared spaces in the national forests are rented for grazing 
purposes, forest rangers see that the regulations concerning 
the grazing of cattle are observed, collect fees, and other- 
wise serve as government agents. In some localities, the 
tract must be regularly 
patrolled to prevent the 
theft of valuable timber. 
The life of a forest 
ranger requires good 
health and a love for the 
out-of-doors. It requires, 
too, at least a common 
school education, with 
special training to enable 
the ranger to recognize 
fungal diseases, and to 
estimate the quantity of 
timber on a tract or the 
lumber in a tree. 
380. Necessity of Re- 
foresting. - So great is 
the value of forests that 
efforts are constantly 
being made to increase 
forest areas. Reforesting is necessary when tracts have 
been cut over or have been destroyed by fire. The state will 
cooperate when large tracts are to be reforested. There 
are three ways, the use of any one of which depends on local 
conditions. Seeds may be gathered and sown broadcast, 
but this is expensive and wasteful, as most of the seed is 
lost by falling on spots where it cannot grow, or is eaten by 
squirrels and birds. Again, it is not evenly distributed, 
and to obtain an even set requires additional work in trans- 
planting. 
Figure 364. - Castle Peak Fire Lookout 552 
FORESTS AND FOREST PRODUCTS 
Better results are obtained the second way, namely, by 
planting the seeds evenly and covering them to reduce the 
number that may be wasted. This is nearly as costly, and 
not so satisfactory as the third method, which consists of 
planting the seeds and raising the young plants in nurseries 
till they are old enough to live in the open. Then they are 
set out under favorable conditions, in large numbers, and 
Figure 365- - Nursery Where Young Trees Are Started. 
allowed to grow with only such care as disease or injury 
make necessary. 
381. Forestry and the Department of Agriculture. - The 
chief work in forestry of the United States is in charge of 
the United States Department of Agriculture. This is be- 
cause the science of forestry is essentially a branch of agri- 
culture, for it has to do with the growing of successive crops 
of timber from the soil. 
The administration of the National Forests is directly in 
charge of the Forest Service, which is a bureau of the Depart- FORESTRY AND DEPARTMENT OF AGRICULTURE 
553 
ment of Agriculture. Its chief is designated the " Forester." 
Besides administering the National Forests, he supervises 
investigations in the best use of the forests and their pro- 
tection. 
The timber, water, grazing, recreational opportunities, 
and other resources of the National Forests are for the use 
of the people. These forests contribute to industrial enter- 
prises through their yearly cut of over three quarters of a 
billion feet of timber, used mostly by sawmills and mines; 
they protect watersheds, which furnish about one third of 
the water-power resource of the country; they supply pure 
and abundant water to a thousand towns and cities; they 
furnish pasturage for nearly 15,000,000 head of livestock of 
all ages ; and they afford playgrounds for millions of recrea- 
tion seekers, to whom these vacation places are made acces- 
sible by the building of roads and trails. 
Figure 366. - Airplane View of Evergreen Forest. 554 
FORESTS AND FOREST PRODUCTS 
In 1921 the total net receipts from the National Forests on 
account of timber sales, grazing fees, and special uses were 
84,468,940. 
382. Forestry in Other Countries. - The care of the for- 
ests in European countries began many years earlier than 
in the United States. This has resulted in a systematic 
organization of the forest work; in a greater interest in the 
scientific investigations of all forest problems; and in a 
deeper appreciation by the public of the value of forests. 
There one can study the results of many years of systematic 
planting and cutting. We have so many trees in this coun- 
try that only slight attention has been given to utilizing all 
parts of the tree when it is cut. In Germany, Sweden, and 
Denmark the complete utilization of every part of the tree, 
down to branch wood one inch and less in diameter, is com- 
mon practice. 
There is still another feature of the forest development 
in Europe that is of interest. Many of the small villages 
own communal forests which belong to the people of the 
village. These are kept at a high state of production. 
They furnish the timber needed in the particular locality 
and afford a substantial income to the people. 
383. Federal and State Protection. Parks. - The for- 
ests of the United States now cover about 550,000,000 acres, 
or more than one fifth of the total area. According to good 
authority these resources are sufficient to supply our lumber 
industries and firewrood consumption, provided the area is 
properly stocked and conserved. This can best be done by 
the federal and state governments, which appropriate huge 
sums every year for the protection of forests and the de- 
velopment of parks. 
Forestry in New York State. - The largest tract in this 
state is the Adirondack Preserve, which consists of about 
4,600,000 acres. The next in size is the Catskill Forest 
tract of 1,200,000 acres. Smaller parks are the Long Island TREES IN PARKS AND STREETS 
555 
Pine and Oak Lands, The Hudson Highlands, and Allegheny 
Highlands. 
National Forest Preserves. - In 1891 President Harrison 
set aside the Yellowstone Park Timberland Reserve, which 
was the first forest preserve. Since that date other presidents 
have set aside other regions, until there are one hundred and 
forty-nine National Preserves with a total net area of over 
156,000,000 acres. 
384. Care of Trees. - Trees are subject to the attacks of 
fungal diseases and to the ravages of insects. Certain in- 
sect larvae can be prevented from ascending trees by catch- 
ing them under bands of burlap fastened around the trunk 
of the tree near the bottom, or they may be caught by bands 
of sticky paper fastened around the trunk. Insects which 
eat the leaves can be killed by a poison spray (see page 12), 
and those which suck the juices can be killed by a spray 
which clogs their spiracles (see page 66). Insect-eating 
birds like the chickadee, the wren, the nuthatch, the phoebe, 
and many others are the best friends a tree has. Birds 
should be protected and encouraged, for they are a great aid 
in fighting insects. 
Tree Surgery. - Trees should be examined frequently 
for evidence of disease and injury from the elements and 
from insects. If dead or broken limbs are found, they 
should be sawed off smoothly as close to the trunk as pos- 
sible, and the fresh surface painted over to prevent the en- 
trance of spores of fungi or of bacteria. In case a tree has 
been split, its life may sometimes be greatly prolonged by 
bolting the parts securely together or surrounding them with 
a band of iron. Decayed parts should be cleaned out and 
the hole filled with cement to give strength and to prevent 
further decay. The scientific treatment of diseased or broken 
trees is known as tree surgery. 
385. Trees in Parks and Streets. - Trees that are 
planted along streets, especially paved streets, do not thrive 556 
FORESTS AND FOREST PRODUCTS 
unless special provision is made to enable their roots to 
obtain a supply of water and of air. This is done in some 
cities by covering an area with grating as far around the tree 
as possible and by systematic watering during dry weather. 
The grating is so made that it can be used as part of the 
sidewalk. Many fine old trees are killed every year by the 
injury done to their roots in grading for paving, and in de- 
priving them of moisture 
by laying paving mate- 
rial which excludes water 
over a great part of the 
area occupied by their 
roots. 
The importance of 
trees in parks and around 
homes cannot be meas- 
ured. A few of the rea- 
sons why they should 
be planted are given, 
and you can add many 
more by a little thought. 
(1) Trees add greatly 
to the attractiveness of 
a locality or a home. 
(2) They furnish shade. 
(3) They increase the 
humidity of the air (see page 458). (4) They furnish homes 
for birds. (5) They increase the amount of oxygen in the air, 
and decrease the amount of carbon dioxide. The amount of 
water which is given off by a forest is sufficient to produce a 
noticeable effect on the climate of the immediate vicinity. 
386. Some Common Trees. - The total number of kinds 
of trees in the United States is over 500, of which about 150 
kinds are used as lumber. Each forest region has its few 
important trees, which can be readily learned. 
Figure 367. - Hemlock Twigs and 
Cones. SOME COMMON TREES 
557 
The common trees in the United States fall into two general 
classes: (1) The narrow-leafed, cone-bearing, soft woods 
such as pine, spruce, balsam (the Christmas tree), hem- 
lock, cedar, and others; in short, the evergreens. (2) The 
broad-leafed, non-cone- 
bearing, hard woods such 
as elm, maple, beech, 
oak, birch, basswood, 
and many others. 
The use of the terms 
hard and soft wood is a 
lumberman's way of de- 
scribing the difference 
between the two classes 
irrespective of the fact 
that basswood is softer 
than the evergreen long- 
leafed pine. 
Shade Trees. - When 
one has occasion to plant 
a tree, the question often 
arises as to what is the 
best kind of tree to plant. 
While much depends on 
where the tree is to be 
planted, and on the care 
it will receive after- 
wards, there are a few 
general facts that should 
be kept in mind. 
Elm trees, poplar 
trees, and silver maple trees have the bad habit of clogging 
waste and sewer pipes in their search for water, of which they 
demand a large supply. Besides, one should consider that 
silver maple trees are brittle and apt to split when they 
Figure 368. - White Pine Cone. 
There are five needles in a bundle. 558 
FORESTS AND FOREST PRODUCTS 
become old, and that their shade is light. Elm trees in some 
localities are subject to the attacks of elm beetles and require 
spraying to preserve them. Poplar trees are hard to kill when 
it becomes necessary to remove them, owing to their habit of 
sending up sprouts from the roots and from the stump. 
Horse-chestnut and catalpa trees make a great deal of lit- 
ter, detracting from their 
usefulness as ornamental 
trees. Other trees, like 
the Norway maple, have 
the habit of branching so 
low that they require 
frequent trimming in 
cities, to prevent their 
being in the way of um- 
brellas. The trimming 
is likely to mar their 
symmetry. 
Hard maple, oak, syca- 
more, ash, linden, and 
tulip are satisfactory 
trees for most localities, 
having all the good fea- 
tures and none of the bad 
ones of the other trees 
mentioned. It should 
be remembered in plant- 
ing trees along paved 
streets that the condi- 
tions are very hard, and they should have special care, 
otherwise they will die from much cutting of the roots and 
branches, from the attacks of insects, and from the lack 
of food and water. In planting, trees should have space 
enough left between them so that each tree may grow on 
all sides. 
Figure 369. - Twigs and Cones of 
Norway Spruce. 
Commonly planted for ornament. PINE TREE AS A TYPE 
559 
It is important that you should appreciate that these 
huge plants live in just the same way as small, even micro- 
scopic plants do. To make this point clearer, we shall give 
a short account of the 
pine and some of the 
evergreen trees. 
387. Pine Tree as a 
Type. - The pine illus- 
trates the plants of this 
family. The pine has all 
the parts of a flower- 
ing plant - stem (trunk), 
branches, roots, leaves, 
seed producing organs, 
and fruit (cones). 
Stem. - The trunk 
does not divide, - a 
marked characteristic of 
conifers. In a forest 
where trees are crowded 
together and there is in 
consequence a struggle to 
get light, the trunks grow 
tall and most of the 
branches are near the top. 
A cross section of a 
stem shows a series of 
rings, known as annual 
rings, by which the ap- 
proximate age of the tree 
can be told. In the 
spring, when all the con- 
ditions are at their best 
and growth is rapid, the 
cells of the tree are large 
Figure 370. - A Group of Redwood 
Trees. 
This kind of evergreen grows best in the 
Rocky Mountains and west of them. 560 
FORESTS AND FOREST PRODUCTS 
and thin-walled, strength being sacrificed to size. In the 
fall or during a dry time in summer, the cells formed are 
much smaller and the walls thicker. These small cells which 
show most plainly make up the annual ring. During a 
season in which long, dry periods occur, 
more than one ring may be made. From 
the center to the bark extend medullary 
or wood rays. The part of the stem 
where increase in thickness takes place 
is just under the bark. 
Branches. - The branches leave the 
stem almost horizontally and nearly in a circle around the 
trunk of the tree. In the pine they curve upward, but each 
kind of evergreen has its own habit of curvature in its 
branches. 
Leaves. - The leaves, called needles, are long, slender, 
and flattened on one side. They grow in bundles of two, 
three, four, or five needles, according to the kind of pine. 
The leaves, which are 
borne but once in a place, 
remain on the tree from 
two to five years* and 
then fall oft, leaving the 
branches bare except near 
the ends. 
Roots. - The roots of 
the pine vary according 
to the kind of pine and 
according to the soil, but 
they are always exten- 
sive. 
Seed-producing Organs. - Early in the spring, two kinds 
of organs are found on the new shoots which grow from the 
terminal buds. The pollen bearers look like short cat- 
kins, and are borne in clusters near the base of the shoot. 
P n 11 p n 
/Grain 
. 
„ „ 
Grain of Pine. 
Figure 372. - Young Ovule-bearing 
Organ (Cone.) PINE TREE AS A TYPE 
561 
They consist of scales arranged spirally around the central 
axis. Each scale bears two pollen sacs. They wither 
soon after shedding their pollen, although they may remain 
on the tree for a year. 
The other kind of organ, 
the ovule bearer, is short 
and thick, and is found 
at the tip of the shoot 
or on the side of the shoot 
near the tip. It, too, is 
made up of scales ar- 
ranged spirally around a 
central axis. Each scale 
near its base bears two 
ovules. When the pollen is ripe, each grain, being provided 
with wing-like air sacs, is easily blown about by the wind. 
Some of the pollen sifts into the ovule-bearing organ (young 
cone) through the spaces between the scales, which at this 
time are separated slightly. 
Then the scales close up, the 
cones turn downward, and 
continue to grow for several 
months (Figures 372, 374). 
Fruit. - During the next 
year, the pollen grains which 
are shut up inside the scales 
put forth pollen tubes and 
fertilize the egg cells which 
develop in the ovules. From 
the fertilized eggs the embryo 
pines develop. 
When the cones are about 
two years old the scales open 
and allow the seeds to drop 
out. Each seed is provided 
Figure 373. - Young Pollen bearing 
Organs of Pine. 
Figure 374. - Mature Cone of 
Pine. 562 
FORESTS AND FOREST PRODUCTS 
with a wing by which it is blown about, for the pine depends 
on the wind to scatter its seeds as well as its pollen. 
388. Related Forms of Conifers. - Hemlocks, spruces, 
firs, and balsams have smaller, flatter needles than the pines 
and they are not arranged in bundles. Cedars have scale- 
like leaves. Larch and cypress trees shed their leaves in the 
fall, but in other respects are much like the pines. 
Habitat. - The evergreens grow in sandy soil in temper- 
ate or in cold climates, but a few of them occur where it is 
very warm. The finest evergreen forests in the world are 
Left, pine ; upper center, fir ; lower center, hemlock ; right, spruce. 
Figure 375. - Evergreen Tips, I 
found in the western part of North America, on the slopes 
facing the Pacific Ocean. 
Economic Importance. - The value of the conifers can 
scarcely be overestimated. Most of the trees are sawed into 
lumber for building purposes, but some of them are used in 
their natural form for telegraph poles, masts of ships, and 
timbers of mines. Wood pulp, from which most of our paper 
is made, is produced from small spruce trees. The by-prod- 
ucts of this group of trees are of great value. From the 
pine come tar, pitch, turpentine, and resin, while the bark 
of the hemlock was formerly extensively used in tanning 
leather. STUDENT REPORT 
563 
FIELD STUDY OR FIELD WORK 
Most of the work in connection with conifers should be done out 
of doors. The student should learn to know by sight all the local native 
evergreens and those commonly planted for ornament. He should 
note the method of branching and the character of the trunk compared 
with other trees. He should observe the position of the cones on the 
branches and be able to give the reasons therefor. In the spring he 
should look for the male and female organs, and for leaf buds in the 
winter. He should examine the leaf scars and the external rings which 
mark a year's growth, and decide how many years each tree keeps its 
leaves. He should note the arrangement of the leaves on the branches, 
Figure 376. - Evergreen Tips, II. 
From left to right, (first two) juniper or red cedar, white cedar, larch. 
the annual rings in the wood and their relation to the grain of the wood, 
the resin on wounds, the curvature of the branches, and other features 
readily observed. 
Make a list of the trees you know by sight. What are the charac- 
teristics of each? What are they used for? 
Make a list of all other trees known to grow in your locality. 
STUDENT REPORT 
^Singlr8 Needles Needles in Cones Cones 
Alternate Scale-like Bundles Large Small 
Hemlock . 
White Pine 
Larch . . 
Cedar . , 
Spruce . . 
etc. . . 564 
FORESTS AND FOREST PRODUCTS 
LABORATORY WORK 
In the laboratory examine a cross section of the stem to see the dif- 
ference in the cells grown in the early and in the late part of a season. 
Note the pith and medullary rays.. If specimens are available, examine 
sections of wood from different trees. Make a collection of the woods 
found in the vicinity. Examine scales from staminate and carpellate 
strobili. With the microscope examine pollen of pine. Draw and 
describe all. 
389. Properties of Wood. - The question may arise, 
What makes wood so valuable? Is there nothing else that 
Left, tangential section ; center, cross section ; right, radial section. 
Note the annual rings in all. The tangential and radial are most com- 
monly used for lumber. 
Figure 377. - Sections of Wood. 
can be used in its place? One of its most valuable prop- 
erties is that it is so easily shaped with sharp tools. An- 
other is that it is light, compared with iron and steel, at the 
same time being tough and elastic. It has remarkable re- 
sistance to crushing, twisting, and pulling apart. A piece 
of yellow pine one inch wide and thick and a foot long sup- 
ported at the ends, bears a load of 720 pounds without break- 
ing. It requires a weight of 17,300 pounds to pull it apart. PRESERVATION OF WOOD 
565 
and a load of 7,400 pounds to crush it. It is beautiful 
and it takes a high finish. The beauty of wood depends 
much on its grain, the closeness of which and the hard- 
ness of the wood determining its suitability for particular 
purposes. For instance, where wood-cuts are to be made, the 
grain must be very small, and the wood very hard. Holly 
and box are best for this. In the case of wood used for 
fork and shovel handles, 
the qualities desired are 
toughness and smooth- 
ness. These are found in 
ash and hickory, and so 
the list might be length- 
ened indefinitely. Balsa 
wood, newly discovered in 
the tropics, is much lighter 
than cork. This is em- 
ployed in making life pre- 
servers and rafts to be 
used in case of accident 
at sea. 
390. Preservation of 
Wood. - There are great 
differences in woods as to 
their ability to last in 
the soil or under water. 
Some, like cypress, cedar, 
and locust, have the 
ability to withstand decay on account of substances con- 
tained in the wood, such as resins. All wood lasts longer if 
it is seasoned, that is, allowed to dry out in the air before 
being used. Wood that is to be used in damp places, however, 
usually needs treatment to prevent or at least to retard the 
process of decay. As decay is caused largely by the work of 
bacteria or of fungi, both of which depend upon moisture as 
Figure 378. - Diagram Showing How 
Logs Are Quarter-sawn. 
A, slabs removed to square the log; 
B, C, short radial sections; D, long radial 
sections. Note that at least one end of 
every section is oblique, and that some 
of the sections are very small, entailing 
waste. Quarter-sawn lumber is used for 
furniture and interior finishing. 566 
FORESTS AND FOREST PRODUCTS 
one of their chief vital conditions, the use of timber thor- 
oughly dried is one precaution taken to insure its lasting. 
Other methods used are charring portions that are to be cov- 
ered by earth, and a third, the most common, is the use of 
chemicals. Railroad ties, for instance, are thoroughly im- 
pregnated with a solution containing creosote, among other 
substances, by being soaked in it for a long time, or by 
having it driven in under pressure. This acts as an anti- 
septic, preventing bacteria and fungi from growing in the 
wood, and prolonging the usefulness of the timber to a 
remarkable degree. Although treating ties in this way is 
costly at first, it is an economic measure on the whole, 
as it takes a smaller quantity of timber, and less labor 
than would be the case if the ties had to be replaced fre- 
quently. 
Some kinds of wood depend for their beauty on the glisten- 
ing medullary rays. These show to best advantage when 
cut lengthwise or obliquely, an effect obtained in quarter- 
sawn timber. 
391. The Formation of Coal and Peat. - Ages ago ferns 
were more numerous than they are now, and many of them 
grew to be as large as our present trees. Geologists tell us 
that the climate was warmer and more moist than it is now, 
and conditions especially favored the growth of fern plants. 
Where these large ferns died and fell to the ground, great 
masses accumulated. 
As the earth's surface changed, these masses became 
covered with soil or water, and under the influence of heat 
and pressure they, together with other plants now known 
to be primitive seed-bearing plants,1 changed into coal. At 
the same time natural gas and petroleum, or rock oil, were 
formed. No coal is being formed at the present time, and 
1 In some cases, these trees have been found almost entire among the coal, 
and sections of them have been made for study with the microscope which 
are so thin that the cells and even the pollen grains can be studied easily. FOREST PRODUCTS 
567 
when our supply is exhausted we shall have to find other 
sources of heat and power. 
Peat, found in old bogs, consists largely of vegetable mat- 
ter. When dried it can be used as fuel. 
392. Forest Products. - A study of a few minutes will 
show that many articles of everyday use are made of wood. 
For instance, the paper on which you are writing was probably 
made from wood pulp; the pencil which you are using is 
made largely of wood; the table on which you are writing 
is of wood; the floor on which the table stands is made of 
wood ; the walls of the house, or some part of them, are made 
of wood; the cars in which the lumber was brought to your 
city were made of wood; the ties on which the rails rested 
over which the cars ran were made of wood; the chair in 
which you are sitting was made of wood. 
In some localities, maple trees are raised for the sugar 
and sirup which they produce. Chestnuts, hickories, wal- 
nuts, and others give us nuts year after year, as well as lum- 
ber when they are cut down. Willow trees give us a supe- 
rior kind of charcoal used in medicine and in making certain 
kinds of gunpowder; the poplars and basswood or linden 
give us excelsior, so useful in packing fragile articles and in 
making cheap upholstery. Turpentine, obtained from the 
pine trees, is used in paint and varnish. Thin sheets of the 
more beautiful kinds of wood are laid over the cheaper or 
less beautiful kinds in the form of veneer. Wood alcohol, 
so useful as fuel, is obtained from wood wastes, like sawdust 
and shavings. Resin has many uses. 
Perhaps the most extensive use of the forests is for lumber 
and fuel. White pine was formerly the kind of pine most 
in demand as well as the most abundant. Now yellow 
pine is taking its place on account of the scarcity and high 
cost of white pine, although yellow pine is slightly inferior. 
White oak is highly valued for interior finishing, floors, and 
furniture. Maple is a fine-grained, hard wood which is 568 
FORESTS AND FOREST PRODUCTS 
much prized for furniture and other purposes. Curly maple 
and bird's-eye maple are valued as wood for veneer. The 
former has a wavy grain, and the latter numerous glistening 
points scattered through it, thought to be undeveloped ad- 
ventitious buds. Black walnut, cherry, and mahogany are 
valuable for furniture. Hickory, elm, and ash are used for 
handles of tools and for parts of vehicles where toughness is 
required. Applewood, holly, and box are sought for turned 
articles. Cedar, larch, and cypress are used for posts and 
poles, and basswood for trunks and crates on account of its 
toughness, lightness, and elasticity. Poplar and catalpa, on 
account of their rapid growth, are planted where shade is 
desired in a short time. 
One of the most valuable forest products is rubber, which 
is made from the sap of the rubber tree. The value of this 
product and the extent of its use are enormous. Boots, 
erasers, rain-coats, bands, automobile tires, and wire insula- 
tion are only a few of its many uses. 
393. Forestry as a Vocation. - Forestry is the raising 
of repeated crops of timber upon soils unsuited to agricul- 
ture, and it has been extended to include the proper use of 
these forest crops. The science of forestry is so new that 
there is some difference of opinion as to the true defi- 
nition. 
We usually think only of large trees when we think of a 
forest, but it really includes all the life found in and upon 
the soil; trees, shrubs, herbs, and grasses are all parts of the 
forest life. Even expert foresters are unable to identify all of 
the kinds of life found in forests. The shrubs alone require 
many years of study. But all foresters must be familiar 
with most of the trees, and the specialist readily names each 
one. 
To insure a thorough technical knowledge of the subject, 
colleges of forestry have been founded. Besides the theo- 
retical training offered in the colleges, the men are taken FORESTRY AS A VOCATION 
569 
out into the forests for practical work under supervision. 
Such training affords great opportunities for men interested 
in this work as a vocation, and their service to the country 
can hardly be overestimated. 
OUTLINE 
Importance of forests 
Prevention 
Of floods 
By retarding melting of 
snow 
By forming humus 
Lumbering 
For building 
For fuel 
Waste 
Forest protection 
From carelessness 
From insects 
Forest rangers 
Forest fires 
Reforesting 
U. S. Department of Agri - 
culture 
Forest Service 
National forests 
In other countries 
Federal and State protection 
Parks 
New York preserves 
National preserves 
Care of trees 
Insects 
Surgery 
Common trees 
Evergreens 
Pine 
Spruce 
Cedar 
Hemlock 
Deciduous 
Elm 
Oak 
Maple 
Birch 
Pine as a type 
Stem 
Branches 
Leaves 
Roots 
Seed-producing organs 
Fruit 
Related Conifers 
Habitat 
Economic importance 
Properties of wood 
Light 
Tough 
Elastic 
Beautiful 
Useful 
Preservation of wood 
Drying 
Charring 
Creosoting 
Formation of coal and peat 
Forest products 
Pulp for paper 
Building materials 
Fuel 
Saps 
Maple sugar and sirup 
Turpentine 
Resin 
Forestry as a vocation 570 
FORESTS AND FOREST PRODUCTS 
SUMMARY 
Forests are of value to man for their products, for their influence in 
preventing freshets and erosion, in making soil, and in tempering cli- 
mate. Forests are being used up so much more rapidly than new ones 
are growing, that conservation and reforestation are being practiced 
by both national and state governments. The enemies of forests are 
man's wasteful cutting, fire, and the ravages of insects and fungal dis- 
eases. Among their best friends are the foresters. 
QUESTIONS 
What is a forest ? How are forests useful to man ? Why is refores- 
tation necessary? What is being done to conserve forests? What 
are the duties of a forester? What is forestry? 
How are evergreens like other plants ? How do they differ from other 
plants? What kind of trunk is characteristic of soft woods? How 
does a tree which grows in a forest differ from one which grows in an 
open field? Why? What are annual rings? How are they formed? 
Describe the branches; the leaves; the roots; the organs which pro- 
duce pollen and ovules; the fruit. Name the evergreens. Make a 
list of the uses to which lumber is put. What other products come 
from the evergreen forests ? In what ways are forests beneficial ? What 
are the governments doing to protect them? What regions in your 
own state are covered with forests? 
REFERENCES 
Bergen and Caldwell, Practical Botany, pages 390-411. 
Coulter, Plant Life and Plant Uses, pages 195 and 196. 
Moon, The Book of Forestry. 
Government pamphlets and bulletins. 
Hough, American Woods. 
Keeler, Handbook of Trees. 
National Geographic Magazine. 
Sargent, Trees of North America. 
Schenck, Forest Policy. 
Snyder, General Science, pages 263-269. CHAPTER XXXIII 
FUNGI -PLANTS THAT LACK CHLOROPHYLL 
Truth needs no colour. - Shakspere 
394. Fungi. - The fungi are of importance to us because : 
(1) some can be used as food (the so-called mushrooms); 
(2) one of them, the yeast plant, is used in making bread; 
(3) others spoil our food, as when they grow on bread and 
cake; (4) they cause many diseases in plants. 
Fungi differ from most other plants in two respects. 
(1) They are colorless, or nearly so, chiefly because they have 
no chlorophyll. (2) They are dependent for food on plant or 
animal substances, either dead or alive, because they lack 
chlorophyll and hence cannot make their own foods as the 
green plants do. 
Fungi which live on the substances or juices of live plants 
or of animals are called parasites (Greek, para, beside; sitos, 
food); and those that live on dead plants or animals are 
called saprophytes (Greek, sapros, rotten; phyto, plant). 
Distribution of Fungi. - Fungi are to be found wherever 
the conditions for their growth are favorable, namely, in damp 
warm places where they can obtain organic food. A dim 
light favors their growth in many cases. The spores remain 
viable for a long time, and their lightness causes them to be 
widely distributed. 
395. The Yeast Plant. - This plant is a unicellular fungus, 
too small to be seen by the naked eye. It is oval or almost 
round in shape, and nearly colorless. It has all the parts 
571 572 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
of a typical cell, although the nucleus cannot be seen without 
a special stain. Because it lives upon dead vegetable matter, 
it is a saprophyte. 
The Work of the Yeast Plant. - In the making of bread, 
we know that: (1) yeast secrets an enzyme which breaks up 
sugar into simpler substances; (2) in this process alcohol is 
formed and carbon dioxide is set free; (3) the yeast lives 
on the protein substances in the flour; (4) both the gas which 
makes bread light and the alcohol are driven off by the heat 
of the oven when the bread is baked. 
Figure 379. - Yeast Plants. 
A, single cell; B, cell with buds; C, group of cells; D, chain of cells. 
Yeast, like all other rapidly growing plants, produces and 
uses vitamins in large quantities. For this reason it is a 
valuable source of these substances because from it they can 
easily be obtained in a cheap form. Before the action of 
bacteria and yeast were understood, much trouble was ex- 
perienced in getting uniform products, owing to the presence 
of undesirable bacteria and yeasts. The possibility of mak- 
ing pure cultures, the use of the microscope, as well as the 
tests which are made in the laboratories at every step of the 
manufacture, have placed the bread-making industry on a 
scientific basis. THE YEAST PLANT 
573 
Reproduction of the 
Yeast Plant: Budding. 
- The method of re- 
production of the yeast 
plant is similar to that 
of the bacterium, but 
differs from it in that 
instead of dividing ex 
actly in two, a bud 
usually pushes out from 
the side of the mature 
plant. Sometimes the 
second plant forms a 
bud before it breaks 
away from the first, 
and so a chain of buds 
is made. Often a single 
plant puts forth more 
than one bud (Figure 
379). 
Figure 380.-'Fermentation Tubes. 
The bulb is filled with nutritive liquid 
containing yeast plants. As they grow 
they form carbon dioxide gas, which col- 
lects in the bulb, forcing the liquid into 
the upright arm. These tubes are used in 
estimating the number of yeast plants in a 
substance and the rapidity of their growth. 
In water analysis, the formation of gas 
with certain media indicates pollution. 
LABORATORY STUDY 
Prepare a Pasteur solution, a good food for yeast, as follows: 
Potassium phosphate 10 parts 
Calcium phosphate 1 part 
Magnesium sulphate 50 parts 
Ammonium tartrate 50 parts 
Cane sugar 750 parts 
Sufficient water to make a total of 5000 parts. (This may be used for 
the culture of other molds than yeast and also for bacteria.) 
Yeast. - Examine yeast cells under low power. Note their glistening 
appearance and their number. Under the high power try to find all 
parts of a typical cell. Label and draw. Look for budding cells and 
chains of cells. Draw. Make a thick paste of water, yeast, and flour. 
Put an equal amount into each of three tumblers. Place one tumbler 
in a cool place. Into one of the remaining tumblers stir a teaspoonful 574 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
of sugar and set both in a warm place. Examine several times a day 
and write down all the differences you observe in the three mixtures. 
Try to give a reason for everything you observe. 
396. Bread Mold. - When examined with the naked 
eye, bread mold appears like a thick mass of felt, made up of 
colorless, closely interwoven threads. These threads are 
called hypha (hi'fe : Greek, hyphe, web) and are of two kinds, 
one lying on the surface of the bread or just below it, and 
the other standing upright above the surface. The first 
are the nutritive hyphae, which digest and absorb food ; and 
the sebond are the reproductive. On the ends of the. latter 
Figure 381. - Bread Mold. 
A, nutritive hyphae; B, spore-bearing (reproductive) hyphae; C, stolon; 
D, sporangia. 
are round black bodies which are full of spores, each of which 
is capable of producing a new mold plant, if it falls into a 
place where conditions are favorable for growth, - that is, 
where it has plenty of food, the right degree of warmth, and 
sufficient moisture. Other kinds of fungi may usually be 
found on a loaf of bread after a day or two, as spores of 
many kinds of molds are floating in the air at all times 
(Figure 381). ECONOMIC IMPORTANCE OF FUNGI 
575 
LABORATORY STUDY 
Wet a piece of bread, put a tumbler over it, and set it in a warm place 
for three or four days. Examine without the microscope to get the 
general appearance. With the microscope note (1) the clear, colorless 
threads (hyphae) making up the mass; (2) the groups of spore-bearing 
bodies, black and round, on the ends of the upright stalks; (3) the spores 
coming out of them. 
397. Economic Importance of Fungi. - We have seen how 
fungi may be helpful like yeast, or harmful, like mold. While 
some fungi, like edible 
mushrooms, are useful 
economically, most are 
harmful. Among these 
may be mentioned vari- 
ous rots, potato blight, 
red rust of wheat, corn 
smut, which produces 
the black mass found in 
an ear of corn, and the 
bracket fungi, which 
grow in large numbers 
on trunks of trees and 
whose hyphae cause the 
death of the tree. 
The fungi used for food are nourishing, but there is a prej- 
udice against their use because other fungi which resemble 
them closely are poisonous. As a matter of fact, it is an 
easy task to learn to distinguish the edible from the poisonous 
fungi. While the harmless fungi are now used as food much 
more than formerly, only a few varieties are raised for trade 
purposes (Figures 383 and 384). 
Plant Diseases. - Because of their importance we are 
going to choose three typical plant diseases, Cabbage Yellows, 
Potato Wart, and Black Stem Rust, and study them to see 
how the fungi destroy our food plants. As you learn about 
This is in condition for picking when 
the inside is white. (From Murrill's " Edi- 
ble and Poisonous Mushrooms.") 
Figure 382. - Common Field Puffball. 576 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
each of these diseases, you will see that it is much more im- 
portant that the disease be prevented than cured. Note the 
kind of knowledge necessary to recognize these fungi and the 
methods used in treating them. In 
the case of the rust, your attention is 
called to the complicated life history 
of this fungus parasite as it lives first 
on the wheat, and then on the wild 
barberry in a never ending cycle. 
The farmer who would be success- 
ful must learn how to recognize the 
common diseases of farm plants. If 
he does not know about this impor- 
tant part of farming, he can ask the 
Agricultural Experiment Station to 
tell him what he ought to know. 
398. Cabbage Yellows. - This dis- 
ease is caused by a soil fungus, Fusa- 
rium conglutinans, which is not known 
outside of the United States. 
Effects. - The fungus attacks the 
roots of the plant either in the seed 
bed or soon after transplanting. It 
works greatest havoc during a hot, 
dry period, as warm soil favors its 
growth. The plants attacked soon 
become stunted and the foliage as- 
sumes a pale, lifeless, yellow color. 
The disease is often more severe on 
one side of the plant than the other, 
causing it to curve towards that side. 
The fungus enters through the roots and passes up to the 
stem and leaves through the vascular bundles, which it soon 
clogs and destroys, as well as the tissue adjoining it. As the 
destruction of the vascular bundles shuts off the plant's sup- 
Figure 383.-Shaggy-mane 
(COPRINUS COMATUS) IN 
Perfect Condition for 
Picking. (From Murrill's 
" Edible and Poisonous 
Mushrooms.") CABBAGE YELLOWS 
577 
ply of food material and water, the lower leaves soon drop 
off through lack of sustenance, and the whole plant either 
becomes sickly and fails to head or dies outright, according 
to the severity of the attack. 
Destructiveness. - On fields moderately infected, from 50 
to 75 per cent of the crop is a loss, while in badly infected 
fields the crop is a total failure. 
Figure 384. - Oyster Mushroom. 
An edible mushroom which grows on wood. (From Murrill's " Edible and 
Poisonous Mushrooms.") 
How the Disease Is Spread. - The fungus is carried from 
field to field in a variety of ways : for example, (1) by diseased 
plants from infected fields; (2) by water which drains from 
infected fields; (3) by wind blowing the dust from field 
to field ; (4) by vehicles, tools, and animals. 
Persistence. - Once introduced into the soil, it remains for 
long periods, experiments extending over fourteen years 
having shown it to be still present and active. Soil infested 578 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
with this fungus is said to be " cabbage sick," but other crops 
grow well in it. 
Control Measures. - Various measures have been tried 
as a means of controlling the disease: (a) Disinfection of 
seed and seed beds. This failed because the fungus was 
in the soil of the field and not on the seeds or in the seed 
beds, (b) Using new land for seed beds. This failed for 
the same reason, (c) Crop rotation, to give the fungus a 
chance to die out. A period of fourteen years was found to 
be too short, so that also was impracticable, (d) Fertiliza- 
tion of the soil with a view to obtaining such vigorous plants 
that they could resist the disease. No success was attained, 
(e) Soil disinfection, for the purpose of ridding the soil of the 
fungus. Nothing was found that was cheap enough or 
that would kill the fungus without being detrimental to the 
growth of the crop. (/) Finding plants able to resist the 
disease, based on the experience of finding now and then a 
head in a whole field that had been able to live when the 
rest were killed. 
The method used was to take such heads and raise seed 
from them for next year's crop. These plants were found to 
produce a higher percentage of resistant plants, the best of 
which were then selected to produce the seeds for another 
crop. In this way strains have been developed that are 
practically immune to the attacks of the fungus. Much 
still remains to be done, but enough has been accomplished 
to make sure that success in combating the disease lies 
in producing disease-resisting plants. No one has yet dis- 
covered what the differences are that make immunity pos- 
sible in one plant and not in another. 
399. Potato Wart. - This is a disease dangerous to the 
common potato which has been known in Europe for many 
years, but which has been found in the United States only 
since 1918, when it was discovered in Pennsylvania. It was 
introduced on an importation of several millions of bushels POTATO WART 
579 
in 1911, which were distributed over the eastern part of the 
United States. Much attention is now being given to 
locating centers of infection, in order that quarantines may 
be established. 
Signs of the Disease. - The effects are found in the potato 
itself and not on the parts above ground, which accounts 
for its not being discovered till harvesting time. The first 
evidences of wart are 
small spongy outgrowths 
on the surface of the 
potato, especially at the 
eyes. Sometimes warts 
arise on different parts of 
the same potato, trans- 
forming it into a spongy 
mass which turns from 
brown, the first color, to 
black, then decays (Fig- 
ure 385). 
What Causes Wart. - 
Wart is caused by a 
fungus which penetrates 
the outer coat of the 
potato and stimulates the 
cells to abnormal growth. 
When the wart decays, it 
fills the soil with millions of sporangia of two sorts, one 
capable of germinating at once and infecting new potatoes or 
new places on the same potato, and the other resting spo- 
rangia, capable of living over the winter and starting the 
infection anew in the spring, or lying dormant for years until 
conditions become favorable for germination. 
How the Fungus May Be Spread. - (1) By drainage from 
infected fields; (2) by distribution of the infected soil; 
(3) by the use of manure of animals which have eaten the 
Figure 385. - Potato Wart. 580 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
raw potatoes; (4) by garbage into which peelings from 
diseased potatoes have been thrown; and (5) by planting 
diseased potatoes or those which have grown in infested soil 
and carry the spores on their surfaces. 
Control of the Disease. - As the result of many experiments 
with disinfection, fertilizers, resistant varieties, and so forth, 
the best means of control seems to be to destroy or boil all 
potatoes grown on such infested land, to establish a strict 
quarantine to prevent its spread, and to practice rotation 
of crops over the period of eight years that the fungus is 
known to remain in the soil. It does not cause damage to 
any other cultivated crop, but it may propagate itself on 
other members of the potato family, especially such as grow 
wild. 
Note. - As an illustration of the application that may be 
made of biology, it is said that the disease was first reported 
in this country by a biology student in high school who had 
noticed potatoes in the field at home, but had not known the 
cause of the peculiar appearance or the seriousness of the 
disease till his teacher mentioned it in class. 
400. - The Black Stem Rust of Grain and the Barberry. - 
The black stem rust of grain causes the loss of millions of 
bushels of grain every year. In 1916, a bad rust year, the 
loss in wheat alone in a single state, Minnesota, was about 
30,000,000 bushels. In 1917, not a bad rust year, the loss 
in the whole United States was about 1^ per cent of the whole 
crop. The wheat affected by rust has shrivelled grains, 
which are light in weight, and straws which are crinkled and 
broken. 
The Causes of the Rust. - This is a fungus which lives as 
a parasite on the stalks and heads of grains and grasses during 
a part of its life history, and on the leaves of the common 
barberry for the other part. This is spoken of as the alter- 
nation of hosts, a habit which is characteristic of several 
other fungi which cause plant diseases. THE RUST OF GRAIN AND THE BARBERRY 
581 
How It Spreads. - The fungus itself is composed of very 
small threads or hyphse which grow inside the leaves and 
stems of the host plant. It spreads from one wheat plant 
to another by means of spores which are carried by the wind, 
insects, or other means. In the early part of the summer 
these spores appear in red pustules on the 
stems and leaves of the infested plants, from 
which they fly like dust when the plants are 
disturbed. On account of their small size 
and large numbers, they fall on other plants, 
some near at hand, and some long distances 
away. When moisture makes it possible, 
each spore sprouts and forms a new center 
of infection. These spores, called summer 
spores, are red or orange colored and egg- 
shaped. In the autumn another kind of 
spore is produced, namely, the black or winter 
spore. These appear in black pustules on 
the stems and leaves of the plants which serve 
them as host. These spores are longer, and 
have thick walls, an adaptation which enables 
them to live over the winter in stubble and 
straw. They are made up of two cells, and 
usually are not carried by the wind. 
When they germinate in the spring, each 
of the two parts produces four round, color- 
less bodies called sporidia. These are blown 
about by the wind, but they are not able to 
propagate the disease unless they fall upon 
the barberry, where they produce a plant so different in 
appearance that it was for many years considered a sepa- 
rate plant and given a different name. On the leaf or fruit 
of the common barberry, the sporidia produce yellow cir- 
cular spots containing reddish spores in long chains. From 
the shape of the spot, this is often called the cluster cup 
Figure 386.-A 
Diseased Head 
of Wheat. 
The dark spots 
are fruiting bod- 
ies of the rust. 582 
FUNGI - PLANTS THAT LACR CHLOROPHYLL 
stage. This stage is most active from May until midsum- 
mer. The spores from the plant on the barberry cannot 
reproduce on the barberry, but on being blown to the grains 
or certain grasses, they begin a new stage in the life history 
of the red rust. These propagate on the grain in the field as 
before. Another source 
of infection is the sum- 
mer spores which may 
have lived over the win- 
ter on the grasses near 
the field, or on straw 
or stubble. A summary 
will put the history 
clearly: (1) the red or 
summer spores spread 
the disease from wheat 
to wheat, or from wheat 
to grasses and back to 
wheat; (2) the winter 
spores formed on wheat 
or grasses in the autumn 
remain on them until 
spring when, by means 
of sporidia, the infection 
of the common barberry 
takes place; (3) the 
cluster cups or spring 
spores on the barberry 
start the infection again 
on the wheat and grasses. 
Conditions Favoring the 
Rust. - Cool nights with heavy dews, followed by hot muggy 
days, afford ideal conditions for the growth of the disease. 
Any condition which favors the growth of the grain and re- 
tards that of the rust is unfavorable to the disease. 
F'gure 387. - Diagram of Life History 
of Red Rust of Wheat. THE RUST OF GRAIN AND THE BARBERRY 
583 
Methods of Control. - No sure means has been found of 
curing the disease, but experiments have proved that there 
are several ways of reducing the amount of damage done by 
it. Among them may be mentioned clean cultivation, 
which gets rid of the grasses on which it grows; planting 
early varieties of grain which mature before the rust has 
time to develop; planting varieties which have been found 
able to resist the disease; and, best of all, getting rid of the 
common barberry. Denmark, which eradicated the bar- 
berry in 1903, has not had an epidemic of rust since. 
Note. - The Japanese barberry, more commonly planted 
for ornament than the common barberry, is immune to the 
rust, and may be spared. 
HOME WORK 
Make a list of the plant diseases you know. Try to find out what 
causes each and how it injures the plant. Make a list of the remedies 
you know of for each disease, such as sprays. Find out from the 
owner of a farm how many bushels of each crop his land produced to 
the acre. Compare this with the average for the United States. Ac- 
count for the difference. What can be done to improve a low yield? 
We close the study of the simplest plants with the fungi. 
As in the case of the bacteria, men have spent their lives 
studying the fungi, especially those which cause disease. 
Much has been accomplished, but a great deal remains to 
be done in finding out the cure for certain fungus diseases, 
especially those that attack vegetables which we use for food. 
OUTLINE 
Fungi 
Kinds 
Useful 
As food 
In making bread 
Harmful 
Spoil food 
Cause disease 
Characteristics 
Colorless 
Dependent on organisms 
Distribution 
In warm, damp places 
Yeast 
Unicellular 584 
FUNGI - PLANTS THAT LACK CHLOROPHYLL 
In bread 
Breaks up sugar 
Forms alcohol 
Gives off carbon dioxide 
Lightens bread 
Vitamins 
Reproduction 
Budding 
Bread mold 
Hyphse 
Nutritive 
Reproductive 
Economic importance of fungi 
Helpful 
Yeast 
Some mushrooms 
Harmful 
Rusts 
Rots 
Blights 
Smuts 
Cabbage yellows 
Effects 
Destructiveness 
How spread 
Persistence 
Control 
Potato wart 
Signs 
Cause 
How spread 
Control 
Black stem rust 
Cause 
How spread 
Control 
SUMMARY 
Fungi are of great importance. While some, like certain mushrooms 
and yeast, are useful, most of them are harmful. Yeast is invaluable 
in making good bread, but other fungi, like bread mold and all the 
various rusts, blights, and smuts, do great damage to living organisms. 
Among the worst of these are (1) cabbage yellows, which have been 
found almost impossible to exterminate, (2) potato wart, which ruins 
many a potato crop, and (3) black stem rust, which causes the loss of 
millions of bushels of wheat each year. 
What fungi are useful? Which ones are harmful? Can you tell 
edible from poisonous mushrooms? What are the characteristics of 
fungi? Where do they grow best? How does yeast affect bread? 
Did you ever eat any unleavened bread? How many ways have beer 
tried to fight cabbage yellows? Describe some of them. How can 
potato wart be controlled? How much damage does black stem rust 
cause each year? How does it spread? How can its ravages be 
reduced ? 
QUESTIONS CHAPTER XXXIV 
PLANT CULTURE 
Where grows? Where grows it not? If vain our toil, 
We ought to blame the culture, not the soil. 
- Pope 
401. Relation of Soil to the Growth of Plants. - We have 
seen (page 540) that it is possible for seeds to germinate with- 
out soil, and laboratory experiments have been made in which 
Figure 388. - Peach Orchard on Reclaimed Mesa Land. 
plants grew in water to which had been added the substances 
necessary for their growth. Under ordinary conditions, 
however, soil is absolutely necessary for the healthy growth 
of most land plants. There are two main reasons for this. 
585 586 
PLANT CULTURE 
First, plants need soil to anchor them. How effectively 
even small plants are anchored can be proved by trying to 
pull a weed a few inches high with only one hand. When 
you think of the great weight of some plants, for example, 
trees, you can see how strong their roots must be and how 
deeply they must penetrate to resist the weight and the force 
of the wind against the tops. 
Second, plants need soil to hold moisture for them to ab- 
sorb, and to furnish the minerals needed for growth. The 
only way they have of obtaining them in nature is in water 
which dissolves small quantities of them. Since soil fur- 
nishes certain elements that cannot be obtained elsewhere, 
and since it is necessary to enable plants to stand erect, it 
follows that there is a very close relation between the charac- 
ter of the soil and the elements it contains and the successful 
growth of plants. This is especially true of cultivated plants. 
Therefore, a farmer studies the kinds of soil and the plants 
best suited to grow in them, and also the best ways to prepare 
the soil to make it of the greatest help to the kind of crop he 
is planting. 
402. Kinds of Soil. - Soils differ not only in the elements 
which they contain (we speak, for instance, of an acid soil 
or an gl^dline soil) but also in the coarseness or fineness of 
the earth. 
Another classification is based on texture, four grades 
serving as a basis for the description. The coarsest is gravel, 
composed of small, usually round, stones. This is the poor- 
est kind for most plants as it does not hold water well. Some- 
what better in the matter of holding water is sand. Irriga- 
tion has made thousands of acres of sandy land productive, 
as water can be supplied whenever it is needed. 
Loam is fine sand which is mixed with a large quantity of 
decayed organic matter known as humus. This is one of 
the best kinds of soil for retaining water. Clay is very fine, 
hard-packed soil which retains water well, if it takes it up. PREPARATION OF SOIL 
587 
It is often too firm for the roots of plants to penetrate to get 
the water. Many other kinds of soil might be mentioned, but 
they are all a combination of the four described. Muck 
consists almost wholly of decayed organic matter. 
403. Preparation of Soil. - Farmers prepare the soil by 
breaking it up, thus allowing the roots to penetrate it easily 
(see page 490). Plowing, harrowing, raking, dragging, and 
spading are the methods used, according to the size of the 
plot cultivated. 
Figure 389. - Irrigating Ditches. 
The humus which lies near the surface and is spoken of 
as surface soil must be thoroughly mixed with the subsoil. 
The depth to which soil is plowed and the degree of fineness 
to which it is reduced are determined by the kind of crop to 
be planted and the amount of cultivation it can receive 
while it is growing. In any case the soil must be loose enough 
for the roots to penetrate it easily, for it is from the soil that 
they gather moisture and food material for the plant. 
Often the preparation of soil includes a thorough mixing 
of fertilizer with it. In some cases also land is so marshy 
that it has to be drained before it can be plowed. 588 
PLANT CULTURE 
404. Seed Selection. - Farmers who try to secure full 
returns for the labor expended make it a point to select 
seed carefully. In several states granges and other organi- 
zations offer courses of instruction as to what constitutes 
good seed, and form clubs among the boys and girls, who 
compete for prizes for yields of superior quantity and quality 
from selected seed. 
Corn can be used as an example of the way in which seeds 
are selected for planting. First, care is taken to save for 
seed ears that are of the right shape and of the right size, 
usually the largest ones, and those that have the grains de- 
veloped at both extremities. This may be called an ideal ear. 
An ideal ear for one variety is not necessarily so for another. 
Dormancy. - Most seeds have a rest period, or period of 
dormancy as it is called. This is longer in wild plants than 
in cultivated ones. In most seeds the dormant period is 
only from the summer of one year to the spring of the next. 
In pigweed, however, the seeds of any one year may re- 
quire several years for development, owing to differences 
in the thickness of the testa. Those grow first which have 
the thinnest testa. Years may pass, therefore, before all 
the seeds of a single crop have grown. This fact and the 
great number of seeds produced are the two main reasons 
why this weed is so persistent. Once it has seeded, it has 
the ground supplied with seeds that will grow some one year 
hence, some two, and so on up to thirty years. 
Other weeds which produce seeds that can lie dormant for 
at least thirty years are shepherd's purse, black mustard, 
chickweed, and curly dock. Variation in the thickness of 
the testa in seeds on the same plant is an adaptation which 
prevents the plant from dying out even if unfavorable con- 
ditions cause the death of all the seedlings of any one year. 
Closely related to the dormancy of a seed is its viability, 
or power to grow after long periods of rest. It has been 
proved by experiments that the seeds of weeds mentioned METHODS OF PLANTING 
589 
above are viable or able to grow after a dormancy of thirty 
years. Such facts as have been established by experiment 
lead us to discredit stories about the growing of seeds that 
have lain in Egyptian tombs hundreds of years. 
Seed Testing. - This is necessary, since it has been found 
that mere appearance is not a safe guide in selecting seed, 
for great difference exists in the viability of different ears 
(see page 588). To test viability, a few grains are taken 
from the base, the tip, and the body of an ear of corn, or from 
hundreds where testing is done on a large scale. These 
grains are all placed under the same conditions for germina- 
tion, as nearly perfect as possible (see page 541), and careful 
records are kept of the results. Only those ears are saved 
for planting which show a high percentage of germinating 
grains. In the case of oats and similar grains, the seeds are 
counted and a record kept of the number which germinate. 
Any kind of seed can be tested in the same way. Old seeds 
should always be tested to save disappointment. (See 
page 588, Viability, and page 527, Use of the Terms Fruit 
and Seeds.) 
405. Methods of Planting. - These vary with the nature 
of the plant, the use to be made of it, and the region where it 
is grown. For instance, corn is usually planted in " hills," 
that is, a few seeds (grains) are dropped into a slight de- 
pression, and the soil is heaped over them. As the plants 
grow, more and more soil is hoed around the bases of the 
group of plants in a hill. This favors the sprouting of prop 
roots (see page 491), and enables the plants to stand firmly 
against winds. 
When seeds are sown in " drills," they are dropped one 
in a place in a thick or thin line, according to the kind of grain 
and the condition of the soil. Garden seeds are planted in 
drills, also. Drilling is usually done by a machine which can 
be regulated to suit the size of the seed and the depth and 
thickness of the planting desired. 590 
PLANT CULTURE 
Corn must always be planted close enough to secure 
thorough pollination if full ears are wanted, for only those 
ovules develop which have been fertilized by the growth of a 
pollen tube through the length of the long style, the silk. 
As sweet corn does not mature all at the same time, it must 
be planted far enough apart to permit a man to walk be- 
tween the rows with a basket to select the ears which are 
ready to be picked. 
- *t- From Nature Magazine. 
Figure 390. - A Field of Corn. 
The plants are close together. 
Corn planted in hills or in drills far apart grows to large 
size and bears many ears. The object in planting by this 
method is to secure a large yield of grain. 
When the plants themselves are to be used as ensilage and 
a large production of leaves and stalks is the end sought, 
drilling is closer and the stalks grow taller and not so stout. 
In warmer regions where growth is more robust, only the 
leaves and the upper part of the stalks can be used as food for 
cattle, especially after the crop has been planted with a view METHODS OF PLANTING 
591 
to securing many ears. The method here is to plant one 
seed at a time, with distance enough between the plants to 
give each one a chance to grow to the fullest possible size, 
and to produce large leaves which are stripped from the stalk 
at the end of the season after the ears have been gathered. 
Small seeds must be sown in very shallow drills, and larger 
ones in deeper drills or furrows. Some seeds absorb moisture 
readily lying loosely in the soil. Others need to have the 
Figure 391. - Field Sown in Drills. 
earth pressed firmly over them to make absorption of mois- 
ture more rapid and certain. This is often accomplished by 
passing a heavy roller over the soil where wheat, oats, and 
similar grains have been sown in drills. 
Besides knowing how each kind of seed ought to be planted, 
a successful farmer must know what soil is best suited for 
each crop, and also the time of year to plant it. Some seed- 
lings are easily killed by frost, and others are not harmed by 
it. More and more it is becoming necessary for the man who 
raises plants to have a knowledge of plant life in general. 592 
PLANT CULTURE 
406. Necessity of Cultivation of the Soil. - When crops 
appear above ground, many of them, corn for example, must 
be cultivated. In cultivating, three objects are kept in view : 
(1) to keep the soil loose enough for the roots to penetrate it 
easily; (2) to conserve moisture; (3) to kill weeds. 
Humus is the most important part of most soils, since it 
contains raw material in abundance and in a form to be easily 
used by the plants. It also helps the soil to soak up and re- 
tain water much as a sponge does. Proper cultivation helps to 
Figure 392.- A Desert Scene. 
Even with cultivation it is hard to raise crops here.. 
retain water that would otherwise be lost through evaporation 
from the surface, even in soils which contain much humus. 
Irrigation. In the United States most of the cultivated 
land depends on rainfall for its supply of water. In the west, 
however, irrigation supplies the water needed (see page 596). 
In the Old World, irrigation is used to raise the crops which 
support millions of people. 
Thinning and Transplanting. - Crops like garden vege- 
tables will not grow to full size unless each one has sufficient 
room. On the other hand, a greater yield can be secured SOIL EXHAUSTION 
593 
Figure 393. - Nodules on Roots of Bean Plant. 
by transplanting to fill all vacant spaces. Transplanting 
tomatoes, peppers, and other plants grown in greenhouses 
makes it possible to secure ripe fruit earlier than if they were 
first planted out of doors after danger of frost. 
407. Soil Exhaustion. - Every plant that grows in the 
soil takes from it some of its substances - iron, sodium, 594 
PLANT CULTURE 
phosphorus, etc., especially nitrogen, which occurs in the 
form of nitrates. After a few years the soil becomes so lack- 
ing in substances which plants require that a profitable crop 
cannot be grown. Such soil is worn out or exhausted. It 
cannot produce good crops till the lack is supplied. This 
is usually done by adding fertilizer which contains nitrogen, 
the element which is 
used in greatest quan- 
tity. Nitrogen can be 
obtained in several ways, 
chiefly three: (1) by bac- 
teria on the roots of le- 
guminous plants (see 
page 394); (2) by using 
the wastes of animals, 
especially urea, which 
contains it; and (3) di- 
rectly from the air by a 
new process. 
The Nitrogen Cycle.- 
Nitrogen is taken into 
the body of a plant 
through the root hairs, 
and built up into pro- 
tein. These plants are 
eaten by animals, which 
use part of the nitrogen 
to build up their cells 
and get rid of the excess 
through their kidneys, if they are higher animals. When the 
body of any organism decomposes, nitrogen is returned to 
the soil and ultimately to the air again, thus completing the 
" nitrogen cycle." 
The Use of Fertilizers. - The term fertilizer covers sub- 
stances used not only to replace those taken from the soil by 
Figure 394. - Nodules on Roots of 
Peanuts. SOIL EXHAUSTION 
595 
plants, especially crop plants, but also those which are 
added to make the elements already there more available. 
Manure, usually mixed with urine, is rich in organic matter. 
It furnishes material that can be readily appropriated by 
the plants, and also improves the quality of the soil for hold- 
ing moisture. Guano is the refuse of millions of sea birds 
which has accumulated through the centuries. Bone meal 
is a third form of fertilizer which helps to provide nitrogen 
Figure 395. - Desert Land. 
No cultivated crops can grow here. 
for plants. Nitrates dug from the earth in some localities 
is another form in which this element is supplied to soils in 
which it is lacking. Lime, wood ashes, and other substances 
help to overcome the acidity which prevents the growth of 
some plants. Phosphates added to the soil make it possible 
for plants to obtain phosphoric acid, a form of phosphorus 
which can be utilized in building up protein. 
By a newly perfected process, nitrogen can now be taken 
directly from the air and prepared for use as a fertilizer. 
Inasmuch as the quantity in the air is so small - four parts 596 
PLANT CULTURE 
in ten thousand, this can be done with profit only where there 
is abundance of cheap power, usually water power. 
408. Irrigation and Dry Farming. - This is carried on in 
the western United States where the rainfall is so scanty that 
only a few plants especially adapted to extremely dry con- 
ditions (see page 492) can live. This region, although now 
a desert, lacks only water to make it productive. The water 
Figure 396. - Irrigating Ditch. 
for irrigation is secured by building dams in suitable places 
and storing throughout the summer the water from spring 
freshets and melting snow on the mountain peaks. 
Closely connected with this phase of land conservation is 
dry farming, so called. This is possible, as strains of wheat 
and other crops have been found which can grow with much 
less moisture than the ordinary kinds demand. The use of 
such strains makes crops possible on land too dry for farming 
under ordinary conditions. IRRIGATION AND DRY FARMING 
597 
The use of water for irrigation has been practiced from 
very early times, especially in India and Egypt. The methods 
used there, and the results obtained, however, are insignifi- 
cant when compared with modern methods, a good example 
of which we find in the western United States. Immense 
dams are constructed which impound lakes covering many 
acres. The water from these lakes is let out, carried miles 
Figure 397. - Grapes Grown on Irrigated Desert Land. 
through canals and tunnels, and is distributed to crops as 
needed. In this way, nearly a million of acres have already 
been made fertile which before were unable to produce crops 
on account of the absence of rainfall. 
This work in the United States is carried on by the govern- 
ment under the name of reclamation projects. More than 
twenty such projects have been successfully carried out, 
and the land sold to settlers at reasonable rates. More 
than twenty thousand persons are now living in regions 598 
PLANT CULTURE 
formerly unfit for habitation. It is estimated that there 
are about thirty millions of acres that can be reclaimed by 
carrying on this work. 
Any crop can be raised on irrigated land that the character 
of the soil and the climate make possible. All kinds of 
fruits are produced in abundance in some portions of the 
western irrigated lands, on others garden produce is raised, 
and on still others grains and hay. 
Figure 398. - Apricot Tree in Arizona. 
409. Rotation of Crops. - Since no two plants use exactly 
the same amounts of raw materials from the soil, or the same 
amounts of any one substance, farmers plant first one crop 
on a field and then another of a different kind. Instead of 
planting corn, for instance, year after year they vary it with 
some other crop. If a leguminous crop is planted every 
third or fourth year, nitrogen is restored by the bacteria Luther Burbank (1849, still living). Burbank is noted for his 
skill in selecting the most promising young plants, one or two, 
out of hundreds, and carefully rearing them. He has made 
many experiments in plants, producing the thornless cactus, 
stoneless prunes, and numerous other valuable variations. He 
conducts the Burbank Experimental Farms at Santa Rosa, Cali- 
fornia. On this farm as many as 6000 experiments are under 
observation. ENEMIES OF PLANT LIFE 
599 
which are associated with the roots of these plants. (See 
page 594.) 
410. Enemies of Plant Life. - The enemies of plant life 
are weeds, insects, and certain kinds of bacteria and fungi. 
(See page 575.) 
Weeds are plants which interfere with the growth of some 
cultivated plant or crop. Common garden flowers, like the 
poppy and the pansy, sometimes become weeds. Weeds 
deprive other plants of light, moisture, and raw materials 
from the soil. 
One of the purposes of cultivation of most crops is to keep 
the weeds under subjection. Incidentally the soil is loosened 
so that it can absorb and retain water more easily, and admit 
air to the roots of the plants. In fighting weeds a knowledge 
of their habits and of plant life in general enables one to keep 
them under control. In general, the best way to get rid of 
weeds is to keep them from reproducing. 
Insects injure plants in several ways: (1) by eating the 
substance of the plant, especially the leaves and the roots; 
(2) by sucking the juices from the tender parts; (3) by 
carrying the spores of bacteria and fungi from diseased 
plants to healthy ones. 
Bacteria and fungi are the cause of such diseases as smuts, 
rusts, rots, blights, and mildews. Some of these kill the 
plants outright, and others seriously reduce the yield of 
fruit or grain. (See page 580.) 
OUTLINE 
Relation of soil to plants 
Necessary 
For anchorage 
For nourishment 
Moisture 
Food 
Kinds of soil 
Quality 
Alkaline 
Acid 
Texture 
Gravel 600 
PLANT CULTURE 
Sand 
Loam 
Humus 
Clay 
Muck 
Preparation of soil 
Plowing 
Harrowing 
Raking 
Spading 
Seed selection 
Dormancy 
Viability 
Testing 
Methods of planting 
Hills 
Drills 
Furrows 
Need of cultivation 
Objects 
Loosen soil 
Conserve moisture 
Kill weeds 
Irrigation 
Transplanting 
Soil exhaustion 
Nitrogen cycle 
Fertilizers 
Irrigation and dry-farming 
Rotation of crops 
Enemies of plant life 
SUMMARY 
Plants get the raw materials for their food from the air and from the 
water which their roots absorb from the soil. Soil is of use to a plant 
in anchoring it, in retaining moisture, and in supplying part of the raw 
material it needs. Water is taken through the root hairs by osmosis. 
Loam is the best kind of soil to hold moisture and to furnish raw material. 
Soil must be prepared for crops by plowing and other methods. 
The methods of planting crops vary according to the kind of crop and 
the use to be made of it. Crops must be cultivated to conserve mois- 
ture, make penetration by the roots easy, and to kill weeds. Desert 
lands can be made productive by irrigation. 
Every plant that grows takes materials from the soil, which leave 
it poorer for the plants which grow later. Plants are "the only organ- 
isms that can gather the nitrogen from the air and restore it to the soil. 
This is done either directly by bacteria, or indirectly by the death and 
decomposition of the plants themselves or of the animals which eat 
them. The wastes of live animals also help to restore nitrogen to the 
soil. 
The enemies of plant life are weeds, bacteria, fungi, and insects. 
QUESTIONS 
Where do plants obtain the raw materials for making their food? 
In what ways is soil of use to a plant? Name the kinds of soil. De- 
scribe humus. Tell why it is valuable. What methods of planting are REFERENCES 
601 
used? Why are crops cultivated? What is irrigation? What is 
meant by dry farming? How do plants exhaust the soil? How can 
productiveness be restored? How can it be increased even on good 
soil? Describe the "nitrogen cycle." What are the enemies of plant 
life? 
REFERENCES 
National Geographic Magazine. 
Bulletins of the United States Department of Agriculture. 
Bulletins of the Experiment Stations of your state. 
Bergen and Davis, Principles of Botany, pages 500-513. 
Gager, Fundamentals of Botany, pages 520-570. PART V 
GENERAL BIOLOGY 
CHAPTER XXXV 
APPLICATION OF BIOLOGICAL PRINCIPLES 
TO HUMAN INTERESTS 
Take not away the life you cannot give 
For all things have an equal right to live- 
- Dbyden 
411. Interdependence and Interrelation of Living Things. 
- The organic world is so constituted that plants have come 
to depend on animal life for many of their needs. This has 
not always been true, for there was a time ages ago when the 
organic world was made up entirely of plants. As plants 
manufacture food out of the raw elements of nature, they 
are necessary before there can be any general development of 
animals. 
The dependence of animals on plants for their foods has 
been emphasized over and over again in this course. They 
have never been able to live without plants. The very food 
of animals is the plant, directly as in the case of the deer, 
cow, sheep, or indirectly as in the case of the lion, tiger, and 
cat where these animals feed upon other animals that have 
built up their bodies by means of plants. For example, the 
cat eats mice, but the mice eat seeds, roots, and bark. 
Man eats plants directly, such as cereals and bread, as 
well as fruit, while indirectly he uses them in the flesh, 
milk, or butter of animals that in turn build up their bodies 
602 BALANCED AQUARIUM 
603 
by eating plants. The woolen clothes of man come from 
animals, while his linen is of plant origin. He lives success- 
fully because he has learned how to cultivate and use the 
products of the life about him. 
These simple illustrations of the interdependence and 
interrelation of living things will suggest many others to you. 
This balance may be further illustrated in an aquarium or a 
terrarium. 
412. Balanced Aquarium. - In an aquarium we may 
establish a small organic world of animals and plants if there 
Figure 399. - A Balanced Aquarium. 
This is easily made of snails and plants. 
is a proper selection of water plants and aquatic animals. 
The animals will receive oxygen from the water that has been 
enriched with oxygen by the plants in their starch-making; 
and, in turn, the plants will receive some of their carbon 
dioxide from the animals as they carry on respiration. Sup- 
pose in an aquarium our plant is a small water lily and our 
animal a goldfish, then the lily may furnish some of the food 604 
APPLICATION OF BIOLOGICAL PRINCIPLES 
for the goldfish and the growth of the plant will more than 
make good the loss. The oxygen cast off by this plant will 
furnish all of the oxygen the goldfish needs. 
When we get just the right amount of plant life that will 
supply the needs of the fish and just the amount of animal life 
that will supply the needs of the plant, we have a balanced 
aquarium. 
It is not easy to maintain a balanced aquarium because the 
germ life and fungi from the air, water, and larger animals 
and even the plants themselves will multiply rapidly in the 
favorable conditions of an aquarium. This leads to pollution 
of the water and the death of the fish and plants unless it is 
arrested by proper treatment. 
A balanced aquarium need not be the same each time; it 
depends on which organisms you select. An easy combina- 
tion is made of water plants and snails. Frequently the 
minute hydra is a suitable animal. In short, a balanced 
aquarium can be established whenever the conditions of 
nature are closely imitated. 
413. Balanced Terrarium. - Balance in nature is very 
general. What has just been outlined for aquatic organisms 
is equally true of those that live on and in the soil. If you 
desire to make a balanced terrarium a lettuce plant and a 
garden slug may be selected. The slug will eat some parts of 
the leaves of the lettuce, but a strong lettuce plant will grow 
faster than a slug can eat it. The lettuce plant will cast off 
oxygen into the air to add to the amount already there and 
this the slug will use in respiration. The carbon dioxide 
cast off by the snail can be used by the lettuce in starch- 
making. 
Other plants and animals may be used in place of the lettuce 
and the slug. When such selections are made and confined 
in a suitable case, we have a terrarium. If the collection of 
plants and animals is just right in size and number we have a 
balanced terrarium. Again the germs and fungi being always EARTHWORM AND PLANT LIFE 
605 
present may attack the old or injured lettuce leaves or any 
waste matter in the terrarium and thus destroy the balance. 
The balanced aquarium and terrarium are simply con- 
venient ways of illustrating these important relations as they 
exist everywhere in nature. Those of you who can make 
your observations out of doors are fortunate. It is expected 
that you will be on the lookout for these relations wherever 
you are. 
Longfellow wrote a poem as part of the celebration of the 
fiftieth birthday of Agassiz which expresses this attitude. 
" And Nature, the dear old nurse, took 
The child upon her knee 
Saying ' Here is a story-book 
Thy Father has written for thee. 
" ' Come wander with me,' she said, 
' Into regions yet untrod; 
And read what is still unread 
In the manuscripts of God.' " 
414. Animals as Friends and Enemies of Other Animals 
and Man. - Review the Insects and Birds especially in 
this connection. The Bees and Flowers are discussed on 
pages 98-104. 
415. Earthworm and Plant Life. - Many years ago 
Darwin made a very thorough study of the importance of 
the earthworm to plant life. Ever since this time, the earth- 
worm has been studied by all those who are in any way in- 
terested in the interrelations of organisms. If we are to 
gain any adequate idea of just how this relation is brought 
about, it is necessary to examine first of all the general struc- 
ture of this simple organism and see how its digestive organs, 
especially, are adapted to securing their food from the soil. 
The Body. When one examines a living earthworm, the 
head end can be determined as the one which first moves 
forward. Actually there is no head; nor are there special 606 
APPLICATION OF BIOLOGICAL PRINCIPLES 
sense organs. The muscles in the front end are stronger and 
the body rounder than in the back end. The back, or 
dorsal (dor's'l), part of the worm which is exposed to the light 
is darker in color than the rest. This surface is rounder 
than the opposite (under) one which is in constant touch 
with the dirt when the worm is crawling. The flat surface 
upon which the worm crawls is the ventral (ven'tral) surface. 
The body of the earthworm is made up of a number of 
segments (rings) which are marked off by shallow grooves. 
Some of the segments in the front end are larger than those 
that make up the back end, but all are similar in shape. 
Pharynx Muscles 
Stomach -1 niesi in e 
Oesophagus Bloodvessels Herve 
The number of segments depends mostly upon the age of the 
earthworm. It is from 60 to 150 in full-grown worms. 
Life Processes. - While the earthworm has all the life 
processes common to living organisms, the only one we shall 
take up at present is food-taking, as that is the one most 
affecting human interests. The food of the earthworm is 
chiefly the soil in which it burrows. By means of an upper 
lip, which is a specialized anterior segment, and the muscular 
walls of the pharynx, it takes the earth into its body, and 
the muscles of the digestive tube advance the food along 
its course. The soluble and therefore digestible parts are 
absorbed, and the remainder (the greater portion) is passed 
along to the outside. Earthworms are not critical in the 
selection of their food, although they are not entirely with- 
out a sense of taste. 
Figure 400. - Diagram of the Body of an Earthworm. CELLULAR STRUCTURE OF LIVING THINGS 
607 
Economic Importance. - After a rain you have often 
noticed the large number of earthworms crawling on the 
sidewalk or pavement, if you live in small towns or in the 
suburbs of a city; or if you chance to be so fortunate as to 
have a garden spot, you have noticed their openings and 
castings when you examined your garden in the early morn- 
ing. These observations give you some idea of how numer- 
ous earthworms are in fertile soil. 
Darwin estimated from painstaking observations that in 
some of the meadows of England the earthworms brought 
up from the lower layers of the soil from ten to fourteen tons 
per acre. After this large amount of soil has passed through 
their digestive tracts and been deposited on the ground plant 
roots have easy access to it, and are thus supplied with soil 
that contains important substances out of which they manu- 
facture their own food. You have already learned that 
plants exhaust the soil and that it has to be artificially en- 
riched, but for hundreds of years earthworms have been 
slowly making the soil more favorable for plant life. 
As earthworms burrow their way through the soil, they 
leave passages for the water and air to enter, thus again 
assisting plants to grow. The constant plowing of the soil, 
as Darwin termed it, by earthworms has also been an im- 
portant factor in leveling inequalities, and thus has been a 
factor in adding to the attractiveness and beauty of the 
land. 
416. Cellular Structure of Living Things. - Throughout 
this course the same term, the cell, has been found satis- 
factory in describing the minute structure of every living 
thing. We have seen that the root, stem, and leaf of the 
plant are made up of cells. This is true of every plant that 
you have studied, whether large and complex like a pine tree 
or simple like the fungi. Likewise the tissues and organs 
found in animals are composed of cells. In the Protozoa the 
whole life is carried on within a body composed of but aisingle 608 
APPLICATION OF BIOLOGICAL PRINCIPLES 
cell. The human body with its organs and tissues is a 
grouping of cells. 
In structure you have noticed that all cells are much alike. 
They vary in shape and size, giving rise to different kinds of 
tissues and organs. The work which goes on in the living 
protoplasm of one cell is much alike in all. Plant cells 
contain cellulose in their cell walls. This forms the chief 
distinction between an animal and a plant cell, for this 
carbohydrate is not present in animal cells. In some of the 
very simplest organisms, it is difficult to be certain whether 
they are plant or animal, but in the great majority of plant 
cells cellulose is present. 
417. Protoplasm and the Cell. - The active living part 
of all cells is the protoplasm. This is the part that grows, 
moves, and makes the organism alive. In a green plant 
that looks fresh and strong, it is the protoplasm that gives 
it that appearance. When a kitten runs and jumps, it is 
the protoplasm of the cells that is active in reality. When a 
boy or girl skates or swims, we know that good healthy pro- 
toplasm of the cells is at the bottom of such movements. 
So far as we can tell all protoplasm is much the same thing 
structurally and reacts in much the same way whether it is 
in the plant, kitten, or boy. 
When a plant grows, it is adding more cells; when the 
kitten grows, it is adding more cells ; and the man is the boy 
with more cells added and more training and adaptations 
acquired. Nowhere in the animal or plant kingdom can 
we get away from the fact that the foundation of all organic 
structure is the cell with its living protoplasm. As a brick is 
a unit in a great building, so each cell is a unit in the huge 
tree by the roadside, the elephant in the zoological garden, or 
in a man. As living things grow older certain cells become 
less active, until in old age the tissues have ceased to grow. 
Finally, death is due to the failure of certain cells to do their 
part as they have been doing. This is the reason that the LIFE FUNCTIONS 
609 
expression " We are as old as our cells " is frequently used. 
It means that we are healthy when our cells, all of them, 
are doing their normal, regular work. Healthy cells make 
a healthy body. 
418. Life Functions. - The principal functions of all 
organisms, animals, man, and plants, are sensation, motion, 
respiration, food-taking, digestion, absorption, circulation, 
assimilation, excretion, and reproduction. These have all 
been fully explained as you have studied animals, plants, and 
man. They should be reviewed again for the sake of com- 
parison, and for this reason only a brief summary of each is 
here given. 
(a) Sensation. - We all know that we have five sense 
organs, and students of physiology tell us that we have many 
more, but no matter how many there are, all require special 
cells to respond to the various stimuli such as light, sound 
waves, heat, cold, sour taste, etc. Such cells bring man in 
contact with his environment and help him to understand it. 
The brain of man is more highly specialized than that of any 
other animal, and his sense organs, taken as a whole, are 
better developed than those of any other living thing. 
Most animals have sense organs, though they are simpler 
than those of man. But even animals without sense organs 
or a definite nervous system respond to heat and cold, light 
and dark because of the general sensitiveness or irritability 
of their protoplasm. Plants without nerves show many 
responses to light and dark, heat and cold. 
(6) Motion. - The movement in living things which you 
have observed is unlike the motion of water or wind. The 
power for motion in organisms comes from energy stored 
within their own bodies. Animals are more active than 
plants and consequently utilize more energy. They change 
more potential energy to kinetic energy than do plants. 
The simplest organisms move only a little, but higher 
organisms, especially man, are capable of remarkably varied 610 
APPLICATION OF BIOLOGICAL PRINCIPLES 
motion. The greater the complexity of structure, the more 
diversified the movements and the greater the division of 
labor among the parts. 
(c) Respiration. - Oxygen furnishes a necessary amount 
of energy to all organisms. The simplest animals absorb it; 
others have more complicated adaptations for respiration. 
Animals that live on land have special organs, the lungs, that 
are adapted to taking oxygen from the air; while aquatic 
animals, like fish and crayfish, have gills that are adapted to 
taking oxygen from the water. The thin skin covering the 
body of the earthworm acts like a lung in that oxygen passes 
through it and into the blood. Plants have their leaves 
modified by stomata, and through these oxygen passes into 
the plant. Under some conditions the stems of plants take 
up oxygen. Aquatic animals and plants take up their oxygen 
through their cell walls. 
(d) Food-taking. - Animals require food that has been 
built up into proteins, fats, or carbohydrates. In the pro- 
tozoan this food enters the food-vacuoles, and in the higher 
animals and man it is taken into the digestive canal. Plants 
require food just the same as animals. They simply need 
less. There is apt to be some confusion in comparing plants 
and animals in regard to food-taking. All green plants 
manufacture food, which is either utilized by the plant or 
stored in root, stem, leaf, or seeds. Such stored food is 
eaten by animals. The fundamental need for food is the 
same in plants and animals. The plant has first to manu- 
facture food before it can be utilized. Of all animals, man 
uses the greatest variety of food. 
(e) Digestion. - The food in the stomach of animals and 
man is acted upon by an enzyme secreted by living cells 
lining the digestive cavity. Different enzymes grown in 
the pancreas produce further changes in the food after it 
reaches the intestine. The action of the several digestive 
enzymes is to reduce the foods to solution, which is digestion. LIFE FUNCTIONS 
611 
The parts of the food that are thus digested pass by osmosis 
into the blood. The same principles apply to the digestion 
of the food in the food-vacuole of a paramecium. The 
stored foods in a plant also must be digested before the plant 
can absorb them. Digestion, then, the reducing of foods to 
solution, is the same process in all organisms. 
(/) Absorption. - This is the taking of the foods in solution 
into the blood of animals or into the veins of plants. After 
it has entered the blood or sap it can be carried to all parts of 
the body of the animal or plant. 
{g) Circulation. - The carrying of food in solution to all 
of the cells of an organism is circulation. Such foods cir- 
culate through the cytoplasm of paramecia, for example, 
through the blood of animals and through the sap of plants. 
(h) Assimilation. - Every cell in an organism must take 
the food that it needs from the blood or sap and build it into 
living protoplasm. This is assimilation. 
(i) Excretion. - The energy used by organisms in their 
several activities results in the formation of various wastes. 
These wastes usually take the form of a gas, carbon dioxide, 
given off in respiration by animals and plants, or a liquid 
when discharged from the sweat glands or kidneys. The 
simple contractile vacuole in the paramecium assists in 
removing wastes, while the earthworm possesses numerous 
simple excretory tubes (nephridia) that take the place of 
kidneys in higher animals. 
(j) Reproduction. - The unicellular plants and animals 
reproduce in a very simple manner by fission (division). In 
multicellular organisms reproduction begins in a single cell, 
the germ cell. This germ cell has the power to carry on a 
program of development that varies but little for all eggs of 
one kind. The fish egg and the frog egg look much alike, 
but each follows its own individual order of development until 
the adult stage is reached. There is no mistake, and the 
development is never interrupted in normal growth. There 612 
APPLICATION OF BIOLOGICAL PRINCIPLES 
can be no pause without disaster to the life of the forming 
organism. An egg may be kept before starting to hatch as 
we do with hen's eggs, but once started it must continue. 
The egg cell of plants and animals must be fertilized. This 
process is accomplished through the union of the male germ 
cell with the egg germ cell. 
In all of your study about reproduction in plants, animals, 
and man, you must remember that a new organism can come 
into being only from living germ cells. You cannot cut off a 
leg from the frog and grow a new frog from it, nor can you cut 
any of the higher animals in two and have each part live. 
This important fact should help you to correct the common 
misapprehension that worms can be grown from horse hair 
or that frogs rain down. 
419. Division of Labor. - Nearly all of the organisms that 
you have studied were composed of many parts, each of 
which did a particular thing that was important to the life 
of the organism. (Stem, leaf, root with all of their special 
tissues, each had its special function to perform.) The 
skeleton, nervous system, and digestive organs of the frog 
or man had also a particular work to do. In contrast to this 
division of labor in structures of greater complexity stand 
the more simple organisms of plant and animal life, for 
example, fungi and bacteria, and the unicellular paramecium. 
Here although all the life processes are carried on, they are 
performed by the whole organism. 
In some organisms, the cells are alike in form and function, 
but in others, we find that a few cells have been changed in 
shape in order to perform better the special work of repro- 
duction. This change is the first step in the division of labor. 
This is well shown in the higher animals, where certain 
cells are grouped together for a given work. The digestive 
system contains cells which work to make solutions of the 
food eaten. These solutions nourish the whole body, not 
the cells of the digestive tract alone. Certain other cells GONIUM 
613 
are modified in such a way for secreting and holding lime 
that they form bones by which the whole body is benefited. 
Some cells are grouped to form muscles to be used in 
securing food and in enabling animals to escape from their 
enemies. Other cells are for the purpose of conveying and 
interpreting impressions, so that the animal may hear the 
approach of an enemy, or detect the presence of food. It is 
largely the carrying out of this " division of labor " that 
tells us the rank of an animal or a plant in biological classifi- 
cation. 
In the business world we have a somewhat similar division 
of labor. Years ago the cobbler made all the parts of a shoe. 
In our large shoe factories to-day we find no one man making 
an entire shoe. One man runs the machine that cuts the 
leather and he does no other part of the work. He may have 
been a cutter twenty years, and he works rapidly and ac- 
curately. Another man runs the machine which sews 
uppers to the soles. He, too, is a rapid and skillful worker. 
Other men have their special lines of work to do. In the 
end they produce more shoes and better shoes than this 
same number of men could if they were all cobblers and each 
finished his product. 
Division of labor increases the more complex the structure 
becomes. This fact can be illustrated by studying several 
organisms of increasing complexity, gonium, volvox, sponges, 
and hydra. This idea of division of labor in organisms can 
be shown just as well from plants as from animals, and those 
teachers who do not wish to use the sponge and hydra will 
find that marchantia, mosses, and ferns show the gradual 
formation of root, stem, and leaves as well as the differen- 
tiation of tissues and reproductive organs. 
420. Gonium. - Gonium is an animal made up of sixteen 
separate cells held together by a mucilage-like secretion of the 
cells. Each cell works independently in getting food, respir- 
ing, giving off waste, and in reproduction. The colony moves 614 
APPLICATION OF BIOLOGICAL PRINCIPLES 
by lashing the water with long protoplasmic threads (flagella), 
two of which project from each cell. The advantage in 
rate of movement resulting from the union of cells is illus- 
trated in rowing. Eight men 
in a large rowing shell can go 
faster than one man in a 
single, small shell. In re- 
production, the sixteen cells 
fall apart, and each one 
grows into a new colony. 
421. Volvox. - Volvox is 
a colony of hundreds of tiny 
green cells embedded in a 
hollow gelatinous sphere. 
Each cell has two flagella. 
For a time all the cells are 
alike and share equally in the work of the colony. But 
in reproduction only a few cells take part. In the simplest 
method, a few cells grow large and escape into the hollow 
sphere. There, they divide and grow into new colonies. 
Finally, the mother colony 
breaks, and the daughter colo- 
nies escape. 
The more complex method is 
like the reproduction of higher 
animals. Certain cells in the 
colony grow large and escape 
into the hollow sphere. They 
are the egg cells. Other cells of 
the colony enlarge and divide 
into large numbers of slender, 
free-swimming cells called sperm cells. The sperm cells es- 
cape into the hollow sphere and swim about. One sperm 
enters an egg cell and unites with it, forming a single cell, 
the fertilized egg cell, which can develop a new colony. 
Figure 401. - Gonium. 
Figure 402. - Volvox. SPONGES 
615 
422. Sponges. - Sponges are simple animals composed 
of many cells. In them we find division of labor carried out 
in a more complex way than in 
gonium and volvox. Simple 
sponges have a body in the form 
of a hollow cylinder. Water 
enters through the sides of the 
body and passes out through 
a hole in the top. A simple 
sponge, called Grantia, grows in 
salt water attached to docks or 
other objects submerged along 
the seashore. On examination, 
it is observed that grantia is less 
simple than volvox. 
Structure. - Grantia is com- 
posed of three layers of cells 
which show division of labor. 
The inner layer is called the 
endoderm (en'db-derm). It con- 
sists of cells provided with flagella 
which, by their movement, produce a current of water through 
the central cavity. The water enters through the holes in the 
sides (inhalent pores) and is forced out through the opening 
at the top pore (exhalent pore). 
The water contains food particles 
which the cells of the endoderm 
have the power to take in and 
digest. The food solution is 
passed to the other cells in the 
sponge body by the process of 
osmosis. This is a process in 
which gases or liquids of unequal 
densities, separated by a plant or animal membrane, tend to 
mix and become alike. 
Figure 403. -A Simple Sponge. 
Figure 404. - Sponge Spicules. 616 
APPLICATION OF BIOLOGICAL PRINCIPLES 
1 hus the food digested is passed on and nourishes the cells 
of the middle and outer layers. The cells of the middle 
region form spicules (spic'uls) of lime (Figure 404) that pro- 
ject through the other layers and strengthen the whole body. 
The outer layer or ectoderm (ek'tb-derm) serves as a protec- 
tive layer and with the 
help of the spicules gives 
definite shape to the 
body. 
Reproduction. - At 
certain times of the year 
the sponge reproduces by 
means of two kinds of 
cells (eggs and sperms) 
developed in the middle 
layer. A sponge may 
develop both eggs and 
sperms, but usually de- 
velops only one kind at a 
time. Cells from the 
middle layer move in be- 
tween cells of the en- 
doderm and grow large 
and round. These are 
the eggs (female cells). 
Other cells move into the 
endoderm layer and divide into many small ciliated cells (the 
sperm or male cells). The sperms are set free and escape into 
the water of the central cavity and out from the body of the 
parent sponge. A sperm enters the body of another sponge 
and when it finds an egg, fuses with it, thus forming the 
fertilized egg. The fertilized egg then begins to grow, and 
after a definite period breaks away from the parent, moves 
about for a time, and then settles down, attaches itself, and 
grows into a mature sponge. The immature sponge has the 
Figure 405. - A Branching Sponge. HYDRA 
617 
power of locomotion, but the mature form has lost this power. 
Nevertheless the sponge is an animal. 
Reproduction that comes about through the fusion of an 
egg and a sperm is called sexual reproduction. The other 
method of reproduction, called asexual reproduction, also 
occurs among sponges. By this 
method, sponges form little buds 
or branches which develop into 
new sponges. 
423. Hydra. - The hydra is an 
interesting fresh-water animal 
about a quarter of an inch in 
length which carries the division 
of labor a step farther. Its body 
is shaped like a little cylindrical 
bag with only one opening, the 
mouth, which is surrounded by a 
few, usually six, delicate, thread- 
like arms called tentacles (ten'ta- 
kls). The body is composed of 
three layers, the outer layer, 
ectoderm; the middle layer, the 
mesoglea (mes-d-gle'a: Greek, 
mesos, middle; gloios, glutinous 
substance); and the inner layer, 
endoderm. 
Each layer does some particular 
work for which the others are 
not fitted. For example, the outer layer contains cells 
which are especially sensitive to stimuli and many modified 
muscle cells that enable the animal to move about. The 
inner layer contains cells provided with flagella which catch 
the food particles for the inner cells to digest. The muscular 
action of the outer layer moves the entire animal. The sensi- 
tive cells enable the animal to recognize its prey. The food 
/tentacle- 
mouth 
bud 
young 
sperms 
digestive 
cavity / 
egg I 
basal disk 
Figure 406. - Diagram of 
Body of Hydra. 618 
APPLICATION OF BIOLOGICAL PRINCIPLES 
digested by the inner layer is used by all the cells of the body. 
Thus we see an advance in the division of labor over that 
shown in the sponge. We shall observe a still greater in- 
crease in division of labor as we study higher animals. 
Tentacles are hollow, finger-like branches connected with 
the body cavity. They are provided with stinging cells 
which help the hydra to capture living water fleas and the 
like. These stinging cells 
have darts which are 
automatically discharged 
when the tentacles come 
in contact with little ani- 
mals. The darts poison 
the prey and render escape 
impossible. The tenta- 
cles surround the food 
and carry it to the mouth, 
which opens directly into 
the food cavity. 
The united cells in the 
hydra are connected with 
one another through the 
cell walls. In the higher 
animals we shall find that 
connections between cells 
are made by means of 
nerve cells. The develop- 
ment of a nervous system only carries out division of labor 
to a greater degree. 
Locomotion. - The adult hydra is usually found attached 
as in Figure 407. In this condition the only movements 
possible are such as take place in the expansion and con- 
traction of the whole body. The tentacles wave about 
in the water, and as the hydra expands, the body may move 
first in one direction, then in another. In this sense the 
Figure 407. - Hydra. HYDRA 
619 
hydra does not move about as does a grasshopper or a para- 
mecium. At infrequent intervals, however, the hydra 
detaches itself and moves from place to place by attaching 
the tentacles, then the base, then the tentacles, much like a 
boy turning handsprings. 
Nutrition. - The hydra feeds almost entirely upon minute 
animals. The forms that furnish the greater amount of 
their food are shown in Figure 407. These animals belong 
to a much higher group of animals than the hydra; namely, 
the Crustacea, the group to which the crayfish and crabs 
belong. These animals which have an exoskeleton like in- 
sects are rendered inactive by the stinging cells on the ten- 
tacles. The paralyzed animal is then brought to the mouth 
by the tentacles, Figure 406, and swallowed. Within the 
body, the nutritive parts are digested by enzymes as in other 
animals and absorbed, passing by osmosis to all the cells. 
The indigestible skeleton of the animals eaten is cast out 
through the mouth. 
Respiration and Excretion. - By osmosis, oxygen is ab- 
sorbed from the water by the cells of the ectoderm. The 
water that enters the mouth carries oxygen, and by osmosis 
it is absorbed by the cells of the endoderm. At the same 
time the carbon dioxide from the cells is thrown off into the 
water. 
Irritability. - The hydra is able to appreciate a variety of 
different kinds of stimuli such as jars, a moving animal, or an 
enemy. It is able to contract, expand, and move the ten- 
tacles in such a way as to bring food to the mouth, although 
it does not possess nerves or a brain. When a special study 
of the structure of the hydra is made, nerve cells are found 
which assist it in responding to stimuli. In the Protozoa 
there are no special nerve cells, but the hydra shows the 
beginning of the formation of a nervous system. 
Reproduction. - The hydra reproduces both sexually and 
asexually. In sexual reproduction eggs and sperms are 620 
APPLICATION OF BIOLOGICAL PRINCIPLES 
produced by the ectoderm cells. The sperm cells escape into 
the water and, like sperm cells of all other animals, have the 
power of locomotion. The fusion of the egg cell and a sperm 
cell starts growth, which results in the division of the egg cell 
into many other cells. Hydras also reproduce asexually by 
budding. The buds soon separate from the parent and begin 
an independent life. Like the developing sponge, the develop- 
ing hydra grows until it finally becomes a fully formed hydra. 
As the layers in the body of the hydra become more distinct, 
the division of labor is more marked. 
From the simple layers of tissue, we pass to the formation 
of organs, for which the earthworm previously described is a 
good illustration. The earthworm is much simpler than a 
crayfish, but in turn the crayfish does not have a well-devel- 
oped head such as the fish or frog. Thus you can trace a 
greater division of labor with the complexity of structure as 
you pass from the simpler to the higher animals. 
424. Oxygen, Carbon, and Nitrogen Cycles. - In our 
study of the apple tree, we learned that eventually the tree 
grew old, decay set in, and the rotting stump was all that was 
left. After a while even this stump disappeared and the 
entire tree had vanished. The same set of events occurs in 
the life of all organisms. Energy in the form of food and 
oxygen (which is in the form of a compound) is taken up and 
becomes a part of the bodies either temporarily or for some 
considerable time. 
Life has thus been utilizing energy since it first began, and 
it will continue to do this as long as there is life. At first 
thought, one might say that there must come a time when 
some at least of the necessary substances will become ex- 
hausted and life will have to cease. This used to be believed, 
but ever since men have known about the work of micro- 
organisms and the manner in which oxygen is used, the theory 
that life will have to stop because of the lack of some of the 
needed compounds has been denied. OXYGEN, CARBON, AND NITROGEN CYCLES 
621 
Oxygen. - We shall first review the cycle of oxygen. This 
important compound is taken into the body and takes part in 
oxidation. There results a waste product, carbon dioxide. 
Carbon dioxide is taken up by the green plant and the carbon 
becomes a part of the starch, while the oxygen is set free and 
escapes into the air ready to be used again by some organism 
in respiration. Oxygen can go through this series of changes 
an endless number of times without losing any of its proper- 
ties. It is thus said to go in a cycle or circle in its relation to 
living things. 
Carbon. - The carbon which is a part of starch remains in 
this food until some organism utilizes it. The organism may 
set it free as a waste product in carbon dioxide, to be later 
built up into starch in photosynthesis. The scientists who 
have tried to discover just which elements are in living pro- 
toplasm all agree that carbon is present in large amounts. 
It constitutes about 72 per cent of our own bodies. The car- 
bon that is a part of the living protoplasm remains in this 
relation for an indefinite length of time, being finally released 
when the protoplasm dies. In this way it differs from 
oxygen. There is thus a carbon cycle just as there is an 
oxygen cycle. 
Nitrogen. - Nitrogen is another important element found 
whenever organic matter is analyzed. Living things cannot 
utilize nitrogen unless it is in a complex form. Animals 
require proteins which are very complex. These proteins 
in turn are manufactured by green plants. When an organ- 
ism dies the nitrogen compounds are made simpler by the 
action of bacteria (page 390). Green plants take up nitrates 
(simple nitrogen compounds) and store the nitrogen away in 
proteins. Undoubtedly many of the compounds built up 
by the animal and plant would automatically break down 
after death, yet bacteria hasten the process as they feed on 
them. In this process of decay, the compounds are almost 
completely broken down and the result is that the nitrogen 622 
APPLICATION OP BIOLOGICAL PRINCIPLES 
has now become so simple (simpler than nitrates) that green 
plants cannot utilize it. ♦ 
The group of bacteria (denitrifying bacteria) whose activi- 
ties are spent in changing nitrates into gaseous nitrogen allow 
the nitrogen to escape into the air, thus putting it beyond the 
reach of green plants. Then there come the nitrogen-fixing 
bacteria, which rescue this gaseous nitrogen from the air and' 
unite it with other elements suitable for green plants to use. 
The nitrogen cycle is thus very complex in comparison with 
the oxygen cycle, and it is no wonder that the complete story 
remained untold for many years. Scientists had to learn a 
great deal about the life of bacteria before they understood 
how important a part they play in the life of all of the higher 
organisms, including man. 
OUTLINE 
Interdependence of living things 
Plants on animals 
Animals on plants 
Illustrations 
Balanced aquarium 
Balanced terrarium 
Animals as friends and enemies 
Earthworm 
Life processes 
Economic importance 
Cell structure 
Protoplasm 
Life functions 
Sensation 
Motion 
Respiration 
Food-taking 
Digestion 
Absorption 
Circulation 
Assimilation 
Excretion 
Reproduction 
Division of Labor 
Gonium 
Volvox 
Sponges 
Structure 
Reproduction 
Hydra 
Life processes 
Cycles 
Oxygen 
Carbon 
Nitrogen 
SUMMARY 
Animals, plants, and man live in close relation to one another. Both 
man and animals are dependent on the work of the green plants. There 
is a constant struggle going on in nature between the several kinds of QUESTIONS 
623 
organisms that try to live in any given pond or on any bit of land. 
While they struggle for a place to live and food to eat, they in turn 
contribute necessary substances to one another. Even the insignificant 
earthworm has been an important organism in increasing the pro- 
ductivity of the soil. The protoplasm of all forms of life is similar and 
confined in similar cells. Within these cells takes place all of the activity 
of organisms which we know as life functions. In order that these 
life functions may be carried on better, a marked division of labor is 
evident as we pass from the lower to the higher organisms. Organisms 
utilize energy in living but there is no danger that the supply will ever 
become exhausted, because it has been shown that the elements of which 
the compounds yielding energy are composed pass in a cycle assisted 
by the work of microorganisms, and without which the various cycles 
would be impossible. 
QUESTIONS 
Explain how organisms are dependent on one another. How are 
they beneficial? How harmful? What is a balanced aquarium? A 
balanced terrarium? Do you think that these conditions exist in 
nature? How does the earthworm help plant life? Is its digestive 
system adapted to this work ? Explain. Just how do bees help flowers ? 
How do some insects injure plants? Define a cell. What is the dif- 
ference between a plant cell and an animal cell? Name the life func- 
tions of organisms. Do these apply to man? Which organisms help 
you to understand how the plan of division of labor began ? Is it a good 
thing? Illustrate in animals and plants. Explain the carbon cycle. 
The nitrogen cycle. CHAPTER XXXVI 
HEALTH AND CONSERVATION 
Nor love, nor honor, wealth nor power 
Can give the heart a cheerful hour 
When health is lost. Be timely wise; 
With health all taste of pleasure flies. 
- Gay 
The progress of science has indicated very clearly that 
there is an unnecessary waste of human life, and our course 
of study has revealed something of the devastation that comes 
from communicable diseases - all of which are preventable. 
A similar destruction and prodigal waste has taken place in 
our biological resources. 
Several agencies have been set up which aim to substitute 
prevention and conservation for this loss. A study of health 
agencies and conservation of biological resources are taken 
up in this chapter. 
425. Health Activities. - In our study of bacteria, we 
came to realize that these minute organisms are the cause of 
many communicable diseases, and, when we review the relation 
of the protozoa to our welfare, we realize that these two classes 
of germs are the main source of disease. If we are to keep 
ourselves well and help to prevent these diseases, we must 
observe the laws of hygiene and quarantine. 
So few people have realized the importance of the facts 
which you have been studying that laws have been passed 
regulating our activities. It is important that you should 
first understand what health agencies exist in your munici- 
pality and then give your support to them. But local health 
regulations are often inadequate to govern a situation, and 
624 MUNICIPAL HEALTH AGENCIES 
625 
the entire state or nation must assume control. For this 
reason we have state and national health laws. 
Special foundations have been instituted by private in- 
dividuals who have given large sums of money to further 
the work of scientists in the study of the causes and pre- 
vention of disease. The results of any discoveries are given 
to the public, where they may be of immediate benefit to 
the people. What are some of these important health 
agencies ? 
426. Municipal Health Agencies. - The civic authorities 
of towns, villages, and cities are charged with the duties of 
administering the laws and caring for the well-being of the 
people. A certain amount of the taxes are set apart by the 
civic authorities to care for the health of the people. 
Our streets and parks are improved at great cost. These 
have to be protected and repaired. The care of the streets 
is usually under a separate department whose business it is 
to see that they are cleaned and flushed and to remove dirt 
and decaying matter, which are a source of danger to health. 
Public health activities usually center in a public health 
officer who is charged with enforcing health regulations, 
supervising school hygiene and quarantine. The laws which 
govern these several activities are made in most instances 
both by the state and by the municipality. 
In a large number of the cities and counties of New York 
State there are public health laboratories. In order that 
you may have some idea of the kind of work that goes on in 
such laboratories, the following summary is given. In the 
annual report of one city of New York State 10,872 diph- 
theria cultures were made; 399 examinations of blood and 
1,293 cultures of sputum of patients suspected of having 
tuberculosis; 3,073 chemical and bacteriological analyses 
were made of milk and 213 of cream. The drinking water 
of this city received repeated study, as the 630 tests for 
Bacilli coli indicate. There were 176 inoculations for ty- 626 
HEALTH AND CONSERVATION 
phoid and 973 miscellaneous studies. This does not include 
the work done by the public health division, which has charge 
of vaccination against smallpox. Not only were the dairies 
near the city inspected, but more distant dairies were regu- 
larly examined. 
427. Pure Water Supply. - Plenty of pure water for 
drinking and cooking is indispensable to man. The neces- 
Figure 408. - One of New York City's Reservoirs. 
sity for disposing of sewage has made this problem increas- 
ingly difficult. Sewage-polluted water is never entirely 
safe for drinking. The two must be kept separate. This 
is the main reason why so much money has to be spent to 
bring drinking water to our cities, and this is the reason 
why so much care is taken to prevent this same drinking 
water from becoming contaminated. Some of the smaller 
towns have not yet come to appreciate the value and im- 
portance of having pure water to drink. The result is fre- 
quent epidemics of sickness. PURE WATER SUPPLY 
627 
In Figure 408 is shown a model reservoir. It is well lo- 
cated and all possible sources of surface drainage have been 
eliminated. In Figure 409 is shown a reservoir in which the 
conditions are the reverse. The water is stored in a place 
surrounded by residences and swampy ground on the left 
of the photograph. The open channels in the grass are 
Figure 409. - A Poor Reservoir. 
Note the open stream that empties into the main body of water. The 
impure water of the Erie Canal drains into this open stream. 
streams that empty into the water of the reservoir. One of 
these is supplied from the overflow of water of the Erie Canal. 
This alone is sufficient explanation of why there have been 
frequent epidemics in the town that has this water supply. 
What are the conditions surrounding the water supply of 
your home? 
Cities and villages need more water than old-fashioned 628 
HEALTH AND CONSERVATION 
wells can furnish. To secure this increased supply, lakes, 
rivers, or a group of wells are drawn upon. When a supply 
of water is brought to a village or city from lakes or rivers, 
the health authorities pay particular attention to the purity 
of the water. If it is likely to be polluted, certain germicides 
are forced into the water to destroy disease germs. If it is 
too hard, that is, contains too much lime, it may be softened 
by adding materials which precipitate the lime. If it is 
deficient in iodides (iodine compounds) it will tend to pro- 
duce goiter among those who drink it. Iodides may be 
added in small amounts so that no danger from goiter remains. 
Regulations are enforced by proper officials so that the 
water may not be polluted at its source. Some large cities 
buy the land adjoining the lakes and reservoirs and remove 
all cottages and residences as a means of preventing con- 
tamination of the water. 
428. Proper Sewage. - In every town and city where a 
general water supply is established, it is necessary to provide 
means for the removal of the waste water. This water comes 
from homes, places of business, and various manufactories. 
Not only the wastes from the human body but also from the 
street washing, the waste products of various factories, and 
the annual rainfall and snow are all added to the waste waters 
of a city or town. Such water is known as sewage. 
It is now known that there is an average of one hundred 
gallons of sewage daily for every inhabitant of a city. The 
daily sewage from homes averages about thirty gallons for 
each member of a family; but when we add the street flush- 
ing and wastes of various manufactories the total amount 
per capita is not far from the larger amount named. Thus 
in a city of 100,000 inhabitants, there will be about ten 
million gallons of sewage a day. What must be the daily 
average of sewage in your city? 
Disposal of Sewage. - The question of what shall be done 
with all this vast amount of sewage is one of the most diffi- W. T. Sedgwick (1855-1921), a member of the Department 
of Biology and Public Health at the Massachusetts Institute of 
Technology for thirty-eight years, devoted his training and energy 
largely to making cities healthful. He was one of the foremost 
American biologists in making investigations upon milk, water, 
sewage, and epidemics of typhoid fever, and in showing how 
to apply these technical studies to human welfare. 
He was one of the first to study the bacteria of the air, and 
his work on the " Principles of Sanitary Science and Public 
Health" (1902) was an important contribution to public health 
education. In addition to this marked service to his countrymen, 
he devoted his life to teaching biology and sanitary science and 
to training biologists and public health workers. 
One renders a great service to his age who leaves the world 
safer to live in than he found it. PROPER SEWAGE 
629 
cult that cities are trying to solve. The cities that are lo- 
cated on or near the ocean or Great Lakes let their sewage 
run into them. Those that are built on a stream or river 
empty into this small body of water and the town or city 
farther down the stream does the same. Where does the 
sewage of your city or town go? 
Stream Purification. - Some recent studies made under 
the direction of the Massachusetts Institute of Technology 
show that there are a number of biological factors that assist 
in the purification of sewage-polluted water. These are a 
number of organisms that feed upon the organic matter that 
is suspended in the water. The first living things to be found 
where the water is most polluted are bacteria. As the sew- 
age empties into the stream it is rich in food for bacteria 
and they become very numerous. As they feed upon this food, 
it is broken up into simpler chemical bodies and the water 
becomes clearer. A little farther away from the mouth of 
the sewer are found numerous protozoa that feed upon 
these bacteria and thus tend to remove them from the water; 
while still farther down the stream are to be found numerous 
tube-bearing worms that in turn feed upon the protozoa. 
If the water is now examined, it is found to be much clearer, 
for most of the sediment has either settled to the bottom 
or been destroyed by these several organisms. Neverthe- 
less such water as this is not fit to drink. 
Septic Tanks. - We take our drinking water from lakes 
and rivers, but strangely enough we pour our sewage into 
these same bodies of water. Large septic tanks are employed 
in some cities and villages, where all the sewage is allowed 
to ferment, with the result that disease germs are destroyed. 
The outlet from these tanks takes away the liquid part and 
pours it into lakes and rivers with practically no danger to 
public health. The solid portions from the tanks makes 
good fertilizer for depleted soils. In time we shall come to 
prize our public health so much that we will not allow any 630 
HEALTH AND CONSERVATION 
sewage to pollute our rivers or lakes. This will come only 
with a keener sense of responsibility among all people for the 
preservation and conservation of health. 
429. Supervision of the Milk Supply. - Intimately con- 
nected with our water supply is our milk. If milk cans and 
milk bottles are washed in impure or polluted water, each 
can or bottle is likely to hold some of the disease germs. 
When milk is placed in these containers the germs multiply 
rapidly, especially if the milk is warm, because the milk 
furnishes food for these bacteria which grow best in a warm 
temperature. Under such conditions the milk soon becomes 
a menace to the health of all of those who use it. A pure 
water supply is a good start towards a clean milk supply. 
If milk is produced by dirty or diseased cows or handled 
by dirty or diseased people, it will contain disease germs and 
become a menace to health. For these reasons public health 
authorities examine and test milk containers and the cow 
stables, as well as the health of the cows and the health of the 
men who handle the milk. Sometimes, through careless- 
ness or accident, milk may be contaminated and not be de- 
tected by the inspectors of the health department. If all 
the milk is treated as if it were contaminated, by heating to 
a temperature a little below the boiling point for a half hour, 
practically all disease germs are destroyed and the food value 
of the milk remains unchanged. This treatment is pasteuri- 
zation. It is recommended for all milk, the purity of which 
is in doubt. 
430. Care of Other Foods. - The care of food is extremely 
necessary in preserving our bodily well-being, for the same 
germs which cause disease when taken into the body live 
and grow on food. Fruit and candy exposed to dirt and 
dust or to flies are a menace to health. Such fruits as straw- 
berries, blackberries, peaches, figs, or dates should be kept 
covered; and candy should be protected by cases or boxes. 
More and more health regulations are being formulated to MUNICIPAL QUARANTINE 
631 
protect our food as it is being transported from the place 
of production to the consumer. We used to see the meat 
companies transporting carcasses uncovered through our 
streets, and in many places protection is still inadequate. 
It is not fair to lay all of the responsibility upon those 
who handle our food before it comes to our homes. The 
same hygienic precautions must be taken by us. One 
method of keeping the bacteria on food from growing is by 
proper refrigeration. The temperature of a well-cooled 
refrigerator does not destroy the germs, but makes them in- 
capable of growth. If food is taken from the refrigerator 
and allowed to stand for a time, the bacteria will at once 
begin to grow and cause the food to spoil. If such food is 
eaten an intestinal disturbance usually results. 
431. Municipal Quarantine. - Our public health officials 
must not only supervise the several activities which have 
just been described, but it is their duty to see that the quar- 
antine laws are obeyed. Certain diseases like measles, 
whooping cough, diphtheria, and scarlet fever are contagious. 
Persons who have such diseases may communicate them to 
healthy people by transferring the germs from their bodies. 
To prevent the spread of these diseases quarantine regula- 
tions are established so that healthy people are not brought 
in contact with those who are sick. Patients may be quar- 
antined in one room of the house. 
Nurses and physicians who are careful attend patients 
who have these diseases and do not contract them, nor do 
they carry them to other healthy people. The chief danger 
comes from those who are inexperienced and from those who 
do not understand how contagious diseases are spread. This 
is so important that we restate that the germs must be con- 
veyed from the patient to the healthy person. This may be 
done through the air, which becomes infected from the dis- 
charges from the patient's nose or mouth when he sneezes 
or coughs. Contagion may come through soiled linen, such as 632 
HEALTH AND CONSERVATION 
handkerchiefs or towels that have been used by the patient; 
or it may be conveyed by kissing or handling a patient. 
Nurses who care for persons suffering with a contagious dis- 
ease are very careful to wash their hands in an antiseptic 
solution in order that they may kill all germs that are on 
them. 
432. General State Supervision. - Each state maintains 
a health department which administers health laws affect- 
ing the whole state. In some states this has become an in- 
stitution of far-reaching importance as measured by the 
decrease in death rates over the whole state. When a village 
or a city is temporarily afflicted with an epidemic the spe- 
cialists and nurses from the state health department co- 
operate with the local authorities. 
In addition to this valuable work many state health de- 
partments produce serums and vaccines for the use of citi- 
zens. These serums and vaccines are used successfully to 
combat diphtheria and to prevent typhoid fever. They are 
difficult to produce and are correspondingly expensive. 
New York State Department of Health. - This department 
has been subdivided into proper separate bureaus. These 
divisions are: Sanitation, Laboratories and Research, Vital 
Statistics, Communicable Diseases, Maternity, Infancy, and 
Child Hygiene, Public Health Education, Tuberculosis, 
Venereal Diseases, and Public Health Nursing. The popular 
results of these divisions are published in a weekly bulletin 
called the Health News, which you should have in your school 
library and should read. 
433. The Hygiene of Country Schools.1 There are about 
186,000 one-teacher rural schools in this country, and the 
children attending them constitute more than 50 per cent 
of all school children in the United States. The sanitary 
and hygienic conditions of these schools, therefore, constitute 
an important public health problem to the community. 
1 This section is taken from Clark's Hygeia. CHILD WELFARE CLINICS 
633 
Health supervision of school children first started in this 
country about thirty years ago, and since that time con- 
siderable advance has been made. Unfortunately, however, 
progress has been largely confined to the cities, while in many 
of the rural schools deplorable conditions still exist. The 
buildings are old and in a bad state of repair, the classroom 
illumination is faulty, the ventilation inadequate, and some 
of the schoolhouses have served their present purpose for 
three generations. The children who attend them are largely 
denied the medical and surgical attention by specialists so 
often given to city school children. They do not receive the 
benefits of general sanitary measures such as a good common 
water supply and the safe disposal of human excreta, and 
they are unduly exposed to diseases such as malaria and 
hookworm. 
The evil results of this lack of care are evident in a recent 
compilation made by the United States Public Health Service 
in which it was found that 6,099 school children attending 
semi-rural schools practically without medical supervision, 
lost through illness 37,153 days from a possible 666,449 days 
of school attendance. A large part of this might have been 
prevented by adequate health supervision. Surely it is time 
that the '' little red schoolhouse " should be supplanted by a 
modern up-to-date building equipped with the best appoint- 
ments for health and education. 
434. Child Welfare Clinics. - These are clinics to which 
babies can be brought and examined free. They are usually 
located in the poorer parts of a city among those who are 
ignorant of the best scientific methods of care for babies. 
An attempt is made to introduce proper feeding. The 
mothers are given instruction in the clinics and the nurses 
also go into the homes to show the mothers how to care for 
their babies. It is an attempt to carry preventive medicine 
to the people and thus reduce the death rate among the class 
of people where it is the highest. 634 
HEALTH AND CONSERVATION 
The greatest safeguard against many diseases is a vigorous 
body. To possess a vigorous body certain well-known 
health laws must be complied with. Some of these have to 
do with a supply of pure air, well selected and clean food, 
healthful occupations, rest, and recreation. Some boys and 
girls are in poor health because of diseased tonsils or decay- 
ing teeth, whose poisons are pouring into the system and 
prevent the development of a vigorous body, which is, as we 
have said, the best safeguard against most diseases. 
There is a group of hygienic measures that, when practiced, 
keep us in good health under normal conditions. When the 
normal body is underfed, dirty, without proper clothes, or 
when the tonsils are diseased or the teeth are uncared for, 
the normal resistance to more serious germ diseases is danger- 
ously lowered. All such conditions hinder the regular growth 
of the body. 
To correct as many of these conditions as possible, health 
directors, school nurses, and school physicians make regular 
inspections and inform parents about the health of their 
children. This work is under the general direction of the 
State Board of Health and is doing much to insure a genera- 
tion of healthier boys and girls. 
435. The Anti-tuberculosis Campaign. - It is the general 
theory of medical science that a very large percentage of 
human beings have had a mild form of tuberculosis in youth, 
and during this period have acquired immunity to these 
germs. This conclusion has been reached after discovering 
the remains of an early infection in a large number of human 
bodies whose death has not been due to tuberculosis but to 
some other cause. Another generalization follows from this 
belief, i.e. that a recurrence of tuberculosis may follow with- 
out a new infection when the body becomes exhausted and 
is in poor health. So important is this disease that most 
states have made a special division for it in their health de- 
partments, as already stated for New York State. Then PUBLIC HEALTH ACTIVITIES 
635 
there are independent private charitable organizations, with 
national and international activities, that are devoted to the 
eradication of tuberculosis. The Rockefeller Foundation 
has been assisting in this work in various countries of 
Europe. 
Nearly every county in New York State has either a tuber- 
culosis hospital or has arrangements whereby it can send its 
needy sufferers to such a hospital. In these institutions, 
incipient cases are trained to care for themselves. If the 
care can begin early enough, a cure is usually effected. Such 
persons are taught how to live and are able to tell others 
how they should live. Through this splendid campaign a 
great deal of valuable biological information has been brought 
to hundreds of thousands of people. There is no way of 
estimating how many people have been aided in preventing 
this dreadful malady. 
The same hygienic measures that are good for tubercu- 
losis are beneficial to the general health of every one of us. 
436. National and International Public Health Activities. 
- The responsibility for keeping the water and food in a pure 
condition is often more than one state can manage, and the 
control of some of these activities has been taken over by the 
National Government. In the same way there has grown up 
a conviction that one nation cannot adequately regulate con- 
ditions when a world-wide distribution of a disease exists. 
For example, malaria and yellow fever exist in all parts of 
the tropics. Leprosy is almost wholly an Oriental disease. 
Cholera and typhus fever are confined mostly to the eastern 
hemisphere; while hookworm belts the world in an area 
about 20 degrees each side of the equator. Such conditions 
call for international cooperation, and the Health Division of 
the League of Nations is such an organization. 
Some notable instances of epidemics have followed the 
eating of oysters from localities where sewage from rivers 
has poured into the ocean where oysters and clam beds 636 
HEALTH AND CONSERVATION 
are found. The regulation of the collection of shell-fish 
would thus naturally come under the National Government 
because it often happens that the territory of more than 
one state is involved. 
Our National Government has a splendidly organized 
department of Public Health and Research Laboratories. 
The workers in these have found that special regulations 
have to be adopted when a large number of men are in tem- 
porary camps as the army moves from place to place. The 
work of the army in public health education has been an 
important factor in increasing our general information. 
437. National Quarantine. - Strict quarantine regula- 
tions are enforced by the National Government upon boats 
coming from ports where certain diseases are prevalent. 
Regular inspection of all immigrants is made before they 
are permitted to land. 
Some conception of the extent and exactness of such quar- 
antines as applied to animals and plants can be gained from 
a knowledge of insect pests and the regulations governing 
them, and the importation of plants. 
Insect Pests. - Most of us never realized how many 
different kinds of insects there were that feed upon even 
garden vegetables until we tried to do our part by caring for a 
war garden. Nearly all the thousands of plant diseases and 
pests that go to make the life of the farmer, gardener, or 
orchardist unhappy, and greatly to reduce the size or entirely 
destroy his whole crop, a few years ago occupied but small 
territories. So far as our information goes more than one 
half of the insects that cause incalculable losses to our fruits 
and vegetables came from foreign countries. They may 
be said to have migrated to the land of plenty, for in their 
native homes either the amount of food was limited by the 
growing of small crops or their natural enemies were so nu- 
merous that they were themselves destroyed before they could 
do any marked damage. NATIONAL QUARANTINE 
637 
One of the early pests to be introduced into America was 
the Hessian fly, which was brought over in the straw used to 
bed the horses of the Hessian soldiers in the Revolutionary 
war. The litter from the stables was thrown ashore in New 
Jersey, from which region it soon spread to all sections. This 
single immigrant insect destroys as much wheat each year 
as, if marketed, would pay the entire expense of the Revolu- 
tionary war. 
At first thought it seems strange that the government of 
the United States should have a quarantine against insects 
landing at our seaports, but that is just what the Federal 
Plant Quarantine Act of 1912 means. One department of 
our government is turning its attention to little insects in 
order to save American agriculture by preventing any more 
kinds of insects from entering the United States. 
Fruit-flies. - Some of these insects of other lands that 
are serious pests are popularly known as fruit-flies. They 
resemble house-flies, but are of more attractive appearance, 
inasmuch as their wings are prettily spotted and banded 
and their bodies are usually more brightly colored. They 
are like house-flies also in that they lay small eggs that hatch 
into whitish maggots. These maggots feed upon the living 
tissues of fruits, nuts, and vegetables. Eggs are laid just 
under the skin of the fruit, and these eggs hatch into maggots 
that burrow in all directions. As the maggots tunnel about 
they cause decay to develop, and these decaying areas pro- 
duce greater injury than the maggots themselves. In order 
to destroy fruit-flies, the Plant Quarantine Act prohibits 
the entry of all horticultural products likely to carry insect 
pests unless they have been rendered free from danger as pest 
carriers. 
The Bermudas probably would not now be infested by the 
Mediterranean fruit-fly had not a sailing vessel, bound for 
New York from the Mediterranean region during Civil War 
times, been blown from her course and forced to unload her 638 
HEALTH AND CONSERVATION 
cargo containing infested fruits at St. George. The Medi- 
terranean fruit-fly did not become established in Australia 
until steamships and cold storage made it possible for the 
infested Mediterranean countries to ship oranges to Perth 
and Sydney. With the pest established in eastern Aus- 
tralia the ships plying between Australia and Hawaii carried 
the maggots to Honolulu, and to-day the inspectors of the 
state of California and of the United States are intercepting 
infested fruits on ships arriving at San Francisco and San 
Pedro from Honolulu and Hilo. 
Some conception of the extent to which restrictions are 
placed is gained from the following list: Importations of 
certain fruits from Mexico are prohibited; also all pines 
from Europe, and five-leafed pines from Asia, Canada, and 
Newfoundland; alligator pear seeds from Mexico and Cen- 
tral America; all citrus fruit stock from all foreign coun- 
tries ; Indian corn or maize and closely related plants from 
India, Siam, China, Malayan Archipelago, Australia, New 
Zealand, South Sea Islands, Philippines, Formosa, and 
Japan ; sweet potatoes and yams from all foreign countries; 
banana plants from all foreign countries, including Hawaii 
and Porto Rico. 
438. Work of Special Health Agencies. - The Rocke- 
feller Institute for Medical Research is distinct from the 
Rockefeller Foundation. Its purpose is indicated in the 
charter as being devoted to " medical research with special 
reference to the prevention and treatment of disease." 
Several notable discoveries in regard to antitoxins and the 
conditions regulating the growth of cells under normal and 
abnormal conditions have already been made. 
The Rockefeller Foundation was chartered in 1913 to 
promote the well-being of mankind throughout the world. 
The large resources of this private foundation are almost 
entirely spent on public health and medical education. 
The trustees of the foundation have contributed several WORK OF SPECIAL HEALTH AGENCIES 
639 
millions of dollars to the establishment of schools of hygiene 
and public health at the Johns Hopkins and Harvard uni- 
versities, as well as supported medical education by large 
additional gifts to selected medical schools in the United 
States, Canada, England, and China. 
During the year 1922 demonstrations on hookworm con- 
trol were carried on in eleven southern states and twenty-two 
foreign countries, which gave this foundation an interna- 
tional activity. In a similar way their work on malaria and 
yellow fever took on an international character, for the con- 
trol of such diseases is not a local problem. Prevention 
requires that the causes be eliminated, and this no state or 
nation can do without the cooperation of all of the countries 
where the cause exists. 
The discoveries of scientists constitute an absolutely 
essential step, but unless these discoveries can be made effec- 
tive by being put into practice, they are of no avail. For 
instance, scientists learned that certain fish were very bene- 
ficial because they fed on mosquito larvae, but it was neces- 
sary to distribute these fish in the regions where malaria 
and yellow fever were prevalent before any benefit could 
result. The Rockefeller Foundation helped to introduce 
these fish (Figure 262) into Mexico during 1922. 
The League of Nations has a special division, the Health 
Section, which has been doing remarkable work in the dev- 
astated and famine-stricken regions of Europe. The Rocke- 
feller Foundation has been cooperating with this organization 
by helping to finance its work, which is of inestimable value 
in the preservation of the public health of Europe and Asia. 
The name of the Memorial Institute for Infectious Dis- 
eases, founded in memory of John Rockefeller McCormick 
in 1918, was changed to the John McCormick Memorial 
Institute for Infectious Diseases in 1918. This institution, 
located in the city of Chicago, consists of a laboratory and 
hospital. Diphtheria, diphtheria carriers, measles, scarlet 640 
HEALTH AND CONSERVATION 
fever, and certain of the respiratory infectious diseases have 
received critical attention in this research institution. The 
discovery of the germs of scarlet fever was announced in 
1924 by this institution. 
The Carnegie Institute of Washington was founded by 
Andrew Carnegie on January 28, 1902. The articles of 
incorporation declare that the object shall be "to encourage 
in the broadest and most liberal manner investigation, re- 
search and discovery and the application of knowledge to 
the improvement of mankind." We are particularly in- 
terested in the biological departments of research. (1) The 
Department of Genetics and Experimental Evolution located 
in Cold Spring Harbor, Long Island, N.Y., is chiefly devoted 
to the theoretical studies of heredity and evolution, and the 
application of heredity to human beings. (2) In the Labora- 
tory for Plant Physiology at Tucson, Ariz., research activities 
are carried on in desert vegetation with especial attention 
given to their adjustments to the arid conditions. (3) The 
Department of Embryology, located at the Johns Hopkins 
School, Baltimore, is concerned chiefly with human embryol- 
ogy. (4) The Nutrition Laboratory, Boston, Mass., devotes 
most of its researches to discovering the fundamental laws 
governing our vital activities. It has been necessary to in- 
vent many complicated pieces of apparatus in order that 
exact measurements can be made on human beings under- 
going fasting, or exercise experiments. So far the results 
abundantly justify the large amount of money that has been 
expended. It will take many years to solve these problems 
accurately. (5) The Department of Marine Biology, located 
at Tortugas, Fla., is given over to the study of marine tropi- 
cal life. 
The American Society for the Prevention of Cancer was 
organized in 1913 and is devoting its research activities to 
these abnormal growths, which we do not as yet understand. 
There are similar organizations in London and Paris. MODERN SURGERY 
641 
The Millbank Memorial Foundation of New York City is 
another private organization that is making a critical study 
of tuberculosis and its prevention. It is just beginning its 
activities, so that it cannot be stated what special phases 
will be emphasized. 
Any enumeration of important public health activities 
that did not take into consideration the Red Cross, an inter- 
national and national voluntary society, would be omitting 
a very important organization. The Red Cross holds itself 
in readiness to offer the best scientific assistance that can be 
given in times of great emergencies, such as the San Francisco 
earthquake and fire, the flood in the Ohio Valley, or the re- 
cent Japanese earthquake, as well as in time of war. 
The work of these several Public Health agencies varies 
from year to year, and you will find it interesting to make a 
special study of their work during the year that you study 
biology. 
439. Modern Surgery. - Modern surgery began with 
Sir Joseph Lister, who in 1867 announced his practical appli- 
cation of the germ theory to wounds. He said: " When it 
had been shown by the researches of Pasteur that the septic 
property of the atmosphere depended, not on oxygen or 
any gaseous, constituent, but on minute organisms suspended 
in it, which owed their energy to their vitality, it occurred 
to me that decomposition in the injured parts might be 
avoided without excluding the air, by applying as a dressing 
some material capable of destroying the life of the floating 
particles." 
This method of Lister, greatly modified and improved, 
has been universally adopted. Until Pasteur or some one 
else discovered germs and the fact that they gave rise to 
fermentation changes, the marvelous results of Lister were 
impossible. Pasteur did not ask whether the study of fer- 
mentation had any relation to man or not, when he was 
carrying on his epoch-making discoveries. He was simply 642 
HEALTH AND CONSERVATION 
trying to discover what principles governed fermentation. 
We never know just how valuable a scientific discovery will 
turn out to be any more than we can predict just what great 
contribution to human welfare some of you may make. 
Modern surgery takes great care to prevent germs from 
getting into the openings which have been made to correct 
some abnormal condition. The knives and other instru- 
ments are sterilized. The air in the operating room is dust 
free. The surgeon and nurses wear masks so that germs 
from their noses or throats may not escape into the air. 
This is aseptic surgery. In antiseptic surgery less care is used 
in the operating room, but all cuts are treated with germi- 
cides to kill the germs that may have entered. A strong 
human body may manufacture its own antitoxin and thus 
neutralize the poisons of such germs as are not killed, and the 
patient make a good recovery. The advantages of aseptic 
surgery over antiseptic surgery are self-evident. 
440. Insulin. - Whenever a discovery is made that helps 
to relieve suffering and prolong life, popular interest is im- 
mediately stimulated. It has been known for many years 
that the disease called diabetes was immediately due to 
the failure of the body to burn properly all of the sugars that 
were eaten as food. Scientists had been working for more 
than fifteen years to isolate from the pancreas the particular 
substance that helps the body to utilize the food sugar. They 
centered their interest on the pancreas because certain cells of 
the pancreas were failing to act normally. Finally Dr. Banting 
of the University of Toronto succeeded in 1922 in isolating 
from the pancreas the specific substance that stimulates the 
body in such a way that sugar is utilized. This substance 
is known as insulin. A word of warning is necessary in re- 
gard to the use of insulin because it is not a cure for diabetes 
but merely relieves the symptoms. A large number of sci- 
entists are working on the several problems that this discov- 
ery has helped to solve, and we may expect to learn a great CONSERVATION OF BIOLOGICAL RESOURCES 
643 
deal more about the use of insulin and possibly the preven- 
tion of diabetes within the next few years. 
441. Conservation of Biological Resources. - The whole- 
sale destruction of game represents a distinct loss to all lovers 
of out of doors and often creates a serious situation, for the 
destruction of selected groups of animals usually upsets the 
balance in nature. This may allow the enormous multipli- 
cation of harmful animals or result in the elimination of bene- 
ficial ones. Already the reduction in the number of bij'ds 
has permitted the development of harmful insects in our 
orchards, and to eliminate them requires a large outlay of 
time and money in order that we may raise good fruit. 
Through the Reclamation Service water has been con- 
ducted into desert regions and now great crops of food are 
annually harvested where previously sagebrush and cactus 
were the chief plants that could live. 
Under the direction of the National and State govern- 
ments, large sums are spent annually to help us use our 
biological resources more intelligently. 
Game Laws. - The United States Department of Agri- 
culture issues annually a pamphlet containing a summary 
of the laws of the United States, Canada, and Newfound- 
land, relating to trapping, open seasons, propagations, and 
bounties. By the adoption of strict regulations there is 
gradually coming into existence a realization of the impor- 
tance of conserving our wild animals. By offering suitable 
bounties the destruction of such harmful animals as wolves 
and coyotes and the destructive rodents is being effected. 
442. New York State Conservation Department. - This 
is a separate department and is concerned with the care and 
protection of the forests, and the fish and game in these 
forests and inland waters. It also has supervision of forest 
nurseries, reforestation, hatcheries, game farms, and the 
conditions under which vacationists may camp on state land. 
Supplementing the work of this department, the State 644 
HEALTH AND CONSERVATION 
Agricultural College, the State Forestry College, and the 
State Experimental Station carry on researches and train 
men to understand the necessity of conserving our plants 
and animals. 
Specifically the work of the New York State Agricultural 
Station takes up such problems as the following. From the 
early days of the Station's existence, down to the present 
time, an effort has been made to test every variety of hardy 
fruit that will grow and to see in what way it can be improved. 
Much attention has been given to the breeding of new fruit. 
More than thirty thousand seedlings of various sorts have 
been grown, and from these over sixty new varieties of differ- 
ent fruits have been secured which were deemed worthy of 
naming and distributing to fruit growers. 
The work of this station in studying plant and animal 
diseases has been very great. In fact, it is probably not too 
much to say that only because of the tireless efforts of en- 
tomologists and plant-disease specialists is marketable fruit 
possible. 
Extensive and original experiments have been carried 
on in connection with the milk supply. A quick and easy 
method has been devised for the direct counting with the 
microscope of the bacteria in fresh milk as it is brought from 
the farm. The application of this method is of great benefit 
in quickly determining whether milk is fit to use or not. 
Such experiments as these indicate that if the station is to 
serve the state and nation effectively, it must lead the way 
into new fields of endeavor and not be content simply to 
follow the trend of the times. 
443. The United States Fish Commission. - The Bureau 
of Fisheries is one of the subdivisions of the United States 
Department of Agriculture. In this Department are carried 
on studies dealing with problems of national importance 
concerning the sources of food from the sea and the great 
inland lakes such as Michigan, Superior, and others. Early THE UNITED STATES BIOLOGICAL SURVEY 
645 
studies upon the life of lobsters and fishes revealed the fact 
that a great many of the young were eaten before they had 
an opportunity to mature. This suggested the desirability 
of establishing hatcheries where young could be hatched and 
protected until they were old enough to secure their own food 
and escape their enemies. The United States Government 
supports a number of such hatcheries. This is also true of 
New York State, where hundreds of thousands of trout and 
bass eggs are hatched annually. 
Just now lobster fishing is of major interest. The United 
States Bureau of Fisheries has endeavored to transplant 
lobsters to the Pacific coast with little success. However, 
there seems to be no reason why it should not eventually 
succeed. The success of this enterprise would greatly in- 
crease the annual output. Lobster fishing on the Atlantic 
coast is declining. Great improvements in the management 
must be instituted if this business is to continue to be profit- 
able. 
444. The United States Biological Survey. - This is 
another division of the United States Department of Agri- 
culture. It is the bureau of information on all matters per- 
taining to game and wild-life protection, economic value 
of birds, routes and migration habits of birds, and, in general, 
the informational side of such biological questions. As an 
example of the use made of its fund of knowledge, we can 
cite its recommendation of a law prohibiting the importation 
of the mongoose. 
This animal which is said to combine the ferocity of the 
mink, the agility of a squirrel, the penetration of a ferret, and 
the cunning of a rat, has caused no end of trouble in Jamaica, 
Cuba, and some of the Hawaiian Islands, where it was intro- 
duced for the purpose of destroying rats. It not only de- 
stroyed rats, but when these were gone it started in to ex- 
terminate all of the wild birds and domestic fowls of the 
island. If such an animal were introduced into the United 646 
HEALTH AND CONSERVATION 
States, you can easily imagine what damage it would do to 
our game birds, song birds, and domestic fowls. 
This Department has issued a considerable number of 
pamphlets describing the life history, food habits, breeding 
habits, and general activities of our wild animals. These 
bulletins can be secured by writing to the Department of 
Agriculture. The activities of this Department in helping 
the western farmers to destroy the numerous rodents that 
feed upon their grains, has been of immense importance. 
One would expect to find all mammals under the super- 
vision of the biological bureau. But this is not so. The 
fur seals which have become so valuable financially, are under 
the direction of the Bureau of Fisheries, as these animals 
live in the ocean, and the ocean life is all under the direction 
of the Bureau of Fisheries. 
One would also expect that the care of our national parks 
would be under the supervision of the Department of Agri- 
culture, but this is not so, and we look to the Department of 
the Interior for the supervision and regulation of these parks. 
All of these agencies in whatever bureau in the state or na- 
tion they happen to be placed are established for the conser- 
vation of biological resources. 
445. Conservation and the Future. - The death rate 
among human beings is being lowered by applying the re- 
sults of scientific discoveries about health and disease. Wild 
animals are being preserved in the " sanctuaries " and regu- 
lations protecting our wild flowers are becoming more general. 
Destructive insects and harmful plants are being kept out 
of the United States. The National Government is co- 
operating with the state departments in their endeavor to 
control the cotton boll weevil and the European corn borer. 
International cooperation is bringing under restraint world- 
wide diseases that destroy man, animals, and plants. 
Advance in science must wait for the work of individuals 
who have those qualities of mind that enable them to solve CONSERVATION AND THE FUTURE 
647 
problems that no one else has yet been able to solve. We 
are too prone to pass lightly by great minds, although daily 
we enjoy the results of their labors. Let us pause a moment 
and tender to them our sincere obligations. 
Dr. Charles Wardell Stiles of the United States Public 
Health Service discovered hookworm and the methods of 
cure. This contribution alone made many millions of people 
debtors to him. His marvelous discovery did not make him 
any richer in money but it did give to him the greatest satis- 
faction that ever comes to any human being. The men who 
lost their lives trying to discover the cause of yellow fever 
and the value of X-rays in the treatment of disease, are 
among our greatest national heroes. They died trying to 
find out a method by which the lives of millions of people 
might be prolonged. A nation is safe when it has such heroes. 
It is in danger when it forgets them. 
Health activities 
Municipal 
Water supply 
Sewage 
Disposal 
Purification 
Septic tanks 
Milk supervision 
Other foods 
Quarantine 
State 
Supervision of children 
Country schools 
Child welfare clinics 
Anti-tuberculosis campaign 
National and international activ- 
ities 
National quarantine 
Insect pests 
Fruit-flies 
OUTLINE 
Special agencies 
Rockefeller Institute 
Rockefeller Foundation 
League of Nations 
McCormick Memorial Insti- 
tute 
Carnegie Institute 
Minor organizations 
Modern surgery 
Insulin 
Conservation of biological re- 
sources 
Game laws 
N. Y. State Department 
U. S. Fish Commission 
U. S. Biologic Survey 
Conservation and the future 648 
HEALTH AND CONSERVATION 
SUMMARY 
Conservation of animals, plants, and human beings is the greatest 
problem that we have to solve. Immense progress has been made 
through scientific discovery. Municipal, state, national, and interna- 
tional agencies are making effective these discoveries. Many private 
agencies are making great contributions to conservation through their 
researches and by distributing the new information all over the world. 
QUESTIONS 
What is conservation? Why did not conservation begin a hundred 
years ago? What must be done before conservation activities can be 
effective with the cotton boll weevil? What is public health? How 
is it carried on? Why are laws necessary in connection with public 
health activity? What conclusions do you draw when you discover 
that a country has practically no health laws? Name some of the 
agencies that are helping the advancement of public health. Why 
should there be conservation of biological resources? What agencies 
are doing the most in this regard? CHAPTER XXXVII 
BIOLOGY AND HUMAN PROGRESS 
From lower to the higher next, 
Not to the top, is Nature's text; 
And embryo good, to reach full stature, 
Absorbs the evil in its nature^ 
- Lowell 
Whenever we compare the things that we can do, the pleas- 
ures that we enjoy, the clothes that we wear, our knowledge 
of disease, with those of our fathers we discover that impor- 
tant progress has been made. This progress shows the extent 
to which man has gained control of his environment and the 
use that he has made of this control. In a general way our 
environment has not undergone much change in the last 
thousand years, and yet our control over it has undergone 
more change during the past hundred years than in any 
previous thousand years. 
This change is due largely to two factors: first, scientific 
discoveries; second, the intelligent application of these 
discoveries to everyday life. 
446. New Discoveries. - If our universe has remained 
about the same during the past thousand years, how can there 
have been so many new discoveries in recent years? This 
question can be easily answered. When some one finds a 
new animal or plant and announces that he has discovered 
this animal or plant, it simply means that man has seen and 
described it for the first time. This kind of animal or plant 
may have been living in this same region for hundreds of 
649 650 
BIOLOGY AND HUMAN PROGRESS 
years. It is the same when some one makes a new discovery 
in physics or chemistry. He recognizes relationships that 
no one else has ever noticed. 
All new discoveries have been made by men and women 
who once were just boys and girls as you are, with possibly 
no notion of the way that they were to help to make this 
world a better place to live in. Every one of us is anxious to 
do some little thing to improve the conditions under which 
Photograph furnished by Cornell University. 
Figure 410.-Timothy Heads. 
people live. There is still much to be learned about the re- 
lations of plants and animals to man and some of you should 
prepare yourselves to have a part in this great work. So 
much has been learned that it will be necessary for you to 
spend a number of years before you will have sufficient train- 
ing to undertake to solve any of nature's secrets. 
In this chapter a brief account of the value and character 
of new discoveries in connection with improving plants and IMPROVEMENT OF PLANTS AND ANIMALS 
651 
animals, the relation of heredity and variation to progress, 
will be given. 
447. Improvement of Plants and Animals by Breeding. - 
In Figure 410 is shown a photograph of the different sizes 
in the heads of timothy hay. The variations have to do 
with the length, thickness, and form of the head. In these 
heads are grown the seeds which are valuable as food to 
animals and which are used as seed when the farmer wishes 
to raise a crop of hay. Figure 411 shows the practical value 
of planting seed that yields a large crop instead of a small 
Photograph f urnished by Cornell University. 
Figure 411. - Bundles of Timothy Raised under Identical Condi- 
tions from the Same Amount of Seed. 
It pays to plant good seed. 
one. In each of the five bundles in this figure, the same 
amount of seed was planted in the same kind of soil. It is 
unprofitable to use poor seed. 
In order to furnish the farmer with the necessary informa- 
tion upon all such subjects, scientific experts have been and 
are now devoting a great deal of time to experimentation. 
The following example shows the importance of such study 
in helping man to produce new and better kinds of plants 
and animals. 
Figure 412 consists of bearded wheat, the pollen of which 
was placed on the stigma of the wheat flowers that formed on 
the non-bearded wheat shown at the right in the figure. 652 
BIOLOGY AND HUMAN PROGRESS 
When the kernels of wheat in this head ripened, they were 
sown and a plant was produced which grew a longer head, 
having practically no beards (the middle head in Figure 412). 
Such a head of wheat would yield more kernels than either 
Photograph furnished by Cornell University. 
Figure 412. - Heredity in Wheat. 
The head of wheat on the left of this figure has beards. The pollen from 
the wheat flowers of this head was placed on the stigma of the wheat 
flowers that grew in the head shown in the right wheat head of this figure. 
When these kernels of wheat ripened, they were sown and produced a 
wheat plant that had more wheat kernels than either parent. This is the 
head shown in the middle. Charles Darwin (1809-1882) made many original observations 
on animals and plants and conducted numerous experiments with 
them. But he was not satisfied simply to discover new facts; he 
wished to find some explanation for them. Just how all of the 
many forms of life came to live where they do and to have the size 
and habits that they do is hard to determine. Darwin believed 
that there was a natural struggle continually going on in nature 
between the weak and the strong, and that some which could run 
faster or eat more kinds of food were able to live in the competi- 
tion while the ones that lacked such ability died. He formulated a 
number of explanations (theories or hypotheses). The best known 
of these theories is the Origin of Species by Natural Selection. 
The main idea emphasized by Darwin in this theory is that life 
has gradually unfolded or evolved (hence evolution) passing from 
the simpler types like sponges or hydra to the more complex, 
gradually becoming more complicated as the division of labor 
sets organs more and more apart. 
Darwin, himself, was conservative and reverent, as the following 
from the closing sentences of his book on the Origin of Species 
shows : 
"There is a grandeur in this view of life, with its several 
powers, having been originally breathed by the Creator into a few 
forms or into one; and that, whilst this planet has gone cycling 
on according to the fixed law of gravity from so simple a begin- 
ning, endless forms most beautiful and most wonderful have been 
and are being evolved." IMPROVEMENT OF PLANTS AND ANIMALS 
653 
of the parent heads. Now if the scientific expert can make 
this new wheat plant permanent, that is, produce seed that 
will always grow large heads, he has furnished the farmer 
with a new kind of wheat and has made a new discovery. 
Another example of the way in which scientific experts 
study the question of improving plants and animals is shown 
in the study of the resis- 
tance of grapes to disease. 
The American grape is a 
North American plant 
including from fifteen to 
twenty-five different spe- 
cies, about one half of 
the total number known 
to man. These different 
kinds of grapes grow in 
varied areas and cli- 
mates. Their original 
distribution over North 
America was due to ani- 
mals, such as birds, and 
to river currents. 
The several varieties 
of American grapes are 
descended from an origi- 
nal species which has 
become changed by en- 
vironment until we find 
types of grapes as diverse as the regions in which they are 
found. 
Many of these varieties have been in existence since white 
men came to this country. During this time they have ac- 
quired a strong resistance to certain parasitic diseases which 
are very destructive to the European grapes. Among them 
is one that is caused by a minute plant louse that lives either 
Figure 413. - Leaf Galls on Grape 
Caused by Grape Phylloxera. 
The roots are also injured by this dis- 
ease, which threatened to destroy all of 
the European vineyards. 654 
BIOLOGY AND HUMAN PROGRESS 
in the leaf, stem, or root. This insect is known as phylloxera 
(fil-oks-e-ra). In addition to this animal disease, there are 
three plant parasite diseases : black-rot, downy mildew, and 
powdery mildew. Each of these four diseases is able to kill 
grape plants, and more than one may attack the same plant 
at the same time. 
A few years ago these diseases became so widespread in 
Europe that they threatened to destroy most of the Euro- 
pean vineyards. Many experiments were undertaken to 
save this valuable industry. It was discovered that the 
European grapevine could be grafted on to the root of any 
one of several of the American grapes, and when these vines 
were thus grafted they were found to possess a resistance 
to all four diseases, with the result that the vineyards of 
Europe were saved. 
This success was due to scientific study, which discovered 
the difference between the European and American grapes 
in their power to resist disease, and the fact that the quality 
of the European grape would not be altered by grafting it 
on the roots of the American varieties. Here we have an 
illustration of variation that is not confined to the shape and 
size of the parts but to their resistance to disease. This 
may be described as an acquired immunity that is transmitted 
by heredity from one generation of grapes to another. The 
word immunity used in this last sentence was explained on 
page 418. 
These examples introduce us to a large number of results 
that scientists have secured, which are of great benefit to 
man. The sugar content of corn has been increased, seedless 
oranges and grapefruit have been developed by breeding 
experiments. The Holstein breed of cows is famous for a 
large yield of milk, while the Jersey gives milk that is very 
rich in butter fat. The heavy draft horse that you see haul- 
ing great loads is poorly qualified for racing, and yet the 
draft horse and race horse are both the product of experi- HEREDITY 
655 
mental breeding. One of the most striking illustrations of 
the extent to which such breeding can be carried is seen in 
any large exhibit of poultry. At the New York State Fair 
more than one hundred different classes of poultry are shown 
each year. 
What does the scientific man do who makes such discov- 
eries? He starts out to tell just as many people as he can 
that he has made a new discovery and to ask them if they 
do not wish to try it. In order that as many people as possi- 
ble shall have an opportunity to know about his new dis- 
coveries he writes a description of them and sends them to 
some scientific journal. He does not get any pay for his 
scientific articles, as do writers of stories, nor does he have his 
articles copyrighted, but he invites any one who wishes, to 
use his facts. 
Thus new ideas are constantly being furnished through 
the investigations of the hundreds of scientists throughout 
the world. These new ideas keep one informed about the 
way other people do and help to make one broad-minded 
and progressive. New ideas and new discoveries, however, 
are of no value unless they are utilized. 
448. Heredity. - An easy way to understand the tech- 
nical meaning of this term, which we use so frequently, is to 
make a study of your hand. Normally we all have four 
fingers and one thumb, but our hands are quite unlike. This 
is readily seen by comparing the three hands in Figure 414. 
The large one is the hand of father, the middle one of daugh- 
ter, and the right one of mother. The first and the last fingers 
of the father's hand are about the same length, while the 
little finger of the mother is much shorter than her first finger. 
The difference in the length of these two fingers is repeated 
in the hand of the daughter. We say that the daughter in- 
herited from her mother a short little finger and a long fore- 
finger. 
Now if we study the position of the thumb in its relation 656 
BIOLOGY AND HUMAN PROGRESS 
Figure 414. - Heredity Shown by Comparison. 
Photograph of hand of father at the left, of mother on the right, and of daughter in the middle. Which parts 
of the daughter's hand are like her mother's ? Which like her father's ? HEREDITY 
657 
to the palm of the hand, it is seen that the distance between 
the thumb and the base of the forefinger is proportionately 
greater in the hand of father than of mother. The same is 
true of the hand of daughter. When she grows to maturity, 
this distance will be much greater than it is in the hand of her 
mother. The daughter inherits this peculiarity in her hand 
from her father. 
Make a study of the several parts of your own hand and 
compare your hand with the hand of your mother and father. 
This study will show you what is meant by the term heredity 
as applied to your hand. 
In a similar manner you can compare the color of your 
eyes and hair; length of arm; shape of head; muscular 
vigor; size of body; intellectual traits, such as interest in 
language, history, science, or business; and temperament, 
which includes liveliness, deliberateness, excitability, quick- 
ness, or slowness. 
After you have made these comparisons, you realize that 
you are unlike both parents in that you have some features 
which are lacking in either your father or your mother. The 
total of the like parts and traits which are the same as in your 
father make up what you have inherited from your father; 
and the total of the parts and traits which are the same as 
those in your mother, make up what you have inherited 
from your mother. Thus we inherit from both parents. 
But there are usually found some structures and char- 
acteristics that do not represent anything found in either 
parent. If such are carefully analyzed, it is usually dis- 
covered that they exist in some of the grandparents. It is 
always interesting to try to locate their origin. 
This study of our hands and other parts of our body leads 
to an important general statement. All the parts of your body 
with their individual peculiarities have existed in other human 
beings and these persons were your immediate ancestors (parents, 
grandparents, great-grandparents, etc.). 658 
BIOLOGY AND HUMAN PROGRESS 
This explanation of heredity applies to all animals and 
plants, so that we can study heredity in our own gardens or 
with our pet animals. 
There is a limit to the differences that exist between child 
and parent, and these differences under normal conditions 
produce changes that would never make the structure a new 
one; for example, the finger is always a finger, and hair is 
always hair. Hered- 
ity is thus a descrip- 
tive, technical word 
used to explain the 
like parts between 
child and parent. 
449. The Mende- 
lian Laws.-The Aus- 
trian Monk, Johann 
Gregor Mendel, used 
the leisure time that 
he had from his duties 
to experiment with 
plants in the garden of 
the monastery. His 
results were published 
in an obscure journal 
in 1866 and he died 
in 1884, before scien- 
tific men had become 
acquainted with his remarkable investigations, for it was 
not until 1900 that similar experiments were made in Holland, 
Austria and Germany, England, France, and America. 
Through a method of investigation, devised by Mendel, 
heredity is rapidly becoming a more exact science. Mendel's 
experiments were concerned with crossing varieties of peas 
which differed in size, color, or form. These experiments 
extended over about eight years and include a large mass 
Figure 415. - Gregor Mendel. 
From a photograph taken about the year 1862. THE MENDELIAN LAWS 
659 
of information. We can only illustrate some of the simpler 
conclusions. 
Two of the pea plants selected for experimentation differed 
in the color of the pea. In one they were green and in the 
other all were yellow. Now when the pollen from the plant 
of the green peas is placed upon the stigma of the plant with 
yellow peas, or just the opposite experiment is tried, and these 
ripened peas are planted, all of the peas will be yellow as in 
Figure 416. This plant is called the first hybrid generation. 
It is called a hybrid be- 
cause of this crossing be- 
tween the two kinds of 
plants. 
Now if the pea flower 
of this first hybrid gen- 
eration is self-pollinated 
and then the ripened peas 
are planted, there will be 
found in the pea pods 
green and yellow colored 
peas, in this second hybrid 
generation (Figure 416). 
The green color appeared 
to be absent in the first 
hybrid generation. It was really concealed by the fact that 
yellow dominated the green. This is the first and most im- 
portant law of Mendel and two descriptive words are used to 
make it clear. The yellow color is said to be dominant and 
the suppressed color, green, is recessive (hidden). 
This same idea was illustrated in comparing the hands 
in Figure 414. The length of the little finger was not inter- 
mediate between that of the two parents. The shortness 
of the little finger was dominant in that particular cross over 
the long little finger of the father. In Mendel's actual ex- 
periments he obtained 6,022 yellow peas, and 2,001 green 
green 
yellow 
First hybrid 
generation 
second hybrid 
generation 
Figure 416. - Diagram to Illustrate 
Simple Mendelian Inheritance. 660 
BIOLOGY AND HUMAN PROGRESS 
colored peas, thus giving a nearly exact ratio of 3:1. Now 
if the green colored pea shown in the pod in Figure 416 is 
planted, it will give rise only to green colored peas. If the 
three yellow peas are planted, however, some of these will 
give rise to yellow and some to green, and the ratio will con- 
tinue approximately of three yellow to one green. In man, 
eye color has been found to be inherited according to this 
law of Mendel. 
Mendel's method of investigation has now been applied 
to a very large number of animals and plants. Large books 
have been written, describing these results. From all of 
these studies it appears that the many peculiarities exist as 
separate parts, such as, the long or short little finger, the 
green or yellow color in the pea. Scientists call these differ- 
ences, characters, and so in stating Mendel's law they say, 
" Characters are represented in the germ cells by units which 
tend to segregate or combine in definite proportions," such 
as was shown in the three to one ratio in crossing peas. 
450. Eugenics. - There are two ways of bringing about 
human progress. The first is by improving the environment, 
the second consists in seeking a better inheritance with which 
to begin life. This is called eugenics and is defined by Galton, 
the famous English student of heredity, as the science of being 
well born. In 1916 there were nearly 395,000 inmates in 576 
institutions in the United States, costing the people in taxes 
over $81,000,000, for that year. The inmates of these 
576 institutions were insane, criminals, dependents, feeble- 
minded, deaf, or inebriates, all showing inferior mental 
qualities. 
Two notable defective family histories have been investi- 
gated, namely, the Jukes and Kallikaks. The Jukes family 
shows a history of 709 descendants of Max Jukes who was a 
shiftless backwoodsman. One half of the children died in 
infancy, and of those who lived, there were 310 paupers, and 
over 30 convicted criminals. The cost to the state in main- EUGENICS 
661 
taining and prosecuting this band of crooks has been over 
$3,000,000. 
The Kallikak family show in a striking fashion that mental 
deficiency when once started may persist for many genera- 
tions; 481 descendants were traced from a feeble-minded 
mother, giving 143 feeble-minded children and 291 who were 
inferior in intellectual ability. In this same family there are 
496 descendants from an intelligent mother and only two 
show any indication of subnormal mentality, while the other 
494 were successful citizens in their several communities. 
In these two tragic illustrations mental deficiency made 
a poor parent and there was a long line of poverty, misery, 
sin, and crime. It is important that we should realize that 
culture, refinement, intelligence, and all of the desirable 
traits present in man are likewise inherited. In all of the 
great countries of the world, we find a long list of eminent 
men who are related by direct descent. In the Bach family 
there are 20 eminent physicians and over 40 less eminent. 
The Darwins became noted for their scientific ability two 
generations before the birth of Charles Darwin. Erasmus 
Darwin was an eminent man. He had a son Robert who 
was a distinguished physician. Robert was the father of 
Charles R. Darwin, who is regarded as one of the greatest 
men of science. The four sons of Charles Darwin all became 
prominent. One of the descendants, Francis Galton, a 
cousin of Charles Darwin, is one of the most famous students 
of heredity. 
In America we have the famous family of Edwards. Jona- 
than Edwards was a noted New England clergyman. In 
1900, 1,394 descendants were known. Among these there 
were 295 college graduates, 13 college presidents and many 
school principals, 60 physicians, many of whom were emi- 
nent, 100 clergymen, 75 officers in the army and navy, more 
than 100 lawyers, 30 judges, and 80 who held public office. 
The contrast between the Jukes and the Kallikak families 662 
BIOLOGY AND HUMAN PROGRESS 
on the one hand, and Bach, Darwin, and Edwards on the 
other, clearly indicate that good inheritance is the most 
priceless gift that ever can come from parent to child. 
Thus general ability and a tendency to industry and thrift 
are qualities that can be inherited. The men and women 
who possess such mental traits carry on the business of the 
country and pay taxes, not only to support the government, 
but also to care for the idle, the shiftless, and the criminal. 
If we have inherited these, we should strive to keep them 
unimpaired and to strengthen them, so that we may pass them 
on to our children, in order that the next generation shall 
possess men and women who will be able to advance human 
progress beyond our best effort. 
451. Mental Health. - We have placed a great deal of 
emphasis in this book on the care of the teeth, good digestion, 
a healthy body, and the prevention of disease. All of these 
are very important. But physical health is not all we need; 
biologists are studying the problem of mental health as 
well, in order to devise ways of helping us to understand this 
part of our life. It represents one of the new fields of benef- 
icent research. 
Biology is intimately associated with everything that has 
to do with disease. Our minds may become diseased and 
insanity may follow. During the years 1917-1922 more 
than 68 thousand persons from 21 states were admitted into 
68 state hospitals for the insane. Four per cent of these 
were associated with alcoholism; 47 per cent were due to 
faulty mental adjustment. Thus, one half of this large num- 
ber might be said to have become insane unnecessarily. 
The time has come to recognize that certain phases of 
insanity are preventable. You should try to keep your 
mind as clean and healthy as you do your body. Try to 
enjoy yourself when you work as well as when you play. 
Your companions should be good books and good friends. 
In just the same manner that you get pleasure from your ENVIRONMENT 
663 
friends, let them enjoy you. Natural healthy recreation 
such as scouting is of great value in giving you a correct 
view of yourself and others. It is a splendid thing to have 
a plan about what you are going to become when you grow 
up. A young boy once wrote an essay on " Why I want to 
go to School." It was very short, " I am going to school so 
that I can enjoy my mind." This needs to be enlarged so 
that we can say, I am going to school so that I can learn how 
to live and can help others to live. This simple plan for our 
lives will do much to prevent mental breakdowns and make 
us fit to be citizens of our great democracy. 
452. Environment. - All through this book attention 
has been directed to the environment in which the animal 
or plant, that was being studied, lived. The same fact was 
emphasized in the beginning of this section dealing with 
human biology. When the environment of man is critically 
studied, it is noted that it may have a large influence upon 
him. Even though he may have inherited a strong body 
and a tendency to thrift and industry, he may find himself in 
a social environment that is so strong that he has great diffi- 
culty in earning enough money to keep alive. When the 
full influence of environment was appreciated, men and 
women began to insist that better housing conditions and a 
certain amount of fresh air and light must be provided in 
order that those who lived in the tenements should find it 
easier to keep well and thus be able to work. Even though 
their environment is not of the best, it is possible for them 
to become superior to it. 
In the steady advance which human progress is making, 
the conditions under which men and women live and work 
are constantly growing better. As these conditions improve, 
there will naturally follow a larger opportunity for our in- 
heritance to have its full influence upon us. Two note- 
worthy movements are already having a marked influence 
in this direction; namely, the prevention of the spread of bio- 664 
BIOLOGY AND HUMAN PROGRESS 
logical diseases and the child welfare movement (see page 
633). As we gain a clearer conception of the importance 
to man of variation and heredity, other movements will be 
undertaken to place man in greater control of his environment. 
The fact that biology stimulates us to think about all 
such problems is one of the main reasons for studying it. 
But with all this scientific information at our disposal, much 
remains for the individual to do. He must realize his ob- 
ligations and opportunities in the age in which he lives. A 
mere passive existence has never accomplished anything 
worth while. The desire to serve our country and our fellow- 
men and a personal ambition must be added to our scientific 
information, if we would attain real success. 
453. Biology and Progress. - In tracing the progress of 
the history of biology you will find the names of many emi 
nent men, who possessed marked ability and industry. One 
of the earliest men to make a great contribution to our sub- 
ject was the famous Greek, Aristotle, who collected large 
numbers of animals and dissected them. He lived more 
than 300 years before the time of Christ. Aristotle sends a 
splendid, simple message down to us from long ago. " I 
found no basis prepared, no model to copy-mine is the first 
step and therefore a small one, though worked out with 
thought and hard labor. It must be looked at as a first 
step and judged with indulgence." Many years later Galen, 
who lived for some time in Rome, was one of the most bril- 
liant scientists among all of the ancients. He was a man of 
originality who studied the lower animals very extensively. 
Similarly we might come down through the ages to modern 
times. But it would be necessary to pause on the way if 
we were to speak with justice of all the great men who have 
made lasting contributions to the progress of science. In 
this book there are printed in connection with the subject 
most closely related to their work the names of a few of the 
great biologists who have contributed to human progress. BIOLOGY AND PROGRESS 
665 
There are also included in this book the names of a con- 
siderable number of Americans who have played a large part 
in making the world a better place for us to live in - men 
like Darwin, Pasteur, Koch, Audubon, and Harvey. Distin- 
guished American scientists living to-day probably outnumber 
those of any other nationality in the world. You should learn 
to respect these remarkable men who are doing so much to 
advance human progress. 
OUTLINE 
New discoveries 
Improvements by breeding 
Heredity 
Mendel 
His laws 
Eugenics 
Defective families 
Jukes 
Kallikaks 
Strong families 
Bachs 
Edwards 
Darwins 
Environment 
Biology and progress 
SUMMARY 
Scientific progress, upon which so much of human progress depends, 
is due to scientific discoveries and the intelligent application of these 
discoveries to our lives. Domestic plants and animals have been 
greatly improved by experimental breeding. These improvements are 
based upon sound scientific principles. Heredity is the study of the 
similarity and differences that exist between parent and offspring. 
Owing to the method devised by Mendel, experts in the study of heredity 
can predict with a great deal of accuracy what characters will be in- 
herited and in what proportion. The application of the principles of 
heredity to man are discussed under the term Eugenics. 
QUESTIONS 
What do you understand by Human Progress? How can Biology 
improve the conditions under which you live? Mention some of the 
ways in which it has improved them. How are new discoveries made? 
How can you make new discoveries? What does a scientific man do 
when he makes a new discovery? How does this differ from what a 
man does who makes an invention? How do we study heredity? 
Who was Mendel? What was his method? Why is it important to 
know about Eugenics? How can you help to improve the race? RfiSUMfi OF DEMONSTRATIONS FOR 
LABORATORY EXERCISES 
Description of not less than 30 demonstrations should be 
recorded in the note-book of each student in the year course 
and not less than 15 demonstrations in the half-year course. 
1. Demonstrations to observe the characteristics of some 
of the elements and compounds - oxygen, carbon, hydrogen, 
nitrogen, water, and carbon. Pages 24-27. 
2. Demonstration of the physical appearance of each of 
some other elements and compounds - sulphur, phosphorus, 
iron, magnesium, sodium, potassium, sodium nitrate, calcium 
acid phosphate, and potash. Pages 26, 27. 
The laboratory should have these substances. 
3. Tests for the nutrients. Pages 42, 342, 344, 537. 
4. Demonstration to show photosynthesis (includes neces- 
sity of light and of chlorophyll). Pages 39, 40, 461. 
5. Demonstration to show digestion of food. (Use 
starch.) ' Pages 41, 42. 
6. Demonstration to show osmosis. Pages 42, 43, 492. 
7. Demonstration to show oxidation. Pages 40, 41. 
8. Demonstration to show parts of protozoon studied. 
Pages 246, 247. 
9. Demonstration to show effect of (a) alcohol, (6) tobacco 
on one-celled organisms. Page 252. 
10. Demonstration, using manikin, models or organs of an 
animal, of important parts of the human body. Page 271. 
11. Demonstration to show digestion of protein. Page 342. 
12. Demonstration to show necessity of digestion of 
starch. Page 344. 
667 668 
DEMONSTRATIONS FOR LABORATORY EXERCISES 
13. Experiment to show normal rate of pulse and causes of 
variation. Pages 353, 354. 
14. Demonstration to show growth with bacteria from 
different sources. Pages 392-396. 
15. Microscopic demonstration of lower epidermis of leaf. 
Page 453. 
16. Demonstration to show upward path of liquid through 
stem. Page 481. 
17. Demonstration to show the region of root through 
which liquid rises. Pages 492, 493. 
18. Demonstration to show position and kinds of food 
stored in seeds. Pages 537, 539. See also page 27. 
19. Tests to show kinds and position of nutrients stored 
in seeds. Page 537. 
20. Demonstration to show necessity of stored food in 
seed for germination and growth. Page 539. 
21. Demonstration to prove necessity of air for germina- 
tion. Page 539. 
22. Demonstration to show production of carbon dioxide 
in germination. Pages 539, 540. 
23. Demonstration to show necessity of moisture for 
germination. Page 540. 
24. Demonstration to show necessity of moderate heat 
for germination. Page 540. 
25. Demonstration to show the response of roots to 
(a) gravity, (6) moisture. Pages 493, 541. 
26. Demonstration to show the response of stems to light. 
Page 541. 
27. (Optional) Demonstration to show scales on the wing 
of moth or butterfly. Page 96. 
28. (Optional) Demonstration of adaptations for sting- 
ing, carrying pollen, and cell building. Pages 100-102, 
104-105. 
29. (Optional) Microscopic demonstration to show blood 
corpuscles. Pages 349, 350. DEMONSTRATIONS FOR LABORATORY EXERCISES 
669 
30. (Optional) Demonstration to show the composition of 
bone. Pages 267, 268, 271. 
31. (Optional) Demonstration to show the digestion of 
fat. Pages 338, 339, 342. 
32. (Optional) Demonstration to show capillary circula- 
tion in web of frog's foot or organ of other animal. Pages 353, 
356. 
33. (Optional) Demonstration to illustrate action of 
human lungs and diaphragm in breathing. Pages 285-288. 
34. (Optional) Demonstration to show liberation of gas 
from a water plant. Pages 462, 463. 
35. (Optional) Demonstration to show circulation in 
warmed leaf of elodea. Page 441. 
36. (Optional) Microscopic demonstration to show that 
plants are composed of cells. Page 440. 
37. (Optional) Microscopic demonstration to show cellular 
nature of roots, root hairs, and root cap. Page 487. 
38. (Optional) Demonstration to show the path of air 
to the lungs of a frog. • Pages 143, 144, 152. 
39. Demonstration of liberation of water vapor from 
leaves. Pages 462, 463. 
Note. Demonstrations 27, 28, 29, 30, 31, 32, 33, 36, 
and 38 are optional only in the year course. They are re- 
quired in a half-year course. GLOSSARY 
A 
Abdo'men (Lat. abdomen, belly): the third region of an insect's body; 
the region below the chest in man. 
Absorp'tion (Lat. absorbere, to swallow down): the process of taking 
in liquid food or other substances through the walls of cells. 
Accessory (Lat. accedo, give to) buds : more than the normal num- 
ber (one) in the axil of a leaf. Accessory parts of a flower are the 
sepals and petals. 
Acquired immu'nity : that which results from having had a disease, 
or from preventive measures. 
Adaptation (Lat. adaptere, to fit): changes in, or peculiarities of 
organisms which make them fit for their environment; fitness. 
Ad'enoids (Gk. aden, gland): fleshy growths in the cavity back of the 
nose. 
Adul'terate (Lat. ad, to, + alter, other): to add a cheap or inferior 
substance to a good one; to cheapen, weaken, or reduce. 
Adventi'tious (Lat. ad, to, + venio, come): appearing at unusual 
places, as roots on a slip. 
Af'ferent (Lat. ad, to, + fero, bear) fibers : those which convey 
stimuli to the sense organs, brain, or spinal cord. 
Aggres'sive (Lat. ad, to, + gradior, walk) coloration : that which 
protects an organism as it lies in wait for prey. 
Akene' (Gk. a, not, + chainein, to gape): a dry, indehiscent fruit, as 
in buttercup, dandelion, and clematis. 
Albu'men : a form of protein found in white of egg. 
Al'cohol: a narcotic poison; the intoxicating element in whisky, 
beer, wine, etc. 
AlimenTary (Lat. alimentum, food) canal : the digestive tube or 
tract. 
Al'kaline substance : one which neutralizes an acid. 
Altri'cial (Lat. altrix, nurse) birds : those that are helpless when 
hatched, as robins, sparrows, etc. 
671 672 
GLOSSARY 
Amphib'ians (Gk. amphi, double, + bios, life): animals that spend 
part of their life in water and part on land, as a frog. 
Amphiox'us (Gk. amphi, double, + oxys, sharp): a small, burrowing, 
spindle-shaped marine animal; the ancestor of vertebrates. 
Amylop'sin (Gk. amylon, starch): an enzyme found in the pancreatic 
juice that changes starch to sugar (glucose). 
Anassthet'ic (Gk. an, not, + aisthesis, feeling): substances that de- 
stroy consciousness. 
An'giosperm (Gk. angeion, a case, + sperma, a seed): a plant which 
bears its seeds in a case, as pea, bean, poppy. 
Annel'lida (Gk. anulus, ring): a group of worms composed of rings 
or segments, as earthworm. 
An'nual (Lat. annus, year) ring : the concentric growths of light 
and dark cells formed in a woody stem during a year. 
Anoph'eles : the kind of mosquito that carries the malarial parasite. 
Anten'na (Lat. antenna, a sailyard): a jointed sensory organ on 
the heads of insects, crabs, etc. 
Anter'ior (Lat. ante, before): nearer the head (zobl.); facing out- 
ward from the axis (botany). 
An'ther (Gk. antheros, flowery): the pollen-bearing part of a stamen. 
Antisep'tic (Gk. anti, against, + sepsis, putrefaction): a substance 
which prevents the growth of bacteria or other organisms. 
Antitox'in (Gk. anti, against, + toxin, a poison): a substance in 
the blood after certain diseases which confers immunity from further 
attacks for a greater or lesser period. 
Anus (Lat. anus, ring): the posterior opening of the alimentary 
canal. 
Aor'ta (Gk. aorte, from aeirein, to lift): the largest artery in the 
body; the one leaving the left ventricle. 
Ap'iary (Lat. apis, bee): a place where bees are kept. 
Appen'dage (Lat. ad, to, + pendo, hang): an organ, usually jointed, 
attached to the body. 
A'queous (Lat. aqua, water) humor : the transparent liquid in the 
anterior part of the eye. 
Arach'nida (Gk. arachne, a spider): a class of arthropods which 
includes spiders, scorpions, mites, etc. 
Ar'tery (Lat. arteria, an artery): a blood vessel that carries blood 
away from the heart. 
Arthro'poda (Gk. arthron, joint, + pod (root of pous) foot): a group 
of animals having jointed legs, as insects. 
Articula'tion (Lat. articulo, divide into joints): the joining or place 
of meeting of two bones. GLOSSARY 
673 
Artificial breathing (artificial respiration): that produced by 
mechanical means in an attempt to resuscitate drowned persons or 
those suffocated by gas. 
Asex'ual : without sex; reproduction by other means than egg and 
sperm. 
Ash : the grayish mineral substance resulting from the burning of or- 
ganic matter, as wood. 
Assimila'tion (Lat. assimulare, to make like): the process of chang- 
ing digested food into protoplasm. 
Astig'matism (Gk. a, without, + stigma, spot): a defect in the cur- 
vature of the lens of the eye which causes indistinct vision. 
Au'ricles (Lat. auricula, little ear): the upper chambers of a verte- 
brate heart. 
Ax'illary (Lat. axilla, dim. of axis, axis) buds : those which arise 
in the angle between the stem and the leaf. 
B 
Bacil'lus (Lat. bacillum, little stick): a rod-shaped bacterium. 
Bacter'ia (Gk. bacteron, a stick): the smallest and simplest plants. 
Balanced aquarium : one in which plant and animal life supply 
each other's needs. 
Balanced diet : one in which there are the correct amounts of car- 
bohydrates, proteins, and fats. 
Ball-and-socket joint : one in which the enlarged end of one bone 
fits into a depression in another, allowing free motion. 
Bast : tough fibers in the inner bark of trees and other plants; part 
of the phloem. 
Beetle : an insect having hard wing covers; one of the Orthoptera. 
Belly of muscle : the middle portion. 
Bien'nial (Lat. bi, two, + annus, year): a plant which grows and 
stores food the first year and bears fruit the second year. 
Bile : the fluid secreted by the liver. 
Biological diseases : those caused by organisms. 
Biol'ogy (Gk. bios, life, + logos, a talk or discourse): the study of 
living things. 
Bi'valve (Lat. bi, two, + valva, leaf of a door): a mollusk having 
two valves or shells, as a clam. 
Bladder : the muscular sac in which urine collects. 
Blade : the expanded portion of a leaf. 
Blas'tula (Gk. blastos, a bud): the hollow sphere stage in the de- 
velopment of certain eggs. 
Blight : disease of plants caused by certain fungi. 674 
GLOSSARY 
Body cavity : the space in which the vital organs are contained. 
Bract (Lat. bractea, a thin metal plate): a small, leaf-like growth 
at the base of the pedicel of a flower. 
Brain : the compact portion of the nervous system; in vertebrates, 
the part inclosed in the skull. 
Bronchus, pl. bronchi (Gk. bronchos, windpipe): one of the two large 
subdivisions of the trachea. 
Bud : an undeveloped branch or flower; an outgrowth on sponge, 
hydra, and yeast. 
Budding : a form of grafting; the insertion of a bud of one tree 
under the bark of another. 
Bulb : a cluster of thickened leaf-bases attached to a reduced stem, 
and surrounding a bud, as in onion, hyacinth, etc. 
By-product: something produced incidentally in a manufacturing 
process, as oxygen in photosynthesis. 
C 
Cal'orie (Lat. calere, to be hot): a unit employed in estimating the 
kind and amount of food necessary to maintain the body at its best. 
It is the amount of heat required to raise one kilogram of water one 
degree Centigrade. 
Ca'lyx (Greek, kalyx, cover): the outermost row of leaves or parts 
of a flower, usually green. 
Cam'bium (Lat. cambire, to exchange): the active, growing cells be- 
tween the xylem and the phloem in the fibrovascular bundle of di- 
cotyledonous plants. 
Cap'illary (Lat. capillus, a hair): the microscopic blood vessels 
which fill the spaces between the ends of arteries and the beginnings 
of veins. 
CXr'apace (Sp. carapacho, a covering): the shell-like dorsal covering 
of crustaceans and turtles. 
Carbohy'drate (Lat. carbo, coal; Gk. hydor, water): the class of 
food stuffs made of carbon, hydrogen, and oxygen, the hydrogen and 
oxygen being in the same proportion as water. 
Carbon diox'ide (Lat. carbo, coal; Gk. di, two; oxys, acid): a gas 
formed as a product of respiration and combustion. 
Carniv'orous (Lat. caro (carnis}, flesh; vo'rare, to eat): flesh-eating 
animals and plants. 
Car'rier : a person who is immune to certain diseases the bacteria 
of which infest him, but capable of infecting others. 
Car'tilage (Lat. cartilago, gristle): the elastic animal tissue forming 
parts of organs or bones. GLOSSARY 
675 
Ca'sein (Lat. caseus, cheese): the form of protein found in the curd 
of milk. 
Cat'erpillar (Lat. catta, cat; pilus, hair): the active, larval stage 
in the metamorphosis of a lepidopterous insect; often covered with hair. 
Caud'al (Lat. cauda, tail): pertaining to the tail. 
Cell (Lat. cella, a small room): the unit of structure and function 
of living things. A mass of protoplasm inclosing a nucleus, and usually 
inclosed in a cell wall. 
Cellulose (Lat. cellula, a little cell): an organic substance usually 
found in the walls of plant cells. 
Cen'tipede (Lat. centum, one hundred; Gk. pod, root of pous, foot): 
a small arthropod having two legs on each segment. 
Cere (Lat. cera, wax): a fleshy growth at the base of the bill of some 
birds. 
Cerebel'lum (Lat. cerebellum, little brain): the part of the brain 
behind the cerebrum in man, and overlying the midbrain. 
Cer'ebrum (Lat. cerebrum, the brain): the anterior part of the 
brain. 
Char'acter (Gk. charakter, an engraved mark or stamp): a trait or 
peculiarity passed on from parent to offspring. Characters may be 
dominant, or evident, or recessive, not showing for the generation or 
time being. 
Chela (Gk. chele, claw): the large pincers of a crayfish or lobster. 
Chirop'tera (Gk. cheir, hand, + pteron, wing): the "hand-winged" 
mammals, as bats. 
Chitin (Gk. chiton, a gown or tunic): the outer covering of the bodies 
of some animals, as insects. 
Chlor'ophyll (Gk. Moros, green, + phyllos, leaf): the green color- 
ing matter characteristic of plants; the substance which enables them 
to perform photosynthesis. 
Chlor'oplast (Gk. Moros, green, + plastos, molded): the granules 
in the protoplasm of a cell which contain chlorophyll. 
Chrys'alis (Gk. chrysos, gold): the quiescent stage in the develop- 
ment of a moth or butterfly; the pupa inclosed in a thin, smooth case. 
Cil'ium (Lat. cilium, an eyelid with eyelashes): a tiny hair-like pro- 
jection of protoplasm attached to some portion of the surface of a cell. 
Clav'icle (Lat. clavicula, a little key): the collar bone, so named from 
its shape. 
Cleistog'amous (Gk. kleistos, closed, + gamos, marriage) flowers : 
those which appear usually below the surface and are specially modi- 
fied for self-fertilization. Violets produce cleistogamous flowers after 
the others. 676 
GLOSSARY 
Cloa'ca (Lat. cloaca, sewer): the lower end of the digestive tract 
which receives also wastes from the kidneys and the reproductive prod- 
ucts in some vertebrates, as frogs and birds; the central cavity of a 
sponge. 
Coal : a substance used for fuel, consisting largely of carbon formed 
from the remains of ancient vegetation. 
Coc'cus (Gk. kokkus, berry): a spherical bacterium. 
Cocoon' (Lat. concha, shell): the hairy or silken covering of the 
pupa of some insects; the egg case of spiders and earthworms. 
Coe'lom (Gk. koilos, hollow): the body cavity; the part of the body 
in which the organs lie. 
Coleop'tera (Gk. coleos, sheath, + pteron, wing): an order of in- 
sects having hard w'ing covers over the flying or true wings; the beetles. 
Commu'nicable (Lat. communico, hold in common) diseases : 
those which can be given by one person to another. True of certain 
biological diseases, as diphtheria. 
Compound' eyes (Lat. compono, put together): an eye made up of 
many separate facets or parts, as in insects and crayfish. 
Conjuga'tion (Lat. con, with, + jugare, to join): the temporary 
union of two similar cells for the purpose of exchanging nuclear proto- 
plasm, as in paramecium. 
Conserva'tion of energy : Energy can neither be created nor 
destroyed. Any given amount may be made to assume different forms, 
as heat, light, motion. 
Conserva'tion of matter : Matter can neither be created nor de- 
stroyed. Its form may be changed, as water which may exist as a gas, 
a liquid, or a solid; wood may be burned, or changed into water, smoke, 
and ashes. 
Contract'ile vac'uole : a cell organ found in many Protozoa, which 
appears and disappears regularly. 
Corm (Gk. kormos, tree trunk): a solid, underground stem for stor- 
age of food, as Jack-in-the-pulpit. 
Corol'la (Lat. corolla, crown): the petals of a flower taken as a 
whole. 
Cor'puscle (Lat. corpusculum, a little body): the floating cells in 
the blood, red and white. 
Cor'tex (Lat. cortex, bark): the fleshy portion of a root surrounding 
the central cylinder and covered by epidermis. 
Cor'ymb (Gk. korymbos, top): a flat-topped or rounded (convex) 
flowrer cluster. 
Cot'yledon (Gk. kotyledon, a socket): the seed leaves of a plant. 
Monocotyledonous plants have only one, dicotyledonous plants have two. GLOSSARY 
677 
Cross-fertiliza'tion : the union of the nuclei of the egg of one in- 
dividual and the sperm of another. 
Cross-pollina'tion : the receiving of pollen from a different plant 
by the pistil. 
Crusta'cea (Lat. crusta, a crust) : a group of animals covered with 
a hard exoskeleton, as crayfish. 
Cu'lex : the scientific name of a very common, non-disease-bearing 
mosquito. 
Culture : a controlled growth of bacteria, fungi, or Protozoa, usually 
in a prepared nutrient medium. A pure culture contains only one 
kind of organism. 
Cu'tin (Lat. cutis, skin): the transparent waxy covering of leaves. 
Cy'toplasm (kytos, vessel, + plasma, anything formed): the form 
of protoplasm which makes up the main part of a cell. It incloses the 
nucleus, and is inclosed by the cell wall. 
D 
Decid'uous (Lat. de, down, + cado, fall) leaves : those which fall 
from the tree in autumn. 
Decomposition (Lat. de, from, + cum (com), together, + ponere, to 
place): the act of separating into constituent parts; decay or rotting. 
Dehis'cent (Lat. de, from, + hiscere, to open): a term applied to 
fruits that open, as pod, capsule, etc. 
Deliques'cent (Lat. deliquescere, to melt or dissolve): a term ap- 
plied to trees the trunks of which subdivide repeatedly. 
Demonstration (Lat. de, fully, + monstro, show): an orderly 
sequence of events, repeated by some one who wishes to explain or il- 
lustrate certain facts to learners. In a demonstration, the facts are 
already known. In an experiment, they are not known. 
Den'tine (Lat. den^s, a tooth): the inner portion of a tooth. 
Deod'orizer (Lat. de, from. + odor, smell): a substance used to 
modify or disguise odors. 
Dermis (Gk. derma, skin): the true skin, lying beneath the epi- 
dermis. 
Di'aphragm (Gk. diaphragma, a partition wall): the sheet of muscle 
which separates the chest cavity from the abdominal. 
Di'astase (Gk. diastasis, separation): the enzyme or ferment in 
plants which converts starch to grape sugar (glucose). 
Di'cotyle'don (Gk. di, two, + kotyledon, a socket): a plant which 
bears seeds having two cotyledons, as bean. 
Diges'tion (Lat. digestio, the dissolving of food): the process of pre- 
paring food for absorption. 678 
GLOSSARY 
Dip'tera (Gk. di, twice, + pteron, wing): an order of insects which 
has only two wings, as fly and mosquito. 
Disc (Gk. discus, a disc) flowers : the central portion of certain 
1 ' flowers" like the daisy or sunflower. 
Disinfect'ant (Lat. dis, apart, + inficio, make): a substance used to 
destroy harmful bacteria. 
Dominant (Lat. dominare, to rule) characters : those which are 
most conspicuous in the hybrid. 
Dor'mancy (Lat. dormio, sleep): the state of quiescence charac- 
teristic of seeds before germination. 
Dor'sal (Lat. dorsum, the back): pertaining to the back. 
Drone : the male of bees and ants. 
Dry farming : the raising of crops in semi-arid regions. 
Dry fruits: not fleshy. Nuts, cereals, pods, etc. 
Ductless glands : those which pour their secretions directly into 
the blood, as thymus and adrenal glands. 
E 
Ec'toderm (Gk. ectos, outside, + derma, skin): the outer layer of 
cells of animals. 
Ec'toplasm (Gk. ectos, outside, + plasma, thing molded): the out- 
side layer of unicellular organisms. 
Edenta'ta (Lat. e, out, + den^s, tooth): a group of mammals which 
have no teeth. 
Ef'ferent (Lat. e, out, + fero, bear) fibers : the fibers that carry 
impulses away from the brain, the motor fibers. 
Egg : the female element in sexual reproduction; the ovum. 
El'ement (Lat. elementum, first principle): a substance which can- 
not be further simplified by any known means; one of the simple sub- 
stances which, combined with others, make up the objects around us, 
both organic and inorganic. 
Em'bryo (Gk. embryon, an embryo): an organism in its early stages 
of development. 
Embryol'ogy (Gk. embryon, an embryo, + logos, a talk or discourse): 
the study of the development of organisms. 
Enam'el : the hard outer covering of the upper part of the teeth. 
Encyst'ment (Gk. en, in, + kystis, a bladder): the act of being in- 
closed in a resistant covering; forming a cyst. 
En'doderm (Gk. endon, within, + derma, skin): the inner layer of 
cells in sponge, hydra, or an embryo. 
En'doplasm (Gk. endon, within, + plasma, substance): the inner 
portion of the protoplasm in a one-celled animal. GLOSSARY 
679 
En'doskel'eton (Gk. endon, within, + skeleton, a dried body): a 
skeleton within the body, as in man. 
En'dosperm (Gk. endon, within, + sperma, a seed): the food that is 
stored near the embryo, as in a grain of corn. 
En'ergy (Gk. energos, at work): the power or ability to perform work. 
En'tomol'ogist (Gk. entomon, insect, + logos, talk or discourse): 
a person who studies insects. 
Envir'onment (Fr. environ, around): the surroundings of an organ- 
ism. 
En'zyme (Gk. en, in, + zyme, leaven): a substance secreted by or- 
ganisms and inducing chemical changes, as digestion and fermentation. 
Ephemer'ida (Gk. ephemeras, for a day): an order of insects which 
live but a few hours. 
Ep'idem'ic (Gk. epi, upon, + demos, the people): a disease that is 
widespread, affecting many people at the same time. 
Epider mis (Gk. epi, upon, + derma, skin) : the covering of the true 
skin; the outer layer. 
Epiglot'tis (Gk. epi, upon, + glottis, glottis): the lid which closes 
the opening into the trachea when anything is swallowed. 
Eros'ion (Lat. erodere, to gnaw off): the wearing away of a sub- 
stance, especially soil, by the action of the natural elements, as water. 
Essen'tial parts (of a flower): the stamens and pistils, both of 
which are necessary in forming a seed. 
Eugen'ics (Gk. eugenes, well born): the study of heredity in its re- 
lation to the improvement of offspring. 
Eusta'chian tubes : the tubes which connect the middle ear with 
the throat. Named for Eustachius. 
Evergreens : plants which retain their leaves for several years; 
the cone-bearing trees, in general. 
Evolu'tion (Lat. e, out, + volvo, roll): the development of com- 
plex forms from simple ones; organic descent; the theory that accounts 
for present forms of life by tracing them from simpler forms which ex- 
isted in the past. 
Excre'tion (Lat. excretus, separated out): the process of removing 
waste products from the protoplasm; the products so removed. 
Excur'rent (Lat. ex, out, + currere, to run) stem : a stem which 
extends from base to tip without dividing, as spruce, cedar, etc. 
Exhal'ent (Lat. ex, out, + halo, breathe) pore : the central 
opening at the top of a sponge through which water is passed outward. 
Ex'oskeleton (Gk. ex, out, + skeleton, a dried body): the outer, 
crustaceous or horny covering of animals such as crayfish and insects. 
Experiment (Lat. experior, try): a test under controlled condi- 680 
GLOSSARY 
tions for the purpose of discovering new facts, truths, or relations. In 
a real experiment, the result is not known beforehand to the person 
investigating. 
Expira'tion (Lat. ex, out, + spiro, breathe): the process of emptying 
the lungs of air in breathing. 
Exten'sors (Lat. ex, out, + tendo, stretch): the muscles which 
straighten an appendage at the joint, as arm. 
F 
Fangs : the organs through which spiders, snakes, and other animals 
inject poison or venom into their prey or enemies. 
Fas'cicled (Lat. fasciculus, a little bundle) roots : the clustered, 
fleshy roots of dahlia and other plants. 
Fatigue' (Lat. fati^o, tire) : the effect of exertion or other stimu- 
lation of cells or organs. 
Fats : one of the common classes of nutrients, containing much car- 
bon and hydrogen and little oxygen. 
Feathers : the characteristic covering of birds. 
Fe'ces (Lat. faeces, dregs): the wastes from the alimentary canal; 
excrement. 
Feelers : antennae; the long, slender, jointed projections from the 
head found chiefly in crustaceans. 
Fehling's solution : a substance used to determine the presence of 
glucose or grape sugar. Several formulas are in common use. 
Fe'mur: the long bone of the lower limb in vertebrates; the large 
portion of the leg of a grasshopper. 
Fer'ment : an enzyme; a substance which produces fermentation. 
Fertiliza'tion (Lat. fertilis, from fero, bear): the union of the 
sperm nucleus with the egg nucleus in forming a new individual or 
organism. 
Fer'tilizer : a substance added to the soil to promote plant growth. 
Fibrin'ogen (Fr. fibre, a fiber): the substance in the blood which 
induces clotting by the production of fibers when exposed to air. 
Fi'brous (Fr. fibre, a fiber) roots : those composed of many slender 
fibers, as grass. 
Fibrovas'cular bundles : the conductive system of plants. A 
fibrovascular bundle consists of xylem cells which communicate by 
means of perforations in the sides of their thick walls, and phloem cells 
which are thin-walled and perforated at the ends. Other cells, non- 
conductive, are found in or near the bundle. 
Fil'ament (Lat. filum, thread): the slender stalk of a stamen; any 
thread-like projection. GLOSSARY 
681 
Fin : a locomotor organ characteristic of fishes and used for loco- 
motion, balancing, and steering. 
Fis'sion (Lat. findere, to split): division into two smaller cells by a 
process of splitting or pinching in two. 
Flac'cid (Lat. flaccus, flabby): a soft or relaxed condition of a cell 
due usually to shortage of water. 
Flagel'lum (Lat. flagellum, a whip): a long protoplasmic projection, 
used chiefly for locomotion. 
Flatfoot: a common disease caused by the breaking down of one 
or more of the arches. 
Flatworms : a group of unsegmented worm-like animals, many of 
which are parasitic, as liver fluke and tapeworm. 
Fleshy fruits: those that have the seeds surrounded by an edible, 
juicy layer, as pome (apple), drupe (plum). 
Flex'ors (Lat. flexus (flecto), bend): muscles that bend the joints; 
the set that work in opposition to extensors. 
Flipper : the fore limb of a seal or other aquatic mammal, modified 
as a swimming organ. 
Flower : the organ of a plant which produces fruit containing seeds; 
or one of the essential parts of such an organ, as staminate flowers of 
corn, pistillate flowers of willow. 
Food : a substance that furnishes material for the growth or repair 
of an organism, or that yields energy for it. 
Forestry : the study and practice of producing successive crops of 
trees from a given tract. 
Fossils: the stone-like remains of plants and animals no longer 
living on the earth. 
Fruit: the ripened ovary and its contents. In some fruits traces 
of parts of the flower may be seen adhering to them. 
Fry : young fishes just able to take care of themselves. 
Func'tion (Lat. functio, performance): the normal action of any 
organ or set of organs; use. 
Fundament'al func'tions : those on which an organism depends 
for existence, as respiration, excretion, etc. 
Fun'gus (Lat. fungus, mushroom): a plant which lacks chlorophyll. 
Fungi are dependent on prepared (organic) food, dead or alive. 
G 
Gall : (Lat. galla, gallnut): a growth produced on certain leaves by 
the action of insects; the bile. 
Gall bladder : the sac in which gall or bile is stored temporarily. 
Gan'glion (Gk. ganglion, tumor): a collection of nerve cells. 682 
GLOSSARY 
Gas : one of the forms in which matter exists, as oxygen, hydrogen. 
Gas'tric (Gk. gaster, stomach): pertaining to the stomach, as gastric 
glands. 
Gas'trula (Gk. gaster, stomach): the two-layered stage in the de- 
velopment of an egg into an embryo. 
Generation (Lat. generatus, from genero, beget): the persons 
existing at one time or period. Applied also to plants and animals. 
Gen'us (Lat. genero, beget): a group of organisms including one or 
more species. Used in classifying plants and animals. 
Germ (Lat. germen, sprig): a microorganism; the rudimentary 
vital element; an embryo. 
Germina'tion (Lat. germinatus, from germino, sprout): the be- 
ginning of growth of a seed or pollen. This is commonly used to describe 
the growth of a plant from a seed. It more properly describes the 
growth of the embryo within the seed. 
Gill rakers : projections on the gill arches of some fishes to assist 
in gathering food. 
Gill slits : openings in the neck through which water, taken into 
the mouth, passes out over the gills, as in fishes. 
Gills : thin, finely divided organs of aquatic vertebrates, used to 
gather oxygen. 
Gir'dle : the bones which attach vertebrate limbs to the axial skele - 
ton. The anterior is called the pectoral and the posterior the pelvic 
girdle; to encircle with a deep cut or by removing the bark, as to girdle 
a tree. 
Giz'zard (Lat. gigeria, cooked entrails of poultry): the muscular 
chamber where food is ground. A characteristic organ of birds. 
Gland : an organ which produces a substance for use in the body, or 
for removal from it; examples, salivary gland, kidney. 
Glomer'ulus (Lat. glomero, make a ball): minute rounded bodies 
in the cortex of a kidney; a knot of blood vessels; a Malpighian body. 
Glot'tis (Gk. glotta, tongue): the opening into the trachea. 
Glu'cose (Gk. glykys, sweet): the form of sugar found in fruits; 
the product of the digestion of starch. 
Glu'ten (Lat. gluten, glue): the proteid substance in cereals which 
makes them sticky when wet and crushed. 
Gly'cerin (Gk. glykeros, sweet, from glykys~): the sweet substance 
resulting from the digestion of natural fats. 
Gly'cogen (Gk. glykys, sweet, + gen, producing): animal starch, 
stored in the liver. 
Gon'ad : an undeveloped sex organ, or one which cannot be recog- 
nized as either male or female in the non-reproductive season. GLOSSARY 
683 
Gon'ium : a very small animal which consists of a colonial group of 
eight cells, each practically independent. 
Graft'ing : the process of inserting a small piece (twig) of one plant 
(the scion) into a slit in a larger one (the stock) and protecting it till the 
parts grow together. 
Grain (Lat. granum, grain): one of the cereals, or cereals in general; 
a kernel of corn; the markings on wood due to annual rings and med- 
ullary (wood) rays. 
Grav'el : small stones or pebbles, usually rounded and often mixed 
with sand. 
Grav'ity (Lat. gravis, heavy): the force which tends to draw ob- 
jects towards the center of the earth. 
Green glands : excretory organs of a crayfish, found in the head 
region. 
Gr^en manuring : the process of plowing under a crop of some 
leguminous plant, as clover, for the sake of the nitrogen which has been 
gathered by bacteria living on its roots. 
Grub : the larva of certain beetles, as white grub, the larva of the 
May beetle. 
H 
Hab'it (Lat. habitus, condition): a tendency towards an action or 
condition which, by repetition, has become spontaneous. 
Hab'itat (Lat. habito, inhabit): the region where any organism or 
group of organisms is usually found; the place where it lives. 
H^moglo'bin (Gk. haima, blood, + Lat. globus, globe): the red 
coloring matter in the small blood corpuscles. 
TLe'morrhage (Gk. haima, blood, + rhegnymi, break): the dis- 
charge of blood from a ruptured blood vessel. 
Hard pal'ate : the bony part of the roof of the mouth. 
Head: the division of the body which contains the brain; a collec- 
tion of small flowers; the collection of grains which make up the fruit 
of cereals. 
Health : the condition resulting from the normal performance of all 
the life functions. 
Hemip'tera (Gk. hemi, half, + pteron, wing): an order of insects 
which has the anterior part of its wings hard and the posterior part 
membranous. 
Herbiv'orous (Lat. herba, grass, + voro, eat): animals which feed 
upon grass and other plants. 
Hered'ity (Lat. heres, heir): the passing on to offspring of char- 
acters of parents or other ancestors. 684 
GLOSSARY 
Hibernation (Lat. hiems, winter): the condition induced by severe 
cold in the case of some animals; a death-like torpor and rigidity 
brought about by extreme cold. 
Hi'lum : the scar on a seed showing where it was attached to the 
fruit. 
Hinge joint: one which admits only of back-and-forth motion, as 
the elbow. 
Homop'tera (Gk. homos, same, + pteron, wing): a group of insects 
having their wings of the same texture throughout, in contrast to other 
Hemiptera. 
Hon'ey : the partly digested food of bees. They suck up nectar 
which is retained in the crop till partially digested, after which it is 
pumped up and stored in cells of wax. 
Hook'worm : a small parasitic, unsegmented, round worm found in 
the intestine of man, sheep, and other animals. 
Hor'mones (Gk. hormaein, to excite): substances secreted directly 
into the blood in one part of the body which are carried by the cir- 
culation and incite action in another part of the body; chemical 
messengers. 
Host (Lat. hospes, entertainer): the larger organism on or in which a 
smaller, dependent one (parasite) lives. 
Hit'merus (Lat. humerus, shoulder): the larger bone of the upper 
arm. 
Hu'mor (Lat. humerc, to be moist): the transparent liquids of the 
eyeball. 
Hu'mus (Lat. humus, ground): the substances in the soil formed by 
the decay of organic matter; vegetable mold. 
Hy'brid (Lat. hybrida, mongrel): the offspring of parents of two 
different species or varieties. The mule is a hybrid. 
Hy'dra (Gk. hydor, water): a two-layered aquatic animal; a polyp. 
Hy'drogen (Gk. hydor, water, + gen, create): one of the two elements 
that enter into water; the lightest known substance. 
Hy'giene (Gk. hygeia, health): the study of health, especially as 
to maintaining health by observing proper conditions. 
Hymenop'tera (Gk. hymen, a membrane, + pteron, wing): an order 
of insects (including bees and wasps) which have membranous wings. 
Hy'piee (Gk. hyphai, a web): the single strands or threads which 
make up the body of a fungus. 
Hy'pocot'yl (Gk. hypo, under, + kotyledon, socket): the part of a 
developing plant embryo which lies between the stem and the root. 
Hypophar'ynx (Gk. hypo, under, + pharynx, throat): the tongue- 
like organ of a grasshopper. GLOSSARY 
685 
I 
Ichneu'mon (Gk. ichneuo, hunt): a hymenopterous insect which 
lays its eggs on the larvae of other insects or in them; a helpful para- 
sitic insect. 
Imbecil'ity (Lat. imbecillus, weak): the state or condition of being 
far below normal in mental development; feeble-mindedness. 
Immu'nity (Lat. immunis, free from duty): the condition which 
prevents a person from "taking" an infectious disease. 
Incis'or (Lat. incido, cut into): a cutting tooth. In gnawing 
animals the incisors have chisel edges. 
In'current (Lat. in, in, + curro, run) siphon : the tube through 
which water enters the gill chamber of clams. 
Indefinite annual growth : the forming of new wood through- 
out the whole growing season, as in sumac. 
Indehis'cent (Lat. in, not, + dehiscere, to open) fruits : those that 
do not open, as nut, grain of corn, akene. 
Indeter'minate (Lat. in, not, + de, completely, + termino, ter- 
minate) in flores'cence (Lat. in, in, + Jloreo, bloom): a form of 
flowering in which the axis continues to grow and new flowers continue 
to form. A plantain illustrates it. 
Infus'ion (Lat. in, in, + fusus, from fundo, pour): the process of 
steeping a substance in a liquid for the purpose of extracting its medic- 
inal or other qualities; the liquid extract so obtained, as hay infusion. 
In'halent (Lat. in, in, + halo, breathe) pores : the mouths of 
tubes which conduct water inward through the walls of a simple sponge. 
Inocula'tion : the introduction of a virus, as of smallpox, into the 
system through the skin. 
Inorganic (Lat. in, not, + organum, organ) matter: that which 
has not been formed by living (organic) processes. 
In'sect (Lat. in, in, 4- sectum, cut): a group of small animals having 
three distinctly marked-off body regions. 
Insectiv'ora (Lat. insectum, insect, + voro, to eat): an order of 
insect-eating vertebrates, including moles and shrews. 
Inser'tion (Lat. insertus, from in, in, + sero, join): the place of at- 
tachment of a muscle. 
Inspiration (Lat. in, in, + spiro, breathe): the act of taking air 
into the lungs. 
In'sulin : a newly discovered remedy for the treatment of diabetes. 
Integ'ument (Lat. in, in, + tego, cover): an outer covering or en- 
velop, as the skin. 
Intes'tine (Lat. intestinus, internal): that portion of the alimen- 686 
GLOSSARY 
tary canal in vertebrates between the stomach and the anus. There 
are two divisions or sections, the small intestine and the large intestine. 
Invert'ebrates (Lat. in, not, + vertere, to turn): all animals which 
lack a vertebral column, as worms, insects, mollusks. 
Invol'untary (Lat. in, not, + voluntas, from volo, will) muscles : 
those which are not under the control of the will, as the muscles of the 
intestine. 
I'odine (iodin): one of the elements. It is used as a test for the 
presence of starch which it turns blue, also as an antiseptic and a pre- 
ventive of goiter. 
I'ris (Gk. iris, rainbow): the colored portion of the eye. 
Irritabil'ity (Lat. irritabilis, from irrito, excite): the property of 
reacting to stimuli; a life function. 
J 
Jellyfish : a soft, jelly-like animal related to hydra. 
Joint (Lat. jungo, join): the place where two bones meet; an 
articulation. 
K 
Keel : the projection on the breastbone of birds for the attachment 
of muscles for moving the wings. 
Kid'ney : a gland which secretes urine. 
Kinet'ic (Gk. kinein, to move) energy : that form of energy em- 
ployed in producing motion. 
L 
La'bium (Lat. labium, lip): the lower "lip" of a grasshopper's mouth. 
La'brum (Lat. labrum, lip): the upper "lip" of a grasshopper's 
mouth. 
Lac'teals (Lat. lac, milk): the vessels which carry the absorbed food 
from the intestine to the vein which receives it. 
Lar'va (Lat. larva, a ghost): the eating and growing stage in the 
complete metamorphosis of some insects, as moths and butterflies. 
Lar'ynx (Gk. larynx, gullet): the portion of the trachea which con- 
tains the vocal cords; the voice box; "Adam's apple." 
La'tent (Lat. lateo, lie hidden) energy : that form of energy which, 
temporarily, is not at work, as a tightly wound watch spring. 
Lat'eral (Lat. lotus, side) bud : one which is on the side of a stem. 
Lay'ering : the covering of the nodes of a stem with dirt to induce it 
to produce roots; a means of propagating such plants as grape vines. 
Leaf mosa'ic : the arrangement of leaves to cover all spaces, as ivy 
on a wall. GLOSSARY 
687 
Leath'er (A.-S. lether, leather): the skin of an animal when tanned 
or otherwise prepared for use. 
Legumes' (Lat. legere, to gather): plants which have pods for fruits; 
the seeds of such plants, as peas, beans, etc. 
Legu'min : the proteid substance found in seeds of the pulse (pea) 
family. 
Len'ticel : an opening in bark for the admission of air. 
Lep'idop'tera (Gk. lepis, scale, + pteron, wing): the order of in- 
sects characterized by having scaly wings, as moths and butterflies. 
Life cycle : the stages of development, maturity, and decline through 
which every organism passes. 
Life functions : the various physical processes upon which the 
continuance of life depends; the vital processes, as digestion, respira- 
tion, etc. 
Lig'ament (Lat. ligare, to bind): a band of tissue which binds one 
bone to another. 
Lip'oid (Gk. lipos, fat, + eikos, like): a substance found in abun- 
dance in cells of the nervous system which is dissolved by amesthetics 
and narcotics. 
Liq'uid (Lat. liquere, to be fluid): a form of matter in which the par- 
ticles move easily upon one another, as water, and take the shape of 
the container. 
Liv'er : the largest organ of the body, a gland which secrets bile, 
stores glycogen, and performs other functions. 
Loam : a form of soil containing much humus (which see). 
Locomo'tion (Lat. locus, place, + motus, fr. moveo, move): moving 
from one place to another. In many animals locomotion is essential 
in food-getting. 
Lymph (Lat. lympha, clear water): the fluid resembling plasma which 
fills intercellular spaces. The watery substance in a blister is lymph. 
Lymphat'ic (Lat. lympha, clear water): a vessel that conveys lymph; 
pertaining to lymph. 
M 
Maggot : the legless larva of a fly. 
Magnes'ium : one of the elements a trace of which is found in proto- 
plasm. 
Mala'ria (Lat. malus, bad, fl- aer, air): a biological disease caused 
by parasitic protozobns which live in the body of the mosquito known 
as Anopheles during part of their life history, and part in the blood of 
man to which they are transmitted by the bite of a mosquito. Malaria 
was once thought to be due to breathing bad air, especially night air. 688 
GLOSSARY 
Males: individuals producing sperms. 
Mam'mary (Lat. mamma, breast) glands: the milk-secreting glands 
which are characteristic of mammals. 
Man'dible (Lat. mandere, to chew): the cutting part of the mouths 
of crustaceans. 
Marsu'pials (Gk. marsipion, a little pouch): an order of mammals 
having a pouch in which the young are carried, as opossum, kangaroo. 
Maxil'la (Lat. maxilla, jaw): one of the mouth-parts of crustaceans. 
Maxil'liped (Lat. maxilla, jaw, + pes, foot): an appendage near 
the mouth of a crustacean which assists in getting or passing food. 
Meas'uring worms: the larvae of certain moths which move by 
looping their bodies. 
Medul'la (Lat. medius, middle) oblongata : the posterior part of 
the brain, connecting it with the spinal cord. 
Med'ullary (Lat. medulla, pith) rays : thin bundles of wood cells 
extending from the meristem to or towards the center; wood rays. 
Men'delism : a law of heredity first announced or discovered by 
Gregor Mendel. 
Mer'istem (Gk. meristos, divisible): the actively growing tissue 
found in the tips of roots and stems. 
Mes'entery (Gk. mesos, middle, + enteron, intestine): a fold of 
tissue which suspends the intestine from the dorsal wall of the abdomen. 
Mesogle'a (Gk. mesos, middle, + glorios, glutinous substance): the 
middle, non-cellular layer of hydra. 
Mes'ophyll (Gk. mesos, middle, + phyllon, leaf): the middle portion 
of a leaf, consisting of irregular, loosely packed cells. 
Mesotho'rax (Gk. mesos, middle, + thorax, thorax): the middle 
section of the thorax of an insect. It has one pair of wings and the 
second pair of legs on it. 
Metamor'phosis (Gk. meta, beyond, + morphe, form): a life history 
in which the organism passes through several changes of form, as butter- 
fly, frog. 
Metatho'rax (Gk. meta, beyond, + thorax, thorax): the third divi- 
sion of an insect's thorax. It bears the last pair of legs, and the second 
pair of wings, if any. 
Mi'crobe (Gk. mikros, small, + bios, life): a microscopic organism; 
a bacterium. 
Mi'cropyle (Gk. mikros, small, + pyle, gate): the opening in the 
testa of an ovule through which the pollen tube enters. 
Mid'rib : the main vein or rib of a leaf. 
Migra'tion (Lat. migro, move): the act of changing a dwelling place 
from one locality to another, as birds, salmon. GLOSSARY 
689 
Mil'dew : a fungus which causes decay and disease. 
Milt: the sperms of a fish. 
Mim'icry (Gk. mimikos, imitative): resemblances in form or color 
which some organisms show to other objects, to protect them. 
Mix'ture (Lat. miscio, mix): a combination of several ingredients 
in which each retains its own individuality. 
Mol'ecule (Lat. dim. of moles, mass): the smallest part of a sub- 
stance that can exist without losing its identity. 
Mol'lusks (Lat. mollis, soft): a group of animals having soft bodies, 
usually covered by one or two shells. 
Molt : to cast off, as skin in snakes, feathers in birds, skin in larvae. 
Monocot'yledon (Gk. monos, single, + kotyledon, socket): a plant 
which has only ono cotyledon, in its seeds, as corn. 
Mosa'ic vision : the image formed by the compound eye of an insect, 
each facet producing a part which fits in with others to make a complete 
picture. 
Moths : insects resembling butterflies; small lepidopterous insects 
which infest wool, cloth, fur, etc. 
Motor (Lat. moveo, move) fibers : nerve fibers which convey im- 
pulses from the brain to the muscles, producing motion. 
Movable joints : those capable of motion; opposed to sutures, 
which are immovable joints. 
Mu'cous (Lat. mucus, slime) membrane : the lining of the alimentary 
canal and respiratory tract. 
Mucus (Lat. mucus, slime): a slimy substance secreted by certain 
cells of the mucous membrane. 
Mule (Lat. mulus, mule): the offspring of a horse and a donkey. 
Mus'cle : an organ made up of contractile fibers, the function of 
which is to produce motion. 
Mush'room : a fleshy fungus, particularly the edible field mushroom 
vith pink gills. 
Mycel'ium (Gk. myces, mushroom): the (hyphal) threads which 
make up the body of a fungus. 
My'osin (Gk. myo, muscle): the form of protein which exists in 
muscle. 
Myriop'oda (Gk. myrioi, ten thousand, + pous, foot): a group of 
crustaceans having four legs on each segment. 
N 
Narcot'ic (Gk. narkotikos, making numb): a substance which dis- 
solves lipoid, dulls the senses, and in sufficient quantity produces in- 
sensibility. 690 
GLOSSARY 
Nat'ural immu'nity: the state of not being liable to "take" an 
infectious disease. 
Nat'ural selec'tion : the survival of those organisms which are best 
adapted to live under certain conditions, and the perishing of those less 
well adapted. 
Nec'tar (Gk. nectar, drink of the gods): the sweet fluid secreted 
by nectar glands in a flower; the substance from which bees make honey. 
Nerve fibers : the separate fibers of which a nerve is made up; the 
elongated processes of neurons (nerve cells). 
Nervous system : the system by means of which an animal becomes 
aware of its surroundings, and by which it adjusts itself to them; the 
coordinating system. 
Net-veined leaf: one in which the veins branch again and again, 
forming a network. 
Nic'titating (Lat. nictare, to wink) membrane : a thin, almost 
transparent inner eyelid found in certain vertebrates, as frog, bird, cat. 
Nissl bodies : granules in the bodies of nerve cells which disap- 
pear when the cell has been subject to frequent and prolonged stimu- 
lation. 
Ni'trogen : one of the elements in the form of gas. Besides consti- 
tuting about four fifths of the air, it is found in many organic substances, 
as protein. 
Node (Lat. nodus, knot): the places on a stem from which branches 
arise in dicotyledons, and leaves in monocotyledons. 
No'tochord (Gk. notos, the back, + chorde, a string): a rod in the 
back of the embryos of vertebrates around which the spinal column 
develops. 
Nour'ishment (Lat. nutrio, nurse or feed): that which sustains, or 
promotes growth in any way. 
Nucell'us (dim. of nux, nut): the tissue which fills the space not 
occupied by the embryo sac in an ovule. 
Nu'cleus (Lat. nucleus, a kernel): the center of vital activity in a 
cell; specialized protoplasm, part of which transmits heritable traits 
to offspring. 
Nut: a dry, indehiscent fruit with a hard pericarp, as walnut, hazel 
nut. 
Nu'trients (Lat. nutrio, nurse or feed): foods, such as starches, 
sugars, proteins, edible fats, and mineral matter, which contain the 
necessary elements for keeping the body in repair and making it grow; 
food compounds. 
Nutri'tion (Lat. nutrio, nurse or feed): the process by which growth 
is promoted and repairs made in living organisms. GLOSSARY 
691 
Nymph : an immature form of an insect, as grasshopper, which has 
incomplete metamorphosis. 
O 
Odona'ta (Gk. odontos, toothed): an order of insects including dragon 
flies and damsel flies. 
CEsoph'agus (Esophagus) (Gk. oiso, will bear, + phagein, to eat): 
the tube through which the food passes from the pharynx to the stom- 
ach ; the gullet. 
Oil : (Lat. oleum, oil): a liquid substance of organic origin, containing 
carbon, hydrogen, and oxygen, insoluble in water. A food substance 
(edible fat). 
Olfac'tory (Lat. oleo, smell, 4- facio, make) nerve : the nerve which 
supplies the organ of smell. 
Oper'culum (Lat. operculum, lid): the gill cover in fishes. 
Optic (Gk. optikos, sight) nerve : the nerve which conducts stimuli 
from the retina to the brain. 
Or'der (Lat. ordo, order): in classification, a group of organisms made 
up of several similar families. 
Or'gan (Gk. organon, instrument): any part of a plant or animal 
which performs some definite function. 
Organ'ic ash : the mineral matter left after the complete burning of 
plant or animal substances. 
Organ'ic substance : any substance made by plants or animals. 
Or'ganism (Gk. organon, instrument): a plant or an animal; a body 
composed of different organs performing special functions that are 
mutually dependent and essential to life. 
Or'igin (Lat. orior, rise): the attachment of a muscle nearest the 
center of the body. 
Orthop'tera (Gk. orthos, straight, + pteron, wing): a group of in- 
sects whose outer wings meet in a straight line in the middle of the back. 
It includes grasshoppers and crickets. 
Osmo'sis (Gk. osmos, pushing): the passing of soluble substances 
through a moist membrane, the greater movement being towards the 
denser liquid. 
O'vary (Lat. ovum, an egg): the organ in female animals and in 
plants which produces ova or eggs. 
O'viduct (Lat. ovum, egg, + duco, lead): the tube through which 
the eggs leave the body. 
O'vipos'itor (Lat. ovum, egg, + pono, place): the organ in insects 
by which eggs are thrust into a hard substance, as earth or wood. 
O'vule (Lat. ovulum, a little egg): the body, in plants, which con- 692 
GLOSSARY 
tains the egg cell. In case the egg cell is fertilized, the ovule develops 
into a seed or a fruit, as a grain of corn. 
Ov'um (Lat. ovum, egg): the sexual element produced by the female. 
Oxida'tion : the chemical union of oxygen with another substance. 
Ox'ygen : a gas, one of the elements. It is very abundant in nature, 
existing in the air as O2 and in combination with carbon and hydrogen 
and nitrogen to make sugars, starches, and protein. 
P 
Pal'ate (Lat. palatum, palate): the roof of the mouth. 
Palisade' cells : a row of cells longer than wide lying just beneath 
the epidermis of leaves. 
Palmately compound leaves : those in which the leaflets, five or 
more in number, arise from the top of the petiole. 
Palp (Lat. palpo, stroke): one of the sensory, jointed mouth parts 
of crayfish, insects, etc. 
Pan'creas (Gk. pas, all, + creas, flesh): a gland which secretes a 
liquid containing enzymes used in the intestinal digestion of food. 
Papil'la : a small projection, as from the surface of the tongue. 
Pap'pus (Gk. pappos, down): the tuft of down on the fruits of cer- 
tain plants, as thistle, dandelion, for distribution by wind. 
Parallel venation : the characteristic venation of monocotyledon- 
ous plants in which a number of veins of about'the same size run side 
by side from base to apex of the leaf. 
Par'asite (Gk. para, beside, + sitos, food): a small, dependent organ- 
ism which gets its food directly from a larger one, the host, without any 
benefit to the latter. 
Pasteuriza'tion (named from Pasteur, the originator): the process 
of killing most of the harmful bacteria in milk by heating it for a short 
time and cooling it quickly. 
Peat : a substance composed of partially carbonized organic matter, 
chiefly plants, found in bogs, and used for fuel when dry. 
Pec'toral (Lat. pectus, breast) girdle : the bones which support 
the anterior limbs of vertebrates and attach them to the trunk. 
Pedun'cle (Lat. pedunculus, little foot): the axis or stem to which 
the several flowers of an inflorescence are attached, as in lily-of-the- 
valley. 
Peg of hypocot'yl : the hard portion on the top of the arch of 
the hypocotyl which protects it from injury and assists it in piercing 
the soil. 
Pel'vic (Lat. pelvis, basin) girdle : the bones to which the posterior 
limbs of vertebrates are attached. GLOSSARY 
693 
Pel'vis (Lat. pelvis, basin): the broad, curved bones which support 
the organs of the abdomen. 
Pep'sin (Gk. pepsis, cooking): the ferment in the gastric juice which 
acts on protein. 
Pep'tone : the substance resulting from the digestion of protein by 
pepsin. 
Peren'nial (Lat. per, through, + annus, year): a plant which lives 
year after year, as a tree. 
Perfect flower : one which has both stamens and pistil, the essential 
organs. 
Pe'rianth (Gk. peri, around, + anthos, flower): the sepals and petals 
of a flower taken together when they are similar in shape and color, as 
in a lily. 
Pericar'dium (Gk. peri, around, + cardia, heart): the membranous 
sac surrounding and inclosing the heart. 
Perios'teum (Gk. peri, around, + osteon, bone): the membrane which 
covers bones and adheres to them. 
Peristal'sis (Gk. peri, around, + stalsis, constriction): the squirm- 
ing motion in the intestine caused by the contraction and relaxation of 
its muscles. 
Perspira'tion (Lat. per, through, + spiro, breathe): the watery se- 
cretion of the perspiratory glands; the substance secreted. 
Pet'al (Gk. petalon, leaf): one of the colored parts which make up 
the corolla of a flower. 
Pet'iole (Lat. petiolus, fruit stalk): the part of a leaf by which it is 
attached to the stem; the leaf stalk. 
Pha'gocytes (Gk. phagein, to eat, + cytos, sac): the white corpuscles 
of the blood which act as scavengers. 
Phar'ynx (Gk. pharynx, gullet): the cavity back of the mouth com- 
mon to the respiratory and digestive systems. 
Phlo'em (Gk. phloios, inner bark): the outer part of a fibrovascular 
bundle in a dicotyledonous plant. 
Phos'phorus (Gk. phos, light, + phero, bear): one of the elements 
found in minute quantities in protein. 
Photosyn'thesis (Gk. phos, light, + synthesis, putting together): 
the process of making starch, peculiar to green plants. 
Physiological oxidation : a slow combustion without flame or 
smoke, but with the production of heat and the formation of car- 
bon dioxide and water. It takes place constantly in all active 
organisms. 
Physiol'ogy (Gk. physis, nature, + logos, a talk): the study of the 
life processes of organisms. 694 
GLOSSARY 
Pistil (Lat. pistillum, from pinso, pound): the central part of a 
flower consisting of a stigma, style, and ovary (which see). 
Pith : the soft, spongy tissue in the center of a woody stem; 
the substance between the vascular bundles in a monocotyledonous 
stem. 
Placen'ta (Lat. placenta, cake): the tissue to which seeds are at- 
tached in the ovary of a plant. 
Plas'ma (Gk. plasma, a thing formed): the liquid portion of the 
blood of vertebrates. 
Plecop'tera (Gk. plectos, plaited, + pteron, wing): an order of 
insects having plaited wings, as stone flies. 
Plu'mule (Lat. plumula, little feather): the first bud of an embryo 
plant. 
Pod : the seed case of certain plants, as pea; a form of dry, dehiscent 
fruit. 
Poi'son (Lat. potio(n) from poto, drink): any substance which acts 
in a harmful manner when taken into the system of an organism. 
Pol'len (Lat. pollen, fine flour): the fine, powdery substance formed 
in the stamens of flowers. Each grain contains a sperm nucleus for 
fertilizing the egg cell in an ovule. 
Pol'lina'tion (Lat. pollen, fine flour): the act of receiving pollen 
on the stigma of a pistil. 
Pome (Lat. pomum, fruit): a fruit having thick, fleshy walls which 
inclose the papery pod containing the seeds, as apple, pear, quince. 
Por'tal (Lat. porta, gate) vein : the large vein that carries blood 
to the liver. 
Posterior (Lat. posterus, following) part: the hinder portion of 
an organism. 
Potas'sium : one of the elements found in minute quantities in proto- 
plasm. 
Poten'tial (Lat. potentia, power) energy : that which is temporarily 
inactive, as that in a tight spring. 
Praeco'cial (Lat. prae, before, + coquere, ripen): birds which are 
able to run soon after hatching. 
Preser'vative (Lat. prae, before, + servo, save): a substance added 
to food to prevent its "spoiling." Sugar in fruit, salt or smoke on meat 
are examples. 
Preserve' (Lat. prae, before, + servo, save): a place in which plants 
or animals, or both, may not be molested. 
Pri'mary (Lat. primus, first) foods : all plant foods, and such ani- 
mal foods as fish and oysters, where the animal gets its nourishment 
from some other source than primary foods and fodders. GLOSSARY 
695 
Pri'mary (Lat. primus, first) root: the first and usually the main 
root of a plant; the tap root. 
Pri'mates (Lat. primus, first): a group of animals which stand at 
the head in intelligence, as monkeys, apes, etc. Man, as an animal, is 
a Primate. 
Proboscid'ia (Gk. pro, before, + bosko, feed): a group of animals 
characterized by having a proboscis. 
Probos'cis (Gk. pro, before, + bosko, feed): an elongated appendage 
for gathering food. In insects, a coiled tube; in elephants, a pre- 
hensile nose and upper lip. 
Protec'tive coloration : coloration which fits in with the environ- 
ment, as toad, frog, grasshopper, tree frog. 
Protec'tive resem'blance : the resemblance of a harmless organ- 
ism to a harmful or distasteful one, as viceroy butterfly to monarch. 
Protein (Gk. protos, first): a compound of oxygen, hydrogen, car- 
bon, and nitrogen, with traces of other elements; a component of 
protoplasm; a nutrient. 
Protho'rax (Gk. pro, before, + thorax, chest): the first of the three 
regions of an insect's thorax. 
Pro'toplasm (Gk. protos, first, + plasma, molded form): the living 
substance composing the cells of plants and organisms. 
Protozo'a (Gk. protos, first, + zobn, animal'): one-celled animals. 
Pseudopod'ium (Gk. pseudes, false, + pous, foot): a projection of 
protoplasm used by protozobns for locomotion. 
Pto'maine (Gk. ptoma, corpse): a poisonous substance produced by 
the decomposition of animal matter. 
Pty'alin (Gk. ptyalon, spittle): the enzyme in saliva which changes 
starch to sugar. 
Pulse (Lat. pulsus, beating): the beating of the blood vessels near 
the surface, as at the wrist. 
Pupa (Lat. pupa, puppet): the quiescent, inactive stage in the de- 
velopment of an insect between larva and adult. 
Pupil of the eye : the round opening in the iris which admits light 
into the eye. 
Pylor'us (Gk. pylorbs, gate-keeper): the opening between the 
stomach and the intestine. 
Q 
Quar'antine : the enforced isolation of persons or places infected 
with contagious diseases. 
Quarter-sawn timber : that which is sawed lengthwise into quar- 
ters to show the medullary (wood) rays obliquely, especially quartered oak. 696 
GLOSSARY 
Queen bee : the mother of a community of bees whose only duty is 
to lay eggs in cells prepared by the workers; a perfect female bee. 
R 
Raceme' (Lat. racemus, cluster): a form of inflorescence in which 
the flowers are arranged spirally around a central axis, as lily-of-the- 
valley. 
Ra'phe (Gk. raphe, a seam or suture): the band running lengthwise 
around the outside of a bean seed. 
Rapto'res (Lat. rapere, to ravish): an order of birds having sharp, 
hooked beaks and strong, sharp talons; birds of prey. 
Ray flowers: the outer flowers of certain composite "flowers," 
for example, common daisy, with white ray flowers, sunflower, with 
yellow ones. 
Recep'tacle (Lat. re, back, + capio, take): the expanded end of a 
modified branch on which the floral parts are arranged. 
Reces'sive (Lat. re, back, + cedo, yield) characters : those which 
do not appear in a hybrid, owing to the dominance of other characters. 
Re'clamation (Lat. re, again, + clamo, call): the act of bring- 
ing wild or arid land to use in raising crops; supplying water for 
irrigation. 
Rec'tum (Lat. rectus, straight): the terminal portion of the alimen- 
tary canal. 
Red rust: a parasitic fungus which has two hosts, wheat and bar- 
berry, during its life history; called also black rust from its mature 
stage on wheat. 
Re'flex (Lat. re, back, + flecto, bend) action : that which takes 
place in voluntary muscles without the intervention of the mind, the 
stimulus going first to the spinal cord and being switched to the motor 
nerves, causing movement. 
Re'foresta'tion : the act of replanting areas with trees, or setting 
out trees on new areas. 
Re'genera'tion (Lat. re, again, + genera, beget): the act of restoring 
a lost part by growing a new one, as the tentacle of a hydra, or the end 
of an earthworm. 
Regular flower : one which has all its petals, also its sepals, the 
same size and shape, as rose, buttercup. Pansies, violets, and salvia 
have irregular flowers. 
Repel'lent (Lat. re, back, + pello, drive): a substance which makes 
plants distasteful to their insect enemies. 
Reproduc'tion (Lat. re, again, + pro, before, + duco, lead): the act 
of bringing forth another thing of the same kind; generation. GLOSSARY 
697 
Respira'tion (Lat. re, again, + spiro, breathe): the life function 
which consists of getting and using oxygen for oxidizing protoplasm to 
release energy, and removing the carbon dioxide resulting from oxida- 
tion. 
Ret'ina (Lat. rete, net): the inmost layer of the coat of the eyeball 
which receives the stimuli of light rays and conducts them to the brain 
through the optic nerve. 
Rhi'zome (Gk. rhiza, root): a thickened, underground stem used for 
food storage, as in Solomon's seal and pteris, or for propagation, as in 
quack grass and Canada thistle. 
Roden'tia (Lat. rodo, gnaw): a group of animals having chisel-edged 
incisor teeth for gnawing, as squirrel, rat. 
Root cap : the loose protective cells covering the end of a rootlet. 
Root hairs : elongated projections of epidermal cells of roots for 
absorption. 
Root pressure : the osmotic force which causes sap to rise in stems. 
Rosette' (Lat. dim. of rosa, rose): the spiral arrangement of leaves 
on a very short axis, as shepherd's purse or bull thistle in early spring. 
Ru'minant (Lat. rumen, throat): an animal which chews its cud, as 
cow. The food is swallowed with very little chewing while eating. 
Later it is returned to the mouth partially digested and is thoroughly 
chewed. 
Rust : a form of plant disease caused by certain fungi; especially red 
rust (black rust) of wheat. 
S 
Sali'va (Lat. saliva, spittle): the natural moisture in the mouth 
secreted by the salivary glands. 
Sama'ra (Lat. samara, elmseed): an indehiscent winged fruit, as in 
maple, elm, and ash. 
Sanc'tuary (Lat. sanctio, make holy): a place of refuge from violence, 
particularly designated localities where birds or other animals may not 
be molested. 
Sanitation (Lat. sanitas, from samus, whole): the devising and 
applying of measures for preserving and promoting health, especially 
public health. 
San Jose scale : an injurious insect which infests fruit trees. 
Sap : the liquids which circulate in plants. 
Sap'rophyte (Gk. sapros, rotten, + phyton, plant): the group of 
fungi which live on dead organic matter. 
Scap'ula (Lat. scapulae, shoulder-blades): one of the shoulder- 
blades. . , . . . 698 
GLOSSARY 
Sci'on (Lat. seco, cut): the small branch inserted into the large plant 
(stock) in grafting. 
Sclerot'ic (Gk. skleros, hard) coat : the tough outer coat of the eye- 
ball. 
Scute (Lat. scutum, scale): one of the large scales on the abdomen of 
a snake. 
Scutel'lum (Lat. dim. of scutum, shield): the shield-shaped cotyle- 
don lying under the embryo in corn and other grains. 
Secre'tion (Lat. sc, aside, + cerno, separate): a substance separated 
or elaborated from blood or sap; the act of forming such a substance. 
Seedling : a young plant during the period when it is dependent 
on food stored in the seed. 
Seg'ment (Lat. segmentum, from seco, cut): one of the ring-like divi- 
sions of the abdomen of insects, and of earthworm. 
Self-pollination : the act of getting pollen on the pistil of any flower 
from its own stamens. 
Sensa'tion (Lat. sensatus, from sentio, feel): the consciousness 
(awareness) of a stimulus received through a sense organ. 
Sen'sory (Lat. sentio, feel) nerves : those which convey stimuli to 
the brain, producing sensation. 
Sex'ual (Lat. sexus, sex) reproduction : that in which the new 
individual arises from the union of an egg and a sperm. 
Sieve cells : large cells with perforated ends which are a part of the 
phloem of a fibrovascular bundle. 
Simple eye : a single organ of sight found in insects, resembling one 
of the numerous parts of the compound eyes. 
Sinus (Lat. sinus, bend): a hollow or cavity in a bone; an irregular, 
widened space in a vessel or among the cells of a tissue. 
Si'phon (Gk. sipho, siphon): one of the openings in the mantle of a 
clam through which water flows in or out. 
Siphun'cula'ta (Gk. dim. of sipho, siphon): an order of insects 
which have sucking mouths, as sucking lice. 
Skel'eton (Gk. skeleton, dried body): the firm part of an animal's 
body to which the muscles are attached. 
Skin : the outer covering of an animal's body. 
Soil (Lat. solum, bottom): the finely divided particles of rock, 
humus, etc., which make up the outer layers of the earth not covered 
by water. 
Sol'id (Lat. solidus, dense): a form of matter neither gaseous or 
liquid, as wood, stone, clay. 
Sol'itary (Lat. solitarius, solitary): single; alone; especially a 
flower which grows at the end of its own stalk. GLOSSARY 
699 
Sol'vent (Lat. solvo, set free): a fluid which makes other substances 
fluid also. 
Spawn : to deposit eggs or roe for reproduction, as fishes. 
Spec'ial senses : seeing, hearing, smelling, tasting, feeling. 
Sperm (Gk. sperma, from speiro, sow): the male element in sexual 
reproduction. 
Sperm'ary (Gk. sperma, from speiro, sow): the organ which pro- 
duces sperms; the testis. 
Spic'ule (Lat. spiculum, dim. of spicum, point, spike): a small, 
hard, pointed body found in sponges. 
Spinal nerves : those arising from the spinal cord, a pair from each 
vertebra. 
Spir'acle (Lat. spiraculum, air-hole): an opening for air in the body 
of an insect or whale. 
Spiril'lum (Gk. speira, coil, wreath): a spiral form of bacterium. 
Spleen (Gk. splen, spleen): a ductless organ lying in the abdominal 
cavity. 
Sporan'gium (Gk. spora, a seed, + angeion, a receptacle): the case 
in which spores are produced. 
Spore (Gk. spora, a seed): a non-sexual reproductive body common 
to fungi, mosses, and other plants. 
Sprain : the injury resulting from a violent twisting or pulling of 
the ligaments. 
Spur : a short, stiff, sharp spine, as on a rooster's leg. 
Spu'tum (Lat. sputus, from spuo, spit): expectorated matter charac- 
teristic of certain diseases. 
Sta'men (Lat. sto, stand): the organ in a flower which produces 
pollen. 
Starch : a substance composed of carbon, hydrogen, and oxygen, 
hydrogen and oxygen occurring in the same proportion as in water; 
a carbohydrate. 
Steapsin : a digestive ferment found in the pancreatic juice and 
assisting in the digestion of fats. 
Stegomy'ia : the species of mosquito which is the host of the malarial 
parasite during one phase of its life history, transmitting it to man by 
its bite. 
Ster'ile (Lat. sterilis, barren): free from bacteria of every kind. 
Ster'num (Gk. sternon, breast): the breast bone. 
Stig'ma (Gk. stigma from stizo, prick): the part of a pistil which re- 
ceives the pollen. 
Stim'ulant (Lat. stimulus, goad): any agent that excites to organic 
action. 700 
GLOSSARY 
Stim'ulus (Lat. stimulus, goad): that which causes a reaction in 
nerve, muscle, or vegetable tissue, as light, sound, electricity, warmth, etc. 
Sting : an organ of offense or defense in animals, as bees, wasps, etc.; 
hollow hairs of plants filled with acrid liquid secreted by the plant, as 
nettle. 
Stip'ule (Lat. stipula, stalk): one of the two leaf-like growths at 
the base of the petioles of certain leaves, as clover, strawberry. 
Stock : the large stem on to which a smaller one (scion) is grafted. 
Sto'lon (Lat. stolo, twig): a thread-like, leafless branch which has 
a vegetative bud on the end, as in strawberry. 
Sto'ma (Gk. stoma, mouth): one of the very small openings in the 
epidermis of a leaf through which water vapor passes out and air in. 
Stom'ach (Gk. stomachos, from stoma, mouth): the sac or enlarged 
portion of the digestive tract in which digestion is carried on. 
Strap-shaped flower : one in which the narrow petals are united 
and turned in the same direction, as in dandelion. 
Style (Gk. stylos, pillar): the slender portion of a pistil connecting 
the stigma and the ovary. 
Sucto'ria (Lat. suctus, from sugo, suck): an order of insects which 
have sucking mouths, as fleas. 
Suf'focate (Lat. suffocatus, from suffoco, choke): to kill by exclud- 
ing air from the lungs or by substituting some other gas for air, as smoke. 
Sug'ar: a carbohydrate of sweetish taste, soluble in water. (See 
starch.') 
Sul'phur : one of the elements found in protein. It forms a combi- 
nation with hydrogen in decomposing protein which is ill-smelling. 
Su'ture (Lat. sutura, from suo, sew): the joining of two bones by 
mutually serrated edges, forming an immovable articulation, as in the 
bones of the skull. 
Swarm'ing : the departure from the hive of a queen bee and most of 
the workers. 
Swimmerets' : small appendages on the abdomen of a crayfish, 
useful in swimming. 
Symbio'sis (Gk. syn, together, + bios, life): the close relationship 
of two organisms which results in mutual benefit. 
Sys'tem (Gk. syn, together, + histemi, stand): a group of organs 
which work together to perform a life function, as digestive system, 
circulatory system. 
T 
Tachi'na-fly : a useful dipterous insect which lays its eggs on the 
larvae of potato beetles. GLOSSARY 
701 
Tad'pole : the larval stage of frogs and toads. 
Tal'on (Lat. talus, heel): a claw, especially of a bird of prey. 
Tar'sus (Gk. tarsos, any flat surface): the ankle; the scaly part of 
a bird's leg; the terminal segment of an insect's foot. 
Ten'don (Lat. tendo, stretch): the connective tissue ending of a 
muscle which attaches it to other structures. 
Ten'dril : an organ of certain plants which clasps a support, enabling 
it to climb. 
Ten'tacle (Lat. tento, touch, try): a jointed flexible appendage on 
the head of insects and other invertebrates, used for touch, grasping, 
or motion; a feeler. 
Ter'minal (Lat. terminus, boundary) bud : one which appears at 
the end of a branch or stem. 
Ter'rapin : one of the tortoises or land turtles. 
Tes'ta (Lat. testa, shell): the hard outer covering of a seed. 
Tes'tis (Lat. testis, a testicle): an organ in a male animal where 
sperms are produced. 
Thales'sa: a useful ichneumon fly which destroys the larvae of 
Tremex, a wood borer. 
Thorac'ic (Gk. thorax, thorax) cavity: the second part of an 
insect's body; in mammals, the cavity above the diaphragm; the chest 
cavity. 
Thy'roid (Gk. thyreos, large shield) gland: a large ductless gland 
on the outside of the trachea below the larynx. 
Thysanu'ra (Gk. thysanos, fringe, + oura, tail): an order of insects 
having bristles on the end of the abdomen, as in fish-moths. 
Tib'ia: the shin bone in man; the fourth division of an insect's 
leg. 
Tis'sue (Lat. texo, weave): a collection of similar cells that per- 
form the same function. 
Ton'sil (Lat. tonsilla, tonsil): one of two ductless glands lying in 
the throat back of the tongue. 
Tox'in (Lat. toxicum, poison): a poisonous substance given off by 
disease-producing bacteria. 
Tra'chea (Gk. tracheia, windpipe): the air passage leading from the 
pharynx to the lungs; an air tube in insects. 
Transpira'tion (Lat. trans, through, 4- spiro, breathe): the evap- 
oration of water through the stomata of leaves. 
Tree surgery: the scientific treatment of diseased trees, consist- 
ing of pruning, filling cavities, and so on. 
Trichinel'la (Gk. thrix, hair): a small round worm sometimes found 
in pork living as a parasite, and the cause of trichinosis in man. 702 
GLOSSARY 
Tri'chocysts (Gk. thrix, hair, + kystis, bag): minute, dart-like or- 
gans of offense and defense found in paramecium. 
Trichop'tera (Gk. trichos, gen. of thrix, hair, + pteron, wings): a 
group of insects having long, hair-like projections from the end of the 
abdomen. 
Tro'chanter (Gk. trochanter, from trecho, run): the second joint 
of an insect's leg. 
Trunk : the stem of a tree; the main part of the body of a verte- 
brate to which the appendages are attached. 
Tryp'sin (Gk. tripsis, a rubbing): a digestive ferment, found in 
pancreatic juice and acting on protein substances. 
Tu'ber (Lat. tuber, a swelling): a short, thick underground stem 
used for storage, as potato. 
Tur'gid (Lat. turgeo, swell): distended with air or liquid; 
swollen. 
Tympan'ic (Gk. tympanon, drum) membrane : the thin partition 
which separates the middle ear from the outer, commonly known as the 
ear-drum. 
u 
Ungula'ta (Lat. unguis, nail): a group of mammals characterized 
by hoofs. 
U'rea (Lat. urina, urine): the nitrogenous waste of animals which 
is passed off in the urine. 
Ure'ter (Gk. oureter, from our on, urine): a tube, one of two, leading 
from the kidneys to the bladder and carrying off the nitrogenous waste 
in the urine. 
U'rino-gen'itals (Lat. urina, urine, + genitalis, from gigno, beget): 
the organs common to the urinary and the reproductive systems, or 
the combination of these systems. 
U'ropod (Gk. oura, tail, 4- pod, from pous, foot): the modified swim- 
meret on either side of the last segment of a crayfish. These, together 
with the telson (the modified last segment) make up an appendage use- 
ful in swimming backwards. 
V 
Vaccina'tion (Lat. vacca, cow): inoculation with the virus of cow- 
pox as a preventive of smallpox. The term is loosely used to denote 
inoculation for other diseases. 
Vaccine' (Lat. vacca, a cow): the virus of cowpox prepared for or 
introduced by vaccination. 
Vac'uole (Lat. vacuus, empty): a space in the protoplasm of a cell GLOSSARY 
703 
usually filled with a clear liquid secreted by the cell, or by food in the 
process of digestion. 
Valve (Lat. valva, leaf of a door): one or more folds in the lining 
tissue of a blood vessel or other organ to prevent or check the flow of 
a liquid in the opposite direction. 
Variation (Lat. varius, various): deviation from the type in struc- 
ture or function. 
Vas'cular (same as fibrovascular) bundles (Lat. vasculum, a little 
vessel): elongated cells which communicate with each other, forming 
tube-like vessels for the transportation of liquids in plants. 
Vein: (Lat. vena, blood vessel): one of the vessels which conducts 
blood towards the heart; one of the ribs of an insect's wing; one of the 
larger supporting and conducting vessels in a leaf. 
Vel'amen (Lat. velare, to veil): a pendant air root of certain orchids 
adapted to gather and store moisture. 
Ven'tral (Lat. venter, belly): pertaining to or situated on the ab- 
dominal side of the body. 
Ven'tricle (Lat. ventriculus, a little belly): any cavity of a hollow 
organ, especially one of the lower chambers of the heart. 
Vermi'form (Lat. vermis, worm, + forma, form) appen'dix (Lat. ad, 
its, + pendo, hang): a slender tubular pouch of the large intestine near 
its juncture with the small intestine. 
Ver'tebrates (Lat. verto, turn): the group of animals which have 
backbones. 
Viabil'ity (Lat. vivo, live): having life or the ability to live, as 
a seed. 
Villi (Lat. villus, a hair): the minute projections which cover the 
lining of the small intestine; an organ of absorption. 
Vi'rus (Lat. virus, poison): the element or principle that is the agent 
or medium for communicating infection. 
Vis'cera (Lat. viscus, an organ of a cavity of the body): the organs 
of the abdominal cavity. 
Vi'tamin (Lat. vita, life): certain substances in foods which are 
necessary for the proper functioning of the vital processes. 
Vitreous (Lat. vitrum, glass): the liquid which fills the posterior 
chamber of the eyeball. 
Vivip'arous (Lat. vivo, live, + pario, bear): producing young alive, 
as cat, man. 
Voluntary (Lat. voluntas, will) muscles : those under the control 
of the will, as the hand. 
Volvox: a colonial organism in which the individual cells show the 
division of labor. 704 
GLOSSARY 
Warm-blooded: having a constant temperature, as man. 
Warning coloration: marks or colors which make an insect or 
other animal conspicuous to its enemies. 
Weed : a plant that grows where it is not wanted. 
Wig'gler : the larva of mosquitoes. 
Workers: underdeveloped females in a community of bees which 
perform all the work of the hive except reproduction. 
Worm : a group of animals having flat or cylindrical bodies which 
in some cases are composed of segments. 
X 
Xy'lem (Gk. xylon, wood): the thick-walled cells in a fibrovascular 
bundle. 
Y 
Yeast: a unicellular fungus which causes fermentation. 
Yolk : the yellow portion of an egg; the food material used by the 
embryo. 
Z 
Zy'mase (Gk. zyme, a ferment): the ferment. INDEX 
References are to pages 
A 
Abdomen, of crayfish .... 109 
of grasshopper 53 
of man 261 
Abdominal cavity 261 
Abnormal growth of tissue 
cause of disease .... 404 
Absorption, a life process . . 15 
of food in man 342 
of food not nourishment . . 345 
of nutrition 17, 333 
Accessory parts of flower . . 497 
Acid medium in stomach . . 338 
Acid soil 586 
Aconite, a poison 319 
Acquired immunity .... 418 
Action of voluntary muscle . . 273 
Active bacteria reduced in 
number by heating milk . 396 
Activities of insects .... 50 
Adam's apple 286 
Adaptation, discussed ... 18, 19 
in appendages of crayfish. . 112 
Adaptations, for pollination . . 512 
of birds 193 
of excretory organs .... 367 
of fruits and seeds for dis- 
persal 522 
of fruits to distribution by 
, water 523 
of honey-bee 104 
of individuals, use of . . . 21 
of a leaf 454 
of mammals for protection . 213 
of man 257 
of reptiles 168 
of the seed 532 
of the skeleton 286 
of wood . 482 
Addison's bronze disease . . 360 
Adenoids . 295 
Adrenal glands 360 
Adulteration, of cereals . . . 318 
of foods 317 
of milk 318 
Adventitious roots 489 
Aerial roots 490 
Afferent fibers 374 
Agar-agar, formula .... 392 
Age of trees, how told . . . 473 
Agencies of seed distribution . 522 
Aggressive coloration .... 90 
Agriculture, amount and kind 
of cultivation in . . 587, 592 
education for 526 
as an industry 526 
Air, home of bacteria . . . . 391 
Air cells of lung 286 
Air currents 292 
Air sac 286 
Akene 517 
Albumen, example of protein . 299 
Alcohol, ambition destroyed by 322 
a narcotic 321 
and disease 330 
and patent medicines . . . 330 
a poison 321, 404 
cause of disease 322 
chemical composition of . . 299 
effect of, on circulation . . 359 
effect of, on digestion . . . 346 
effect of, on nervous system . 322 
formed by yeast plant. . . 317 
in bread driven off by heat . 317 
not a food 299 
Protozoa and 252 
shortens life 321 
use of, in consumption . . . 410 
Alcoholism a disease .... 379 
1 2 
INDEX 
Alfalfa, root system of . . . 490 
Alimentary canal, of frog . . 144 
of man 333 
Alkaline medium in mouth . . 338 
Alkaline soil 586 
Alligators, described .... 168 
example of reptiles . . . . 163 
Alternate leaves, of elm . . . 445 
Altricial birds, defined . . . 173 
American elm 557 
American grape, immunity of . 654 
American Medical Association 329 
Ammonia in test for protein . 537 
Ammonium tartrate in Pasteur 
solution 573 
Amoeba, described 244 
discussed 243 
respiration of 245 
Amount of sleep required . . 376 
Amphibians, described . . . 141 
economic importance of . . 159 
examples of 141 
laboratory study of ... 149 
summary of 160 
Amphioxus, notochord of . . 124 
Amylopsin, a ferment.... 339 
Anesthetic, defined .... 319 
dissolves lipoid 321 
Animal parasites, habits of . . 416 
Animal preserves, purpose . 182, 217 
Animal starch, in liver . . . 343 
" Animals " 208 
Animals, agents in distribution 
of seeds 523 
Animals as friends and enemies 
of other animals and man 605 
decomposed by bacteria . . 391 
without a backbone . . . 124 
Annelida, a class of worms . . 415 
Annual rings, age of tree told by 473 
in longitudinal sections of 
trunks 291 
in stem of pine 342 
Anopheles, mosquito .... 83 
cause of malaria . . . 83,411 
Ant-bear, examples of toothless 
mammal 208 
Ant-eater, example of toothless 
mammal 208 
Antennae, of grasshopper, organ 
of smell 52 
of crayfish 112 
References are to pages 
Anterior metatarsal arch . . 280 
Anther, described 497 
Anti-pain medicines .... 507 
Antiquity of man 256 
Antiseptic 393, 423, 642 
Antitoxin, discussed .... 421 
use in diphtheria .... 422 
Anti-tuberculosis campaign . . 634 
Ants, example of Hymenoptera 65 
life history of 106 
social life of 105 
Anus, in digestive system of 
man 336 
Aorta, largest artery in man . 355 
Ape, a primate 209 
Aphid, example of Homoptera . 65 
Appendages, of grasshopper . . 54 
of crayfish 110 
Appendicitis 336 
Appendix, vermiform .... 336 
Apple wood, use of .... 568 
Apples, a form of fruit . . . 521 
example of pome .... 521 
Applications of biology to the 
human body 255 
Aqueous humor 381 
Arachnids, a group of crusta- 
ceans 119 
list of 119 
Arbutus, destruction of . . . 518 
Arch, of foot 280 
of hypocotyl of bean . . . 533 
supports 282 
Area of forests 554 
Arms, example of organ ... 45 
Army worm, harmful insect. . 176 
Arsenic, a poison 404 
Arteries, function of ... . 353 
of crayfish 115 
of fishes 132 
of man 353 
Arthropods, word explained . 109 
Articulation of bones . . . . 270 
Artificial pollination .... 509 
Artificial respiration (breath- 
ing) 290 
Aseptic surgery 642 
Asexual reproduction, of hydra 619 
of sponge 617 
Ash, result of chemical change. 30 
Ash tree, for shade .... 558 
Ash wood, use of 565 References are to pages 
INDEX 
3 
Asparagus fern, a leafless plant 478 
beetles 67 
Assimilation, a life process . . 15 
in man 357 
in plants 17, 460 
of nutrition 17 
Astigmatism 383 
Atmosphere, composition of 26, 27 
Attitude of early settlers 
towards forests .... 546 
Auditory organ of grasshopper . 55 
Auricles of heart 353 
Autumn colors of leaves . . . 449 
B 
Bacilli coli, tests for .... 625 
Bacillus, a form of bacteria . . 389 
Bacillus tuberculosis, cause of 
consumption 408 
Bacteria, cause of sour bread . 317 
cause of sour milk .... 396 
conditions necessary for 
growth 390 
control of 392 
dairy 393 
decomposition of materials 
by 390 
discussed 389 
effect of enzymes and . . . 391 
forms of 389 
harm to teeth from .... 340 
harmful 389 
helpful 391 
important plants . . . . 391 
in formation of soil .... 393 
injury caused to plant by. . 599 
inoculation of soil with . . 394 
in relation to milk .... 395 
in roots of leguminous plants 394 
in warm milk 398 
laboratory study of. . . . 392 
life processes of 390 
multiplication of .... 391 
presence, in polluted water . 629 
prevention of growth of . . 396 
proper conditions for growth 
of 390 
reproduction of 391 
shape and size 389 
soil bacteria 393 
source of disease . . , , 406 
Bacteria, continued 
summary of 402 
unfavorable conditions with- 
stood by 391 
where found 390 
Bacterial poison, toxin . . . 391 
Bailer in gill chambers of cray- 
fish 115 
Balanced aquarium .... 603 
terrarium 604 
Balanced diet 306 
Balancing, use of fins for . . 128 
Balancing organ, of crayfish . 112 
ear a 384 
Ball and socket joint .... 270 
Balsam, adventitious roots on . 476 
Balsams, conifers 557 
Balsa wood 565 
Baltimore oriole 185 
Bananas, value of, as food . . 527 
Barberry, host of black stem 
rust 581 
Bark of hemlock, use of . . . 562 
Barley, a cereal 526 
Barnacles, crustaceans . . . 119 
Barn swallow 189 
Bass, a bony fish 126 
Basswood, characteristics of . 568 
Bast fibers 482 
Bat, enemy of mosquito . . . 223 
sense organs of 222 
Bayne-Blauvelt Law .... 180 
Beaks of birds, variations in . 194 
Bean, embryo, growth of . . 533 
example of dicotyledons . . 535 
foodstuffs in 536 
from ovulet to seed . . . 531 
fruit of 534 
germination of 533 
seed, laboratory study of . . 536 
seed, relation to flower . . 534 
seedling, parts of .... 533 
source of protein .... 537 
Bean (pulse) family, members 
of 462, 541 
Bear, example of carnivorous 
animal 208 
" Beast " . . 208 
Beaver 228 
example of rodent . . . . 210 
protected in New York State 217 
Bee farms, escape of bees from 102 4 
INDEX 
Bees, classes of 99 
classified insects 65 
community life of ... . 99 
complete metamorphosis of . 99 
drone 99 
gathering of nectar and pollen 
by 5, 514 
honey, value of 104 
imperfect female (worker) . 99 
life history of 99 
members of Hymenoptera . 65 
nurses 99 
perfect female (queen) . . 99 
" robber bees " 100 
sanitary measures of ... 100 
sting of 100 
swarming 101 
wax, value of 104 
Beet, biennial plant .... 489 
source of sugar 494 
storage of food in ... . 494 
Beetle, May, a harmful insect . 68 
potato, a harmful insect . . 68 
Beetles 68 
bird enemies of 68 
discussed 67 
Belly of muscle 275 
Berkshire pigs 234 
Berry, a form of fruit.... 527 
Biceps muscle 273 
Bichloride of mercury, use of . 423 
Biennial roots 489 
Bile, a digestive juice .... 339 
Binding effect of roots . . . 545 
Biological diseases, kinds . 404, 406 
Biological problems involved in 
the production of food 586-599 
Biological survey 645 
Biological terms defined ... 15 
Biology and human progress 649, 665 
Biology, defined .... 1, 13 
progress of 655 
Birds, beneficial, list of . . . 176 
characteristics of . . . . 171 
classified ....... 171 
destroyers of grasshoppers . 60 
economic importance of . . 176 
number of . . . . . . . 183 
protection of 179-181 
recognition of common birds 183 
summary of 172 
Bird's-eye maple 568 
References are to pages 
Bird's feet, different kinds of . 194 
Bitter, a fundamental taste . . 334 
Blackbirds, food of . . . 98, 176 
Black raspberries, rooting of . 480 
Black rot 654 
Black stem rust .... 575, 580 
Bladder in man . . . . . . 364 
Blade of leaf, food storage in . 445 
Blanching of celery .... 461 
Blattoidea, order of insects . . 65 
Bleeding in plants . . . 475, 477 
Blood 349 
corpuscles 349 
heat 351 
of man 349 
plasma 349 
pressure in man 354 
supply of muscle .... 275 
vessels, function of .... 353 
Blossom, first step in produc- 
tion of fruit 5 
parts of 5 
Bluebird, a beneficial bird . , 183 
destroyer of Lepidoptera . . 98 
food of 183 
Blue crab, an edible crustacean 119 
Blue jay, feeds on larvae of 
Lepidoptera 98 
Blubber of whale 215 
Boa-constrictor 165 
Boards of Health 431 
Bobolink, migratory habits of . 197 
Body, parts of, in fish .... 126 
Body regions of grasshopper . 53 
use of each ...... 53 
Body temperature, of birds . . 195 
of mammals 207 
of man 366 
Bone ache 410 
Bone, cells of 268 
structure of 271 
Bones, broken 270 
Boneset, medicinal plant . . 463 
Bony fishes, examples of . . 126 
Borax, a preservative . . . . 396 
in cosmetics . . . . . . 328 
Borers, insect enemies of tree . 4 
eaten by downy woodpecker 68 
Boric acid, a preservative . . 396 
Botany, meaning of .... 436 
Botfly, harmful insect . . . 82 
Boxwood, use of . . . . . 565 INDEX 
5 
Bracket fungi, effect on trees . 575 
Brain, efficiency, discussion of . 376 
efficiency, conditions neces- 
sary for ....... 376 
Brain case . . 261 
" Brain " of earthworm . . . 606 
Braincase of frog 147 
Bran, used as an adulterant . 318 
Branch, of pine, position of . . 560 
Brazil nut, a seed . . . . . 527 
Bread, crumbs for feeding station 201 
mold 574 
mold, laboratory study of . 575 
use of .yeast in making . . 317 
Bread-making, scientific basis 
of 316 
Breast bone of birds .... 195 
Breathing center in developing 
embryo 378 
in grasshopper 53 
in man . 287 
not respiration 16 
Breeding habits of fresh- 
water clams 121 
Broken bones 270 
Bromide of potassium . . . 327 
Bronchitis 295 
Bronchus 286 
Bronze disease 360 
Brook trout raised in hatcheries 139 
Brown creeper, at suet station 202 
food of 98 
Brown rat, a pest 221 
Browntail moths 94 
Bruises, treatment of . . . . 425 
Bubbles of oxygen in masses of 
spirogyra 306 
Bubonic plague, a bacterial 
disease 75 
Bud, in reproduction of yeast 
plant 573 
Budding, man's use of . . 9, 476 
Buds, a characteristic of stems 468 
Bugs, members of Hemiptera 65, 66 
Bulbs 479 
Bullfrog, time required for 
development 152 
Bumble bee, carrier of pollen . 98 
Bunions ........ 282 
Burdock, common weed . . . 489 
distribution of seed by ani- 
mals . . . ... . . 523 
References are to pages 
Bureau of Entomology ... 88 
Bureau of Fisheries .... 138 
Burns, treatment of ... . 425 
Butcher bird (shrike) .... 172 
Butter . . 299, 305, 391, 398, 002 
example of fat 307 
flavor of, due to bacteria . . 391 
value of, as food . . 305, 307 
Butterflies, classified .... 65 
complete metamorphosis of . 94 
Butterfly, swallowtail, from cel- 
ery worm 94 
larvae of 96 
Buzzards, food of 177 
By-product of photosynthesis . 456 
C 
Cabbage yellows, a plant 
disease 575 
Cabbages, food of man . . . 463 
vitamins in 306 
Cactus, length of roots of . . 492 
Caddis flies 65 
Calcium, found in carrots . . 29 
use of, in the body . . . 29, 339 
Calcium phosphate, in Pasteur 
solution 573 
Callouses 282 
Callus in broken bone . . . 271 
Calorie, defined 302 
greater 304 
lesser 304 
needs 303 
Calyx, described 496 
Cambium 471 
Cambium layer in woody stems 471 
Camel, economic importance of 221 
Camomile, flowers of ... . 525 
Canada thistle 479 
Canal, alimentary, of frog . . 146 
of man (digestive tube) . . 333 
Cancer 404 
Cane sugar in Pasteur solution 573 
Canine teeth 339 
Canker worm 94, 176 
Canning 398 
Capillaries, described .... 353 
Capillary circulation . . . . 356 
Capsule, a form of fruit . . . 524 
Carbohydrates, a class of food . 39 
constituents of 39 6 
INDEX 
Carbohydrates, continued 
manufacture of ... . 39, 455 
stored by bean 536 
Carbolic acid, a disinfectant . 423 
a germicide 393 
a poison 319 
Carbon, discussed 26 
Carbon cycle 620 
Carbon dioxide, a gas ... 8 
a waste product of respira- 
tion 16, 460 
formed by yeast plant. . . 572 
product of respiration in 
seeds 539 
taken from the air by 
plants 8, 38, 455 
Carbonic acid gas, discussed . 38 
Cardiac valve of stomach . . 336 
Care of the ears 385 
Care of the eyes 383 
Care of other foods .... 630 
Care of the teeth 340 
Care of trees 555 
Care of young by fish .... 134 
Careless pruning, results of . . 477 
Carnivora, a group of animals . 208 
described 209 
Carp 135 
Carrier of disease 427 
Carrion beetle, beneficial insect 67 
Carrot, example of biennial . . 494 
source of calcium .... 30 
storage of food in ... . 494 
Cartilage 268 
rings in air passages . . . 286 
where found on ribs . . . 266 
Casein, a form of protein . . 28 
made into buttons .... 237 
Castor oil 537, 542 
Cat, a carnivorous animal . . 208 
Catalpa, as ornamental trees . 558 
rapid growth of 538 
Catbird 183 
Caterpillars, destructive insects 71 
larvae of butterflies .... 94 
stage in metamorphosis . . 94 
Catkin-like flowers of poplar . 503 
Catnip, a medicine .... 463, 482 
Cattle, hoofed animals . . . 209 
value of, to man .... 232 
Cauliflower, use of .... 525 
Causes of disease 404 
References are to pages 
Causes of obesity 328 
Caustic soda in Fehling's solu- 
tion 42, 537 
Cavities in the body of man . 261 
Cedar, a conifer 557 
Cedar, leaves of 562 
Cedar of Lebanon, age of . . 468 
Celery, plant blanching of . . 461 
food of man 463 
Cell, described 44 
name given by Hooke ... 45 
growth and division . . . 439 
parts of 438 
unit of structure .... 44 
wall 44, 438 
Cellular structure of living 
things 607 
Centipedes 120 
Central axis of pine cone . . 561 
Central cavity, of bone . . . 271 
Central ideas in biology ... 13 
Central nervous system, of frog 147 
of man 371 
parts of 371 
use of each part . . «n . . 372 
Cere « • • 171 
Cereal foods, source of . . . 526 
Cereal insect investigations . 88 
Cerebellum, of amphibians . . 148 
of child . . 378 
of man ,p . . 371 
Cerebral hemisphere of frog . 148 
Cerebrum of man 371 
Certified milk, defined < . . 397 
Cetacea ? . • 209 
Chameleon, a lizard .... 164 
"Chamois" . . . . . . 234 
Chara, food of crayfish . . . 113 
Character, Mendelian . . . 660 
Characteristics, of birds , . . 171 
of man's skeleton .... 262 
Cheek bones of man .... 265 
Cheese, cottage, vitamins . . 305 
example of protein . . . . 307 
flavor of 397 
indirect product of plants . 526 
Cheese skipper ...... 82 
Chela of crayfish Ill 
Chemical change, defined . . 30 
Chemical compounds .... 25 
Chemicals, used to enrich soil, 
" fertilizers " . . . . . 595 INDEX 
7 
Chemical terms, explanation 
of 24, 27 
Chemical test for carbon dioxide 540 
Chest cavity of man .... 261 
Chickadee 185 
destroyer of eggs and larvae . 185 
Chickweed, viability of . . . 588 
Child Welfare Clinics. . . . 633 
Chimney swifts, feet of . . . 194 
Chinch bug, harmful insect . . 49 
Chipmunk 210 
Chiroptera, a group of animals 209 
Chitin, outer covering of insects 52 
Chloride of lime 393 
Chloroform, example of anes- 
thetic 320 
action on lipoid 321 
Chlorophyll, use in photosyn- 
thesis 38 
Chlorophyll bodies 438 
Chloroplasts, seat of chloro- 
phyll 38, 438 
Cholera 406 
Choroid, coat of eye .... 381 
Cicada, discussed 67 
Cigarette smoking, effect of, on 
eyes 383 
Cilia, in air passage .... 288 
of paramecium 247 
Circulation, a life process . . 15 
effect of alcohol on ... . 359 
in crayfish 115 
in fish 131 
in man 349 
in plants 459 
of nutrition 17 
Civet, a carnivorous animal . 208 
Clam, example of mollusk . . 120 
Clams, fresh water, life history 
of 121 
Clasping base, of grass leaves . 455 
Classes of bees 99 
Classification, basis of, in 
Protozoa 250 
of birds 171 
of fruits 519 
of insects 65 
of seeds 535 
Clavicle 267 
Clay, a kind of soil .... 586 
Clean air 294 
Clean milk 397 
References are to pages 
Clematis, use of petioles in . . 449 
Climbing plants 467 
Climbing stems compared with 
trees 467 
Cloaca of frog 145 
Clothes moths, discussed . . 71 
Clothing, source of . . 63, 481, 603 
Clotting of blood 350 
Clover, affected by darkness . 450 
member of pulse (bean) 
family 462 
Cluster cup stage of black stem 
rust 581 
Coach or carriage horse . . . 231 
Coal, formation of 566 
potential energy in ... . 34 
Coats of pollen grain .... 506 
Cobra, most deadly snake . . 165 
Cocaine, a poison 404 
cause of disease 404 
Coccus, a form of bacteria . . 389 
Cocklebur, adaptations of . . 524 
Cockroaches, family of 
Blattoidea .... 59, 60, 65 
Cocoa 319 
Coconut, a fruit distributed by 
water 523 
Cocoon, of codling moth . . . 7, 70 
Cod, a useful bony fish . . . 126 
Codling moth, a harmful Lepi- 
doptera 7, 70 
complete metamorphosis of . 70 
controlled by spraying . . 71 
discussed 70 
enemy of a tree 6 
life history of 7 
Coffee, a stimulant .... 319 
Cold, a common disease . . . 295 
Cold-blooded animals . . . 132 
Cold storage, purpose of. . . 400 
Coleoptera, examples of . . . 67 
order of insects 65 
Collar of grass leaf .... 455 
Color of fungi, reason for . . 571 
Colors, use of, in flowers... 5 
Communicable diseases . . . 406 
prevention of 430 
Comparison of monocotyledon- 
ous stems with dicoty- 
ledonous .... 469, 473 
of life needs and life functions 
of plants and animals . . 441 8 
INDEX 
Compass plant 450 
Complete flower, definition of . 497 
also perfect 497 
Complete metamorphosis of 
insects 94 
Complexion, light, dark . . . 365 
Composite flowers 505 
Compound eyes, of grasshopper 54 
of crayfish 113 
Compound leaves, defined . . 448 
Compounds, defined .... 25 
Conditions necessary for the 
growth of bacteria . . . 390 
for satisfactory water supply 627 
Conifers, general characteristics 559 
related forms of 562 
and the future 646 
Conservation of biological re- 
sources 643 
of energy 33 
of forests 547 
of land 596 
of matter 34 
of useful mammals .... 217 
of wild flowers . . . . . 516 
Consumption, treatment of . . 409 
Contagious diseases, list of . . 406 
Contractile vacuole of amoeba . 245 
Control of bacteria .... 398 
Cooking 315 
Cooper's hawk, economic status 
of 178 
Copperhead snake 165 
Copper sulphate, in Fehling's 
solution 42 
Cordage 482 
Core, in pome fruits . . . . 521 
Corms 479 
Corn, embryo leaves of . . . 535 
example of monocotyledon . 466 
flower, described . . 509, 510 
indehiscent fruits . . . . 519 
laboratory study of ... 536 
plant, prop roots of ... 491 
planting 589, 590 
" seed," comparison with 
bean 535 
seedling 535 
smut, a fungus 575 
stem 473 
Cornea of eye ...... 380 
Corns . . . ... , . . 282 
References are to pages 
Corolla, described 496 
Corpuscles, red and white . 349- 350 
Corrosive sublimate .... 393 
Cortex of root 485 
Cortical layer of kidney . . . 363 
of root 485 
Corymb 504 
Cosmetic preparations . . . 328 
Cottage cheese, vitamins found 
in 305 
Cotton, source of clothing . 63, 603 
Cottony cushion scale ... 80 
Cotyledon, of corn 535 
of bean 531 
of bean, importance of, as food 537 
of bean, storage of food in . 532 
parts of seed 531 
Cow 232 
Cowpox, Jenner and .... 420 
Crabs 108 
common name for crayfish . 109 
economic importance of . . 10 
example of Crustacea . . . 108 
Cranial cavity 261 
Cranium of frog 147 
Crayfish, discussed . . . . 109 
appendages of Ill 
cephalothorax of .... 110 
circulatory system of . . . 115 
digestive system of . . . . 114 
food and food-getting . . . 113 
green glands of 115 
laboratory study of . . . 117 
life history of 115 
molting of 110 
nervous system of . . . . 115 
respiration of 114 
typical crustacean . . . . 109 
Creosote, preservative of woods 566 
Cricket, member of Orthoptera 65 
harmful insect 60 
Crocodiles, example of reptiles 168 
Crop of earthworm .... 606 
Cross-pollination, defined . . 507 
advantage of 508 
Crow 184 
Crown, part of flower .... 498 
Crows, food of . . . . . . 185 
Crustacea . 108 
contrasted with molusks . . 120 
economic importance of . . 117 
exapiples of 108 INDEX 
9 
Crustacea and related forms . 119 
Cryptobranchus, a salamander. 141 
Cuckoos, food of 176 
Culex (mosquito) 83 
Culture, for Protozoa .... 243 
of bacteria 592 
Curd of milk 299 
Cure-alls 326 
Cure of plant disease 578, 580, 583 
Cures of deafness 327 
Cures of epilepsy 326 
Cures of quacks ..... 326 
Curlydock, viability of . . . 588 
Curly maple 568 
Currant " worm," a larva . . 415 
Cuticle of paramecium . . . 247 
Cutin of leaf 457 
Cuts, treatment of . . . . 358, 429 
Cutworms, harmful insect . . 94 
Cyclops, a small crustacean . . 119 
Cypress trees, conifers . . . 562 
Cypris, a small crustacean . . 119 
Cytoplasm, of cells 44 
of nerve cells 322 
of protoplasm 244 
D 
Daddy-long-legs, an arachnid . 119 
Dairy cow, discussed .... 232 
Daisy, a composite flower . . 505 
Dandelion, weed 516 
a composite 505 
Daphnia, a small crustacean . 119 
Darkness, effect of, on clover 
and oxalis 450 
Dead matter simplified by bac- 
teria 391 
Deafness, " cures " 327 
Death caused by insects ... 64 
Deaths among infants . . . 428 
Decay, caused by bacteria . . 398 
Decomposition caused by bac- 
teria 391 
Deer, ungulates 209 
even-toed 210 
Defects in hearing 476 
Definite annual growth . . . 472 
Definitions of common biologi- 
cal terms 15-43 
Dehiscent fruits, defined . . . 519 
forms of . . . .... 519 
References are to pages 
Deliquescent stems .... 469 
Demonstration of oxidation . . 41 
Denuded hills, cause of 
freshets 544-546 
Deodorizers, not disinfectants . 423 
Department of Agriculture of 
United States, inspecting 
meat 426 
investigations concerning cot- 
tony cushion scale ... 80 
Dependence, of fungi . . . 571 
Dermis, defined 366 
Deserts, habitat of plants . . 492 
Development of tadpole . . . 151 
Devices for regulating trans- 
piration ....... 457 
Devil's paint brush, a weed . . 516 
Diaphragm, of man . . 262, 335 
characteristic of mammals . 207 
passage of esophagus 
through 335 
Diastase, an enzyme . . 28, 41, 459 
Dicotyledons, group of plants . 535 
represented by bean, squash, 
etc 535 
seeds of . 227 
Diet 303 
Digestion, a life process ... 15 
completed in intestine . . . 339 
described . . . . , . . .' 333 
effect of alcohol on ... . 346 
in man ........ 338 
in plants 281 
laboratory study of ... 41 
of food in leaf 459 
of food in seed 538 
of frog 144 
of nutrition ...... 17 
Digestive fluids, of man . . . 337 
Digestive organs, of crayfish . 114 
of frog 144 
of man 333 
Digestive system of animals, 
student report on . . . 337 
Diphtheria (germ disease) . . 406 
antitoxin 421 
carriers 427 
disease of respiratory tract . 295 
ten years of, in France . . 422 
treatment of 422 
Diptera (order of insects) . . 65 
described 82 10 
INDEX 
Dirty milk, bacteria in . . 395, 630 
Disc flowers 505 
of composites 505 
Disease, causes of 404 
results of 577, 580 
student report on ... . 583 
summary of 584 
Diseases, carried by lice ... 75 
caused by abnormal growth 
of tissues 404 
caused by bacteria .... 404 
caused by plants or animals . 404 
caused by poisons, list of . . 404 
of plants 575 
of respiratory tract.... 295 
Disinfectants .... 393, 423 
Disinfection 423 
Dispersal of seeds, agencies for 522 
by animals 523 
by pappus and hooks . . . 523 
by water 523 
by wind 522 
necessity for 522 
Disposal of sewage .... 628 
Dividing egg, becoming tadpole 151 
of frog 151 
Division of drugs 505 
Division of labor 612 
in Gonium 613 
in sponge 615 
in volvox 614 
Dodder 450 
Dog 208 
Dogwood, picking of ... . 518 
Domestic fowl, wings of . . . 194 
Dominant characters .... 659 
Dormancy in seeds .... 588 
Dorsal surface of earthworm . 606 
Dough in bread-making . . . 316 
Down on wind-distributed 
seeds 522 
Downy woodpecker, a per- 
manent resident . . . . 187 
food of 188 
Dragon flies, enemies of mos- 
quito 84 
member of Odonata ... 65 
Drills, a method of planting . 589 
Drones (bees) 99 
Dropping of leaves in autumn . 448 
Drowning, a form of suffoca- 
tion 290 
References are to pages 
Drug habits 319 
Drupe, examples of .... 521 
Dry farming 596 
Dry fruits, bean an example of 519 
Drying, protection of bacteria 
from 391 
Dry season, effect of, on annual 
ring 473 
Dry seasons, effect of, on size 
of cells 473 
Ducks, feet of 194 
Ductless glands 359 
Duration of roots ..... 489 
of stems . 468 
E 
Eagle, a scavenger 177 
Ear, organ of sound .... 384 
balancing organ . . . 112, 384 
drum 386 
membrane of frog .... 143 
of fish 132 
of grasshopper 55 
pistillate flower of corn . . 510 
sense organ 384 
wax in 385 
Earliest homes of man . . . 256 
Earthworm, and plant life . . 605 
economic importance of . . 607 
life processes of 606 
ventral surface ..... 606 
Economic importance, of am- 
phibians 159 
of birds 176 
of crustaceans 117 
of earthworms 607 
of flowers and fruits . . . 525 
of forest products .... 567 
of fungi 575 
of leaves . 463 
of mammals 221 
of mollusks 120 
of Protozoa 250 
of plants 457 
of roots 494 
of seeds and seed products . 540 
Economic insects 64 
Economic interest in plants . . 457 
Economic phases of grasshopper 59 
Economy in the purchase of 
foods 301 INDEX 
11 
Ectoderm, of sponge . . . . 616 
of hydra 617 
Ectoplasm of amoeba .... 244 
Edentata, a group of mammals 208 
Edible fats 28 
Edible mollusks, list of . . . 120 
Edible pulp of fruit, factor in 
distribution 523 
Eels, life history of .... 134 
Effect, of drugs and alcohol on 
digestion 346 
on circulation 359 
Effect of coffee on heart . . . 359 
Efferent fibers 374 
Efficiency centers of brain . 378 
Egg, white of, example of pro- 
tein 299 
Egg cell, of frogs 150 
fertilization of, in plants . . 510 
vol vox 614 
Egg nucleus 506-507 
Egg plant, a fruit 527 
Eggs, of frogs 150 
of grasshopper 57 
Elder, use of flowers of . . . 525 
Elements and compounds . . 25 
Elk, protected in N. Y. State . 217 
Elm tree, roots of 557 
found in organisms .... 26 
number and names of . . . 26 
wood, characteristics of . . 531 
Elephant 209 
Embryo 531 
corn, position of 535 
growth of, in ovule .... 532 
heart of human 377 
parts of 533 
sac, contents of 531 
vigorous, result of cross-pol- 
lination 509 
Employment afforded by plant 
industries 526 
Encystment of amoeba . . . 245 
Endoderm, of sponge .... 615 
Endoplasm, of amoeba . . . 244 
Endoskeleton of fish and frog . 109 
Endosperm, food supply of 
corn ........ 535 
of corn grain 535 
of corn, used for growth of 
seedling 539 
Endurance of muscles . . . 277 
References are to pagec. 
Enemies, of frog 153 
of insects 98 
of Lepidoptera 97 
of plant life 599 
Energy, defined 31 
discussed 31 
forms of 31 
uses of, in body 277 
English sparrow, destroys 
weevils 187 
eats larvae of Lepidoptera . 98 
permanent resident. . . . 171 
English walnut, protein in . . 299 
Enlarged base of onions, stor- 
age of food in 479 
Enriching the soil by nitrogen . 594 
Entomologists, work of . . . 81 
Environment, defined .... 158 
discussed 47 
illustrated by development of 
frog 158 
influence on man .... 663 
Enzymes, discussed .... 28 
in pancreatic juice .... 339 
of yeast plant 572 
secreted by bacteria . . . 391 
Ephemeridae, an order of in- 
sects 65 
Epidemic, defined 430 
Epidemics, after wars . . . 429 
of diseases, costliness of . . 428 
prevention of 430 
Epidermal tissue of pteris stem 482 
Epidermis, of root 485 
of leaf 452 
of rootlets 487 
of desert plants 454 
outer layer of skin .... 365 
Epiglottis 285 
Epsom salts in cosmetics . . 328 
Erosion checked by roots . . 545 
Esophagus, of crayfish . . . 114 
of earthworm 606 
of frog 144 
of man 335 
Essential parts of flower. . . 497 
Ether, an anesthetic .... 321 
test for oil 537 
Eugenics, defined 660 
European corn borer .... 76 
control measures .... 78 
discussed 76 12 
INDEX 
Eustachian tube, of frog . . . 143 
of man 335 
Evaporation of perspiration, ef- 
fect of 366 
Evening grosbeak, winter vis- 
itant 172 
Evergreen, leaves defined . . 560 
Evergreen trees, examples of 562 
Evergreens, characteristics of . 557 
Evolution 156 
Excelsior, source of .... 567 
Excretion, a life process ... 15 
definition of 17 
in crayfish 115 
in fish 132 
in frog 146 
in grasshopper 56 
in plants 459 
of hydra 619 
of man 363 
Excretory organs of man . . 363 
Excurrent stem of ever- 
greens 468 
Exercise, benefits of ... . 358 
effect of, on breathing . . . 288 
necessary to keep one fit . . 366 
Exercises to correct flat-foot . 281 
Exercising, out-of-doors . . . 
to keep well 289 
Exhalent pores of sponge . 615 
Exhalent siphon of clam . . . 121 
Exoskeleton, of crayfish . . . 109 
of grasshopper 52 
Experiment, to show digestion 
of starch 341 
production of carbonic acid 
in germinating seeds . . 539 
performed on plants . . . 462 
Expiration, defined .... 287 
Explosion of fruit case to 
scatter seeds ..... 524 
Extent, of original forest . . 546 
of root system 490 
Extensor muscles 275 
External appearance of woody 
stems 468 
External parts of fish .... 126 
Extinct animals, remains of . . 157 
Eye 380 
Eyeball 380 
Eyelid 380 
Eyes, of fish ....... 132 
References are to pages 
Eyes, continued 
of grasshopper 50 
of man 380 
of man, care of 383 
of vertebrates 380 
" Eyes " of potato 480 
F 
Faeces, defined 344 
removal of 344 
Fainting, cause of 358 
Fangs of rattlesnake . . . . 165 
Far-sighted eyes 383 
Fascicled roots 489 
Fatigue of muscles . . . . 276 
Fats, a class of foods . . 28, 298 
absorption of 343 
furnished by animals . . . 299 
nutrients 28 
Fear of snakes 165 
Feathers, a characteristic of 
birds 196 
of birds, modifications of 
skin 366 
Federal and state protection . 554 
Federal Plant Quarantine Act . 637 
Feeblemindedness .... 662 
Feelers, of bullhead .... 132 
of grasshopper 54 
Feet of birds, different kinds 
of 195 
Fehling's solution, formula . . 42 
test for grape sugar ... 42 
Femur, of grasshopper ... 56 
of man 267 
Ferments 41 
Fermentation, cause of . . . 572 
effect of , 572 
produced by enzymes . . . 572 
Fertilization, defined .... 150 
of egg cell in the ovule. . . 509 
Fertilizers, use of, to supply 
elements 594 
Fibers in blood 351 
Fibrinogen, in formation of 
clot 331 
Fibrous roots . . . . . . 486 
Fibrovascular bundles, cells of . 266 
conducting vessels .... 469 
in leaves . . . . . 445, 460 
structure of ...... 471 References are to pages 
INDEX 
13 
Field study, of conifers . . . 363 
of moths and caterpillars . . 73 
Filaments, of gill 131 
of anthers 497 
Finches, beak of 195 
Fins, of fish 126-128 
use of, in balancing and 
steering 128 
Fires, forests destroyed by . . 548 
prevention of, by national 
government 550 
Firs, conifers 562 
Fish, care of young .... 134 
locomotion of 127 
production 313 
spawning habits 134 
substitute for meat . . . 311 
summary of 140 
Fish hatcheries 138 
Fishes, bony 126 
circulation of 131 
classified 126 
food-taking 128 
importance of 126 
movement, how produced . 128 
mucous glands of .... 127 
reproduction of 133 
respiration of 130 
scales of 127 
special senses of 132 
teeth of 128 
with lungs 126 
Fish fry, young 138 
yolk, food for 133 
Fish-killing insects . . . . 129 
Fish-moth, example of Thysa- 
nura 65 
Fission, a form of cell divi- 
sion 246, 440 
Flaccid cells 454, 458 
Flagella 250, 390 
Flagellata, group of Protozoa . 250 
Flat foot 280 
Flat worms, classified .... 415 
Flavor, of butter 391 
Flavors, caused by fermentation 391 
by bacteria 391 
Flax, useless parts of, removed 
by bacteria 391 
Fleas, member of Suctoria . . 65 
Flesh-eating animals .... 208 
Fleshy fruits 519 
Flexor muscles 275 
Flicker, a beneficial bird . . . 189 
at suet station 202 
Flies, carriers of bacteria . . 64 
classified 63 
discussed 82 
Flying animals (Chiroptera) . 209 
Floods, cause of 544 
Flour, food elements in . . . 316 
Flower, defined 496 
Flower bud 469 
Flowering plants 496 
Flowers, home work .... 499 
of lilies 499 
of nasturtium 496 
wind-pollinated 508 
Flycatchers, eaters of larvae . . 98 
food of 98 
Flying wings of grasshopper . 55 
Food, care of 630 
definition of 298 
fungi, a source of ... . 575 
necessary to keep one fit . . 297 
of bacteria 390 
of frogs 143 
of muscles 275 
of snakes 165 
storage 489 
stored in cotyledons of bean 532 
Food and Drugs Act .... 318 
Food-getting, by grasshopper . 52 
Food groups 306-307 
Foods 297 
classes of 298 
use of each class .... 298 
Food shortage 312 
Foodstuffs in bean .... 437 
Food substitutes 311 
Food-taking, a life function . .15 
not true of green plants . . 39 
Food vacuole of amoeba . . 245 
Foot of clam 121 
Forage insect investigation . . 88 
Fore limbs of animals dis- 
cussed 211 
Forest fires 550 
Forests and forest products 544, 567 
rangers, work of 548 
Forest reserves 555 
Forestry and the Department of 
Agriculture 552 
as a vocation 568 14 
References are to pages 
INDEX 
Forestry and the Department 
of Agriculture, continued 
defined 552 
in other countries .... 554 
in New York State .... 554 
Forests, extent of, in U. S. . . 554 
importance of 544 
patrolling 551 
proportion necessary . . . 554 
Formalin, a germicide . . . 393 
in milk 318 
Formation of coal and peat . . 566 
Forms of leaves 449 
of matter discussed .... 25 
Fossils, described 157 
shells of animals now extinct 156 
Foul breath caused by bacteria 340 
Fox, protected in N. Y. State . 217 
Fox sparrows, transients. . . 172 
Fox terrier, comparison of 
primitive horse with . . 231 
Fractures, treatment of . . . 425 
Freezing, protection of bacteria 
from 492 
Fresh air, a condition for health 292 
aid in curing consumption . 409 
Fresh fruits, use in diet . . . 302 
Freshets, cause of 544 
Fresh-water planarians . . . 416 
Frog, bull, development of . . 152 
central nervous system of . 147 
common 142 
description of 142 
eggs 150 
enemies of 153 
example of amphibians . . 141 
food of 143 
food-taking of 143 
green, development of . ... 152 
habitat of 141 
internal organs of • . . . 144 
laboratory study of ... 142 
leopard, description of . . 142 
reproduction of frog . . . 146 
respiration of 143 
Frogs and their way of living . 141 
Fruit, defined 519 
flies 81, 637 
of apple tree 6 
of bean 519 
of pine 561 
of poppy 517 
Fruit, continued 
production in connection with 
storage roots 489 
steps in development of . . 502 
use of, to plant 520 
Fruits, distributed by animals . 523 
by wind ....... 522 
distributers of seeds . . . 522 
effect of cross-pollination on 
seeds 508 
furnish luxuries of food . . 520 
of rose 520 
with hooks 523 
Fruits and seeds 527 
Fry 138 
Fuel, trees, source of . . 482, 567 
Functions of the parts of a 
flower 501 
Functions of the skeleton . . 268 
Functions of fruit 519 
Fundamental functions, dis- 
cussed 15-18 
Fundamental tastes .... 334 
Fungi, as food 575 
conditions favorable for 
growth 571 
discussed 571 
distribution of 571 
summary of 584 
Fungus, an enemy of corn . . 575 
Furniture, lumber for .... 568 
Furs, as clothing 218 
Fusarium conglutinans, cause 
of cabbage yellows . . . 576 
G 
Gall bladder of frog .... 146 
Gall flies, enemies of apple 
tree 2 
Game laws, purpose of . 134, 137 
Ganglia, of grasshopper ... 57 
of sympathetic system . . 372 
Gas, a form of matter ... 25 
use in bread-making . . . 317 
Gastric glands 337 
Gastric juice 338 
Gastric mill, of crayfish . . • 114 
Geese, feet of 194 
wild, transients 172 
General biology, project in . . 13 
state supervision (of health) . 632 References are to pages 
INDEX 
15 
General methods of controlling 
insects 79 
Geranium slip, roots of . . . 489 
Germ, a name for unicellular 
organisms 389 
diseases 405 
Germicide 393 
Germination, laboratory study 
of 538 
Germs 389 
a name for bacteria . . . 389 
getting well 409 
of disease carried by in- 
sects 64, 75 
Gila monster, poisonous lizard . 165 
Gill cover 126 
Gill rakers 130 
Gill scoop, of crayfish . . . 115 
Gill slits . 124 
Gills, of fish 131 
of crayfish Ill 
Ginger root, use of .... 494 
Giraffe 209 
Girdle, pectoral 125 
pelvic 125 
Girdling of trees 477 
Gizzard of earthworm . . . 606 
Glands, defined 337 
Glomerulus of kidney . . . 364 
Glucose 276 
Gluten 28, 316 
Glycerin formed by zymase . 317 
Glycogen, stored in liver . . 276, 343 
Gnawing animals (Rodentia) . 209 
Goats, economic importance 
of 301 
Goiter 360 
Goldfinch 190 
Goldfish, a typical bony fish . 126 
killed by tobacco smoke . . 326 
Gonium 613 
Good food, value of, in cure for 
tuberculosis 409 
Gophers, harmful mammals . 221 
Government inspection, of 
meat 418, 426 
Grafting, effect of 10 
described 10, 476 
Grain 519 
of corn, a form of fruit . . 519 
" Grain " of wood . . . 473, 483 
Grains (cereals) 526 
Grantia, described 615 
Grape sugar, discussed ... 27 
Grass, monocotyledon . . . 445 
wind-pollinated flower. . . 508 
Grasses, adaptations of . . . 455 
importance of, as food . . 463 
Grasshopper, classified . . 59, 65 
classification of 58 
described 50 
laboratory study of ... . 56 
life history of 57 
life processes of 51 
mouth parts of ■ 54 
parts of 53 
typical insect 50 
structure of 58 
Gravel, a kind of soil .... 586 
Gravity, a form of energy . . 31 
influence of, on roots ... 33 
Grayfish, an edible fish . . . 136 
Gray substance of nerves . . 371 
Great northern shrike, winter 
visitant 172 
Green frogs, development of . 152 
Green glands of crayfish . . 115 
Green manuring 394 
Green peas as food .... 542 
Green plant, a food factory . . 37 
Green turtles 164 
Green vegetables as food . . 302 
Gristle, defined 268 
Grosbeaks, beak of .... 194 
Ground birds, wings of . . . 194 
Growth, of bean embryo . . . 533 
of nervous system . . . . 372 
of stems 472 
Grub, enemy of tree .... 4 
Guard cells, of stomata . . . 454 
Guinea pigs 222 
Gullet, of paramecium . . . 248 
Gulls, sailing birds .... 191 
Gums, effect of tartar on . . 340 
Gunpowder, use of willow char- 
coal for 567 
Guttation, defined 458 
Gymnosperms, cone-bearing 
trees 557 
discussed 559 
economic importance of . . 562 
economic value (of forests) . 554 
field study of 563 
in coal beds 566 16 
INDEX 
Gymnosperms, continued 
student report on ... . 563 
Gypsy moths, injurious in- 
sects 82, 94 
H 
Habitat, of evergreens . . . 562 
of frogs 153 
of Protozoa 242 
Habits, as to alcoholic bever- 
ages 321 
of frogs 153 
Haddock, an edible fish . . . 136 
Haemoglobin in corpuscles . . 349 
Hair, origin of 366 
Hair worm 416 
Hard bone 271 
Hard maple as shade tree . . 558 
Hard palate 335 
Hard wood of maple .... 567 
Harmful bacteria . . . 401, 404 
Harmful birds, list of ... . 178 
Harvestman, useful arachnid . 119 
Haustoria, modified roots . . 490 
Hawk, Cooper's, harmful . . 178 
example of Raptores . . . 171 
red-shouldered 176 
red-tailed 176 
sharp-shinned 178 
Hawks, beneficial birds among 176 
foot of 195 
Hay infusion for Protozoa . . 243 
Head, body region 261 
cluster of flowers . . k . 504 
of grasshopper 54 
Head end of earthworm . . . 605 
Heads, inflorescence of com- 
posite family . . . . . 505 
Head-thorax region of crayfish 109 
Health 624, 404 
activities 624 
Healthy bodies and bacteria . 401 
Hearing 384 
Heart, of man 352 
center 377 
muscle cells 273 
of crayfish 115 
rate of heart beat .... 353 
valves of, in man .... 353 
Heart and blood-vessels of 
man 352-353 
References are to pages 
Heat, a form of energy ... 31 
Heat and pressure, influence 
of, in forming coal . . . 566 
Heating, common methods of . 292 
milk, effect on bacteria . . 396 
protection of bacteria from . 392 
Hedgehog 208 
Helpful bacteria 391 
Hemiptera, discussed .... 66 
order of insects 65 
Hemlock, bark, use of . 236, 562 
conifer 562 
Hemorrhage 424, 351 
Herbaceous plants 655 
Heredity, discussed .... 157 
of disease 431 
Hermit crabs 119 
Herons, beak of 194 
Herring, an edible fish . . . 126 
Herring gull 191 
Hibernation, defined .... 154 
Hickory, source of nuts . . . 567 
wood, uses of 568 
Hills, a method of planting . . 589 
Hilum of bean 532 
Hind legs of mammals . . . 211 
Hinge joint 270 
Hinge of clam 120 
Hip girdle ....... 267 
Hippopotamus 210 
Hogs, inspection of .... 418 
Hollow bones of birds . . . 195 
Holly; use of wood of . . . . 568 
Home-making, work of women 315 
Home project, How Insects 
Pass the Winter .... 91 
Home study of mammals . . 238 
Homing instinct in birds . . 201 
Homoptera, an order of insects 65 
Honey, amount of carbohydrate 
in 299, 307 
value of, in U. S 104 
Honey-bee, discussed .... 98 
development 99 
worker, queen, drone ... 98 
Honey-bees clustering at 
swarming time . . . . 101 
Hoofed animals (Ungulates) . 209 
Hoofs of cattle, origin of . . 366 
Hooke, first observer of cell . 241 
Hooks, on fruit of burdock . . 523 
on fruits, use of 523 INDEX 
17 
Hookworm disease .... 418 
Hop lice destroyed by ladybugs 68 
Hormones 360 
Horned toad, a lizard .... 165 
Horns of cattle, origin of . . 366 
Horse, classified 209 
discussed 230 
evolution of 231 
use of 231 
Horse-chestnut, as shade tree . 558 
compound leaves of . . . 448 
Host, defined .... 74, 87 
Hotels, examination of help for 427 
House-fly, discussed .... 84 
House-sparrow (English spar- 
row) 187 
How fertilization is accom- 
plished 510 
How tracts can be reforested . 551 
How the smoker's heart is 
affected 323 
Humane methods, of catching 
fish 139 
of care and protection of 
mammals 216 
Human interests in biology . . 602 
Human progress . . . 649-665 
Humidity 292, 458 
Humerus 266 
Humming birds, beak of . . 195 
summer residents . . . . 172 
Humor, aqueous 381 
vitreous 381 
Humus, a kind of soil .... 586 
formed by leaf decay . . . 544 
Hybrids 659 
Hydra, cell layers in ... . 617 
described 617 
Hydrochloric acid in artificial 
gastric acid 342 
Hydrogen, discussed .... 27 
proportion of, in plants and 
animals 27 
Hygiene of country schools . . 632 
Hygiene of the foot .... 280 
Hygienic habits of breathing . 288 
Hymenoptera (bees) .... 98 
order of insects ..... 65 
Hyphae of bread mold . . . 574 
Hypocotyl, part of embryo . . 531 
part to grow first .... 533 
use of, to embryo .... 533 
References are to pages 
Hypopharynx of grasshop- 
per 54 
I 
Ice, a form of water .... 30 
use of, in caring for milk . . 396 
Ichneumon fly 87 
Imbecility 404 
Immovable joints 270 
Immunity 418 
defined and discussed . . . 418 
Imperfect flowers, of corn . . 508 
Importance, of bathing . . . 366 
of excretion 367 
of exercise 277 
of health 404 
of mastication 341 
of muscles 273 
Importation of certain fruits for- 
bidden 637 
Improving the varieties or 
plants and animals . 314, 651 
Impurities in water and milk . 318 
Incisor teeth 339 
Incomplete flower, part lacking 
in 501 
Incomplete metamorphosis . . 58 
Increasing the food supply . . 313 
Indefinite annual growth . . 472 
Indehiscent fruits, defined . . 519 
Indeterminate inflorescence . 504 
Indian pipe, a leafless plant. . 450 
Indigestion 345 
causes of 345, 405 
disguised by alcohol . . . 346 
tablets for 346 
Indistinct ring, left by bud 
scales 468 
Infection 407 
Inflorescence 503 
Influence of alcohol on brain . 378 
Influenza 410 
Infusoria 250 
Inhalent pores of sponge . . 615 
siphon of clam 121 
Inhalers 323 
Inherited diseases 404 
Inner chamber of eye . . . 381 
Inner coat of pollen grain . . 506 
Inner ear 384 
Inoculation 394 18 
INDEX 
Inorganic foods 29, 299 
Inorganic matter 24 
Insanity 404 
Insect, definition of ... . 26 
pollination 6 
Insecta 58 
Insect control 88-89 
National 88 
State ........ 89 
Insect-eating mammals (Insec- 
tivora) 208 
Insect enemies of forests . . 88 
Insectivora, a group of mam- 
mals 208 
bait for fish 129 
characteristics of ... . 58 
classification of 64 
devices of flowers for attract- 
ing 505 
economic 63 
field study of 51 
food of fish 129 
object in visiting flowers . . 505 
reasons for numbers of . . 62 
Insects, age of 63 
Insertion of muscles .... 273 
Inspection of meat . . . 418, 426 
Inspiration, defined .... 287 
Insulation of nerve fibers . . 321 
Insulin 642 
Integument, of bean (testa) . 531 
of ovules 531 
Intercellular spaces . 357, 358, 451 
Interdependence of living things 602 
Internal, gills .... 151, 152 
organs of frog 144 
lung 143 
Interrelation of living things . 602 
Intestinal glands 337 
Intestine 364 
Invertebrates, group of animals 124 
Inverted image 382 
Involuntary muscles .... 272 
Iodine test for starch .... 40 
Iris of eye 381 
Iron in blood cells 29 
in prunes and spinach ... 30 
Irrigation 592, 596 
Irritability a fundamental func- 
tion 15 
of frogs 147 
Ivy, roots of 489 
References are to pages 
J 
Japanese barberry, immunity 
of 583 
Jaw bones of fish 126 
Jaw of man 265 
Jenner, vaccination .... 420 
Jewel weed, explosive fruit of . 524 
Joints in man 269 
classes of 270 
Junco 195 
at seed station 202 
K 
Kangaroo . 208 
Katydids, a family of Orthop- 
tera 59 
Keel of bird's breastbone . . 195 
Keeled sternum of bird . . . 195 
Keeping milk sweet .... 396 
Keeping well 426 
Kidney, described 363 
Kidneys of frog 146 
Kidneys of man 363 
Kinds of diseases 404 
Kinds of foodstuffs in seeds . 536 
Kinds of land used for for- 
ests 545, 568 
Kinds of mammals .... 208 
Kinds of soil 586 
Kinetic energy defined ... 31 
King bird 176 
food of 176 
Kingfisher, nesting habits of . 172 
Knee cap 267 
Knees of cypress . . . 489, 491 
Koch, discoverer of Bacillus 
tuberculosis 408 
of tuberculosis test . . 397, 400 
study of bacteria by . 400, 408 
L 
Labium 54 
Laboratory experiments with 
leaves .... 453, 461, 462 
Laboratory study, of amphib- 
ians 142 
of apple 521 
appendages of crayfish . . 113 
of bacteria 392 Index 
19 
Laboratory study, continued 
of bean seed 536 
of bread mold 575 
of cells 440 
of course of sap 481 
of corn 536 
of digestion of protein and 
fats 342 
of effect of alcohol and to- 
bacco on paramecia . . . 252 
of fish 127 
of foodstuffs in seeds . . . 537 
of fruits 520 
of germination 536 
of grasshopper 56 
of gymnosperms (cone 
bearers) 564 
of land plants 462 
of leaves 453 
of liberation of gas .... 462 
of liberation of water vapor . 462 
of lily 500 
of live fish 127 
of monarch butterfly ... 96 
of nasturtium 498 
of necessity of starch digestion 344 
of orange 520 
of osmosis 492 
of paramecium . . . 246, 253 
of photosynthesis . 39, 46, 461 
of reptiles 169 
of roots 487, 492 
of skeleton 291 
of stems 478 
of tasting 334 
of tomato 521 
of woody stem 468 
of yeast plant 573 
Labium 54 
Labrum 54 
Lacey law 180 
Lacteals 343 
Lactic acid, effect of ... . 396 
La grippe 411 
Ladybug 67 
larvae of 68 
Ladyslipper 468 
Lake trout raised in hatcheries 139 
Lampreys, a group of fishes . . 126 
Larch, a conifer 562 
Large cells, position of, in an- 
nual ring 560 
References are to pages 
Large intestine 336 
Lark, meadow, nest of . . . 172 
Larvae 68-105 
Larynx of man 286 
voice box 286 
Lateral bud 469 
Layering 476 
Lead, cause of disease . . . 404 
Leaf 444 
general structure and parts 
of 444, 452 
mosaic 447 
scars defined 468 
work of 2 
Leaf-cutting wasps .... 3 
Leafless plants 450 
Leaflets of compound leaf . . 448 
Lean meat, example of protein 299 
Leather 235 
made from skins .... 235 
Leaves, arrangement of . . . 445 
functions of 455 
modified forms of ... . 449 
movement of 451 
of elms 445 
of grass, shape of ... . 455 
of pine, described .... 560 
of pitcher plant 449 
of trees, arrangement of . . 445 
used for food 463 
used for medicine .... 463 
Leech, enemy of frog .... 153 
Leeuwenhoek, improver of mi- 
croscope 46 
Legs and wings of birds . . . 193 
Legumin 28 
Lemur 209 
Lens of eye 381 
Lenticels, described .... 469 
Leopard frog 142 
Lepidoptera, order of insects . 65 
Lice 74 
Life cycle, of bean 534 
of tree 6 
Life functions 15, 609 
Life history, of ant .... 106 
of codling moth 7 
of eel 134 
of frog 150 
of grasshopper 57 
of house-fly 86 
of monarch butterfly ... 94 20 
INDEX 
Life history, continued 
of plant, defined 6 
of potato-beetle 69 
of reptiles 163 
of toad 154 
Life of flowering plants . . . 442 
Life preservers from balsa wood 565 
Life processes, of crayfish . . 113 
of grasshopper 51 
of bacteria 391 
of paramecium 247 
review of 251 
Ligaments 270 
Light, a form of energy ... 31 
influence on plants .... 32 
Lily flower 499 
Limbs of man 261 
Linen, furnished by flax . . . 481 
source of clothing .... 481 
use of bacteria in manufac- 
turing 391 
Linseed oil, source of ... . 542 
Lipoid 320 
Lips of frog 144 
Liquid, a form of matter ... 25 
Liquor license required . . 330 
List of insects in Orthoptera . 59 
List of injurious insects ... 49 
List of subjects studied by 
Bureau of Entomology . . 88 
Liver 145, 337 
Liver flukes 416 
Lizards 164 
horned toad, example of . . 165 
Loam, a kind of soil .... 586 
Lobes, olfactory 147 
Lobster, example of Crustacea 108 
protected by law 118 
Location of nerves in man . . 370 
Lockjaw 421 
Locomotion, of fish .... 127 
of paramecium 247 
Locust, a kind of grasshopper . 59 
Long bones of arm and leg . . 266 
Longitudinal arch of foot . . 280 
Louse, carrier of disease ... 75 
Lumber, from gymnosperms 
(conifers) 562 
how cut 566 
Lumbering, compared with 
forestry 547 
operations, forests destroyed by 547 
References are to pages 
Lungs, of birds 195 
of frog 143 
of man 364 
Luxuries, fleshy fruits . . . 527 
Lymph 357 
Lymphatic circulation.... 358 
Lymphatics 357 
M 
Mackerel, a bony fish . . . 126 
Maggots, larvae of flies . . . 637 
Magnesium sulphate in Pas- 
teur solution 573 
Mahogany, use of, as furniture 
veneer 568 
Malaria 411 
caused by mosquito ... 83 
protozoan disease . . . . 411 
Malarial parasite 411 
Mammals, classified .... 208 
discussed 207 
home studies on 238 
summary of 239 
Mammals valuable for buttons 237 
Mammals valuable for oil . . 237 
Mammals with nails (Primates) 209 
Mammal sanctuaries . - . . 217 
Man and his competitors . . 11 
Man, as an animal .... 255 
example of mammal . . . 209 
Mandibles, of crayfish . . . Ill 
of grasshopper 52 
Mandrake, medicinal plant . . 494 
Maple sirup 567 
trees, products of ... . 567 
Maple wood, use of ... . 568 
Marrow of bone 271 
Marsh island preserve . . . 182 
Martins, mosquitoes eaten by . 84 
Marsupials (pouched animals) . 208 
Massasauge, a rattlesnake . . 165 
Masts 482 
Material for clothing . . 481, 542 
Matter, organic and inorganic . 24 
Maturity, a period of life . . 259 
Maxilla, of grasshopper ... 54 
of crayfish Ill 
Maxillipeds, of crayfish . . . Ill 
May beetle, harmful insect . . 68 
May flies, member of order 
Ephemeridae 65 INDEX 
21 
Meadow lark 172 
Measles, probable cause of . . 407 
Meat, indirect product of plants 298 
lean, use of, as food . . . 299 
Median fins of fish . . 127-128 
Medicinal plants 
463, 482, 494, 525, 541 
Medulla, of frog 148 
of man 371 
Medullary layer of kidney . . 363 
Medullary rays, of woody stem 171 
primary 472 
secondary 472 
Medullary sheath of nerve . . 371 
Men who made the study of 
bacteria possible .... 400 
Menhaden, example of bony 
fish 126 
Mendelian Laws, The .... 658 
Mental attitudes, effect on pos- 
ture 280 
health 662 
Mercury poison 404 
Mesentery of frog 146 
Mesoglea of hydra .... 617 
Mesophyll of leaf 452 
Mesothorax of grasshopper . . 55 
Metal container dangerous for 
milk 398 
Metamorphosis 58 
complete 94 
incomplete 58 
of frog 152 
Metathorax of grasshopper . . 55 
Methods, of attracting birds . 201 
of breeding wheat .... 651 
of control of house-fly ... 86 
of forest protection .... 548 
of planting 589 
Mice, destroyed by hawks . . 176 
harmful mammals .... 210 
Microbes, a name for bacteria . 389 
Micropyle, of bean .... 531 
use of 531 
Microscope, inventor of . . . 46 
Midbrain 148, 371 
Middle ear 384 
Migration of birds 196 
Migratory habits of birds . . 171 
Milk 301 
care of 301 
curd of, example of protein . 299 
References are to -pages 
Milk, continued 
from healthy cow, number of 
bacteria in 395 
indirect product of plants . 299 
products 397 
Milk glands, characteristic of 
mammals 207 
Millipedes 120 
Milt of fish 138 
Mimicry in insects .... 91 
Mineral matter in food . . 29, 298 
Mineral substances, use of . . 29 
Mink, harmful mammal . . . 208 
Mints used for medicine and 
in food 463 
Mites, arachnids 119 
Mixed diet of man .... 299 
Mixed joints 270 
Model reservoir 626 
Modern surgery 641 
Modified cotyledon (scutellum) 
of corn 535 
Moisture, a condition for 
growth of bacteria . . . 390 
Molars of man 340 
Mold 574 
Mole 208 
Moles destroyed by hawks . . 176 
Mollusks, characteristics of . 120 
importance of, to man . . 120 
Molting, of crayfish .... 110 
of grasshopper 57 
Monarch butterfly 94 
Monkey, example of mammal . 209 
Monocotyledons, group of 
flowering plants, 445, 466, 
473, 535 
represented by corn . . . 535 
Monocotyledonous stems . . 473 
tissues in 473 
Morning glory, an annual plant 468 
Mosaic vision 113 
Mosquitoes, breeding places . 84 
life history 82 
members of Diptera ... 82 
Moths, example of Lepidoptera 65 
Moths and butterflies, field 
study of 73 
Motion, a fundamental function 15 
compared in organic and in- 
organic 16 
influence on organisms . . 32 
473, 535 22 
INDEX 
Motor fibers 374 
Mouse 209 
Mouth, of man 333 
Movable joints 270 
Movements, of leaves . . . 450 
Mucous glands of fish . . . 127 
Mule 232 
Mullein, flowers of 525 
Municipal health agencies . . 625 
quarantine 631 
Muscle, bundle 272 
Muscle cells, heart .... 273 
fibers 272 
involuntary 272 
voluntary 272 
Muscles, color of 272 
involuntary 272 
of man, discussed .... 272 
voluntary 272 
Mushrooms, edible fungi . . 575 
poisonous 575 
Muzzling of dogs 415 
Myosin 28 
Myriapods, discussed .... 119 
N 
Nails, origin of 366 
Narcotic, defined . . . 297, 319 
Narcotics, use of 319 
Nasal cavity of fish .... 132 
Nasturtium flower, example of 
adaptations 496 
National and International 
health activities .... 635 
quarantine 636 
National forest preserves . . 555 
National game preserves . . 182 
Native fruit, defined .... 10 
Natural enemies of potato 
beetle 70 
Natural gas, formation of . . 566 
Natural immunity 419 
Natural rate of breathing . . 288 
Near-sighted eyes 383 
Necessary destruction of mam- 
mals 219 
Necessity of fish protection . . 137 
of cultivation of the soil . . 592 
Necessity of re-foresting . . 551 
Nectar glands 498 
sought by insects .... 5 
References ar? to pages 
Nectar glands, continued 
use in blossom 5 
Needle-like leaves of pine . . 560 
Need for a study of forestry . 568 
Nerve cells 369 
Nerve fibers, defined .... 369 
description of 369 
gray substance of .... 371 
white substance of . . . . 371 
work of 371 
Nerve supply of muscles . . 275 
Nerves, cranial, of frog . . . 149 
location of 149 
number of, in man .... 273 
of frog 149 
Nervous system, growth of . . 372 
in grasshopper 57 
of crayfish 115 
of fish 132 
of frog 147 
of man 369 
parts of 369 
summary of 387 
Nest-building of birds . . . 172 
Nesting boxes .... 202, 204 
Net-veined leaf 445 
Neurons 369 
New discoveries, discussed . . 649 
New ideas, value of ... . 655 
New varieties of fruit developed 
by cross-pollination ... 11 
New York State Conservation 
Department 643 
Nighthawks, destroyers of mos- 
quitoes 84 
Nissl bodies 378 
Nitric acid, test for protein . . 537 
Nitrogen, a chemical element . 27 
gathered by bacteria ... 394 
in lipoid 321 
proportion of, in living things 27 
Nitrogen cycle .... 594, 620 
Node of corn stem 473 
Non-ruminants 210 
Non-smokers, scholarship of . 325 
Normal body temperature of 
man 293 
Norway maple 558 
Nose, sense organ 380 
Nostrums 326 
Notochord, embryonic structure 
of fishes 125 INDEX 
23 
Nourishment, defined.... 346 
Novius, enemy of cottony 
cushion scale 80 
Nucellus 531 
Nuclei of pollen and egg . . 506 
Nucleoli of cells 45 
Nucleus, of cell 45 
of nerve cell, action of alcohol 
upon 378 
Number of kinds of animals . 49 
Nurses, care of bee larvae by . 99 
Nuthatches, at suet station . . 202 
destroyers of Lepidoptera . 98 
Nutrients, defined 27 
in common foods .... 297 
named 27 
Nutrition a fundamental func- 
tion 17 
phases of 17 
Nuts, from hardwood trees . . 567 
furnished by walnut . . . 567 
indehiscent fruits . . . . 519 
Nymphs, of cicada 67 
of grasshopper 57 
O 
Oak trees 557-578 
Oat plant, root system of . . 490 
Oats, a cereal 526 
Obesity cures 327 
Obnoxious plants, names of . 516 
Ocellus, simple eye .... 54 
Odonata, order of insects . . 65 
Odor, use of, in flowers . . 513-514 
Odors of other foods absorbed 
by milk 398 
Oils, tests for .... 520, 537 
a class of foods .... 28 
Old age, a period in life his- 
tory 239 
Olfactory lobes, of frog . . . 147 
One-celled plants 438 
Onions, storage of food in . . 479 
Operculum of fish 126 
Opium, a poison 319 
Optic lobes of frog 148 
Optic nerve 382 
Opossum 208 
Orbits, defined 380 
Orchids, roots of . . . .489,491 
References are to pages 
Organ, defined 45 
of smell in fish 132 
Organic ash 30 
Organic matter, defined ... 24 
Organism, beginning of new . 612 
defined 24 
sensation in 15 
Organs, defined .... 24, 45 
of circulation of fish . . . 131 
ofcrayfish. . . '. . 110-115 
of frog 144 
of plants 437 
of respiration in man . . . 285 
Orioles, food of 186 
nest of 172 
Orthoptera, order of insects 59, 65 
Osmosis, defined 43 
in absorption of food . . . 342 
in photosynthesis .... 43 
in root hairs 487 
in sponges 615 
Outer coat of pollen grain . . 506 
Outer ear 384 
Outer skeleton, of crayfish . . 109 
of turtle 164 
Ovary, of frog 147 
part of pistil 497 
Overeating, results of . 327, 345 
Oviducts of frog 147 
Ovipositor of grasshopper . . 56 
Ovules, change to seed in . . 531 
described 500 
Owl, feet and beak of . . . . 194 
screech, beneficial .... 191 
snowy, a winter visitant . . 172 
Oxen 232 
Oxidation, physical .... 40 
physiological 40 
Oxygen, a chemical element . 26 
a condition for the growth of 
bacteria 390 
cycle 620 
proportion of, in living things 27 
use in respiration .... 291 
Oysters, examples of mollusks 120 
study of, by Bureau of Fish- 
eries 635 
P 
Palate of man 335 
Palisade cells of leaf .... 453 24 
INDEX 
Palmately compound leaves . 448 
Panama Canal, a health prob- 
lem 49 
Pancreas, of frog 146 
of man 337 
Pancreatic juice, enzymes in . 339 
Pancreatin 342 
Paper, made from wood pulp . 567 
Papillae of tongue 333 
Pappus 517 
Paraffin, in transpiration ex- 
periment 463 
Parallel venation 445 
of leaves of lily family. . . 445 
of grass leaves ..... 445 
Paramecium 246 
example of Protozoa . . . 246 
mode of defense 247 
study of 247 
Parasites, action of . . 70, 75, 87 
group of fungi 571 
tapeworms 416 
that injure hides .... 236 
Thalessa 87 
Parasitic flies 87 
Parasitism, a dependent rela- 
tion 87 
Parks 554 
Parsnips, storage of food in . . 489 
Partridge, wings of .... 193 
Parts of a flower found in nas- 
turtium 496 
Parts of a leaf 445 
Parts of a lily 499 
Parts of nervous system in man 369 
Pasteur, discoverer of lactic 
acid bacteria 396 
study of bacteria by . . . 396 
Pasteurization, defined . . . 396 
Pasteurized milk 397 
Patent medicines, defined . . 326 
to be avoided in consump- 
tion 409 
Patrolling of forests .... 551 
Peanut, source of calcium and 
phosphorus 30 
Peanut shucks as adulterant . 318 
Pea plant, modified leaves of . 449 
member of pulse family . . 462 
Pearl button industry . . . 121 
Pears, example of pome . . . 521 
Peat 567 
References are to pages 
Pectoral girdle, of man . . . 267 
of vertebrates 125 
Peculiarities of plant life . . 366 
Peg of hypocotyl 533 
Pelvic girdle, of man .... 267 
of vertebrates 125 
Pelvis, of kidney 363 
Penguins, use of wings . . . 193 
Peony 490 
Peppermint 463 
Pepsin, an enzyme . . 28, 41, 338 
Peptone in agar-agar formula . 392 
Perch, a bony fish 126 
Perennial roots 490 
Perfect flower, definition of . 497 
Perianth of lily family . . . 500 
Pericardium of man .... 353 
Pericarp 519 
Permanent residents .... 171 
Permanent teeth . . . 339, 341 
Perspiration, discussed . . . 366 
use of 294 
Petals, described .... 5, 496 
Petiole, of leaf 445 
of clematis 449 
of nasturtium 449 
Petri dish 392 
Petroleum, formation of . . . 566 
Pharynx, of earthworm . . . 606 
of man 335 
Pheasant, a seed-eater . . . 178 
wings of 193 
Phlegmatic temperament, heart 
tracing of . . . . . • 324 
Phloem, conducting food mate- 
rials 460 
discussed ....... 497 
position in woody stem . . 471 
position of, in vascular 
bundle 471 
Phoebes 190 
Phosphates 299 
Phosphorus, a chemical element 
found in living things . . 29 
a poison 404 
in lipoid 321 
in peanuts 29 
useful in body .... 29, 339 
Photosynthesis, defined ... 37 
discussed 37, 455 
finished product of ... . 456 
importance of ..... 39 INDEX 
25 
Photosynthesis, continued 
oxygen produced by . . . 39 
performed by stem .... 478 
use made of products of . . 456 
vital process in plants . . 37, 441 
Phylloxera, injurious insect . . 654 
Physical change described . . 30 
Physical training, value of . . 277 
Pieplant, example of perennial 
root 490 
Pigment in skin 365 
Pigs, even-toed mammals . . 210 
important mammals . . . 234 
Pike, a bony fish 126 
raised in hatcheries. . . . 139 
Pill-bug, a common land crus- 
tacean 119 
Pimples 328 
Pine, tree, described, a type . 559 
yellow, lumber of ... . 567 
Pineal gland 360 
Pistil, described 497 
Pitcher plant 449 
use of leaves in 449 
Pith, in corn stem 473 
in woody stem . . . 469, 471 
Placenta of flower 500 
Plague, an epidemic disease . 75 
Plague of locusts 59 
Planarian worm 416 
Plantain, a weed 505 
Plant, biology 436 
breeding 509, 651 
diseases 575 
lice 66 
members of Hemiptera . 66 
protected by ants . . . 105 
or animal matter food of 
bacteria 390 
Plant culture 585 
Plants as organisms, interest 
in 436 
Plants, general structure of . . 437 
Plasma 349 
Plecoptera, order of insects . . 65 
Plum, example of drupe . . . 521 
Plumage, discussed .... 196 
Plumes on wind-distributed 
seeds 522 
Plumule, connection with seed 
leaves 534 
part of embryo . . . . . 534 
References are to pages 
Pneumonia 295 
Pod, form of fruit 524 
Poison, defined 319 
in tobacco smoke . . 325, 383 
Poisons and neutralizing agents 425 
Poisonous character, of lizards, 
Gila monster 165 
of snakes 165 
of toxins 391 
Pollen, cell necessary for pro- 
ducing seed . . . 501, 510 
distributed by wind . . . 507 
of pine 561 
part of flower 5 
produced by stamens . . . 501 
sacs of pine 561 
tube, formation of ... . 506 
Pollen grains, growth through 
pistil 507 
Pollination, by wind .... 507 
definition of 505 
service of bee in 5 
step in production of fruit . 506 
Pome, a fleshy fruit .... 519 
Poplars, as shade trees . . . 557 
rapid growth of 568 
Poppy, capsule of 517 
Porcupine 209 
Pores of sponge 615 
Pork, inspection of . . 418, 426 
trichinella in 417 
Portal circulation . . . 343, 357 
Position of stems 467 
Potassium, a chemical ele- 
ment found in all living 
things 29 
contained in food .... 29 
use in body 339 
use to plants 29 
Potassium permanganate, a dis- 
infectant 423 
Potassium phosphate in Pas- 
teur solution 573 
Potato, a food plant .... 481 
beetle, injurious insect . . 68 
wart, a disease 575 
discussed 578 
Potential energy, defined . . 31 
Pouched animals 208 
Poultry destroyed by certain 
hawks 178 
Power of health officials . . 631 26 
References are to pages 
INDEX 
Practical problems connected 
with respiration and ex- 
cretion 292 
Praecocial birds, defined . . . 175 
Prairie dogs, harmful mam- 
mals 221 
Prairie horned larks at seed 
station 202 
Praying mantids, a family of 
Orthoptera 59 
Predigested foods, use of . . 346 
Premolar teeth, discussed . . 339 
Preparation of foods, dis- 
cussed 315, 398 
of soil 587 
Preservation of wood .... 565 
Preservatives, list of ... . 399 
use of, in milk 318 
Preventable diseases .... 407 
Prevention, of communicable 
diseases 409-410 
of epidemics 430 
Preventive measures against 
sickness 426 
Primary foods 297 
roots 488 
Primary functions and forms of 
roots 488 
Problem of sewage disposal . 628 
Proboscidia 209 
Proboscis of butterfly ... 97 
Products of cotton seeds . . 542 
of photosynthesis .... 456 
Propolis, defined 100 
use of, by bees 100 
Proper sewage 628 
Properties of wood .... 564 
Prop roots of corn 491 
Protection, of birds .... 179 
of forests 548 
of grasshopper 52 
Protective coloration, of birds . 196 
of crayfish 109 
of insects 89 
Protective resemblance ... 89 
Proteid substances in flour 
source of food for yeast 
plant 316 
Protein, a class of foods . 28, 299 
in bean 462 
product of photosynthesis . 461 
stored by bean 541 
Proteins of serum 317 
Prothorax of grasshopper . . 54 
Protoplasm, of cell 44, 46, 438, 608 
of pollen grain 506 
Protoplasmic activity .... 441 
Protozoa, cause of disease 407, 411 
discussed 241, 242 
flagellate 250 
number of kinds of . . . . 249 
resemblance to bacteria . . 389 
simplest animals .... 242 
Protozoa and alcohol .... 252 
Protozoan cell, described . . 242 
Protozoan diseases .... 407 
Prunes, source of iron, so- 
dium, potassium and phos- 
phorus 30 
Pruning 477 
Pseudopodium of amceba . . 244 
Ptomaines 398 
Ptyalin, an enzyme .... 338 
Public baths, institutions, ex- 
amination of servants for . 427 
Public markets 315 
Public museums 204 
Public parks 625 
Public preserves . . 181, 217, 646 
Puffins, nest of 172 
Pulmonary circulation . . . 354 
Pulmonary tuberculosis, dis- 
cussed 408 
Pulse caused by beating of 
heart 353 
Pulse family, foods furnished 
by 541 
list of plants of 462 
value to the soil of plants of 394 
Pupa, stage in the metamor- 
phosis of insects . . . 83, 96 
Pupil of eye 381 
Pure culture, defined .... 400 
of nitrogen-gathering bac- 
teria 395 
of yeast plant 572 
Pure food laws 318 
Pure milk, cost of produc- 
ing 395 
Pure water supply 626 
Purpose of respiration . 285, 291 
Pustules on wheat stems . . 581 
Pyloric valve of stomach . . 336 
Python, a constrictor . . . . 165 INDEX 
27 
Q 
Quack, defined 326 
Quack grass 479 
" Quadrupeds " 208 
Quail, a seed-eater .... 178 
food of 178 
Qualifications of a forester . . 568 
Quality of work a test . . . 379 
Quarantine against insects . . 77 
defined 414 
laws 415 
regulations 414 
violation of 415 
Quarter-sawn timber . . 565-566 
Queen bee 99 
R 
Rabbits, enemies of ... . 225 
groups of 224 
harmful animals 209 
protection of trees from . . 225 
Raceme 504 
Raccoon 208 
Range of plant's territory, how 
increased 522 
Raphe of beans 531 
Raptores, discussed . . . . 171 
Rats, harmful animals . 209, 220 
Rattlesnake, a poisonous snake 165 
fangs of 165 
poison, effect of 3 
Raw materials of photosyn- 
thesis 38 
Raw milk, danger from . . . 398 
Ray flowers of composites . . 505 
Receptacle, part of flower . . 498 
Recessive characters .... 659 
Reclamation of land .... 597 
Reclamation projects .... 5 
Recreative forms of exercise . 278 
Rectum, part of digestive 
system 336 
Recovery from fatigue of 
muscles 276 
Red corpuscles of blood . . . 349 
Red rust of wheat, a fungus . 581 
Red-shouldered hawk . . . 176 
Red squirrels, harmful ani- 
mals 222 
Redwood trees, age of . . . 468 
References are to pages 
Reflex action, discussed . . . 373 
in the frog 374 
in man 373 
Reforestation 551 
Refrigeration of foods . . . 400 
Regions of the body of man . 261 
Regular flowers, defined . . . 500 
Rejuvenation of worn-out land 545 
Relapsing fever, epidemic dis- 
ease 430 
Related forms of conifers . . 562 
Relation of heredity to human 
progress 585 
Relation of vaccination to hu- 
man progress 419 
Remedies, plants a source 
of 436, 463, 482, 494, 525, 541 
for clothes moths .... 71 
Report on mammals .... 222 
Reproduction, a life process . 18 
of amoeba 245 
of bacteria 391 
of fishes 133 
of frogs 146 
of grasshopper 57 
of hydra 619 
of paramecium 249 
of yeast plant 573 
Reproductive hyphae of bread 
mold 574 
Reptiles, discussed 162 
life history of 163 
summary of 169 
Resemblances between man 
and other animals . . . 255 
Residents, birds classed as . . 171 
Resin 567 
Respiration, a fundamental 
function 15 
a two-fold process . . .16, 285 
described 16 
in man 285 
organs of 285 
means of obtaining energy . 16 
of amoeba 245 
of fish 130 
of frogs 143 
of grasshopper 53 
of hydra 619 
of plants 460 
of paramecium 249 
produces carbonic acid gas 16, 285 28 
INDEX 
Respiration, continued 
purpose of 16, 285 
student report on ... . 285 
Respiration and excretion 363-364 
Rest and relaxation .... 375 
effect of, in consumption . . 409 
necessity for, in keeping well 375 
relieves fatigue 276 
Resting stage (pupa) of codling 
moth 7 
Restricted diet of primitive 
life ........ 299 
Retina 381 
Review and summary, of ab- 
sorption 611 
of carbon cycle 621 
of cellular structure of organ- 
isms 607 
of circulation 611 
of composition of living things 35 
of conservation . . . 624, 643 
of digestion 610 
of excretion 611 
of food-getting of animals . 610 
in plants 610 
of green plants 43 
of interdependence of animals 
and plants . . . 437, 441, 595 
of living things . . . . . 602 
of motion 609 
of nitrogen cycle . . . . 621 
of oxygen cycle 621 
of physical basis of life . . 48 
of plant and animal improve- 
ment 651 
of principal functions . . . 609 
of protoplasm 608 
of public health . . . 625, 635 
of relation of plants and ani- 
mals to man .... 14, 602 
of reproduction 611 
of respiration 610 
of sensation 609 
Rhinoceros 210 
Rhizomes 480 
Rhizopoda 244, 250 
Rhubarb, medicinal plant . . 494 
Rib of leaf 445 
Ribs of man 266 
Rice, a cereal 526 
importance of 526 
Rind of corn stem 473 
References are to pages 
Ripened ovary, the fruit of a 
plant 519 
Roadsters or trotting horses . 231 
Robber bees 100 
Robin, a useful bird .... 186 
sometimes a permanent resi- 
dent 186 
Rochelle salts in Fehling's solu- 
tion 42 
Rock oil, formation of . . . 566 
Rodentia 209 
Rodents, discussed . . . . 210 
Rod-shaped bacteria .... .389 
Root, part of plant ... 4, 485 
Rootcap 486 
Root hairs, discussed .... 487 
Roots, of alfalfa 490 
of beet 494 
of pine ........ 560 
Root system, of alfalfa . . . 490 
of wheat plant 490 
Rose-breasted grosbeak, de- 
stroyer of potato beetles . 68 
Rosette formation of leaves . 446 
Rotation of crops 598 
Rules of hygiene 401 
Ruminants 210 
Runners (stolons) 480 
Russian thistle 523 
Rye, a cereal 526 
S 
Sacrum 268 
Saddle horses 232 
Saffron, source of 525 
Sailing birds, examples . . . 193 
wings of 193 
Salamander, classified . . . 140 
discussed 141 
Saliva, of mosquito . . . . 412 
use of, in man . . . 338, 342 
Salivary glands, of man, loca- 
tion of 337 
of mosquito 412 
Salmon, example of bony fish . 126 
in hatcheries 139 
Salt, a fundamental taste . . 334 
common, scientific name of . 339 
use of, in preserving meat . 399 
Salt-rising bread 317 
Samara , 519 INDEX 
29 
Sand, a kind of soil .... 586 
Sand swallow, nest of . . . 172 
Sanitation, effect of, in prevent- 
ing disease 404 
San Jose scale, an injurious 
insect 66 
Sap, compared with blood . . 459 
conducted by vascular 
bundles 460 
Saprophytes, group of fungi . 571 
Sardines, example of bony fish 126 
Sawdust, adulterant .... 318 
Scale insects, spray for ... 66 
Scale-like leaves of cedar . . 562 
Scales, of fish 127 
modifications of skin . . . 366 
Scales of staminate cone of pine 561 
Scapula 267 
Scarlet fever, probable cause of 407 
Scars, characteristic of stem . 468 
Schaefer method of artificial 
breathing 290 
Scholarship, effect of smoking 
tobacco, on 325 
Scientific interest in plants . . 437 
Scion 476 
Sclerotic coat of eye .... 381 
Scorpions, example of Arach- 
nida 119 
Screech owl, a useful bird . . 191 
Scutellum, digestive organ of 
corn grain 535 
modified cotyledon .... 535 
Scutes of snake 165 
Sealing, object of 399 
Seals 208 
Sea-turtles 164 
Sea-worm a true worm . . . 415 
Secondary foods 298 
Seed, development of. . . . 531 
distribution of 522 
of pine 561 
Seed bud (plumule) .... 533 
Seed coat (testa) 531 
" Seed " corn 527 
Seed dispersal 532 
Seed-eating birds 178 
bills of 195 
toes of 194 
Seed-leaves 1 
Seedling, defined 534 
Seed-producing organs of pine 560 
References are to pages 
Seed selection 588 
Seed testing 588 
Seed wheat 527 
Seeds and germination . . . 531 
devices for distributing . . 522 
food of birds . . . . . . 178 
improvement in, by cross- 
pollination 508 
of cotton 542 
of weeds 178, 588 
Segments, of crayfish .... 109 
of grasshopper 55 
of worms 415 
Selection of seed 588 
Self-pollination, discussed . . 507 
prevention of 509 
Semi-circular canals of ear . . 384 
Sensation, a life process ... 15 
Sense organs, list of ... . 380 
of touch, location of . . . 380 
Senses, use of, in grasshopper . 52 
Sensitive plants 451 
Sensory function of afferent 
nerves 374 
Sepals, described 496 
Septic tanks 629 
Serrate edge of leaf .... 445 
Serum 421 
Setting of bones 270 
Setting-up exercises .... 277 
Seventeen year locust (cicada) 67 
Sewage, improper care of . . 629 
Sexual reproduction, of hydra . 619 
Shad, example of bony fish . . 126 
Shade trees 557 
Shaft of bone 271 
Sharks, a division of fishes . . 126 
Sheep, discussed 233 
even-toed ungulate . . . . 210 
Shepherd's purse, a weed . . 588 
Shocks, effect of 372 
Shrew 208 
Shrike (great northern), a win- 
ter visitant 172 
Shrimps, example of Crustacea 108 
Sieve plates 2 
Sieve vessels of phloem . . . 474 
use of 474 
Silica in corn stem 473 
Silk of corn, attachment of . . 535 
the style 510 
Silk worm 72 30 
INDEX 
Silver maple, poor shade tree . 557 
Simple eyes of insects ... 54 
Simple leaf, defined .... 448 
Sinus, defined 115 
Siphunculata, an order of in- 
sects 65 
Siphons of clams 121 
Sirup, maple 567 
Sitting, correct posture for . . 277 
Skate, edible fish 135 
Skeletal structures, student re- 
port on 272 
Skeleton, external, of birds . . 195 
of crayfish 109 
of man 262 
summary of 283 
of Protozoa 250 
Skin, as sense organ .... 380 
described 365 
example of organ .... 45 
Skull of man 263 
Skunk, example of harmful 
mammal 226 
Slant agar-agar tubes .... 392 
Sleep, amount needed . . . 376 
Sleep movements of plants . . 450 
Sleeping sickness, probable 
cause of 407 
Slimy substances of sponge re- 
moved by bacteria . . . 391 
Slips producing adventitious 
roots 492 
Sloth 208 
Small cells, position of, in an- 
nual ring 473 
Smallest plants 389 
Small intestine, of frog . . . 145 
of man 336 
Smallpox, Jenner and .... 420 
lessened by vaccination . . 420 
probable cause of ... . 407 
Smell, organ of, in grasshopper 52 
relation to taste 380 
sense of 380 
Smilax 478 
Smoke, result of chemical 
change 30 
Smoker's heart, effect of to- 
bacco illustrated .... 323 
Smoking and scholarship . . 325 
Snakes, discussed 165 
examples of Reptilia . . . 163 
References are to pages 
Snakes, continued 
fear of 165 
food of 165 
Snowy owl, a winter visitant . 172 
Soap in cosmetics 328 
Society for the Prevention of 
Cruelty to Animals . . . 217 
Soda, a nutrient, use of . . . 29 
preservative 396 
Sodium, found in prunes, car- 
rots, and spinach ... 30 
use of, in body 29 
Sodium carbonate in artificial 
pancreatic juice .... 342 
Sodium chloride, scientific name 
for common salt .... 339 
use, in body 339 
Soft palate of man 335 
Soil, an element of success in 
agriculture 585 
upper layers, habitat of bac- 
teria 390 
Soil bacteria 393 
Soil exhaustion 593 
Soldiers, a class of ants . . . 105 
Soles of feet, animals that walk 
on 211 
Solid, a form of matter ... 26 
Solitary flower 503 
Some common trees .... 556 
Song sparrow, at hemp and 
millet station 202 
useful bird 188 
Sounds from sound waves . . 385 
Sour, a fundamental taste . . 334 
Sour bread, cause of ... . 317 
Source of malarial parasite . 83, 411 
Source of man's food supply 437, 457 
Sources of danger in milk . 319, 397 
Souring of milk, cause of . . 396 
Spanish influenza 411 
Sparrow 187 
destroyer of cicadas ... 67 
example of useful bird . . 98 
fox, example of transient bird 172 
hawk, destroyer of grass- 
hoppers 60 
Sparrows, seed-eaters .... 178 
Spawn, migrations of fishes to . 133 
Spearmint, uses of 463 
Special adaptations . . . . 211 
Special modifications of plants 450 INDEX 
31 
Special senses, of fish . . . 130 
organs of 380 
Specialized roots 490 
Specialized stems 478 
Speed a test of efficiency . . 379 
Sperm, cells of fishes .... 133 
of hydra 619 
nucleus of pollen grains . . 506 
of vol vox 614 
Spermary of frog 147 
Sphinx moth from tomato worm 74 
Spicules, described .... 616 
Spider, member of Arachnida . 119 
Spinach, source of iron and 
sodium 30 
Spinal column of man . . . 266 
Spinal cord, part of nervous 
system 371 
Spines of porcupine .... 215 
Spiracles, of grasshopper . . 53 
Spiral arrangement of scales on 
cones 561 
Spirillum, a form of bacterium 389 
Spleen of frog 146 
Splints, use of, in setting bones 271 
Spoiling of food by bacteria . 398 
Sponges, described .... 615 
use of bacteria in preparation 
of 391 
Spongy bone 271 
layer of leaf 453 
tissue of velamens .... 491 
Spores, of bread mold . . . 574 
Sprain, defined 270 
Spraying to destroy insects . 11-12 
Spread of biological diseases . 427 
Spruce, cone-bearing tree . . 562 
Spur, part of flower .... 498 
Sputum, destruction of, neces- 
sary 409 
spread of tuberculosis by . . 409 
Squirrels, damage done by . . 210 
hinder reforestation . . . 551 
rodents 209 
Stamens, part of blossom . 5, 497 
Staminate cones of pine (pollen 
bearers) 561 
Staminate flower, of corn . . 509 
of willow 508 
Standing, correct posture for . 279 
Starch, a nutrient 27 
discussed 27 
References are to pages 
Starch, continued 
form of carbohydrate . . . 299 
in cosmetics 328 
in flour 316 
Starling 199 
State Department of Health . 632 
State parks and game pre- 
serves 182 
Statistics of life insurance com- 
panies 321 
Steam, a form of water ... 30 
Steapsin, a ferment .... 339 
Stegomyia, a mosquito (Aedes) 
Stem, adaptations of ... . 467 
as a means of propagating 
plants 475 
function of 467 
monocotyledonous .... 466 
of cactus plants 478 
of conifer 559 
of corn 473 
part of plant 4 
uses of, to plant 4 
woody 466 
Stems, discussed 466 
home work 475 
Sternum, of man 266 
keeled, of birds 195 
Sticklebacks, nests of. . . . 134 
Stigma, feathery 508 
part of pistil 497 
Stimulants 297 
Stimulants and narcotics . . 319 
Stimuli, defined 15 
Stinging cells of hydra . . . 618 
Sting of bee 100 
Stipules, part of leaf .... 445 
Stock and scion 476 
Stolon 480 
Stomach, a digestive organ . . 333 
example of organ .... 45 
of frog 145 
of man 336 
valves of 336 
Stomata, number of ... . 455 
of leaf 452 
position of, in floating leaves 452 
Stoneflies, members of Plecop- 
tera 65 
Storage of food in leaves . . 456 
Strap-shaped flowers .... 505 
Stream purification .... 629 32 
References are to pages 
INDEX 
Street cleaning by flushing, 
advantage of 409 
String beans, value of, as food 542 
" Strings " of celery .... 466 
Structural changes due to 
alcohol 322, 378 
Structure, of amoeba .... 243 
of bone 271 
of leaf 452 
of lily 499 
of paramecium 247 
of pollen grain 506 
of roots 485 
of vascular bundle . . 471, 473 
of woody stems 469 
Student report, on adaptations 
in animals 258 
' on digestion 342 
on digestive system. . . . 337 
on sickness 419 
on skeletal structures . . . 272 
on water supply 627 
Studies about plants, kinds of . 436 
Study of an apple 521 
of birds 175 
Study of an orange .... 520 
Study of a tomato 521 
Study of plants as organisms . 437 
Study of variation in wheat. . 652 
Style, part of pistil .... 497 
Subsoil 587 
Substitutes for sugar .... 311 
Substitutes for butter . . . . 311 
Success in cultivating plants . 442 
Sucking lice example of Suctoria 65 
Suctoria, an order of insects . 65 
Suet, for winter feeding of birds 201 
station 202 
Suet-eating birds 202 
Suffocation, and artificial 
breathing 290 
discussed 290 
Sugar, a nutrient. 27 
a preservative 399 
broken up by yeast enzyme . 317 
form of carbohydrate . . . 299 
in flour 317 
lessens fatigue 276 
obtained from maple trees . 567 
product of photosynthesis . 39 
source of 567 
value of, as food .... 307 
Sulphur, a disinfectant . . . 423 
a germicide 393 
an element in animal and 
vegetable tissues .... 29 
sulphur dioxide 423 
Summary, of amphibians . . 160 
of arthropods 123 
of bacteria 402 
of birds 206 
of circulation 361 
of conifers 570 
of crab family 123 
of digestion in man .... 347 
of disease 434 
of excretion 367 
of fish 140 
of flowering plants .... 529 
of fungi 584 
of grasshopper 61 
of insects 93 
of mammals 239 
of moths and butterflies . . 107 
of nervous system of man . 387 
of our interest in plants . . 437 
of reptiles 169 
of resemblances between man 
and other animals . . . 260 
of simplest plants .... 402 
of skeleton of man .... 283 
Summer residents, examples of 172 
Sunburn 365 
Sundew, use of leaves in . . 449 
Sunfish, care of eggs by . . . 134 
example of bony fish . . . 126 
Sunflower, " seed " at feeding 
station for birds .... 201 
Sunlight, a disinfectant . . . 393 
Superiority of man . . . . 261 
Supervision of the milk supply 630 
Supply of oxygen kept up by 
plants . 457 
Surface soil 587 
Surplus food stored in roots . 488 
Sutures of bone 270 
Swallows, destroyers of flying 
insects ....... 189 
Swallow-tail butterfly, from 
celery worms 94 
larvae of 94 
Swarming of bees ..... 101 
Sweat glands, discussed . . . 366 
Sweet, a fundamental taste . . 334 INDEX 
33 
Sycamore, useful shade tree . 558 
Symbiosis, defined 394 
nitrogen-gathering bacteria . 394 
Sympathetic system .... 372 
Symptoms, medicines in con- 
nection with 326 
Systematic exercise .... 289 
Systemic circulation .... 355 
T 
Table showing consumption, of 
carbohydrates .... 301 
of fats 307 
of foods 317 
of protein 308 
Tachina-fly, beneficial insect . 87 
Tadpole, development of, from 
egg 151 
stage of frog 151 
Tail region of fish 127 
Talons, characteristic of birds 
of prey 171 
Tanning, use of hemlock bark 
in 236, 562 
Tapeworm, a common . . . 416 
Tap roots 488 
Tapir, odd-toed ungulate . . 210 
Tarsus of grasshopper's foot . 56 
Tartar, effect on gums . . . 340 
Tassel, staminate flower of corn 509 
Taste 334 
Teeth, of adults 339 
of frog 144 
irregular, of children . . . 341 
Telegraph poles, use of trees for 482 
Temperament, nervous, effect 
of smoking on 324 
phlegmatic, effect of smoking 
on 324 
Temperate regions as a habitat 
of evergreens 562 
Temperature, and ventilation . 292 
of birds 196 
of blood 351 
of fish 132 
of soil, an element of success 
in agriculture 591 
Tendon 273 
Tendrils of pea plant .... 449 
Tentacles of hydra .... 618 
Tent caterpillar 71 
References are to pages 
Terminal bud 468 
cones in relation to ... . 563 
Terrapin, use of, as food . . . 164 
Testa developed from integu- 
ment 531 
Testimonials for patent medi- 
cines 328 
Testing seed 589 
Texas fever in cattle, cause of . 119 
Thalamencephalon of frog . . 150 
Thalessa, parasitic fly . . . 87 
Thickened fibrous roots . . . 489 
Thick stems for food storage . 480 
Thick-walled cells of annual 
ring, how formed . . . 473 
Thinning and transplanting . 592 
Thin-walled cells, when formed 560 
Thistle, a common weed . . 479 
Thoracic cavity of man . . . 261 
Thoracic duct 343 
Thorax, of grasshopper ... 53 
Thorn, modified leaf .... 449 
Thousand-legged worms. . . 120 
Thread-like hairs, of spirilla 
and bacilli 390 
Threads, of bread mold . . . 574 
Throat, cavity of man . . . 339 
of tadpole .... 151, 152 
Thymus gland 360 
Thyroid extract, use of . . . 328 
Thyroid gland 360 
Thyrse 504 
Thysamura, an order of insects 65 
Tibia, of grasshopper .... 56 
Tickle-grass 523 
Ticks, harmful insects . . . 119 
members of Arachnida . . 119 
Tight clothing, effect on respira- 
tion 290 
Timbers of mines, use of trees 
for 482 
Tissue, definition of ... . 45 
Tissues of woody stem of 
dicotyledon 469 
Toad, common 154 
horned 165 
Toadfish 135 
Toads, hibernation of ... 154 
Tobacco, effects of use of . . . 322 
inhaling fumes 323 
Tobacco worm, cocoons of 
parasite on 97 34 
INDEX 
Toes of cow 210 
Tomato, a food plant .... 527 
worms, larvae of sphinx moth 74 
Tongue, a sense organ . . . 334 
of frog 144 
of man 339 
Toothache, result of poor teeth 340 
Toothless animals (mammals) . 208 
Tortoise, use of, as food . . . 164 
Toxin, bacterial poison . . . 391 
of diphtheria 421 
secreted by bacteria . . . 391 
Trachea, of man 285 
Tracheae, of grasshopper . . 53 
Transient birds, examples of . 172 
Transpiration, amount of water 
given off by 458 
defined 455, 457 
devices for retarding . . . 457 
laboratory work on ... 462 
Tree sparrow, at bread crumb 
station 202 
Tree surgery 555 
Trees, in parks and streets . 555 
Tremex borer, harmful insect . 87 
Trench fever 75 
Trichina, discussed .... 417 
Trichinella, discussed .... 417 
Trichinosis, cause of ... . 418 
Trichocysts of paramecium . . 247 
Trichoptera, an order of insects 65 
Trillium, picking of .... 517 
Trochanter 53 
Tropical regions, first home of 
man 257 
Trout, example of bony fish . 126 
Trunk animals 209 
Trunk of elephant 215 
Trunk region, of fish .... 126 
of man 261 
Trunks of evergreens .... 559 
Trypsin, an enzyme .... 339 
Tuber, an underground stem . 479 
Tuberculin test, discovered by 
Koch 397 
for cows 397 
Tuberculosis, a bacterial dis- 
ease . . 406 
discussed 407 
in cows 397 
of throat and other organs . 295 
treatment for .... 408-409 
References are to pages 
Tubular flowers 505 
Tubules of kidney 363 
Tulip tree 558 
Tumors 404 
Turgid cells 454 
Turnip, example of biennial 
root 489 
storage of food in ... . 489 
Turpentine, source of ... 567 
Turtle, example of Reptilia . . 163 
green, use of, as food . . . 164 
skeleton of 164 
Turtles, discussed 164 
Tusks of elephant 215 
Twining petiole, of clematis . 449 
Twining stems 15, 467 
Tympanic cavity 384 
Types of cattle, discussed . . 232 
Types of heads, of fruits . . . 519 
of inflorescence 503 
horses discussed 230 
pigs discussed 234 
sheep discussed 233 
Typhoid fever, a bacterial dis- 
ease 406, 427 
spread by carriers .... 427 
Typhus fever 75 
U 
Umbel 504 
Underground stems, described 278 
examples of 279 
Undissolved food 344 
Ungulata, a group of mammals 210 
Unhealthy cows, milk from . . 397 
Unicellular fungus, yeast. an 
example 571 
United States, biological sur- 
veys 645 
fish commission 644 
Unsolved problems in disease . 432 
Unwashed hands, number of 
bacteria on 392 
Ureter, of frog 146 
of man 364 
Urethra, of man 364 
Urinary bladder of frog . . . 146 
Uriniferous tubule 364 
Uropod, organ of crayfish . . 110 
Use and abuse of the muscles . 278 
Use of fertilizers 594 INDEX 
35 
Useful birds, examples of . . 178 
Uses and necessity of oxygen . 291 
Uses, of fruits to man . . . 525 
of nutrients in the body . . 299 
of roots to man 494 
of stem, to man 481 
to plant 467 
of terms " fruit," " seeds," 
etc 527 
of wood 481-482 
V 
Vaccination, discussed . . . 419 
Vaccine 421 
Vacuole, food, of amoeba . . 245 
contractile 245 
Vacuoles, in nerve cells . . . 378 
Vacuum cleaners 422 
Valves, of veins 357 
of clam shell 120 
of stomach 336 
Vapor, a form of water ... 30 
Variations, in beaks of birds . 194 
in legs of birds 193 
Varied diet of man .... 299 
Variety of animal life .... 49 
Vascular bundles, arrangement 
of 470, 473 
formation of tubes by . . . 474 
of root (conducting vessels) . 486 
of woody stems 469 
Vascular system in plants . . 453 
469, 473, 486 
Vaseline, use of, in transpira- 
tion experiment .... 463 
Vegetable nitrogen, source of . 394 
Vegetable ivory, source of . . 237 
Vegetable oyster, biennial 
root 489 
food of man 494 
Veins, compared with fibro- 
vascular bundles . . . 459, 466 
of leaf 445 
of man 353 
Velamens 491 
Venation 445 
Veneer 567 
Ventilation 292 
Ventral nerve chain of cray- 
fish 115 
Ventral surface of earthworm . 606 
References are to pages 
Ventricle (fourth) of brain . . 148 
Ventricles of heart .... 353 
Venus's flytrap 449 
use of leaves in 449 
Vermiform appendix .... 336 
Vermin (lice, etc.) . . .74, 430 
Vertebrae 266 
Vertebrates, a group of animals 
discussed 124 
Viability of seeds 532 
Villi, described .... 337, 343 
Vinegar, a preservative . . . 399 
Virgin forest in United States . 546 
Virus in inoculation .... 421 
Vital functions of amoeba 244, 246 
Vitamins 30 
diseases caused by deficiency 
of 306 
list of foods containing . . 306 
names of 305 
necessary 30 
use of 306 
Vitreous humor 381 
Vivisectors 433 
Vocal cords, location of . . . 286 
Voice box, the 286 
Voluntary muscle cells . . . 272 
Voluntary muscles .... 272 
Volvox, described 614 
Vomiting 336 
Vultures, beneficial birds . . 177 
example of Raptores . . . 171 
W 
Walking, correct position of the 
feet in 279 
Walking legs of crayfish . . . Ill 
Walking sticks 59 
Walnut, plant protein in . . 299 
Walnut tree 567 
Walrus 221 
Ward-Mcllheny Bird Preserve 181 
War gardens 314 
Warm-blooded animals . . . 207 
Warm milk, multiplication of 
bacteria in 398 
Warmth, a condition of the 
growth of bacteria . . . 390 
Warning coloration .... 90 
Washing away of soil by 
floods 544 36 
INDEX 
Wasp-fly, beneficial insect . . 82 
Waste materials of photosyn- 
thesis (by-products) . . 39 
Waste products of body . . 363, 365 
removed by excretion . . . 363 
Wash for protection of trees 
from rabbits 226 
Water, a necessary condition 
for growth of bacteria . . 390 
contains bacteria .... 390 
composition of 29 
sanitary measures for pro- 
tecting 626 
supply, student report on . 627 
universal solvent .... 29 
uses of, in body 29 
Water beetles, destroyers of 
mosquitoes 84 
Water-tiger, larva of water 
beetle 129 
Water roots 489 
Water supply 626 
Wax, in ear 385 
produced in U. S., value of . 104 
Weasels, enemies of ... . 225 
harmful animals .... 226 
Webbed toes, of swimming 
birds 194 
Wedding flight of bee . . . 103 
Weeds, common, list of . . . 516 
definition of 599 
seeds destroyed by birds . . 178 
Weeks-McLean Law .... 180 
Weevils, example of beetle . . 67 
injurious insects 63 
Well-balanced diet .... 307 
Wells, as source of water supply 628 
Whale, a marine mammal . . 209 
Wheat, a cereal ..... 526 
Where bacteria are found . . 390 
Where foodstuffs are stored in 
seeds 538 
White blood corpuscles . . . 350 
White-breasted nuthatch at 
feeding station .... 202 
Whitefish, example of a bony 
fish 126 
White grubs, eaten by birds . 68 
White oak, uses of . . . . 567 
White of the eye 381 
White pine, value of ... . 567 
White substance of nerves . . 371 
References are to pages 
Whiting, edible fish .... 136 
Whooping cough, a bacterial 
disease 407 
Wigglers, larvae of mosquitoes . 82 
Wild plants, improvement of, 
by man 9-10 
Willow tree, source of char- 
coal 567 
Wind-distributed fruits . . . 522 
Window-growing plants, re- 
sponse to light in ... 451 
Windpipe 285 
Wind-pollinated flowers, of 
grass family 508 
characteristics of .... 508 
Wind pollination 508 
Winglike air sacs of pine pol- 
len 561 
Wing of pine seed . ! . . . 562 
Wings, of birds 193 
of fruits 523 
Winter visitants, examples of . 172 
Witch-hazel, explosive fruit of . 524 
Wood, formation of .... 473 
Wood alcohol 567 
Wood borers 87 
Woodchuck, a rodent .... 210 
Wooded area, under govern- 
ment control ..... 554 
Woodpeckers, at suet station . 202 
(downy) permanent resi- 
dents 171 
food of 188 
Wood-pulp, source of ... . 567 
Woody stem, structure of 469, 559 
use of elements in ... . 469 
Woody twig, buds of . . . . 468 
Wool, source of 233 
Woolly aphis, member of He- 
miptera 66 
Work, of a leaf 455 
of a forest ranger .... 548 
of special health agencies . 638 
of the heart 352 
of the yeast plant . . . . 572 
Work of the vascular bundle . 474 
Workers (bees) 99 
Worm, planarian 416 
Worm group, discussed . . . 415 
Worm-like animals, classified . 415 
Wren, a useful bird .... 192 
food of 98 INDEX 
37 
References are to pages 
X 
Xylem, conductor of water . . 459 
in fibrovascular bundle of 
corn 473 
in vascular bundle .... 459 
relation to cambium . . . 471 
Y 
Year's growth of twig, how told 468 
Yeast, enzyme of . . . . . 317 
use of 317 
reproduction of ... . 573 
in bread-making .... 316 
Yeast, continued 
plant, described 571 
work of 572 
Yellow fever, carried by mos- 
quito 413 
caused by Protozoa . . . 407 
Yellow pine, value of . . . . 567 
Yellow warbler 192 
Yolk, of fishes' eggs .... 133 
Youth, a period of life . . . 259 
Z 
Zymase, work of 317