A MANUAL 
OF 
HISTOLOGY 
EDITED AND PREPARED BY 
THOMAS E. SATTERTH WAITE, M.D., 
OF NEW YORK 
Professor of Histological and Pathological Anatomy in the New York Post-Graduate Medi- 
cal College, Pathologist to the St. Luke's and Presbyterian Hospitals, etc. 
IN ASSOCIATION WITH 
Drs. Thomas Dwight, J. Collins Warken, William P. Whitney, Clarence J. 
Blake, and C. H. Williams, of Boston; Dr. J. Henry C. Simes, of Philadel- 
phia ; Dr. Benjamin P. Westbrook, of Brooklyn; and Drs. Edmund C. 
Wendt, Abraham Mayer, R. W. Amidon, A. R. Robinson, W. R. 
Birdsall, D. Bryson Delay an, C. L. Dana, and W. H. 
Porter, of New York City 
SECOND EDITION, ENLARGED AND REVISED, CONTAINING TWO HUN- 
BRED AND TWO ILLUSTRATIONS, WITH AN APPENDIX 
NEW YORK 
WILLIAM WOOD & COMPANY 
56 and 58 Lafayette Place 
1883 WILLIAM WOOD & COMPANY 
1881 
Copyright by 
Trow’s 
Printing and Bookbinding Company 
201-213 East sith Street 
NEW YORK PREFACE TO THE SECOND EDITION. 
The editor, in preparing the second edition, acknowledges 
that the favor with which the first edition was received, both 
at home and, in Great Britain, has been a matter of pleasure 
and of surprise to him, and probably no less so to those who 
aided him in the work. But he was totally unprepared for 
the announcement, a few months after the publication of the 
volume, that a second edition would soon be needed. This 
task has now been accomplished, though not in a manner to 
satisfy the rigid requirements of such a book, which should 
be in all respects abreast of the time at which it is issued. 
Practically speaking, however, it has been the opinion of the 
collaborators that the positive advances that have been made 
in the field of Histology during the brief interval alluded to 
have not been sufficient to justify any extensive alterations 
in the text-matter, especially in view of the great expense 
attending such changes. The editor, in taking this occasion 
to thank his able reviewers for the many valuable sug- 
gestions they have offered, states at the same time that only 
such textual changes have now been made that were neces- 
saiy to remedy those manifest errors that will unavoidably 
creep in. An appendix, however, is now added, and it is 
hoped that this new text-matter, illustrations, and recent 
bibliographical references will add to the usefulness of the 
book and make it continue to merit the favor of practi- 
tioners and students of medicine. 
T. E. S. PREFACE TO THE FIRST EDITION. 
For some years past there has been a general demand 
among the members of onr profession for a manual of Histol- 
ogy, summarizing, in concise and plain language, our present 
knowledge in this fundamental branch of medicine. It is true 
many books have been written on the subject, but their great 
brevity, on the one hand, or an unnecessary diffuseness on the 
other, have prevented them from meeting with acceptance at 
the hands of physicians and students. In the one class belong 
the little handbooks of Rutherford and Schaefer, which have 
done much to simplify and therefore popularize histology, but 
they were intended for beginners, and especially students doing 
class-work under the laboratory system now so much in vogue. 
But both physician and student need something of wider scope, 
and they have been compelled to turn to Klein & Smith, 
Strieker, or Frey, though no one of these excellent works is 
thoroughly adapted to their wants. 
Apart from the expense of the two former, they all are 
deficient in matters relating to human histology. 
The practical experience of a teacher made it evident also 
that the volume to fill such an obvious gap should take the 
form of a text-book. And the present time seemed opportune 
for its appearance, since we have latterly made much positive VI 
PREFACE. 
advance in histological studies, while histologists themselves 
are now more of one mind in microscopical matters. That such 
a book should appear under American auspices seemed further 
to be eminently proper, as we have in various parts of the coun- 
try a goodly number of medical men who are either engaged 
in teaching histology or in studying some special branch of it. 
The advantages of utilizing their accumulated experiences 
was therefore apparent to the editor, and he gladly applied 
to them for assistance when it was found that one individual 
could not prepare the volume within a reasonable time or 
in a manner that would be satisfactory. It is hoped that 
the names of the collaborators furnish a sufficient guarantee 
that proper representatives of American histology have been 
selected. In some respects the object sought for has not been 
wholly attained, as, for example, in the effort to separate 
purely human histology from the comparative. But this is 
impossible at the present time, mainly because our knowl- 
edge is still too limited. It is a matter of regret, also, that the 
original illustrations have been so few in comparison with the 
total number, but the great expense attending their production 
would not warrant any one in attempting much in this direc- 
tion. Through the kind co-operation, however, of Messrs. Wil- 
liam Wood & Co., the editor has been able to utilize many 
excellent cuts that were in their possession. 
As a further means of relieving the tedium associated with 
a work that is so largely descriptive, the various authors have 
aimed to intersperse here and there throughout the text mat- 
ters of physiological or pathological import. Still, intelligent 
practitioners do not have to be reminded that rational thera- 
peutics has found a substantial support in the revelations of 
pathological anatomy, which, in turn, rests upon histology, PREFACE. 
so that the relation between microscopic anatomy and the sci- 
entific practice of medicine is readily appreciated. 
Emanating as the volume does from American sources, the 
editor finds it a fitting place to give proper space to American 
contributions, and the reader may therefore find due notice of 
the physiological desquamation of blood-vessels, considerations 
on the nature of nerve-termini, matters relating to the intimate 
structure of the striped muscular fibre and nerves, with the 
results of studies on the structure and development of certain 
connective substances, and novelties in microscopic apparatus 
and methods. A special chapter is also given to the thick 
cutis vera, now for the first time described as a distinctive 
portion of the skin. In it will be found detailed the discovery 
of the fat-columns, which are calculated to explain certain 
pathological changes that have been imperfectly understood. 
The first chapters of the book are devoted to the mechanism 
of the microscope, and to certain formal methods of work with 
which the beginner should be familiar. Of the illustrations, 
sixty-five were prepared for the volume, while forty have never, 
it is believed, appeared in book-form. The remainder are 
mostly from the manuals of Strieker and Frey. 
A limited number of bibliographical references have been in- 
serted where it was thought they were desirable in guiding 
the reader to the literature of the subject. For the prepara- 
tion of these tables and much valuable assistance, the editor 
here desires to express his thanks to Dr. E. C. Wendt, of this 
city. 
It was thought best to omit the subject of optical principles 
which figure so conspicuously in some of our histological 
manuals. Those who wish information on these matters are 
referred to any of the standard text-books on physics, where PREFACE. 
the subject is treated at greater length than was permissible in 
the present instance. 
For a similar reason, and also because it would prove a 
needless expense, the price-lists of instrument-makers have 
been omitted. Full particulars relating to the various sorts of 
microscopes and their accessories can be obtained from any 
of the leading opticians, who from time to time issue lists con- 
taining ample illustrations of the most recent improvements 
in all that pertains to practical working of the instrument. 
In conclusion, the editor finds himself compelled to reiter- 
ate the well-worn statement, that circumstances over which he 
has had no control have united to delay the press-work of 
the volume, and at the end have made its final revision rather 
hasty. A kind indulgence is therefore asked for any error 
that may, through oversight, have escaped his notice. 
T. E. S. TABLE OF CONTENTS. 
FART I. 
CHAPTER I. 
THOMAS E. SATTERTHWAITE, M.D. 
Materials Requisite for Histological Work.—How to Use the Micro- 
scope.—Testing the Microscope.—lts Uses Page 1 
Appliances for microscopic work, 1. Chemical reagents, 3. Illumina- 
tion, 4. Stage diaphragms, 5. The mirrors, 5. Direct and oblique light, 5. 
Arrangement of the object, 6. Kind of lens to use, 6. How to keep the 
instrument clean, 7. Magnifying power of a lens, 7. How to estimate the 
size of an object, 8. Testing a lens, 8. How to illumina'e the object, 9. 
Testing the eye-piece, 10. Testing high lenses, 10. Measuring the angle of 
a lens, 10. 
CHAPTER 11. 
THOMAS E. SATTERTHWAITE, M.D. 
Methods for Preparing Microscopic Objects Page 13 
General directions, 13. To prepare fresh objects for rapid examination, 
18. Ordinary methods of preparing tissues, 18. Muller’s fluid, 14. Potas- 
sium bichromate solution, 14. Ammonia bichromate solution, 14. Alcohol 
and acetic acid mixtures, 14, 15. Molybdate of ammonia, 15. Solution of 
osmic and chromic acids, 15. Alcohol and acetic acid, and muriatic acid 
solution, 15. Method of hardening the brain, 15. How to embed speci- 
mens, 15. Embedding in glycerine and tragacanth, 16. The hand section- 
cutter, 16. Freezing section-cutters, 17. Hailes’ microtome, 19. The 
Vincent microtome, 21. Staining fluids, ammonia carmine, 31. Borax car- 
mine, 33. Double staining, 33. Hcematoxylon solutions, 33, 34. Solutions 
for multiple staining, 34, 25. Preparation of the cornea, 35. Triple stain- X 
TABLE OP CONTEXTS. 
ing, 26. Double, triple and quadruple staining, 26. Bismark brown, 26. 
Solution of alum carmine, 27. Naphthaline yellow for bone, 27. Methyl 
green and induline, 27. Purpurine, 28. French archil, 28. Alizarine, 28. 
Metallic solutions, staining with osmic and oxalic acids, 28. Chloride of 
gold and lemon juice, 28. Nitrate of silver, 29. Chloride of gold, 29. 
Osmic acid, 29. Methyl green for waxy change, 29. Wickersheimer’s 
liquid, 29. Methods of injecting the blood-vessels, 30. 
CHAPTER 111. 
THOMAS E. SATTERTHWAITE, M.D. 
The Blood Page 34 
Red corpuscles, 34. Comparative measurements in men and animals, 36. 
Number of, 37. Corpuscles in an indifferent fluid, 38. Brownian and 
amoeboid movements, 39. Heating slide, 40. Action of dilute salt solution, 
40. Action of distilled water—irrigation, 41. Action of carbonic acid gas, 
42. Action of acids, 43. Action of alkalies, 44. Action of electricity, 44. 
Exhibition of the circulation, 45. Internal structure of red corpuscles, 46. 
Development, 47. White corpuscles, 48. Counting corpuscles, 48. Blood 
crystals, 53. Hasmoglobin, 53. Hsemochromometer, 54. Bibliography, 54. 
CHAPTER IY. 
THOMAS E. SATTERTHWAITE, M.D. 
Epithelium Page 56 
Ordinary flattened or squamous epithelium, 57. Ciliated epithelium, 58. 
Effect of reagents, 59. Columnar or cylindrical epithelium, 60. Other va- 
rieties, 61. Structure of epithelial corpuscles, 61. Bibliography, 61. 
CHAPTER Y. 
THOMAS B. SATTERTHWAITE, M.D. 
The Connective Substance Group.—Mucous or Gelatinous Tissue.— 
Adenoid Tissue.—Neuroglia.—Fat Tissue.—Fibrous Tissue Prop- 
er.—Corneal Tissue.—Intermuscular Tissue,—Tendon Tissue.— 
Elastic Tissue Page 63 
Connective substances in general, 62. Mucous or gelatinous tissue, 63. 
Development of fibrous tissue, 64, 65. Fibrous tissue, 66. Adenoid tissue, 
69. Neuroglia, 70. Tendon tissue, 72. Fat tissue, 73. Intermuscular 
tissue, 74. Corneal tissue, 75. Elastic tissue, 77. Pavement endothe- 
lium, 80. Bibliography, 81. TABLE OF CONTENTS. 
CHAPTER YI. 
THOMAS E. SATTERTHWAITE, M.D. 
The Connective-Substance Gboup (Continued!).—Caktilagb Page 83 
Hyaline cartilage, 83. Parenchymatous cartilage, 83. Division of the 
corpuscle, 84. Calcification, 84. Methods of studying hyaline cartilage, 
84. Yellow elastic cartilage, 85. Pibrous cartilage, 86. Structure of cor- 
puscle, 87. Bibliography, 88. 
CHAPTER YIL 
THOMAS E. SATTERTHWAITE, M.D. 
The Connective-Substance Group {Continued).—Bone Page 89 
Compact tissue, 89. Ossein, 89. Bone-corpuscles, 90. Haversian sys- 
tem, 90. Preparation of dry bone, 93. Preparation of decalcified bone, 93. 
Sharpey’s fibres, 94. Cancellous tissue, 94. Marrow, 95. Periosteum, 95. 
Development of bone, 96; through cartilage, 97; from membrane, de- 
velopment and absorption, 99. Howship’s lacunae, 100. Formation of cal- 
lus, 100. Bibliography, 101. 
CHAPTER YIII, 
THOMAS E. SATTERTHWAITE, M.D. 
The Teeth Page 102 
The enamel, 102. Dentine or ivory, 103. Dentinal globules, 104. Cement, 
105. Pulp, 105. Development of teeth, 105. Primary enamel organ, 107. 
Development of enamel, 108. Bibliography, 108. 
CHAPTER IX. 
THOMAS E. SATTERTHWAITE, M.D. 
General Histology of the Nervous System Page 109 
Nerve-fibres, 109. Myelinic fibres, 109. Staining in picro-carmine, 111. 
Staining with silver, 112. Staining with osmic acid, 113. Semi-desicca- 
tion, 113. Transverse sections of myelinic nerves, 114, Preparation by 
ammonia bichromate, 115. Modern conceptions of myelinic nerves, 110. 
Fibres of Remak, preparations in osmic acid and picro-carmine, 118. Prep- 
arations of Remak’s fibres in htematoxylon, 118. Ganglionic bodies, 119. 
Ganglia of the cranial and spinal nerves, 120. Gasserian ganglion, 120. 
Ganglionic bodies of the spinal cord, 120. Brain, 121. Sympathetic, 121. 
Meissner’s plexus, 122. Auerbach’s plexus, 123. Termination of nerves, 
123. Tactile corpuscles, 124. Pacinian bodies, 124. Nerve-terminations 
in muscle, 125 ; in epithelium, 126. Connective tissue of nerves, 126. 
Bibliography, 127 TABLE OE CONTENTS. 
PART II 
CHAPTER X. 
THOMAS DWIGHT, M.D, 
Muscular Fibre Page 128 
Involuntary muscular fibre, 128. Voluntary muscular fibre, 130. Physi- 
ological attributes, 134. Nuclei and muscle corpuscles, 136. Conclusions, 
187. Peculiarities of voluntary muscles, 138. Termination of muscle in 
tendon, 139. Muscular fibre of the heart, 140. Bibliography, 140. 
CHAPTER XL 
EDMUND C. WENDT, M.D. 
The Blood-Vessels Page 142 
Capillary blood-vessels, 142. Vascular endothelium, 143. Capillaries 
proper, 144. Genesis, reproduction, and regeneration of capillaries, 150. 
Arteries, 151. Veins, 155. Peculiar vascular structures, 158. Blood-vas- 
cular glands, vascular plexuses, 158. Intercarotid gland, 160. Corpora 
cavernosa, 160. Vasa vasorum, lymphatics, and nerves, 161. Bibliography, 
162. 
CHAPTER XII. 
W. E. BIRDSALL, M.D. 
The Lymphatic System Page 163 
Modern views of, relative to connective tissue, 168. General histology, 
164. Lymphatics of the mesentery, 165. Klein’s studies on the omentum, 
166. Perilymphangeal nodules, 167. Development of fat-tissue, 168. Lym- 
phatic radicles, 168, Artificial injection of lymphatics, 169. Endothelium 
and stomata. 169. False stomata, 170, 171. Intimate structure of lym- 
phatic vessels, 172. Variations in shape, 178. Topographical peculiarities, 
174. Thoracic duct, 174. Subarachnoid and subdural spaces, 175. Lym- 
phatics of tendons, 175. Lymphatic glands, 175. Nerves of lymphatic 
nodes, 179. Injection of a lymphatic gland, 179. Method of studying, 179. 
Ranvier’s method, 180. Other methods of injecting glands, 180. Bibli- 
ography, 183. TABLE OF CONTENTS. 
CHAPTER XIII. 
A. MAYER, M.D. 
The Liver and Biliary Apparatus Page 188 
Hepatic lobules, 188. Blood-vessels, 18G. Connective tissue, 188. Liver- 
cells, 189. Larger bile-ducts, 191. Glands of the ducts, 191. Capillary 
bile-ducts, 192. Do the bile-capillaries possess walls ? 196. Gall-bladder, 
197. Lymph-vessels of the liver, 198. Nerves, 199. Bibliography, 199. 
CHAPTER XIY. 
A. MAYER, M.D. 
The Kidney .' Page 201 
General structure, 201. Renal tubules, 203. Their epithelium, 206. The 
loops, 209. Their epithelium, 210. Intercalated portions, 211. Collecting 
tubules, 211. Their epithelium, 211. Blood-vessels of the kidney, 213. In- 
jecting the kidney, 214. Kidney stroma, 215. Nerves, lymphatics, capsule, 
calyx, 216. Natural injection by the sulphindigate of soda, 216. Bibliog- 
raphy, 222. 
CHAPTER XY. 
J. HENRY C. SIMES, M.D. 
Male External and Internal Organs op Generation, with their 
Glandular Appendages Page 223 
Penis, 223. Urethra, 225. Cowper’s glands, 227. Prostate, 227. Testi- 
cles, 229. Tunica vaginalis, 230. Hydatid of Morgagni, 231. Vas defe- 
rens, 232. Seminal vesicles, 235. Bibliography, 238. 
CHAPTER XYI. 
J. HENRY C. SIMES, M.D. 
Female External and Internal Organs op Generation, with their 
Glandular Appendages.—Placenta Page 240 
Labia majora, 240. Labia minora, 240. Clitoris, 240. Vestibule, 241. 
Glands of Bartholine, 241. Hymen, 241. Vagina, 241. Urethra, 242. 
Uterus, 243; Mucous membrane of, 243. Ovula Habothi, 244. Fallopian 
tubes, 246. Ovary, 246. Graafian follicles, 248. Parovarium, 350. Pla- 
centa, 251. Bibliography, 251. XIV 
TABLE OE CONTENTS. 
CHAPTER XYII. 
By BENJAMIN F. WESTBEOOK, M.D. 
The Respiratory Tract Page 253 
Larynx, 153, Ligaments of, 253. Cartilages, 254. Epiglottis, 255. 
Mucous membrane, 255. Trachea and primary bronchi, 257. Smaller bron- 
chi and lungs, 259. Pleura, 265. Lymphatics of, 267. Pleural append- 
ages, 267, Bibliography, 267. 
CHAPTER XYIII. 
The Skin Page 269 
A. R. ROBINSON, M.D. 
General plan of arrangement, 269. Structure, 270. Different layers, 
271. Epidermis, 271. Rete Malpighii, 271. Granular layer, 274. Stratum 
lucidum, 274. Corneous layer, 274. Subcutaneous connective-tissue layer, 
275. Pacinian corpuscles, corium, 277. Blood-vessels, 279. Nerves, 279. 
Tactile corpuscles, 280. Sweat-glands, 282. Muscles, 287. The hair, 288, 
Nails, 293. Bibliography, 295. 
CHAPTER XIX. 
R. W. AMIDON, M.D 
The Central Nervous System .....Page 296 
Spinal dura mater, 296. Spinal arachnoid, 297. Spinal pia mater, 297. 
General histology of the spinal cord, 298. Nerve-elements of the cord, 299. 
Special studies in different portions of the cord, 301. Medulla oblongata, 
307. Olivary body, 310. Cerebellum, 317. Cerebral ganglia, 319. Cere- 
bral ventricles, 319. Cerebral cortex, 321. Structure of cortex, 323. Bib- 
liography, 325. 
CHAPTER XX. 
C. H. WILLIAMS, M.D. 
The Eye Page 328 
Eyelids, 328. Eyelashes, 328. Tarsus, 329. Meibomian glands, 329. 
Conjunctiva, 330. Cornea, 331. Sclera, 337. Vitreous layer, 339. Ciliary 
body, 340. Retina, 343. Lens, 350. Lachrymal gland, 351. Bibliography, 
352. 
CHAPTER XXL 
W. F. WHITNEY, M.D., and CLARENCE J. BLAKE, M.D. 
The Ear Page 353 
External ear, 353. Middle ear, 355. Eustachian tube, 355. Internal 
ear, 357. Membranous labyrinth, 358. Cochlea, 362. Bibliography, 367. TABLE OF CONTENTS. 
PART 111. 
CHAPTER XXII. 
D. BRYSON DELAVAN, M.D. 
The Nasal Fossa:, Pharynx, and Tonsils ...Page 368 
Vestibulum nasi, 368. Respiratory region, 368. Olfactory region, 370. 
Olfactory nerves, 372. Bowman’s glands, 372. Pharynx, 373. Tonsils, 
373. Bibliography, 375. 
CHAPTER XXIII. 
D. BRYSON DELAYAN, M.D. 
The Mouth and Tongue Page 377 
Tunica propria, 377. Blood-vessels, 379. Lymphatics, 379. The tongue, 
380. Papillae, 380. Taste-goblets, 381, Bibliography, 384, 
CHAPTER XXIY. 
EDMUND 0. WENDT, M.D. 
The Alimentary Canal Page 386 
(Esophagus, 386. Stomach, 388. Small intestine, 394. Large intestine, 
400. Rectum, 401. Bibliography, 402. 
CHAPTER XXY. 
C. L. DANA, M.D. 
The Spleen, Pancreas, Thymus, Thyroid, and Pineal Glands, and 
Pituitary Body Page 403 
The spleen—coats, 403, 404. Malpighian corpuscles, 404. Pulp, 406. 
Blood-vessels, 407. Lymphatics, 409. Nerves, 409. Development, 409. 
Pancreas—excretory duct, 411. Blood-vessels, 411. Lymphatics, 411. 
Nerves, 411. Development, 411. Thymus gland, 412. Capsule, 412. Fol- 
licles, 412. Central canal, 414. Blood-vessels, lymphatics, development, 414. 
Thyroid body, 415. Blood-vessels, 416. Lymphatics, 416. Nerves, 416. 
Pineal gland, 417. Pituitary body, 417. Bibliography, 418. XVI 
TABLE OF CONTENTS. 
CHAPTEE XXYI. 
By J. COLLINS WARREN, M.D. 
The Thick Cutis Vera Page 420 
Fat-columns, 421. Blood-vessels, 423. Lymphatics, 424, 
CHAPTER XXYII. 
EDMUND 0. WENDT, M.D. 
Urinary Excretory Passages.—Suprarenal Capsules Page 428 
Renal pelvis, 428. Ureters, 429. Bladder, 430. Suprarenal capsules, 
431. Bibliography, 437. 
CHAPTER XXYIII. 
W. H. PORTER, M.D., and E. C. WENDT, M.D. 
Mammary Gland Page 439 
General considerations, 439. Nipple, 440. Galactophorous ducts, 441. 
Milk reservoirs, 441. Areola mammas, 442. Arteries, 442. Lymphatics, 
443. Nerves, 443. Structure of expanded gland, 444. Of involuted gland, 
446. Rauber’s views, 450. Corpuscles of Donne, 450. Milk, 451. Devel- 
opment, 452. Plan of histological study, 455. Bibliography, 456. 
APPENDIX A. 
The Lymphatic System Page 459 
W. R. BIRDSALL, M.D. 
Views of G. and F. E. Hoggan, 459. New methods of demonstrating the 
lymphatics, 459. Bibliography, 460. 
APPENDIX B. 
The Salivary Glands Page 461 
EDMUND C. WENDT, M.D. 
General remarks, 461. The acini, 462. The secreting cells, 463. 1. 
Albuminous glands, 463. 2. The mucous glands, 464. Excretory ducts, 466. 
Blood-vessels and lymphatics, 467. Nerves, 467. Intra-alveolar Reticu- 
lum, 468. Bibliography, 469. A 
MANUAL OF HISTOLOGY 
AND 
HISTOLOGICAL METHODS. 
CHAPTER I. 
MATERIALS REQUISITE FOR HISTOLOGICAL WORK—HOW TO USE 
THE MICROSCOPE—TESTING THE MICROSCOPE—ITS USES. 
Very little apparatus and few reagents are essential for gen- 
eral histological work. Such as are really needed may be so 
arranged as to fit in a box or bag, that can be carried in the 
hand. First of all, the student should be provided with a 
. Fig. 2, 
Fig. 1 
Fig. 3.—Curved Iris Scissors. 
pair of small forceps, with either curved or straight points 
(Figs. 1, 2), according to individual fancy ; a pair of delicate 
cur red iris scissors (Fig. 3); a. few pipettes; a glass rod or 2 
MANUAL OF HISTOLOGY. 
two ; a spoon (Fig. 4) for lifting sections of tissues from the 
fluids in which they have been immersed ; a pair of needles 
(Fig. 5) in handles for teasing or tearing tissues ; (the handles 
used for crochet needles, or the pin-slides sold by jewelers, 
may be fitted with ordinary milliner’s needles, which are long, 
delicate, and flexible, and therefore well adapted for this 
Fig. 4. 
Fig. 5.—Microscopic Needle-holder. 
Fig. ti.—ijicroscopic Section Razor. 
Fig. T.—Capped Bottle. 
work) a sable or cameVs hair brush for removing cellular 
elements, so as to bring particular parts into prominence ; bibu- 
lous paper ; a sharp Jcnife (Fig. 6) for cutting thin sections ;1 
1 For this purpose the razors made by Le Coultre, in Geneva, have been highly 
recommended, but good knives may be obtained of almost any cutler ; indeed, most 
of the makers of surgical instruments furnish them ; they are usually flat on one 
side and slightly concave on the other. MATERIALS REQUISITE FOR HISTOLOGICAL WORK. 
five or six shallow 'porcelain dishes, ounce gallipots, with, flat 
bottoms, in which to soak the tissues when they have been cut; 
glass slides for mounting specimens (the ordinary size is 8 x 1 
inch) ; thin glass or mica covers (squares or circles) for cover- 
ing the specimens (three-quarters of an inch is a good diameter). 
Mica'covers are much cheaper than glass, and are suitable for rapid work 
and when it is not desirable to make permanent preparations. 
Fig. 8.—Beer’s Cataract Knife. 
In addition, a small Beeds cataract Tcnife (Fig. 8) will be 
found useful for puncturing vessels and hollow organs to obtain 
samples of their fluid contents. All of these articles may easily 
be contained in the drawer of a box 10 xl 2 inches in size ;1 the 
upper portion will hold the necessary reagents. These latter 
should comprise a small amount of a three-fourths per cent, 
aqueous solution of sodium chloride, about an equal amount 
of distilled water, dilute acetic acid, glycerine, and iodized se- 
rum;2 a fluid ounce of each will be all that is necessary, and 
for convenience of use they may be put in corked bottles pro- 
vided with capped pipettes passing through the corks. The 
vials and perforated corks may be obtained of almost any 
apothecary. The cap being of rubber, very small quantities 
of the fluid can be withdrawn from the bottle and pressed out 
as desired, either upon the slide or otherwise. 
Other reagents required are oil of cloves in a two-ounce 
stoppered bottle ; dammar varnish or Canada balsam, eacli in 
a capped bottle (Fig. 7), containing a glass rod ; a solution of 
logwood, and another of borax carmine,3 in ordinary glass 
stoppered two-ounce bottles, and a small vial of asphalt or 
some similar cement. It will be useful, in addition, to have a 
small bottle (4 oz.) of absolute alcohol, another (8 oz.) of com- 
mercial alcohol, some Muller’s fluid3 (8 oz.), and a solution of 
the bichromate of potassium (gr. xv.— | j.). 
1 T. H. McAllister, optician, No. 49 Nassau Street, New York City, has made one 
for me which answers the purpose satisfactorily. Miller Bros., No. 69 Nassau Street 
and 1218 Broadway, New York City, also make and furnish cases for the same 
purpose. 
2 See page 88. 
3 See page 14. 4 
MANUAL OF HISTOLOGY. 
Ho good histological work can be done without a note-hook 
to record the results of observation. All such memoranda will 
be very useful for subsequent reference. A heating slide, a 
gas chamber and a slide arranged for conducting electric cur- 
rents may also be desirable. They will be described in the 
chapter on the Blood. 
The following substances that cannot be contained in a box, 
and are necessary in some forms of microscopic work, may be 
mentioned: osmic acid (1 percent.), nitric acid (C. P.), distilled 
water, olive oil, caustic soda or potash, chloride of gold (£ per 
cent, sol.).1 
It is also very convenient to have at hand a short wooden 
rule which is divided into inches and tenths of an inch. The 
stage micrometer is also equally necessary. Other accessory 
materials will be described in their proper places. 
HOW TO USE THE MICROSCOPE.2 
Illumination.—When the instrument is ready for use it 
should be placed upon a firm and rather low table, near a 
window, which does not receive the direct rays of the sun. If 
daylight is not to be obtained, a small kerosene hand-lamp will 
answer sufficiently well for illuminating purposes. The flame 
should be on a level with the reflecting mirror of the micro- 
scope, and quite near it. Sometimes a condenser is interposed, 
but this is rarely necessary, and, indeed, it may be said that it 
seldom comes into use in histological work. 
A thin sheet of blue glass may sometimes be found to assist 
the eye when artificial illumination is used, as the light is made 
white. Some microscope makers furnish with their instru- 
ments a set of blue glasses varying in color from very light to 
dark blue. They are rarely needed, as the eye soon becomes 
accustomed to continuous work for long sittings, even when 
strong light is employed. Those who work much with the 
microscope keep both eyes open, and use first one and then 
1 See pages 28, 29. 
2 It is presumed that students engaging in histological work are more or less 
familiar with the mechanism of the microscope. For this reason the subject of 
optical principles and the description of the different parts of a microscope are 
omitted here. Those who may wish special information on these points are re- 
ferred to the standard text books on Physics. HOW TO USE THE MICEOSCOPE. 
the other. Some find it a great assistance to direct the un- 
engaged eye upon a dark object, such as a blackened card, 
which they fasten to the tube of the instrument near its top. 
As it is desirable that the lamp should only illuminate the 
refiector, a great many ingenious contrivances have been made 
to cut off the superfluous light. For this purpose some micros- 
copists interpose a piece of thin board, or a thick card, having 
a circular opening between the lamp and the reflector. 
Stage diaphragms.—When the pencil of light has been 
reflected from the mirror upon the opening in the stage, it is 
plain that a larger or smaller amount of light will pass, accord- 
ing to the size of the opening. The appliances that regulate 
this matter are called stage diaphragms—sometimes they are 
simply cylindrical tubes with capped upper extremities, each 
tube being provided with caps of varying aperture. The tubes 
are pushed into the stage from beneath. When polished they 
undoubtedly aid in converging the light upon the aperture. 
Other diaphragms are simply round holes in a circular revolving 
plate which is set into the stage. 
The diameters of the apertures vary from that of a pin’s 
point to about three-fourths of an inch or even more. 
The revolving diaphragms have now come into general use, 
because they work simply and efficiently. Mr. AVale has de- 
vised one that is extremely ingenious. It has the advantage 
of a cylindrical diaphragm, in so far as it converges the pencil 
of light upon the diaphragmatic opening, while the size of the 
opening is regulated by the action of a single thumb-screw.1 
It acts as the iris does in enlarging or diminishing the pupil, 
and therefore its name, the iris diaphragm. 
The mirrors.—Of these there should be two, one plane, 
when a diffuse light is needed ; the other concave for a concen- 
trated beam. The latter is frequently used, the former seldom. 
Direct and oblique light.—Thus far the descriptions have 
applied to direct light, and it is the only kind much used in 
histological work. In testing a lens, however, as with a diatom, 
it is often necessary to use oblique light in order to resolve a 
line or series of lines. In such cases the aperture in the stage 
should be made as large as possible, and the mirror, concave or 
plane, is to be carried well up under the stage, to the left or 
1 See illustrated catalogues of leading microscope makers. 6 
MANUAL OF HISTOLOGY. 
right, so that the pencil of light may be thrown across the 
object. By this means, little inequalities of the surface which 
would be invisible under direct light are clearly demonstrated. 
The poorer lenses, however, are those which necessitate oblique 
light. When reference is made to the definition of the lens, 
direct light is intended. 
Arrangement of the object.—When the object is to be ex- 
amined, it should be placed upon the glass slide, which is usu- 
ally one by three inches in superficial measurement, and as 
thin as is compatible with the usages to which it is put in 
ordinary microscopic work. The glass should be white in color, 
and free from any imperfections that can be detected by the eye. 
Usually a drop or two of water, a drop of glycerine, or a drop 
of water and glycerine in equal parts, is placed upon the slide. 
The object is then immersed in the liquid. It takes some 
little time for the fluid to permeate the specimen, so that it is 
ready for study. When pure glycerine is used fully ten minutes 
will generally elapse before the specimen is transparent. A 
covering glass is then cautiously let fall upon the liquid, care 
being taken that no bubble of air enters. The cover is then 
pressed down. In such cases, when the object is studied with 
high powers, the cover will often slowly rise and separate itself 
from the slide, so that the forceps or the finger may be neces- 
sary to press it back. This inconvenience is obviated by paint- 
ing a little Canada balsam or cement around the edge of the 
cover so as to hold it down. 
The hind of a lens to be used.—For the first examination a 
low objective should be used, with a medium, not short, eye- 
piece. The tube should then be carried down until the object 
comes within the focus. Low powers should always be used 
at first, because they give a good idea of the object in its gen- 
eral features. 
Then the tube may be withdrawn, and a higher power sub- 
stituted, and so on, until the specimen has been studied in all 
its details. A convenient accessory is now made by most of 
the instrument makers; it is a “nose-piece”—a brass attach- 
ment which is screwed into the end of the tube, and carries two 
or more lenses.1 
1 The double angular nose-piece made by Schrauer, 46 Nassau Street, costs $6, 
the triple, $2O ; all of the microscope makers are now prepared to furnish them. TESTING THE MICROSCOPE ITS USES. 
The first named is usually fitted with a f and a } inch lens ; 
in addition to these aTV immersion may be used for the triple 
nose-piece. 
How to keep the instrument clean.—After using the instru- 
ment it should always be wiped dry, as it is damp from the 
moisture of the breath and hands. The lenses should be re- 
turned to their cases, and, if necessary, the surfaces are to be 
rubbed off with a bit of soft chamois skin or fine linen. Water 
will remove almost all the dirt from the anterior lens, but occa- 
sionally it may be necessary to use alcohol. In such cases but 
very little is requisite, as it may penetrate behind the anterior 
lens and dissolve the Canada balsam that cements the different 
portions together. 
It is well for the student to familiarize himself at first with 
certain common objects that are apt to be met with in all 
forms of microscopic work, such as the little foreign substances 
that go to make up the dust of rooms; these include minute 
bits of wood, cotton and linen fibres, particles of wool, hairs of 
various animals, feathers, etc. 
The imperfections in the glass should also be noted, and 
especially the curious red figures sometimes resembling butter- 
fly wings, caused by an accumulation in the flaws of the glass 
of a red substance—the red oxide of iron—used by manufac- 
turers in polishing glass. These red figures are often wonder- 
fully alike, and have given rise to singular errors among micro- 
scopical workers. 
TESTING THE MICROSCOPE—ITS USES. 
Magnifying power of a lens.—To determine the actual 
magnifying power of a lens in combination with the particular 
eye-piece that happens to be in use, the ordinary method is as 
follows : 
The glass stage micrometer, which is ruled off into tenths, 
hundredths, and thousandths of an inch, is placed upon the 
stage and focussed. This having been done, the wooden rule, 
which we have already alluded to and which is divided into 
inches and tenths of an inch, is laid alongside of the micro- 
meter-slide. 
One eye, looking outside of the tube, reads off the number 8 
MANUAL OF HISTOLOGY. 
of divisions of the wooden rule corresponding to a single divi- 
sion of the micrometer slide as seen with the other eye directed 
through the tube of the microscope. 
By this method of double vision, as it were, a comparison is 
instituted between the two rules, and the ratio that one bears 
to the other may be estimated. 
Suppose, for example, that oho of an inch on the scale of the 
stage micrometer is equal to TV of an inch on the wooden rule. 
The ratio of ToVo to T\ will represent the magnifying power 
of that particular combination. Reducing these fractions to 
a common denominator they stand to one another as 1 to 200. 
The object has therefore been magnified two hundred times. 
With a short eye-piece the power is greater and it increases 
in proportion as the tube is drawn out. It is customary how 
ever to assume a certain length of the draw-tube as the stand- 
ard : this is twenty-five centimetres or about ten inches. 
How to estimate the size of an object.—To estimate the size 
of an object is a much easier task. Place the stage micrometer 
upon the stage of the microscope and then slip the micrometer 
eye-piece into the draw-tube. The micrometer eye-piece is 
simply an ordinary ocular with a glass cover fitted into the 
diaphragm. The micrometer consists of a series of parallel 
lines ruled across it at regular distances apart. By focussing 
the lines on the stage micrometer one may readily count the 
actual fractions of an inch corresponding to a single division 
in the micrometer eye-piece. 
Thus, for example, if we find that a single division of the 
micrometer eye-piece corresponds to ToVo of an inch, and that 
a lymphoid corpuscle covers half a division, its diameter is 
necessarily of an inch. 
Testing a lens.—A lens should be free from certain defects, 
as we have already stated. First of all it should have no 
spherical aberration ; the objects seen upon the edge of the 
field should be sharply defined, and all objects having parallel 
sides should appear as such. In other words, they should not 
be distorted. 
Secondly, they should have no color or, at least, as little 
as possible. This defect, however, has never been entirely 
overcome ; some glasses are over-corrected and then the pre- 
vailing color is blue ; others are under-corrected and then the 
prevailing color is red. TESTING THE MICROSCOPE—ITS USES. 
It is a matter of some indifference which color prevails. 
These defects are best seen by observing a bubble of air in a 
fluid specimen. The prevailing color is seen at the periphery 
of the bubble. 
Thirdly, all objects in the field should appear with equal 
distinctness, whether at the periphery or in the centre. If a 
fine powder, such as lycopodium be strewn over the field, the 
granules should be seen as distinctly at the edges as at the 
centre ; an ordinary thin section of any microscopic object will 
also exhibit this defect, if it exist. 
Fourthly, the glasses should have good resolution. This 
enables the observer to see the general aspect of bodies better, 
though it may not make him see objects quite as sharply ; the 
former depending upon a large angle of aperture, and the latter 
(definition) upon a small one. 
To be able to have at the same time both great resolving 
and great defining power is the highest desideratum, and it has 
been the merit of our American makers to increase the angle 
of aperture and still maintain a high defining power. 
For ordinary histological purposes, a lens that will show 
the oscillatory movement in the raucous or salivary corpuscles 
is sufficiently high for practical purposes. This is accomplished 
by the ordinary student’s one-fifth of Grunow, for example. 
If, however, we are studying the delicate intercellular sub- 
stance of the brain and connective-tissue corpuscles, bacteria, 
etc., a somewhat higher power is needed. 
For such studies it is desirable to have an immersion lens, such as the No. 10 
or 12 Hartnack or Prazmowski, or a A or -^s of other good makers, such as 
Wale, Tolies, etc. 
In using these high powers it is necessary to place a single drop of water 
on the anterior lens and depress the tube until the drop touches the circle 
or cover. The drop of water utilizes light that would otherwise be lost, mag- 
nifies slightly, and corrects, so that the image is made brighter and more 
distinct. 
The new oil immersion of Zeiss is highly recommended by Woodward of 
Washington. In using such a lens, a drop of oil is substituted for water. We 
are hardly yet prepared to decide whether oil is preferable on the whole to 
"water. 
How to illuminate the microscope.—ln doing ordinary 
microscopic work it is best to use day-light, such as is reflected 
from a clear sky. It is not well to use direct sun-light, but to 10 
MANUAL OF HISTOLOGY. 
receive illumination from a point opposite to the sun. North 
light is very excellent. 
If artificial light is to be used, an ordinary kerosene burner 
will answer sufficiently well, even better than gas. Some of 
the highest lenses require artificial light. 
Testing the eye-piece.—Eye-pieces are usually free from 
serious defects, but if we are desirous of testing one, the fol- 
lowing method may be followed : 
Select a combination of lens and eye-piece that gives a per- 
fectly flat field. Then remove the eye-piece and -substitute the 
one that is to be tested. If now the image is no longer flat, 
the eye-piece has aberration of form and should be rejected. 
Testing high lenses.—In combinations that magnify about 
five hundred times, a good test is the pleurosigma angulatum, 
one of the diatoms. A lens that will demonstrate three sets of 
lines by direct light has a proper amount of defining power, 
and with the other qualifications already mentioned, is suit- 
able for the finer sorts of microscopical work. This task is 
easily accomplished by either the No. 10 immersion of Hart- 
nack or Prazmowski, the XV of Wale, and also by lenses of other 
good makers. 
To test the resolving power of lenses even more accurately, 
Nobert’s test plates may be used. They consist of bands of 
fine lines from nineteen to thirty in number. 
It has usually been thought that the eighth or ninth of 
their series is a good test; the nineteenth band,1 however, has 
been defined by a ten immersion Ilartnack, and probably by a 
goodly number of American lenses. (See Appendix.) 
Measuring the angle of a lens.—Take an instrument of 
which the pillar is hinged, and which also revolves on its ver- 
tical axis. 
Measure off on the table, in front of the instrument, a semi- 
circle with the pillar as a fixed point. Divide the semicircle 
into the proper number of degrees, viz., 180. 
Place opposite the instrument, and without the circle, a 
candle or lamp. Then interpose between the two a screen hav- 
ing an aperture to admit a small beam of light. Revolve the 
tube on its axis until the light can no longer be seen ; then 
1 According to Carpenter, the nineteenth band contains 113,595.13580 spaces to 
the inch. TESTING THE MICROSCOPE ITS USES. 
count off the number of degrees which the instrument has 
passed over. Suppose, that, in a given case, the number be 
seventy ; then revolve the instrument in the opposite direction 
and count as before. The number of degrees will of course be 
the same. 
Add the two figures together, and the total number of de- 
grees (viz., 140) will represent the angle of aperture. CHAPTER 11. 
METHODS FOR PREPARING MICROSCOPIC OBJECTS. 
General directions.—Microscopic work should be done at a 
rather low table, not more than thirty inches high, and resting 
squarely upon the door, so that it cannot be jarred by move- 
ments in the room. In most laboratories small and short mi- 
croscopes are preferred ; they are now made by nearly every 
optician. The total height, when the stand is vertical, need 
not be more than eleven or twelve inches. For various reasons, 
which soon become apparent to those who do much histological 
work, it is seldom necessary to provide the stand with a hinge- 
joint, which allows the tube to be inclined toward the observer. 
A vertical and rigid stand is steadier, less expensive, and, ex- 
cept in very rare instances, all that is required in medical work. 
When the microscopist is about to commence his examina- 
tion, he should select the various materials that are likely to 
be needed, and place them near him on the table, so as to be 
within easy reach of his hand. Special tables for microscopic 
work may be provided with rows of drawers upon either side 
of the worker. In them should be kept all the microscopic 
accessories that he expects to use, such as glass slides and 
covers, wooden boxes for specimens, labels, a note-book for 
rough sketches and annotations, a bit of chamois skin for 
cleaning the lenses and other adjuvants which are found useful. 
By so doing, these materials are kept free from dust, and stand 
ready for use at any time. A small vessel holding clean water 
to wash the covers and slides, a receptacle of some kind for 
the waste, and a clean, fine, and soft towel should not be for- 
gotten, as they are always useful for every kind of microscopic 
work. 
The instrument is best kept under a bell-glass on the table. 
If, however, it has to be taken about from place to place, it METHODS FOR PREPARING MICROSCOPIC OBJECTS. 
should be packed in its box, and the accessories may also be 
kept in a suitable chest, such as has been described, and which 
is made by a number of opticians. 
After the directions that have been given, it seems hardly 
necessary to add that everything pertaining to the work should 
be carefully cleansed after using, and put away in its proper 
place, so as to be immediately available at any future time. 
The expenditure of a little time in these details is more than 
counterbalanced by the greater rapidity and effectiveness of 
subsequent work. 
How to prepare afresh microscopic object for rapid exam- 
ination.—-When practicable, every specimen should be studied 
as early as possible after removal from the body, and this is 
important even if it is to be hardened and prepared for per- 
manent preservation. 
Take a clean slide, which, of course, should be reasonably 
thin ; place it before you upon a white ground (some micro- 
scopists have a square plate of marble set into the table); mois- 
ten the slide with a drop of some indifferent fluid, such as 
iodized serum or, perhaps, a three-fourths per cent, aqueous 
solution of common salt; then place in the drop the fragment 
to be examined. Small particles are more easily studied than 
large ones. Usually the substance should be spread out a 
little with needles. 
In one or two minutes it is ready for examination. By this 
method striped muscular tissue may easily be detected ; and it 
also happens to be a good example because it is very frequently 
brought to microscopists for examination. In certain forms of 
dyspepsia, especially in women, it is common for ingested 
meat to pass through the alimentary tract with very little 
change. Prepared for the microscope in this simple way the 
peculiar markings of striped muscle may be observed at once, 
and even if the meat has been boiled. 
If, however, the material to be examined is opaque, we add 
to the drop of serum another of glycerine ; the latter alone re- 
fracts the light too much, and is therefore undesirable. When, 
however, it is combined with an equal amount of serum or the 
salt solution, the fluid has a proper refractive power for most 
histological purposes. The microscopist should now let fall 
upon the drop a cover glass, and place the slide upon the stage 
of the microscope. Nothing is required to keep the cover in 14 
MANUAL OF HISTOLOGY. 
place. Examine at first with a low power, and then with a 
higher one, nntil the specimen has been studied in all its 
details. 
THE ORDINARY METHODS OF PREPARING TISSUES. 
Muller*sfluid.—It is customary to use Muller’s fluid to 
render tissues firm, so that they may be easily cut with the 
knife, and made thin enough for microscopic studies. The for- 
mula is (by weight) bichromate of potassium, 2 parts, sulphate 
of soda, 1 part, distilled water, 100 parts. This fluid, which 
is of a brown color and transparent, is admirably adapted for 
hardening and preserving permanently nearly all the tissues of 
the body ; though for the brain and cord it is unsatisfactory 
without the subsequent use of other reagents. It is, however, 
very cheap, and specimens may be preserved in it for years, 
and still retain the characteristics which make them suitable 
for microscopic study. 
Potassium bichromate solution.—Some microscopists prefer 
simply a solution of the bichromate of potassium (gr. xv.— 3 j.). 
It is well, in this case, to put the specimens into a fresh solution 
every day for several days. Subsequently they are to be hard- 
ened in alcohol. The strength of the latter should at first be 
eighty per cent., then ninety per cent., and finally may be 
ninety-five per cent. The alcoholic process requires a few ad- 
ditional days. Solutions containing chromic acid or the bi- 
chromates are objectionable if the specimen is to be used for 
coarse demonstration, because the yellow or brown color of the 
acids is difficult to remove. Prolonged soaking in distilled 
water will accomplish a great deal, but the final color is gener- 
ally a clay brown. Of course this objection does not apply to 
microscopic sections, and indeed it appears as if the chromic 
acid and chromate solutions prepare them particularly well for 
the process of staining in various colors. 
Ammonia bichromate solution.—Gerlach has recommended 
this reagent in one or two per cent, solutions for hardening the 
brain and cord. It is to be used as the preceding (Prey). 
Alcohol and acetic acid mixture (Lockhart Clarke).—Two 
objects were sought by their combination: one to coagulate 
albuminous matters by the alcohol, the other to render them 
transparent. The proportion was alcohol three parts and THE ORDINARY METHODS OF PREPARING TISSUES. 
acetic acid one part. It is said that by this method sections of 
the cord may be made transparent in a few hours (Frey). 
Alcohol and acetic acid mixture (Moleschott).—This ‘£ strong 
acetic acid mixture,” of which the formula is strong acetic acid 
(1.070 sp. gr.), 1 vol.; alcohol (.815 sp. gr,), 1 vol.; distilled 
water, 2 vols., causes the connective-tissue substances to be- 
come very transparent. Delicate textures do not tolerate it 
well (Frey). 
Molybdate of ammonia has been recommended by Krause 
for hardening specimens. It has met with some favor. 
Solution of osmic and chromic acids.—Flesch recommends 
a union of these acids for hardening and decalcifying bone. 
It is also useful for hardening other tissues. His formula is 
as follows : osmic acid, 10 parts; chromic acid, 25 ; distilled wa- 
ter, 100. 
Alcohol and acetic acid and muriatic acid solution.— 
Beale gives the following formula: water, 1 oz.; glycerine, 1 
oz.; spirit, 2 oz.; acetic acid, 2 drachms; hydrochloric acid, 
i drachm. This is said to harden well and be suited for epithe- 
lial structures (Frey). 
Method of hardening the brain.—Hamilton recommends 
the following method: pieces of brain and cord cut into sec- 
tions not more than an inch in length, or length and breadth, 
are immersed in a fluid containing three parts of Muller’s fluid 
and one of methyl alcohol, and put away for some three weeks 
in a refrigerator. Then they are to be soaked in a solution of 
the bichromate of ammonia (1-400) for a week ; another week 
in a solution of 1-100 ; a third week in a solution of 1 to 50 ; 
and finally kept in chloral hydrate (12 gr. to the ounce). Be- 
fore cutting, they are to be washed twelve hours or more in 
water; they then are to stand forty-eight hours in a syrup 
containing two parts of refined sugar to one of water. He then 
cuts with Rutherford’s microtome. Staining is done with 
osmic acid and carmine. 
How to embed specimens.—When a piece of tissue is so 
small that it cannot be held in the hand, it is customary to 
embed it in some substance of about the same consistence. A 
combination of wax and oil answers the purpose very well; 
they should be mixed in about equal proportions in a porce- 
lain dish, and then heated together until the wax is thoroughly 
For clarification he uses oil of cloves or turpentine. 16 
MANUAL OF HISTOLOGY. 
melted. This having been done, a mould should be at hand to 
receive both the embedding mixture and the piece of tissue. 
Various moulds are in use. Some are made of tin-foil, and are 
shaped like a common earthenware garden-pot. 
A line, long cambric needle should be passed through the tis- 
sue,and then (the mould being placed in position) the point of the 
needle is to be pushed through the bottom into the table beneath. 
Then the mixture of the liquid wax and oil, which has been 
heated to the point of melting and no more, should be poured 
slowly into the mould, so as to slightly cover the specimen. 
During the process of hardening, minute bubbles of air will be 
liberated from the tissue ; they will escape more rapidly, and 
the embedding material will harden more quickly and thor- 
oughly, if the microscopist blows gently and continuously on 
the surface of the liquid. Just at the moment when the mass 
is no longer liquid, the needle should be suddenly withdrawn. 
As soon as it is hard throughout, the tin-foil mould may be 
torn off by breaking the edge at any point with the finger. 
The foil tears like paper. 
When moulds are not at hand, an excellent substitute may 
be made with ordinary writing paper. Some confectioners 
make them of pressed paper. 
Embedding in glycerine and tragacanfh.—Mr. John Ste- 
venson’s plan is as follows : He takes two drachms of glyce- 
rine and mixes them with one drachm and a half of powdered 
gum tragacanth. The tissue to be cut is then placed in a small 
pill-box, and the mixture poured in. The box is then laid 
away in a cool place from eight to twelve hours, when sections 
may be made with the knife. In case the specimen is to be 
preserved for a longer time, the bottom of the box may be 
taken off, and the side slit up. The specimen will now be 
found embedded in a solid elastic cake, and may be slipped 
into alcohol until required. When it is to be kept in spirits 
less than twenty-eight hours, the mixture should be glycerine, 
2 drachms ; powdered tragacanth, 1 drachm; gum arabic, 15 
grains. Tissues that have lain in spirit should be steeped in 
cold water a few hours before embedding. 
The hand section-cutter is used by some microscopists. It 
is simply a cylinder which is designed to receive the object 
and the material in which it is embedded. A plunger, which 
is driven up from beneath by the revolution of a screw, pushes THE OEDINAET METHODS OF PEEPAEING TISSUES. 
np the specimen so that it may be sliced off by an ordinary 
knife. For some purposes it is very useful. 
Freezing section-cutters.—Of these there are many in use, 
and they have certain advantages. In conjunction with Dr. 
J. H. Hunt, of Brooklyn, I have devised a modification of the 
ordinary instrument.1 (Fig. 9.) 
I'm. 9.—Freezing section-cutter: B, metallic box ; S, cylinder; a, well; c, c, frame for holding Icnlfe 
A, A; G, indicator; D, milled head; P, P, plugs; E, B, tubes to fit in well; H, H, covers to metallic 
box; K, binding screw attaching box to table. 
It consists of the brass cylinder, S, made of rather large 
size, and placed in the centre of a metallic box, B. The 
length of the cylinder, with driver, D, is about five inches. The 
diameter of the well, a, measures If inch. Fitted round and 
about the cylinder is a plate of glass which from its smooth- 
ness permits the knife to sweep it easily. 
The knife, A, A, is large, measuring 18 inches in length, in- 
cluding handle ; in breadth, If inch. It is fitted into a brass 
frame, c, c, inches in length and 3f in breadth. Two strong 
brass springs, and two sliding clamps, hold it in place. The 
knife is slightly concave on both sides. 
The well is so large that it will hold an ordinary kidney 
after hardening, or at least so much of it that a transverse sec- 
1 Made by Miller Bros., 1213 Broadway, New York city. 
2 18 
MANUAL OF HISTOLOGY. 
tion may be made of the whole organ at one sweep of the knife. 
The knife and frame are modifications of those devised by Dr. E. 
Curtis of this city, and the section-cutter and box are not dif- 
ferent in any essential particulars from those in common use. 
They are larger, however, and the indicator, Gr, enables the 
observer to determine with accuracy the thickness of his sec- 
tions. Thus, in my own instrument thirty-one turns of the 
milled head drives the plug forward one inch. 
Each revolution consequently drives the specimen forward 
■jy inch. Now, the circumference of the milled head is marked 
off into thirty divisions. 
When the indicator marks that the plug has been driven 
forward one division, the distance traversed will be inch. 
It is easy, therefore, to determine the thickness of any sec- 
tion with considerable accuracy. 
When it is desirable to put the instrument in use, the 
plug that is to be used is well oiled, as also the thread of the 
driver, and the metallic box is filled with a mixture of ice and 
snow. 
It is necessary to be particular and oil the bearings 
thoroughly, else they will bind and the instrument will be 
clogged while the freezing process is going on. The usual 
plan is to soak the tissue (as Dr, Pritchard suggests) in a 
thick solution of gum, which cuts like cheese when frozen. 
The soaking should continue for a number of hours, say until 
the next day. 
When the tissue is ready, a thick solution of the gum 
should be poured into the well and the tissue held until it is 
fixed by the ice. Some non-conductor is to be placed over 
the well as soon as fixation has commenced, in order that ac- 
cess of heat may be prevented. 
If ice is used it should be ground up finely and then packed 
tightly about the well; snow is better. The whole process 
takes only ten or fifteen minutes. The freezing section-cutter 
is of use when wTe are desirous of making a rapid examination 
of fresh tissues. 
It is obvious that they are seen under more natural circum- 
stances than when they have passed through the bichromate i 
or chromic acid solutions, or alcohol, all of which cause more 
or less change in such delicate substances. 
It has been hoped that by the freezing method we should THE ORDINARY METHODS OF TISSUES. 
learn mucli that is new about the finer structures of the brain 
and the character of the corpuscular elements of the body, but 
as yet it has not reached our expectations. 
Hailes's microtome.—A very ingenious and excellent instru- 
ment (Fig, 10) has been devised by Dr. William Hailes, Pro- 
fessor of Histology and Pathological Anatomy at the Albany 
Medical College. Objections to it will be mainly on the ground 
of price. 
Dr. Hailes uses it as a simple instrument or as a freez- 
ing microtome, arranged either for ice and salt, ether-spray, 
rhigoline, etc. 
The employment of ice and salt (coarse) is preferred, be- 
cause it costs but little and freezes the mass solidly and 
quickly, and, if desired, 500 or 1,000 sections can be obtained 
in a few moments, depending, of course, upon the rapidity 
and skill of the operator. 
The time of freezing is about seven minutes, except in 
very warm weather, when it requires a few moments longer. 
The instrument does not work quite so satisfactorily in very 
warm weather, owing to the rapid melting at the surface of the 
preparation. 
It is absolutely necessary that the mass should be frozen 
solid, or the sections cannot be cut smoothly. 
An extra freezer may be employed, and while one specimen 
is being cut the other is being frozen ; by exchanging cylinders 
(they being interchangeable) no delay is necessary. 
The art of cutting is readily acquired. Two hundred or 
two hundred and fifty sections have been made in a minute, 
and of a uniform thickness of Wot °f an kick. It is not 
necessary to remove the sections from the knife each time, 
but twenty or thirty may be permitted to collect upon the 
blade. They lie curled or folded up upon the knife, and when 
placed in water, straighten themselves out perfectly in the 
course of a few hours. The knife employed is an ordinary 
long knife from an amputating case. 
Perfectly fresh tissues may be cut without any previous 
preparation, using ordinary mucilage (acacia) to freeze in, but 
most specimens require special preparation. 
If preserved in Muller’s fluid, alcohol, etc., they require to 
be washed thoroughly for several hours, and then, according 
to the suggestion of Dr. David J. Hamilton, F.R.C.S., etc., of 20 
MANUAL OF HISTOLOGY. 
tlie University of Edinburgh, Scotland, the specimen is placed in 
a strong syrup (sugar, two ounces ; water, one ounce) for twenty- 
four hours; it is then removed to ordinary mucilage for forty- 
eight hours, and finally is cut in the freezing microtome. 
These sections may be kept indefinitely in a preservative 
Fig. 10.—Poly-microtome (without freezing apparatus); A, small well fitting on pyramidal bed-plate • 
B, pyramidal bed-plate containing different sizes; C, micrometer screw; D, ratchet-wheel attached to 
screw ; E, lever actuating the micrometer screw by means of a pawl engaging in teeth of ratchet-wheel; 
P, arm carrying a dog, which prevents back motion of screw; Gr, regulator for limiting the throw of 
lever, and consequently governing the micrometer screw; H, lever-nut for fixing regulator; I, index, with 
pointer and graduated scale, from 1/2400 inch to 1/200 inch ; K, knife for cutting sections ; L, knob to 
turn micrometer screw direct when pawls are detached; M, table clamp; T, table of microtome, with 
glass top to facilitate cutting. 
Pig. 11.—(Very much reduced in size). A, B, tube containing specimen which is surrounded by freez- 
ing mixture in tin receiver C, D ; E, P, revolving hopper with wings, W, W, for stirring the ice ; G-, out- 
let for melted ice. 
fluid recommended by Dr. Hamilton: IJ. Glycerin., aquae 
destil., aa. |iv. ; acid, carbolic., gtt. iij. Boil and filter. The 
addition of alcohol, | ij., is advisable. STAINING FLUIDS. 
The Vincent microtome.—This instrument, which was de- 
vised by Dr. Vincent, of New York city, is a flat piece of steel 
(Fig. 12) 12 inches long by 2—2 i inches wide, with a bevelled 
cutting edge, 6 inches long. The handle is simply the rounded 
and smoothed extremity of the knife. 
It has been in use at the School of Histology connected with 
the Columbia Veterinary College, and has proved to be a very 
efficient knife. 
The mode of action is very simple. The object having been 
previously placed in any ordinary hand-cylinder and mounted 
Fig. 12. 
in wax, paraffine, or pith, the sections are made by a stroke of 
the knife, which is pushed straight forward. As will be readily 
seen, the larger the section the wider the knife must be. 
The blade is made of the best plate steel, and is easily kept 
in order. 
STAINING FLUIDS. 
Ammonia carmine.—This is one of the oldest and best 
known solutions. Take one part, by weight, of the best car- 
mine, which is known as “ No. 40,” dissolve it in 100 parts of 
distilled water, and add one part of aqua ammonise. The pre- 
vious dull color now gives place to a most brilliant and deep 
red. It is necessary, however, that the carmine be either neu- 
tral or very faintly alkaline, else the color will diffuse and the 
tissues will be differentiated. Expose the fluid, therefore, 
for some weeks to the air, or evaporate over the water-bath 
until the odor of ammonia is no longer perceptible. 
The nuclei should be deeply and brightly stained, while the 
intercellular substance is in no way affected. If, however, 
diffusion has taken place, a great deal of it may be removed 
by soaking the section in a saturated alcoholic solution of ox- 
alic acid. When a brick-red color has in this way been ob- 
tained, the object has been accomplished. Crystals of oxalic 
acid are apt to be found in specimens that have been prepared 22 
MANUAL OF HISTOLOGY. 
in this way. It is therefore desirable, after using the acid, to 
wash thoroughly in alcohol or water. 
Borax carmine (Arnold’s formula).—The following method 
is given by Dr. M. N. Miller as the one in use by students in 
the histological laboratory of the New York University. It 
originated with Prof. J. W. S. Arnold. A saturated solution 
of borax is prepared in a wide-mouthed pint bottle. The borax 
should be in some excess. “No, 40” carmine is now added 
to the solution under constant agitation, until after a while it 
no longer dissolves, and an excess remains at the bottom of the 
vial, mingled with the crystals of borax. After twenty-four 
hours the supernatant fluid is decanted. To this clear portion 
f. 3 ij. of alcohol are added, and f. 3 j. of caustic soda solution 
(U. S. P.). The staining solution is now ready. Or, the alco- 
hol may be omitted (Arnold), and the liquid evaporated to dry- 
ness ; the red amorphous mass is then powdered. Of this, 
15 grains are placed in an ounce of water, to which f. 3 j. of 
alcohol is added.1 
Sections, after staining, should be washed in alcohol to re- 
move the superfluous coloring fluid, and then transferred to a 
saturated solution of oxalic acid in alcohol to fix the color. 
The oxalic acid is then washed out in alcohol; finally the sec- 
tions are cleared up in oil of cloves, and mounted in balsam or 
dammar. 
Double staining by borax carmine and indigo carmine.—- 
Drs. W. T. Norris and E. 0. Shakespeare, of Philadelphia, 
have recommended a method which is a modification of Mer- 
kel’s. Two staining fluids are made, one red and the other 
blue. The red one contains carmine, gr. 7\; borax, 3 ss.; dis- 
tilled water, |j. The blue contains indigo carmine, 3 ss.; bo- 
rax, 3ss.; and distilled water, | vij. 
After thorough trituration the ingredients are mixed and 
left in a vessel; the supernatant fluid is then poured off. The 
sections, if previously hardened in bichromate, picric acid, or 
chromic acid, should be well washed ; they then are to be 
placed for a few minutes in a mixture (equal parts) of the red 
and blue fluids, then transferred, without washing, to a satura- 
ted solution of oxalic acid and allowed to remain in it rather 
less time than in the staining fluid. When sufficiently bleached 
1 [This preparation of borax carmine is the best that I have ever used.—T. E. S.] STAINING FLUIDS. 
the sections should be washed in water until every trace of ox- 
alic acid is removed. Sections thus prepared may be mounted 
in balsam ar dammar. Connective-tissue substances are blue, 
while the nuclei are red. The osseous lamellae of bone are 
blue, the cells in the lacunae red, while the marrow is apple- 
green. 
Picro-carmine (Miller’s).—Add one part of a saturated so- 
lution of picric acid to two parts of the 15-grain borax carmine 
solution (Arnold’s). The epithelium of the glands and the 
muscles are stained yellow, while the nuclei of the cells and the 
connective tissues acquire the carmine color. Sections should 
remain in the picro-carmine solution for about twenty-four 
hours. Next they are washed quickly in water, then in alcohol, 
after which they are transferred to the oil of cloves. (For Ran- 
vier’s method of making picro-carmine, see the chapter upon 
the Histology of the Nervous System.) 
Hcematoxylon solution (Boehmer’s).—Dissolve 20 grains of 
hsematoxylon in one-half an ounce of absolute alcohol; then 
dissolve 2 grains of alum in an ounce of water. Some drops of 
the first solution are added to the second, which, after a short 
time, becomes a beautiful violet. It improves after keeping for 
a few days, and should always be filtered before using (Thin). 
Hcematoxylon solution (Kleinenburg’s).—First make a satu- 
rated solution of the chloride of lime in seventy per cent, alco- 
hol, and add alum to saturation. 
Then make a saturated solution of alum in seventy per 
cent, alcohol. Add the first to the second in the proportion of 
one to eight. To the mixture add a few drops of a saturated 
solution of hmimttoxylon in absolute alcohol (Thin). 
Hcematoxylon solution (Miller’s method).—Take a pint bot- 
tle, as in the former process, fill with water, and add about an 
ounce of common extract of logwood in coarse powder. Allow 
this to remain in a warm place for twenty-four hours, with 
occasional stirring. After the expiration of this time add pow- 
dered commercial alum until the liquid changes from the 
muddy brown color given by the logwood to a brilliant purple. 
The alum is to be added until no change is produced. An 
excess of the salt will do no harm. Add about f. §j. of alcohol, 
and after decanting or filtering it is ready for use. One 
may omit the alcohol at this stage, and evaporate to dryness 
as in the borax-carmine process. The powder thus obtained is 24 
MANUAL OF HISTOLOGY. 
added to water when required. Three grains to the ounce of 
water will give a fluid that will stain alcohol-hardened tissue 
in from ten to fifteen minutes. A solution containing ten 
grains to the ounce will stain very quickly. If it is desired to 
keep the solution, add f. §j. of alcohol for each ounce. Hsema- 
toxylon stainings are soaked in water for a few minutes to 
wash out the alum, then transferred to alcohol, clarified in the 
clove oil, and finally mounted in balsam or dammar. 
Klein's formula for hcematoxylon.—Mix in a mortar 5 
grammes of the officinal extract of heematoxylon, with 15 
grammes of alum, and pulverize carefully. To this add grad- 
ually 25 c.c. of distilled water, and filter. To the residue add 
15 c.c. of distilled water and again mix in a mortar, and filter; 
to this filtrate add 2 grammes of alcohol. !STow mix the two 
filtrates and keep in a glass-stoppered bottle. If the liquid 
should at any time become muddy, filter again. Care must be 
taken to prevent any acid from intermingling with the fluid. 
Acids cause the hsematoxylon to turn red ; for this reason, sec- 
tions which have been hardened in chromic acid should be 
placed in a watch-glass and covered with distilled water, to 
which add a drop or two of a 30 per cent, solution of caustic 
potassa ; allow it to remain therein 10 to 15 minutes. To use 
the hsematoxylon fluid, add a few drops to an ounce of distilled 
water, so as to make a pale violet solution ; allow sections to 
remain in this solution for 12 to 24 hours. Or, a stronger so- 
lution may be employed which will stain specimens in 10 to 30 
minutes, and still give good results. Mount in glycerine, ace- 
tate of potassa, balsam, or better, resinous turpentine. 
Eosine solution.—Eosine, first introduced by Fischer in 
1875, is much used in staining fresh preparations. It is cus- 
tomary to have a strong solution of one to ten or twenty on 
hand. A few drops are then added to a watch-glassful of water 
or alcohol. Fresh tissues are both stained and hardened. It 
affects the body of the cells, together with the nuclei. It is apt 
to diffuse, unless special care is taken, and long soaking, say 
for twenty-four hours, is practised. 
Double-staining with eosine and other aniline colors.— 
Schiefferdecker first stains in an alcoholic solution of eosine 
and then in a one per cent, watery solution of an aniline color 
(dahlia, methyl violet, or aniline green). Care must be taken 
not to extract the color when dehydrating the specimen in STAINING FLUIDS. 
alcohol according to the usual method; very deep staining is 
therefore desirable. 
Green coloration of the nuclei.—To effect this, Tafani em- 
ploys a fluid containing three or four parts of a saturated 
watery solution of aniline blue to some six or seven parts of a 
saturated watery solution of picric acid. 
Eosine and hoematoxylon for staining hone.— Busch recom- 
mends eosine and hsematoxylon for double-staining the zone of 
ossification in growing bone. The sections of decalcified bone 
are first immersed a few days in a one-half per cent, chromic 
acid solution, or in a one per cent, solution of the bichromate 
of potassium, and then, after washing with water, in a watery 
solution of eosine. In young bone, where ossification is pro- 
gressing, the cartilage matrix is blue, while the nuclei of the 
cartilage-cells adjoining the line of bone are red; the contents 
of the medullary spaces are also bright red, while in the bone 
trabecles there is a combination of blue and red. 
Eosine for 'permanent specimens.—Renaut has employed 
eosine to differentiate all forms of protoplasm, whether bodies 
or their processes. He either employs a watery solution alone, 
or with the admixture of one-third its volume of alcohol. 
The coloration is obtained after immersion of the sections from 
one-half minute to one minute. They are then washed in 
distilled water, and may be preserved in a neutral solution of 
glycerine to which one per cent, of chloride of sodium has been 
added to prevent the glycerine dissolving the eosine. These 
preparations will then remain unchanged for months. 
In examining the fixed corpuscles of the subcutaneous tis- 
sue, the same author injects beneath the skin a solution of 
eosine and water (1-500), and then removes a portion of the in- 
filtrated tissue with the scissors. The fibrous fascicles are un- 
affected, while the elastic fibres take the color deeply. 
The fixed corpuscles appear as red granular plates, while 
their nuclei take a very intense color. This reagent, therefore, 
is well suited for the study of connective tissues. In special 
instances the silver method may be used first, and then the 
eosine. 
Preparation of the cornea.—Klein has adopted the follow- 
ing plan for exhibiting this most delicate tissue. He first burns 
the centre of the cornea of a kitten with caustic potash, and 
then, twenty-four hours later, brushes the surface with nitrate MANUAL OF HISTOLOGY. 
of silver, and, half an hour afterward, immerses it in water 
acidulated with acetic acid ; after a day or two it is found to 
have a glutinous appearance. The lamellae are then easily 
stripped off, and in the middle portions, the corneal corpuscles 
assume a purplish-brown color while their nuclei are uncol- 
ored. The outlines of the lymphatic channels are also sharply 
defined. 
Plcro-hcematoxylon and eosine (triple-staining).—Wendt 
has described a method of double-staining by picric acid and 
haematoxylon. Only the very thinnest sections, however, give 
satisfactory results. A strong solution of haematoxylon is first 
employed. In this the sections are allowed to remain about 
twelve hours. After washing them in water, they are placed 
in a saturated solution of picric acid and carefully watched. 
They may be removed from time to time, examined with a low 
power, and, when properly stained, put in alcohol and mount- 
ed in Canada balsam with as little delay as possible. To ob- 
tain triple-staining, eosine may be conveniently combined with 
this picro-luematoxylon method. To insure good results some 
amount of practice is necessary. 
Double, triple, and quadruple staining.—Dr. Gribbes re- 
commends for double-staining, immersion first in picro-carmine 
and then in logwood, or which is better, immersion first in a 
spirituous solution of rosine or aniline violet, and then in an 
aqueous solution of aniline blue or iodine green. In obtaining 
more than two colors there is considerable difficulty. To ac- 
complish it he uses first the chloride of gold or picro-carmine 
and then the spirituous and aqueous solutions of the ani- 
lines. 
Staining with Bismarlc brown,—Make a watery solution of 
gr. ij.— 3j., heat and filter; soak in the solution about three 
minutes ; set the color with glacial acetic acid (4 per cent), 
for half a minute. After dehydrating with alcohol mount in 
dammar varnish. Weigert prepares the Bismark brown as 
follows : he makes a concentrated aqueous solution by boil- 
ing in water, filtering from time to time. He also uses a weak 
alcoholic solution, and combines with other colors. 
[To combine with eosine—pnt the sections in a strong aqueous solution of 
Bismark brown; remove after about two minutes, set in weak acetic acid (four 
per cent.), then place in a weak alcoholic or aqueous solution of eosine, and 
then again in the acetic acid solution.—T. E. S.] STAINING FLUIDS. 
Solution of alum-carmine.—Grenadier recommends tins 
fluid: Take a one to five per cent, solution of ordinary alum, 
or ammonia alum ; boil with one-half to one per cent, powdered 
carmine for twenty minutes. Filter, and add a little carbolic 
acid to preserve. 
Naphthaline yellow for hone. —ln sections of the femur 
from a foetal pig, three and a half inches in length, the follow- 
ing method was found to yield very excellent results : 
After immersion for three days in Muller’s fluid, sections 
were made, and, after washing in water, immediately dipped in 
an alcoholic solution of naphthaline yellow (gr. iv.— f j.); after 
eight to ten minutes the sections were removed, and dipped in 
a watery solution of acetic acid of three per cent.; then they 
were immersed for-about ten minutes in the%ordinary solution 
of ammonia-carmine, rendered neutral by exposure to the 
air. 
The sections were again dipped in the acetic acid solution 
in order to set the color, and then placed in alcohol of eighty 
per cent., and subsequently in absolute alcohol. 
The specimens thus stained showed a matrix of deep trans- 
parent chrome yellow. The young bone-corpuscles and osteo- 
blasts, on the other hand, together with the fibrous tissue, 
assumed a brilliant rose color, thus affording an excellent con- 
trast between forming and formed bone. 
Staining with methyl-green and induline. —Calberla has 
introduced two new substances into use, viz., methyl-green and 
induline. The one stains the nuclei of the cells of the sub- 
cutaneous tissue, the nuclei of vessels and nerve-sheaths rose 
color, while the cells of the corium and their nuclei are a 
violet red; the other colors the cells of the Malpighian layer 
a greenish blue. Combinations of methyl green and eosine are 
also recommended. Eosine (one part) and methyl green (sixty 
parts) are to be dissolved in a thirty per cent, solution of warm 
alcohol. The epithelial nuclei take a violet blue, the nuclei 
of connective tissue a greenish blue, and the cell-body a red 
color. Singular differentiations are made; thus, while the 
striated muscle is red, the nuclei are green. On the other 
hand, smooth muscular tissue is green, and the intercellular 
substance red. In the salivary glands the cells of the excretory 
ducts are blue, while the so-called secretory cells are red. In- 
duline dissolves in warm water and in dilute alcohol. Take a 28 
MANUAL OF HISTOLOGY. 
concentrated watery solution, dilute it with six times its 
volume of water, then immerse the preparations from 5 to 20 
minutes, wash them out and clarify in oil of cloves or glycerine. 
The peculiarity of this material is that it never affects the 
nucleus, but only the cell-body. More frequently, however, it 
is the intercellular substance that is colored blue. 
Purpurine.—Ranvier has recommended this dye, which is 
extracted from madder. Alum (one part) is dissolved in dis- 
tilled water (two hundred parts); the fluid is then heated to 
the boiling point in a porcelain dish. Then a small quantity 
of purpurine is dissolved in distilled water and added to it. 
Sufficient purpurine should be added to leave a residue, by 
which it is certain that the solution is saturated. While still 
hot it is to be filtered into alcohol of one-fourth the total 
volume. The fluid has an orange red color, and is more effi- 
cient when fresh. Sections should be immersed from 24 to 48 
hours. 
French archil—Staining with extract.—Wedl uses this 
substance, which, after the loss of the ammonia, is dissolved 
in 20 c.c. absolute alcohol, 5 c.c. acetic acid of 1.070 sp. gr., 
and 40 c.c. of distilled water so as to make a saturated solu- 
tion. Protoplasm and matrix, but not nuclei, are colored a 
beautiful red. 
Alizarine.—This aniline color is recommended by Than- 
hoffer, but experience is limited with reference to it. It has a 
golden yellow color, and is easily fixed by the tissues. 
METALLIC SOLUTIONS. 
Staining with osmic and oxalic acids.—Broesicke adopts 
the following method: 
Little pieces of fresh or freshly dried preparations are left 
for an hour in a one per cent, solution of osmic acid ; then 
they are carefully washed and soaked in a cold saturated solu- 
tion of oxalic acid, and finally examined in water or gly- 
cerine. Elastic fibres are yellow, fat is black, while the walls 
of capillaries and many connective-tissue substances are 
red. 
Chloride of gold and lemon juice. Ranvier is in the 
habit of demonstrating the corneal nerves by using lemon- METALLIC SOLUTIONS. 
Juice in which the tissue is left live minutes. Then it is soaked 
for 15 to 20 minutes in 3 c.c. of a one per cent, solution of the 
gold chloride, and finally 25 to 30 minutes in distilled water 
to which one or two drops of acetic acid has been added. After 
two or three days’ exposure to the sun, the fibres become dis- 
tinct. 
Nitrate of silver in solution (gr. j.—iv.— | J.) is much used. 
The details of the method will be found in the Chapter on the 
Lymphatics. 
Chloride of gold has also been much used in studying 
the so-called lymph-canalicular system of the cornea. The 
method of emqDloying it will be found in the section relating to 
the cornea. 
Osmic acid in solution is also very useful. Its effects are 
given in the chapter on the General Histology of the Nervous 
System. 
Methyl-green for showing waxy change.—Curschmann, of 
Hamburg, has recommended this reagent to effect the same 
object as the violet de Paris of Cornil. A solution of about 
five grains to the ounce is used. The specimens are bathed in 
the fluid a few minutes or hours. They take the color quickly. 
After staining they may be mounted in glycerine. The amy- 
loid material assumes a brilliant rose color. The surrounding 
tissue takes a dull green. 
Wickersheimefs preserving liquid. —This material has 
been extensively used of late, and there are several formulae 
for it. Among the most recent modifications is that made by 
the firm of Poetz & Flohr, of Berlin. For immersing speci- 
mens the ingredients are: arsenious acid, 12 grains; sodium 
chloride, 60 grains ; potassium sulphate, 150 grains ; potassium 
nitrate, 18 grains; potassium carbonate, 15 grains; water, 10 
litres ; glycerine, 4 litres ; wood naphtha, f litre. A modified 
fluid is used for injecting the blood-vessels. This is suitable for 
all fresh tissues, preserving them in their natural color and 
consistence. 
If the tissues are to be used subsequently for the micro- 
scope, it is said that they should be washed thoroughly in 
water, but it seems from recent experiments that the fluid un- 
fits them for minute examination. It is also rather expensive, 
and has an extremely pungent and unpleasant odor. 30 
MANUAL OF HISTOLOGY. 
METHODS OF INJECTING THE BLOOD-VESSELS.1 
Good injections are hard to make, requiring skill, patience, 
and practice. First of all, it is essential to have a perfectly 
transparent injecting material. This is usually made up with 
gelatine and colored by carmine or Prussian blue. When 
carmine is used it is customary to dissolve it in ammonia, fil- 
ter, and then add it to the solution of gelatine. In order to 
obtain a neutral or faintly acid liquid, acetic acid is added, 
drop by drop, until the alkalinity is overcome, but there must, 
at the same time, be no precipitation of carmine, which is best 
detected by the granules of carmine seen in the field of the 
microscope. If alkaline, the color diffuses and the result is 
a failure. 
It is difficult to lay down any rule in reference to the amount 
of acetic acid necessary ; the color of the liquid is the best 
and only satisfactory test. The ammoniacal odor, if very 
slight, cannot be detected, and therefore is useless as a test. 
A slight excess of acid, however, will do no harm. 
The preparation of the blue injecting fluid is less difficult. 
Usually Briicke’s soluble Berlin blue is used; it can be 
procured at most of the large drug stores, but if not obtaina- 
ble, may be made as follows (Klein) : 
“ Take of potassic ferrocyanide 217 grammes, and dissolve in 
one litre of water (solution A). Take one litre of a ten per cent, 
solution of ferric chloride (solution B). Take four litres of a 
saturated solution of sulphate of soda (solution C). Add to 
A and B two litres of C. Then, with constant stirring, pour 
the ferric chloride mixture into a vessel, collect the precipitate 
upon a flannel strainer, returning any blue fluid which at first 
escapes through the pores of the flannel; allow the solutions 
to drain off. Pour a little distilled water over the blue mass, 
returning the first washing if colored, and renew the water 
from day to day until it drips through permanently of a deep 
blue color. This is a sign that the salts are washed away, and 
all that is further necessary is to collect the pasty mass from 
the strainer and allow it to dry.” 
Having obtained the soluble Berlin blue, it will be much 
1 Prepared for the editor by Dr. W. H. Porter, Curator of the Presbyterian Hos- 
pital, New York city. METHODS OF INJECTING THE BLOOD-VESSELS. 
simpler to inject both arteries and veins with the same solution. 
If a small animal is to be employed (as the rabbit, for instance) 
it will be found most convenient to inject through the aorta. 
If, however, an organ from the human body is to be injected, 
through the main vessels of that part. To commence with, the 
kidney is probably the best, as it is small and of firm consis- 
tence. 
For injecting with the red gelatine liquid the following rules 
will be found of service, and yield good results: 
Take 40 grammes of Cox’s best English gelatine, place it 
in ajar, and add just water enough to cover it; let it stand 
for several hours, when it will imbibe the water, being hygro- 
scopic ; it may then be dissolved over a water-bath. 
Take of the carmine 22 grammes and dissolve in 40 c.c. of 
aqua ammonhe, then add 240 c.c. distilled water, and filter. 
The preparation of the carmine solution had better be com- 
menced the day before, as it takes about twenty-four hours to 
filter. The gelatine and carmine solutions are raised, separately, 
to the same temperature, when the gelatine solution is gradu- 
ally added to the carmine solution, under constant stirring. 
The injection fluid, which is now of a deep cherry-red color and 
alkaline reaction, is precipitated with acetic acid until the deep 
cherry color gives place to a bright red, and the ammoniacal 
odor is exchanged for that of acetic acid. At this point a little 
more acid may be added without doing harm. In case the 
liquid should be found too concentrated, a little more water 
may be added. For the blue mass the following method may 
be adopted: 
Take 66 grammes of gelatine, and prepare as in the former 
case. Add 4 grammes of soluble Berlin blue in substance and 
360 c.c. of water. 
The blue will also be found slow in filtering. When both 
are heated to the same temperature add the gelatine to the 
blue solution, with constant stirring. When this has been 
done, a solution of the iron salts may be added to intensify the 
blue color, care being exercised not to add enough of the iron 
to coagulate the gelatine. This liquid also may be diluted 
if found so concentrated that it will not flow easilj7. The 
liquids having been prepared, the organ carefully removed 
from the body, thoroughly washed out and heated to a tem- 
perature of 98° F., everything is ready for injection. The fill- MANUAL OF HISTOLOGY. 
ing of the vessels may be accomplished in one of two ways : 
either by forcing in the fluid with a syringe or by the pressure 
of a column of water. The syringe is the simplest, but requires 
practice and skill in manipulation. 
Having inserted the canula into the artery, the kidney may 
be entirely tilled with either the red or blue injecting liquid. 
When the organ is seen to be swollen, tense, and well colored 
the vessels must be tied off, and the kidney placed in a freez- 
ing mixture until the gelatine has set. When this is accom- 
plished, the organ should be cut into small pieces, and placed 
first in a weak solution of alcohol (seventy per cent, or less), 
and the strength of the alcohol gradually increased until the 
specimen is sufficiently hard for cutting. The object of using 
weak alcohol is to prevent too great shrinkage of the gelatine. 
If two colors are used, it is impossible to tell beforehand how 
much fluid will be necessary to fill the arterial and venous sys- 
tems, and not have the one encroach on the other. For an 
ordinary kidney, about 250 c.c. of the injecting liquid should 
be prepared to fill the arterial vessels, and nearly double to 
fill the veins. The following rules must be observed in inject- 
ing : keep the gelatine solutions and the organ as nearly as 
possible at the same temperature. Immerse the organ in warm 
water during the process. Avoid the entrance of air into the 
canula when connecting the syringe. Inject slowly, and give 
the fluid time to work its way into the minute capillary rami- 
fications. 
The above rules can be applied to any organ, with such 
modifications as will suggest themselves to the operator. 
BIBLIOGRAPHY. 
Klein. Handbook of the Physiological Laboratory. Edited by Sanderson. Yol. I. 
1878. 
Busch. Arch. f. Mikroskop. Anat. XIV. 1877. 
Norms and Shakespeare. American Journal of the Medical Sciences, Oct., 1877. 
Benaut. Archives de physiol. 2me Serie, T. IV. 1877. 
Schaefer. Histology and the Microscope- Philadelphia, 1877. 
Thin. Practical Histology. London, 1877. 
Wendt. Ueber die Hardersche Druse, etc. Strassburg, 1877. 
Eanvier. Traite technique d’ histologic. Paris, 1877-8. 
Broesicke, J. Med. Centralblatt. 46. 1878. BIBLIOGRAPHY. 
Calberla. Morpholog. Jahrb. 111. H. & S.’s Jahrb. I. 1878. 
Hamilton. Journal of Anatomy and Physiology. Vol. XII. 1878. 
Miller. New York Medical Record, Peb. 2, 1878, p. 97. 
Ranvier. Journ. de micrographie. H. & S.’s Jahrb. 1878. 
Schiefferdecker. Arch. f. mikrosk. Anat. XIY. 1878. 
Tafani. Journal de micrographie. 1878. 
Wedl. Virchow’s Archiv, 74. 1878. 
Weigert. Arch. f. mikrosk. Anat. XV., p. 259. 1878. 
Flesch. Archiv f. mikrosk. Anat. XVI., p. 300. 1879. 
Grenaciier. Arch. f. mikrosk. Anat. XVI., p. 468. 1879. 
Klein and E. Noble Smith. Atlas of Histology. 1879-80. 
Curschmann. Archiv f. Path. Anat. LXXIX., 111. 1880. 
Frey. The Microscope and Microscopical Technology. New York, 1880. 
Gibbes. Lancet, March 20, 1880. 
Hailes. An Improved Microtome. New York Medical Record, July 24, 1880. 
Thanhofper, L. v. Das Mikroskop u. seine Anwendung. Stuttgart, 1880. 
Vincent. New York Medical Record, June 12, 1880. 
Wickersiieimer. Arch. f. Pharm. New Remedies, May, 1880. 
Gibbes. Practical Histology and Pathology. Philadelphia, 1881. 
Seiler. Compendium of Microscopical Technology. Philadelphia, 1881. 
Stowell. The Student’s Manual of Histology. Detroit, 1881. 
Harris and Power. Manual for the Physiological Laboratory. New York, 1881. CHAPTER 111. 
THE BLOOD. 
In man and most vertebrates the blood consists of a clear 
fluid, the liquor sanguinis or plasma, in which a large num- 
ber of corpuscles are very evenly distributed. Of these there 
are two prominent varieties, differing much in character—the 
red and the colorless or white. The former are greatly in ex- 
cess, and give to the liquid its characteristic red appearance. 
In relative proportion the two vary greatly within certain 
limits. Usually there is but one of the white to 600 or 1,200 of 
the red ; but these numerical relations are disturbed by vari- 
ous diseases, and the white may equal the red, or even, in rare 
cases, exceed them. 
In fresh liquid blood the corpuscles are the only solid mat- 
ters visible under the microscope ; nor is there any difference 
in this respect with coagulated blood, when the quantity is 
large. If, however, a little should be allowed to dry, fibrin 
may be deposited under the form of delicate filaments, which 
are superimposed on one another without definite order. 
In one hundred volumes of blood there are said to be thirty- 
six volumes of corpuscles and sixty-four of plasma. This ratio, 
however, is altered somewhat by different conditions, such as 
the age and health of the individual. 
The red corpuscles in man and other mammals, with very 
few exceptions, are bi-concave bodies, circular in outline. In 
birds, amphibia, and almost all fishes they are also bi-concave 
or hollowed out at the centre, but have an elliptical contour. 
In the human species nuclei or central bodies appear at a very 
early period of life, but subsequently are invisible, unless arti- 
ficial means are used to display them. In birds, amphibia, and 
fishes a rounded prominence is also seen at the centre, which is 
particularly well marked when the corpuscle happens to be THE BLOOD. 
turned so that its edge meets the eye. This prominence cor- 
responds to the ordinary nucleus of other elementary bodies or 
cells. In this position the peculiar shape of the corpuscles, 
with their constricted centres and rounded extremities, has 
suggested a comparison between them and the little cakes 
known as lady’s-fingers. (See Fig. 18.) 
It is obvious also that this varying thickness of the disk will 
have some effect upon the microscopic image, for the whole 
superficies cannot be in focus at one time, even when the cor- 
Pig. 14.—Human red blood-corpuscles; a, globules 
showing the double contour; 6, globules turned on 
edge ;c, the same in rouleaux like coin. Rollett. 
Fig. 13.—Red corpuscles of 
the frog. ' Rollett. 
puscle is turned flatwise to the eye. There will be some differ- 
ence between the level of the thickest and thinnest portions. 
As a result, when one is dark the other is bright, when one is 
well defined the other is blurred. This statement serves for an 
explanation of the double contour that is sometimes observed 
in human blood (see Fig. 14), though it has also been offered 
in support of the theory that the semi-solid and elastic matter 
of which the disk is mainly composed has an external envelope 
or limiting membrane of different density. It is to be remem- 
bered, however, that the property of double refraction which 
explains the double contour, belongs to all transparent bodies 
that have rounded edges, such as drops of water or oil, in 
which cases there is no enveloping or peripheral wall. 
When the lens and eye-piece are suitably combined, as in the 
best microscopes, the double marking is often difficult or im- 
possible to discover. On the other hand a poor optical com- 
bination will generally exhibit it to an unpleasant degree, and 36 
MANUAL OF HISTOLOGY. 
especially if great amplification is aimed at. Lenses of very 
high power are also apt in any case to exhibit the same ap- 
pearances. 
Measurements of the red corpuscles in man and ani- 
mals.—The average diameter of the human red globule is still 
a matter of discussion. The faulty measurements of the older 
writers have led to some misconception on these points, and the 
matter has required new study. Welcker, who has long been 
an authority on the Continent, gave .00774 mm. as the average 
breadth in the human male, with a minimum of .0045 mm., the 
latter from personal observation. A maximum of .010 mm. 
has been given by Max Schultze, while Frey places the average 
thickness at .0018 mm. Later investigations by Hayem show 
that a diameter of .012 mm. or even .014 mm. may be reached, 
while he has known it to fall as low as .0022 mm. Elsberg 
gives the mean diameter of the red blood-corpuscle at .0075 
mm., agreeing very nearly with Welcker. He has observed a 
maximum of .01016 mm., and a minimum of .00422 mm. 
Measurements of single corpuscles have no value in deter- 
mining the particular animal from which the blood has been 
obtained, and this is an object of prime importance in medico- 
legal cases. It is common, therefore, to make a hundred or 
more single measurements, and then take the average of them. 
And yet this figure may vary considerably in different individ- 
uals, or even in the same one. In the blood of the puppy, for 
instance (the size of the dog’s corpuscle being very nearly 
that of man’s), a recent observer found that the average diame- 
ter of fifty corpuscles varied only two-millionth of an inch 
from a like average of fifty taken from his own blood. In 
another instance, taking forty from a puppy, he found that 
the average differed only seven-millionth of an inch from a 
similar average of his own (Woodward). 
Opposite is given a table of blood-corpuscle measurements 
by Welcker and others. 
By referring to it, the cat’s and rabbit’s corpuscles will be 
found to have an average diameter which is not far distant 
from man’s and dog’s, while the minimum and maximum 
diameters of each show conclusively that a large number of 
their corpuscles would be likely to equal man’s, and there- 
fore make it impossible to distinguish one from the other. To 
obviate this source of error a very large number of corpuscles THE BLOOD. 
would have to be measured separately, as we have already 
seen, and then an average taken of them all, before even a 
guarded opinion could be given as to the source of the blood.' 
Still other difficulties, however, are apt to beset the microscop- 
ist. The blood is usually dried and in small quantity. The 
disks are then shrunken. If we endeavor to restore them to 
their original shape, as by soaking in blood-serum, we are 
never sure of having accomplished the object, or that we have 
not overdone it. This statement will be better understood by 
experiments that will be detailed at another point in this 
chapter. Where blood-corpuscles are elliptical, as in birds, 
there is much less opportunity for error. 
Measurements of red Blood-corpusdes. 
Maximum 
diameter. 
Minimum 
diameter. 
Average 
diameter. 
Dog 
mm. 
.0082 
mm. 
.0065 
mm. 
.0073 
Cat. 
.0074 
.0058 
.0065 
Rabbit 
.0080 
.0063 
.0069 
Sheep 
.0056 
.0038 
.0050 
Goat (old) 
.0046 
.0036 
.0041 
“ (eight days old) 
.0066 
.0039 
.0054 
Moschus iavanicus 
.0030 
.0032 
.0025 
Elephant 
.0106 
0084 
.0094 
Pigeon (old) 
.0160 
.0183 
.0147 
‘4 (fledgling) 
.0140 
.0116 
.0126 
Chicken 
.0133 
.0104 
.0131 
Duck 
.0140 
.0118 
.0129 
Yespertilion 
.0066 
.0054 
.0061 
Triton cristatus 
.0327 
.0259 
.0293 
Salamandra crvntobranchus 
.0415 
.0302 
.0378 
J aponicns 
.0579 
.0460 
.0513 
Lepidosiren annectens 
.0440 
.0360 
.0410 
Average 
length. 
Average 
breadth. 
Proteus anguineus 
mm. 
.058 
mm. 
.034 
.075 
.047 
The number of the red globules.—lt has commonly been held 4 
that the blood of an adult man contains 6,000,000 red corpus- 
cles in each cubic millimetre. In anaemic conditions this num- 
ber may be reduced below 3,000,000, while in fair physical 38 
MANUAL OF HISTOLOGY. 
health it has reached 6,000,000 and over. Under ordinary cir- 
cumstances 4,500,000 is thought to argue a fair bodily condi- 
tion (Keyes). 
Quite recently Hayem lias given an instance where the number was reduced 
to 800,000. This extraordinary state he has called aglobulie intense ; the name 
aglobulie extreme was given to a condition observed on another occasion where 
he counted only 450,000 corpuscles. 
The blood-globules in an indifferent fluid.—In order to get 
a proper conception of the various influences that act upon the 
red corpuscles, so as to alter their form, size, and internal 
appearance, it is essential to subject them to some of the more 
common, such, as water, acids, alkalies, electricity, etc. In 
no other way can the student appreciate the extraordinary 
changes which these bodies suffer, and indeed a knowledge of 
such matters is quite necessary in studying the histology of 
either normal or diseased tissues. 
Unfortunately we are not always able to use human blood 
for these demonstrations because the corpuscles ,are too small, 
and consequently the alterations do not admit of easy observa- 
tion. We naturally turn to an object that has larger corpuscles 
and may be procured with little trouble or expense. 
The frog is therefore selected, or, even better still, the newt, 
which is especially well suited for this purpose. At first the 
blood may be examined in a menstruum similar to the liquor 
sanguinis or plasma, and the frog’s aqueous humor is usually 
found satisfactory. 
To a drop of this latter add an equal quantity of the blood, 
mix them well with a glass rod, and adjust an ordinary 
f inch circle. The aqueous humor exerts no special influ- 
ence over the corpuscles, and is therefore called an indif- 
ferent fluid. If it be impossible to obtain aqueous humor, an 
excellent substitute may be found in the fresh fluid from a 
hydrocele or ovarian cyst, or we may use serum to which iodine 
has been added, which is then called iodized serum. To six 
ounces of the fluid twenty grains of finely powdered iodine are 
added. After prolonged agitation the iodine will be dissolved, 
and the mixture thus prepared may be kept for a number of 
months. Suspended in this liquid the blood is studied to 
advantage with a lens of moderate power, such as an ordinary THE BLOOD. 
I inch. The contents of the disk will appear homogeneous, 
which is a term that merely indicates an apparent absence of 
structure. The nucleus and nucleolus should also be invisible. 
The shape of the corpuscles is oval, and they are flattened and 
have rounded edges, with hollowed centres, in which a promi- 
nence is usually seen (Fig. 13). The protoplasm is the sub- 
stance of which the disk is made ; it has a light yellow color, 
and is dull or pellucid in appearance, much like semi-solid 
jelly. 
Brownian and amoeboid movements. Using the same 
method of preparation the white corpuscles or leucocytes are 
seen to good advantage. They are much smaller than the red 
disks (in the frog—the reverse of human blood), and there is 
wide range in size, one histologist (Klein) having described as 
many as thirty varieties. In the interior, little dark spots are 
sometimes seen in constant vibration. By a skilled observer they 
are readily detected, even with a good inch glass. When 
such specks are numerous the bodies are said to be granular. 
In the newt’s blood this phenomenon is usually best seen. 
The word granule has been applied in these cases from the 
notion once prevalent that the little dots were molecules sus- 
pended in a menstruum of some sort that filled the corpuscle. 
This subject is now eliciting much study, but the movement, 
whatever its significance may be, is called the Brownian move- 
ment. 
Klein, who states that the newt’s leucocyte is traversed by an intracellular 
network, believes that the movement just described is due to the motion of the 
“ disintegrated network ” under the stimulus of imbibed water. Under this 
explanation the oscillatory movement in the corpuscles of the human saliva 
would indicate death rather than life. When fluid has been withdrawn by 
evaporation the phenomenon ceases. According to other histologists this 
vibratile motion is an indication of vital action. 
The remarkable change in form which these corpuscles un- 
dergo is a more positive indication of vital power in the leuco- 
cyte. When the little body is placed under conditions which 
imitate those of its natural state it commences to put forth 
processes and then withdraw them, carrying on these move- 
ments slowly, but with a certain degree of regularity. While 
this is being accomplished the corpuscle is observed to move 
about from place to place. MANUAL OF HISTOLOGY. 
In Fig. 15 the leucocytes are seen. Those marked with the 
letter a are engaged in amoeboid motion. The one marked b 
i? in a state of contraction. This phenomenon is called amoe- 
boid movement, because it resem- 
bles that of the amoeba—the lit- 
tle microscopic organism found 
in stagnant water. In order to 
permit these changes to continue 
for some length of time, it is well 
to paint a little oil or glycerine 
around the edge of the circle. 
Evaporation is thus prevented. 
If the warm slide be used the 
changes will follow with greater 
rapidity. Both Brownian and 
amoeboid movements are usually confined to a limited number 
of the corpuscles, and the former often to only a small portion 
of the interior. 
Fig. 15.—Leucocytes: a, putting out pro- 
cesses ;6, having withdrawn them. Rollett. 
The slide 1 for heating consists of an ordinary glass slide 
(Fig. 16) upon which is riveted a thin copper plate (p) perfor- 
ated in the centre, so as to allow space for the drop of blood 
which is to be examined. From the copj)er plate extends an 
arm (c) over which is slipped a spiral copper wire (<?), that is 
heated by the flame of an alcohol lamp. By this means the 
glass plate is kept warm and with it the drop of blood. In 
order to secure a proper 
amount of heat and no 
more, it is customary 
to put a little bit of 
cocoa butter upon the 
corner of the slide. The 
butter melts at the tem- 
perature of the body, 
and after this point has 
been reached the lamp 
should be carried along 
the wire away from the slide until the precise distance is found 
at which this particular degree of heat will be maintained. 
Fig. 16.—Slide for heating; «, slide; 6, copper plate; c, arm 
over which the spiral wire (d) is slipped 
Action of a dilute salt solution.—It is often difficult, and, 
1 Made by T. H. McAllister, 49 Nassau Street, New York City. THE BLOOD. 
indeed, impossible, to obtain aqueous humor or even an animal 
fluid such as has been described, and microscopists have accord- 
ingly made use of a substitute that can be prepared at any time 
and kept indefinitely. This is a solution of common salt in 
distilled water (1—400). Add a drop of fresh frog’s blood to a 
drop of the salt solution, mix them well, and it will be seen 
that the delicate protoplasm of the red blood-corpuscle, most 
susceptible of change, is not altered in appearance, though the 
body itself will change in form from the elliptical to the spher- 
ical. This salt solution has been found, in practice, an excellent 
substitute for blood-serum, and is very generally used in ex- 
amining fresh specimens, where it is important to avoid any 
material change in the corpuscle. 
Action of distilled water—lrrigation.—The effect of water 
is also noteworthy, as it is a very important consideration in 
both histological and pathological work, especially the latter. 
Take a drop of frog’s blood, add to it an equal quantity of 
distilled water and apply a cover. The nucleus or central body 
will now be readily seen, surrounded by a yellow border ; the 
body of the corpuscle or peripheral part will at the same time 
gradually become paler and larger. Now add distilled water 
slowly, drop by drop, in the following way : Take a long strip 
of tissue or filter paper about half the length of the slide and in 
breadth equal to one-half the diameter of the cover. Apply 
the water with an ordinary minim dropper, close to the edge of 
the cover, on the side opposite to the paper strip. This latter 
will now take up the excess of water and cause a stream to 
pass through the specimen. This process is called irrigation. 
Push the paper a short distance under the edge of the cover, 
and the solid particles in the fluid will be carried to the edge 
of the paper, where they will remain at rest and may be ob- 
served at one’s leisure. 
This plan is often useful in other sorts of microscopic work, as in looking 
for renal casts, urinary crystals, etc. It may save much valuable time. I first 
learned it from my friend, Dr. Edward Curtis, of this city. 
Continued addition of water will cause the corpuscles to 
swell and after a time burst, or, at any rate, become so expand- 
ed that they can scarcely be seen. When water is applied 
slowly to human blood, the corpuscles soon begin to lose their 42 
MANUAL OF HISTOLOGY. 
disk-like form and assume a splieroidal, perhaps spherical con- 
tour. The coloring matter then escapes, in most instances, and 
they become quite transparent (see Fig. 17). Such corpuscles are 
often seen in human urine where they appear as colorless rings. 
In frog’s or newt’s blood the body of the disk first imbibes the 
Fig, 17.—Human red blood-globules: 
ffl, with hmmoglobin; b, without it. Rol 
istt. 
Fig. 18.—Red corpuscles of the frog 
that have imbibed water. Eollett. 
water ; later, the nucleus, which then has a sharply defined 
outline. Sometimes the material of which the body is largely 
composed (haemoglobin) is gathered about the nucleus, sending 
off radiating prolongations to the periphery, while the imbibed 
fluid is stored in the intervening spaces (see Fig. 18). 
Action of carbonic acid gas.—This experiment requires a 
special apparatus. First of all it is essential to have a moist 
chamber (Fig. 19). 
Take a small, flat bit of wood about men. wide, 3 inches 
long, and f inch thick ; make a square opening in the centre, 
sufficiently large to admit an ordinary f inch cover-glass ; this 
is to be pressed to the bottom and firmly fixed, thus making a 
shallow well with a glass 
bottom. Into this cham- 
ber are admitted, through 
side holes, glass tubes (one 
on each side), so that air 
or gases can be carried into the chamber. When in use, the 
chamber is kept moist by a drop of water, which is put in 
one corner of the well, while the specimen of blood to be ex- 
amined is dropped upon a large glass cover, and the latter in- 
verted over the mouth of the well. In determining the effect 
of carbonic acid gas upon animal life, we have merely to con- 
nect the gas-chamber just described with a jar in which carbonic 
Fig. 19.—Moist chamber. THE BLOOD. 
acid gas is generated. Fig. 19 illustrates a gas or moist cham- 
ber of the same general character, and devised by Dr, J. 11. 
Hunt, of Brooklyn. Take a large gallon flask, fill it partly 
full of pulverized marble-dust, attach it by means of a rubber 
tube through a perforated stopper to a Wolff’s bottle, which 
latter must be connected with the moist chamber. Now gener- 
ate the carbonic acid gas in the flask by pouring muriatic acid 
upon the marble-dust. When the gas is being evolved it will 
be known by the ebullition of the water in the Wolff’s bottle. 
Now place the moist chamber upon the stage of the micro- 
scope. Take a drop of newt’s blood, dilute it with serum or an 
indifferent fluid, and mount it upon a glass cover, which invert 
over the well, first seeing that the edge of the cover is oiled, so 
that it will remain in place. Now connect the tube of the moist 
chamber with the tube of the gas-generator, and the carbonic 
acid gas will enter and pass through the chamber. The rapidity 
with which the current moves may be regulated by a spring 
clip. As soon as the gas enters, the central body or nucleus 
becomes distinctly visible, and is surrounded by a yellow halo ; 
when, however, the gas is withdrawn and atmospheric air 
is admitted, the nucleus and colored zone disappear. This 
double experiment may be repeated a number of times. Finally 
a point will be reached where all action will cease. This cen- 
tral body, under such circumstances, has been called the zooid, 
and the corpuscle proper the oikoid (Bruecke). 
Action of acids upon the blood.—Acetic acid is commonly 
nsed in observing the changes that are produced by an acid 
solution. 
Take the ordinary dilute watery solution of acetic acid 
(1 per cent.) so much used in laboratories, add a drop of it to 
an equal amount of frog’s blood. The red globules instantly 
exhibit nuclei. The colorless globules also cease their motion, 
if any has existed, and they become granular and shrivelled. 
The term granular is used merely in a relative sense and has no 
special reference to granules whether present or not, but merely 
to an appearance that has already been explained. 
These phenomena are more marked if the solution is con- 
centrated. The red bodies, also, in such case, are apt to crack 
and split up. A good way of determining the proper strength 
for the ordinary acetic acid solution is to pour a little into an 
ordinary watch-glass, and then add chemically pure acetic 44 
MANUAL OF HISTOLOGY. 
acid drop by drop until the solution is faintly acid to the 
taste. 
Action of alkalies upon the blood.—Take a drop of the 
newt’s blood and mount it in a drop of serum or of salt solu- 
tion. Then, affixing a strip of bibulous paper in the w7ay that 
has been described, add drop by drop a weak solution of aqua 
ammonise. A similar strip of paper, somewhat larger in size, 
upon the other side, will cause a current and carry the corpus- 
cles to the side of the field where the paper strip is largest, and 
there the corpuscles may be observed at rest, and the altera- 
tions effected by the alkali duly noted. It will be seen that 
after a little time the corpuscles, both red and colorless, will 
swell up and finally, after a time, provided the alkali be in 
sufficient amount, disappear or become so expanded as to be 
invisible. Sometimes they will burst, leaving the field evenly 
stained with a homogeneous glutinous-looking substance. 
Action of electricity.—lt seems to make little difference, so 
far as the microscope is concerned, whether the continuous or 
interrupted current is employed, as in either case the phe- 
nomena observed are the same in quality. Take bits of tin- 
foil and attach them to an ordinary glass slide, in such a 
way that they are just } inch distant from one another. The 
pieces of foil should be triangular in shape and have their 
pointed extremities turned to one another. The specimen 
should be a drop of newt’s blood diluted with an equal amount 
of serum, both perfectly fresh. They should be intimately 
mixed with a glass rod. 
Depositing a drop of this solution upon a cover-glass, it 
should be inverted and placed upon the slide in such a way 
that it occupies an intermediate position between the bits of 
tin-foil. The ordinary stage clips of the microscope are then 
to be used in holding the slide firmly in position and to press 
upon the tin-foil. The only remaining task is the attaching of 
conducting wires from the electrical instrument, one to each 
clip. The bits of tin-foil are easily fastened to the slide ; they 
have merely to be hammered out fiat, when they will adhere by 
simple pressure. Sometimes it may be desirable to approxi- 
mate the poles. In such cases it is necessary to use two fine 
bits of platinum wire. They should be flattened, and shaped 
like the letter S. Rest them upon the bits of tin-foil, opposite 
to one another and at the required distance apart. The cover- THE BLOOD. 
glass should press on them. Some little mechanical dexterity 
is required to get them in position, and they are apt, after using, 
to become so charged that their action upon the corpuscles 
commences before they are connected with the battery. The 
phenomena at the negative pole are those of an acid; at the 
positive, those of an alkali. At a distance from the line of the 
current, secondary changes occur of a less regular character. 
Halting has devised an apparatus which is somewhat more 
elaborate, but in principle the same. 
Other changes in the red corpuscles.—lf a drop of blood be 
taken from the finger, by pricking with a needle (the triangu- 
lar or glover’s is the best), it will be seen 
after a time that the exterior of the corpus- 
cle is indented or crenated, as this change 
is called. It as well shown in Fig. 20. 
Examination of the circulation in the 
web of a frog’s foot.—Take a medium-sized 
frog and cnrarize kirn by injecting beneath 
the skin, with an ordinary hypodermic syr- 
inge, two drops of a weak solution of curara 
(1—2,000 in water) or a few minims of a 50 per cent, solution 
of chloral hydrate (Schaefer). After a variable time the ani- 
mal will be completely paralyzed, but the circulation will go 
on as before. 
Fig. 20.—Human blood: 
red corpuscles crenated. Kol- 
lett. 
There are many difficulties in the use of curara, depending on the variable 
strength of the drug, the idiosyncrasies of the animal, and other causes that 
We do not appear to understand. A solution which will produce a proper 
amount of paralysis in a frog on one day will rapidly Idll another frog the next 
day. To ensure any reliability of action, it is well to have a specimen of 
which the strength has been properly tested. Then, if time enough is at one’s 
disposal, a weak solution, such as the above, may be injected every hour until 
the symptoms of the drug are apparent. If the subsequent recovery of the 
animal is not of vital importance, the amount may be increased, for the circu- 
lation will often be well shown, even if the animal does not eventually survive. 
My friend, Dr. W. H. Welch, who is in charge of the Histological Labora- 
tory at the Bellevue Medical College, employs a watery solution of curara. 
He keeps on hand a | per cent, solution of the drug ( 1 gramme to 200 c.c. of 
distilled water), and then dilutes it as occasion may warrant to \ per cent., or 
even Ao per cent. (1—500 or 1—1,000). Of this diluted solution he injects four 
or five drops into the dorsal lymph-sac of the frog. A still more dilute solu- 
tion he is often in the habit of using, so that the frog does not come under the 
influence of the drug for an hour or an hour and a half. After twenty-four to 46 
MANUAL OF HISTOLOGY. 
forty-eight hours the animals entirely recover, but if a stronger solution is 
used, he finds the results are frequently fatal, though the animals may survive 
long enough to permit a ready demonstration of the circulation, emigration of 
leucocytes, etc. 
ISTow envelop Ins body in a damp cloth and extend him upon 
a cork plate about a quarter inch thick and large enough to 
support the entire body. Make a small opening in the cork, 
and over it place the web of the frog’s foot, fastening the latter 
by ordinary pins. 
The circulation may in this way be studied at one’s leisure. 
The red and white blood-corpuscles are seen in the arteries, 
veins, and capillaries. While the red bodies pass rapidly 
through the central portions of the vessels, the white creep 
slowly along the walls, altering their shape as they meet with 
any obstruction. Where, however, a small artery divides, it 
will sometimes be seen that the corpuscles, especially the red, 
are caught at the bifurcation ; part bending to go down one 
branch, and part down the other ; taking, in fact, the shape of 
a saddle-bag. Such a phenomenon exhibits the elastic and 
distensile properties of the corpuscle. Apply an irritant, such 
as a weak solution of nitrate of silver, and after prolonged and 
careful watching, the gradual exit of both white and red cor- 
puscles may be seen. This procedure requires extreme pa- 
tience and a co-operation of peculiarly fortunate conditions, 
which are not likely to favor the beginner in microscopy. 
Internal structure of the red corpuscles.—As yet the inti- 
mate structure of blood-corpuscles is a matter little understood, 
though an abundance of theories are rife about it. Klein main- 
tains that these corpuscles, in common with others in the body, 
are traversed by an intracellular network. In the red cor- 
puscles of the newt, especially, he says there is a network of 
fibrils, with an interfibrillar hyaline ground substance, both 
together forming the so-called stroma. The nucleus contains a 
network of fibrils in connection with the network of the cor- 
puscle proper ; the haemoglobin, a colored fluid, is contained in 
the substance of the meshes of the network of the corpuscle 
proper. Drs. Cutter, of Boston, and Heitzmann, of this city, 
also state that there is an intracellular network. The former 
regards it as due to the mycelium of a parasitic growth. 
Dr, Elsberg, of this city, also states that he finds a reticu- 
lar appearance after using a solution of the bichromate of THE BLOOD. 
potash (30 per cent, to 50 per cent, of a saturated solution in 
water). 
Real granules are often present in the corpuscles, as may be 
proved by adding water in large quantity. They will then 
become greatly distended, and bursting, the granules will be 
scattered throughout the field. 
If finely ground vermilion is sprinkled in the liquid, some 
of the white corpuscles will take up the granules, perhaps with- 
out losing their amoeboid character; finally, they may eject 
them after a longer or shorter sojourn. 
According to Boettcher, the human red blood-corpnscle has a nucleus. He 
exhibits it in the following way: Taking a saturated solution of corrosive subli- 
mate in alcohol (96°), he diffuses about fifty volumes with one of blood. The 
corpuscles are deprived of their hsematin, but at the same time are preserved. 
The mixture is frequently agitated, but in about twenty-four hours it is allowed 
to subside, when the superincumbent fluid is poured off and alcohol added. 
By further agitation for another twenty-four hours the corpuscles are thoroughly 
Washed, and then settle at the bottom of the vessel. Prof. Boettcher claims 
in this way to have found three classes of red globules. The first are homo- 
geneous and shiny throughout; the second are clear externally, but granular 
within; the third variety exhibit a nucleus and nucleolus. 
Development of the blood-corpuscles.—In early foetal life 
all the corpuscles are colorless (Klein). According to Balfour 
and Foster, both colored and colorless corpuscles, at least in 
the chick, are developed from solid sprouts of protoplasm, de- 
rived from the middle germinal layer. There seems good rea- 
son, however, to believe that the leucocytes are formed in part, 
at least, from the lymphatic glands, and Klein thinks that 
they are thrown off from the “germinating buds” of serous 
membranes. Later, the red ones make their appearance, and 
for a time are nucleated. The investigations of Neumann and 
Bizzozero, showing that the red corpuscles in the medulla of 
bones are also nucleated, favor the theory that bone-marrow is 
one of the theatres for such corpuscular metamorphosis. 
According to Hayem the production of red corpuscles in the 
blood is accomplished through the agency of Immatoblasts, 
i.e., minute red corpuscles. In convalescence from acute fe- 
vers, or after a considerable loss of blood, these smaller bodies 
may be observed in the blood for a variable time, even some 
weeks. 48 
MANUAL OF HISTOLOGY. 
According to Recklinghausen, the colorless corpuscles may he generated 
from the red corpuscles, but it is probable that they may be formed in the tis- 
sues at many points, and the connective substances through their intimate asso- 
ciation with the lymphatics are capable of manufacturing them in almost any 
quantity. Neither of the two varieties of corpuscles, the red or the white, have 
a cell-wall or outer investing membrane that can be demonstrated, though it is 
not unlikely that the outer layer of protoplasm has greater density than the 
more internal portions. 
White or colorless Mood-corpuscles.—The white blood-cor- 
puscle is much larger, on an average, in the human species, 
than the red. It is rounded in form, and is estimated as varying 
between .0077 and .0120 mm. The average is .0091 mm. (Frey). 
In contour they are apt to be more or less rough, and exhibit 
processes. In some of these corpuscles the nucleus is distinct, 
though when quite fresh a nucleus is rarely seen. If the eye 
of the observer can watch the corpuscle when it is upon a 
heated stage and under suitable conditions, its division may 
be seen. The number contained in the system is variable, as 
we shall see, depending upon a great number of conditions. 
The personal observations of the author do not incline him 
to regard the network which has attracted so much attention 
of late years as satisfactorily shown to exist in living corpus- 
cles, although there is no question but that it has been seen in 
corpuscles after exposure to chemical reagents. 
According to Dr. Richard Norris, there is, in mammals, a third corpuscular 
element which is usually invisible and of the same size as the red ones. Some 
doubt is thrown upon his alleged discovery, by the fact that the method he 
employs is likely to produce artificial appearances, and therefore leads to the 
supposition that the alleged bodies were merely red corpuscles decolorized. 
Mode of counting the Mood-corpuscles.—Thanks to the 
instruments of Malassez, Hayem and Nachet, and Gowers, we 
are in a position to count the red blood-corpuscles with a fair 
degree of accuracy. 
The methods are somewhat different, but are not difficult to 
understand. 
Schaefer describes his plans as follows : In order to separate 
the corpuscles and prevent coagulation, the blood used is first 
diluted to a definite extent—say a hundred times—with a 10 
per cent, solution of sulphate of soda. The mixing can be per- 
formed in a measuring-glass if the blood is in sufficient quan- THE BLOOD. 
tity, but if only a small drop is obtainable, such, for example, 
as is got by pricking the linger, a mixer is better. This con- 
sists of a capillary tube terminating in a bulb, the capacity of 
the bulb between the marks 1 and 101 being exactly 100 times 
that of the tube from its point to the mark 1. A small glass 
ball is inclosed in the bulb, and serves, by its movements, to 
facilitate the mixing. The capillary tube is allowed to fill with 
blood as far as the mark 1; sulphate of soda solution is then 
sucked up as far as the mark 101. As it passes in, it of course 
pushes the blood before it into the bulb, and the two are there 
thoroughly mixed by gentle agitation. 
The next thing is to count the corpuscles in a known quan- 
tity of the mixture. The most convenient plan is that of 
Hayem and. Nachet. A slide is used, having a glass ring } mm. 
in depth, cemented on to its upper surface. A drop of the 
mixture, but not enough to fill the cell so formed, is placed in 
the middle of the ring, and a perfectly Hat cover-glass is so laid 
on that the drop touches and adheres to it without reaching 
the sides of the cell. The slide is placed on the microscope, 
and as soon as the corpuscles have settled down to the bottom 
of the drop, the number in a definite area is counted. If the 
area chosen is mm. square, this will give the number which 
were contained in \ mm. cube of the mixture, and multiplying 
this by the number of times the blood was diluted, the result 
will be the number of corpuscles in £ mm. cube of blood. 
Schaefer thinks that it is more convenient to have the quad- 
ratic markings upon the micrometer glass of the eye-piece than 
upon the slide, which is a practical point. The quadratic 
markings are shown in Fig. 22. To measure any square, it is 
only necessary to take the stage micrometer, ruled in milli- 
metres and decimals, and adjusting the draw tube, make the 
side of one square correspond exactly to an interval of \ mm. 
on the stage micrometer. It will then be convenient to mark 
the tube at this point, and then, in all subsequent work, if the 
tube be kept at this line and a slide is used of the thickness of 
the micrometer and the same lens and eye-piece, the side of a 
square will always be | mm. This method is the one in general 
use. 
Another less frequently employed is that of Malassez, which 
is also described by Schaefer as follows : A little of the mixture 
of blood and sulphate of soda is transferred to a very fine fiat- 
4 50 
MANUAL OP HISTOLOGY. 
tened capillary tube, the capacity of a given length of which has 
been ascertained previously and marked on the slide to which 
the tube is fixed. Thus, in his capillary tube a length of 400 mi- 
cromillimetres represents the Part °f a cubic millimetre 
of the mixture. The counting is performed with the aid of a 
squared ocular micrometer, the microscope tube having been 
previously so adjusted by the aid of a stage micrometer that 
the side of the square shall have the value of one of the lengths 
(400 /i1 for example) marked on the slide. The result of the 
Fig. 21.—Hayem and Nachet’s apparatus for blood-counting, 
counting gives the number of corpuscles in a known quantity 
(tbVp c.mm.) of the mixture, and the number in a whole cubic 
millimetre can therefore be readily determined. 
Dr. Keyes uses a modification of the method of Hayem and 
Nachet, making a dilution of 1 to 250, in order to render the 
counting more easy. In Fig. 21 the pipette, A, is filled up to 
the mark, 5D ; it is then emptied into the glass vessel, F. The 
pulp of the finger of the patient whose blood is to be tested 
should be pierced with a triangular needle (glover’s). Quick 
1 A micromillimetre {/x) = Ttbrs mm. THE BLOOD. 
but firm pressure down the finger will at once force out a drop 
from the punctured spot. The blood must be drawn imme- 
diately into the capillary pipette lest it coagulate. When the 
pipette is full to the mark 2, its point should be rapidly wiped 
clean of any blood adhering to the outside, and the contents at 
once blown into the artificial serum in the cup, F. A little 
suction back and forth clears the tube of any blood-corpuscles 
which may have adhered to the glass within. Both tubes 
should be carefully washed before being put away. 
The mixture is now to be thoroughly agitated with* the glass 
rod, and before it has time to settle, a drop is placed in the 
middle of the cell on the slide, D, care being taken that the 
drop is not large enough to touch any part of the circumference 
of the celL The covering glass, E, should at once be placed 
upon the cell. Should the drop be too large, so that when the 
thin cover is adjusted it spreads out too much, the glass should 
be cleansed and the attempt made anew. Finally, a small drop 
of water or saliva is applied to the edge of the covering glass, 
under which it circulates around the top of the cell, serving to 
hold the cover in place and pre- 
vent evaporation. The slide is 
then put in position and when 
the corpuscles have all settled 
to the bottom of the fluid, the 
counting should begin. The 
following detailed plan is then 
given by Dr. Keyes : 
“It is better to count each 
of the sixteen squares and write 
down its number separately, 
so that in counting the square 
beneath it, should there be any 
doubt about counting a given 
corpuscle lying upon the line, a glance at the number recorded 
for the square above may remove all doubt. Many corpuscles 
will be found lying upon the outside lines bounding the large 
square. I have adopted the rule of rejecting all those lying 
upon the upper and right-hand outside lines (of the large 
square) and counting all those lying on the lower and left- 
hand outside lines. 
Fig. 22.—Blood corpuscles as seen with the 
squared ocular micrometer. Keyes. 
After having thus obtained the number of red corpuscles 52 
MANUAL OF HISTOLOGY. 
situated within the large square, it becomes easy, by a simple 
equation, to find the number in a cubic millimetre. A single 
count, however, exposes to sources of error, and in order to 
approach more nearly to exactness, I have uniformly counted 
the number contained in the large square in five different por- 
tions of the field (sometimes ten), and have taken a mean of the 
whole number of counts as the standard. 
The computation is as follows : The glass cell on the slide 
is i mm. deep. The eye-piece micrometer marks off mm. 
square, therefore the count of red corpuscles (or white, as the 
case may be) must indicate the number contained (in the dilu- 
tion used) in | mm. cube. But } mm. cube is of a c’mm., 
therefore the number counted must be multiplied by 125 ; and 
the blood was diluted by adding 250 parts of fluid to 1 of blood 
(2 c.mm. to 500 c.mm.), therefore the product above obtained 
must be again multiplied by 251 to get the number of corpus- 
cles in a c.mm. of pure blood. Instead of multiplying twice, a 
single multiplication by the product of 125 x 251, 81,876, will 
give the same result.” 
This method should, theoretically, he absolutely accurate, but there are vari- 
ous errors which will unavoidably creep in. First of all, the tubes should be 
verified as to accuracy. This has been done for me at the Winchester Observa- 
tory, of Yale College, by Leonard Waldo, Esq., the astronomer in charge. My 
larger glass tube is slightly different in shape from the one here represented, and 
is marked so that the line at 1 indicates a capacity of 500 cubic millimetres 
(0.5005 grammes of distilled water at 26.4° 0.). The cubical contents of the 
reservoir from the point to the line i = 0.2425 + 0.008 = 2505 grammes = 
250 c.mm., approximately. Accordingly, the marks i and \ indicate i and i 
a cubic centimetre, within a limit of error so small as to be practically insensi- 
ble. The ■ smaller glass tube, which is capillary, is marked 2, 21, 4, and 5. 
The level 5 indicates a capacity of 5 c.mm. The capacity between the pointed 
extremity and 2is 2 c.mm., less a'fa c.mm.; the space between 2 and 2| con- 
tains .55 c.mm.; the space between 2£ and 4 contains 1.45 c.mm.; the space 
between 4 and 5 contains exactly 1 c.mm. (Waldo). The determination of these 
capacities was made by using distilled water, and comparing the weight, when 
filled to the various levels, with the same tube after careful drying. 
These estimates are given to show one of the errors which may be met 
with, and that an instrument, before using, should be verified by some one who 
has special means for determining capacities of this kind. My eye-piece mi- 
crometer was made for me by Rogers, of Cambridge, and the entire field was 
subdivided into squares, so that every portion of it may be counted without 
moving the slide. My method has been practically the same as that of Dr. 
Keyes, except that I prefer diluting with one thousand parts of the diluent, THE H-EMOCIIROMOMETEK. 
and use iodized serum in place of urine. The ordinary J per cent, solution 
of common salt in water will also answer sufficiently well. 
Recent investigations, such as those conducted by Drs. Cut- 
ter and Bradford, of Boston, have established that there is 
great variation in the number of globules of an individual, de- 
pending on various causes, such as the locality from which the 
blood is drawn, the loss of fluids, as by diarrhoea, sweating, 
increased urinary secretion, etc., and even the period of the 
day, week, or year. These general conclusions have also been 
sustained by Hayem, of Paris, in researches which are still 
being prosecuted. 
When one further considers that we have no definite stand- 
ard of comparison; that the instrument is apt to be imperfect ; 
that there is a liability of errors to the amount of 10 per cent.; 
that skill and practice are required in manipulation, it is by no 
means difficult to see that the hsematometer is not calculated 
at present to introduce much scientific precision into medicine, 
unless the most extraordinary precautions are taken in every 
case, and these all duly noted. 
Blood crystals.—The pigment of the blood occurs usually 
in an amorphous form, and is called hsematine. The brownish 
red needles found in extravasated blood are known as haema- 
toidine. 
Hemoglobin also occurs in most mammalian blood, and is 
deposited under the form of rhombic plates. It is estimated 
that about 125 grammes are present in the blood of a healthy 
adult. 
THE HiEMOCIIKOMOMETE'R. 
According to Mantegazza and others, richness in haemoglo- 
bin indicates a corresponding richness in red corpuscles, and 
any special depth of color in the blood may be regarded as im- 
plying a certain given number of red corpuscles to the cubic 
millimetre. While this ratio appears to hold true in health, it 
fails in disease. Thus, a condition which we recognize as anae- 
mia may be almost wholty due to a loss of haemoglobin in the 
corpuscle, or an actual loss of red corpuscles, together with a 
diminished amount of haemoglobin in those that remain. In 
the cachexia of cancer the number of the corpuscles may be 
sustained, but their haemoglobin diminished. In diabetes mel- 54 
MANUAL OF HISTOLOGY. 
litus, on the other hand, there may be an excess of red cor- 
puscles, while there is a diminution of their haemoglobin. In 
anaemia, from hemorrhage, there is an actual loss both of cor- 
puscles and of haemoglobin in those that remain. 
To facilitate the estimation of haemoglobin, an instrument 
has been devised by Malassez and Yerick (Paris), called the 
Ticemochromometer,1 which is easily manipulated, and bids fair 
to establish some facts of practical utility (see Archives de 
Phys., 1877, p. 1). 
It consists of a hand-screen, to which a movable prismatic 
trough, containing a colored tiuid, is attached, and a modified 
Potain pipette. By means of this apparatus the richness of 
the blood in haemoglobin, and the maximum quantity of oxy- 
gen which it can absorb, may be determined. To use the ap- 
paratus the pipette is first filled up to a certain point with the 
blood to be examined, and then diluted with 100 parts of water. 
The reservoir of the pipette is then filled with the diluted 
blood. The screen has two holes; behind one of these the 
prismatic trough is made to slide up and down, the color of the 
fluid contained in it of course varying in intensity, according 
to the extent of the upward and downward motion. Behind 
the other opening the reservoir of the pipette is secured by 
means of a little elastic ring. The screen is now held against 
the light (preferably white light; sunlight is to be especially 
avoided), and the trough moved until the color of the blood 
mixture is matched by its own color. Tlien the figure on the 
scale attached to one side of the trough is read off, and this 
indicates, by reference to the table annexed to the apparatus, 
the points to be determined. If the blood to be examined be 
deeply colored, the aqueous blood-mixture is made in the pro- 
portion of i to 100 ; if it be but slightly colored, in the propor- 
tion of 2 to 100. 
BIBLIOGRAPHY. 
Welcker. Pragervierteljahreschr. XLIV., p. 60. 1854. Zeitsclir. f. rat. Med. 
3, XX., p. 380. 
Sciiultze, Max. Archiv f. mikrosk. Anat. 1., p. 85. 1865. 
Rollett. Strieker’s Manual of Histology. New York, 1873. 
Woodward. Am. Jour, of the Med. Sci., Jan., 1875. N. Y. Med. Rec., Jan. 31,1880. 
1 To be obtained of J. F. Eeynders & Co., New York city. BIBLIOGRAPHY. 
Kelsch. Arch, de Phys. Yol. 11. 1875. 
Keyes. Am. Jour, of the Med. Sci., Jan., 1876. 
Heitzmann. New York Med. Jour., April, 1877. 
Mantegazza. Berl. Klin. Woch., April 1, 1878. 
Banvier. Traite technique d’histologie. Paris, 1877 et seq. 
Hayem. Archives de Poys. 2 Ser., T. VI., p. 201 et seq. 1879. 
Bizzozero, G., and Salyioli, G. Centralb. f. d. Med. Wiss. 16, p. 273. 1879. 
Pouchet. Gaz. Med. de Paris. 14, 16. 1879. 
Cutler, E. G., and Bradford, E. H. Journal of Phys. Yol. I. 1878—1879, 
Boettcher. Archiv f. mikrosk. Anat, Bd. XIV. p. 73. 1817. 
Klein and E. Noble Smith. Atlas of Histology. 1879. 
Elsberg. Annals of the N. Y. Academy of Sciences. Yol. 1., Nos. 9 and 10. 1879. 
(A very extensive bibliography.) 
Satterthwaite, T. E. Arch, of Comp. Med. N. Y. 11. 1880. 
Baxter and Willcock. Lancet, March 6, 13, 20, 1880. 
Bizzozero. L’examen microscopique du Sang. Ann. Soc. med.-chir. de Liege. 
XX. 201-216. 1881. 
Hayem. Contribution a I’etude de la structure des hematoblastes et des hematics. 
G. Ac. Med. de Paris. 6. S., 111. 479-481. 1881. 
Thoma, It. Die Zahlung der weissen Zellen des Blutes. Arch. f. Path. Anat., etc. 
LXXXVII. 201-209. 1882. 
Vibert. Possibility de distinguer le sang de I’homme de celui des mammiferes. 
Arch, de phys. norm, et path. 2. S. IX. 48-58. 1882. CHAPTER IV. 
EPITHELIUM. 
The skin, mucous surfaces of the body and various pas- 
sages in connection with them, are evenly coated with bodies 
of peculiar shape, which are united together to form a cover- 
ing of one or more layers. 
In some places, as upon the external portions of the epider- 
mis, the corpuscles are more or less flattened. Elsewhere, as in 
the ducts of secreting glands and in the trachea and fallopian 
tubes, they are cylindrical, and the free extremities are often 
surmounted by cilia—fine, hair-like processes, which have a 
vibratile movement that propels solid matters, such as sputa 
and ova, in some special direction. In other parts, again, as in 
the collecting tubes of the kidney, near the apices of the pyra- 
mids, a cuboidal variety is found. Intermediate or transitional 
forms are also frequently met with in all parts of the body. 
A characteristic of epithelium which is especially note- 
worthy is that the same species is not found uniformly in the 
same position. Sometimes this mutation of type is governed 
by the physical laws that regulate the growth and development 
of the subject, or it may be a consequence of disease. An ex- 
ample of the former peculiarity is to be noted in the larynx, 
where the ciliated corpuscles of infancy part with their cilia 
from advancing age, or indeed may become flattened. 
As an example of pathological change it is not uncommon 
to find villosities covered with the most beautifully marked 
cylindrical epithelium, springing from the ordinary mucous 
membrane, just where the superficial corpuscles happen to be 
somewhat flattened in their normal state. 
The use to which the part is put has also an important influ- 
ence in governing the shape and other attributes of the corpus- 
cles. Where they are exposed to the drying action of the air, 
to harsk usage, and continued friction, as upon the hands and EPITHELIUM. 
feet, they become flattened, dry, and horny ; in the interior of 
the body, on the other hand, where such conditions do not 
exist, they are succulent and pliable. 
Ordinary flattened or squamous epithelium.—This is best 
obtained by scraping the back of one’s tongue with a blunt 
instrument. The scrapings should then be mounted in equal 
parts of the common salt solution (J per cent.) and glycerine. 
The epithelial bodies may in this way be readily studied. They 
are separate or grouped together in collections of two or more. 
In diameter they vary between and inch. The sur- 
faces are all bevelled, and at the same time are uneven or 
ridged; consequently they overlap one another to a certain 
degree, and the inequalities of one corpuscle fit into those of 
another. The most superficial epithelium is the thinnest, and, 
conversely, the deepest is apt to be the most nearly spheroidal. 
Intermixed in the mucus will be seen the so-called mucous 
or salivary corpuscles. They are not very numerous, but are de- 
tected by the “molecular” or Brownian movement of their in- 
terior. In size they closely resemble the white corpuscles of the 
blood, but, as a rule, exhibit no amoeboid motion ; the white glob- 
ules, on the other hand, rarely have any Brownian movement. 
The surfaces of the epithelia are often so covered with bac- 
teria that they are only recognized with some difficulty. These 
little bodies are wonderfully uniform in size, and are disposed 
in the most regular manner. Looking straight down upon 
them they appear to be minute spheres with a diameter aver- 
aging between and If|f« inch. Closer inspection and 
examination of the corpuscles at their free edges shows that 
the bacteria are in reality rod-shaped, and that adhere to 
the corpuscles by their extremities, standing in such cases 
vertical to the surface. A high power, such as the immersion 
TV, develops this point quite clearly. 
Incidentally the mucin of the mucus may be seen to advan- 
tage in the scrapings of the mouth or tongue. To a drop or two 
add another drop of commercial alcohol and a drop of the or- 
dinary hmmatoxylon solution. The alcohol will coagulate the 
mucin, which then takes the form of filaments and branching 
networks ; the logwood will make them distinctly visible. 
Epithelium from the skin may be studied in one of two 
methods. Take a fresh specimen from the palmar surface of 
the hand or plantar of the foot, freeze it in a section cutter, 58 
MANUAL OF HISTOLOGY. 
take off a thin slice with a knife, immerse for a few seconds in 
a dilute solution of acetic acid per cent.), and then mount in 
glycerine and water; or a similar portion of the skin may be 
steeped in a weak, sherry-colored, watery solution of the bichro- 
mate of potassium (gr. ij.—iij.—f. 3 j.) for several days and then 
hardened in alcohol, first of 80 per cent., then of 90 per cent., 
finally of 95 per cent, strength ; this latter process taking several 
days, and ending when the specimen is thoroughly hard. Sec- 
tions may then be made in the usual way. By the use of acetic 
acid the nuclei will readily be seen in the lower strata of the epi- 
dermis, while the outermost layers have none, or, at least, none 
that can be demonstrated by the usual histological methods. 
Three different strata can now be recognized : 1, the stra- 
tum corneum, or corneous layer, in which the corpuscles are 
flattened, and appear to have no nuclei; 2, the rete mucosum, 
or malpighian layer, immediately underlying the former, and 
composed of cuboidal elements, armed with spines or prickles, 
as they are often called ; lastly, 3, there is tho pigmented layer, 
which overlies the papillae. The bodies of the latter corpuscles 
are infiltrated with particles of melanine, which is the cause of 
the dark color in the skin of the negro and swarthy races. 
Maceration of the epidermis in liquor potassae is an excellent 
method for exhibiting the individual elements; after a few min- 
utes they will swell up and detach themselves from one another. 
It was thought, until quite recently, that these prickle cells interdigitate 
with one another, but Ranvier has claimed that they are continuous with those 
of adjacent corpuscles (see chapter on the Skin). This point is difficult to set- 
tle, as it requires a special method and lenses of high power. Ranvier injected 
a one-fourth per cent, solution of osmic acid into the lower layers of the epider- 
mis, using a hypodermic syringe, and driving the fluid right and left. 
There is a form of flattened and pigmented epithelium that 
may be seen by examining the external surface of the choroid, 
the ciliary processes, and the posterior surface of the iris. In 
the choroid these bodies look like a mosaic of polyhedral cells. 
Such specimens may be permanently preserved by simply dry- 
ing them, and then mounting in dammar or Canada balsam. 
Ciliated epithelium.—The movement of living cilia is readily 
seen. All that is necessary is to take the common frog (Rana 
temporaria), draw out his tongue, and then observing the teat- 
like projections at the posterior part, snip one off. EPITHELIUM. 
This little piece is then to be mounted in a one-fourth per 
cent, salt solution, or serum, and examined. Along the free 
edge of the mucous membrane the cilia will be seen engaged in 
active vibratile motion. The appearance presented by a broad 
expanse of moving cilia has been aptly described as resembling 
a field of grain which is being swept by the wind, though the 
motion is often much more rapid than this comparison would 
imply. It will be seen that various substances, such as blood 
globules, are propelled in a definite direction. When the frog’s 
mouth is open, all solid particles that are lodged upon the 
mucous membrane are carried quietly but inevitably toward 
the gullet, and down toward the stomach. The power of the 
ciliary movement may be estimated, in a measure, by placing 
some light but adhering body upon the anterior portion of the 
roof of the mouth, and then inverting the animal. The sub- 
stance immediately begins to ascend against gravity, and soon 
is wedged in the gullet. The same force, though acting in an 
opposite direction, expels mucus, pus, and indeed all solid 
matters, from the cavities of the human lungs; it also propels 
the ova through the Fallopian tubes into the uterus. In ex- 
cessive catarrh from mucous membranes the epithelial bodies 
may themselves be expelled, so that they are not infrequently 
found with their cilia attached, as in the nasal discharges. After 
death cilia are hard to recognize ; they contract down to little 
knobs on the surface of the cells, and can only be demonstrated 
when the eye looks directly .down upon them. Osmic acid is 
useful to preserve them in their natural condition. Take a fresh 
specimen and immerse it for twenty-four hours in a one-fourth 
per cent, osmic acid solution, and for another twenty-four hours 
in dilute alcohol; then tease and mount in glycerine and water. 
It will be observed that each cilium is a slim, straight rod, which 
is apparently structureless ; they rest upon a band, which, with 
a high power, may be seen to have vertical striations. 
Effect of reagents.—By making use of the moist chamber 
(Fig. 19, p. 42), and placing a drop of chloroform in the cor- 
ner of the cell, it will be seen that the action of the cilia rap- 
idly stops, while, if the chloroform be removed, it will again 
resume its activity. 
If carbonic acid gas is admitted, the action of the cilia will 
at first be accelerated, but subsequently retarded, and eventu- 
ally stopped (Kuehne). 60 
MANUAL OF HISTOLOGY. 
After shutting off the carbonic acid gas and admitting oxy- 
gen, the action will again commence. When the ordinary 
motion has ceased, the gradual application of heat will cause 
it to return ; but if the temperature be raised continuously, a 
point will soon be reached where the excessive heat will cause 
the motion again to stop. 
Columnar or cylindrical epithelium.—This is the epithe- 
lium par excellence of the digestive tract, clothing the mucous 
membrane from the cardiac orifice of the stomach to the anus. 
It is also found at the orifices of the ducts of the large excretory 
glands, such as the liver and pancreas, in the milk-passages of 
the nipple, and in some parts of the generative system. These 
cells are tall and narrow, standing vertical to the surface of the 
mucous membrane. Sometimes they are broadest at their free 
extremity, at other times about the middle, so that when viewed 
from above they appear to be separated from one another. The 
nuclei are rounded, and are either placed about the middle of 
the cell or near the attached border. They admit of consider- 
able variation, however, as to size and shape, some of those in 
immediate contact being broad at one extremitjg and some 
broad at the others ; the free edge also may be uneven. 
Scrape the surface of a frog’s tongue or a rabbit’s intestine 
after washing; the cells will be seen to advantage. Place 
some of the scrapings in a drop of glycerine and water to 
which another drop of dilute acetic acid (p per cent.) has been 
added, and mount. In this way the nuclei will be brought 
clearly into view. The cells closely resemble in their shape 
the columnar variety, except that they have no cilia. Among 
them will almost always be found chalice or goblet cells. They 
lie among the columnar corpuscles, and are usually shorter, 
but broader, expanding in the centre, and terminating at their 
attached extremities in a single or double process. The sur- 
face is cupped. They contain one or more nuclei; whether 
they are a distinctive cell or not is as yet uncertain. Some 
suppose them to be the ordinary columnar cell undergoing 
mucoid degeneration; others that they are not epithelial at 
all. Frey regards them as artificial productions.1 
1 The most rational explanation is that furnished by F. E. Schultze. The intra- 
fibrillar substance is, according to this observer, converted into hygroscopic mucin, 
which swells up. This constitutes a change in the cell which, from being columnar, 
becomes goblet-shaped. The wall finally ruptures, and the mucin is poured out. EPITHELIUM. 
61 
Other varieties of epithelium will be taken up in connection 
with the different organs. As already stated, many transi- 
tional varieties occur, even in direct association with the typi- 
cal forms we have described. 
Structure of epithelial corpuscles.—According to the views 
of Heitzraann, Klein, and others, the substance of the cor- 
puscle is pervaded by a network, the minute fibres of which 
may be seen under a lens of high power. The nucleus or cen- 
tral body is also similarly provided. Within the meshes of 
this network there is a hyaline substance, the abundance or 
paucity of which determines the size of the meshes. 
The “granules,” which have often been described, are, ac- 
cording to this view, the nodal points of the mesh work. It 
is also stated that the epithelial cells sometimes have a fine 
limiting membrane (Klein); but even in such instances it is 
merely a condensation of the outer part of the corpuscle. 
Within the nucleus there are also, according to the same ob- 
servers, fibres, within the meshes of which are not infrequently 
real granules (nucleoli). The epithelial corpuscles are at- 
tached together, either by an interlacement of their processes, 
as in the liver, or by a peculiar cement substance, as in pave- 
ment epithelium, or by a continuity of their processes, as in the 
rete mucosum. 
Recent histological studies have narrowed the field formerly 
occupied by the epithelial bodies, and, in accordance with 
these views, the flattened corpuscles which cover serous mem- 
branes, such as the pleura and peritoneum, will be arranged 
under the connective-tissue series, rather than under the epi- 
thelial. The reasons for this change will be given in a subse- 
quent chapter. On the other hand, the enamel of teeth finds 
a more fitting position among epithelial structures, as it is 
largely if not wholly developed from them. 
BIBLIOGRAPHY. 
Ranvter. Traite technique d’histologie. Paris, 1870. 
Delafield. Studies in Pathological Anat. New York, 1878 et seq. 
Klein and E. Noble Smith. Atlas of Histology. 1879-80. 
Heitzmann. New York Medical Record, July 81, 1880. p. 133. 
FreV. The Microscope and Microscopical Technology. New York, 1880. CHAPTER V. 
THE CONNECTIVE SUBSTANCE GROUP. 
MUCOUS OR GELATINOUS TISSUE ; ADENOID TISSUE ; NEUROG- 
LIA ; FAT TISSUE ; FIBROUS TISSUE PROPER ; CORNEAL TIS- 
SUE ; INTERMUSCULAR TISSUE ; TENDON TISSUE ; ELASTIC 
TISSUE. 
The term connective substance was first proposed by Reich- 
ert in 1845, and is now applied to a class of animal tissues whose 
offices are very important in the economy. Prominent among 
them is bone, which forms the solid framework of the body, 
gives it strength, and supplies points of attachment for muscles 
and tendons; another group comprises the ligaments, which 
assist in holding the bony parts, and also some organs, in their 
proper relations ; others again, of a more delicate nature, fur- 
nish support or protection for epithelial bodies, blood-vessels, 
and nerves. Just at the present time the histology of connec- 
tive substances has an important bearing on many points that 
relate to inflammation, degeneration, and the development of 
certain new growths, and it is therefore desirable to have a clear 
conception of them. This object is best effected by studying 
each variety separately, not only in its normal condition, but 
under the changes it exhibits when acted on by the factors that 
are concerned in the processes of disease. 
It is a property of these substances that they supplant one 
another at different times or under peculiar circumstances. As 
an example, the hyaline cartilage of young life may change 
into true bone in old age, while, on the other hand, there is 
always a tendency for fully formed tissue, if inflamed, to re- 
vert toward the embryonic type. 
The connective substances may be subdivided as follows: 
1, mucous or gelatinous tissue; 2, adenoid tissue; 3, neurog- THE CONNECTIVE SUBSTANCE GKOUP. 
lia; 4, fat tissue; 5, fibrous tissue proper; 6, corneal tissue; 
7, intermuscular tissue; 8, tendon tissue; 9, elastic tissue; 
10, bone; 11, cartilage; 12, cement; and 18, dentine. The 
word connective tissue was first proposed by Johannes Mueller, 
and is sometimes used as synonymous with connective sub- 
stance, but erroneously. The former is merely a variety of the 
latter, and is usually intended to indicate one or other of the 
flexible connective substances that form the interstitial material 
of the body, and in that sense we shall use it for convenience 
sake, but without implying any special histological character. 
In precise histological descriptions it is always best to use 
the special name of the variety intended, such as mucous tis- 
sue, adenoid tissue, and the like, where the structure happens 
to be known. 
It is also well to state here that the term “cellular” tissue, 
found in many of our anatomies, is apt to mislead the student. 
The word “cellular” has no reference to cells, i.e., corpuscles, 
but to the large cavities or spaces that exist in all loose connec- 
Fig 23.—Gelatinous or mucous tissue. Human umbilical cord. 
tive tissues, of which the subcutaneous is an example. These 
spaces are easily seen by the naked eye, when inflated with air. 
Mucous or gelatinous tissue.—This is the most simple 
form that is met with. It is seen to great advantage in the 
embryonic umbilical cord, which also contains several other 
varieties of connective tissue. 
The following method has been found best suited to demon- 
strate it. Take a small piece of cord at about the third month 
and immerse it a few weeks in Mueller’s fluid ; make a thin sec- 
tion through the very soft gelatinous part, then soak it a few 
minutes in distilled water, to which subsequently a few drops 64 
MANUAL OF HISTOLOGY. 
of acetic acid are to be added so that the solution shall not con- 
tain more than 1 per cent, of acid, and then mount in glyce- 
rine. It will then be seen that the softest portion contains 
numbers of irregularly-shaped, thin plates, some provided with 
an oval, flattened nucleus, others having none that are appa- 
rent (Fig. 23). Some of these flattened bodies anastomose by 
these processes with those of other plates, others are quite free. 
The substance lying between the cells, the intercellular sub- 
stance, is quite homogeneous, or slightly granular, in the softest 
portions, and has at first no defined fibrillation. In the neigh- 
borhood of the former tissue, lines of fibrillation occur, while at 
the same time these flattened bodies become smaller, although 
they are still flattened (Fig. 24,5). Mucous or gelatinous tissue, 
Fig. 24.—Connective tissue in an advancing stage of development. From the umbilical cord. 
« 
as it is seen in the umbilical cord of an embryo, is properly an 
embryonic or developmental form of connective tissue which is 
never found in normal adult life. All the phases of develop- 
ment may here be seen, from the most primitive, comprised in 
Wharton’s jelly, to the firm, fibrous fascicles that encircle the 
vessels. 
Properly speaking, the true mucous tissue is, as its name 
implies, a viscid material, and, indeed, is much like half-set 
glue, in which the corpuscles are scattered with little or even 
no cohesion. 
The intercellular substance differs from albumen in not con- 
taining sulphur ; from chondrin and gelatin, in not being pre- 
cipitated by boiling, tannin, or the bichloride of mercury. THE CONNECTIVE SUBSTANCE GROUP. 
At an early stage there are no marks of fibrillations in the 
intercellular substance, but later fibrils are seen in the vicinity 
of the corpuscles, and are some of the early signs that organi- 
zation of the tissue is commencing. 
The corpuscles at the same time become smaller, and about 
the central body or nucleus we see a delicate expansion (Fig. 
24 a), which is the envelope of the connective-tissue corpuscle— 
a film of great tenuity. Klein believes that in these corpuscles 
there are two portions, a granular or firmer part continuous 
with the processes, and a delicate expansion that is hardly 
visible. It is certain that the connective-tissue corpuscle is 
frequently in connection with one or more of its fellows by a 
mutual anastomosis of processes. The fibrillation appears to 
be at first limited to certain areas about the cellular elements, 
so that the long, flattened and pointed lamellm of fibrous tis- 
sues on which the corpuscles are attached look like large cor- 
puscles with correspondingly large nuclei. Using a camel’s- 
hair brush and pencilling off the specimen under examination, 
after soaking in a 10 per cent, watery solution of common salt, 
the apparent nuclei with their delicate envelopes are partially 
(Fig. 24 h) or wholly removed. We then see small strips of 
more or less fibrillated tissue, having no central body that can 
be recognized, even with the use of strong staining solutions. 
These and similar observations tend to establish a conviction 
that the fibrillated portion arises from the soft, gelatinous ma- 
terial by a process of fibrillation inaugurated by the presence 
and under the formative action of the connective-tissue cor- 
puscle. It is not impossible that the fibrin of the blood, which, 
though fluid in the blood-current, is often known to be de- 
posited in delicate filaments, may contribute largely, if not 
wholly, to the formation of the fibrillse. As the tissue becomes 
firmer, the little plates with their anastomosing branches form 
a loose network which separates the fibrils into distinctive 
bundles or fascicles, and encircles them more or less completely. 
There is another view which is offered as an explanation of 
the process by which connective tissue becomes organized. It 
is this. The change is derived wholly from the corpuscles. 
Some of them split up into fibrils, constituting the fibrous 
part of the tissue; the others remain, and are developed into 
connective-tissue corpuscles. This view has the support of 
excellent histologists. 66 
MANUAL OF HISTOLOGY. 
The white corpuscles of the blood are pre-eminently suited 
for building tissue. When blood is organized, which occurs 
not infrequently, the white corpuscles at once assume an im- 
portant role, while the red are soon melted down into a homo- 
geneous mass, that is usually absorbed. This change is ob- 
served under various pathological conditions. 
Fibrous tissue.—This substance, which is also known as 
fibril!ated connective tissue, is the fully developed material 
that has just been described. It occurs either in parallel 
Fig. 25.—Reticular form of connective tissue. From the human umbilical cord. 
bundles or fascicles, in interlacing lamellae, or as a fenestrated 
material containing larger or smaller openings. A special va- 
riety, the reticular, is seen to great advantage in the umbilical 
cord of an infant at birth (Fig. 25). 
If a cut be carried through the spongy portions of the cord, 
it will be seen that the tissue is composed of bright, shining, 
branching bundles, d, superimposed upon which are a num- 
ber of oval, flattened plates, a, at intervals; about them is THE CONNECTIVE SUBSTANCE GEOUP. 
a delicate envelope, h, which appears to be highly elastic, so 
that it will stretch or relax, according as the networks are 
compressed or dilated. By teasing with needles or immersion 
for a few days in a 10 per cent, watery solution of common 
salt, these corpuscles can often be separated from the bundles, 
and then they will be seen to form a connected system. When 
entirely isolated from one another, they often appear spindle- 
shaped. That this is not their character may be shown by 
passing a current of fluid through the specimen—a method 
already described under the name of irrigation. It is accom- 
plished in this way : having affixed small strips of filter-paper 
to the edges of the cover on either side, and moistened one side 
with fluid, the excess will be absorbed by the other slip, caus- 
ing a current by which the corpuscles may be made to roll 
over. We then learn that they are disks of an irregularly 
flattened form, having longer or shorter processes (c, c, Fig. 
25)—variations in form which seem to depend, in a great 
measure, upon the tension to which they are exposed, and the 
position they occupy in the tissue. This explanation will 
serve to show why all measurements of such corpuscles are 
merely approximative, and have but little value. 
They are shrunken by immersion in alcohol, swollen by the 
imbibition of water, are drawn out into long, flattened spindles 
when the tissue is put on the stretch, or become rounded, per- 
haps nearly spherical, during relaxation. They may assume 
almost any form as the result of pressure. 
The nucleus may be regarded as more of an exception to 
this rule; at any rate it seems that in fresh specimens, when 
the substance has been swollen by immersion in water, it is 
always oval and flattened. 
The bundles upon which these bodies lie are somewhat 
cylindrical in form, branched, and composed of separate fila- 
ments, that can be separated by Mueller’s fluid, or a 10 per 
cent, watery solution of common salt. 
Two other forms of corpuscles may also be noticed: (1) the 
kind observed by Waldeyer, and called plasma cells, and 
thought by him to be corpuscles peculiarly prone to take up 
fat to make fat tissue, bodies four or five times the size of 
a lymphoid corpuscle, and rounded in form, containing a cen- 
tral body ; and (2) the ordinary lymphoid corpuscles, seen at 
times in all tissues. 68 
MANUAL OF HISTOLOGY. 
The form of fibrous tissue that occurs in parallel lamellae is 
well shown in the mesentery of the frog, and in serous mem- 
branes generally. No great difficulty will be met with in pre- 
paring this tissue, for it is only necessary to remove it from the 
frog in the fresh state, acidulate it in a weak (1 per cent.) 
watery solution of acetic acid, and mount it in glycerine. 
It will be seen that these so-called spindle-cells are really 
flattened plates, when viewed flat-wise, and generally irregu- 
larly quadrilateral, though the form varies somewhat in each 
instance. 
It is not improbable that some which appear spindle-shaped, 
and lie in the interfascicular spaces, have a double office, one 
of which is to guard the nutrition of the tissue, and the other 
to form a partial lining of a lymphatic channel. The researches 
Fig. 26.—Connective tissue in the mesentery of the frog. 
of Klein tend to establish this double relation, for they show 
that these corpuscles lie in the walls of the lymphatic radicles, 
which are themselves in direct communication with the perito- 
neal cavity by breaks in the endothelial connective-tissue cor- 
puscle coating and in actual apposition with the endothelial 
elements of the serous membranes. 
During the last few years there has been a tendency to regard the serous 
membranes, especially such as have large openings and slight reticula, as 
having no connective-tissue corpuscles, other than the endothelial, which form THE CONNECTIVE SUBSTANCE GROUP. 
a covering over tliem. In the larger trabecles, however, there are connec- 
tive-tissue corpuscles, in addition to those just mentioned; they are well 
seen in profile, interposed between the bundles (Fig. 26). 
Adenoid tissue (Fig. 27).—Adenoid tissue is the name given 
to the delicate substance that forms the framework of the lym • 
phatic glands. It consists of fibres in networks which form an 
Pig. 27.—Adenoid tissue from a human lymphatic gland. 
intricate texture, that is filled with the rounded bodies com- 
monly known as lymphoid cells. It is exceedingly difficult to 
analyze these tissues, because it is not easy to demonstrate any- 
thing that conveys to the eye our idea of a cell, i. e., excepting, 
of course, the lymphoid corpuscle. The best mode of proced- 
ure is the following; Take a lymphatic gland—such as the in- 
guinal in the early stage of inflammation; harden at first, in 
Mueller’s fluid, and then in ■alcohol, and make sections through 
it. 
On viewing such a specimen under the microscope it will 
exhibit a delicate meshwork, packed with lymphoid corpuscles 
(Fig. 27, a). Now, if we take such a section and agitate it in a 
test-tube with water for a considerable length of time, and then 
place it upon a glass slide, pencilling it with a camel’s-hair 70 
MANUAL OF HISTOLOGY. 
brush, most of the lymphoid cells will be removed, and the 
delicate network, c, will be very thoroughly exposed. 
It will be seen that, at certain parts of this meshwork, there 
are flattened bodies, b, of small size, lying upon the larger 
cords of the meshes. It has been held by Klein and other his- 
tologists that the reticulum is made of branching corpuscles ; 
but this statement must be modified. In some instances the 
appearance of netted corpuscles is well seen in those portions 
of the glands that are regarded as the lymph passages, where 
the adenoid tissue forms the framework of the part. The net- 
work seems to be comprised of delicate, silk-like cords, enclos- 
ing vast numbers of lymphoid corpuscles, and exhibiting, at 
the nodal points of the meshes, flattened corpuscles. These 
delicate fibres, however, are often replaced by heavy trabecles, 
c, such as are seen in the figure, and after continual inflamma- 
tions the diameter of these latter may be found greater than 
that of the spaces. 
In these latter instances it is often difficult to find any cor- 
puscular elements that may not be separated from the fibres ; 
and, indeed, large areas of these fibrous networks may, by dil- 
igent pencilling with a camel’ s-hair brush, be swept clean of 
corpuscles. But neither this rough method, nor agitation in a 
test-tube, will always succeed in separating all the corpuscles 
from the fibres, even after an immersion in common salt solu- 
tion for many weeks. The sum of the whole matter is, that 
adenoid tissue does not generally consist of a network of 
branching corpuscles, as has been claimed, but rather of a net- 
work of fibrous cords, on which the corpuscles are superim- 
posed ; they may anastomose, but this point seems difficult to 
demonstrate in most cases. 
Possibly higher powers than those now in use, or some new 
method may solve the question. Where the fibrous networks 
have attained some thickness, there is no doubt that we find 
the ordinary flattened connective-tissue plates lying on the 
bundles and surrounded by a delicate envelope. 
Neuroglia (Fig. 28).—But a short time since it was not 
known positively whether the delicate, supporting substance of 
the nervous system, especially of the brain, was granular or 
fibrous. Even after Virchow insisted that this substance was 
like the other tissues, known as connective, doubt was thrown 
upon the matter, for the defining power of most objectives then THE CONNECTIVE SUBSTANCE GROUP. 
used was insufficient to make out such delicate objects. At 
the present time the actual existence of a network is hardly 
called in question, for it may be demonstrated with really good 
glasses, such as some of the immersion lenses (No. 10) of Hart- 
nack’s system, and, indeed, by other lenses made both at home 
and abroad. As to the question of the corpuscular elements 
there is more doubt, and it can hardly be said that their exact 
form and shape have been definitely agreed upon by histolo- 
gists. We find, it is true, that where there is a considerable 
deposit of connective mate- 
rial along the central canal of 
the spinal cord, we have the 
ordinary fibres and corpuscles 
already described, and so, too, 
near the surface»of the con- 
volutions. When, however, 
we examine the supporting 
substances of the white and 
gray masses there is less cer- 
tainty. The actual condition 
may be tolerably well seen 
by adopting the following 
plan. Place any portion of 
the brain or cord a few days 
in a weak solution of bichro- 
mate of potash (5 per cent.) 
Fig. 28.—Human brain showing neuroglia. 
or Mueller’s fluid, then immerse it in alcohol until hard ; make 
thin sections and stain for twenty-four hours with the follow- 
ing solution of haematoxylon: haematoxylini, gr. lip ; aluminis, 
Ij. ; aquae, § viij. ; mix and strain. 
’ Wash in distilled water and mount in glycerine, tease with 
needles and examine with a high power; there will then be 
little difficulty in seeing that the delicate supporting substance 
of both gray and white matter consists of fibres. They may 
even be distinctly isolated, for the coloring matter darkens them 
somewhat and they become hardened at the same time so as to 
be somewhat stiff and unyielding. It will be seen that many 
fibrils are disposed in parallel rows which perhaps can hardly 
be called bundles, but rather thin laminae; other similar fibrils 
cross them at various angles, giving to the whole, with a 
moderately high power, the appearance of a very delicate 72 
MANUAL OF HISTOLOGY. 
meshwork, a. It does not appear as if the fibrillse anastomose 
with one another, though this point cannot now be definitely 
settled. It must be stated that some of these fibrils are possi- 
bly nerve-elements, and yet this is doubtful, because they do 
not even seem to be connected with the nerve-fibres 1 that are 
distinctly shown by this method of preparation. 
Granular appearances are always noted in the brain, which 
is to be expected when cross-sections are made of the delicate 
fibrillse. Three kinds of corpuscles are met with in the brain 
and medulla. The first are the variously shaped ganglionic 
corpuscles or cells, Fig. 28, b,l),h ; secondly, the ordinary 
lymphoid cells, c, c, which are generally seen to have a pale 
envelope about them ; lastly, smaller corpuscles, d, d, of irre- 
gular shapes, and many of them undoubtedly flattened and 
appearing to have branching processes. They may be found 
in considerable numbers, and can be isolated so that there is no 
doubt that they exist. 
The fibrillse of the neuroglia do not differ substantially in 
size from the fibrillse of fibrous tissues elsewhere. 
Tendon-tissue (Fig. 29).—Tendon-tissue may be well studied 
in the gastrocnemius of the 
frog. It is prepared like 
the preceding. If, how- 
ever, it is desirable to show 
the nuclei in adult tissue, 
it is well to use nitrate of 
silver. Cut a thin section 
of a fresh tendon and ex- 
pose it for a few minutes 
in a i per cent, solution 
of nitrate of silver, until 
the section is turbid or 
milky, then place in the 
sunlight, and in a few min- 
utes the turbid color will 
give place to dark brown or black, owing to the deposit of 
silver, and the tissue may then be mounted in glycerine and 
examined. 
Fig. 29.—Tendon-tissue from the frog. 
This method will show the corpuscular bodies to advantage. 
1 To avoid confusion they are not represented in the drawing. THE CONNECTIVE SUBSTANCE GROUP. 
In some cases better results are obtained by the use of chloride 
of gold. The method is as follows : Freeze a small portion of 
a tendon, then make the thinnest possible section, acidulate it 
slightly and immerse in a \ per cent, solution of chloride of 
gold until a strong yellow color has been obtained, then soak in 
a \ per cent, solution of dilute acetic acid and expose to the 
sunlight until a purple or reddish color has been obtained. 
This will take a variable time, and is not always successful, for 
reasons which are not easy to understand. 
At considerable distances from one another there will be 
seen small dark bodies, which are the corpuscles already de- 
scribed. It is difficult to determine whether or not these cor- 
puscles are connected together. To isolate them, take a small 
piece of young tendon-tissue, immerse three or four days in a 
10 per cent, solhtion of common salt, and then tease. In this 
way the cells may be liberated, and they will prove to be irre- 
gularly flattened plates. 
Sometimes they lie at the intersection of several bundles 
and then have separate expansions for each bundle ; the plates 
then lie at various angles with one another, and if one be seen 
edgewise it looks as if the corpuscle proper were traversed by 
a line. 
Silver or gold, the latter especially, is generally necessary 
to show the corpuscles in old tendons. The same method 
shows the fibrillated tissue to advantage. The large tendon 
bundles are often covered with endothelium (connective-tissue 
corpuscles), which are continuous and form a complete invest- 
ment. 
For the smaller bundles the tendon-corpuscles do not by 
any means form a connected sheath. In very young tendons 
they are quite near to one another, though even at this time 
they only form a partial investment for the bundles ; but as 
the tendon grows older the corpuscles become smaller, with- 
draw from one another, and sometimes almost disappear. 
Tendon bundles, like other forms of connective tissue, are 
often encased in a transparent, delicate membrane, not unlike 
the sarcolemma of striped muscular tissue. It is well shown 
by immersing the tendon in a dilute solution of acetic acid. 
Fat tissue.—The ordinary fibrillated connective tissue often 
becomes the deposit for oil, which fills the corpuscles, making 
them swell out enormously. This is fat tissue. An excellent MANUAL OF HISTOLOGY. 
way of .showing it consists in making a section through fat tis- 
sue that has been hardened in alcohol or Mueller’s fluid, or both. 
The phenomena will, in this way, be well shown. After im- 
mersion in an acid solution, it will be seen that the fatty acids 
crystallize in the centre of the sac. 
The nature of the evidence that fat corpuscles are really the 
altered corpuscles of the fibrous tissues is as follows: They 
occupy the same position, being in rows, between the bundles, 
just as the other corpuscles that we have mentioned ; a few oil 
drops at first appear, then others, until finally they coalesce 
into a single large drop, which fills the corpuscle ; if fat tissue 
be pressed, and the oil escapes, the walls of the fat-corpuscles 
collapse, and then the flattened nuclei may be observed on the 
side of the cell-body. 
Waldeyer believes that there is a peculiar corpuscle, three 
to five times the size of the lymphoid, and roundish, which is 
especially prone to take up fat, and be converted into a fat- 
corpuscle. 
This body, known as thqplasma cell, is the second element 
that forms the fat-cell. The change is said to occur only occa- 
sionally, and under favorable conditions of alimentation 
(Klein). 
The same author states that there is also a third way in 
which fat is formed : In many parts of serous membranes, espe- 
cially in connection with the large vessels, there appear ‘‘no- 
dules or cords, which are made up of multiplying connective- 
tissue cells.” The cells increase, the matrix is converted into a 
network, lymph-corpuscles appear, the tissue is supplied with 
arteries, veins, and capillaries, and resembles lymphatic tissue. 
Sometimes these structures persist as they are ; in other cases 
they are converted into fat-tissue. 
Ranvier recommends the following plan of demonstrating 
fat-tissue ; He injects beneath the skin a weak solution of os- 
mic acid (1-1000). The connective-tissue corpuscles may be 
seen to be more or less filled with oil-globules. 
The property of taking up oil is not peculiar to these cor- 
puscles already described, but belongs, physiologically, to the 
liver, to adult cartilage, the glandular elements of the female 
breast during lactation, and the glandular epithelium of the 
sebaceous glands. 
Intermuscular tissue.—It has been claimed by some that THE CONNECTIVE SUBSTANCE GEOUP. 
there is a form of spindle-cell in the intermuscular tissue of the 
frog’s thigh. This, however, is apparent rather than real. We 
find broad plates, in which are oval, flattened bodies, placed at 
certain distances apart (Fig. 31). These, seen in profile, appear 
spindle-shaped. There is something peculiar about such 
bodies, for they seem to bear a close relationship to the elastic 
networks, a, so that, in some cases, it appears as if the flat- 
tened central bodies were directly connected with the elastic 
fibres, as stated by 8011. 
In many instances these elastic fibres lie upon the plates, b, 
which themselves rest in a homogeneous, intermediate, and 
apparently structureless substance. 
This tissue is therefore similar, in some respects, to mucous 
tissue. 
Corneal tissue.—The cornea consists of thin, fibrous bands, 
each one partly anastomosing with its adjacent neighbor. 
Between them are well-marked corpuscles lying in clefts—the 
corneal spaces. 
The term corneal corpuscles, however, is even now applied 
to the spaces by some of the best-known writers, and it seems 
evident that there is doubt as to whether real corpuscles exist 
or not. Recently the subject has been restudied by Waldeyer, 
and the author has been able to verify his conclusions in a 
great measure, both as to the character of the corpuscles and 
the spaces in which they lie. 
In general, these bodies appear, as stated by Waldeyer, to 
be flat, having a considerable amount of protoplasmic material 
about their nuclei (Fig, 30), though in the direction of the per- 
iphery they gradually taper off into thin expansions, which are 
nearly homogeneous, and extending from them are distinct 
processes which in part unite with those of other corpuscles, 
not materially differing in this respect from tendon-tissue and 
the other varieties. In them is the same flattened, oval body, 
which, when seen on the side, is rod-shaped, b, and is sur- 
rounded by an irregular envelope that assumes almost any 
shape. Thus the corpuscles are not always flat, though they 
are usually so. Their shape depends upon many different 
causes, such as the method of preparing the tissue, the amount 
of laceration to which it is subjected, etc. The best method of 
examining the cornea consists in preparing it by the gold me- 
thod, already described. 76 
MANUAL OF HISTOLOGY. 
After the tissue has been properly stained, which is known 
when it has taken a mauve or violet tint, as already stated, the 
specimen should be allowed to stand in the sun. Thin lamel- 
lae are then torn off with the forceps and mounted in dammar 
varnish or Canada balsam. 
After the specimen has been made thoroughly transparent 
by soaking in oil of cloves, it will then be seen that there are 
bodies within certain well-defined areas—the corneal spaces, 
Fig. 30.—Corneal tissue. From the rabbit. 
as they have been called by Recklinghausen and others. These 
bodies are disposed at quite regular intervals throughout the 
cornea, and are generally flat with rounded contours, though 
often they have processes extending from them in various direc- 
tions. In the accompanying drawing the spaces may be dis- 
tinctly seen, as well as the variously shaped corneal corpuscles. 
One, <?, is crowded into the prolongation of a corneal space, 
while another, b, is connected by its processes with a neighbor- 
ing corpuscle. One corneal space, a, is entirely empty. These 
differing conditions are in a measure due, probably, to the THE CONNECTIVE SUBSTANCE GROUP. 
laceration of the tissue in preparing it, some of the bodies 
haying been torn out and others forced to the side of the cor- 
neal space. There seems to be a very general agreement that 
the intercellular substance may be separated into indepen- 
dent fibrils ; but I have seen no decisive proof bearing on this 
point. 
Elastic tissue.—This differs from the other forms micro- 
scopically and chemically, though it is often combined with 
them in the body. It is also convenient to class it by itself 
for other reasons, chief of which are, that its corpuscular ele- 
ments have not yet been definitel}" shown in adult tissue. 
Virchow, some years ago, stated that this tissue, as well as 
other connective substances, was composed of networks, the 
substance of the fibres containing certain markings, and he in- 
ferred that these latter might be the corpuscles of the tissue. 
Elastic fibres were, however, according to him and others, noth- 
ing but the ordinary fibrous tissue condensed. Each fibre was 
hollow and capable of conveying the nutritive Juices. 
Henle, in his earlier writings, regarded the elastic fibres as 
emanating from the nuclei, of which, in fact, he stated they 
were prolongations. Subsequently, he seems to have believed 
that the fibres originated in the basis substance. 
Reichert could not trace the connection between the nuclei 
and the elastic fibres, and, when the latter had formed, the 
former had disappeared. 
8011, however, distinctly stated that the elastic fibres, each 
one constituting an “elastic cord,” arise from the plate-like 
cells. 
Ranvier examined tendon-tissue, as mentioned before, but 
he was only able to find the elastic fibres after boiling the tis- 
sue from eight to ten hours. It is proper, however, to add 
here, that elastic fibres are very uncommon in tendon-tissue, 
at least they have not often been observed. 
The fibres of the elastic substance are pretty readily re- 
cognized by the fact that they are not colored by carmine or 
hsematoxylon, and do not swell with acetic acid ; they branch 
dichotomously, these branches forming, with similar branches 
of other elastic fibres, networks. 
Elastic tissue prevails in the ligamentum nuchm of the ox, 
in the serous membranes generally, and in the subcutaneous 
connective tissue of the skin, as well as in the delicate inter- 78 
MANUAL OF HISTOLOGY. 
muscular substance already described. It will generally be 
found that where this material occurs in bundles it is not be- 
cause there are no meshes, but rather because they are com- 
pressed laterally, so as not to be apparent unless most carefully 
teased apart. When such fibres are broken off, their extremi- 
ties curl up ; further, the fibres are unaffected by being boiled 
in solutions of strong acids and alkalies, such as 35 per cent. 
Fig. 31.—Elastic tissue networks. From the frog. 
solutions of caustic potash, or nitric acid (standard prepara- 
tions commonly used in laboratories), unless the action is pro- 
longed for a considerable time. These networks are beautifully 
shown by taking the mesentery of the frog when slightly con- 
tracted after immersion in acetic acid. The fibrillated connec- 
tive tissue will then swell up and become invisible, while the 
elastic fibres are unaffected. 
The ligamentum nuchse also affords an excellent oppor- 
tunity for studying this tissue by itself. To render the work 
more easy, the specimen may be allowed to soak a few days in 
a 10 per cent, watery solution of common salt, so that it may 
be the more easily teased. In the subcutaneous connective 
tissue of the skin the elastic fibres are well shown by luuma- 
toxylon preparations. Being unaffected by this staining solu- 
tion they appear as bright, silk-like cords, which lie in close 
apposition with the wavy bundles, and the branches arch over 
the bundles, to anastomose with corresponding branches of 
other bundles, so that in this way meshes are formed. Some 
writers have spoken of little knobs at the nodal points of the 
meshes, but these appearances have been illusory. 
Kecklinghausen seems to have believed with Virchow, that 
the elastic fibres contain peculiar nuclei of their own, which in THE CONNECTIVE SUBSTANCE GROUP. 
adult tissue become extremely small, and are represented by 
the dark markings seen in them. Thin, of London, has claimed 
that they originate in branching corpuscles, which by their 
coalescence form the network, and the remains of the nucleus 
may be shown by haematoxylon. These markings may, it is 
true, be seen in the ligamentum nuchae of the ox, but it is 
doubtful whether they are nuclei or mere clefts in the tissue. 
Examination by the author, with such high powers as Gund- 
lach’s No. 15 immersion, and Wale’s TV, have failed to clear 
up the matter. 
Good examples of human elastic tissue are found in the 
sloughs of ulcers and in the sputa of phthisical patients. 
In some portions of the body these networks are stouter, 
as in the bronchi and trachea ; here they almost form a layer 
by themselves ; some of the fibres are even said to have a 
sheath. 
There is a variety that has been called, by Henle, perforated 
membrane. It is found in arteries and veins. The fibres are 
broad and the meshes very small. There are also “continuous 
elastic membranes.” They are made up of fibrils, react chemi- 
cally like elastic tissue, and have no meshes. Such is Bow- 
man’s elastic membrane in the human cornea, which is very 
distinct in man, also Descemet’s membrane—the posterior 
elastic membrane of the cornea. 
In various parts of the body, beneath the epithelium, there 
are other elastic membranes which will be noticed in their 
proper places. The elastic membrane, made ,of endothelium, 
and forming the basement membrane of gland-ducts, must not 
be confounded with those first described. 
The growth and development of connective tissue varies ac- 
cording to the particular^type. It is probable, however, that 
all the corpuscles are first round, but soon become flattened 
and have a delicate envelope (Fig. 32, b). 
About this is a further lightly attached investment, which, 
uniting with those of other similar bodies, is the commence- 
ment of the intercellular substance. At first the plate-like 
bodies lie in niches, as it were, in the intercellular substances, 
and if one is brushed out it leaves a socket behind it (Fig. 32, c). 
They are often arranged in rows, as in the drawing, which was 
taken from a fibroma of the scalp. As the intercellular sub- 
stance increases the corpuscles become smaller, while imme- 80 
MANUAL OF HISTOLOGY. 
diately under them thin laminae are formed, probably from 
the effused fibrine—the commencement of fibrillation. 
As the corpuscles become smaller their envelope shrinks, 
and they recede from one another. Yet, in many cases, they 
may retain connection with one another by means of their pro- 
cesses. In advanced life these cor- 
puscles are generally more or less 
flattened, but their form is also con- 
siderably modified by the age of the 
tissues and various mechanical alter- 
ations to which they are subjected, 
according to the particular locality 
in which they occur or the province 
they have to fill. 
By referring to Fig. 32 it will be 
seen that the delicate protoplasm, b, 
has processes which come clearly in- 
to view where the corpuscles are iso- 
lated. 
Pavement endothelium {epitheli- 
um).—From the views that have been 
advanced it is plain that we are pre- 
pared to abandon the old idea that the 
mesentery, peritoneum, the pleura, 
endocardium, serous cavities, and ten- 
dinous sheaths are lined with epithe- 
lium. It is becoming more and more 
evident from studies in the lymphatics that they are lined with 
connective-tissue corpuscles, which, on the one hand, are in 
actual continuity with the interfascicular connective-tissue cor- 
puscles, and, on the other, with the pavement corpuscles of 
the serous cavities. It is but a step farther and in the same 
direction to trace the endothelium of the endocardium out 
through the arteries and veins into the capillaries and recog- 
nize the connective-tissue corpuscle as the one cellular element 
of all these tissues. The special methods by which these parts 
are studied may be found described in the chapters more es- 
pecially devoted to these topics. Nitrate of silver and chloride 
of gold are still prominent among the reagents that demon- 
strate them most distinctly. 
Fig. 32.—Development of, fibrous tis- 
sue. Fibroma of the scalp. 
Ehrlich has recently described peculiar connective-tissue BIBLIOGRAPHY. 
corpuscles, which he previously supposed to be identical with 
Waldeyer’s plasma cells, but which he is now inclined to re- 
gard as a distinctive group of bodies. They are characterized 
by a special power of intense coloration in specimens treated 
with certain of the aniline dyes. Red and violet colors appear 
to be best suited to reveal the presence of these bodies, called 
by Ehrlich granular cells. Acetic acid produces a diffuse 
staining of the nucleus in these aniline stained cells. At the 
same time the conspicuous granules lose their color. The same 
author also states that the granular cells commonly found in 
such great abundance in inflammatory processes are not modi- 
fied leucocytes, but are derived from the fixed connective- 
tissue corpuscles. 
According to Ravogli, the connective-tissue corpuscles of 
the corium and subcutaneous tissue are branching cells, whose 
processes unite to form anastomoses. With advancing age these 
cells undergo structural alterations, and their processes begin 
to form reticula of elastic tissue. Simultaneously with this 
metamorphosis the cell-bodies are said to become flattened, 
elongated, and united in longitudinal rows. At length the cells 
as well as their processes are transformed into ordinary elastic 
tissue. 
BIBLIOGRAPHY. 
Satterth WAITE, T. E. On the Structure and Development of Connective Sub- 
stances (Prize Essay). New York Med. Jour., July, 1876, and Monthly Micro- 
scop. Jour., October and November, 1876. 
Flemming. Arch. f. Anat., etc. 1879. 401—454. 
Stricker. Allg. Wien. med. Ztg. 1879. XXIY., 547. 
Kollmann. Centralbl. f. d. med, Wiss. 1878. XVI., 881. 
Ehrlich. Verhandl. d. Berliner phys Gesell. Jan. 17, 1879; Arch. f. Anat. u 
Phys Phys. Abtheil. pp. 166—169, 1879. 
Ravogli. Wien, med. Jahrb. Heft 1, p. 49. 1879. 
Also the more recent text-books of Klein and Eanvier. 
6 CHAPTER VL 
THE CONNECTIVE SUBSTANCE GROUP— Continued. 
CARTILAGE. 
Cartilage is divided into three prominent varieties: 1, 
hyaline; 2, fibrous; and 8, elastic or yellow. There is, in 
addition, a form called ossifying, which will be described in 
connection with the development of bone. 
Hyaline cartilage is the tissue from which the bones of the 
skeleton are first made; it is also found in the articular and 
costal cartilages, and in the cartilages of the larynx, trachea, 
and bronchi; possibly also in some of the nasal cartilages, and 
in portions of the sternum. All of these tissues consist of a 
solid material or matrix, in which are capsules which contain 
the true cartilage corpuscles. 
The character of the intercellular substance determines the 
particular variety. Thus, hyaline cartilage appears, under the 
microscope, to be structureless and homogeneous. Fibrous 
cartilage, on the other hand, has distinct lines of fibrillation 
extending through it. Elastic cartilage is permeated by net- 
works of elastic fibrils. 
Hyaline cartilage, though so-called because of its apparent 
absence of structure, is now known to be less often structure- 
less than has been supposed, for the researches of Tillmanns 
have revealed distinct marks of fibrillation in some adult artic- 
ular and costal cartilages. Soaking the tissue in alO per 
cent, solution of common salt will dissolve out the cement sub- 
stance and isolate fibrils, though the tissue has previously ap- 
peared homogeneous. Staining with the picro-carminate of 
ammonia (Ranvier’s formula) will also demonstrate the fibrils. 
Each capsule is probably invested by a delicate membrane, 
which is thicker in some instances than in others. Extending THE CONNECTIVE SUBSTANCE GKO UP. 
from this cavity are minute canals, which communicate with 
those of other capsules in many instances, and thus, in all 
probability, establish a system of serous channels which convey 
the plasmatic fluid, i.e.y the lymph. 
Many years ago H. Mueller gave a description of minute passages radiating 
out from the cartilage capsules. Since this time the matter has been studied 
by numbers of observers, but opinions have been divided as to their existence. 
More recently A. Budge has detailed a method by which he claims that a 
complete lymphatic system can be demonstrated in hyaline cartilage. Em- 
ploying a solution of Berlin blue, he injected the cartilage of an epiphysis from 
which the articular lamella had been cut off. Having thus ojmned and exposed 
the substance of the cartilage, he found it permeated with minute blue net- 
works that were in communication with the cartilage capsules. A connection 
with the lymphatics of the bone was also shown. 
Nykamp, who prosecuted his investigations about the same time (1876-77), 
verified the work of Budge, though his methods were different. He experi- 
mented on rabbits, injecting one gramme of indigo carmine (in substance) 
into the abdominal cavity. Blue granules appeared in certain spaces, which 
had shown themselves to be hollow passages by a previous soaking in the neu- 
tral chromate of ammonia. The cartilage commonly known as hyaline was 
also, by this means, shown to be fibrillated. 
Round about every cartilage capsule there is usually an 
area of hyaline material. When very thin sections of cartilage 
are made, these areas sometimes become visible ; soaking in 
acids is said also to bring them into prominence (Klein). 
The amount of intercellular substance in comparison with 
the capsules varies ; as a rule, there is less of this substance 
near the periphery of the cartilage. When the amount is so 
very small that the tissue is almost cellular, it is called par- 
enchymatous cartilage; this condition is observed in all carti- 
lages, at an early stage of development, and in some portions 
of the adult forms. The cartilage corpuscles are rounded 
bodies, sometimes oval and sometimes pyriform. In the nor- 
mal condition they till up the capsule, but after the application 
of reagents that shrivel, such as alcohol, they are withdrawn 
from the walls of the capsules, being only attached at a few 
points (perhaps where their processes extend out through the 
canaliculi). 
The cell-corpuscles and nuclei are said, by some recent ob- 
servers, to exhibit networks in their interior (Schleicher and 
Flemming). They frequently contain, in addition, moving 
bodies, which are often oil-globules of minute size. 84 
MANUAL OF HISTOLOGY. 
The cartilage capsules do not usually appear to have any 
connection with one another when examined in an indifferent 
fluid, though in the episternal cartilage of the frog, immedi- 
ately beneath the perichondrium, a connection may occasion- 
ally be seen. 
Division of the cartilage corpuscle.—One of the prominent 
features seen in cartilage is the division of the cartilage cor- 
puscle. First we notice the splitting of the nucleus ; then of 
the corpuscle itself. When such a division has taken place 
the corpuscles are called daughter-cells (Fig. 33). As a next 
step each daughter-cell may divide and again subdivide, and 
Fig. 33.—Fresh cartilage from the triton. Eollett. 
thus we have developed in one capsule four or eight cor- 
puscles. Sometimes it will be observed in the same specimen 
that with each division of a corpuscle, hyaline matter from 
without the capsule pushes in, and so from the original capsule 
two are now formed. 
Calcification of hyaline cartilage.—Hyaline cartilage in 
old age is infiltrated by a deposit of the salts of lime, which, 
when seen under the microscope, have a granular appearance. 
The deposit occurs first round about the cartilage capsule 
(Ranvier). 
Nerves and blood-vessels are not supplied to hyaline car- 
tilage proper, though blood-vessels which belong to adjacent 
tissues sometimes dip into it or pass through it. 
Methods of studying hyaline cartilage.—An excellent and 
simple plan is to snip off the tip of the episternal cartilage THE CONNECTIVE SUBSTANCE GROUP. 
from the frog ; strip it of perichondrium and mount in serum. 
Tlie shoulder-girdle of the triton (newt) may also be employed. 
It will then be seen that there are numbers of granular cor- 
puscles, with nuclei scattered irregularly throughout an ap- 
parently homogeneous, i.e., structureless matrix. If now a 
little water be added to the preparation, it will be seen that the 
corpuscles are made to shrivel, and in so doing they expose 
the wall of the cavity or capsule in which they lie. The cor- 
puscles do not appear to have any uniform size or shape: some- 
times they are single ; again they are double (daughter-cells); 
occasionally they are united with the corpuscles in adjacent 
capsules. The nucleus is apt to be round and full; the corpus- 
cles are apt to be filled with dark spherical bodies which are 
usually fatty molecules, as may be shown by employing a di- 
lute solution of osmic acid (1 per cent.). 
Using the silver method it will be seen that there exist, in the apparently 
homogeneous matrix, numbers of corpuscles whose nature is not fully under- 
stood. Incidentally it may be mentioned that the silver method often exhibits 
curious markings in all tissues. 
Sometimes these appearances are due to the silver itself, and some caution 
is therefore necessary in deducing conclusions from the method. 
The gold method1 shows that there are concentric rings about the capsules, 
but it is highly probable that this phenomenon is artificial. 
Ranvier recommends, as a staining fluid, purpurine, the 
formula of which is as follows : Take one gramme of powdered 
alum and add to it two hundred grammes of distilled water, 
which boil,in a porcelain dish. To this solution add some pow- 
dered purpurine diluted with water. If the boiling be now con- 
tinued, a portion of the purpurine will dissolve. Filter while 
warm, and receive the colored fluid in a flask which contains 
60 c.c. of alcohol. This liquid has a rose-orange color. The 
nuclei of the corpuscles will be colored red and have a double 
contour ; the cell-body will be bright red. 
Hyaline cartilage may be well exhibited in the respiratory 
tract of young children, as in the cricoid cartilage of an infant 
two or three years old. 
Yellow elastic or reticular cartilage is a very distinctive 
form. It consists of the hyaline variety permeated with elas- 
tic networks. Examples of it may be obtained from the human 
1 See pages 28-29. 86 
MANUAL OF HISTOLOGY. 
epiglottis, laryngeal cartilages, and the pinna of the ear (Fig. 
84). The presence of elastic fibres is proved by their resistance 
to boiling in acids and alkalies, and their failure to color with 
carmine. Sections may be made with the knife and prepared 
in almost any of the ways already mentioned. 
The appearances already described are not seen in the early 
development of elastic tissue, but are easily identified in adult 
Fig. 84.—Section of the boiled and dried auricle of the human ear :a, retiform cartilage; 6, connec- 
tive tissue. Eollett. 
life. Even then the elastic fibrils may only be found in the in- 
terior of the cartilage, while at the periphery the matrix is 
hyaline. Elastic cartilage is coated over with a delicate mem- 
brane—the perichondrium. 
Fibrous cartilage.—This variety is also known as fibril- 
lated or fibro-cartilage. The matrix has probably no elastic 
fibrils, but is interspersed with connective-tissue bundles. It 
is found in the cartilages which make the lips of the joints, the 
inter-articular cartilages, the cartilaginous deposits in tendons, 
the cartilage of the symphysis pubis and of glenoid fossae, and 
possibly in the intervertebral ligaments and sesamoid carti- 
lages. There is often more or less hyaline material about them. 
In many instances the line of distinction between cartilage and 
fibrous tissue is difficult to make out. Where, however, dis- 
tinct corpuscles can be demonstrated, the tissue may properly 
be regarded as cartilage. These bodies are similar to those 
seen in hyaline and reticular cartilage. 
Division of the cartilage-corpuscle.—A problem that has the connective substance geoup. 
attracted tlie study of various histologists for a number of 
years, since Leidy, in 1849, first directed attention to it, is the. 
mode in which cartilage-corpuscles divide. Various theories 
have been afloat, each with its special supporters. 
Dr. W. S. Bigelow, of this country, in 1878 reviewed the 
subject carefully, pursuing his investigations on the hyaline 
cartilage of the triton, tree-toad, frog, various fishes, the guinea- 
pig, foetal pig, and the human embryo in health and disease. 
His inquiries were especially concerned with reference to the 
statement of Buetschli, that in the divisions of the corpuscles, 
the splitting of the nucleus and cell-body are simultaneous. 
As the result of Dr, Bigelow’s work, he concludes that the old 
theory is still tenable, viz., that at first there is a division of 
the nucleus, and that subsequently a septum is found in the 
cell-body. After division takes place the matrix of the carti- 
lage penetrates between the corpuscles, and thus two cavities 
are formed. This view has received confirmation from very 
extended and elaborate researches by Schleicher, to which 
Flemming has also expressed a provisional assent. 
Structure of the cartilage-corpuscle.—According to Schlei- 
cher the nuclei are provided with peculiar filaments and gran- 
ules which undergo amoeboid movements when they are in the 
act of dividing. In the cell-body of young cartilage-corpuscles 
he has seen no network, such as has been described by some 
later writers (Heitzmann, Klein, etc.), though in the adult tissue 
peculiar linear markings are evident. He thinks that the nu- 
cleus is not permeated by a network, but is homogeneous. 
Reticulated appearances are apt, he thinks, to be the result of 
using reagents that alter the natural quality of the tissues. 
According to Flemming, the nucleus of the cartilage-corpus- 
cles contains a network which gives the appearances described 
as “ coarsely granular.” 
In the drawings of this author the cell-bodies nowhere exhibit a network, 
but, on the contrary, linear markings, which have often a concentric direction. 
In many, the internal structure is represented as homogeneous. The conflict of 
opinion now apparent in this matter, and the marked differences in the micro- 
scopic drawings of the same object, make it apparent that these topics are still 
to be regarded as sub judice. 
Structure of the intercellular substajice.—According to Spina there is an intra- 
cellular substance in cartilage which is directly continuous with the intercel- 
lular substance, which itself exhibits an extremely delicate network. This 88 
MANUAL OF HISTOLOGY. 
condition, which he regards as an early form of cartilage, undergoes changes, 
in so far that the intercellular network is enlarged and narrowed so as to give 
the appearance of fascicles or bundles of parallel fibres. The meshes are filled 
with a finely granular substance which is thought to be partly formed at the 
expense of the network. The method employed in demonstrating these ap- 
pearances consisted in taking the articular extremities of frog’s bones, im- 
mersing them three to four days in alcohol, then cutting thin sections, and 
finally, examining them in alcohol. 
BIBLIOGRAPHY. 
Tillmanns. Archiv f. mikrosk. Anat. X. Bd. X. p. 401. 1874. 
Budge, A. Archiv 1 mikrosk. Anat. Bd. XIY., S. 65. 1877. 
Nykamp. Archiv f. mikrosk. Anat. Bd. XIY., S. 492. 1877. 
Heitzmann. Studien am Knochen u. Knorpel. Wien. med. Jahrb. 1872. V. and 
H.’s Bericht. 
Bigelow, W. S. Arch. f. mikrosk. Anat. XVI., 2. 1878. 
Schleicher. Ibid. 
Flemming. Ibid. 
Klein and E. Noble Smith’s Atlas of Histology. 1879—1880. 
Ranyier. Traite technique d’histologie. 1877. 
Buetschli. Zeitschr. f. wiss. Zool. 29, p. 206. 
Spina, A. Sitzb. de k. Akad. der Wiss. Bd. LXXX., LXXXI. 1879, 1880. CHAPTEE VII 
THE CONNECTIVE SUBSTANCE GROUP.—Continued. 
BONE. 
There are two principal varieties of bone known to anato- 
mists, the compact and the cancellous or spongy. The former 
is found in the shafts of all the long bones of the body and 
along the outer surface of all the short and flat bones. The 
latter occurs in the articular extremities of all long bones and 
in the interior of all short and flat bones. 
Compact tissue consists of an unyielding, almost inelastic, 
massive framework, which is traversed by networks of blood- 
vessels and lymphatics, and perhaps by nerves. The dense 
organic substance forming the groundwork of all bone—ossein 
—is in reality nothing but a form of connective substance 
almost precisely resembling ordinary fibrous tissue, but which 
is evenly infiltrated with minute molecules of the carbonates 
and phosphates of lime and some other inorganic salts. These 
insoluble matters are so thoroughly intermixed with the fibrous 
tissue that they give it great solidity, though at the same time 
they restrict its flexibility, and therefore increase its suscepti- 
bility to fracture. 
Like other forms of the connective-tissue series, it contains 
corpuscles that are disposed in a regular way between lamel- 
lae, which here correspond to the fascicles of fibrous tissue. The 
province of these corpuscles is doubtless the same as that of 
other connective-tissue corpuscles, viz., to preside over the nu- 
trition of the tissue in which they are found. 
After decalcification by strong acids, such as the nitric or 
muriatic, if the residue be boiled it will yield gelatin or chon- 
drin. 
These corpuscles that have just been described are not al- 90 
MANUAL OF HISTOLOGY. 
ways easily recognized, and, in fact, have often been ignored 
by writers of anatomical text-books. They were not detected 
for a long time, because the capsules in which they are em- 
bedded received all the attention, and were even called hone- 
corpuscles. But when it was discovered by Virchow that 
these bodies had nuclei, and that they could be separated, to- 
gether with their processes, from the bone, it was supposed 
that the nutrition of the tissue was maintained through them, 
acting in the capacity of hollow tubes. This view Virchow at 
one time supported. Subsequently it was discovered that in- 
jection fluids could be forced into the canaliculi and round 
about the corpuscles, so that three facts became assured : (1) 
the existence of capsules in the bony substance with radiating 
and anastomosing passages, the lacunse and canaliculi ; (2) the 
presence of nucleated and branched corpuscles in the lacunse; 
and of spaces (8) about the nucleated corpuscles and their 
processes, suitable for the movement of fluids designed for the 
nutrition of the part. 
The structure of bone then became clear, and its similarity 
with other connective substances well established. These bony 
canaliculi extend to the wall of the Haversian canal, the great 
channel conveying the blood-vessels and larger lymphatics. 
Thus a lymph-canalicular system permeates the bone in close 
connection with the blood-vessels, bathing every bone-cor- 
puscle. 
When a cross-section is made of any long bone, it will be 
observed that most of the lamellae have a concentric arrange- 
ment about each Haversian canal (Fig. 85, 5). But it will also 
be seen that there are other groups of lamellae whose arrange- 
ment is slightly different. For example, at the periphery of 
the bone their direction is parallel with the surface. 
Such lamellae may be represented at a. They are known as 
the intermediate or circumferential (Tomes and Be Morgan). 
Another group, only partly encircling each canal, is known as 
the peripheric or interstitial, c. The first mentioned, imme- 
diately about the canal, are the concentric, h. 
Schaefer believes with Sharpey that each lamella consists of fibres crossing 
each other diagonally, and separated on either side by a homogeneous layer. 
According to Yon Ebner, the peculiar cross striations belong only to Canada 
balsam preparations that are old. These markings are due to the peculiar 
refractive power of the balsam which fills the canaliculi. THE CONNECTIVE SUBSTANCE GKOUP. 
91 
The arrangement just described is found in all compact 
bone where there is any considerable thickness, but when, as 
in Hat bones, the cortex is very thin, the lamellae often pursue 
a straight and parallel course. Some of these lamellae or plates 
exhibit transverse striations ; others are homogeneous. 
In Fig. 85 may be seen the lacunae lying between the 
lamellae. They appear 
as dark spaces disposed 
at quite regular intervals 
and, having their long 
axes parallel with the 
course of the lamellae. 
Laterally each corpuscle 
gives off numbers of pro- 
cesses, many of which 
branch, while all, or near- 
ly all, anastomose with 
corresponding branch- 
lets of other corpuscles- 
A branchlet is also given 
off from the end of each 
corpuscle, and forms a 
connection with the adjacent bodies lying in the same inter- 
lamellar space and in the same plane. 
Pig. 85.—Transverse section of human femur, deprived of 
inorganic material by hydrochloric acid. Bollett. 
The Haversian canals form a broad-meshed network through- 
out the bone, establishing a communication between the central 
marrow cavity and the external surface of the bone (Fig. 36). 
The arrangement of parts comprised by each Haversian 
canal, with its investing lamellm, and interposed lacunee and 
their anastomosing canaliculi constitutes an Haversian system. 
Though found mainly in the they may also be 
seen in the large trabeculae of the spongy substance. As seen 
in Fig. 36, the Haversian canals form a network of which the 
longitudinal tubes are the larger and longer. Besides convey- 
ing blood-vessels and lymphatics they have a certain amount 
of connective tissue which varies according to the locality, and 
establishes a more or less complete connection between the con- 
nective tissue of the marrow cavity and of the periosteum. 
In young bone this is well seen; in adult bone the direct 
continuity can with difficulty be traced, as the vessels are apt 
to fill the tubes pretty completely. 92 
MANUAL OF HISTOLOGY. 
Preparation of dry hone.—In order to study the char- 
acteristics which have Just been described, any human long 
bone may be taken. It should be stripped of its soft' parts, 
bleached, and well dried. Thin sections are then to be made 
both in a longitudinal and transverse direction, with a watch- 
spring saw. 
Next, cleanse them well in water to which a little bicar- 
bonate of soda has been added; then place on a whetstone 
and grind down by rubbing backward and forward with the 
finger until they are suffi- 
ciently thin ; or the sections 
may be placed between two 
plates of ground glass and 
rubbed down. 
Finally, when so thin that 
type may be read through 
them, mount either dry or 
in Canada balsam or dam- 
mar varnish. All the char- 
acteristics already described 
may then be seen. 
Preparation of decalci- 
fied hone.—Another method 
consists in first removing the 
earthy salts. If it is desira- 
ble to accomplish the work 
rapidly, cut the bone to be 
prepared into the smallest 
available pieces and immerse 
from four to five days in a 10 
per cent, watery solution of 
hydrochloric acid. 
Fig. 86. —Longitudinal section of human ulna, show- 
ing the Haversian canals forming meshes. Rollett, 
The completion of this 
process may be determined by testing the bone with a fine cam- 
bric needle. So long as it meets with resistance, the presence 
of the bone-earths is certain; on the other hand, if it enter 
easily, the process of decalcification is over, and the piece ready 
for cutting. 
Now wash thoroughly in water, so as to remove the acid, 
place in 80 per cent, alcohol, gradually increasing the strength 
to 95 per cent. The specimen is then ready for use and may THE CONNECTIVE SUBSTANCE GROUP. 
be treated precisely as any other tissue of the body. If more 
time is at the disposal of the student, chromic acid may be 
used in a i per cent, solution. This process is rather slow, re- 
quiring several months. It may be materially hastened by the 
use of nitric acid (2 per cent.). It has been found that after 
immersion in chromic acid for a few days, the soft parts are 
rendered insensible to the action of other strong acids, such as 
nitric and hydrochloric, when used in the dilute form. These 
chromic acid preparations are exceedingly beautiful objects 
Fig. 37.—80ne lacunas with their processes. Kollett. 
when seen with low powers. The matrix is of a deep grass 
green. If a thin section is stained with borax-carmine (Arnold s 
formula) the bone-corpuscles and connective tissue are stained 
red, and the contrast of color brings out the finer elements 
very distinctly. 
Picro-carmine may also be used, and then the muscular tis- 
sue, if any chance to adhere to the bone, is stained yellow ; oi 
eosine and hsematoxylon may be used instead of borax car- 
mine, and thus very excellent examples of triple staining pro- 
cured. Sometimes a saturated solution of picric acid is em- 
ployed to decalcify, but the excess of acid, after taking out 
the bone-earths should be thoroughly removed by soaking in 94 
MANUAL OF HISTOLOGY. 
water before immersion in any staining fluid. In preparing a 
specimen for cutting with the knife it may conveniently be 
held in the hand, or, if the microtome is used, the bone may 
be embedded in the ordinary mixture of wax and oil, pith, or 
liver, according to methods already described. Rutherford re- 
commends glycerine Jelly for this purpose. 
Any of these plans of preparing decalcified bone will reveal 
the presence of the bone-corpuscles within the lacume. These 
will be found to correspond quite closely in size and shape 
with the cavities. They may also be shown to have a direct 
continuity with the connective-tissue corpuscles of the perios- 
teum. In growing bone this is more evident. A nucleus can 
also sometimes be seen in the bone-corpuscle. In Fig. 36 
the lacunae, with their canaliculi, are well shown. 
Sharpey's perforating fibres.—Attached to the outer sur- 
face of compact tissue, and penetrating the bone at right an- 
gles, are certain fibres which have been named after Sharpey, 
their discoverer. 
Take a flat bone of the skull that has been decalcified, seize 
pieces with the forceps, tear them out from the surface, and 
examine in water. In some of the fragments the bundles of 
fibres will be seen ; in others the lamellae, perforated for the 
fibres. If a portion of tendon adhere to the bone, and a sec- 
tion be made through the two at their line of apparent Junc- 
tion, it will be seen that the tendon-fibres are continuous in 
the bone with Sharpey’s fibres. 
A very prevalent view is that they constitute the remains of 
the periosteal processes, which we shall see are largely con- 
cerned with the ultimate development of bone. 
Cancellous tissue.—All of the elements of bone, that go to 
make up a Haversian system, are found in the cancellous 
tissue, so that, in this respect, it does not differ from the com- 
pact. The chief peculiarity lies in the marrow cavities, or 
channels, as they might appropriately be called, and they indi- 
cate either, on the one hand, that the bone is passing through 
a developmental stage ; or that it is being rarefied by a process 
of retrograde metamorphosis ; or, finally, that it has reached a 
stadium of repose in either of the first-named changes. These 
points will be further particularized when the growth and de- 
velopment of bone is explained, but the reader is now prepared THE CONNECTIVE SUBSTANCE GEOUP. 
for the rather remarkable proposition that compact bone is 
formed out of spongy, and spongy out of compact. 
These marrow channels are a series of branching and anasto- 
mosing tubes, rich in corpuscular elements and vessels. In 
young bone the latter are known as red marrow. When a 
longitudinal section has been made through a tubular bone, it 
will be seen that the channels are enclosed in an osseous net- 
work, whose meshes differ much in shape. In the articular 
extremities they are long and narrow; at other points, more 
nearly quadrilateral. 
There is a second variety of marrow, known as yellow, which 
is found in the central cavity of the long bones. The yellow 
color is due to the presence of fat, though it also contains 
peculiar, small, colorless corpuscles, not unlike the leucocytes 
of the blood, and known as marrow-cells, together with the 
ordinary branched and nucleated connective-tissue corpuscles, 
also large multi-nucleated bodies that are usually granular and 
sometimes striated, and blood-vessels. The large corpuscles 
are the myeloplaxes of Robin (giant-cells). 
The red marrow also contains marrow-cells, though but few 
fat-cells. It is remarkable for being the seat of the peculiar 
nucleated blood-corpuscles that have been described by Neu- 
mann and Bizzozero. They are transitional between the white 
and the red in size, and have a uniform yellowish green color 
(Klein). 
The anthers above referred to found the nucleated corpuscles in the red 
marrow of the ribs and bodies of the vertebrae; they resembled blood-corpus- 
cles that are found in the human embryo, and were regarded as evidence that 
the bones have bloodmaking properties. Later researches (Orth and Litten) 
have seemed to corroborate these views, and to ha've shown that in certain 
morbid states of the blood, as in carcinoma, phthisis, and syphilis, an effort of 
this kind is made for the relief of the constitutional infection. Experiments 
upon dogs have also added further testimony and have shown that after extreme 
artificial ansemia there is a new formation of blood-globules, in which the 
nucleated bodies play an active part, together with other elements, such as the 
giant-corpuscles of Hayem, etc. These views, however, have met with opposi- 
tion, and Eutherford (“ Pract. Histology,” p. 88) maintains that the nucleated 
corpuscle is an indication of corpuscular disintegration rather than of new- 
formation. 
The periosteum is a layer of dense fibrous tissue closely 
covering the bone, and connected with it by a thinner layer of 96 
MANUAL OF HISTOLOGY. 
looser texture. The external portion may be composed of sin- 
gle, double, or treble laminae of varying thickness. The inner 
or osteogenetic portion is of great interest and importance, 
as it contains the osteoblasts, which are active agents in the 
formation of a great part of all bones, as we shall presently 
see. 
Development of bone.—Views as to the method by which bone 
is formed have undergone great changes within the past few 
years, and it may be stated that most modern observers have 
given in their adhesion to the theory that bone is not developed 
by a calcification of cartilage, but by a long and complicated 
series of changes inaugurated by the corpuscles of the marrow 
cavities, on the one hand, and those of the periosteum, on the 
other. These conclusions have been the result of very extended 
researches conducted by a variety of methods and upon many 
kinds of animals. 
As the mode of growth in man and horned cattle is identical, 
a good method of procedure is as follows. Take the hoof of a 
yearling bullock, and, removing the bones, macerate them a 
few days in a 10 per cent, watery solution of hydrochloric acid 
and then in chromic acid (gr. ij.— f j.). In a few days they 
will be decalcified sufficiently to allow of a thin section being 
shaved off from the surface so as to include parts where ossifi- 
cation has already commenced. The sections may then be 
stained in a neutral solution of carmine and mounted. The 
gradual stages between the advancing bone and the liquefying 
cartilage can now be studied. Following the changes from the 
surface of the articulation toward the centre of the bone, there 
is seen at first, beneath the fibrous layer, a stratum of hyaline 
cartilage. The corpuscles are long, flattened, and lie parallel 
with the surface. Passing to a greater depth they become 
larger, and increase in number by gradual progression. As 
these capsules enlarge and their contents multiply, they 
begin to be arranged about the wall of the cavity, while 
the matrix gradually wastes away. A little farther and 
there is a deposit of calcific material in the intercapsular sub- 
stance. Another step internally and the cartilage capsules 
have in part coalesced, and now they are beginning to be filled 
by the marrow tissue pushing up from the central parts of the 
bone. When the connective tissues and vessels that constitute 
this arborescent growth have entered the capsules, the corpus- THE CONNECTIVE SUBSTANCE GROUP. 
cles that line them are called osteoblasts. Whether or not they 
are identical with the cartilage-corpuscles, or belong to the 
budding marrow-processes, seems to be a matter of doubt. 
Klein intimates that the cartilage-corpuscles disintegrate. Ran- 
vier has seen no proof of it. It is probable that some of the 
cartilage-corpuscles persist, certainly to a limited extent, 
and preside over the remains of the calcified cartilage. The 
bulk of the new bone is made up, however, of new material 
which is deposited under the form of concentric lamellae about 
the marrow cavities, most likely by a proliferation of the 
osteoblasts. 
These changes may all be observed to advantage in the 
specimen just mentioned, and the successive gradations of the 
process can be conveniently magnified, so as to be easily seen, 
by making sections obliquely to the surface of the bone. With 
a low power the specimens will have uncommon beauty, as the 
corpuscles take the carmine well, while the interstitial tissue is 
of a bright, transparent grass-green. 
In a vertical section of a long bone, while the process is 
essentially the same, there are some modifications in the suc- 
cessive steps. Thus the spongy bone of the epiphysis en- 
croaches on the cartilage, causing it to be absorbed in the man- 
ner already described, but the intermediary cartilage, lying 
between the epiphysis and diaphysis, is seen to have its cor- 
puscles arranged in long lines parallel with the axis of the 
bone {“step-ladders”). The bone meshes of the encroaching 
bone are also shaped in correspondence with the cartilage cap- 
sules, that is, they are long and narrow. 
Formation of hone through the medium of cartilage.—The 
successive changes in this species of bone development have 
been best described by Klein. According to him the hyaline 
cartilage that is destined to prepare the way for bone is covered 
with perichondrium, consisting like the periosteum of two 
layers. This membrane does not at first contain mature fibrous 
tissue, but merely the rudiments of it, under the form of spin- 
dle-shaped corpuscles ; its internal layer, however, is early pro- 
vided with spherical corpuscles, the future osteoblasts, and is 
rich in vessels. 
Subsequently this osteogenetic envelope puts out processes 
{periosteal processes, Virchow) that penetrate into the carti- 
lage-capsules, which, melting as the external growth makes its 98 
MANUAL OF HISTOLOGY. 
way inward, develop communications between the capsules, so 
that in this way a cartilaginous network is formed that is tilled 
with the arborescent tissue. This change in the cartilage, 
which is characterized by absorption and rarefaction, is called 
chondro-porosis. 
At a more advanced stage the cartilage around the oldest 
channels has become transparent in places, while the walls are 
irregular, because portions of calcified trabeculae project into 
them. These irregular spaces are called primary marrow 
cavities. Now upon the walls may be seen, not the cartilage- 
corpuscles, but the osteoblasts, which are proceeding to develop 
concentric layers of osseous tissue. 
When this process has been completed, the osseous tissue 
will be found to have replaced the calcified cartilage, and true 
bone has been formed. But this action may be no sooner 
completed than absorption will again commence, and at first in 
the last or most internal layer of the Haversian system. This 
process is essential for the development of the central marrow 
cavity. After an Haversian system has been removed, the 
matrix will also disappear. 
Now, while this cavity is filling up with marrow a gradual 
development of bone is taking place from the periosteum, 
which slowly encroaches upon the bone whose formation we 
have just described. 
This last stage results in the formation of adult bone. 
When it has been completed all the first formed bone has 
been absorbed before it. This periosteal or metaplastic bone 
is at first spongy, as is all new bone; in the fulfilment of its 
task it next appears to form compact bone, and then part of 
this latter is rarefied, as, for example, along the wall of the 
central cavity. Thus, as we have already seen, compact bone 
is formed from spongy, and spongy from compact. The peri- 
pheric or interstitial lamellae are either the remains of calcified 
and unabsorbed trabeculae, or perhaps the walls of other Haver- 
sian systems forming sides of the bony network. 
Formation of bone from membrane.—This second method 
of bone-formation is seen in the bones of the skull and face. 
The steps are precisely similar to those already described. The 
inner layer of the periosteum, which is lined witli osteoblasts, 
produces both matrix and bone corpuscles by a process of bud- 
ding. The change first begins at the points of ossification. THE CONNECTIVE SUBSTANCE GEOUP. 
At first the bone is spongy, but later absorption takes place— 
osteoporosis. Around some of the marrow-tubes concentric 
lamellae are formed, and in this way a Haversian system de- 
velops. The unabsorbed portions of the trabeculae are thought 
to constitute the lamellae known as the intermediary. Com- 
pact tissue is thus formed from spongy. This theory, which 
has been placed in its present acceptable light by Klein, is very 
simple and appears to accord with observation, and explains 
all the phenomena. Yet those who have believed in the direct 
transmutation of cartilage into bone are still in the field. 
Kolliker maintains that both views are correct. 
According to this last named author the differences between primary or 
primordial and the tegumentary or secondary bones are, from a morphological 
point of view, sharp and complete. The former are ossifications of the carti- 
laginous skeleton. 
The tegumentary are never cartilaginous at first; the primordial bones, on 
the other hand are, without exception, formed from cartilage. The method and 
manner in which bony tissue is formed is the same in both bones. The pri- 
mordial skeleton in the lower vertebrates ossifies only in part from the peri- 
chondrium, in part perichondrally, and, in part, endochondrally. 
According to Kassowitz, in the tuberosities and spines of the bones the 
periosteal processes of the periosteum, which develop the bone, are primarily 
cartilaginous, the fibrillated tissue being converted into hyaline cartilage, 
which is at first calcified and then undergoes direct conversion into bone. 
According to the experiments of Strawinsky a transplanted periosteum will 
develop either bone or cartilage, when the conditions are favorable. The con- 
ditions of nutrition determine which it shall be. When the supply is best, 
cartilage is formed ; when poorest, bone. 
The earliest evidences of ossification were seen by this observer between 
the fourth and fifth days. The formation of vessels preceded that of bone. 
Absorption commenced between the second week and the second month. The 
new formation of periosteum is partly derived from the border of the wound 
and partly from the Haversian canals, which contain a small amount of connec- 
tive tissue. 
Development of hone and absorption.—lt lias been seen 
that these two processes go on hand in hand. As soon as the 
periosteum has commenced to deposit new layers of bone on 
the surface of the primary spongy bone, absorption takes place 
along the marrow canal. First of all, as we have already said, 
the innermost of the concentric lamellae yield. In this way 
the Haversian canals are widened and become Haversian spaces, 
as they were at first; then the interstitial lamellae, and finally 100 
MANUAL OF HISTOLOGY. 
the spaces disappear, and in place of them there is a single 
dilated central cavity. 
How ship's lacunce are the pits or lacunae seen in bone 
beneath the periosteum. They usually contain a multinuclear 
corpuscle (giant-cell), which is in some way related to absorp- 
tion, and, therefore, has received the name osteoclast (Kolli- 
ker). It has been surmised (Klein) that they are the agents by 
which an acid is formed that dissolves the lime-salts. Whether 
they are developed out of the osteoblasts or not is a matter of 
uncertainty. 
All the steps, both in development and absorption of bone, 
have been carefully studied and placed upon a most satisfac- 
tory foundation (Lieberkuhn and Bermann). The absorption 
of bone has also been actually proved by measurements of the 
bones in children (Schwalbe). By comparing the bones of the 
third and fourth years of life, it wTas found that the marrow 
cavity had enlarged in the latter, while the compact bone had 
diminished in thickness. The change commenced at the sixth 
month. This physiological process is closely allied to the 
pathological one exhibited in rachitis; in the latter the de- 
velopment of bone from the periosteum has the character of 
foetal bone, but the formation of the lamellae is slow and 
incomplete. 
It has been claimed that the growth of bone takes place 
by an expansion of the intercellular substance (Strelzoff), but 
this is denied (Kolliker, Wegener, Schwalbe, and tfihers). 
The ossein appears to increase somewhat, but it is at the ex- 
pense of the bone-corpuscles, which are thereby diminished in 
size. 
Formation of callus.—The method is the same as in the de- 
velopment from periosteum. A corpuscular blastema is devel- 
oped from the periosteum and intermuscular tissue. This 
presses in between the fibres and bundles of the loose con- 
nective tissue, pressing them asunder, assuming considerable 
volume. This new tissue is hyaline cartilage. In from three 
to six weeks it ossifies, being in part directly transformed into 
bone, in part mediately, i.e., through the agency of medullary 
spaces and osteoblasts. Where the extremities of the bone are 
widely separated there is a formation of bone in the medullary 
spaces of the broken ends of the bones. The pre-existing bone- 
corpuscles have no part in the new-formation. This compact 101 
THE CONNECTIVE SUBSTANCE GROUP. 
bone thus formed will be absorbed in a few months, in its 
internal portions, by rarefying ostitis, so that the marrow cavi- 
ties of the broken diaphysis will be in communication. 
BIBLIOGRAPHY. 
The student is referred, for further particulars, to Klein’s Atlas of Histology, Ran- 
vier’s Traite technique d’histologie, Strieker’s Manual of Histology, and also to the 
following recent writers: 
Schaefer. Pract. Histology. 1872. 
Lieberkuhn and Hermann. Ueber Resorption der Enochensubstanz. 1877. 
Atjprecht. Ueber Eiesenzellen in Elfenbeinatiften. Med. Centralblatt, Ho. 20. 
Jahresb. d. Fortschritte der Anat. und Phys. 1878. 
Arnold, J. Virchow’s Archiv. Bd. 71, p. 17. 1877. 
Von Ebner. Sitzungsbericht der Wiener Akad. 111. Abtheil. Bd. 75. Hofmann 
und Schwalbe’s Jahresb. 1878, 
Kassowitz. Med. Centralblatt, Ho. 5. Hofmann und Schwalbe’s Jahresb. 1878. 
Schwalbe. Sitzungsb. dermed. naturwiss. Gesellschaftzu Jena. 1877. H. und S.’s 
Jahresb. 1878. 
Strawinsky. Ueber Knochenresorption. H. und S.’s Jahresbericht, p, 109, 1878. 
Litten, M., and Orth, J. Berliner klin. Woch. Ho. 51, p. 743. 1817. 
Kolliker. Entwickelungsgeschichte. V. und S.’s Jahresb. 1878. 
Totjrneux, F. Application de I’acide osmique a I’etude du tissu osseux. Oaz. 
med. de Paris. 6. S. 111. 318. 1881. CHAPTER YIII. 
THE TEETH. 
From the standpoint of descriptive anatomy, every tooth is 
composed of three parts: (1) the crown, that portion which 
stands above the level of the mucous membrane of the gum ; 
(2) the neck, a constricted part at the level of the gum ; and (3) 
the root, which terminates in one or more fangs, and is firmly 
embedded in the alveolar process of the jaw. Each fang also 
is pierced from below by a canal, which extends up into the 
crown, and is filled by a soft material rich in nerves and ves- 
sels, called the pulp, which has the special province of sup- 
plying nutriment to the dense tissue about it. 
From a histological point of view, every tooth may be di- 
vided into : 1, enamel; 2, dentine, or ivory ; 8, cement, or true 
bone. The enamel forms the covering for the crown, the cement 
for the root; but they meet at the neck, and there the cement 
slightly overlaps. The ivory or dentine lies intermediate be- 
tween the outer coatings and the pulp. 
The enamel.—This substance, which is the hardest met with 
in the body, consists of a series of long polyhedral columns 
grouped in bundles and disposed mostly at right angles to the 
surface of the dentine which lies beneath it. Each column or 
pillar is a hexagonal prism, having a diameter varying between 
■johro and inch. When viewed in cross-section these col- 
umns look like a tesselated pavement. They are not, however, 
closely applied to one another, but have interspaces which are 
said to be filled with a homogeneous substance or fluid. 
All of the groups of columns do not stand vertical to the 
dentine ; some are parallel to it, and thus are interwoven with 
the vertical ones. This crossing of the fibres produces an 
alternation of light and dark bands (Fig. 38, 1). But there are 
other systems of markings. In the same figure are wavy THE TEETH. 
lines running parallel to tlie surface. These are the “ brown, 
parallel stripes of lletzius.’’ They pursue a somewhat curved 
course. No unity of opinion exists about their significance, 
one (Hertz) attributing them to deposits of pigment, another 
(Von Bibra) to the pres- 
ence of the oxide of iron. 
Still other striae are ob- 
served, and are thought 
to represent the zigzag 
or spiral course of the 
enamel prisms. It is 
observed that when the 
prisms are isolated, which 
can be accomplished by 
immersion in a dilute hy- 
drochloric acid solution, 
they have a somewhat 
spiral form, and have 
bulging sides and cross 
markings, the signifi- 
cance of which will be 
alluded to at another 
place. 
Near the line of the 
dentine there are spaces 
between the prisms which 
are continuous with the 
cavities in the dentine. 
These are called the in- 
terglobular spaces of 
Czermak. They also oc- 
cur at irregular intervals 
in the dentine. 
Fxa. 38.—Premolar tooth of the cat, in situ. Vertical 
section, magnified 15 diameters. 1, enamel with decussating 
and parallel striae ; 2, dentine with Schreger’s lines ; 8, ce- 
ment ; 4, periosteum of the alveolus; 5, inferior maxillary 
bone. Waldeyer. 
In young subjects 
there is a delicate mem- 
brane covering the sur- 
face of the enamel. It is composed of laminated epithelial 
scales, and corresponds to the corneous layer of the skin, of 
which, indeed, it represents the vestiges. 
The dentine or ivory (Fig. 88, 2) consists of a dense and 
hard matrix impregnated with the salts of lime. It contains 104 
MANUAL OF HISTOLOGY. 
numerous passages having, like the enamel prisms, a direction 
at right angles to the surface of the bone. These passages, the 
dentinal canals, are united with one another laterally by 
minute oblique branches, and form undoubtedly open channels 
of communication between the pulp cavity and the spaces be- 
tween the enamel prisms in the crown and the bone lacunae of 
the cement in the fang. Each canal 
is lined with a particularly delicate 
and resistant membrane, the den- 
tinal sheath of Neumann. 
Upon the internal surface of the 
dentine, or the external surface of 
the pulp-tissue, is the layer of 
odontoblasts (Schwann). These cor- 
puscles, according to Waldeyer, 
have long branching processes ex- 
tending in three directions, inward 
into the pulp-cavity, outward 
through the dentinal channels, 
forming the dentinal fibres of 
Tomes, and laterally so as to form 
connections with adjacent corpus- 
cles, On the outer surface of the 
dentine the canals connect with 
the interglobular spaces of Czer- 
mak, and they in turn are con- 
tinuous with interstices between 
the enamel prisms. The dentinal 
tubules never appear to be in di- 
rect communication with the enam- 
el spaces, but only mediately, as 
has been described. These cavi- 
ties are filled with protoplasmic 
material. Those immediately adjoining the cement are small 
in size, and form what is known as the granular layer of 
Tomes or PurMnje. 
Fig. 39.—Canine tooth of man, present- 
ing a portion of the transverse section of 
the root: 1. cement with large lacunae and 
parallel striae; 2, interglobular substance; 
3, dentinal tubules. Magnified 300 diame- 
ters. Waldeyer. 
Dentinal globules (Fig. 39, 2) is the name given to certain 
spheroidal masses that are regarded (Waldeyer) as calcified 
remains of the corpuscles in the spaces. The contours of these 
masses correspond in outline with those of the interglobular 
spaces. THE TEETH. 
Beneath the cement the intercommunication of interglobu- 
lar spaces and bone-lacunse is well shown. The interglobular 
substance is apt to be present in layers; the lines which are 
then called the incremental lines of Salter, are supposed to 
show that there has been growth by successive stages. The 
lines of Schreger (Fig. 38,2) are also waving parallel lines ; they 
are thought to be due to the curvature of a series of adjacent 
fibres. In some instances vascular channels have been found 
in the dentine, which has acquired the name osteo or vaso- 
dentine. In pathological conditions masses have also been 
found containing bone-lacunse. They have been called odonto- 
mata by Virchow. 
The cement is true bone-tissue, containing lacunae and 
canaliculi, and in them the bone-corpuscles with their pro- 
cesses. The matrix is also subdivided into lamellae. The peri- 
osteum of the gum dipping down into the bony socket from 
the surface of the gum forms a coating over the cement. Oc- 
casionally Haversian canals and blood-vessels are seen where 
the cement is thick (Salter). Sharpey’s fibres may also be seen, 
according to Waldeyer. 
The pulp is a substance that belongs to the connective- 
tissue series. Adjoining the dentine are two layers of corpus- 
cles. The nearest are long cylindrical bodies whose oval nuclei 
are distant from the dentine. Wedged in between them, and 
forming a layer intermediate between them and the pulp, are 
peculiar branched corpuscles of a spindle or pyramidal shape. 
According to Klein, these latter send processes into the den- 
tinal tubules, while, according to Waldeyer and 801 l the odon- 
toblasts send the fibres, and are also connected to one another 
by lateral processes. The pulp tissue is very rich in non- 
medullated nerves; their prolongations penetrate between the 
odontoblasts, but it is a matter of question whether they enter 
the dentinal canals. 
Capillaries are abundant and form close networks in the 
pulp. The lymphatics are said to accompany the blood-vessels 
and to be surrounded by endothelial sheaths. 
Development of the teeth— Waldeyer, whose views on the 
teeth are the most complete and satisfactory extant, makes the 
following succinct statement: 
“The anatomical model of a tooth of a vertebrate animal 
is a large papilla of the mouth or of the pharyngeal mucous 106 
MANUAL OF HISTOLOGY. 
membrane, which in consequence of chemical and histological 
conversion of its constituents has acquired a remarkable degree 
of hardness, and according to whether the connective-tissue 
substance of the papilla participates in the hardening or not, 
two large groups of teeth are distinguished—dentinal teeth and 
horny teeth. The horny teeth are by far the most simple in 
Fig. 40.—Vertical section of the inferior maxilla of a hu- 
man foetus,measuring 11 ctms. from the vertex to the coccyx. 
Magnified 25 diameters. 1, dental groove; 2, remains of the 
enamel germ; 3, enamel organ presenting externally epitheli- 
um, as also where it forms the enamel germ of the papillae of 
the dental sacculus ; 4, secondary enamel germ: rudiment of 
the permanent tooth; 5, dental germ; 6, lower jaw; 7, 
Meckel’s cartilage. Waldeyer. 
Fig. 41.—1, various forma of 
odontoblasts, with the three kinds 
of processes; 2, three enamel 
cells, with a few cells of the stra- 
tum intermedium attached; 3, an 
enamel cell, with a small portion 
of enamel; 4, fragments of ena- 
mel fibres from young and soft 
enamel; 5, old enamel fibres with 
transverse striae and rounded ex- 
tremities. Waldeyer. 
their structure. They appear as more or less developed papil- 
lae covered with a thick horny investment. They are never 
continuous with portions of the skeleton, but constitute the 
transition to other horny formations, as hairs, stings, etc.” 
“In the dentinal teeth the connective-tissue matrix of the 
papillae plays a most important part in the hardening process, 
which here proceeds in a manner precisely similar to the ossi- 
fying process, except that no true bone is formed, but only an 
allied substance, of much harder consistence, and differing 
more or less in histological structure, termed dentine. The epi- 
thelium of the tooth papillae either atrophies to a rudimentary THE TEETH. 
horny investment—the cuticula (membrane of the enamel)—or 
it becomes elongated in a remarkable manner into long, petri- 
fied prisms, which collectively invest the dentine and are 
known as the enamel.” 
Preparations for the development of the teeth take place at 
a time when the epithelium of the mucous membrane of the 
mouth is found growing downward, like a solid peg, with a 
rounded extremity. 
This has been called the primary enamel organ. As a next 
step, the material which is to give form to the tooth pushes 
upward as a papillary growth, and meeting 
the epithelial peg, pushes in or invaginates 
its rounded extremity. This is the tooth 
papilla, and as it pushes upward the pri- 
mary enamel organ becomes the secondary 
enamel organ, or the enamel cap. We have 
now two tissues which are embedded in the 
soft embryonic substance, that happens at 
this early period to be gelatinous. That 
portion of it immediately surrounding the 
papilla and cap is called the tooth-sac. 
The papilla, which becomes highly vas- 
cular, is covered, on its outer surface, by 
the odontoblasts, a layer of columnar epi- 
thelial corpuscles, which elongating, are 
transformed directly into the dentinal sub- 
stance at their outer extremity. 
Fig. 42.—Longitudinal sec- 
tion of a milk tooth from the 
foetal sheep, carried through 
the margin of the dentine 
pulp and adjoining portion of 
the enamel organ. Magni- 
fied 200 diameters. 1, dental 
sacculus; 2, external epithe- 
lium and stratum interme- 
dium here united to the in- 
ternal epithelium or enamel 
cells; 3, after the disappear- 
ance of the enamel pulp; 4, 
young layer of enamel de- 
tached from the enamel cells; 
5, dentine; fi, odontoblasts: 
7. part of the dentine pulp. 
Waldeyer. 
According to Kolliker and others, they 
excrete the dentine. The former view seems 
to have the most weight of argument in its 
favor, but it seems less likely that the odon- 
toblasts both make the matrix and send 
fibres into the tubulse. The view of Klein 
already given seems to be preferable, and in conformity with 
what we know of other connective substances. 
The separation of the tooth-sac from the mucous membrane 
is effected by the gelatinous tissue, which, gradually closing in 
the neck of the sac, finally cuts it off. The epithelium of the 
enamel cap is abundant and of various kinds; into it push a 
number of papillary processes downward from the gelatinous 
tissue. Later the enamel cap is changed into three membranes. 108 
MANUAL OF HISTOLOGY. 
The middle membrane is a peculiar cellular network, formed 
by the transformation of the middle epithelium layer into a 
network of cells, below which there is a deposit of a hyaline 
material. The inner membrane is formed of cylindrical epithe- 
lial bodies, which are called enamel-cells ; outside of them are 
one or more layers of polygonal cells ; they form the stratum 
intermedium of Hannover. The outer membrane is composed of 
several layers. Finally, the middle membrane disappearing, the 
outer and inner membranes are brought into close apposition. 
Development of the enamel.—This is formed by the enamel- 
cells (inner epithelium, Kolliker), presumably in the same 
way as the dentine by the odontoblasts. There is a direct con- 
version of the outer extremities of the enamel-bodies into en- 
amel. Kolliker, Hertz, and Kollmann, however, regard the 
enamel as an excretion from the enamel-cells. The former 
view appears the more natural, especially as the enamel-prisms 
are continuous with the enamel-cells, having the same form and 
shape. The successive stages of growth, it is believed, give 
rise to the transverse markings. 
Whether or not, in the interstitial substance of the enamel, 
there are corpuscular elements (Boedecker), is a matter that 
will require further investigation. The outer membrane even- 
tually gives rise to the cuticle covering the enamel. 
The development of the cement takes place precisely as 
bone is produced, viz,, from the periosteum, or, which is the 
same in this instance, from the fibrous tissue of the tooth-sac, 
the periodontium. 
BIBLIOGRAPHY. 
The following systematic works and journal articles may be consulted : 
Retzius. Muller’s Archives. 1837. 
Nasmyth. Med.-Chir. Trans. Yol. 33. 1839, 
Kolliker. Man. of Human Histology. 1853. 
Wenzel. Arch. d. Heilkunde. 1868. 
Henle. Anatomic. 1871. 
Stbicker. Manual of Histology. Am. Ed. 1873. 
Tomes. Manual of Dental Anatomy, Human and Comparative. Lond,, 1876. 
Owen. Comparative Anat. and Phys. of Vertebrates. 1866. 
Boedecker. Dental Cosmos. XXL, 409—416. Phil., 1879. 
Heitzmann, Microscopic Anat. of Human Teeth. Med. Rec., N. Y., 1879. XV., 
187. 
Klein. Atlas of Histology. 1879—80. CHAPTER IX. 
GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
We may gain a clear conception of the nervous system in 
its general outlines by remembering that it consists essentially 
of a series of delicate cords which, on the one hand, proceed 
from the nucleated bodies of the gray matter, conveying voli- 
tional impulses to the periphery of the organism ; or, on the 
other hand, of sensitive peripheral extremities that take up the 
impression of external objects and carry them back to the cen- 
tral gray substance. 
In either case both the conducting cords and the central 
corpuscles of the gray matter possess no distinctive differences, 
such as may be appreciated by the microscope, while, on the 
other hand, the peripheral termini appear under many different 
forms, the peculiarity of ending being dependent in part upon 
the type of tissue in which they are found, partly upon the 
office thejr have to perform, and partly upon other causes that 
are unknown to us. The nerve-centres are located in the brain, 
spinal cord, and in the ganglia of the cerebro-spinal and sym- 
pathetic system. 
The methods of nerve-terminations that have been described 
may be briefly enumerated here. They are by (1) peculiar 
terminal bodies, (2) loops, (8) networks, (4) end bulbs, (5) proto- 
plasmic bodies (cells), (6) free or pointed extremities. 
Nerve-fibres.—Of these there are three kinds that have 
distinctive differences; 1. The myelinic or medullated fibres. 
2. Fibres of Remdk. 3. Ultimate fibrils. Intermediate forms, 
such as have been described by various writers, under the names 
of protoplasmic processes, primitive fasciculi or naked axis- 
cylinders, varicose cylinders, etc., will be noticed in other con- 
nections. 
Myelinic fibres.—These are also known as the medullated. 110 
MANUAL OF HISTOLOGY. 
To the naked eye they appear white and glistening, and are 
the main constituents of the peripheric nerves, though they 
occur in less number in the sympathetic and also in the brain 
and cord. Each tibre is made up of three distinct parts ; {a) a 
central cylindrical cord, the axis-cylinder, about which is a (&) 
coating of soft homogeneous fatty material, called myeline 
(medulla, white substance of Schwann), forming for the axis- 
cylinder a sort of tubular sheath, while exterior to both is a 
delicate membrane or envelope (c), the sheath of Schwann or 
primitive sheath.1 These fibres run a parallel unbranching 
course, except near their termini or origin, and are surrounded 
by a connective-tissue coating of varying thickness. Their 
diameter varies also according to their situation and the degree 
of their tension or relaxation. In the nerve-trunks the average 
diameter lies between TV and yio millimetre. In the brain they 
are described as having sometimes a diameter of .millimetre, 
but it is difficult to determine the presence of a medulla in such 
small fibres. 
To study the properties of a myelinic nerve, we may take a 
portion of the sciatic from a frog that has just been killed. 
Having removed it with care and placed it in a drop of water 
on a slide, we should separate the fibres carefully with needles, 
taking care not to tear them. Then adjusting a covering 
glass, it will be seen that from the broken end of the nerve a 
soft substance is exuding (Fig. 43, 5); in a few minutes it is 
pushed off in the form of drops of irregular shapes (Fig. 48, c). 
This material is the myeline or medulla. It will be seen to re- 
fract the light strongly, and show concentric markings. It will 
also be seen that each fibre has a double contour and is divided 
at tolerably regular intervals by transverse divisions, which are 
now known as Manmed s nodes. (See Fig. 47.) Midway be- 
tween each node we may perhaps see an oval body surrounded 
by a broad expansion of protoplasm. In a few fibres we may 
even see that a fine thread-like process is projecting from the 
broken ends of the nerve-fibre—the axis-cylinder (Fig. 43, d)— 
while the whole fibre is enclosed by a delicate tightly investing 
membrane, the sheath of Schwann. Possibly we may also see the 
1 A most unfortunate source of confusion among histologists has arisen from the 
use of the word neurilemma, which by some is spoken of as synonymous with 
Schwann’s sheath (Frey), and by others as the connective tissue which binds the 
nerve-fibres together (Klein, Rutherford). We shall avoid the term altogether. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
oblique or arrow markings (incisures of Schmidt) (Fig. 48, f), 
which seem first to have been accurately described by Schmidt, 
of New Orleans, later by Lantermann of Cleveland, Shaw, and 
others. The same appearances can be also obtained by the use 
of iodized serum. 
The double contour is not visible in all the myelinic nerves, 
but is most marked where they show varicose swellings, a con- 
dition that is due to a preponder- 
ance of myeline at the enlarged 
point. From this fact and anoth- 
er, that the drops of myeline when 
separated from the fibre show the 
same double contour, it is argued 
that the double marking in the 
fibre is due to a refracting (double) 
of the myeline, and has nothing to 
do with the membranous sheath. 
These varicosities just mentioned 
are not to be confounded with the 
bulgings of the ultimate fibrils, or 
with the “necklace” appearances 
seen in the course of the fibres of 
Remak, both of which latter may 
probably be regarded as artificial 
productions, either from stretching 
in the act of teasing or from the 
imbibition of water. In the brain 
of the calf they are frequently seen, 
and they are said to be found in the 
intracranial part of the olfactory, 
optic, and acoustic nerves. The 
fibres in which this change occurs 
are usually quite small. 
Fig. 43, a, Myelinic fibre in a state of 
“ coagulation ; ” 6, myeline exuding from 
the broken end of the fibre; e, drops of mye- 
line separated from the nerve-fibre; d, axis 
cylinder; e, nucleus of Henle’s sheath; /, 
arrow markings. 
Staining in piero-carmine.— 
This reagent has been recommended by Ranvier. It is satis- 
factorily prepared by Rutherford’s process.1 Taking precau- 
tions not to injure the nerve in removing it, mount in the solu- 
IHe takes 100 c.c. of a saturated solution of picric acid. Next he prepares an 
ammoniacal solution of carmine by dissolving one gramme in a few c. c. of water, 
with the aid of an excess of ammonia and heat. He then boils the picric acid solu- 
tion on a sand-bath, and when boiling adds the carmine solution. The mixture is 112 
MANUAL OF HISTOLOGY. 
tion. The nuclei will then be stained a brick-red, while the 
sheath of Schwann, and, in fact, the whole nerve, will be stained 
yellow. It is said that, if the axis-cylinder projects, it will be 
stained a bright red, though twenty-four hours may be required 
to effect the staining. In my hands picro-carmine has not 
proved so successful a coloring agent as some others. 
Staining with the nitrate of silver.—The sciatic or any 
peripheral nerve may be employed. Expose it without re- 
moval in a frog that has Just been killed. Then dry up all 
fluid from about it, and pour on a solution of the nitrate (1 to 
1,000). In this way the nerve-fibres will be made rigid. They 
are then to be removed with a pair of delicate scissors, and 
placed in a flat vessel containing a little more of the solution. 
After a few minutes the nerve will look turbid, and then it 
should be cut out and washed in distilled water, and exposed 
to the sunlight. In a variable time (ten to fifteen minutes) the 
turbid appearance will give way to a brown coloration. Exam- 
ining a single funicu- 
lus or bundle in gly- 
cerine, it will be seen 
that it has an endothe- 
lial coating of one or 
more layers (Fig. 44). 
If another funiculus 
be separated with fine 
needles,1 the same care 
being taken to spread 
the fibres apart and not 
tease, and so lacerate 
them, it will be seen 
that ieach fibre con- 
tains a series of Latin 
crosses at certain pretty regular intervals. The transverse bar 
of the cross corresponds to the “annular constriction” seen 
in Ranvier’s node, while the axis-cylinder forms the longitudi- 
nal bar. Close observation with high powers will show that 
this latter is marked by transverse lines of a dark brown or 
Fig. 44.—Funiculus or Nerve Bundle covered with Endothe- 
lium (Epithelium). From the sciatic of the frog.—Hartnaok, 
object. 4, oc. 2. 
then evaporated to dryness, the residue dissolved in 100 c.c. of water, and filtered. 
If the solution is not clear, he adds more ammonia, evaporates, and then dissolves as 
before. 
1 Milliners’ are the best. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
biack {Frommanris lines). It appears probable, as Ranvier 
explains, that, owing to the break in the myeline, at the “ an- 
nular constriction,” the particles of silver gain an entrance to 
the axis-cylinder at this the only unprotected spot. If the 
action of the salt is long con- 
tinued, the axis-cylinder is col- 
ored for a somewhat longer 
distance. The transverse bar 
seems to be formed of two 
conical segments set base to 
base. The position of this bi- 
conical segment usually cor- 
responds in position with the 
“annular constriction,” but 
it would appear that they may 
be separated, for, when the 
tissue of the nerve has been put upon the stretch, the biconical 
segment, may be drawn away from the annular constriction. 
(See Fig. 45.) 
Fig. 45.—a, Eanvier’s disk; 6, Frommann’slines; 
c, nucleus of interannular segment. 
Now, as Schwann’s sheath is understood to end at the an- 
nular constriction, where it is cemented to the next adjoining 
segment just as epithelial cells are joined together, the biconi- 
cal disk may belong to the axis-cylinder exclusively, and 
merely constitute a dividing line between its segments. Ac- 
cording to Engelmann, the axis-cylinder is divided up into 
portions corresponding with the interannular segments. 
According to liawitz, Schwann’s sheath does not end at the nodes, but is 
continuous with the sheath of the adjacent interannular segment. 
Staining of the nerve in osmic acid—semi-desiccation.— 
Osmic acid is one of the most valuable reagents for histological 
work, and the method now to be described (a modification of 
Ranvier’s1) succeeds well. Take the frog’s sciatic, or any other 
peripheral nerve, carefully remove a portion with the surround- 
ing tissue, keep the whole extended with pins, upon a fiat bit 
of cork, and then dip it into a vessel containing a 1 per cent, 
watery solution of osmic acid.2 The vessel is then to be exposed 
to the light. The whole nerve will be more or less thoroughly 
1 Legons sur I’Histologie du Systeme Nerveux, Paris, 1878. 
s The solution should, of course, have been kept in a dark bottle away from the 
light. 114 
MANUAL OF HISTOLOGY, 
stained in a few hours. The external portions, however, will 
be stained in a few minutes, and they may be removed care- 
ful separation with tine needles. To mount, take a glass slide 
and slip it under the nerve-tibres, while the needle is employed 
to carry them up on to a dry part of the slide 
where they can be placed side by side. Then 
remove the excess of water with bibulous paper, 
and let the fibres get so dry that they adhere 
to the slide. Place about them a ring of tis- 
sue-paper, so that when the cover is adjusted 
it will not press upon the fibres. Fix the cover 
at different points with paraffine, then put a 
drop of glycerine upon one side, and a drop of 
water upon the other. The union of water and 
glycerine should be allowed to go on for 
twenty-four hours in a damp place. The con- 
strictions and arrow-markings are usually well 
seen. The nuclei also are occasionally to be 
found in a niche of the myeline. These bodies, 
however, are better seen in specimens that have 
been a short time (fifteen or twenty minutes) 
in osmic acid, and then in picro-carmine a few 
hours. It still is a question among histologists 
whether the arrow-markings are artificial or 
not; each of the sections lying between the 
markings is called the cylindro-conical segment 
{HoJilcyUnder, Kuhnt). (See Fig. 48.) 
Transverse sections of myelinic nerves.— 
Certain points are best seen by making trans- 
verse sections. Prepare the sciatic of a frog or 
any of the human peripheral nerves by im- 
mersing a few days in a sherry-colored solution 
of bichromate of potash, or in Mueller’s fluid,1 
and then in 90 per cent, of alcohol, until the tis- 
sue is hard enough to cut. Then it is to be 
mounted in the microtome with wax and oil of 
about its own consistence. Sections are to be made with the 
razor; or it may be mounted in elder-pith in the following 
way : bore out from the centre of the pith-cylinder a cylindri- 
Fig. 46. Human 
myelinic nerve : a, In- 
terannular segment; b, 
Ilanvier's node ; c, nu- 
cleus of the interannu- 
lar segment surround- 
ed by granular proto- 
plasm ; d, flenle’s 
sheath, with nucleus. 
1 Tty well-known eye-fluid, of which the composition is : Bichromate of potash. 
3to 2i grammes; sulphate of soda, 1 gramme; distilled water, 100 grammes. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
cal hole a little larger than the trunk of the nerve, then im- 
merse the whole in water, and the pith will begin to swell. As 
soon as it has firmly embraced the nerve, sections may be 
made with the knife. Ammonia-carmine will stain the axis- 
cylinder well, but the outline of the cut will appear irregular 
rather than round. This appearance is doubtless artificial. In 
my hands, borax-carmine 1 has proved much better than the 
ammonia-carmine, as it diffuses very little, and much of the 
excess may be removed by dilute acetic acid (about J percent.), 
in which the specimen should remain, from a few seconds to a 
minute or two, until it has become bright to the eye. The fur- 
ther steps in the process of making a permanent preparation 
are the same as those for other specimens; i.e., it may be 
mounted in glycerine and water, or clarified by clove-oil and 
mounted in dammar varnish or Canada balsam. 
Preparation toy the bichromate of ammonia.—Ranvier em- 
ploys of this a 2 per cent, solution,, allowing the specimen to 
remain, with frequent changes of the 
fluid, from two or three months to a 
year. The sections are to be stained 
in ammonia-carmine or picro-carmine, 
and mounted in glycerine. It will 
then be seen that immediately about 
the axis-cylinder is a sheath. This is 
called by Ranvier the sheath of Mauth- 
ner, from the author who described it. 
(See Fig. 46, h.) Specimens prepared 
in the ordinary way, by long immer- 
sion in Mueller’s fluid alone, or sub- 
sequently in the chromic acid solution (gr. ij.— f j.) and stained 
with ammonia-carmine, occasionally show the same thing. 
Flo. 47.—Cross-section of the hu- 
man cord just below the decussation : 
a, axis-cylinder ; b, sheath of Mautn- 
ner. 
Sometimes histologists find that embedding in gum succeeds 
best in securing these transverse sections of nerves. The diffi- 
culty of the task is one of considerable moment. The method 
is as follows : Take a fresh nerve, harden it in osmic acid (1 per 
cent., if it is desirable to expedite the process, or TV per cent, 
if it is not necessary to conclude the examination the same 
day). Then, when the nerve is thoroughly blackened all through, t 
1 The powder is prepared by Eimer & Amend, of this city (305 to 311 Third 
Avenue), according to Arnold’s formula. The strength required is gr. xv.— §j. 
distilled water. 116 
MANUAL OF HISTOLOGY. 
it is to be immersed in water for a few hours ; then in 90 per 
cent, alcohol, and then in a weak solution of gum-arabic, 
which fills the interstices between the bundles, and finally in 
strong alcohol (95 per cent.), which hardens the gum sufficiently. 
The sections, cut as thin as possible, should be placed on a 
slide to remove the excess of alcohol, which may be done with 
filter-paper. A drop of water is then to be added; about 
the cover put a few drops of carbolized water ; remove to a 
damp place. At the end of twenty-four hours the gum will 
have dissolved, and then the glycerine may be allowed to enter 
slowly without displacing the elements (Ranvier). 
In examining such cross-sections, the medullated nerves will 
present various diameters, and the contour of the myelinic 
sheath will vary in width and outline according as the cut 
comes through the broadest part of the arrow-marking, or 
through the thin overlapping parts. (See Fig. 48.) If the cut 
chances to pass close to the annular constriction, no myeline 
will of course be seen. For these reasons, the cross-sections of 
such nerves, when stained with osmic acid, are very different. 
Modern conceptions of myelinic nerves.-—The specimens 
that have been studied according to the methods given will not 
have shown any termination of the nerves, or any division, 
either into trunks of any considerable size or into the fibrils of 
which they are said to be composed. They do, however, as we 
have already said, divide both near their origin and near their 
termination. It is presumed that each fibril of which the axis- 
cylinder is composed passes directly through from its point of 
origin of the nerve-centres, to its final point of distribution, 
without branching. It is difficult, however, with the instru- 
ments in ordinary use, to see any distinct marks of fibrillation 
in cross-sections of the axis-cylinder, and it is in them that we 
should expect to see them best. The ideas of Ranvier are well 
worthy of consideration, as he has given more form and solid- 
ity to our conception of the intimate structure of a myelinic 
nerve-fibre than any previous writer. According to him, each 
section of nerve between the annular constrictions represents 
an ultimate morphological element. It is, in fact, a tubular 
cell, whose proper external portion (the membrane of the cell, 
according to common phraseology) is the sheath of Schwann, 
while the myeline or medulla fills the interior, just as in adi- 
pose tissue a globule of oil fills out and distends an ordinary GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
connective-tissue corpuscle. Each of these bodies, which he 
calls an interannular segment, begins and ends at the constric- 
tion. It contains a single ovoid flattened nucleus, which fills 
a niche in the myeline, and is surrounded by a broad, thin ex- 
pansion of protoplasm (the body of the corpuscle). The axis- 
cylinder has nothing to do with this body that we have de- 
scribed, except that it pierces it. Instead of stopping short at 
each constriction, it goes on indefinitely. As we have already 
seen, the annular constriction and the biconical disk are not 
always at the same point, which argues strongly for Ranvier’s 
views. The myelinic sheath probably protects the delicate 
fibre from external injury, but whether it also insulates it, is 
problematical. In the foetus all nerves are devoid of myeline. 
Fibres of Remak.—These are called by some the amyelinic 
or non-medulla ted fibres, by others the pale, gray, or gelati- 
nous fibres. The term Remak’s fibres has come into use re- 
cently as the distinctive name for certain nerve-fibres abound- 
ing in the sympathetic, as distinguished from others which 
also contain no myeline, and are found in the cranial portions 
of the optic, auditory, and olfactory nerves. Each fibre is 
marked with oval nuclei at pretty short intervals, and has an 
indistinct longitudinal striation, probably the evidence of fibrils 
such as are believed to exist in the axis-cylinder. The nuclei 
are imbedded in a homogeneous sheath. There being no breaks 
in the continuity of the fibre, there can be no sheath of Schwann 
in the sense that has been described. In diameter each fibre va- 
ries between 2J~O and T| o millimetre. In 1838 Remak.first called 
attention to them, but his views were received with disfavor. 
More recently, Max Schultze, Frey, Leydig, and Henle have 
joined in representing them as long, cylindrical, continuous, 
slightly striated, and dotted with nuclei. 
The fibres of Remak are found in great abundance in all 
the nerves of the organic system, but they also exist in all the 
mixed nerves, varying with the kind of nerve and the animal. 
They are not found in special nerves. The pneumogastric of the 
cat is well adapted for the study of them, as the myelinic fibres 
are present in considerable quantity, and make the mechanical 
separation of the bundle easy. Associated with them, fibres are 
often seen, that are shown in Fig. 48, c. They are delicate, 
run a course, and sometimes exhibit curious varicosities 
(a), (necklace appearance). The nuclei are placed at about the 118 
MANUAL OF HISTOLOGY. 
same distances apart as in the other form of fibre already men- 
tioned. 
Preparation in osmic acid and picro-carmine.—Remove 
the pneumogastric in the following way, from a cat that has 
just been killed: Having exposed the nerve, slip under it in 
situ a long narrow strip of cork, to which, pin down the nerve 
with some adjacent tissue, all of which may be removed at 
once and placed in a solution 
of osmic acid (1—1,000) for 
twenty-four hours ; the nerve 
may then be separated from 
its attachments and placed 
in the picro-carmine solution 
for still another twenty-four 
hours. The excess of the col- 
oring agent may be removed 
by dipping for a few seconds 
in acetic-acid solution Q- per 
cent.), and then the nerve 
may be placed in alcohol, 
afterwards in water, and fin- 
ally mounted in glycerine. 
It will be seen that the nerve- 
fibres are stained a reddish 
yellow, while the nuclei are 
brick-red. The picric-acid 
yellow is apt, however, to 
diffuse. Careful separation 
of the fibres may show that 
they branch, as shown in Fig. 
48, A, B; and yet this char- 
acteristic, which Ranvier in- 
sists upon, is by no means 
easy to see in most of the fibres, in fact it requires much care- 
ful work before it is apparent. The myelinic nerves will be dis- 
tinguished by their greater average size, their dusky, granular 
medulla, broken at points, and by the axis-cylinder, which, 
if it does not project, may be seen winding spirally along be- 
neath its medullary coat. In them, too, as a rule, each in- 
terannular segment contains but one nucleus. 
Fig. 48.—Fibres of Remak. A, Pneumogastric 
of the cat—hsematoxylon specimen ; a, nerve nu- 
clei ;6, appearances of branching; c, connective- 
tissue sheath. B, Same. Picro-carmine specimen. 
The branching in this case is more evident. C, 
Same—hiematoxylon specimen. The necklace ap- 
pearance is shown at a. 
Preparation of Remak'1 s fibres in Juematoxylon.—One of GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
the most rapid and successful methods is by the use of hsema- 
toxylon. The pneumogastric nerve of a cat is removed and 
immediately placed in the hsematoxylon solution; then, after 
thoiough staining, which may only take a few minutes, in 
dilute acetic acid (£ per cent.), and finally mounted in gly- 
cerine. In this way the nuclei will be stained a beautiful pur- 
ple, while the fibres will be unaffected. The number of nuclei 
and absence of medulla will serve to distinguish the fibres of 
Remark from the medullated. It is difficult by any method of 
preparation to see that there are any precise limits to the lon- 
gitudinal lines in the fibres, i. e., that the striation is due to 
little, short, narrow rods, lying side by side (Ranvier), The 
nitrate of silver demonstrates no transverse markings and no 
constrictions or crosses. There is but little likelihood in these 
specimens to mistake the fibres for connective-tissue bundles. 
In the first place, the nuclei, and what cell-bodies happen to 
be about them, of the one, are small, flattened, ovoid bodies 
occurring at pretty regular intervals, while the connective-tis- 
sue corpuscles are usually larger, longer, and, though they 
may appear oat-shaped, when the side is turned to the observer, 
are broad plates with irregular edges when seen flatwise. In 
the second place, the fibres run their course in long, narrow 
bundles, as no connective tissue does. 
Ganglionic bodies.—Of these there are three kinds: 1. 
Those that are connected with the spinal and some cerebral 
nerves. 2. Those found in the gray substance of the brain and 
spinal cord. 3. Those in the ganglia of the sympathetic sys- 
tem. These bodies are of such large size that they may often 
be seen with the naked eye. In the human species they are 
usually in close connection with the origin of the nerves, though 
they also may be interspersed at points through the course of 
the fibres or may be present near their points of distribution 
{ganglia of Auerbach). Their immediate connection with the 
nerve-fibre is made in the following ways: 1. A large process, 
which does not at first appear to branch, passes off, and is 
continuous with the axis-cylinder. 2. Fine branches are given 
off from one or more corpuscles, and, uniting, contrive to form 
a nerve-fibre (either a fibre of Remak or a myelinic fibre). 3. 
These branches after combination may pass through a gangli- 
onic corpuscle, which then is called bipolar (Gerlach, Wal- 
deyer). In the sympathetic system we have the unbranched 120 
MANUAL OF HISTOLOGY. 
process and the superficial or spiral fibre, which corresponds to 
the branched fibre of the ganglionic bodies of the brain and 
spinal nerves. 
Ganglia of the cranial and spinal nerres.—These organs, 
which appear to the naked eye as nodular enlargements of the 
nerves with which they are connected, consist of groups of 
peculiar large corpuscles which are interspersed among the 
nerve-fibres. In shape they are usually large and ovoid, or 
pear-shaped. About and between them are bands of connective 
tissue studded with nuclei, forming for each separate body a 
kind of capsule ; the vascular supply to them is liberal. The 
contents of these bodies are soft, elastic, and beset with gran- 
ules. They have a large, globular, or ovoid nucleus or nucleo- 
lus, and may appear to have no process, or to be unipolar or 
bipolar, as in the lower animals.1 
Examination of the Gasserian ganglion in the frog.— 
Take a frog that has just been killed, or, better still, one that 
has been some time in Mueller’s fluid; trace the fifth nerve 
into the skull. On it will be seen, just within the bone, a yel- 
low enlargement. This is to be removed with forceps and 
teased with needles. The ganglionic bodies usually appear to 
have no processes (apolar), but they probably have one or more, 
and the apparent absence of them is because they have been 
torn off in teasing. 
Examination of the ganglia of the spinal cord.—Take the 
cord of a bullock, and prepare it while fresh, or after it has 
been a greater or less time in Mueller’s fluid, or a weak so- 
lution of the bichromate of potash (gr. xv.— | j.). Having cut 
it into transverse segments, the gray substance may be easily 
seen. Snip out with fine curved scissors small pieces from the 
anterior horns in the lumbar regions where the corpuscles are 
very numerous ; if the specimen be fresh, immerse in osmic 
acid (1—1,000) for twenty-four hours. Then, by careful brush- 
ing in water with the camel’s-hair brush, or by teasing, or agi- 
tation in a test-tube with a little distilled water, some of the 
ganglionic corpuscles will be successfully removed. They will 
be seen to vary much in size, and be multipolar, i.e., they will 
exhibit a very large number of branches {Deitef sprotoplasmic 
1 According to Key and Retzius, they are probably all unipolar. Stud, in der 
Anat. d. Nerven-Syst., 2 Halfte, Y. and H.’s Jahresb., 1878. GENERAL HISTOLOGY OE THE NERVOUS SYSTEM. 
processes) which divide and subdivide, and, it is said, form a 
network which unites with a similar one proceeding from the 
ganglionic bodies of the posterior roots. 
There is, in addition, a single straight process (naked axis- 
cylinder), which, proceeding outward, soon receives a medul- 
lary sheath. The nucleus is very large and circular, and usu- 
ally displays a nucleolus. The contents of the body of the 
corpuscles are more or less granular, and a mass of pigment in 
granules is usually seen piled up in some one portion. The 
corpuscles thus separated may be preserved in glycerine and 
water, or, after staining in borax-carmine, in dammar varnish 
or Canada balsam. In the posterior horns the corpuscles are 
similar in character, but smaller. Gerlach claims that the 
ganglionic bodies of the anterior horns are connected together 
through networks formed of the branching processes given off 
from each. Carriere, working under Prof. Kollman, of Mu- 
nich, has examined the spinal cord of the calf in the fresh con- 
dition, and has satisfied himself that the ganglionic corpuscles 
are connected together by their fine processes, being thus in 
agreement with Stilling, Wagner, Remak, and many others.— 
Arch.f. mikroskop. Anat., xiv., 2, 1877. 
Ganglionic bodies in the human brain.—Thin sections 
made through the cortex of the human brain show that there 
are conical ganglionic corpuscles of medium size, whose base 
is directed toward the white substance, and apex toward the 
superficies. From either end processes are given off, from the 
broad end several, and from the apex a single one ; both subse- 
quently branch. In the upper strata the corpuscles are small- 
est. Disseminated throughout this substance are two other 
forms of corpuscles, one star-shaped (spider-cells),1 and the 
other the lymphoid corpuscles that belong to all tissues of the 
body. Possibly the spider-cells, which have a variable number 
of processes, are the cells of the neuroglia. Brush-cellss have 
also been described. Perhaps they should also be regarded as 
a variety of the spider-cells. 
Ganglionic bodies of the sympathetic system.—They occur 
either singly or in groups, interspersed among the nerve-fibres, 
or in lines, or form enlargements in the nerve-plexuses, as 
1 Described by Jastrowitz. 
2 Arch. f. mikrosk. Anat., 1874, LXI., p. 93. 122 
MANUAL OF HISTOLOGY. 
in the digestive tract. Preparations of the cceliac ganglion of 
the frog may be made according to.the methods that have al- 
ready been described. The aorta and bulbus arteriosus of the 
frog are recommended by Klein, and the gold method is the best 
to show them. It was in these corpuscles of the green tree-frog 
that Beale noticed a spiral fibre. It was a delicate one, wind- 
ing round the axis-cylinder, finally going off in an opposite 
direction. He also thought, from an examination of the gan- 
glia in the mammalia, that the same fibre existed in them. Sub- 
sequently Julius Arnold corroborated his views, and even de- 
scribed a network of fibres which was connected with the 
nucleolus, and extended through the corpuscle, at its final 
exit forming the spinal fibre. Recent observers, however, have 
failed to confirm Arnold’s opinion, and even the existence of a 
spiral fibre is held to be in doubt.1 These corpuscles, which are 
either globular or oblong, may appear to be apolar, unipolar, 
bipolar (when two processes are given off in the opposite direc- 
tions), or multipolar (when two are given off in the same direc- 
tion, or several are given off in various directions). 
Meissner'1 s plexus.—This network, named after its dis- 
coverer, is situated in the submucous tissue, and consists of 
nerve-bundles of medium size, which have nodular enlarge- 
ments studded with nuclei at certain points. An excellent 
way of securing them is the following : Take a piece of cat’s 
intestine, three or four inches in length; cleanse thoroughly 
by passing through it a stream of water; then ligate one ex- 
tremity. Fill an ordinary two-ounce syringe with a solution of 
the chloride of gold (i°). Slip the nozzle into the other end of 
the intestine, and, tying it in, inject with such force as to dis- 
tend the gut to its utmost extent without bursting. Then pass 
another ligature round the gut beyond the nozzle, and draw it 
tight. Remove the syringe, and place the specimen in an open 
vessel containing the same solution, but allowing fully one- 
half of it to be uncovered by the liquid. After twenty-four 
hours the part thus exposed will have taken a mauve or violet 
color. Then remove from the liquid, and open with scissors, 
let it partly dry, and, seizing the mucous membrane with the 
forceps, tear it off in pieces. The submucous tissue will then 
1 Key and Retzius did not find the spiral fibre in the human species, but in the 
frog occasionally. Op. cit. Many other excellent observers agree with them. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
be exposed, and small bits are to be tom out in a similar way. 
They may be mounted in glycerine or dammar varnish. The 
nerve-trunks can be readily seen; they will contain, on an 
average, from two to three fibres perhaps, and form a large- 
meshed plexus. The ganglionic enlargement may be found 
where three or four bundles meet, or in the course of a single 
bundle. The diameter of the enlargement is three to five times 
the size of the bundle. 
Auerbach"* s plexus, called after its discoverer, is seen by 
taking the same specimen, and tearing out thin laminae from 
the muscle, at the junction of their longitudinal and trans- 
verse coats. The ganglionic bodies are nodular, and contain 
numerous nuclei. It is said that they may be isolated by 
immersion of the muscular tissue eight to ten days in a 10 per 
cent, solution of common salt. G-uinea-pigs furnish the best 
specimens,1 There are both coarse and fine networks. 
Termination of nerves.—There are various methods which 
have been described, and these are : 1, by undivided or free 
endings (tendons, conjunctiva); 2, by end bulbs (cornea); 8, 
by terminal loops ; 4, in corpuscles (seminal canals—Letzerich) ; 
5, by networks (peritoneum); or, finally, 6, in a special appa- 
ratus (Pacinian or Meissner’s corpuscles). When nerves termi- 
nate by networks, the meshes may be formed from the medul- 
lated fibres, or those of Remak, and may consist of one or more 
fine fibrils. They have been found in the skin, and are to be 
seen in the submucous tissue of the intestines, in the cornea, 
and elsewhere. Termination by bulbs has been closely investi- 
gated by Krause. The bulbs are described as having a diam- 
eter of gL- millimetre, and ovoid-shaped in man, with a thin 
capsule of connective tissue. One or more fibres appear to 
enter the bulb, and, penetrating some distance, end in a knob. 
They have been found in the conjunctiva, in the mucous mem- 
brane of the floor of the mouth, lips, soft palate, and tongue, 
and in the glans penis and clitoris. In the cavity of the mouth 
they are placed in the papillae. The bodies Krause has ob- 
served in the clitoris are somewhat peculiar ; they are variously 
shaped, and have a mulberry-like surface. 
These corpuscles, about which there has been so much dis- 
cussion, and which some excellent observers (Waldeyer, Arnold) 
1 Frey : Das Mikroskop., Leipzig, 1877. 124 
MANUAL OF HISTOLOGY. 
had failed to see, were investigated a few years ago by Long- 
worth, of Cincinnati, and their existence established as a matter 
of no donbt. He took the human eye, freshly removed with 
the conjunctiva, and made the examination immediately. At- 
taching the conjunctiva with threads, so that it preserved its 
natural tension, he immersed it in a £ per cent, solution of os- 
mic acid, or exposed it to the vapor of the same solution. 
After twelve to twenty-four hours the membrane was deeply 
stained, and the epithelium could usually be removed with 
a brush or the finger-nail. Next, a thin piece of cornea was 
removed and examined in water, or in 1 to 2 per cent, acetic- 
acid solution. It was then mounted in glycerine. This method 
was preferred to the gold chloride. In some conjunctivse they 
were found almost entirely absent; in others, or in certain por- 
tions, quite numerous. The entire interior was seen to be filled 
with nucleated corpuscles. Waldeyer, in commenting on the 
work of Dr. Longworth, agreed to it fully, and retracted his 
former opinions. He places these bodies intermediate between 
the tactile and Pacinian bodies. 
The tactile corpuscles of the skin (called also Meissner’s 
or Wagner’s corpuscles) are to be seen in the papillae, and 
especially well in the tips of the fingers, and in the internal 
genitals. They have a length of about millimetre. Speci- 
mens hardened and preserved in the ordinary way show them 
well. They are oblong, rounded, and marked by transverse 
wavy lines. A nerve-fibre may be seen running into their 
centre. 
The Pacinian bodies, discovered by Yater, in 1741, but first 
carefully described by Pacini, of Pisa, are oval or pear-shaped 
bodies, attached to the nerves like berries to a stem. They are 
found in the subcutaneous tissues of the finger (Kdlliker), in 
the labia majora, prostate, corpora cavernosa, and in many 
other places. They are seen to the best advantage, however, 
in the mesentery of the cat, where they are so large as to be 
easily visible to the naked eye. 
Cut out a small piece of the mesentery, place it in a weak 
solution of osmic acid (1—100), and after a few minutes, when 
it has become brown, detach the capsule carefully with needles. 
Mounting at once in glycerine, the whole interior of the Paci- 
nian will be superbly shown, constituting one of the most beau- 
tiful specimens in histology. The medullated nerve may be GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 
seen winding in at one end (Fig. 49), covered with a dense coat- 
ing of connective tissue, and accompanied by a small artery. 
After penetrating a variable distance, it leaves its medulla and 
is continuous with a straight fibrillated band that is called the 
core. It terminates in one or more granular expansions, appar- 
ently. In two cases, how- 
ever, I saw the nerve passing 
through the body, giving off 
its medulla on entering it, and 
assuming it again on leaving. 
This has been observed by 
Klein, Pappenheim, and oth- 
ers. Round about the core, 
forming a series of pretty reg- 
ularly oval markings, are con- 
centric tunics. Toward the 
periphery they are at a pret- 
tjT- even distance apart. Be- 
tween them, applied closely 
to the tunics,1 are small ovoid 
nuclei. The spaces between 
the lamellae are probably 
filled with a clear fluid. In 
my experience these bodies 
are not successfully pre- 
served in glycerine, even after 
hardening in osmic acid. The 
chloride of gold may answer 
better. 
Nerve - terminations in 
muscle are quite easily seen. 
It is only necessary to take a 
bit of muscle from, the thigh 
of a frog Just dead, and immerse it in dilute acetic acid, and 
then in glycerine. When the tissue is thoroughly transpa- 
rent, as it will be in a few minutes (ten or fifteen), there will 
be little difficulty in finding a medullated nerve, and then in 
tracing it into a muscle-fibre. Reaching the sarcolemma, it 
Fig. 49.—Pacinian body from the cat’s mesentery. 
1 According to Schaefer, the nuclei belong to epithelioid corpuscles which cover the 
tunic on both sides. Practical Histology, p. 134; Quarterly Microscop. Joum., 
1875. 126 
MANUAL OF HISTOLOGY. 
penetrates it at a prominence {Doyerd s eminence). From this 
point it divides into librils, which form delicate networks, and 
one, or possibly two filaments will be seen to enter an irregular 
body placed in the centre of the fibre. This body is highly 
nucleated, and may without much difficulty be distinguished 
from the muscle nucleus, which lies either on the bundle or in 
it. This body is called the motorial plate. It is not certain, 
however, that the ultimate fibrils actually end there, for in 
some instances one is in connection with one side, and one with 
the other. Varicosities are described in the primitive fibrils 
when osmic acid or chloride of gold is used. 
Gschleiden, of Breslau, one of the most recent writers on 
this subject, has traced (in the leech) the ultimate fibrils to the 
cement substance between the contractile muscle-corpuscles 
(unstriped muscular tissue). He never saw them end in plates 
or in networks. Ganglion-cells are closely attached to the 
fibres near their termination, and they may be unipolar, bi- 
polar, or even multipolar, the former being the most numer- 
ous. 
Termination of nerves in epithelial bodies has been de- 
scribed by a good many observers. The demonstration of such 
endings, however, is extremely difficult. The ultimate fibrils 
are liable to be confounded with elastic tissue, possibly with 
connective-tissue fibres. To be quite sure of their character 
they should be traced into connection with nerve-trunks, on 
the one hand, or ganglionic bodies on the other. 
Connective tissue of nerves.—-In our description we have 
adhered to the idea that the sheath of Schwann is the one that 
immediately incloses the medulla, without any intervening 
substance. Eanvier has called the first sheath, exterior to 
Schwann’s, “the sheath of Henle.” (Pig- 43, e.) 
The term perineurium is often applied to the sheaths of the 
funiculus or bundle. The connective tissue separating the 
funiculi in a large trunk has been called the endoneurium, 
while epineurium is the great sheath of the whole trunk. 
Each bundle or funiculus, the smallest element that we see in 
making a gross dissection of a nerve, is covered with one or 
more layers of endothelium, forming a special sheath. These 
funiculi do not run parallel without anastomosing, but two, 
joining, form a third, which again divides. 
There is much practical difficulty in the way of giving pre- BIBLIOGRAPHY. 
else limits to these sheaths, from the fact that they are apt to 
be continuous with one another, while one or more may be 
absent, according to the size or quality of the nerve. 
BIBLIOGRAPHY. 
Cohnheim. Virchow’s Archiv. Vol. XXXVIII., p. 343. 1867. 
Cleveland. Ueber d. feineren Ban d. Markhiilt. Nervenfasern. Arch. f. mikrosk. 
Anat., 1870. Vol. XIII., p. 1. 
Schultze, Max. Strieker’s Histology, p. 117. 1873. 
Schmidt. On the Construction of the Dark or Double-bordered Nerve-fibre. 
Month. Micros. Journ., May 1, 1874. 
Long worth. Arch. f. mikrosk. Anat. Vol. IT. 1875. 
Schaefer. Practical Histology. Quart. Micr. Journ., p. 134. 1875. 
Krause. Arch. £. mikrosk. Anat. Vol. XII. 1876. 
Shaw. Some Peculiarities in the Myelinic Peripheral Nerves, etc. Jour, of Nerv. 
and Ment. Dis., Jan., 1876. 
G-schleiden. Arch. f. mikrosk. Anat. Vol. XIV. 1877. 
Ranvier. Lecons sur I’histoire du systeme nerveux. 1878. 
Key and Retzius. Stud, in d. Anat. d. Nerv.-Syst. V. & H.’s Jahresb. 1878. 
His, W. Arch. f. Anat. u. Phys., p. 455. 1879. 
Rawitz, B. Arch. f. Anat. u. Phys. 1879. 
Ruhpf. Zur Histol. d. Nervenfaser, etc. Unt. d. Phys. Inst. d. Univ. Heidelberg. 
Vol. 11. 
Schultze, H. Axencylinder u. Ganglienzelle. Arch. f. Anat. u, Phys. 1879. 
Kuhne, W. Zur Histol. d. motor. Nervenendig. Unt. d. phys. lust. d. Univ. Heidel- 
berg. Vol. IT. 
Hesse, Fr. Zur Kennt. d. peripher. Markhalt. Nervenfaser. Arch. f. Anat. u. 
Phys. 1879. 
Kuhne, W., and Steiner, J. Beobacht. ueber Markhiiltige u. Marklose Nerven- 
fasern. Unt. d. Phys. Inst. d. Univ. Heidelberg. Vol. 111. 
His, W. Ueber d. Anfiinge d. peripher. Nerven-System. Arch. f. Anat. u. Phys., 
p. 455. 1879. 
Waldeyer. Ueber die Budig. d. sensiblen Nerven. Arch. f. mikros. Anat. Vol. 
XVII., pp. 367-383. 1880. 
Ranvier. Lecjons d’anat. gen. App. nerveux term., etc. Paris, 1880. 
Krause, W. Die Nervenendigung in den Tastkorperchen. Arch. f. mik. Anat. 
XX. 313-331. 1881-83. 
Lustig, A. Ueber die Nervenendigung in den glatten Muskelfasern. Sitzungst. 
d. k. Akad. d. Wiss., math, naturw. cl. 3. Abtheil. Wien. LXXXIII. 186- 
194. 1881. 
Wolff, W. Ueber freie sensible Nervenen digun gen. Arch. f. mikr. Anat. XX. 
383-413. 1881-83. 
Pfitzner, W. Nervenendigungen im Epithel. Morphol. Jahrb., Leipzig. VII. 
736-745. 1883. PART 11. 
CHAPTER X. 
MUSCULAR FIBRE. 
THOMAS DWIGHT, M.D., 
Instructor in Topographical Anatomy and in Histology at Harvard University. 
The physiological attribute of muscular tissue is contrac- 
tility. This may or may not be under the control of the will. 
The structure of voluntary muscular fibre is very different from 
that of the involuntary. 
This distinction, however, is not absolute. The muscular 
fibre of the heart presents a structure intermediate between the 
two typical forms. Striped fibres are found in some places, as, 
for instance, in the upper part of the oesophagus, over which 
most people have little or no control. There is also an un- 
doubted difference in the manner of contraction among volun- 
tary muscles. Whether this is associated with a difference of 
structure is an interesting but very uncertain question that 
will be alluded to later. 
INVOLUNTARY MUSCULAR FIBRE. 
Unstriped muscular fibre is shown with great advantage in 
the bladder of the frog. It should be stained with gold chlo- 
ride, logwood, or carmine.1 After the specimen has lain two 
1 If one’s object is to study the muscular tissue only, gold has no advantages over 
the other agents, and should not be used, because it is less certain. The writer has 
obtained remarkably beautiful stainings of the bladder by using carmine, following 
Beale’s method. INVOLUNTARY MUSCULAR FIBRE. 
or three days in glycerine, the lining epithelium is easily 
brushed off. The bladder of the frog is peculiarly favorable, 
because it affords an opportunity of studying the fibres, both 
Fig. 50. 
Fig. 51. 
Fig. 52. 
Fig. 50.—Muscular fibres treated with serum. Fig. 51.—Muscular fibres from the muscular tissue 
of the intestine, isolated by means of nitric acid. Fig. 52.—Muscular fibres from a pleuritic membrane. 
J. Arnold. 
separately and in bundles, in its walls and in the coats of the 
minute arterioles which nourish it. 
The plain fibre is composed simply of one or more elongated 
9 130 
MANUAL OF HISTOLOGY. 
cells. (Fig. 50.) The nucleus is at about the middle. The cell 
swells out around the nucleus, and quickly contracts again be- 
yond it. A small cell, such as is found in the wall of a small 
blood-vessel, is consequently spindle-shaped, but we find many 
in the frog’s bladder that run out into fine threads of indefinite 
length. Sometimes one end of a cell divides into two fibres. 
(See Figs. 51 and 52.) 
The nucleus sometimes appears to be homogeneous, though 
it usually contains one or more granules, sometimes considered 
to be nucleoli. When using a high power the writer has some- 
times found that the nucleus contained many granules, so ar- 
ranged as to suggest very strongly a transverse striation. A 
row of granules at each end of the nucleus is sometimes found. 
Muscular fibres in the walls of small, transparent blood-vessels 
are very instructive objects, because by changing the focus we 
can observe them as they curve round the vessel, both in longi- 
tudinal and in transverse section. At those places where a 
transverse section of one end of the cell is in focus we see what 
appears to be a granule merely. If another part near the nu- 
cleus is brought into focus, it shows as a small circle, while if 
the nucleus happens to be cut transversely, it gives the effect 
of a dark spot inside a circle. 
VOLUNTARY MUSCULAR FIBRE. 
No tissue is more easily recognized than striped muscular 
fibre, yet none is more difficult to understand.1 
The fibres are cylinders or irregular prisms of varying length. 
Their diameter in the human body varies, according to Frey, 
from .0118 to .0563 mm. Each fibre is tightly inclosed in a struc- 
tureless elastic membrane, called the sarcolemma. This sheath 
is not very easily demonstrated ; but if fresh muscle be roughly 
picked to pieces in water, shreds of it may be seen at the torn 
ends of fibres, and sometimes it can be made out where the 
muscular substance has been injured in the course of a fibre. 
1 Any attempt at an account of the many views that have been and are held, 
would make this article far too long. A few only will he mentioned, and these inci- 
dentally. It is hoped that this defect, if it be one, will be compensated for by the 
fulness of the bibliography. VOLUNTARY MUSCULAR FIBRE. 
The existence of a sarcolemma being admitted, it is clear 
that it must be highly elastic so as to accommodate itself 
to the changes both of length and breadth which the fibre 
undergoes. The phenomena of contraction show, moreover, 
that it must be attached at definite points to the muscular 
substance. 
Fresh muscular fibre of a vertebrate animal, when teased 
out and examined under a moderately high power, presents a 
series of alternate black and white cross stripes, which are 
held to be characteristic of voluntary muscle. (Fig, 53.) This 
appearance is beautifully distinct in some 
fibres, and very vague in others. It may 
vary greatly in different parts of the same 
fibre ; the stripes may run perfectly straight 
across the fibre ; they may present a uni- 
form curve, or they may be interrupted at 
intervals, some parts of the line being in 
advance of others. (See Fig. 53.) 
As a fibre taken from an animal im- 
mediately after death naturally draws it- 
self together (without, however, necessarily 
presenting the phenomena of physiologi- 
cal contraction), it is desirable to ascertain 
whether this modifies the appearances. To 
do this, fibres from a recently killed animal should be ex- 
amined in a state of extension. A cut should be made in the 
body of a muscle, a few fibres teased out and stretched on the 
slide under the covering glass before their attached ends are 
divided. 
Fig. 53.—Striped muscular 
fibre : a, black stripe : 6, in- 
termediate stripe; c, white 
stripe; n, nucleus. After 
Ranvier. 
It will be seen that the light stripe is more affected by the 
stretching than the dark one, though both are broader than in 
the non-extended fibre; but the most important effect is the 
appearance, often seen with high powers, of a very narrow, in- 
terrupted black line in the middle of the light band. 
Beside this cross striation, the fibres of vertebrates show 
more or less plainly minute longitudinal lines. It is to be no- 
ticed that when the cross stripes are very distinct the longitu- 
dinal ones are veiy faint, or even invisible, and that when the 
latter are well marked the former are the reverse of it. Some 
reagents tend to divide a fibre into disks, others into fibril!m. 
Among the former are solutions of acetic acid in water (1 in 132 
MANUAL OF HISTOLOGY. 
100—200), hydrochloric acid (1 in 50—200), and among the latter 
a solution of chromic acid (1 in 200). It is very probable that 
the amount of longitudinal striation varies in different muscles, 
being related, perhaps, to physiological properties, or possibly 
the result of mechanical causes. It is certain that both kinds 
of striation may be found in great perfection in fibres treated 
with almost any reagent that does not destroy them. Some- 
times muscle is seen to be split into fibrillse, each of which 
shows the transverse stripe, though the shreds are so fine that 
each disk is represented by a dot merely.1 This may be de- 
tected very well in the muscle of the lobster after it has been 
picked to pieces in glycerine. 
Returning to the transverse stripes in vertebrates, the striae 
are very near together in the frog, and thus this useful animal 
is not specially desirable. The muscle of the rabbit is much 
better, and human muscle is, perhaps, better still. The muscle 
of the human embryo in the last months of pregnancy is par- 
ticularly good. A very high power will often show the narrow 
black line in the midst of the white band. Sometimes one edge 
of each black stripe will be very sharply marked against the 
glaring white, while the other side will present a less marked 
contrast. If the stage of the microscope admits of rotation,2 in- 
structive effects can also be obtained. As the.field turns round, 
the brightness at the sharp border of the black stripe gradually 
decreases, to return on the other side. Again, this change may 
not occur. Sometimes, when the upper edge of the fibre is pre- 
cisely in focus, the black and white stripes may be made to ap- 
parently exchange places, if the lens is slightly depressed. This 
is probably to be accounted for as follows: First, we may for 
the present assume that the black and white bands are caused 
by disks of different nature. Take a series of such disks and 
imagine them somewhat inclined to one side, like a roll of 
coins on their edges leaning against a support. A vertical line, 
representing the line of vision, that passes through a black disk 
at the upper border of the roll will strike a light one at a 
deeper level. A peculiar effect may be obtained by removing 
the diaphragm and employing very oblique light. The black 
1 The fact that muscle removed from the body can be reduced to fibrillar does not 
prove that these are pre-existing elements. 
2 It is to be regretted that this movement is not more common. VOLUNTARY MUSCULAR FIBRE. 
band then is often replaced by two narrow black lines with a 
light space between them. This is more frequently observed 
when the rays strike the fibre longitudinally. 
The fibres of invertebrates, though on the same plan as 
those of higher animals, are better fitted for study, because the 
elements are farther apart, and because the phenomena of con- 
traction may, in some cases, at least, be observed under the 
microscope. 
The muscles from the thorax and legs of large flies are very 
good. Merkel recommends that they be examined in fresh al- 
bumen from the egg, in which they will continue to contract. 
The fibre is crossed by narrow black stripes which, be it re- 
membered once for all, correspond to the black stripes of ver- 
tebrate muscle. On each side of these stripes there is a bright, 
glittering border, which gradually shades off into a dull band, 
midway between the two stripes. The substance between the 
black stripes is all of one nature, the difference between its 
middle and end portions being an 
optical effect. The dull band corre- 
sponds to the fine line which high 
powers reveal in vertebrate muscle. 
Its greater breadth is due to the 
greater distance of the black strides. 
Fibres from the legs and wings 
of the large water-beetles (Hydro- 
philus and Dytiscus) are admirable 
objects, Schafer s valuable obser- 
vations were made on those of the 
legs. He found the black stripe to 
consist of a double row of highly 
refracting granules, which were the 
ends of dumb-bells embedded in the- 
contractile substance. These struc- 
tures are arranged side by side, the 
adjacent ends of the dumb-bells forming the stripe, while the 
handles constitute the slight longitudinal striations. (See Fig. 
54.) The bright borders are due to the refraction of light from 
the spherical heads of the dumb-bells. It is clear that they 
must cause a greater amount of rays to pass through the sub- 
stance directly beside them than go through the substance 
midway between them, which latter appears dark in conse- 
Pig. 54.—Muscle of large water-beetle 
(Dytiscus) : a, dull band ; b, bright space 
around; c, the highly refractive ends of 
the dumb-bells: cl, the handles of the dumb- 
bells ; 5, sarcolemma. After Schafer. 134 
MANUAL OF HISTOLOGY. 
quence. Some years before Schafer’s theory was advanced 
Heppner had shown that the bright borders of the black stripe 
must be due to the reflection of rays through them from the 
surface of the stripe. The phenomena observed on rotating 
the stage of the microscope are in accordance with this theory. 
There are, no doubt, some apparent exceptions, but these lose 
their weight when we consider how many elements there are 
that complicate the problem. If, for instance, as is often the 
case, the disks do not present their edges quite evenly to 
the eye of the observer, but are somewhat inclined, like the 
roll of coins above mentioned, the conditions are at once 
changed. Again, light thrown up vertically through a small 
diaphragm must produce different effects on the object from 
light striking it very obliquely. 
Some years ago the writer was fortunate enough to discover 
an excellent object for the study of living muscular fibre in the 
detached legs of the Gyrinus. This is a small beetle, known 
in the county as the “ lucky bug,” which describes most ec- 
centric figures on the surface of ponds. A leg should be cut 
off close to the body, and examined in a drop of water under a 
very thin covering glass. The shell is transparent, and as the 
muscles are undisturbed, except in the segment cut in remov- 
ing the leg, they are in a perfectly normal condition, lacking 
only their vascular and nervous supply. They will frequently 
contract for more than an hour, if the covering glass be lightly 
tapped occasionally. The part of the leg known as the tibia, 
which is easily recognized by a large Y-shaped air-tube, has 
the thinnest shell, and is usually the best place for study, 
though occasionally better views are obtained in the two parts 
next above it, in which it is easier to find a single layer of fibres. 
The leg is very apt to flex itself between the femur and tibia, 
thus obscuring one of the best places. If necessary, this can 
be prevented by putting a thin piece of paper against the inner 
side of the leg. The anterior pair of legs, which project for- 
ward, are made on another plan, and are less desirable. A 
very high power is necessary, as, for instance, Hartnack’s 10 
immersion lens. Much practice also is needed to follow the 
steps of contraction, and indeed this can be done only when it 
has become very slow. 
The fibre, when at rest and moderately stretched, appears 
to be a cylinder with straight edges, and composed of a semi- VOLUNTARY MUSCULAR FIBRE. 
fluid, transparent ground-substance. This is crossed by the 
black stripes with shining borders, such as have been described. 
The black stripe usually appears 
granular, and may be divided into 
two parallel rows of granules. Some- 
times the two borders are equally 
bright; sometimes one much out- 
shines the other. Some fibres are 
found which, not being subjected 
to any tension, are much more 
drawn together. The black bands 
are, perhaps, only half so far apart 
as in the case just described. They 
are never divided into two, and 
though some appear granular, 
others are homogeneous. The edges 
of the fibre are no longer straight, 
but slightly scalloped, the centre 
of each projection being midway 
between the black stripes. (See 
Fig. 55.) 
When active contraction takes 
place, the whole fibre is involved, 
and presents nothing but a series 
of transverse black and white bands 
with scalloped edges. To study the 
successive stages of contraction we 
must wait until it is feeble and in- 
volves but a small part of the fibre. 
It runs like a wave from one end of 
the fibre to the other, pauses a mo- 
ment, and then runs back again, 
and sometimes starts anew, but with 
diminished force. It is hard to fol- 
low the steps, for the elements are 
changing their shape and position 
at the same time ; the black stripes 
become broader, less granular, and 
each runs toward its neighbor in 
the direction of the wave ; the gray band disappears, and the 
edge of the fibre bulges. As the elements in front of the 
Pig. 55. Semi-diagrammatio repre- 
sentations of muscular fibres of G-yrinus. 
Fibre supposed to be in situ and showing 
the different appearances which the black 
stripe may present. The wave of contrac- 
tion is travelling toward A. At owe 
notice that a part of the fibre, after con- 
traction, has been subjected to stretching 
after the passage of the wave; at B the 
elements are in a state of active contrac- 
tion. The longitudinal striation made 
unavoidable in the woodcut, does not, as a 
rule, exist in the living fibre. 136 
MANUAL OF HISTOLOGY. 
wave enter into the contracted condition, those behind as- 
sume their normal state at first, but do not retain it, for they 
are immediately subject to a severe stretching by the course 
of the wave, and present new and very instructive appear- 
ances. The fibre becomes much narrower, the black stripes 
are resolved into two rows of granules some 
distance apart. The whole substance of the 
fibre is lighter than in the other conditions, 
and though the bright borders of the stripes 
are still there, they are much less glaring, and 
present less contrast with the intermediate por- 
tion. 
In some of these fibres an indistinct longi- 
tudinal striation is seen, but the writer is not 
satisfied that it is in the substance of the fibre. 
Fig. 56. Trans- 
verse section of frozen 
frog’s muscle show- 
ing Cohnheim’s areas. 
Frey. 
Transverse sections of muscle have been ap- 
pealed to for elucidation of the structure of the 
fibre. Cohnheim showed a network of whitish 
lines surrounding small, dull-colored polygons 
on cross-cuts of frozen muscle (Fig. 56), The muscles of the 
crab are said to show this particularly well. Schafer found 
in the muscles of the water-beetle the appearance of granules 
on a clear ground. A similar appearance is seen in the fibres 
of vertebrates. The writer has observed in the cross-section of 
fibres from the tongue of the mocassin snake, granules which 
presented, at least, the suggestion of bright points in their cen- 
tre. In some fibres these were collected into groups, separated 
by clear spaces. 
Cohnheim’s areas cannot be considered equivalent to fibril- 
Ise, but rather, as Kolliker claims, to bundles of them, sup- 
posing always, we would add, that fibrillse exist at all. It is 
pointed out in the account of the transverse striae that these 
are often interrupted, and there is no doubt that this may be 
due to the limits of the muscle-columns. Of course, we must 
assume that there are many more columns than would be in- 
ferred from these interruptions ; for if the transverse stripes of 
two neighboring columns exactly correspond, no break will 
appear. 
Nuclei and muscle-corpuscles.—ln mammalian muscle acetic 
acid demonstrates a number of oval nuclei which may contain 
one or more nucleoli. Their long axis runs in the same direc- YOLTJJSTTAEY MUSCULAE FIBEE. 
tion as that of the fibre. A small amount of granular matter 
may be seen at their extremities. Cross cuts of fibres show 
that, witli possibly some exceptions, they lie directly beneath 
the sarcolemma. In the frog, and in many invertebrates, as the 
beetles, they lie in the substance of the fibre, and, especially 
in the latter class of animals, are surrounded by a mass of 
granular protoplasm, Weber denies that in the adult frog 
they are surrounded by this mass. 
Conclusions.—From what precedes, it seems demonstrated 
that striped muscular fibre consists of a transparent, semifluid 
ground-substance, which is the contractile element. At certain 
intervals a double layer of minute granules or spherules is 
placed, which practically forms a transverse disk. The refrac- 
tion of the light causes the substance bordering this disk to 
appear brighter than the intermediate portion, which is only 
occasionally seen in mammalian muscle as an indistinct and 
usually a broken line, because the black stripes are so near to- 
gether that the bright borders of two neighboring ones coalesce. 
In invertebrates, as beetles, for instance, they are so far apart 
that the dim stripe is proportionally broad, but it necessarily 
disappears when by contraction the black stripes are brought 
nearer together. Variations in the direction of the light, or 
any obliquity of the disks, will cause peculiar effects, well- 
nigh defying analysis. The writer’s views coincide, in the main, 
with Schafer’s, except that he cannot accept the “handles” of 
the latter’s dumb-bell-shaped structures. As the writer has 
stated in another paper, muscles in the leg of the Gyrinus 
which have been exhausted by electricity show the stripes very 
indistinctly, and contain a number of stray granules. Klein 
has pointed out that if fresh muscular fibre of the frog is 
teased out in salt solution, when a break of the substance oc- 
curs inside the sarcolemma, “ inside this tube a greater or less 
number of granules are observed in active molecular move- 
ment.” These observations appear to confirm the views given 
above. 
A good deal has been written about the effect of polarized 
light on muscular fibre, and very different results have been 
reached. Ranvier thinks it of no value in the discussion, be- 
cause the same substance may be either doubly or singly re- 
fracting, according to the pressure to which it is subjected. 
This is certainly a strong argument against its value, espe- 138 
MANUAL OF HISTOLOGY. 
cially in view of the discrepancy of the observations made 
with it. 
Each fibre is, moreover, divided longitudinally into a vary- 
ing number of what are called muscle-columns, held together 
probably by a delicate cement. Between these are lodged the 
muscle-corpuscles in the lower forms of animals. In opposition 
to most authorities, the writer is inclined to question the exist- 
ence of fibrillm in the living muscle, at all events, as essential 
parts of its structure. The granular appearance of cross sec- 
tions is in accord with the views given above, and does not 
necessarily imply the presence of fibrillse. 
Peculiarities of voluntary muscles of different functions. 
—Ranvier was the first to discover a physiological and struc- 
tural difference in the red and white muscles of the rabbit’s 
leg and in some other animals where both kinds exist. He 
found that the semitendinosus of the rabbit, a red muscle, if 
acted on by an induction current, gradually contracted till it 
became tetanized, and remained so until the current was 
stopped, when it gradually relaxed. White muscles, on the 
other hand, when treated in the same way, contracted sud- 
denly, and continued to give jerks corresponding to the inter- 
ruptions of the current as long as it was continued. With its 
cessation the muscle instantly returned to its original length. 
From this he concludes that the white muscles are those of 
sudden action, while the red ones serve to regulate power and 
to maintain equilibrium. As to structure, he found out that 
the white muscles had a very distinct transverse striation, and 
a very faint longitudinal one, while in the red the longitudinal 
lines were very marked, interrupting the cross ones at many 
points, and giving the fibre a granular appearance. The nu- 
clei were much more numerous in the red fibres, and, instead 
of being flattened and situated just beneath the sarcolerama, as 
in the white, were oval and projected into the fibre, some even 
lying in its interior. 
Ranvier showed later that the vascular supply of the red 
muscles differed from the usual arrangement, which consists 
simply in elongated meshes of capillaries in the main parallel 
with the fibres. In red muscle, not only were the minute ves- 
sels more numerous, but the longitudinal capillaries were more 
varicose, the meshes nearly as broad as long, and the transverse 
vessels, both of the capillaries and small veins, presented fusi- VOLUNTARY MUSCULAR FIBRE. 
form dilatations, the object being, as he points out, to keep the 
muscle supplied with oxygen during its long-continued con- 
traction, which must interrupt the circulation. 
E. Meyer has since shown that Ranvier was over-hasty in 
his generalization. What is true of the semitendinosus of the 
rabbit is not necessarily true of other red muscles. 
The writer is able to confirm this statement. As to the dif- 
ference between the semitendinosus and white muscle, he is in- 
clined to admit the greater number of nuclei of the former, but 
the difference in the stripes did not seem to him conclusive. 
The peculiarity, however, of the minute blood-vessels of the 
semitendinosus is very striking ; but in another red muscle of 
the rabbit’s thigh he did not find the same arrangement. The 
richness of the capillary network varies greatly in different 
muscles of the same animal. Future investigations will, per- 
haps, show that modifications in the arrangement of the minute 
blood-vessels correspond with the 
function of the muscle. 
The termination of muscle in ten- 
don.—This occurs in several ways. 
Sometimes the fibre divides again and 
again, ending in small bundles of 
fibrillse which have lost all muscular 
characteristics. Again, instead of 
spreading out, a fibre may become 
pointed, and the enveloping sarco- 
lemma, reinforced with more or less 
fibrous tissue, runs on as a delicate 
tendon. Both these modes of end- 
ing can be seen in the tongue.1 The 
cases in which a fibre loses its stria- 
tion, and is apparently continued as 
a tendon of about the same size, 
present greater difficulties. By sep- 
arating the fibres of a frog killed 
by immersion in hot water, Kanvier has succeeded in demon- 
strating that the sarcolemma incloses the tendinous end of the 
fibre. The whole subject, however, of the ending of the fibres 
is not exhausted. 
Pig. 57. Anastomosing muscular 
fibre of the heart, seen in a longitudinal 
section. On the right, the limits of the 
separate cells with their nuclei are ex- 
hibited somewhat diagrammacically. 
After Schweigger-Seidel. J. Arnold. 
1 Thin sections of the hardened tongue of a small animal are to be recommended, 
not only for the study of this point, but for that of striped muscle in general. 140 
MANUAL OF HISTOLOGY. 
The muscular fibre of the heart.—This is transitional in 
structure between the voluntary and the involuntary. The 
fibres of the heart of the frog resemble chiefly the latter, being- 
made of elongated, narrow, nucleated cells, which differ from 
it only in being transversely striped. In the mammalia the 
fibres are broader and composed of nucleated cells placed end 
to end. These cells frequently give off lateral processes which 
support others, thus forming a network of fibres. The cells 
have both a longitudinal and a transverse series of stripes, 
but the latter are not so clear as in well-marked voluntary 
muscle. 
BIBLIOGRAPHY. 
Bowman. On the Structure and Movements of Voluntary Muscle. Philosoph. 
Transactions. 1840-41. 
Amici. Ueber die Muskelfaser. Virchow’s Archiv. Bd. XVI. 1859. 
Weismann. Ueber die Muskulatnr des Herzens beim Menschen uud in der Thier- 
reihe. Reichert &Du Bois-Reymond’s Archiv. 1861. 
Ibid. Ueber die Verbindung der Muskelfasern mit ihren Ansatzpunkten. Zeit- 
schrift fur ration. Medicin. 3te Reihe. Bd. XII. 1861. 
Cohnheim. Ueber den feineren Ban der quergestreiften Muskelfaser. Virchow’s 
Archiv. Bd. XXXIV. 1865. 
Dwight. The Structure and Action of Striated Muscular Fibre. Proceedings Bos- 
ton Soc. Nat. Hist. Vol, XVI. 1873. 
Schaefer. On the Minute Structure of the Leg Muscles of the Water-Beetle. 
Philos. Transact. 1873. 
Engelmann. Mikroskopische Untersuchungen liber die quergestreifte Muskelsub- 
stanz. Pfliiger’s Archiv. Bd. VII. 1873. 
Kolliker. Handbuch der Gewebelehre. Leipzig, 1867. 
Hensen. Arbeiten aus dem Kieler physiologischen Institut. 1868. 
Heppner. Ueber ein Bigenthuraliches Verhalten der quergestreiften Muskelfaser. 
Archiv fiir mikroscop. Anat. Bd. V, 1869. 
Doenitz. Beitrage ziir Kenntniss der quergestreiften Muskelfaser. Reichert &Du 
Bois-Reymond’s Archiv. 1871. 
Sciiweiger-Seidel. The Heart. Strieker’s Histology. 1873. 
Merkel. Der quergestreifte Muskel. Archiv fiir mikro. Anatomic. Bd. VIII. 
1872. ' 
Brueckb, E. The Behavior of Muscular Fibres when examined by Polarized Light. 
Strieker’s Histology. 1872. 
Sachs. Die quergestreifte Muskelfaser. Reichert &Du Bois-Reymond’s Archiv. 
1873. 
Wagener. Ueber die quergestreifte Muskelfibrille. Archiv fiir mikro. Anat. Bd. 
IX. 1873. BIBLIOGRAPHY. 
Ibid. Ueber einige Erscheinungen an den Muskeln lebendiger Oorethra plumicornis- 
larven. Archiv.. filr mikro. Anat. Bd. X. 1874. 
Kaupmann. Ueber Contraction der Muskelfaser. Reichert &Du Bois-Reymond’s 
Archiv. 1874. 
Thin. On the Minute Anatomy of Muscle and Tendon. Edinburgh Medical Jour- 
nal. Sept., 1874. 
Weber. Note sur les noyaux des muscles stries chez la grenouille adulte. Archives 
de physiologic. 1874. 
Ranyier. De quelques fait relatifs a I’histologie et ala physiologic des muscles 
stries. Archives de phys. 1874. 
Ibid. Note sur les vaisseaux sanguins et la circulation dans les muscles rouges. 
Archives de phys. 1874. 
Ibid. Traite technique d’histologie. Paris, 1875. 
Fredericq. Generation et structure du tissu musculaire. Bruxelles, 1875. 
Meyer. Ueber rothe und blase quergestreifte Muskeln. Reichert &Du Bois- 
Reymond’s Archiv. 1875. 
Fredericq. Note sur la contraction des muscles stries chez I’hydrophile. Bulletin 
Acad. Roy. de Belgique. Tome XL. 1877. 
Renaut. Note sur les disques accessoires des disques minces dans les muscles 
stries. Compt. rend. Tome LXXXY. No. 21. 1877. 
Biedermann. Zur Lehre vom Bau der quergestreiften Muskelfaser. Wiener Acad. 
Sitzungsbericht. Bd. LXXXY. No. 21. 1877. 
Schaefer. Quain’s Anatomy. Eighth edition. New York: Wm. Wood & Co. 
1878. 
Nasse. Zur microscopischen Untersuchung. des quergestreiften Muskels. Pfliiger’s 
Archiv. Bd. XVII. 1878. 
Froriep. Ueber das Sarcolemm und die Muskelkerne. Archiv filr Anatomic und 
Entwickelungsgeschichte. 1878. 
Engelmann. Nouvelles recherches sur les phenomenes microscopiqne de la con- 
traction musculaire. Archives Neanderlaises des Sciences exactes et natu- 
relles. 1878. 
Flemming. Ueber Formen und Bedeutung der organischen Muskelzellen. Zeit- 
schrift fiir wissenschaftliche Zoologie, XXX. Supplement. 1878. 
Unger. Untersuchungen iiber die quergestreiften Muskelfasem des lebenden Thiers. 
Wiener medinische Jab rbiicher. 1879. (Largely pathological.) 
Newman. New Theory of Contraction of Striated Muscle, and Demonstration of 
the Composition of the Broad Dark Bands. Journal of Anatomy and Physi- 
ology. Vol. XIII. 1879. 
Chittenden. Histochemische Untersuchungen iiber das Sarcolemm und einige 
verwandten Membranen. Untersuchungen aus der Physiol. Institut der Uni- 
versitiit Heidelberg. Bd. 111. 1879. 
Klein and Smith. Atlas of Histology. Part V. 1879-80. 
Ranyier. Lemons d’anatomic generate sur le systeme musculaire. Paris, 1880. 
Von Thanhoffer. Beitr. z. Hist. d. quergestreift. Muskels u. d. Nervenendigun- 
gen in demselben. Biol. Centralbl. I. 349-351. 1881. CHAPTER XL 
THE BLOOD-VESSELS. 
Bt EDMUND C. WENDT, M.D., 
Curator of the St. Luke’s and St. Francis’ Hospitals, etc., New York City. 
In man, a closed circuit of branching tubes, which proceed 
from a central organ, the heart, and, ramifying throughout the 
body, return the blood to this central organ, constitutes the 
blood-vascular system, as it has been named. 
Of these vessels we recognize three different kinds : arteries, 
capillaries, and veins. The arteries convey the blood to the 
various capillary districts, whence it is again collected and car- 
ried back to the heart by the veins. 
The arteries, highly elastic throughout, are composed of 
three superimposed layers or tunics. The veins, less elastic, 
and consequently more flaccid and compressible, likewise con- 
sist of three coats or tunics. In both sets of vessels these 
coats have received the names of intima for the inner, media 
for the middle, and adventitia for the external layer. The 
capillaries, intervening between the two, form minute branch- 
ing tubules, which generally have but a single exceedingly 
thin and permeable membrane as the sole constituent of their 
walls. 
Of course, all these vessels merge into one another, so that 
a sharp line of demarcation can nowhere be drawn ; but in 
their typical forms they present clearly defined structural dif- 
ferences, necessitating a separate description of them. We 
begin with the simplest and yet most important class ; 
The capillary blood-vessels.—They are composed, as we 
have already said, of a single layer of cells, arranged in tubu- 
lar form, and containing nuclei. These corpuscles are di- 
rectly continuous, on the one hand, with the inner coat of THE BLOOD-YESSELS. 
the terminal arteries, and, on the other, with the intima of the 
veins, hence also with the lining membrane of the heart. They 
are called endothelia, and since they constitute the only struc- 
tural elements which enter into the composition of all blood- 
vessels, we will first consider them and their relations to these 
vessels. ' 
The vascular endothelium.—Histologists understand by 
the term endothelium a thin layer of flattened cells lining the 
free surface of various membranes, canals, sheaths, and cavi- 
ties, all belonging to the serous type. Epithelium, on the 
other hand, is found covering the skin and mucous surfaces. 
All endothelia, in common with the blood, the blood-vessels, 
'and connective tissues, are derived from the mesoblast, or mid- 
dle of the three fundamental layers of the embryo. The epi- 
thelia, it will be remembered, originate in the two other layers, 
called epiblast and hypoblast, respectively—the former being 
the superior and the latter the inferior layer of the embryo. 
In adult human subjects the vascular endothelia are made 
up of thin, polygonal, sometimes irregularly pentagonal, flat- 
tened cell-plates. Most of the elements are furnished with a 
rounded or ovoid nucleus, of central or more or less peripheral 
location (Fig. 58). Some have two nuclei. In general, the cells 
are somewhat elongated in the longitudinal direction of the ves- 
sel to which they belong. They also grow slightly narrower as 
the calibre of the vessel decreases. Their borders are serrated 
or scalloped, and dove-tailed into one another. An albuminoid 
substance, ordinarily invisible, cements their adjoining edges. 
This substance has the peculiar property of effecting an ener- 
getic reduction of silver nitrate. Hence, by proper manage- 
ment, the outlines of each individual cell may be made visible 
as a black zigzag surrounding a nucleus. Every cell represents 
a plate-like expanse of modified protoplasm. Remnants of this 
original substance may be seen to surround the nuclei of young 
vessels, where they appear in the shape of varying quantities 
of distinctly granular matter. Klein has described an intra- 
cellular network, formed by plexuses of minute fibrils, and 
associated with a second denser reticulum within the nucleus, 
called the intranuclear network. Whatever interpretation we 
choose to give these minute structures, the fact of their exist- 
ence is indisputable. In man, however, their presence is not 
as readily demonstrable as in animals. 144 
MANUAL OF HISTOLOGY. 
An isolated endothelial cell, when tilted up on its edge, pre- 
sents the appearance of a straight or curved double contour, 
with a central thickening corresponding to its nucleus. Viewed 
en face, we observe the sinuous outline and the central or ec- 
centric nucleus, with its surrounding granules of protoplasm. 
The shape and contour of endothelial cells are subject to con- 
Fig. 58.—Endothelium of the carotid artery of man, after treatment with nitrate of silver: a, cells; 
b, clearer, c, darker intermediate spaces; d, intra-cellular circular and spotted markings. Bberth. 
siderable variations in the different vascular districts. Such 
differences also occur in the same district, with the varying de- 
gree of expansion or contraction of the particular vessel under 
observation. 
The capillaries proper.—In point of wideness of distribu- 
tion, this variety of blood-vessels greatly exceeds all others. 
Indeed, the capillaries occupy a rank, in this respect, second 
only to the connective-tissue group of histological struc- 
tures. As regards importance to the economy, it will only be 
necessary to advert to the vital processes of nutrition, secre- 
tion, respiration, and excretion, to recall the quality and 
extent of their physiological usefulness. Throughout the THE BLOOD-YESSELS. 
body 1 capillary plexuses are interposed between arteries and 
veins, wliicli constitute a series of conveying and returning 
tubes. Thereby the direct continuity of these blood-channels 
is established. 
It is in these intermediate territories, and in them only, that 
the blood serves its true function of giving and taking. True 
markets of exchange, then, these capillary districts, where the 
system is supplied with new material, and in 
return gets rid of useless or even deleterious 
by-products of tissue-life. Hence, the para- 
mount importance of these vessels in the 
maintenance of life and health. Hence, also, 
the direct practical utility of knowing their 
minute and physiological dignity. 
Every practitioner of medicine will see the 
important relation this branch of histology 
holds to pathology, and therefore to thera- 
peutics. At the same time we should not 
forget that the role played by the capillaries 
in the system is normalty due to the inherent 
mechanical and physical properties of a fine- 
ly elastic animal membrane, rather than to 
any specific action of their cellular constitu- 
ents. 
Robin, following Henle’s example, dis- 
tinguishes several varieties of these vessels. It 
seems to me proper to limit the term capil- 
laries to those minute tubules which are 
entirely devoid of muscular elements. This 
corresponds to the classification adopted by 
Virchow, Kdlliker, Eberth, Ranvier, Frey, 
and others. It is the one therefore that has 
generally been accepted, and is both simple 
and logical. 
Pig. 59.—A rather large 
capillary from the hyaloid 
of the frog, presenting a 
membranous and nucleated 
tunica adventitia. Eberth. 
The diameter of these tubules varies from 
0.0045 to 0.0115 mm. Their structure is readily understood. 
Examined in the living animal with a high power, we see mere- 
ly a delicate, hyaline, double-contoured membrane, having an 
1 Hoyer has shown that a direct communication of arterioles with venules occurs 
normally in the tips of the fingers, the matrix of the nails, the tip of the nose, and 
various other parts. 146 
MANUAL OF HISTOLOGY. 
average thickness of 1 to 2 micro-millimetres (0.001—0.C02 
mm.). This membrane forms a tubule, the parietes of which 
are studded at intervals with rounded or oval nuclei, often 
containing one or more bright nucleoli. When oval, these nu- 
clei have their long axis parallel with the direction of the ves- 
sel. Their average size is 0.0056 to 0.0074 mm. They possess 
the property of eagerly imbibing most of the staining fluids 
employed in histology, and of resisting the action of dilute 
acids, alkalies, and other reagents. (See Fig, 50.) 
Besides nuclei, the capillary wall contains at various points 
peculiar granules, which indicate its protoplasmic nature. In 
addition, Strieker and Eberth have described lateral processes 
and pointed prolongations jutting out from the parietes of the 
Fia. 60.—Capillaries of the lungs of the frog, with irregularly dentated cells: a, vascular meshes 
Eberth. 
capillary tubes. In growing tissue these are readily demonstra- 
ble, often forming thread-like connecting bridges between neigh- 
boring vessels ; at a later period they are hollowed out into 
true capillaries. The shorter sprouts are also protoplasmic 
buds, capable of further development into similar vessels. (See 
Fig. 61.) By employing weak solutions of silver nitrate, the 
capillary-wall may be shown to consist of variously shaped 
areas, each one corresponding to a nucleated cell. They are 
the endothelia, and represent, as already stated, the sole essen- 
tial constituents of all capillaries. Their form varies with the 
calibre of the vessel, the smaller capillaries being composed of THE BLOOD-VESSELS. 
corpuscles wliicli are comparatively narrow, tire larger vessels 
having broader cells. In man they have an average length of 
0.0756—0.0977 mm., and an average breadth of 0,01—0.05 mm. 
The intercellular boundaries, brought out as dark lines by 
means of the silver salt, frequently exhibit little nodular swell- 
ings. (See Fig. 58.) 
In addition to the ordinary endotheha, we hnd smaller 
areas, generally without nuclei; they have rounded or some- 
what dentate contours, 
and are interposed be- 
tween the other cells. 
Eberth believes that 
some of these intercal- 
ated areas, as Auerbach 
has called them, proba- 
bly correspond to por- 
tions of strangulated vas- 
cular cells. It is more 
logical to regard them as 
the remnants of an in- 
complete endothelial des- 
quamation, a process 
which is of physiologi- 
cal occurrence through- 
out the blood-vessels. 
These remaining bits are 
finally destined to be- 
come quite detached 
from the vascular wall, and are then swept away by the rush 
and flow of the blood-current. The detached portions of such 
endothelia and their nuclei appear as free granules in the blood, 
where they have puzzled many observers, and have been vari- 
ously called microcytes, hcematoblasts, etc. From this descrip- 
tion it is plain that Cohnheim’s view, that these spaces are 
openings or stomata, is not sustained. True, we find in serous 
membranes of certain animals real openings, but these always 
appear of rounded shape, and are, to say the least, not com- 
monly observed in human blood-vessels. This statement of 1 
the case does not militate against Cohnheim’s well-known 
views that the corpuscles emigrate through the vessels, for, 
remembering the protoplasmic nature of the endothelial tubes, 
Fig. 61.—A, A, stellate connective-tissue cells connected by 
8,8, delicate protoplasmic threads to 0,0, sprouts of endothe- 
lial tubes ; D, protoplasm connecting two capillaries ; B, nu- 
cleus imbedded in a primitive sprout of protoplasm, budding 
from wall of capillary. Specimen prepared by silver nitrate. 148 
MANUAL OP HISTOLOGY. 
we can readily account for the phenomena in question. The 
capillary-wall is elastic, extremely thin, and permeable. By 
virtue of these qualities, it may allow the passage of a leu- 
cocyte or colored globule through its substance without suf- 
fering a permanent breach of continuity. 
The writer’s views on endothelial desquamation as a normal process of physi- 
ological import may strike the reader as insufficiently substantiated by known 
facts. But when we remember that similar processes have been actually ob- 
served taking place under the microscope, all doubts as to the probability of 
this endothelial desquamation should vanish. The author refers to the recent 
observations of Altmann {Arch. f. miJcros. Anat., Yol. XYL, p. 111). This his- 
tologist investigated the changes which take place in the serous epithelium 
[i.e., endothelium) of the exposed frog’s mesentery. Multiple swellings of the 
endothelia were seen to occur; then portions of these cells would become de- 
tached. Such detached bits were found to resemble in their appearance ordi- 
nary leucocytes. But, in spite of this apparent breaking up of the endo- 
thelia into these nucleated corpuscles, they often retained their individuality 
unaltered. The production of bodies resembling leucocytes from endothelia 
has, therefore, been actually observed in connection with serous membranes, 
and vascular desquamation is essentially the same process. 
The capillary blood-vessels occupy the interstitial connec- 
tive tissue of organs, without entering their parenchyma proper. 
Cartilage, the teeth, the hairs and nails, the cornea, and cer- 
tain structures of the nervous system and organs of special 
sense are devoid of capillary supply. 
Most of the larger tubes are invested by a delicate, exter- 
nal, sheath-like structure, called the capillary adventitia or 
vascular perithelium. It is composed of a rather close net- 
work of delicate connective-tissue fibrils. Prolongations of pe- 
culiar stellate cells, which clasp the capillary-tube, may some- 
times be seen to join these fibrils. (Fig- 62.) Such branching 
cells are also encountered at some distance from the capillaries. 
They show delicate processes, which may anastomose with the 
offshoots of the adventitial corpuscles. In other places we 
only find external plates of connective-tissue cells (Krause's ino- 
hlasts), which have become more or less fused with the capil- 
lary-wall. In many instances the perithelium is inseparable 
from the connective-tissue stroma surrounding the vessel. 
In reference to the manner of anastomosis, the forms and 
modes of ramification of different networks vary with the dif - 
ferent tissues and organs of the body. Hence, a simple in- THE BLOOD-VESSELS. 
spection of capillary reticula will generally enable us to decide 
the nature of the tissue or organ in question. From a physio- 
logical point of view, we recognize a causal relation between 
high capillary development and great functional activity. 
Therefore, the abundance of capillaries will determine the 
physiological importance of an organ. 
The chief forms of ramification may be grouped as follows : 
1. Loops (a), simple or compound; e.g., the skin and the hard 
Fig. 62.—Capillaries from the hyaloid membrane of the frog: a, a, capillary-wall; b,b, nuclei of the 
same ; c,c, cells of the tunica adventitia; d,d, processes of these cells clasping the capHlary-wall; e, stel- 
late cell anastomosing with the cells of the tunica adventitia. Eberth. 
palate ; (b) reticulated (the intestinal villi). 2. Tufts (the kid- 
ney), 8. Irregularly polygonal networks (the glands and the 
mucous membranes). 4. Rounded reticula, with round or 
polygonal meshes (adipose tissue). 5. Reticula witheiongated 
meshes (the muscles, bones, and tendons). There would be a 
certain satisfaction in knowing that this or that vessel had a 
precise breadth, and its coat a certain thickness. The precision 
would be apparent, however, rather than real, because such 150 
MANUAL ON HISTOLOGY. 
measurements vary greatly at different times in the same ani- 
mal, and even more so in different animals. It may be stated, 
in general, that the calibre corresponds to the size of the largest 
blood-globules. In man, therefore, we have an average diam- 
eter of about 0.007 mm. The largest capillaries exist in the 
mucous membrane of the stomach and colon, the periosteum 
and bones, and the pituitary body. The smallest are found in 
the skin, the small intestine, the lungs, the muscles, the gray 
substance of the brain, and the retina (Valentin, Weber, and 
Henle). 
The genesis, reproduction, and regeneration of capillaries. 
—There is still much uncertainty about the mode in which 
blood-vessels are first formed in the embryo. My personal 
Fig. 63.—Growth anil development of capillaries hy nucleated sprouts of protoplasm: A, poly-nucle- 
ated large sprout with filiform process ; 8,8, blood-globules; C, branched cell; D, delicate protoplasmic 
tendril linking C with E, a smaller mono-nucleated sprout of endothelial wall. 
observations on this subject, while working recently under the 
supervision of Kolliker, appear to confirm the view held by 
Foster and Balfour. These authors’ account of the interesting 
process may be summed up as follows : About the second day 
of incubation in the chick, certain mesoblastic cells send out 
solid processes, which, uniting, form a protoplasmic network 
containing nuclei. A majority of the latter acquire a reddish 
tint, and are ultimately transformed into colored blood-glob- 
ules. Other nuclei, however, remain unaltered, and, receiving 
an investment of protoplasm, form walls inclosing the reddened THE BLOOD-VESSELS. 
nuclei. The protoplasm of these central nuclei rapidly becomes 
liquefied, thus forming the blood-plasma. And now we have a 
system of communicating tubules, containing corpuscles float- 
ing in a plasma, their walls consisting of nucleated cells. 
Hence, the blood-vessels do not arise as intercellular spaces, 
but are hollowed out to form channels in an originally solid 
reticulum of protoplasm derived from mesoblastic cells. 
This explanation of the way in which vessels are formed 
aids us in understanding both how capillaries are reproduced 
in the adult, and their regeneration under pathological condi- 
tions. The capillary-wall itself, under the influence of favor- 
ing circumstances, begins to bud, as it were ; the delicate proto- 
plasmic sprouts send out more delicate filaments, which, uniting 
with similar offshoots from neighboring vessels, establish a 
connection between two capillaries. In due time these solid 
structures undergo the familiar process of hollowing out, and 
the newly formed vessel is complete. Frequently the proto 
plasmic threads communicate, forming a reticulum which Ran 
vier has called vasoformative network. This author also ob 
served that capillaries develop from special cells, termed 
vasoformative cells. They resemble leucocytes, and form by 
their prolongations a network of solid protoplasm. This is 
originally quite independent of already existing capillaries. 
Subsequently, however, a consolidation is effected, and the 
blood then flows through these new channels in the usual 
manner. 
The author has been able to trace collections of emigrated 
leucocytes through various stages of progressive development, 
culminating in the formation of true capillaries. The experi- 
mental investigations on this subject were carried out in Pro- 
fessor v. Rindfleisch’s laboratory, and have been fully described 
by his former assistant, Prof. Ziegler, of Berne, 
The arteries.—lf we follow the capillaries in a direction 
toward the heart, we soon find the endothelial tube receiving 
an investment of unstriped muscle-cells. These are wound 
transversely or obliquely around the capillary, thus forming a 
second tube, as it were, surrounding the first. External to the 
muscular layer there appears some connective tissue, mingling 
with which elastic elements may be observed. The direction 
of these additional fibres is mainly longitudinal. They form 
the third or external coat, called the adventitia, the second or 152 
MANUAL OF HISTOLOGY. 
middle being represented by the muscle-cells, and the first or 
internal by the endothelial tube. The latter now receives the 
name of intima. When the layers of its walls are arranged in 
this simple manner the vessel is called an arteriole, and this 
constitutes the type of all arteries. 
Arterioles, however, commonly contain a few additional 
fibres between the intima and the media, as the first indication 
of what afterward becomes a special layer. This structure, 
known as the internal elastic coat, attains considerable devel- 
opment in the larger vessels. With the growth of an artery in 
calibre its individual coats are reinforced by additional layers. 
Hence the thickness of the entire wall increases at the same 
Pig. 64. Pig. 65. Fig. 66. 
Pig. 64.—Minute artery showing optical section of alternate groups of muscle-cells, and an external nu- 
cleated membrane, representing the tunica adventitia. 
Pig. 65,—A, intima; B, delicate internal elastic coat; E, media (as in Fig. 64); D, adventitia. Arteriole, 
from a child’s mesentery. 
Fig. 66.—Elastic internal tunic of the basilar arteries. Bberth. 
time that its structure is rendered more complex. But new 
tissues never appear. Moreover, the increased thickness is not 
uniformly proportionate to the enlarged calibre ; neither does it 
take place by equal participation of the different tissues men- 
tioned. In vessels of small and medium size there is a prepon- 
derance of muscular over elastic elements. In the larger trunks 
the reverse condition obtains. It is, therefore, proper to dis- 
tinguish arteries of the muscular from those of an elastic type. 
The latter class is represented by the principal distributing 
trunks, all the remaining arteries belonging to the muscular 
type. There exist, however, no abrupt lines of demarcation 
between these main forms—the one merging gradually into the 
other. 
The interposition of the internal elastic coat between the THE BLOOD-VESSELS. 
intima and the media marks the transition of a minute into a 
small artery. This new layer consists at first of delicate fibrils 
of elastic tissue, or an apparently homogeneous membrane. 
Vascular contraction throws it into folds, which appear as 
longitudinal strise or a transverse series of continuous festoons. 
As the vessel grows larger this coat gets thicker, becomes dis 
tinctly fenestrated, and presents a reticulat- 
ed appearance. It is now made up of inter- 
lacing bundles of connective tissue and elas- 
tic fibres, with spaces left between them. 
The latter constitute the fenestrse of this 
layer, which in the large vessels becomes a 
double or triple lamellated membrane. Be- 
tween it and the lining endothelium there 
appears still another structure, which has re- 
ceived various names from different authors. 
Thus, Kblliker has called it the striated in- 
ternal coat; Remak, the innermost longi- 
tudinal fibrous coat; and Eberth, the in- 
ternal fibrous coat. We shall employ the 
last term. The internal fibrous coat consists 
at birth of a granular substance, which be- 
comes distinctly fibrillated in the adult. 
Embedded in this membrane lie numerous 
branching corpuscles, containing large, con- 
spicuous nuclei. Besides these cells, smaller, 
so-called granulation-bodies are frequently 
seen. So far from regarding them as of path- 
ological origin (Eberth, in “Strieker’s His- 
tology”), I prefer to consider them as ma- 
trix-cells for the regeneration of desquamated 
endothelia. My reasons for so doing are 
as follows: In the blood-vessels of young 
animals and newly born infants I have fre- 
quently noticed thick, dark, and granular bodies immediately 
below the endothelial lining. These subendothelial cell-plates 
were smaller and more polyhedral than ordinary endothelia, 
and invariably contained one or even two nuclei. They ap- 
peared to resemble germinating endothelial cells, such as Klein 
has described as occurring in serous membranes. They did 
not, however, occur in single layers, as Klein has seen them, 
Pig. 67. Small artery 
from the brain of man : a, 
tunica adventitia ; a', a\ nu- 
clei of the tunica adventitia; 
6, muscle nucleus; c, elastic 
internal tunic; d, membrane 
formed of fusiform cells. 
Eberth. 154 
MANUAL OF HISTOLOGY. 
but in strata. They were observed in particular vessels of 
young animals. It seems likely that these cells disappear or 
shrivel with the growth of the individual, but their sudden reap- 
pearance in pathological processes leads the author to believe 
that at least some of them persist through life. Talma (Vir- 
chow's Arch., Yol. LXXYIL, pp. 242-269) observed similar 
elements, but thinks they are derived from the ordinary en- 
dothelia, instead of vice versa. He is also convinced that the 
latter are merely modified leucocytes ; but this view has been 
shown to be erroneous by Virchow (Archiv f. path. Anat., 
Yol. LXXYIL, pp. 380-883). Endothelial desquamation is 
probably, as already stated, a physiological process of constant 
PIG. 68.—Transverse section through small artery ami vein : A, artery; a. intima with bulging en- 
dothelial cells, the vessel being drawn in a state of contraction ; b, internal elastic coat, wavy for same 
reason; c, media; cl, adventitia. B, vein, same denominations. 
occurrence, and in some respects analogous to the epithelial 
shedding from the surface of the skin and mucous membranes. 
The media,musculosa, or middle coat, consists of superim- 
posed layers of smooth muscle-elements disposed in groups. 
Most of them lie transversely to the course of the vessel. The 
intervals between neighboring groups are occupied by connec- 
tive tissue and elastic fibres, arranged in networks. This inter- 
stitial substance becomes augmented with the increasing calibre 
of the artery. In the largest trunks it all but replaces the 
muscle-cells. Here, however, the elastic fibres also reach their 
maximum development, encroaching upon the connective-tissue 
elements until the latter become quite inconspicuous. Besides 
its principal transverse layer, the media also contains fusiform 
muscle-cells, placed in an oblique or longitudinal direction. THE BLOOD-YESSELS. 
They are scattered irregularly throughout the middle coat. 
Sometimes the intima and the adventitia also contain sparsely 
distributed muscle-cells. The arterial muscular coat is dis- 
tinctly separated from the intima by the interposition of the 
internal elastic coat. Externally a sharp boundary is formed 
either by the adventitia or by the external elastic coat. The 
latter appears as a separate membrane in arteries of small and 
medium size. There are, however, exceptions to this rule. The 
external elastic coat consists of a close network of delicate 
Fig. 69.—Longitudinal section of pulmonary artery. Mounted in glycerine and acetic acid after de- 
siccation of the artery. «, Internal portion of intima; ft, external portion of intima; c, internal elastic 
coat; d, media, showing cross sections of muscle fibres and elastic tissue ; e, adventitia. 
elastic fibrils, anastomosing with similar adventitial reticula. 
The adventitia is composed of interlacing bundles of connec- 
tive tissue, commingled with elastic lamellm of varying thick- 
ness. 
The veins.—From their origin in the capillaries to the point 
where they enter the trunk proper, the veins preserve through- 
out a uniform type of structure. But no sooner have they 
penetrated into the visceral cavities of the body than we find 
them undergoing considerable alterations, which may either 
increase or diminish the complexity of their structure (Ran- 
vier). The veins are far more numerous than the arteries. 
They are also, as a rule, wider and more dilatable, and have 
thinner coats. It is owing to the latter peculiarity that the 156 
MANUAL OF HISTOLOGY. 
color of the blood is seen through their semitranslucent walls. 
Finally, they branch more frequently than the arteries. Three 
main coats or tunics enter into the composition of most veins. 
These resemble the corre- 
sponding arterial struc- 
tures, and have likewise 
received the names of in- 
tima, for the internal endo- 
thelial lining ; media, for 
the middle muscular ; and 
admntitia, for the external 
connective-tissue coat. 
Veins, however, differ 
from arteries in the feebler 
development of their mus- 
cular coat, in the compara- 
tive paucity of elastic ele- 
ments, a greater laxity 
of their intima, and the 
presence in some of valves. 
We may distinguish veins of smaller calibre, or venules, 
from the vessels of medium and large size. The venules, like 
the arterioles, in certain respects resemble the capillaries. As 
Fig. 70.—Portion of innominate vein of dog, after in- 
jection of a solution of silver nitrate. The endothelial 
cells and their nuclei are visible. The media shines 
through this layer. 
Pig. 71.—Arteriole and venule from child’s mesentery, treatment by acetic acid and glycerine: A, ar 
tery ; a. nucleus of muscle-cell of media ; 6, same in transverse section (optical). B, vein ; c, nucleus of 
connective tissue constituting media, which in these minute veins contains no muscle-cells; d, nucleated 
connective tissue. 
it may become important to differentiate the minuter forms 
of vessels, we will here briefly indicate the main points of dis- 
tinction between full-sized capillaries, small veins, and arte- THE BLOOD-YESSELS. 
rioles. In the latter, the endothelial cells are more nearly 
fusiform, longer, and somewhat narrower than in the venules. 
In tiie capillaries, their form and dimensions hold an interme- 
diate position between the arterial and venous types. The 
middle coat is entirely wanting in capillaries, and is much less 
conspicuous in the small veins than in the arterioles. In fact, 
under ordinary circumstances, the muscle-coat forms by far the 
most characteristic distinguishing feature between these ves- 
sels. Venules quite frequently have only a few sparsely scat- 
tered muscle-cells, in place of the continuous muscular layer 
which exists in minute 
arteries. The former 
also are either altoge- 
ther deficient in the in- 
ternal elastic coat, or the 
presence of this struc- 
ture is barely indicat- 
ed by delicate elastic 
fibres ; these latter usu- 
ally have a longitudinal 
direction. On the other 
hand, arteries of corre- 
sponding calibre are 
mostly furnished with 
a distinct elastic inner 
coat. Finally, with re- 
gard to the adventitia, 
we find it more highly 
developed proportionally in venous than in arterial vessels, 
whereas capillaries commonly have only a few faint fibres to 
denote the presence, in them also, of this coat. 
The internal elastic coat of the larger and largest veins is 
very feebly developed in comparison with that of the arteries. 
Distinct fenestrated membranes are scarcely evefi encountered. 
Veins are likewise possessed of an internal fibrous layer, but 
here again we observe that comparatively feeble development 
of a coat which in the arteries is quite conspicuous. 
Among the many special characteristics of the various 
veins in different regions, we will only mention the following : 
the jugular veins show well-marked elastic reticula, the meshes 
of which contain sparse muscular elements. In the femoral, 
Fig. 72,—Longitudinal section of popliteal vein: a, intima; 
&, media ; c, adventitia. 158 
MANUAL OF HISTOLOGY. 
brachial, and subcutaneous branches there is a media of con- 
siderable dimensions. The inferior vena cava has, in addition 
to a transverse layer of muscle-cells, a longitudinal one of 
greater thickness, and, besides these, contains muscle-cells, 
which are scattered through its elastic coat. The veins of the 
meninges of the encephalon and cord, the retina, the bones, 
and the muscles, and the jugular, the subclavian, the innomi- 
nate, and the thoracic portion of the vena cava are all entirely 
devoid of a true muscular coat. The veins of the gravid ute- 
rus have only longitudinal muscle-elements. In addition to an 
outer longitudinal layer, the vena cava, the azygos, the renal, 
the hepatic, the internal spermatic, and the axillary veins pos- 
sess an inner circular layer. The iliac, the femoral, the popli- 
teal, and several other veins contain a middle coat of transverse 
muscle-cells, between internal and external longitudinal layers. 
The valves of the veins consist of longitudinal bundles of 
connective tissue commingled with scanty elastic fibrils, and 
containing nucleated cells. The inner endothelial layer appears 
to be a direct continuation of the intima of the vein. That 
portion of the subendothelial tissue which does not face the 
blood-current is less developed than the part turned toward it; 
the elastic fibres of the latter are also barely visible. The at- 
tached valvular border frequently presents transversely dis- 
posed muscle-elements. Eberth has denied their occurrence, 
but they have been repeatedly observed by Ranvier and other 
competent histologists. 
Peculiar vascular structures.—The following structures are 
remarkable for the conspicuous and characteristic development 
of their blood-vessels, the vascular membranes, tunicce vascu- 
loses, such as the pia mater of the brain and spinal cord, and 
the choroid coat of the eye. In these we find that the excessive 
vascularity is intended to nourish, not the membranes them- 
selves, but the organs which they invest. 
Blood-vascular glands, vascular plexuses.—ln man, two 
bodies of peculiar structure represent this group. They are 
the coccygeal gland of Luschka, and a rudimentary organ 
called the intercarotid gland. Both consist essentially of con- 
voluted blood-vessels and nerves, imbedded in a nucleated con- 
nective-tissue stroma. The coccygeal gland is a small, rounded, 
pinkish body, of rather firm consistence, and is connected by a 
pedicle with the middle sacral artery. This pedicle contains THE BLOOD-VESSELS. 
blood-vessels and nerves. The arteries entering the gland-like 
body become convoluted, and show numerous tubular, fusi- 
form, or ampullar dilatations. Sometimes they have terminal 
sacculi, closely resembling minute aneurisms, and giving the 
organ its glandular appearance. Indeed, Luschka has called! 
them gland-tubules and vesicles. After death they are com-1 
Fio. 78.—Section of a naturally injected coccygeal gland: a, vessels; B, collection of cells. Ebertn. 
monly found to be empty, but by proper management a good 
natural injection with blood may be readily obtained. Both 
capillaries and veins also present lateral varicosities, studding 
them in great number. All these vessels have the usual endo- 
thelial lining. External to this there appear aggregations of 
rounded or polygonal cells. They are furnished with nuclei, 
and receive an investment corresponding to the vascular ad- 160 
MANUAL OF HISTOLOGY. 
ventitia, but containing comparatively more nuclei than that 
structure. 
The intercarotid gland differs from the coccygeal In its 
larger size, and because it contains accumulations of ganglionic 
nerve-cells. These are derived from the carotid plexus. Here 
the vascular sacculi also more nearly resemble dilated capilla- 
ries, whereas in the other body they approach the arterial type. 
In all other respects the structure of these vascular plexuses 
is identical. Some authors regard the spleen and the supra- 
renal capsule as belonging to this group of blood-vascular 
glands. The author sees no necessity for so considering them, 
and the subject may 
therefore be dis- 
missed without fur- 
ther comment. 
Corpora caverno- 
sa.—They consist in 
great part of dilated 
blood-vessels, chief- 
ly of the venous 
type. These inter- 
communicate very 
freely, and when 
filled with blood 
cause the organ to 
assume the peculiar 
condition known as 
Fig. 74.—A, cellular vascular sheath, from the coccygeal plexus; 
«, connective tissue with scattered cells and nuclei; 6, round and 
polygonal cells lying immediately upon the capillary wall, c; B, a 
capillary from the coccygeal plexus, with a vascular sheath very rich 
in cells. Beferences as in A. Eberth. 
erection. The penis and the clitoris are supplied with caver- 
nous bodies. The urethra of the female and the vestibule also 
contain them. Interlacing bundles of muscle-fibres, together 
with similar bands of connective tissue, form a framework for 
the support of the vascular structures mentioned. The latter 
present the ordinary endothelial lining. 
Several years ago Dr. 11. J. Bigelow succeeded in demon- 
strating the existence of cavernous tissue in the nasal fossae. 
In a letter to the author, Dr. Bigelow states that his point 
was “ the demonstration of an abundant and true cavernous 
structure and erectile tissue on and about the turbinated bones, 
occupying the place of what had been previously supposed to 
be only venous sinuses, the loops of Kohlrausch. The new re- 
sult obtained was due to a different mode of preparation. Kohl- BIBLIOGRAPHY. 
rausch injected from the jugular vein ; I [Dr. Bigelow] inflated 
the tissue locally, as if it were in the penis.” 
rVasa vasorum, lymphatics, and nerves.—Nutrient ves- 
sels are found in the walls of all the larger arteries and veins, 
where they occupy the adventitia. Sometimes they are seen 
to dip down into the outermost portions of the media. Lym- 
phatics occur as clefts or spaces between the various tissues of 
all arterial and venous trunks. Some vessels are ensheathed 
by a lymphatic membrane, which is sometimes furnished with 
a lining endothelium. Such structures are called perivascular, 
or, better, circumvascular spaces. They may be found in 
connection with the omental and the mesenteric vessels, also 
the splenic and the hepatic arteries, as well as certain menin- 
geal vessels of the brain and cord. 
Nerve-fibres are seen to pass to many of the blood-vessels. 
They enter the adventitia, and at its internal boundary sud- 
denly appear to divide into numerous filaments, the ultimate 
distribution of which has not hitherto been satisfactorily ascer- 
tained. They seem to terminate in the muscle-cells of the 
media. Beale considers the presence of ganglion-cells in the 
vascular nerves as of constant occurrence. The author cannot 
admit the truth of this general statement, having discovered 
such cells in only exceptional instances. There is no discerni- 
ble difference of structure between the vaso-constrictor and the 
vaso-dilator nerve-fibres. 
BIBLIOGRAPHY. 
In addition to the well-known standard treatises by Bichat, Kolliker, Henle, 
Sappey, Krause, Frey, Leydig, Teichmann, Strieker, Klein, Ranvier, Bonders, Yier- 
ordt, Luschka, Pouchet et Tourneux, the following may be consulted: 
Ludwig. De arteriarum tunicis. Lipsiae, 1739. 
Rauschel. De arteriarum et venarum structura. Yratisl., 1836. 
Robin. Sur la structure des arteres. Compt. rend. 1847. 
Schultze. De art. struct. Gryph., 1850. 
Remak. Hist. Bemerk. ueber d. Blutgefasswande. Muller’s Arch., p. 96. 1850. 
Segond. Syst. capillaire sanguin. These. Paris, 1853. 
Remak. Entwickelung d. Wirbelthiere. Berlin, 1855. 
Remak. Klappend. Venen. Dent. Klinik. 1856. 
Hacked. Muller’s Arch. 1857. 
Luschka. Yirch. Arch. XVIII., p. 108. 1860. 162 
MANUAL OF HISTOLOGY. 
Hoyer. Arch. f. Anat., p. 244. 1865. 
Klbbs. Yirch. Arch. Yol. XXXII., p. 172. 1865. 
Aeby. Med. Cent. Zeit. No. XIV. 1865. 
Curzonszczewsky. Yirch. Arch. Yol. XXXV. 1865. 
Eberth. Yirch. Arch. Yol. XLIII., p. 136, and Centralblatt, p. 196. 1865. 
Auerbach. Yirch. Arch. Yol. XXXIII. 1865. Med. Cent. Zeit. No. X. 
Gimbert. Structure et texture des arteres. These. Paris, 1865. Journ. 
I’anat. et de la phys. Eobin, p. 536, 1865. 
Fasce, Luigi. Istologia della arterie. Palermo, 1865. 
Langhans. Virchow’s Arch. Yol. XXXVI., p. 197. 1866. 
His. Die Haute und Hohlen d. Korper’s. Basel, 1866. 
Legros. Journal de Vanat. et de la phys. No. 111., p. 275. 1868. 
Tolubew. Beitr. z. Kennt. d. Baues u. d. Ent. d. Capill. Arch. mikr. Anat, 
49. 1869. 
Ziegler. Exp. Unt. ueber d. Herk. d. Tuberkelelemente. Wurzburg, 1875. 
Ziegler. Unt. ueber pathol. Bind. u. Gefassneubildg. Wurzburg, 1876. 
Kolliker. Entwickelungsgeschichte. Leipzig, 1876. 
Disse. Arch. f. mikros. Anat. Yol. XYI., p. 1. 1879. 
Illtmann. Arch. f. mikros. Anat, Yol. XYI., p. 111. 1879. CHAPTER XII 
THE LYMPHATIC SYSTEM. 
Dr. W. R. BIRDSALL, New York City. 
Histological research has brought to light within recent 
years no more important or interesting facts than those con- 
nected with the lymphatic system; interesting, in exhibiting 
entirely new features in tissues which had previously been 
carefully studied ; and important in their physiological, and, 
particularly, in their pathological relations. 
Assisted by experimental pathology, it is still in this direc- 
tion that we are to look for advancement in pathological his- 
tology, for there can be no doubt that heretofore too little 
attention has been paid to the lymphatic system, both in its 
histological details and in its topographical anatomy. 
Present condition of the views on the structure of the lym- 
phatic system—Relations to the connective tissues.—Unfor- 
tunately we have still a great variety of contradictory observa- 
tions, and various interpretations of the same observations. 
Through this maze of uncertainties it is not easy to lead the 
student to a settled opinion, nor can all the phases of this many- 
sided subject be presented. It shall be our aim, however, to 
draw the outlines. If the student wishes to follow out the 
controversies, he will be aided by the references which are 
appended to this chapter. 
It may be said that we have, to a great extent, returned to 
the views of the older anatomists and physiologists, and be- 
lieve that the whole connective-tissue formation is a network of 
channels ; that its interstices are, directly or indirectly, con- 
nected with the lymphatic capillaries and larger vessels ; that, 
in short, the lymphatic system is pre-eminently a connective- 
tissue circulatory system, irregularly distributed, it is true, but 164 
MANUAL OF HISTOLOGY. 
found in one form or another wherever this tissue exists, and 
constituting in the serous membranes a great absorbent sys- 
tem, with its special connections, the lacteals, the lymphatic 
nodes or glands, and the fat-tracts. The important patho- 
logical processes, both acute and chronic, connected with these 
membranes are due principally to the fact that they are parts 
of this great lymphatic system. 
Of course we must not lose sight of the connections of the 
latter with the complimentary blood-vascular system ; the ten- 
dency has been too much in the opposite direction, however, 
and this more extensive, though less visible, system has been 
too often neglected in favor of its more prominent companion, 
in the consideration of processes of nutrition and of patho- 
logical changes. 
General histology of the lymphatic system Precious 
ideas.—ln describing the lymphatic system, only its general 
histology will be considered, the details of its special distribu- 
tion and arrangement being classed with the description of the 
different organs with which it is associated. Since the serous 
membranes have come to be regarded as important parts of the 
lymphatic system, being, in fact, great membranous expansions 
of that system, they are naturally and easily considered in con- 
nection with each other. It is not intended to treat of them 
here in their special details, but merely to make a general his- 
tological study of them as a class. It is convenient to begin 
with them in taking up the study of the origin of the lymphatic 
system. 
With Yirchow originated the theory that the starting-point 
of the lymphatics is from hollow anastomosing cells, the con- 
nective-tissue cells, whose prolongations communicate to form 
continuous tubes. He termed them plasma cells. Kblliker 
supported this doctrine, and a similar view was held by Ley- 
dig. Henle held a different opinion, whilst Briicke and Ludwig 
reverted to the ancient theory of Bichat, that the interstitial 
spaces of the connective tissue are the true sources of the lym- 
phatics. Recklinghausen, introducing nitrate of silver as a 
reagent, showed that the lymphatic vessels are lined, and the 
serous membranes covered, with flat cells, forming an endo- 
thelial layer. He observed the passage of milk and fine gran- 
ules, through openings in the central tendon of the diaphragm, 
from the peritoneal to the pleural surface. He believed also THE LYMPHATIC SYSTEM. 
that he had discovered a system of canaliculi in connective tis- 
sue, which he termed sap or juice canaliculi (saftkanalchen). 
His views, as modified somewhat later, are, that the connective 
tissue is traversed by serous canaliculi or 'plasmatic channels 
which are directly continuous with the lymphatic vessels. 
“Not mere fissures in the connective tissue, but interstices of 
the fibrous fasciculi and lamellae of connective tissue, cemented 
to one another by a tenacious, homogeneous, firm material, in 
which the serous canaliculi are buried.” 
The lymphatics of the mesentery.—A portion of the mesen- 
tery between the trabeculae, taken fresh from a cat and stained 
with nitrate of silver, exhibits on both surfaces an endothelial 
layer, the cells of which possess an irregular outline, marked 
by the deposit of silver, either in a supposed intercellular sub- 
stance or in crevices between the cells. Sometimes this outline 
is polygonal, sometimes sinuous, crenated, or even sharply den- 
tated. It may be an even, fine line, or it may possess irregu- 
larities as if beaded. At the union of these lines, that is, where 
two or more cells terminate, a round, irregularly triangular, or 
spindle-shaped spot may be often observed, which is stained 
like the intercellular line, or in a lighter or darker shade. 
There are other spots of larger size, presenting the appearance 
of openings ; we shall refer to them again. The surface of the 
cells may be clear, or granular, sometimes it is quite dark, vary- 
ing with the degree of staining and the condition of the tissue ; 
a nucleus can usually be seen at a slightly deeper level. This 
is plainly visible in unstained or slightly stained specimens, or 
where special reagents have been used to make the nuclei promi- 
nent, as hsematoxylin or picro-carminate of ammonia. The 
granular appearance spoken of is sometimes confined to a series 
of cells which surround a stoma, or the black spots mentioned, 
while the neighboring cells may be clear; in other cases, sev- 
eral corpuscles in the form of an irregular tract may present 
this appearance. 
Klein has observed cells which are club-shaped, undergoing a budding pro- 
cess, i.e., giving off little bodies resembling lymphoid corpuscles. He has given 
the term germinating endothelium to these cells. Other histologists have made 
similar observations. 
Underneath and around the nuclei a delicate, intricate, re- 
ticulum of elastic fibres may be seen plainly in unstained sped- 166 
MANUAL OF HISTOLOGY. 
mens, and by careful focussing in silver preparations. Accord- 
ing to Ranvier, they are connected near their point of union 
by a very thin, elastic, fenestrated membrane. Below the layer 
of elastic fibres is the connective tissue which forms the basis 
of the membrane. It consists of fasciculi, which are straight, 
or wavy, according to the degree of tension of the membrane, 
or its fasciculi are held together by the elastic fibres, which 
penetrate from the reticulum on each side. They usually pre- 
sent a decidedly convoluted appearance in ordinary specimens, 
and in consequence of the contiguous fasciculi not possessing 
corresponding convolutions, clear interspaces are seen. Some- 
times the fibres are very irregular in their arrangement. Ran- 
vier claims that an interfascicular membrane can be demon- 
strated here also. Ordinary fiat, branching connective-tissue 
cells are distributed through this tissue; they lie upon and 
between the fasciculi; they are particularly numerous under 
the endothelial layer. Lymphatic and blood-capillaries trav- 
erse the interspaces and run upon the fasciculi. In the mesen- 
tery and pleura they form a wide-meshed plexus ; in the peri- 
cardium a close plexus. 
To see the features of the deeper portions to advantage, we 
must remove the superficial endothelial layer before staining 
with silver. 
Klein's method of studying the omentum.—Klein has de- 
scribed a very careful process for doing this, and as he claims 
it must be followed in detail to obtain the results at which he 
has arrived, we reproduce it: “To prepare the omentum, a rab- 
bit is killed by bleeding ; the stomach is exposed ; after having 
pushed the intestine to the right side, the free surface of the 
omentum is pencilled several times from the large curvature 
toward the diaphragm, with a fine camel’s-hair pencil moistened 
with fluid of the abdominal cavity. After that, a\or i per 
cent, solution of nitrate of silver is allowed to flow over the 
omentum from a large capillary-tube until the membrane has 
become slightly milky (one or two minutes are generally suffi- 
cient) ; after that, the stomach, together with the omentum, 
spleen, pancreas, and a portion of the duodenum is cut out and 
transferred to a large capsule with distilled water ; after some 
time the water is renewed and the omentum is separated under 
water, together with the spleen and pancreas, from the stomach, 
with scissors, and is transferred to common water. Those parts THE LYMPHATIC SYSTEM. 
of the omentum which are seen to contain small patches are cut 
out and mounted A failure is more frequent than a 
success. Either the surface has not been pencilled enough, 
and then the endothelium of both surfaces is colored, and 
consequently, hardly anything is to be seen of the cellular 
elements of the ground-substance; or the surface has been 
pencilled too hard, and then the arrangement of the ground- 
substance is altered, its bundles appear considerably stretched 
and distinctly fibrillar.” 
When these patches referred to, found in the mesentery, 
and particularly in the omentum, are examined, they are ob- 
served, according to Klein, to consist of systems of somewhat 
flattened, finely granular, nucleated, branched corpuscles con- 
nected together ; the spaces which appear clear between them 
forming the lacunae and canaliculi, corresponding to Reckling- 
hausen’s lymph canalicular system. The nuclei of these cells 
are sharply defined, oval, and possess one or two nucleoli. 
Lymphoid corpuscles are found in these spaces, and also 
slightly larger corpuscles, which are supposed to be derived, 
in part, at least, from the branched cells by a process of bud- 
ding. Klein calls these patches lymphangeal patches or nod- 
ules, and lymphangeal tracts. He divides them into two 
classes. 
The perilymphangeal nodules or tracts which lie closely 
connected with, but principally outside of, the lymphatic ves- 
sels, are accumulations of more or less fiat, branched cells, 
which, by their growth and proximity to one another, make the 
canaliculi shorter or close them entirely. The second class de- 
velop within the lymphatic vessels, and are termed endolym- 
phangeal nodules or tracts. They consist of those which 
perfectly resemble adenoid or reticular tissue, and those which 
are formed of a reticulum of branched cells, their spaces being 
filled with liquid or a few lymphoid corpuscles. The last form 
may have a rich blood-capillary plexus, and the branched cells 
may possess buds, pedunculated and non-pedunculated, sup- 
posed to represent different stages in the formation of a lym- 
phoid corpuscle. These tracts and nodules are found most 
frequently in the neighborhood of the blood-vessels and trabe- 
culae. In young animals they are much less numerous and 
more isolated than in adults, where they have become fused 
into extensive tracts in consequence of the growth and division 168 
MANUAL OP HISTOLOGY. 
of the branched cells. Ranvier has described similar struc- 
tures under the name “ laches laiteuses 
Development of fat-tissue.—Their relation to the develop- 
ment of fat-cells is of extreme interest. If we accept the views 
of Klein and Flemming, the branched cells are converted into 
fat-cells, and the former observer has pointed out that, by fol- 
lowing up a perilymphangeal tract into a vascularized fat-tract, 
we may find all stages of conversion into fat-tissue. The fat- 
tracts are found in the same location as the perilymphangeal 
tracts, that is, along the larger blood-vessels, and the greater 
the number of the former the less there are of the latter. The 
conversion of branched cells into fat-cells varies in different 
animals, and in different membranes of the same animal, and 
under different conditions of nutrition. The formation of lym- 
phoid corpuscles, supposed to go on from the branched cells, 
must cease, necessarily, when they become converted into fat- 
cells, and it is found that they are, in fact, present in less num- 
bers when the latter process is going on. Let us consider the 
relations of these branched cells to the lymphatics. The larger 
blood-vessels are usually accompanied by a lymphatic on each 
side, which gives off branches at irregular intervals, finally 
breaking up into a capillary plexus, which may ensheath the 
accompanying blood-vessels, or even enclose a blood-capillary 
plexus. When the latter exists in a perilymphangeal nodule, 
the lymphatic capillary may apparently communicate directly 
with the lacunae and canaliculi, the endothelial cells compos- 
ing the capillary being continuous with those which invest the 
spaces, and covering externally, it may be, the blood-capillary 
as well (Klein, Delafield). 
Course and termination of the lymphatic radicles.—In 
tracing the lymphatic capillaries we find that they run in every 
direction, branching irregularly, and vary in calibre and num- 
ber in different parts. It is very difficult to trace one of them 
to a positive termination. The interstices of the connective- 
tissue fasciculi in brushed silver preparations sometimes pre- 
sent an irregular shape, as if they were enclosed by irregular 
cells. This appears to me to be often due to the convolutions 
of the fasciculi, made more irregular, perhaps, by a cement 
substance, or an interfascicular substance, either fluid or semi- 
fluid, which has been coagulated by the processes following 
death, and by the action of our reagents. The irregular action THE LYMPHATIC SYSTEM. 
of silver, which produces so many doubtful pictures, may aid 
in producing this appearance. The extreme mobility necessary 
in some forms of connective tissue demands extreme flexibility 
as a quality of its elements, thus facilitating great variation in 
structural arrangement under different conditions. 
Artificial injection of the lymphatics.—lf we inject this 
tissue, by puncture with a hypodermic syringe, we can fill the 
lymphatic vessels and 
also the interstices, so 
that they are continu- 
ous ; but the question 
whether this is a natur- 
al or an artificial trans- 
ition is one about which 
histologists still differ. 
Theoretically, we may 
consider that such com- 
munications exist to 
some extent, at least 
when greatly increased 
vascular tension takes 
place. But, at the same time, many, or even most of the in- 
terstices may be closed spaces. 
Fig. 75.—From mesentery of cat: silver-stained right por- 
tion denuded of endothelium, showing, A. branched colls, with 
B, intervening spaces ; left portion, endothelial layer preserved ; 
C, pseudo-stomata ; D, nuclei; E, elastic fibres. 
It is not a matter of great consequence, physiologically speak- 
ing, since not only fluids but lymphoid corpuscles can penetrate 
partitions which fail to resist so slight an injecting force as is 
sufficient to unite these spaces and the lymphatic capillaries.1 
The fact that injections can be made without forming a com- 
munication (Frey) does not prove that the latter does not 
exist; it may be due to an imperfect injection. As we shall 
see later, the wandering propensities of the lymphoid cor- 
puscles would almost exclude the possibility of the connective- 
tissue interstices remaining closed spaces everywhere. 
Endothelium and stomata.—We have already referred to 
1 Thoma and Arnold have shown that injections into the veins, in a living animal, 
of insoluble coloring matters (not distending the vessels, however), pass between the 
endothelial cells and find their way into the clefts and channels of the deeper tissues. 
The possibility of absorption taking place through the intercellular substance which, 
after all, may only be a semifluid material filling a space which varies in size under 
different conditions, throws light on many of the difficult problems of absorption, 
secretion, and excretion, and numerous pathological processes. 170 
MANUAL OF HISTOLOGY. 
Recklinghausen’s observation, that communication exists be- 
tween the abdominal and pleural cavities by means of small 
openings in the central tendon of the diaphragm. By injecting 
some insoluble coloring matter, held by fluid in suspension, 
into the abdominal cavity, he obtained a fine injection of the 
lymphatics of the central tendon, and was able to detect the 
substance on its pleural surface. The experiment may be re- 
versed by injecting the pleural cavity. He was able to see the 
actual passage of milk-globules into these openings by remov- 
ing a portion of the fresh tendon upon a cork ring, its pleural 
surface upward, placing a drop of milk upon it, and observing 
with the microscope the nearly round openings, large enough 
to admit at once two or three of the milk-globules which ran 
toward these openings in little eddies, and disappeared below. 
He stained this membrane with nitrate of silver, and found 
that the openings corresponded to perforations between the 
endothelial cells leading perpendicularly or obliquely to the 
lymphatics. Schweigger-Seidel and Doigiel observed similar 
openings leading from the abdominal cavity, through the retro- 
peritoneal membrane, into the cysternce lymphaticce magnce of 
the frog. Dybkowsky showed that colored fluids placed in the 
pleural cavity were absorbed by the lymphatics of the inter- 
costal pleura. Schweigger-Seidel, Doigiel, and Ludwig con- 
firmed the observations of Recklinghausen in connection with 
the central tendon of the diaphragm, and it is now generally 
admitted that such openings exist, not always freely open, 
however, but sometimes with a valve-like cleft. It must not 
be understood that the small bead-like spots and the dark 
spots between the cells are true stomata. It is not definitely 
known, in fact, what they really represent. Oedmannson first 
described them, not only on the serous membranes, but also 
on the endothelial layer of the chyle-vessels. They are very 
numerous directly over the lymph-vessels of the central tendon 
on its peritoneal surface (Dybkowsky). 
Ranmefs mews on false stomata.—Ranvier has an in- 
geneous theory explaining the formation of these objects, 
which have been termed false stomata, also of the true sto- 
mata and the fenestra of the omentum. He considers that the 
lymphoid corpuscles, which are always to be found in serous 
cavities, penetrate the membrane, making a depression or per- 
foration, sometimes remaining, sometimes escaping again. In THE LYMPHATIC SYSTEM. 
the majority of cases the black spots are formed by the albu- 
minous serum which these openings retain by capillary attrac- 
tion, having been coagulated and stained by the nitrate of 
silver, producing a plug. In other cases, a globular cell re- 
sembling a lymphoid corpuscle occupies the stoma, surrounded 
by a black margin due to the action of the silver. Other cells 
have a greater resemblance to small endothelial cells than to 
lymphoid corpuscles. The irregularity of their distribution in 
different membranes, in different animals, and at different 
ages, seems to favor the idea of such an accidental manner of 
formation. 
Klein on true and false stomata.—Klein divides the sto- 
mata rera, or true stomata, into two classes : a, those which 
form the mouth of a vertical lymphatic channel leading to a 
superficial vessel (they have a 
special endothelial lining); and 
b, those formed by discontinuity 
between the endothelium of the 
surface leading into a simple 
lymphatic sinus near the sur- 
face, and lined only on the lower 
surface with endothelium. Pseu- 
do-sonata, or false stomata, may 
be produced, according to this 
observer, by the prolongations of 
the sub-endothelial branched cells 
becoming free by projection out- 
ward between the endothelial 
cells. In pathological conditions he has seen an extensive 
cell-proliferation going on from one of these projecting pseudo- 
stomata. Ranvier accounts for the origin of the fenestra 
of the omentum in a similar manner, as for the stomata. It 
is of interest to know that the openings do not exist before 
birth, but increase in size and number as age advances. 
Klein, on the other hand, considers that the openings in the 
omentum are produced by a process of vacuolation. The 
arrangement of the connective-tissue fasciculi around these 
openings is not that of complete rings, but is such that each 
opening is bordered by several fibres which take part in the 
formation of other openings in consequence of the irregularity 
in their arrangement. The endothelial cells may form a com- 
Fig. 76.—Frond of fern (Osmunda Olayto- 
niana), under-surface showing stomata. 172 
MANUAL OF HISTOLOGY. 
plete tube in some of the narrow trabeculae, in which a sin- 
gle cell may complete the circumference. Klein states that 
when these openings take place, the connective-tissue cells pre- 
viously situated between the connective-tissue bundles, come 
to lie on the lateral surface which is now free. This, he 
thinks, establishes the fact that the latter may be converted 
into true endothelial cells. Delafield, in considering the ques- 
tion of the re-forraation of the endothelium on serous mem- 
branes, after hydrothorax, remarks that it would seem to be 
reproduced from the old endothelium, or from migrating white 
Fig. 77.—From silver-stained omentum of cat: A, fenestra; B, intercellular lines of upper surface; 
C, nuclei of same ; JD, intercellular lines of lower surface; B, nuclei of same ;F, nuclei in wall of opening; 
corresponding cell-forms, part of upper and part of lower surface. 
blood-cells, or from sub-endothelial connective-tissue cells, 
although he has not seen sufficient proof to establish any of 
these theories. 
The nerves of the peritoneum have been studied by Cyon. 
They enter the mesentery with the blood-vessels as fasciculi of 
medullated nerve-fibres, and, dividing laterally, lose their med- 
ullary sheath and form a plexus, the fibres of which show 
projecting nuclei at various points. The walls of the arteries 
receive a rich supply of these fibres. A lymph-space, surround- 
ing the fibres, can sometimes be demonstrated. 
Intimate structure of lymphatic vessels.—A lymphatic ves- 
sel may be considered as a serous membrane with only one free 
surface, rolled in the form of a tube, its endothelial layer form- 
ing the intima, resting upon an elastic reticulum, and an ad- 
ventitia or external envelope of connective-tissue fasciculi, as 
in the serous membranes. In the finest capillaries only the en- 
dothelial layer is independent, although they lie surrounded THE LYMPHATIC SYSTEM. 
by elastic fibres and connective-tissue fasciculi. In the larger 
trunks, smooth muscular elements form a middle layer. The 
endothelial cells of the lymphatics have a more sinuous outline 
than the spindle-shaped cells of the blood-capillaries ; they are 
often irregularly dentated like the cranial sutures. The calibre 
of the lymphatics is also much more irregular than that of 
blood-vessels. As they increase in size, the tissues external to 
the endothelium assume more and more the character of ves- 
Fio. 78.—Central tendon of the rabbit, treated with solution of nitrate of silver, the most superficial 
serous layer immediately adjoining the pericardium being shown; a, lymphatic capillaries ; b, their ori- 
gin ; c, serous canals with communications; d, serous canals equal in width to the origin of the lympha- 
tic vessels; e, blood-vessel with epithelial cells. Magnified 300 diameters. Recklinghausen. 
sels with independent walls ; they finally resemble the veins 
in the largest trunks, except that they possess more muscular 
tissue than the latter. 
The diameter of the lymphatic capillaries is very variable ; 
they are generally larger than the blood-capillaries, ranging 
from 0.013—0.045 mm. (Frey). Branches of 0.2256—.2609 mm. 
may possess three layers (Kolliker). The vessels are richly 
supplied with valves, which are formed from the intima. 
Variations in shape.—Here let us consider an important 
characteristic of the lymphatic system, viz., its irregularity. 174 
MANUAL OF HISTOLOGY. 
11l this respect it contrasts very decidedly with the blood-vas- 
cular system. In the calibre of its vessels in different regions, 
in different parts of the same organ, and even in different parts 
of the same vessel, it is extremely irregular. A vessel of small 
calibre may suddenly expand into a saccular shape, which 
may have its diverticula or branches, or may form a chain of 
lacunae. It is true that these dilatations are formed just in 
front and behind the valves quite regularly, but they are also 
found everywhere, being, in fact, a characteristic of these ves- 
sels. 
Topographical 'peculiarities.—Nor is a uniform direction to 
be observed in the distribution of these vessels, for while they 
usually accompany arteries, lying outside the accompanying 
veins, they frequently take strange courses. A lymphatic may 
suddenly leave its companions to strike across a comparatively 
non-vascular held of tissue to share its fortunes with another 
set of blood-vessels. Respecting the capillary lymphatics, 
their place seems to be the middle ground between the blood- 
capillaries, just where we would expect to find this drainage 
system.1 They lie deeper in the skin and mucous membrane 
than the blood-vessels (Recklinghausen). The dispute con- 
cerning the question as to whether the smaller lymphatics 
have a distinct wall or are simple spaces, probably has been 
largely due to the variation in the structure of the lymphatics 
in the same tissue or organ in different animals, or in the same 
animal at different ages. 
The thoracic duct, which represents the other extreme in 
the structure of lymphatic passages, has an endothelial layer 
supported by a reticulum of elastic fibres, which mingles with 
the next layer, consisting of smooth muscular elements run- 
ning in every direction, the transverse elements predominating. 
The adventitia of connective-tissue fasciculi and elastic fibres 
completes its coats. The muscular layer in man is highly de- 
veloped compared with quadrupeds (Ranvier). 
1 On the external ear of a rat whose blood-vessels are injected with colored gela- 
tine, and whose lymphatic vessels are rendered visible by silver, the larger centrifu- 
gal lymph-vessels are seen, even with low powers, to be surrounded by a network of 
blood-capillaries. The same has been demonstrated in the mesentery, the dia- 
phragm, and the posterior extremities.—Ueber ein die Lymphgefasse um-spinneudes 
Xetz von Blutcapillaren, von Alex. Dogiel. Arch. f. mikroskop. - Anat, Bd. 17. 3. 
Heft, S. 335-340. THE LYMPHATIC SYSTEM. 
The subarachnoid and subdural lymph-spaces and their 
prolongations.—Axel Key and Retzius have shown that be- 
sides the great subarachnoid and subdural lymph-spaces of 
the brain and spinal cord, connecting with them are spaces en- 
closing the nerve-libres of the cord, and, what is still more 
remarkable, extending outward on the peripheral nerves. The 
nerves of special sense, the olfactory, the optic, and the audi- 
tory, form no exception to this rule. Even the ganglia of the 
system and their fibres have similar spaces, which 
are in connection with the cord. Nor is this the end of the 
intricate labyrinth. Each nerve-fibre has a space immediately 
outside of the sheath of Schwann, between the latter and the 
so-called fibrillary sheath, through which it communicates with 
the perineural sheath-space, and through the latter with the 
lymph-spaces of the central nervous system. That they are 
true lymphatic spaces is shown by the fact that they are lined 
by a layer of endothelial cells. Obersteiner demonstrated by 
injections that the nerve-cells also possess pericellular spaces 
connected with those of the corresponding fibres, a fact which 
1 can corroborate. Key and Retzius say that this whole lym- 
phatic system is nowhere in direct communication with the 
ordinary lymphatic system, and that they have never seen the 
latter injected through the former, except when extravasation 
occurred. Bogras was the first (1825) to inject the nerves. He 
used quicksilver, and succeeded in injecting the peripheral 
nerves up to the ganglia, and made injections from the dura 
down to the ganglia. He failed with the olfactory, optic, and 
acoustic. Cruveilhier, and later, Robin, confirmed the fact 
that such injections are possible. Robin, in 1858, and after- 
ward, His, in 1863, demonstrated the perivascular lymph- 
spaces of the central nervous system. 
Lymphatics of tendons.—-Axel Key and Retzius, and also 
Hertzog, have shown that the tendons possess spaces which 
may be injected. From the spaces formed by the endotenium 
and the peritenium, which communicate, connections exist 
with the deep and superficial lymphatics of the tendon. 
The development of the lymphatics is by a process of bud- 
ding and vacuolation similar to that which takes place in the 
blood-vessels. 
Lymphatic glands.—We now pass to the consideration of 
the lymphatic bodies called glands, ganglia, or nodes. Their 176 
MANUAL OF HISTOLOGY. 
distribution does not concern us liere; it is sufficient to say 
that they are very variable in size and number in different 
regions, being supplied to nearly all the lymphatic trunks, 
with which they are connected by the so-called afferent and 
efferent branches. The former usually consist of several small 
branches ; the latter generally enter as single large trunks. 
The shape of the lymph-nodes may be spherical, oval, ob- 
long, or reniform. In the latter, which is by far the most fre- 
quent form, the afferent vessels penetrate the capsule on the 
convex surface, while the efferent branch escapes at the hilus. 
In the other forms it is difficult to determine which are the 
afferent and which the efferent vessels. A lymph-node con- 
sists essentially of spheroidal and cylindrical masses of reticular 
tissue, containing lymphoid corpuscles, richly supplied by a 
blood-capillary system, and sustained in place by a framework 
of connective tissue, with elastic and sometimes muscular ele- 
ments, forming a network around the masses for the circula- 
tion of lymph, and expanding externally to form a capsule. 
The gland is usually divided by histologists into a cortical and 
a medullary portion, the former being simply that part in which 
the lymphoid masses assume a spheroidal form (the follicles), 
this being the more peripheral portion of the node, or the part 
farthest from the hilus, when that exists. The medullary sub- 
division represents the remaining portion, and its lymphoid 
material is in the form of cylindrical or cord-like prolongations 
from the follicles. The capsule is composed of connective tis- 
sue, the fibres of which run in different directions in its exter- 
nal layers, possessing elastic fibres, flat cells, and a slight 
amount of fat-tissue. The lymphatics of the capsule are found 
mostly in its outer layers. The inner layers present a more 
stratified appearance on account of the regularity of their 
bundles and the interposed connective-tissue cells. An elastic 
network and smooth muscular elements are found here, and 
also in the septa, and are developed in some animals to a high 
degree. It is from the inner layers of the capsule that the 
septa are given off to form the framework of the node. These 
consist primarily of trabeculae, which, passing between the fol- 
licles, converge toward the medullary portion, where they inter- 
lace with the lymphoid cords of the latter, and may again unite 
at the hilus (stroma of His). They have a structure similar to 
that found in the portion of the capsule from which they have THE LYMPHATIC SYSTEM. 
tlieir origin. These septa are not complete partitions, but consti- 
tute an open framework, which, in consequence of its radiating 
arrangement, produces wider spaces in the cortical than in the 
medullary portion. To this the follicles correspond by being 
broadest at their peripheral portions. It must not be under- 
stood that the lymphoid masses, either follicular or cylindri- 
cal, are closely embraced by the septa ; they are separated from 
the latter, and from the sheath as well, by spaces, the “ invest- 
ing spaces of the follicular portion” (Frey), or sinuses of the 
Fig. 79.—Section of the medullary substance of a lymphatic gland from the ox: a, follicular cord ; 6, 
trabecula;; c, path pursued by the lymph; d, blood-vessels. Magnified 300 diameters. Recklinghausen. 
cortical substance (Ranvier), and the lymph-passages (Frey) 
or cavernous plexus (Ranvier) of the medullary portion. These 
spaces are maintained by a network of line fibres (tenter-fibres 
of Frey) derived from the septa, being given oil at nearly right 
angles to the latter. The bundles of fibres composing them 
divide and reunite, forming meshes, and extend to the follicles 
and cords. In reality, they do not end here, but are continued 
to form the reticular tissue of these bodies by dividing into a 
still finer network, which differs in the different portions only 178 
MANUAL OP HISTOLOGY. 
by slight variations in the size of the meshes and the fineness of 
the fibres, the meshes being longer and narrower in the peri- 
pheral portions of the follicles and in the cords than in the 
central part of the former. This sort of tissue has received 
different names: cytogenous tissue (Kolliker), adenoid tissue 
(His), reticular tissue (Frey, Ranvier). It is, as the latter name 
implies, a network, the fibres of which run in every direction, 
being applied to one another in the same manner as the fibres 
of the omentum already described. The nuclei, which are 
more oval and larger than the lymphoid corpuscles, appear at 
the junction of fibres, simply rest upon them, and can be re- 
moved by brushing. They are endothelial cells, and in silver- 
stained preparations an endothelial layer can be seen to cover 
the septa, the reticulum of the lymph-passages, and the folli- 
cles in the same manner that the fine bundles of the omentum 
are covered ; that is, the spaces between the bundles are no- 
where covered, but each bundle is wrapped by these cells. 
This can only be seen after the lymphoid corpuscles that occupy 
the meshes have been removed by brushing. The endothelial 
layer is continuous with that of the afferent and efferent lym- 
phatic vessels, which communicate with the lymph-spaces of 
the node, as shown by injections. 
According to Klein, the clinical nature of reticular tissue 
does not correspond to connective tissue proper or to elastic 
tissue. Filling the meshes of the follicular and cylindrical 
portions of the lymphoid masses are the lymphoid corpuscles, 
two or more in each mesh. Lymphoid corpuscles are also 
found in the investing or lymph-spaces, but they are easily 
brushed out, while a much longer brushing is required to de- 
tach them from the other portions. The corpuscles are some- 
what larger than the colorless blood-corpuscles, though vari- 
able in size. They possess a single prominent nucleus, which 
is readily stained by most coloring matters. The amount of 
protoplasm they possess is small. When examined in a moist 
chamber at a temperature of 80° to 87° C., some of them ex- 
hibit amoeboid movements, the small ones having the least 
protoplasm around their nuclei being most active (Ranvier). 
Klein states that corpuscles are to be found which are larger 
than the others, having more protoplasm, and often two nuclei. 
He considers them in a more advanced stage of development 
than the others. THE LYMPHATIC SYSTEM. 
179 
The arteries and veins of the lymphatic nodes have their 
chief entrance at the hilus, with the efferent lymphatic vessels. 
The main trunks divide to pass into the septa. Still finer 
divisions pass into the reticular tissue, forming a rich capillary 
network in the follicles and cylinders, most marked at the sur- 
face of these bodies. In the cylinders a single axial arterial 
branch, surrounded by a peripheral capillary system, may fur- 
nish the supply. Another source of blood-supply may be from 
the capsule ; small branches, both arterial and venous, which 
ramify in its layers, send finer branches inward, encircling the 
follicles and traversing the septa and reticulum of the lymph- 
spaces. The capillaries possess, besides their proper wall, a 
sheath derived from the reticulum. 
Nerves of the lymphatic nodes.—Little is known on this 
point. Nerve-fibres enter with the blood-vessels in some of 
the larger glands of man (Kolliker), and non-medullated nerve- 
fibres have been seen in the lymphatic nodes of the ox. Con- 
cerning the lymphatics, they exist, as we have seen, in the 
outer layers of the capsule, and do not differ from those in 
other regions, forming a network in the capsule. They are 
continuous externally with the afferent lymphatics, and inter- 
nally with the lymph-spaces already described. 
The numerous lymphoid organs are all constructed upon a 
plan similar to that of the nodes, in that they all represent 
modifications in the arrangement of reticular tissue and its 
vascular supply. 
Injection of a lymphatic gland.—We may obtain an injec- 
tion of the lymph-passages in the node by puncturing the 
capsule with an ordinary hypodermic syringe (a method for 
which we are indebted to Hyrtl), and injecting a mixture of 
Prussian blue and gelatine (soluble blue, 25, solid gelatine, 1). 
It is best to inject one of a series of connected nodes, in place, 
exposing them by dissection in a freshly killed animal. One 
gland is then injected from the other through the afferent and 
efferent vessels (Ranvier). They are excised and hardened in 
Muller’s fluid or alcohol; sections are then made with a micro- 
tome, after which they may be washed in water, stained for a 
few minutes in picro-carminate of ammonia (1 per cent.), again 
washed, and then mounted in glycerine or Canada balsam. 
Method of studying the gland substance.—For the purpose 
of demonstrating the reticulum of the lymph-spaces and the 180 
MANUAL OF HISTOLOGY. 
lymphoid masses, the node must be hardened in alcohol, bi- 
chromate of potassa, or (Ranvier’s method) placed for twenty- 
four hours in a concentrated solution of picric acid; sections 
are then to be made, after which they are gently brushed and 
agitated in water with a camel’s-hair brush to disengage the 
lymphoid corpuscles (we are indebted to His for the method of 
brushing). After staining, preferably with hematoxylin, which 
exhibits, in a beautiful manner, the lymphoid corpuscles and 
the darker nuclei of the endothelial layer, they may be 
mounted in the usual manner. 
Ranmef s plan.—The plan particularly recommended by 
Ranvier is as follows: the node remains for twenty-four hours 
in a mixture of alcohol (36° Cartier), one part, water, two 
parts ; then for twenty-four hours in a syrupy solution of gum- 
arabic, and is afterward hardened in alcohol sufficiently for 
section cutting in a microtome. Floating them in a shallow, 
flat dish, in water two or three centimetres deep, the gum is 
dissolved, and the brush used in a very delicate manner ; the 
sections may then be stained and mounted, as described above. 
The degree of hardness, and the force and duration of the brush- 
ing process, will determine the result, which practice only will 
make perfect. The lymphoid corpuscles in the lymph-passages, 
that is to say, in the parts which fill with the blue injection 
fluid, as previously described, are first removed, and additional 
brushing, when the proper degree of hardening has been at- 
tained, will enable one to remove these bodies from the folli- 
cles and cords, and also to remove the endothelial cells which 
rest upon the fibres of the reticulum and septa. 
Other methods of injecting glands.—A node removed imme- 
diately after death and injected by puncture with a 1 per cent, 
solution of hyperosmic acid, then placed in water for one or 
two hours, and afterward hardened in alcohol, cut in sections, 
colored by picrocarminate of ammonia, and mounted, gives 
good results. 
The best method for showing the endothelial layer is by 
interstitial injection (puncture) with a solution, of nitrate of 
silver, I—3oo1—300 ; harden afterward by freezing, and make sec- 
tions. 
Before closing this chapter, let us take a retrospective view 
of our subject. In doing so, it is almost impossible to avoid 
associating the connective-tissue cell with other forms which THE LYMPHATIC SYSTEM. 
181 
seem to be its antecedents, modifications, or derivatives, viz., 
the extensive system of branched corpuscles in the matrix of 
the serous membranes, whose growth and proliferation form 
large tracts when they possess a sufficient blood-supply, and 
between which the lymph circulates, affording a channel of 
escape for the discha.' ged bits of protoplasm, their offspring ; 
the throwing off of similar bits of protoplasm by the surface 
endothelium of the serous membranes; the probable transfor- 
mation of the branched cells into fat-cells, and the conversion of a 
branched connective-tissue cell into an endothelial cell, when it 
reaches a free surface. Again, the fact that similar endothelial 
cells line the blood and lymph channels, and also cover the reti- 
culum of the lymphatic nodes and follicles, and that in the 
latter forms, when we have also a rich capillary blood-supply— 
that is, a supply of oxygen—the accumulation and probable 
elaboration, if not proliferation, of lymphoid corpuscles goes on 
in a more extensive manner than in the lyrnphangeal tracts ; 
taken together, all point to the idea that they are different 
forms of protoplasm which have been converted, or are con- 
vertible, one into the other under proper conditions of tempera- 
ture, food-supply, and excitability, the definite limitations of 
which are but imperfectly known. 
In the germinating tracts, superficial and deep, of the serous 
membranes, in the lymphatic nodes and follicles of the ali- 
mentary canal, and also in the lymphoid organs (spleen, ton- 
sils, etc.), we have active forms, reproduction by budding, and 
division. The formation of the lymphoid corpuscles, which 
may be considered as so many amoebae sporting in a nutritious 
fluid, and engorging themselves with that which is brought to 
them by the agency of the absorbents and lymph-channels, 
under conditions favorable to great activity, free to penetrate 
most of the tissues, and, perhaps, become fixed forms. These 
processes of activity, when confined to the limits of the organs 
mentioned, are conducive to life and growth, but occurring in 
the allied forms that have become fixed, as the corneal branched 
cells, the connective-tissue cells, or the endothelial cells, to any 
considerable extent, inaugurate the processes of disease and 
death. Thus these comparatively indefinite and undifferen- 
tiated forms of protoplasm may be said to be keys to life and 
death. 182 
MANUAL OF HISTOLOGY. 
BIBLIOGRAPHY. 
Authors referred to in the text: 
Bichat. Anat. gen. Second edition. 1813. 
Ibid. Traite des membranes. 1816. 
Rejiak. Muller’s Archiv. 1850. 
BiiiiCKE. Ueber die Chylusgefas.se, etc. Sitzb. der Wiener Akad. 1853. 
Leydig. Lehrbuch d. Histologic, etc. 1857. 
Virchow. Cellular Pathology. 1860. 
Oedmannson. Virchow’s Archiv. Bd. 26. 1863. 
Chrzonszczewsky. Virchow's Archiv. Bd. 31, 1864. 
His. Archiv f. mikrosk. Anat. Bd. I. 1865. 
Schweigger-Seidel and Doigiel. Arbeit, a. d. phys. Lab. z. Leipzig. 1866. 
Kolliker. Handbuch der Gewebelehre. 1867. 
Cyon. Arbeit, a. d. Phys. Anstalt. in Leipsig. 1868. 
Robin. Diet. Ency. Sc. Med. 1870. 
Recklinghausen. The Lymphatic System. Strieker’s Histology. 1872. 
Klein. The Lymphatic System. 1873. 
Dybkowsky. Arbeit, a. d. Phys. Anstalt. in Leipsig. 
Arnold, J. Archiv f. path. Anat. Bd. 58, p. 303. 1873. 
Thin. Proc. Royal Soc. Vol. 22. 1874. 
Thoma. Centralbl. f. d. med. Wiss. 1875. Archiv f. path. Anat. Bd. 64. 1875. 
Key, Axel, and Retzius. Archiv f. mikrosk. Anat. Bd. IX. 1875. (Abstract of 
large work on the nervous system.) 
Hertzog. Zeitschr. f. Anat. und Entwick. 1875. 
Ranyier. Traite technique d’histologie. 1877 et seq. 
Delafield. Path. Studies. New York, 1878—80. 
Frey. The Microscope, etc. New York, 1880. 
Among the more recent authors that have written on this subject are : 
Hoggan. Proc. Royal Soc, 1876—77, (Two articles.) 
Lewis. Proc. Roy. Society. 1877. 
Robin and Cadiat. Journ. de I’anat. et de la phys. 1876. No. 6. 
Budge. Arch. f. mikrosk. Anat. Bd. X. 1876. 
Riedel. Archiv f. mikrosk. Anat. Bd. XI. 1877. 
Wittich. Mittheil. a. d. k. phys. Lab. 1878. 
Mierzyewski. Jour, de I’anat. et de la phys. Paris, 1879. 
Renaut. Comptes rendus Acad, des Sci. Paris, 1879. 
Weber-Liel. Arch. f. path. Anat. Bd. LXXVII. 1879. 
Fischer. Arch. f. mikr. Anat. XVII. 1879-80. 
Sitna. Wien. med. Presse. XXI. 1879. CHAPTER XIII. 
THE LIVER AND BILIARY APPARATUS. 
DR. ABRAHAM MAYER, 
Late Curator of the Manhattan Eye and Ear Hospital, New York City, etc. 
The liver is enclosed in a connective-tissue capsule, the 
peritoneum, which also gives off secondary folds, or duplica- 
tures, called ligaments, by which the organ is held in proper 
connection with the adjacent parts. The thickness of the cap- 
sule is about 0.03 mm., and its free surface is covered with the 
flattened corpuscles that belong to serous membranes gener- 
ally. Tliis connective-tissue covering is furthermore composed 
of thin laminae, which contain a large number of elastic fibres. 
At the transverse fissure, where it is continued into the inte- 
rior of the organ, the same character is maintained. Here it 
encircles vessels, ducts, and nerves, forming the so-called 
Glisson’s capsule, which, indeed, with its minute ramifications, 
traverses the whole interior of the gland. The liver contains, 
in addition to the glandular substance, blood-vessels, lympha- 
tics, nerves, and gland-ducts, the whole held together by the 
framework of connective tissue just mentioned, which in the 
human species is but imperfectly developed. 
The hepatic lobules.—The glandular parenchyma consists 
of the so-called hepatic lobules, which in the human liver are 
not completely separated from one another, for the reason 
just named. In some of the lower animals, however, this sepa- 
ration is more perfect. In the hog’s liver, for example, the 
septa are so well developed that the lobules are plainly recog- 
nizable by the naked eye. 
To isolate the human lobules is a matter of some difficulty ; 
but it can be accomplished by macerating the organ in water 
from twelve to twenty-four hours. 
These lobules are also known as the hepatic acini, or in- 184 
MANUAL OF HISTOLOGY. 
sulcb of the liver. Their form is irregularly polyhedral, and 
they usually measure about 4xl mm. At their bases they 
are attached to short twigs of the hepatic vein, which have a 
thickness of from 0.03—0.06 mm., and traverse the lobules in 
the axes of their long diameters. As the hepatic vein ascends 
through the lobule, it gives off innumerable capillary branches, 
almost at right angles to its course. The latter pursue their 
way to the periphery of the lobule, and hence have a radial 
direction. These capillaries further subdivide within the lob- 
ules, and are united to each other by transverse branches, 
forming a network with small meshes. At the periphery the 
capillaries join the rami- 
fications of the portal 
vein. The latter divides 
within the liver into nu- 
merous branches', which 
again subdivide at the 
surfaces of the lobules. 
Their ultimate ramifica- 
tions form the boundary 
lines between adjoining 
hepatic lobules, and it 
is for this reason that 
they have been called 
interlobular reins.1 For 
a similar reason the 
branches of the hepatic vein, which traverse the centres of 
the lobules, have been called intralobular1 or central reins2 
(Fig. 80). 
Pig. 80.—Injected liver of rabbit, showing branches to 
portal vein, capillaries, and the hepatic veins in the centres of 
two lobules. Prey. 
The interlobular veins are contained within interlobular or 
intermediate (Hering) canals ; these are easily demonstrable in 
the hog’s liver. In this animal the adjoining edges of three 
or four hepatic lobules combine to form a canal which con- 
tains the interlobular vessels. The latter are surrounded 
connective tissue, which is continuous with that of the septa 
between the lobules. In the human liver there is a similar 
arrangement, but in it the septa of connective tissue do not 
completely separate the lobules, and, excepting at the inter- 
1 Kiernan ; Philosoph, Trans., 1833. 
2 Yense Centrales, Krugenberg, Muller’s Archiv, 1843. THE LIVER AND BILIARY APPARATUS. 
lobular canals, tlie parenchyma of contiguous lobules appears 
to coalesce. 
Nevertheless, the substance of the human liver can be di- 
vided into distinct lobules, and the terminal branches of the 
portal veins may be regarded as their natural boundaries (Figs. 
80 and 87). Starting with the portal veins, therefore, the course 
of the blood is as follows : portal veins, interlobular veins, cap- 
illaries, intralobular veins, hepatic veins, and inferior vena 
cava. 
Sublobular veins, according to Kiernan, are such branches of the hepatic 
vein as are placed under the bases of several lobules, and collect the blood 
from their central veins. 
The liver may be injected either through the portal or he- 
patic veins, or through both. Good specimens may be ob- 
tained by injecting the fresh liver of a dog or rabbit with 
carmine - gelatine through 
the portal vein, then inject- 
ing fluid Berlin blue into the 
hepatic vein, and afterward 
hardening the organ in alco- 
hol. The central vein and 
adjacent capillaries will thus 
be filled with a blue mass, 
while the interlobular and 
portal veins, with the per- 
ipheral capillaries, will con- 
tain the transparent red 
mass. 
The color of the cut sur- 
face of the liver in its natu- 
ral condition is of a uniform reddish brown tint, and its lobular 
structure is not readily made out. Usually, however, we find 
two shades or gradations in color; one, corresponding to the 
central veins of the lobules, is of a dark red ; the other, corre- 
sponding to the periphery of the lobules, is a lighter and yel- 
lowish red. 
Fig. 81.—Transverse section of a human lobule, 
showing opening for central vein. Ecker. 
Occasionally these conditions are found to be reversed, 
and the difference of color is due to the fact that after death 
the central and other hepatic veins are filled with blood, while 
the portal and its branches are empty ; and also because 186 
MANUAL OF HISTOLOGY. 
the deposit of bile-pigment takes place at the centres of the 
lobules about the intralobular veins ; whereas a fatty infiltra- 
tion, such as may occur in normal livers, takes place at the 
periphery. Not uncommonly the yellowish red color at the 
boundary of the lobules exists under the form of delicate 
markings, which are nothing more than the empty interlobular 
branches of the portal vein. 
Kiernan occasionally observed in young subjects that the portal vein was 
distended with blood, while the hepatic vein was empty. In such cases the 
periphery of the lobules was of a darker color than their centres. 
The blood-vessels of the liver.—These have been partly de- 
scribed above. The hepatic artery, and duct, and portal vein 
enter the liver at the transverse fissure, enclosed within Glis- 
son’s capsule, and continuously subdivide as they push their 
ivay through the parenchyma. The subdivisions of the portal 
vein never anastomose, but are distributed around the surfaces 
of the lobules, forming their boundaries. At thd periphery 
they break up into capillaries which enter the lobules. These 
are about 0.02 mm. in diameter, and form a network, the 
meshes of which are scarcely wider than capillaries. Within the 
lobule the capillaries unite to form the central vein, and these 
then empty into branches of the hepatic vein. The subdivi- 
sions of the hepatic vein are also devoid of anastomoses, but 
after traversing the posterior portion of the liver in canals 
(which they embrace closely), unite to form the hepatic vein. 
A peculiarity of this latter vein is the fact that its larger 
branches give off successively small lateral twigs, which enter 
the bases of the neighboring lobules, so that after dividing 
such a branch lengthwise it would seem to be pierced by small 
circular openings, which are the orifices of the lateral branches. 
Not unfrequently a central (hepatic) vein will divide into 
two branches within a lobule, in which case the latter seems 
to possess two apices, which become joined together as we ap- 
proach its base. The connection between the portal and hepatic 
veins takes place only through their capillaries. 
The hepatic artery is comparatively small. It enters the 
liver together with the duct and portal vein, and at once breaks 
up into branches, which, anastomosing with each other, form a 
large-meshed network. The arterial branches are distributed 
to the vessels mentioned, which they enclose, and also to the THE LIVER AND BILIARY APPARATUS. 
connective tissue which surrounds the latter. The hepatic arte- 
ry also gives off nutrient branches which supply its own walls, 
and small twigs, which, piercing the substance of the liver be- 
tween the lobules, supply the branches of the hepatic vein. 
The ultimate branches of the artery are contained within the 
interlobular canals, and break up into capillaries at the peri- 
phery of the lobules, which they traverse for a short distance 
to form a distinct network. There is no communication between 
the intralobular capillaries of the hepatic artery and those of 
the portal vein. The former seem destined to supply the ad- 
jacent vessels, and probably the small amount of intralobular 
connective tissue to be spoken of hereafter. 
It has been thought by some (Ohronszewski, Ilindfleisch, and others) that the 
capillaries of the hepatic artery end midway between the interlobular and cen- 
tral veins, within the lobule. Beale and Kiernan have noticed that an arterial 
branch here and there enters a lobule; while Theile, Davis, and others describe 
a capillary network about the periphery of the lobules. 
Finally, branches of 0.05 to 0.1 mm, in diameter are dis- 
tributed to the capsule of the liver, where they break up into 
capillaries, radiating in all directions and anastomosing with 
each other to form a large-meshed network, which communi- 
cates with the capillaries of the phrenic, mammary, and supra- 
renal arteries. This plexus empties into small twigs, the so- 
called inner roots of the portal vein. 
The capillaries of the liver may be injected either through 
the hepatic or portal vein, or both, as before stated. For in- 
jecting the hepatic artery the author prefers his cold solution 
of carmine-glycerine.1 The gland to be injected must be as 
fresh as possible. If, for example, a dog be selected for this 
purpose, the abdomen should be opened and the animal allowed 
to bleed to death by section of the vena cava. Now introduce 
into the hepatic artery the canula of a syringe tilled with the 
carmine-glycerine, secure it in place and inject. Harden the 
organ in alcohol, cut sections, and mount in balsam. The liver 
will not be uniformly injected, and only those portions can be 
utilized in which the injected mass seems to be widely diffused. 
If, in addition to the artery, the hepatic vein be injected 
with a blue colored mass, beautiful results may be obtained. 
Sections in which the lobules are cut transversely show the 
1 See chapter oa the Kidney. 188 
MANUAL OF HISTOLOGY. 
central veins occupying the position of the axes of the lobules 
and the capillaries, pursuing a radial course and anastomosing 
with each other by transverse communications. 
Since the capillaries successively divide from the centre 
toward the periphery, it follows that they are much less numer- 
ous at the former than at the latter point. A section through 
the long axis of an acinus will show that the central vein is 
divided lengthwise, and that the capillaries are given off from 
it almost at right angles to its course. 
Nearer the summit of the lobule, however, the central vein 
is seen to break up into diverging capillaries. If the section 
has been made to one side of the central vein, but yet parallel 
with its axis, many capillaries will be cut across, more or less 
transversely, and will then appear as small, circular, or oval 
rings. 
The connective tissue of the liver.—Glisson’s capsule is 
formed of longitudinal bundles of connective tissue which are 
loosely interwoven. It serves 
to bind together the hepatic 
artery, portal vein, and hepatic 
duct, and also fills out the 
small spaces left between the 
ramifications of these vessels 
(Fig. 82). Sections from a liver 
hardened in chromic acid or 
alcohol, and immersed in a di- 
lute solution of caustic potassa, 
or simply pencilled, show the 
connective tissue well. About 
the hepatic vein it is thin and 
dense, and firmly united to the glandular structure, so that 
when cut transversely these vessels appear to gape. In the 
camel the connective tissue is greatly developed,1 even more so 
than in the hog. The interlobular septa are very dense and 
fibrillated ; in the interior of the lobule the connective tissue 
has a lamellar structure. 
Fig. 82. —Connective tissue of a child’s liver, 
after hardening in alcohol and pencilling: n, a, 
capillary vessels containing a few blood-globules ; 
6. 6, connective-tissue fibrils ; c, c, liver cells not 
removed by pencilling. Frey. 
According to Ewald and Kuehne, minnte bundles of fibrous tissue extend 
beyond this interlobular connective tissue, and piercing the lobules eventually 
surround the central veins. 
1 Turner, Wm., Journal of Anat. and Phys., Yol. XI., p. 2. THE LIVER AKD BILIARY APPARATUS. 
The liver-cells.—The liver-cells are found lying within the 
meshes of the capillary network of the lobules. If we bear in 
mind the shape of the intralobular capillary reticulum, the 
arrangement of the hepatic cells will be readily understood. 
The meshes of the capillary network have about the same 
diameter as the capillaries themselves. Hence it follows that 
the cells which occupy these meshes must also have the appear- 
ance of a reticulum. Hut inasmuch as the vascular meshes 
contain two or three liver-cells, it is evident that two neighbor- 
ing capillaries must be separated from each other by at least 
one liver-cell. Hence, in sections where the capillaries are cut 
transversely, their circular openings will be surrounded by a 
ring of liver-cells, or a circle of capillaries will enclose a mass 
of glandular substance. In sections which cut the central 
vein transversely the radiating capillaries will enclose radiat- 
ing rows of liver-cells. (See Fig. 81.) These are either joined 
to one another by the intervention of other liver-cells, or 
they are separated from one another by transverse capillary 
branches. 
On the other hand, in sections where the central vein is cut 
lengthwise, the (nearly) parallel intralobular capillaries will ap- 
pear separated from one another by correspond- 
ing rows of liver-cells. The glandular substance 
of the liver would then be composed of small, 
solid columns or rows of cells united to each 
other by other cells, thus forming one connected 
mass, and containing within its meshes the cap- 
illary network. In the fresh state the liver-cells 
appear as spherical or egg-shaped bodies, usu- 
ally presenting facets. They are somewhat flat- 
tened by being pressed against one another (Fig, 
83). Corpuscles possessing processes are some- 
times found. 
Fig. 83. Human 
liver-cells: a, with sin- 
gle nucleus; 6, with 
double nucleus. Prey. 
The hepatic cells are about 0.013—0.02 mm. 
in diameter, and possess one or two nuclei,1 which are gener- 
ally spherical, although they occasionally appear to be bat- 
tened ; the diameter is 0.006—0.007 mm. The liver-cells do 
not possess any membrana propria, but a hardened boundary 
layer seems to exist in its place. It is probable also that the 
1 Occasionally three or five nuclei, especially in young subjects (Beale). 190 
MANUAL OF HISTOLOGY. 
cells are bound together by a colloid substance, although this 
is a point which has not yet been definitely settled. 
Sections of a dog’s liver, immersed for a short time in dilute osmic acid, will 
occasionally exhibit a brown or black tracing between adjoining cells. Pres- 
sure on the cover glass will part them and leave the darkened material free in 
the field of vision. I have satisfied myself that this tracing is not of a nerve, 
biliary duct, or connective-tissue fibril; it is either a portion of the boundary 
layer of a liver-cell, or, as I suppose, a colloid substance between two cells. 
This appearance, however, is not constant. 
The protoplasm is of a dark brownish or greenish color. It 
is viscid, and contains numerous granules of small size, in ad- 
dition to smaller or larger fat-droplets.1 In livers hardened by 
chromic acid or alcohol, the shrinkage of the cells causes them 
to appear polyhedral, and they also seem much darker than in 
the fresh state. If the portal or hepatic vein has been injected, 
the cells will show distinct indentations produced by the dis- 
tended capillaries. 
When liver-cells are treated with diluted acetic acid, their 
protoplasm becomes pale, while their nuclei are rendered more 
conspicuous. In a dilute solution of caustic potassa the cells 
swell up, become rounded, and are finally dissolved. With 
water they also swell up, become paler and more rounded, and 
at length disintegrate. In the fresh state, by the addition of 
an indifferent fluid (£ per cent, solution of chloride of sodium, 
or iodized serum), the liver-cells are said to show protoplasmic 
movements. The granular substance of the liver-cells has 
been shown (by Schiff, in frogs, and by Nasse, in certain mam- 
malia) to consist of an animal amylum, which is converted into 
sugar through the agency of a peculiar ferment. 
The fat-droplets may be either small in number and size or 
quite numerous and large. Not infrequently they coalesce to 
form larger fat-globules. In the so-called fatty infiltration they 
are very large, and compose the greater part of the cells. The 
nuclei are granular, and where two or more of them occupy 
the same cell, they may apparently be united to each other. 
1 According to Kupffer and Klein the substance of the cells is composed of a 
honeycombed network, i.e., an intracellular reticulum. Klein says the nucleus is lim- 
ited by a thin membrane, and includes an intranuclear network, containing occa- 
sionally one or two nucleoli. The intranuclear network is in continuity with the 
intracellular one, and the network of contiguous cells are in connection with one 
another (Klein and Smith : Atlas of Histology). THE LIVER AHD BILIARY APPARATUS. 
Division of a nucleus, as described by Kolliker, I have never been able to 
confirm. When two nuclei are placed in contact, there may be an appear- 
ance of division, but the actual process is not easy to see. 
Thin liver sections may be stained either in carmine fluid or 
hsematoxylon, and preserved in glycerine or balsam. 
The larger bile-ducts.—lf, for the sake of convenience, we 
imagine that the hepatic duct enters the liver to be distributed 
to its substance, we may describe it as giving off two primary 
branches at the transverse Assure, one passing to the right 
lobe, the other to the left. As these branches continue their 
course, following the subdivisions of the hepatic artery and 
portal vein, they also undergo successive divisions, and at 
length enter the interlobular canals. In this position their 
diameter varies between 0.02 and 0.03 mm. 
The primary branches do not, however, pass unchanged 
into the liver tissue. Thej7" ramify even before entering the 
gland, but suck vessels are distributed only to the under 
surface (Henle). Other biliary ducts, given off in the trans- 
verse fissure, form a network on the upper surface, as may be 
demonstrated by injecting the hepatic duct with carmine-gly- 
cerine. The branches of these networks then enter the liver- 
tissue and ramify throughout it, following the subdivisions of 
the hepatic artery and portal, vein. 
As the divisions of the hepatic duct diminish in size, the 
thickness of their walls undergoes proportionate diminution. 
The trunk of the hepatic duct comprises an internal layer 
measuring 0.15 mm. in thickness, and an external layer of 0.2 
—0.3 mm. Both of these coats are composed, according to 
Henle, of interlacing connective-tissue bundles, in which elas- 
tic fibres are freely intermixed. These ducts have an internal 
lining of cylindrical epithelium, which is 0.05 mm. in height. 
Even where the branches measure only 0.2 mm. in diameter 
they have cylindrical epithelium surrounded by a single layer 
of connective tissue longitudinally disposed, in which there 
are also muscle-corpuscles, distinguished by their long, rod- 
shaped nuclei (Heidenhain). The most minute biliary pas- 
sages consist of a structureless membrana propria, which is 
lined with flattened cylindrical epithelia. 
Glands of the ducts.—ln the trunk of the hepatic duct and 
its subdivisions, down to those branches of which the diameter 
is not less than 0.5 mm., the mucous membrane is provided 192 
MANUAL OF HISTOLOGY. 
with numerous irregular excavations, measuring 0.15—0.3 mm. 
in their long diameter. In this trunk there occur also a great 
number of pores or orifices, which, on examination, prove to 
be the mouths of the passages leading from simple and com- 
pound gland-like bodies, the so-called glands of the bile-ducts. 
The simple glands consist merely of single vesicles, or alveoli, 
with afferent passages, all of which are imbedded in the mu- 
cous membrane ; or of two or more vesicles with a single pas- 
sage. The compound glands are formed by the union of two 
or more simple ones, which have a common passage. They are 
quite large, and their expanded portions lie on the outer sur- 
face of the hepatic duct. When filled by injection with gela- 
tine they are visible to the naked eye. The passages pierce 
the wralls of the duct at an acute angle, pursuing a course 
within its wralls, nearly parallel to the duct itself ; the opening 
into the mucous membrane is therefore quite a distance from 
the gland-vesicles. According to Henle, these compound glands 
are not found in the larger branches of the hepatic duct, but 
they occur frequently in the network of bile-ducts situated 
in the transverse fissure. Allusion has already been made to 
them. The vesicles measure 0.04 mm. in diameter, and, like the 
excavations in the larger branches of the duct, are lined with a 
cylindrical epithelium, in no way differing from that of the 
duct itself; the afferent passages also possess the same kind 
of epithelium. 
Structures allied to these excavations and glands occur in 
small number in the bile-ducts1 which are found in the liga- 
mentum triangulare. and on the diaphragm, where they appear 
as villous prominences on the duct-walls. 
According to Theile, Weber, and others, these bile-dncts represent the last 
vestiges of an atrophied liver substance, the existence of which dates back to 
infancy, or perhaps to foetal life. 
The excavations in the larger branches are either simple 
diverticula of the internal walls, or the openings of lateral bile- 
ducts ; the punctate pores are the orifices of the outlet pas- 
sages of duct-glands. 
Capillary hile-ducts.—When the larger bile-ducts, by con- 
1 Yasa aberrantia of E. H, Weber. THE LIVER AHD BILIARY APPARATUS. 
tinnons subdivision, have at length reached the interlobular 
canals, in conjunction with the branches of the portal vein and 
hepgtic artery, they send capillary branches within the sub- 
stance of the lobule, and thus form an intralobular network. 
These capillary ducts are of extreme delicacy, measuring only 
from 0.001 to 0.0012 mm. 
In order to demonstrate them fully they should be filled by 
natural injection. The substance to be employed for this pur- 
pose is a solution of pure indigo-carmine. The animal serving 
for injection (rabbit or dog) should be secured in the manner 
described in the chapter on the Kidney, where all the neces- 
sary manipulations are fully detailed. The best results are 
obtained by injecting a cold, saturated solution of indigo- 
carmine into the external jugular vein, directing the stream 
toward the periphery (brain) ; 5 or 10 ctgms. are to be injected 
at intervals of thirty to forty minutes, and the injection con- 
tinued until from 25 to 50 ctgms. have been used, the amount 
varying according to the size of the animal. It takes a longer 
time for the elimination of indigo-carmine through the capillary 
bile-ducts than for the same process by way of the renal tubules, 
and a larger amount of solution will therefore have to be em- 
ployed. As soon as large quantities of the indigo solution have 
been injected into the jugular vein, the animal becomes uncon- 
scious and there is a decrease of temperature; hence, it should 
be covered over with layers of cotton-batting. After a variable 
time (three to twelve hours) the animal is killed in the follow- 
ing manner : The abdomen is opened and the canula of a large 
syringe filled with absolute alcohol secured in the lumen of the 
portal vein; the inferior vena cava is then cut across above the 
entrance of the hepatic vein, and the piston of the syringe 
pushed home. The liver, which before was of a uniform blue 
color, now presents a marbled appearance, not unlike that of 
malachite. 
Or, the portal vein may be injected with the writer’s carmine- 
glycerine, the vena cava having been divided as above. In 
either case the liver is to be removed at once and placed in a 
vessel containing absolute alcohol, and while immersed in that 
fluid cut into small fragments. Sections may then be made in 
a few hours. 
The arrangement of the bile-capillaries differs in different 
animals. In the rabbit, for instance, they lie between the ad- 194 
MANUAL OF HISTOLOGY. 
Joining surfaces of two contiguous cells, and rarely in tlie 
canals formed by the edges of three or more cells (Hering!). So 
that while the blood-capillaries occupy the canals previously 
described, the bile-capillaries form an independent network be- 
tween the boundary surfaces of the liver-cells (Figs. 84 and 85). 
In cross sections they may be seen, appearing as small, circular 
Pig 84. Fig. SB, 
Pigs. 84 and 85.—Injected liver of rabbit. The narrow, reticulated bile-capillaries are shaded with 
longitudinal, the broader blood-capillaries with transverse lines. Within the boundary line or septum of 
two contiguous cells the cross-section of a bile-capillary is seen as a dark spot or point. The liver cells 
contain one or two nuclei. In Pig. 84, the bile-capillaries are slightly distended by the artificial injec- 
tion ; in Fig. 85, markedly so. Hering. 
openings between the cells, while in longitudinal sections they 
present a linear arrangement (Figs. 85 and 86). In the dog 
this arrangement is the same, only here the bile-capillaries 
occur more frequently in the canals formed by the edges of the 
liver cells. 
According to Hering, both in rabbits’ and dogs’ livers the blood-capillaries 
are separated from the bile-capillaries by the intervention of at least one liver- 
cell. Livers in which the bile-capillaries have been injected by the natural 
method with indigo-carmine do not always demonstrate this. And here it may 
be remarked, that in artificial or forced injections of the bile-capillaries they 
are always distended beyond their natural diameters.2 
1 Hering: Ueberdenßau derWirbelthierleber, and article on Liver in Strieker’s 
Manual. 
2 Compare Figs. 84 and 85, after Hering. Even in Fig. 84 the bile-capillaries are 
larger than they ought to be. In an article on the liver by Dr. W. G Davis, in the 
Amer. Jour. Med. Sci,, Yol. LXXVIIL, the distention of the capillaries is excessive. THE LIVER AND BILIARY APPARATUS. 
By conjoined natural injection of the bile-capillaries and 
artificial injection of the portal system with carmine-glycerine 
by the methods above detailed, very gratifying results are ob- 
tained. Care must be taken, 
however, not to use too much 
force during the process of in- 
jection, and only such por- 
tions of the liver should be 
chosen for sections as show, 
by their red color, a perfect 
filling of the portal branches. 
While the elimination of 
the indigo-carmine is taking 
place within the liver of the 
living animal, the bile-capilla- 
ries probably contain the salt 
in a soluble form. The addi- 
tion of absolute alcohol at 
once precipitates this color- 
ing reagent in the form of 
exceedingly fine stellate crys- 
tals, or as finely granular mat- 
ter, which may in some meas- 
ure account for the angular 
character of the biliary capil- 
laries, as seen in such specimens. Gentle curves, such as are 
represented in Fig, 85, never appear. The constringing action 
of the alcohol on the liver-cells has unquestionably some effect, 
and therefore modifies the normal appearance. 
Fig. 86.—Liver of a three-months’ child, hard- 
ened in chromic acid. The capillaries are filled with 
red blood-corpuscles (indicated by colorless rings) and 
a few leucocytes. The cross section of a bile-capillary 
is shown within the boundary line of any two con- 
tiguous cells. A similar cross section is shown in 
the canal formed by three adjoining liver-cells. 
Hering. 
Natural injections further show the great preponderance of 
the biliary- over the blood-capillaries. In the liver of a dog, 
for instance, each liver-cell seems suspended within two or 
three (rarely four) bile-capillaries, and where the latter are 
One need only compare Fig1. 3 in Davis’s article with Fig. 84 of Bering’s, which, by 
the way, is a good illustration. 
The first to describe the intralobular network of bile-capillaries were Andrejevic 
(Ueber der feineren Bau der Leber. Wiener Sitzungsbericht, 1861) and MacGillavry j 
(Zur Anat. d. Leber. Wiener Sitzungsbericht, 1864). Chronszewski was the first to 
inject the bile-capillaries by natural injection (Virchow’s Archiv, Bd. 35). MacGillavry 
Chronszewski, Budge, and others, described the bile-capillaries as possessing true 
walls. 196 
MANUAL OF HISTOLOGY. 
joined together the calibre of the capillary is markedly in- 
creased. Sections made parallel to the external surface of the 
liver, immediately under the capsule, generally cut the central 
vein transversely, and such sec- 
tions show that the bile-capillaries 
possess a somewhat radial course 
(Fig. 87). Human livers can rarely 
be obtained in a fresh state, and 
examinations of their bile-capil- 
laries are therefore attended with 
difficulty. 
Do ike hue-cap lllarles possess 
walls of their own f—This ques- 
tion must be answered in the 
affirmative. In specimens where 
the bile-capillaries have been in- 
jected by the natural method, 
cross sections of such capillaries 
will demonstrate, with high pow- 
ers, that there is a dot of blue indigo-carmine surrounded by 
a distinct circle which is perfectly transparent and in marked 
contrast to the somewhat yellowish color of the adjoining 
liver-cells. (See Fig. 88.) It is more difficult to see this in 
sections which cut the capillaries in their longitudinal diam- 
eters, but where two or more capil- 
laries unite this halo is again seen. 
That this appearance is due to the pres- 
ence of a true wall seems clear, but all 
doubts will be dispelled by watching 
the diffusion which takes place in such 
a section on the addition of a few drops 
of water under the cover glass. The 
indigo-carmine becomes dissolved in 
the water, forming a deep blue liquid 
which stains the surrounding cells and 
vessels of a uniform color. While 
watching a bile-capillary during the 
progress of this action it appears to 
stand out more prominently than before, and its walls become 
more distinct. In a few moments the cells will have become 
swollen by the imbibition of water, and the picture gradually 
Fig. 87.—Capillary bile-ducts of a rabbit, 
distended by artificial injection : 1, a portion 
of a lobule ; a, central vein ; ft. 6, interlobular 
veins ;c, c, bile-ducts; d, d, blood-capillaries; 
e, e, bile-capillaries. 
Fig. 88.—Liver of the dog. Nat- 
ural injection of bile - capillaries, 
showing double contour of the capil- 
laries, which are only partly tilled 
with injection. Cross sections of 
the capillaries show a dot of indigo- 
carmine surrounded by a distinct 
halo. The woodcut does not show 
this satisfactorily. In the specimen 
the lines corresponding to the walls 
of the capillaries are of the utmost 
delicacy. Magnified 450 diam. THE LIVER AXD BILIARY APPARATUS. 
197 
fades, until at length it would be difficult to even locate the 
original seat of the capillary. I have verified this over and 
over again. The capillary walls seem to be structureless; at 
least with a power of 1,400 diameters I have been unable to 
detect any structure. The membrana propria of the inter- 
lobular bile-ducts is continued on to the capillaries within the 
lobule. 
Hering, Henle, and others do not believe that the bile-capillaries possess 
walls of their own, but suppose them to be contained within the boundary 
surface of the liver-cells, the latter taking the place of the epithelium of the 
interlobular bile-ducts. Henle further quotes Schweigger-Seidel (in the Archiv 
far path. Anal, und Phys., XXYIL, 505, 1863), who injected the bile-capillaries 
with faintly colored gelatine, and showed that by warming the slide the gela- 
tine dissolved without leaving any residue whatever. From what has been 
said of artificial injections, and recognizing the extreme delicacy of the bile-cap- 
illaries, it is not surprising that this result was obtained after injecting a warm 
solution of gelatine into the capillaries. The walls of these capillaries are 
homogeneous and exceedingly delicate, so that they are destroyed by a mod- 
erate degree of heat. Very soon after death they undergo a sort of liquefac- 
tion, and what was before a vessel with true walls is now an open channel, 
through which an artificial fluid can be made to force its way. 
At first the elimination of the indigo-carmine takes place 
in the bile-capillaries on the external border of the lobule, 
and somewhat later the capillaries about the central vein be- 
come filled. Neither the protoplasm of the liver-cells nor their 
nuclei ever become stained with the blue solution during the 
process of elimination ; such coloring would be the result of 
post-mortem diffusion. But the cylindrical epithelium of the 
glands is colored blue, and indubitably these glands excrete 
the indigo-carmine, as do the cells of the convoluted tubules of 
the kidney. Whether they secrete any substance during life, 
or what that substance may be, has not yet been determined. 
Theile, Kolliker, and Kiernan suppose tlxat these glands secrete a mucous 
substance which becomes mixed with the bile. Henle regards these glands 
and excavations as reservoirs which are occasionally filled with bile. From 
what has been said above it would appear that the cylindrical epithelium of 
the glands eliminates the indigo-carmine, and hence we may suppose that 
they secrete some fluid or substance during life. 
The gall-bladder.—The walls of the gall-bladder are about 198 
MANUAL OF HISTOLOGY. 
2 mm. thick, and are composed of three coats:1 an internal, 
mucous and muscular; a middle, of connective tissue; and 
an external, the serous, The internal coat, 0.4 to 0.5 mm. 
thick, is composed of alternating layers of connective tissue 
and smooth muscle fibres, the most internal being a layer of 
connective tissue which contains a fine meshed capillary net- 
work. The connective tissue is dense and the muscle fibres are 
arranged in the form of interlacing bands. The internal sur- 
face is lined by a layer of cylindrical cells bearing a thickened, 
striated edge, and the surface is traversed by a network of 
small intersecting ridges, forming, as it were, a sort of lattice- 
work. The middle coat, 0.6 to 1 mm. thick, is formed of con- 
nective tissue, the meshes of which are wider on the internal 
than at the external surface. This coat contains the larger 
vessels and nerves. The external, or serous coat is thin, and 
consists of a layer of dense connective tissue and peritoneum. 
A few mucous glands2 are found scattered here and there in 
the walls of the gall-bladder. Sections from this organ, hard- 
ened in alcohol, may be stained with the carmine or picro-car- 
mine solution and mounted in glycerine or balsam. 
The cystic and common ducts resemble in structure the 
hepatic duct. The inner surface of the former is thrown into 
crescentic ridges, and in the region of the neck of the gall- 
bladder the connective tissue of the internal coat shows a 
circular arrangement. The ducts contain no muscle fibres. 
The lymph-vessels.—These may be divided into a series 
of superficial and deep channels. The former are situated in 
the capsule of the liver and form a capillary reticulum with 
small meshes, the larger branches of which accompany the 
arteries in pairs and communicate with each other by trans- 
verse anastomoses. They are found in Glisson’s capsule, and 
they also form a network somewhat larger meshed than the 
preceding. They accompany the hepatic artery and portal 
vein and their branches into the interior of the liver, and form 
anastomoses with the superficial lymph-vessels. The lymph- 
canals may easily be injected with colored material (carmine- 
glycerine) by filling a large hypodermic syringe with the liquid 
and injecting one of the larger lymph-vessels in the hilus of 
1 Henle : Eingeweidelehre. 
2Luschka: Virchow’s Archiv, 1857, and Zeitschr. f. rat. Med., 1858. BIBLIOGRAPHY. 
the liver. The syringe may be refilled three or four times 
without removing the canula, and the injection must be made 
in the direction of the normal lymph-current. In this way 
the colored licjuid will flow backward into the smaller vessels. 
During the injection of the larger branches their proximal ends 
should be secured by clamps or ligatures. 
The nerves of the liver enter the organ at the hilus and fol- 
low the course of the vessels. They are composed mostly of 
non-medullated elements, a few medullated fibres being found 
in the larger branches. They cannot be traced into the lobules. 
BIBLIOGRAPHY. 
Kiernan. Anat. and Phys. of the Liver. Philos. Trans. 1833. 
Lambron. Archiv. gen. 1841. 
Krukenberg. Midler’s Archiv. 1843. 
Weber, E. H. Muller’s Archiv. 1843. Program, col. fasc., 11. Lips., 1851. 
Tiieile. Wagner’s Handworterb. Bd. 11. 1844. 
Retzius. Muller’s Archiv. 1849. 
Wedl. Sitzuugsber. d. Wiener Akad. 1850. 
Rainey. Quart. Jour. Microsc. Sc. Yol. I. 1853. 
Gerlacii. Gewebelehre. 1854. 
Beale. Philos. Trans. 1855. Anat. of the Liver. 1856. Archives of Med. Yols. 
I. and 11. 
Yirchow. Virchow’s Archiv. Bd. XL 1857. 
Luschka. Henle u. Pfeuffer’s Zeitsch. Bd. IV. 1858. 
Budge. Reichert u. Du Bois-Reymond’s Archiv. 1859. 
His. Zeitschft. f. wiss. Zoologie. Bd. X. 1860. 
Wagner, E. Archiv d. Heilkunde. 1860. Oester. Zeitschrft. f. prak. Heilkunde, 
1861. 
Ebertii. Zeitschrft. f. wiss. Zoologie, 1860. Med. Centralbl. 1866. Virchow’s 
Archiv. 1867. Schultze’s Archiv f. mik. Anat. Bd. 111. 
Andrejeyic. Sitzungsber. d. Wiener Akad. 1861. 
Riess. Reichert u. Du Bois-Reymond’s Archiv. 1863. 
Sciiweigger-Seidel. Reichert u. Du Bois-Reymond’s Archiv. 1863. 
MacGillayry. Sitzungsber. der Wiener Akad. 1864. 
Irminger. Zeitschft. f. wiss. Zoologie. Bd. XVI. 1866. 
Chronszewski. Virchow’s Archiv. Bd. XXXV. 1866. 
Hering. Sitzungsber. d. Wiener Akad. 1866. Strieker’s Handbuch. Bd. I. 
1871. 
Kolliker. Handbuch d. Gewebelehre. 1867. 
Von Btesiadecki. Sitzungsber. d. Wiener Akad. 1867. 
Heideniiain. Studien aus d. phys. Instituts z. Breslau. Heft IV. 1868. 
Kisselew. Med. Centralbl, 1869. 200 
MANUAL OF HISTOLOGY. 
Pelugee. Pfliiger’s Archiv. Bd. 11. 1869. u. IV. 1871. 
Henle. Eingeweidelehre. 1873. 
Legros. Jour, de I’anat. et de la phys. 1874. 
Cohnheim u. Bitten. Virchow's Archiv. Bd. LXVL 1876. 
Bwald u. Ktjehne. Yerhand. Naturhist. med. Yereins zu Heidelberg. 1 Bd. 5 
Hft. 1876. 
Kolatschewsky. Schultze’s Archiv. Bd. XIII. 1876. 
Turner. Journ. of Anat. and Phys. Vol. XI. 1877. 
Wendt. Med. Oentralblatt. No. 15. 1878. 
Davis. Amer. Jour. Med. Sc. Vol. LXXVIII. 1879. 
Fritscii. Archiv. fur Anat. und Phys. Phys. Abtheil. 1879. 
Klein and Smith. Atlas of Histology. Part X. 1879—1881. CHAPTER XIV. 
THE KIDNEY. 
ABRAHAM MAYER, M.D. 
Late Curator of the Manhattan Eye and Ear Hospital, New York City. 
General plan of structure,—The glandular substance of the 
kidney is divided into two parts, an external or convex por- 
tion, called the cortical substance, or cortex, and an internal 
or concave portion, the medullary substance, or medulla. 
This division can be readily seen by cutting a kidney into two 
equal parts in the line of its long diameter. An intermediate 
zone, which separates the cortical from the medullary sub- 
stance, is called the boundary layer of the kidney. The whole 
organ is enveloped in a fibrous membrane, the capsule. 
The medullary substance contains the pyramids of the kid- 
ney, and is therefore also called the pyramidal portion. The 
apex of each pyramid, the papilla, projects into a special arm 
of the renal pelvis, viz., a calyx; the base or expanded por- 
tion is directed toward the cortical substance, and sends pro- 
longations into the latter. 
An examination of the cortical substance shows it to be 
composed of two distinct varieties of tissue, running parallel 
to one another toward the free surface. One has a fibrous ap- 
pearance, and is composed of cylindrical cords. It is a con- 
tinuation of the pyramids. These pyramidal prolongations 1 
(Henle) are also called medullary rays (Fig. 89). The other 
portion, situated between the prolongations, is a granular-look- 
ing material, called the cortical substance proper, or labyrinth 
of Ludwig.2 The latter contains numerous small bodies, 
which are of a distinctly red color when there is a large 
1 Ludwig und Zawarykin ; Zeitschrft. far rat. Med., 1863. They are also called 
the prolongations of Ferrein. 
2 Ludwig : Strieker’s Manual, p. 461. 202 
MANUAL OF HISTOLOGY. 
amount of blood in the kidney ; they are the Malpighian 
bodies, or glomeruli (Fig. 89, E). 
The boundary layer lis characterized by numeroas blood- 
vessels, some of which unite to form an arcade (Fig. 89, C), 
which is parallel to the convex surface of the kidney, and from 
which branches are given off to the cortical substance proper. 
The renal artery, before it enters the 
hilum of the kidney, divides into 
branches, which pierce the medulla 
between the pyramids and ascend 
toward the cortical substance until 
they reach the boundary layer. Here 
they divide obliquely or at right 
angles to give off smaller branches, 
which have the direction and arched 
ppearance above referred to (Fig. 
89, C). These arched vessels then 
send off the branches already men- 
tioned, which traversing the centres 
of the cortical substance proper, at 
right angles to the parent stem (Fig. 
89, D), extend almost to the capsule 
of the kidney. On their way they in 
turn give off smaller twigs, each of 
which bears a glomerulus upon its 
extremity (Fig. 89, E). In this way 
there is an alternate arrangement of 
pyramidal prolongation and cortical 
substance proper (Fig. 90). Though 
the pyramidal prolongations almost 
reach the capsule of the kidney, 
they never quite touch it, being sep- 
arated by the interposition of some cortical substance proper 
(Fig. 89). 
Fig. 89. Human kidney. Vertical 
section through cortical and medullary 
substances: A, branch of renal artery ; 
B, vein, immediately beneath former, but 
hardly visible in the figure; C, arched 
arterial branches in the boundary layer; 
X), artery of the cortical substance proper; 
E, Malpighian bodies or glomeruli; F, 
medullary rays or pyramidal prolonga- 
tions ; G, vessels of the medulla, the vasa 
recta, x 10. 
Specimens for study should be made from a fresh kidney, 
in which the renal artery has been injected with carmine-gela- 
tine, the whole organ having been subsequently immersed in 
alcohol of 50 per cent, strength. When in that fluid it is to be 
divided into four or more parts, allowed to remain therein for 
1 Henle; Grenzschicht, Eingeweidelehre. THE KIDNEY. 
twenty-four 1 lours, afterward transferred to stronger alcoliol, 
then to absolute alcoliol, and finally mounted in dammar or 
balsam. Vertical sections show the arrangement represented 
in Figs. 89 and 90 ; transverse sections, the appearance of 
Fig. 92. 
The substance of the kidney is composed of secreting and 
collecting tubules, vessels, and a stroma, which fills the inter- 
Fig. 90.—Human kidney. Vertical section through cortical portion ; A, pyramidal prolongation ; B, 
cortical substance proper; C, artery; D, glomerulus, x (il. 
spaces between the tubules, and is more abundant in the med- 
ullary than in the cortical substance. In human adults this 
connective material is found in small quantity and is a sort of 
colloid substance. In the lower animals it is more abundant, 
and assumes the character of real connective tissue. In young 
infants there is said to be a greater proportionate amount of 
this tissue than in subsequent life. 
The renal tubules.—The tubules are found both in the corti- 204 
MANUAL OF HISTOLOGY. 
cal and medullary substances ; they are of different diameters 
and pursue either a straight or tortuous course. Some have a 
basement membrane (;membrana or tunica propria), on which 
the epithelium rests; others appear to have none. The tu- 
bules are clothed with epithelium of different varieties. Speci- 
mens should be made from a kidney that has lain for twenty- 
four hours in a 5 per cent, solution of chromic acid. A small 
Pig. 91.—Schematic representation of the kidney: A, medulla; B, boundary layer; C, cortical por- 
tion ; a, renal artery ; b, renal vein; c, artery penetrating cortex; D, capsule enclosing glomerulus ; B, 
capillaries; P, convoluted tubules of first order; G-, looped tubule, descending branch ; H, looped tubule, 
ascending branch; I, convoluted tubule of second order; J, collecting tubule; K, vasa recta. 
piece of the gland is to be placed on a slide, and a drop of glycer- 
ine added; the tubules may be isolated by teasing with needles. 
In Fig. 91 there is a schematic representation of the vascular 
distribution and course of the tubules in one of the pyramids. 
Each tubule takes its origin in an expansion that surrounds 
the glomerulus, and is called Bowmari sor Muller’s capsule.l 
1 Muller, in 1830, described the capsules, but regarded them as vesicles which had 
no connection whatever with the nriniferous tubules. Bowman, in Philosoph. Trans- 
act. , 1843. THE KIDNEY. 
It is round or elliptical in shape, and has a diameter of about 
0.2 mm. Where the capsule empties its contents into the 
tubule, there is a slight constriction known as the neck; it is 
very distinct in some of the lower animals. The canal then en- 
larges and begins to pursue a tortuous course in the cortical 
substance ;it is now called a convoluted tube1 (Fig. 91, F). It 
next undergoes sudden diminution in size and passes straight 
through the medulla until, at a variable point, it bends upon 
itself, forming a loop; then, ascending, it increases in calibre, and 
in the cortical substance becomes convoluted for the second time. 
Those canals that are nearest the glomeruli are called convo- 
luted tubules of the first order, the others convoluted tubules 
of the second order. Between these two are the looped tubules 
of Henle, just described, each being divided into a descending 
and ascending branch (Fig. 91, G and H). The convoluted 
tubules of the second order terminate by emptying into tubules 
of greater diameter, called collecting tubules,2 which descend 
through the cortical and medullary substances, and, receiving 
other collecting tubules on the way, finally empty into the 
pelvis of the kidney (Fig. 91, J). 
At the base of each pyramid there are a vast number of col- 
lecting tubules, but as they successively empty into larger 
collecting tubes, the area they occupy is thereby diminished ; 
at the apex of the papillae, where they ultimately discharge 
the urine into the pelvis of the kidneys, there are only about 
twenty in number. This gradual coalescence of the tubes gives 
to the pyramids a conical shape, but the breadth of the base is 
also partly due to the presence of the looped tubules which 
pass down into the pyramids for a varying depth. 
The larger collecting tubules may be readily injected with 
Beale’s blue fluid 3 or carmine-gelatine, either directly or from 
the ureters ; it will be found, however, that the injection will 
seldom extend beyond the looped tubules, owing to the small 
diameter of the descending branches. 
1 Tubulus contortus. 2 Straight tubules of Bellini. 
3 Glycerine, pure, 2 oz. ; tr. perchloride iron, 10 drops ; ferrocyan. potassium, 3 
grains ; strong hydrochl. acid, 8 drops; water, 1 oz. Mix the tincture of iron with 
one ounce of the glycerine; and the ferrocyanide of potassium, first dissolved in a little 
water, with the other ounce ; mix gradually, and shake during admixture ; add the 
iron to the ferrocyanide; lastly, add the water and hydrochloric acid. Beale : 
Microscope, p. 87. 206 
MANUAL OF HISTOLOGY. 
Bowman’s capsule is composed of a structureless basement- 
membrane surrounding each glomerulus. Upon the inner sur- 
face of these capsules is a continuous layer of flat, epithelioid 
cells,1 which are continued over the glomerulus itself.2 Occa- 
sionally an epithelioid cell may be seen between the vessels of 
the coil composing the glomerulus. 
Each capsule is pierced by two vessels, called, respectively, 
afferent and efferent. The former enters the capsule and forms 
Fig. 93.—Human kidney. Transverse section of cortical portion, showing the alternating arrangement 
of pyramidal ray and cortical substance proper : A, A, pyramidal rays ; B, convoluted tubule ; 0, glom- 
erulus ; D, D, arterial vessels, x 55. 
the glomerulus, while the latter makes its exit close to the en- 
trance of the former. The layer of epithelium above described 
passes over from the inner surface of the capsule on to the 
glomerulus about the points of entrance and exit just men- 
tioned. On the opposite side, the capsule becomes continuous 
with a convoluted tubule. To obtain specimens, the renal artery 
of a fresh kidney should be injected with blue gelatine and then 
placed in alcohol. Vertical and transverse sections of the cor- 
tical substance may tlien be made. They should be stained in 
carmine and examined in glycerine, or the artery may be in- 
jected with absolute alcohol and the sections stained as above. 
The epithelium of the tubules.—The basement-membranes 
of the convoluted tubules of the first order are in direct con- 
tinuation with the basement-membranes of the capsules. Their 
diameter averages 0.04 mm. The epithelium of these canals is 
1 Schweigger-Seidel; Die Nieren. Halle, 1865. Henle : Eingeweidelehre, p. 829. 
Heidenhain: Zur anat. d. Nieren, in Schultze’s Archiv, Bd. X., Hft. I. Mayer : His- 
tology of the Kidney. Dis. Inaug., 1876. Also Bowman, Johnson, Frerichs, etc. 
2 Gerlach, Heidenhain. THE KIDNEY. 
peculiar, and was first correctly described by Heidenhain. 
According to this writer, the greater part of the cell-protoplasm 
assumes the form of small, cylindrical bodies, the so-called 
rods of Heidenhain, giving the epithelium a stri- 
ated appearance (Fig. 93). 
To exhibit these appearances, the cortical sub- 
stance of a dog’s or rabbit’s kidney should be 
cut into small pieces and immersed for twenty- 
four hours or more in a 5 per cent, solution of 
the neutral chromate of ammonia. After this 
time has elapsed, a small piece of the gland is to 
be placed on a slide and a drop of glycerine 
added ; the specimen may then be teased and ex- 
amined. Portions of the convoluted tubules will 
be. found floating about in the glycerine, and 
should be closely scrutinized. By this mode of 
preparation, individual epithelioid corpuscles can- 
not be recognized; on the contrary, they seem 
to merge with one another. The tubule may be 
regarded as made up of rods transversely dis- 
posed, with nuclei embedded in a pulpy mass 
that appears to fill its lumen, the whole envel- 
oped by the membrana propria. The rods sur- 
round the nuclei, and are not all of the same length. They 
appear to be hollow, as shown by their sometimes containing 
fatty granules. Here and there in the specimen a separate 
corpuscle will present itself to the eye; in 
such instances the rods can readily be made 
out (Fig. 94, A). In the kidney of the rat 
these bodies may be isolated with little diffi- 
culty (Fig. 94, B). At one end the rods rest 
against the membrana propria, to which they 
are attached by a colloid material; their other 
extremity is lost in the protoplasm of the cap- 
sule, which latter lies internal to them and 
appears to have the character of a pulpy mass 
containing nuclei. In the dog, the nucleus of 
each cell is about midway between the lumen 
and the membrana propria. It is surrounded by rods (Fig. 
94, A). In the rat this is not the case (Fig. 94, B). Assuming 
that the rods begin at the membrana propria, they are directed 
Fig. 93.—Convo- 
luted tubule from 
the kidney of a dog. 
Neutral chromate of 
ammonia prepara- 
tion. The tubule 
normally appears 
darker than is rep- 
resented in the fig- 
ure. x 480. 
Fig. 94.—Isolated cells 
from the convoluted tu- 
bules exhibiting rod-like 
epithelium: A, kidney of 
dog; B, kidney of rat. 
x 450. 208 
MANUAL OU HISTOLOGY. 
toward the centre of the lumen of the tubule, and the distance 
between any two adjoining rods at the periphery is necessarily 
greater than at the centre. For the same reason, also, the rods 
are more distinctly defined in the former situation ; the micro- 
meter screw will have to be used in tracing them inward. 
Transverse sections of the cortical substance may be made 
by freezing small pieces which have been immersed in a solu- 
tion of the neutral chromate of ammonia. Such sections should 
be examined in glycerine, or, better, in a saturated solution of 
the chloride of potassium in glycerine.1 The radial direction 
of the rods is beautifully seen in such specimens (Fig. 95, C), 
Fig. 95.—Kidney of dog. Transverse section through the medullary portion, about midway between 
the apex and boundary layer. Neutral chromate of ammonia preparation : A, blood-vessel; B, looped 
tubule, descending portion; 0, looped tubule, ascending portion ; D, collecting tubule; E, connective 
tissue, x 800. 
and the individual cells are more clearly defined. Another 
method of exhibiting these rod epithelia is to inject the artery 
or vein of a fresh, bloodless kidney with a cold saturated solu- 
tion of the chloride of potassium, then, after placing the whole 
organ in alcohol, divide it in small pieces under that fluid. 
After a day or two sections may be made ; they then should be 
immersed for a short time in absolute alcohol and clarified by 
oil of turpentine. Such specimens show the epithelium to 
perfection and may be preserved for a considerable time. Per- 
manent specimens can be made by substituting resinous turpen- 
1 The glycerine should be heated in a porcelain evaporating-dish, the chloride of 
potassium added, and the whole mixture stirred for several minutes with a glass rod. 
The glycerine is ready for use after cooling. THE KIDNEY. 
tine1 for the common oil. The renal artery or vein may also 
be injected with absolute alcohol, and sections prepared as 
above. But the epithelium suffers in this way, for the alcohol 
causes the rods to shrink, and the colloid substance between 
the rods coagulates. Still, the striated appearance is seen near 
the membrana propria. Another fact which seems to have es- 
caped Heidenhain is that alcohol so injected causes the nuclei 
of the cells to recede toward the membrana propria by its 
action on the rods. 
• The action of water on the rods is peculiar. A fresh kidney 
must be used and a portion of the cortical substance placed on 
a slide, together with a drop of water; it is then to be teased 
with needles and immediately examined. At first the rods are 
not distinctly brought into view, but they soon appear with 
their contours sharply delineated. This appearance, however, 
does not last very long, for the epithelium soon imbibes water, 
swells, and then forms an indistinct mass. 
In the neck of the convoluted tubules of the frog, coluber, 
etc., the epithelium is ciliated. In the frog the cilia have great 
length, but the convoluted tubules do not have the rod epithe- 
lium. In the dog, cat, rabbit, etc., the rod epithelium begins 
at the neck of the tubule and is continued as far as the loops. 
The convoluted tubules of the first order, after ramifying 
in the cortical substance, become continuous with the looped 
tubules of Henle, as already described.2 The change takes 
place in the vicinity of the boundary layer. 
The looped tubules.—The looped tubules traverse the 
medulla for a greater or lesser distance. A few almost reach 
the apices of the pyramids ; others extend but a short distance 
below the boundary layer, while a third class occupies an inter- 
mediate position. Good specimens are obtained by macerating 
vertical sections of the medulla in a solution of caustic potassa 
(i to 1 per cent.). The potassa destroys the epithelium, the 
stroma, and the blood-corpuscles, but leaves the basement- 
1 Resinous turpentine is prepared as follows: some common oil of turpentine is 
poured upon a deep plate, so as to form a thin layer, and a piece of fine muslin is 
snugly fastened over it to keep out the dust. The liquid is now exposed to the ac- 
tion of the air. In a few days, if the weather he warm, or a week or more, if the 
weather be cold, the turpentine will have become thick, yellow, and resinous, and is 
now no longer transparent. Resinous turpentine, prepared in this way, forms one of 
the best preserving agents. Its use will be spoken of further on. 
2 Henle: Eingeweidel., 2te Aufl., p. 316. 210 
MANUAL OF HISTOLOGY. 
membrane perfectly intact. A fresh kidney is necessary, and 
one slightly infiltrated with fat makes the best specimens. 
Another method is to embed the kidney of a dog or rabbit 
in powdered chlorate of potassa, adding enough dilute nitric 
or hydrochloric acid to cover the crystals. After some hours 
the connective tissue in the gland will have been destroyed. 
Portions of the medulla should then be placed upon a slide 
with a drop of glycerine and teased slightly, A great many 
of the loops are broken in this way, to be sure, but still some 
will be seen. By this method the epithelium of the narrow 
branch is not destroyed. 
The epithelium of the looped tubules.—The descending 
branch of the loop is small in diameter (0.02 mm.) and pos- 
sesses a peculiar distinctive epithelium. The corpuscles are 
flat, have prominent nuclei, and rest against the membrana 
propria. The disproportionate size of the nuclei causes the 
corpuscle to project into the lumen. But these prominences 
do not obstruct the passage, 
for each one corresponds to 
the space between two on 
the opposite side of the tu- 
bule, so that there is no bar 
to the urine, but the passage is made more or less spiral (Fig. 
96). The corpuscles are of a light color. Specimens should 
be made from a gland that has been macerated in a 5 per cent, 
solution of the neutral chromate of ammonia; they should 
be examined in glycerine. The length of the narrow portion 
of the loop is variable in man, the pig, and horse. 
Fig. 96.—Kidney of dog. Descending portion of 
Henle’s looped tubule. 
The second portion of the looped tubule is wider and its 
epithelium peculiar. In man both the loop and ascending 
branch are wide, usually ; especially is this the case with loops 
high up in the medulla; in the rabbit it is the ascending 
branch only that has this property. Generally speaking, the 
length of the broader branch of the loop exceeds that of the 
narrow portion. The diameter of the broad portion averages 
0.04 mm. The epithelium has the same character as that in 
the convoluted tubules ;it is striated and possesses rods,1 It 
is not precisely similar, however. The width of the individual 
cells is not so great as in the former, and hence the lumen in 
1 Heidenhain ; loc. cit. Henle : loc. cit., p. 317. THE KIDNEY. 
tills portion of the loop is greater than in the convoluted tu- 
bules. Specimens prepared with the neutral chromate of am- 
monia, as before detailed, give good results. Vertical sections 
may be made from a kidney macerated in the ammonia solu- 
tion and afterward treated with alcohol; or, better, from frozen 
specimens. 
The broader extremity of the looped tubule ascends through 
the medulla into the cortical substance and becomes continu- 
ous with a convoluted tubule of the second order (Fig. 91, i). 
These tubules, the intercalated portions,1 greatly resemble con- 
voluted tubules of the first order, as already mentioned. Spe- 
cimens should be prepared in the same way as those of the 
latter. The convoluted tubules of the second order, after rami- 
fying in the cortical substance, terminate by emptying into the 
collecting tubules (Fig. 91, J). 
The collecting tubules and, their epithelium.—The collecting 
tubules2 possess cylindrical epithelia, the bases of which are 
irregular and present point-like prolongations3 (Fig. 97), which 
interdigitate with one another. The nuclei in 
the smaller collecting tubules are large and 
very prominent, but the protoplasm which sur- 
rounds them is not very abundant. The base- 
ment membrane is comparatively thick and 
exhibits a double contour. The smaller col- 
lecting tubules are situated in the cortical sub- 
stance, a little distance below the capsule. 
Their diameter ranges between 0.04 and 0.06 
mm. The small tubules unite to form larger 
ones, and these again to form tubules of still 
larger diameter. The irregular appearance at 
the bases of the epithelia is the same in the 
larger trunks as in the smaller branches ; in the former, how- 
ever, the cells are larger, and the protoplasm more voluminous 
than in the latter. The nuclei have about the same size in 
each (Fig. 98). The basement-membrane diminishes in impor- 
tance in an inverse ratio with the size of the collecting tubules. 
In the smaller ones it is prominent and possesses a double con- 
Fig. 97.—Kidney of 
dog. Isolated cells of 
two collecting tubules, 
showing irregular base 
and point-like prolonga- 
tions : a, from smallest 
collecting tubule; 6, 
from one near boundary 
layer, x 450. 
1 Schweigger-Seidel: Schaltstiicke; Roth : Yerbindungscanale (connecting tu- 
bules). 
2 Open tubules of Henle. Zur Anat. der Niere. Gottingen, 1863. 
3 Heidenhain : loc. cit. 212 
MANUAL OF HISTOLOGY. 
tour; in those of intermediate size it is thin, and has but a 
single contour ; the largest tubes possess no basement-mem- 
brane whatever. In the latter the great cylindrical cells are 
held together by the prolongations above mentioned and a 
colloid substance. The diameter of the largest tubules at the 
apices of the pyramids is 0.2 to 0.3 mm., after the first division 
0.1 to 0.2 mm., the smallest being about 0.06 
mm. The height of the epithelium in the 
largest tubules is between 0.02 and 0.04 mm. ; 
in those at the boundary layer about 0.015 
mm. Good specimens are obtained by im- 
mersing a fresh gland in dilute muriatic or 
nitric acid for a variable period (six to twenty- 
four hours), and examining in dilute gly- 
cerine. The collecting tubules1 should be 
injected from the ureter with blue or red gel- 
atine, and the whole organ immersed in alco- 
hol, until ready for cutting. Sections made 
parallel to the collecting tubules produce 
splendid specimens. The connection between 
the collecting and convoluted tubules of the 
human kidney cannot be shown by injection, 
for the colored fluid thrown in from the ure- 
ter rarely reaches the convoluted tubules of the first order. In 
the lower animals—fishes, frogs, etc.—however, if the ureter be 
injected under constant pressure the entire length of the urin- 
iferous tubules may be filled with the carmine, or, better, Berlin 
blue2 fluid. 
Fig. 98. Kidney of 
dog. Small collecting tu- 
bule above the boundary 
layer, x 450. 
1 In the pig Henle finds that two large collecting tubules begin at the apex of 
each pyramid, then run along the outer borders of the cortical substance proper, 
high up into the cortex, and there unite by forming a loop. Henle states that 
the convoluted tubules empty into these, or their divisions by intercalated portions, 
which be calls communicating tubules (VerbindungscandlcJien). Eingeweidel., p. 324. 
9 This has been done by Frey with fishes and amphibia; by Hiifner with birds, 
fishes, etc. ; by Gross with fishes and tritons, and by Hyrtl with some sorts of fishes. 
According to Seraphina Schachowa (Unters. ueber die Mere. Diss. Bern, 1876) the 
convoluted tubule of the first order is connected to Henle’s loop by a spiral tubule, 
while the ascending portion of the loop exhibits an expanded part immediately above 
the loop, and a spiral part, which latter becomes continuous with the ascending limb 
of the loop. Between the ascending part of the loop and the intercalated portion 
Schachowa describes a new tubule, which she calls the “irregular tubule.” 
The spiral tubule is lined with an epithelium which has a striated appearance in THE KIDNEY. 
The blood-vessels of the Iddney.—The renal artery and vein, 
before entering the hilum, divide and subdivide within the 
sinus of the kidney. Small branches, which are given off at 
the hilum, also supply the fibrous capsule of the gland. Veins 
accompany the arteries as far as the arches already referred to, 
But here a difference is to be noted. The arteries never anas- 
tomose, but form the straight vessels of the cortical substance 
proper, which again send off twigs to form the glomeruli. 
Pig. 99.—Kidney of pig. Injection of artery and vein. Vertical section at boundary layer: A, 
artery; B, vein ; 0, glomerulus; D, capillaries of the cortical portion; B, vasa recta formed from 
capillaries D. x 96. 
At the arches, however, the veins anastomose, and a branch 
accompanies the straight artery of the cortical substance proper 
(Fig. 99, B). The glomerulus is formed from the arterial twig 
above referred to (Fig. 89, D). This enters the capsule directly 
opposite to the point where the latter becomes continuous 
with a convoluted tubule, and divides into two or more 
its first portion. The expanded part of the ascending loop is lined with cells having 
very thick prominent rods, and whose lumen is exceedingly small. 
The irregular tubule has an angular, irregular outline, is of very varying diameter, 
in some portions two, three, or four times as broad as in other portions, a condition 
due to its peculiar lining epithelia, which are angular and present numerous pro- 
cesses ; the rods are exceedingly thick and prominent. 
As yet I have been unable to confirm Schachowa’s researches. 214 
MANUAL OF HISTOLOGY. 
branches which subdivide again and again (Fig. 100) to form 
loops or coils ; these latter unite again and form a vessel equal 
in size to the one which entered the capsule. The first is 
called, as already described, the affer- 
ent ; the second, the efferent vessel, 
and the glomerulus is formed by the 
division and reunion of the branches 
of these two vessels; the whole form- 
ing a rounded tuft within the capsule. 
The vessels of which a glomerulus is 
composed have the same diameter as 
small capillaries; their coats are struc- 
tureless and provided with elliptical 
nuclei. The efferent vessels are not veins ; on leaving the cap- 
sules they break up into capillaries, which anastomose freeiy 
with each other and surround the tubules of the cortex, form- 
ing, in this way, a network with circular meshes (Fig. 99, D). 
Fig. 100.—Glomerulus from kidney 
of pig. Ludwig. 
At the boundary layer the capillaries unite to form vessels 
which are two to three times larger than the original capillaries. 
These vessels take a straight course through the medulla to- 
ward the apices forming the so-called rasa recta1 (Figs. 99, E, 
and 89, G). The vessels immediately below the boundary layer 
are arranged in bundles at the side of the pyramidal prolonga- 
tions, and run parallel with them in that part of the medulla 
(Fig. 89). They give off branches in the medulla, and near the 
apices of the pyramids again form a capillary network which 
surrounds the collecting tubules. The returning vessels (veins) 
have about the same course, anastomose freely with each other, 
and into the venous arches at the boundary layer. 
Other veins are formed by the union of capillaries immediately 
underneath the capsule ; these have a stellate form,3 the centre 
of each star indicating the commencement of a vein. Such 
veins, passing downward through the cortex and receiving 
branches on the way, empty finally into the venous arches 
above referred to. The venous arches also give rise to vessels 
of larger calibre, which run parallel to and accompany the ar- 
teries of the medulla, and at last unite to form the renal vein. 
Injections of the kidney.—The kidney may be injected with 
gelatine either through the artery or vein. It is best accom- 
1 Bonders: Physiol., I. 
2 Vena Stellata, Yerheyen. THE KIDNEY. 
plislied by the artery, under constant pressure (mercury). 
Beale’s blue injecting fluid1 answers very well; the writer’s car- 
mine-glycerine fluid2 also acts exceedingly well, but it is very 
difficult to obtain a good double injection of artery and vein. 
I have found the most successful method to be the following : 
Take a fresh bloodless kidney (dog, pig) and inject the vein 
under constant pressure with the blue gelatine mass.3 Next 
place the kidney in iced water for a few minutes to harden the 
gelatine, and then attach to the artery a very small constant- 
pressure injecting apparatus, the receptacle for the injecting 
fluid containing the writer’s carmine fluid. After regulating the 
amount of pressure, the whole apparatus, with the kidney, is 
placed within the receiver of an air-pump and the air slowly 
exhausted. In this way the arteries become filled with fluid. 
Allow the gland to harden in alcohol and mount the sections 
in balsam or dammar. Kidneys in which the vein and artery 
have been injected may have the collecting tubules filled from 
the ureter with yellow injecting fluid, thus making a triple 
injection. Sections of kidney hardened in alcohol may be 
stained with borax-carmine, and afterward bleached in a di- 
lute hydrochloric acid (1 to 10) solution, or a concentrated one 
of oxalic acid. When the vessels of a kidney have been injected 
with blue gelatine, staining with carmine gives good results. 
Thiersch’s yellow injecting fluid is made as follows : Prepare a solution of 
bichromate of potassa, one part of the salt to eleven parts of water, and a solu- 
tion of nitrate of lead of the same strength. One part of the potassa solution 
is placed in a small basin and mixed with four parts of a concentrated solution 
of gelatine. Two parts of the lead solution are placed in another basin and 
mixed with four parts of jelly. These are to be slowly and thoroughly mixed 
together at a temperature of 75° to 90°, and then heated in a water-bath at a 
temperature of 212° for half an hour or more. Filter carefully through flannel 
(Beale : Microscope, p. 90). 
The kidney stroma.—In the cortical substance the stroma 
is reduced to a colloid material which binds the tubules to- 
gether. In the lower part of the medulla, in the fresh state, 
1 See page 205. 
* Carmine, 5 grammes ; glycerine (anhydrous), 50 grammes; add caustic potassa 
until the carmine is dissolved, and neutralize with pure, concentrated muriatic acid. 
8 Gelatine should be first immersed in water until it becomes softened and then 
gently heated until dissolved. Add soluble Berlin blue, or Beale’s blue fluid, until a 
good color is obtained. Inject while hot. 216 
MANUAL OF HISTOLOGY. 
the stroma is a colorless, transparent substance, which, aftei 
immersion for a variable time in a solution of chromate of po- 
tassa or ammonia, resolves itself into a thin fibrous reticulum, 
containing at regular intervals round or elliptical nuclei;1 
these, according to Schweigger-Seidel, belong to stellate or 
spindle-shaped corpuscles, which may be isolated by macera- 
tion in hydrochloric acid. The nuclei are only seen in the 
lower portion of the medulla ; the fibrous appearance of the 
stroma is retained some distance beyond this point. 
The nerves follow the course of the arteries of the kidney 
and seem to supply only those vessels. 
The lymphatics at the hilum are derived from the interior 
of the organ, and from a network of small lymph-branches 
situated between the bundles of fibres of the capsule. The 
latter communicate with lymph-canals in the interior of the 
organ.2 
The capsule of the kidney is a fibrous tissue, containing 
some few elastic filaments. It is divisible into two layers, an 
outer and an inner one. The former, about 0.1 to 0.2 mm. in 
thickness is continuous with the connective tissue which sur- 
rounds the blood-vessels at the hilum ; the latter, about 0.025 
mm. in thickness, terminates at the points where the papillm 
enter the calices. Immediately underneath the inner layer, is 
a large meshed reticulum of smooth muscle-fibres,3 some of 
which traverse the substance of the gland for a short distance. 
The calyx, at its Junction with the papilla, is covered with 
epithelium, which is continued on to the apex of the papilla ; 
it contains, in addition, muscle-fibres disposed at right angles 
to one another, and connective tissue. 
Natural injection of the tubules of the kidney by the 
sulphindigate of soda.*—The first to inject the kidney in this 
way was Chronsczewski;6 but his experiments were not very 
successful, at least so far as the kidney was concerned. Those 
of Heidenhain6 which have been confirmed by the writer,7 give 
1 Henle : loc. cit. 2 Ludwig, in Strieker’s Manual. 
3 Eberth: Med. Centralbl., No. 15, 1873. 
6 Chronsczewski, in Virchow’s Archiv, Bd. XXXI., p. 187; also Bd. XXXV., p. 
158. 
4 Commonly known in the laboratory and in commerce as indigo-carmine. 
6 Max Schultze’s Archiv, Bd. X., p. 1, and Pfliiger’s Archiv, Bd. IX., p. 1. 
7 Mayer ; Histol. of Kidney. Prize dissert., 1876. THE KIDNEY. 
the most satisfactory results. To insure this desirable end, it 
is necessary that the sulphindigate of soda be pure. 
O. Maschke, of Breslau, the apothecary who manufactures the pure sulphin- 
digate of soda for Prof. Heidenhain, writes to that author as follows : “ The 
indigo-sulphate of soda was prepared from the phoenicin-sulphate of soda. If 
the latter compound be heated for half to one hour, at a temperature of 60° to 
70° 0., with five or six times its volume of sulphuric acid of a specific gravity 
of 1,810, it resolves itself completely into indigo-disulphate of soda and 
indigo-monosulphate of soda (indigunterschwefelsaures Natron). I have 
chosen this mode of preparing the salt because the indigo-gelatine and indigo- 
brown can easily be separated from the phoenicin-sulphate of soda, without 
marked loss, and in this way I obtain a sufficiently pure substance for future 
use. An easier method of preparing the salt is the formula given by Crum 
and Berzelius. One part of best indigo in powder is gradually added to seven 
or eight parts of pure sulphuric acid, specific gravity 1,840, in a large vessel, 
and the two thoroughly mixed. After the liquid has ceased to froth, the 
vessel is covered with an animal membrane and put aside for three days, during 
which interval it is to be frequently shaken. To this solution thirty to forty 
volumes of water are added, and the whole carefully filtered. To the resulting 
clear solution as many parts by weight of crystallized carbonate of soda as 
there were of sulphuric acid, are added. Owing to the effervescence which 
now takes place, the vessel in which the mixture is prepared must be of large 
size. For this reason it is better to substitute the acetate of soda, or chloride 
of sodium, or simply sulphate of soda, for the formation and precipitation of 
the indigo-disulphate of soda takes place with any soda salt which does not 
decompose the indigo-disulphuric acid. The mixture is now filtered, and the 
precipitate dried over a water-bath. It is then pulverized and treated re- 
peatedly with absolute alcohol, which dissolves any indigo-monosulphate of 
soda, acetate of soda, or indigo-red, which may have remained.” In this way 
the indigo-carmine is obtained in a pure state. The crystals are copper-colored, 
but the salt is blue in the pulverized state. The indigo-carmine of commerce 
is an impure article and cannot be used for natural injection. 
For injection, a cold saturated solution of the sulphindigate 
of soda is used ; the salt may be dissolved in boiling distilled 
water, and the solution allowed to cool. A dog or rabbit 
answers for the purpose of injecting. The animal is properly 
fastened to a board, and the external or internal jugular vein 
dissected up and exposed. In either of these vessels a canula 
with stop-cock, previously filled with the indigo-carmine 
solution, is inserted. The injection into the jugular may be 
made downward or upward—the latter is preferable. A syr- 
inge, graduated in cubic centimetres and containing the sol- 
ution of indigo-carmine, is now attached to the canula, the 
stop-cock opened and a small quantity of the solution injected 218 
MANUAL OF HISTOLOGY. 
into the vein. Not more than 6 c.c. should be injected at one 
time. If the animal be a white rabbit, the result of the first 
injection shows itself in a few seconds, for the animal soon 
becomes quite blue. After five or ten minutes another 5 c.c. 
of the solution may be injected, and so on until 20 to 50 c.c. of 
indigo-carmine solution have been employed, the amount 
varying according to the size of the animal. 
The excretion of blue urine takes place soon after the first 
injection of indigo-carmine. As soon as a sufficient quantity 
lias been excreted the animal is killed in the following manner ; 
The abdomen is opened and the descending aorta looked for ; 
when found, the canula of a syringe, filled with absolute alcohol, 
is attached. The jugular vein is now cut across, and while 
the animal bleeds to death absolute alcohol is injected up the 
aorta or into the renal arteries. A safer and better way is to 
inject the renal artery at once with absolute alcohol; in either 
case the renal veins should be cut across. The kidney is at 
once removed, placed in absolute alcohol, and then divided 
into several pieces, to insure a rapid action of the spirit. 
While the indigo-carmine is being injected into the jugular 
vein, the animal should be wrapped up in flannel or cotton- 
batting so as to be kept warm. No air should be allowed to 
enter the vein, or the animal may die before the experiment is 
concluded. Injection of absolute alcohol through the renal 
artery should be accomplished before the animal has bled to 
death, or, at least, immediately afterward. When the kidney 
has been thoroughly hardened, vertical and transverse sections 
are to be made through the cortical and medullary substances, 
and examined in glycerine saturated in chloride of potassium ; 
or, better still, in resinous turpentine. 
If the injection of absolute alcohol be delayed, either through lack of skill in 
the experimenter, or any mishap, the indigo salt within the kidney becomes 
diffused over the entire organ by absorption of water from the contained ves- 
sels, and the whole kidney becomes of a uniform blue color. Such glands 
must be laid aside, for sections made therefrom, even after immersion in abso- 
lute alcohol, are worthless, and will only confuse the microscopist. The abso- 
lute alcohol of the shops is not always absolute, as is well known. It has a 
great affinity for water, and, in handling, rapidly absorbs moisture from the air. 
To make it absolute, I heat sulphate of copper (pure) at a low red-heat. This 
drives out the w7ater of crystallization, and changes the color from blue to 
white. Of this I mix a large spoonful or more, while still hot, with a pint of 
the so-called absolute alcohol, and tightly cork the vessel, which is then to be THE KIDXEY, 
shaken occasionally, but not used for a week or more. The affinity that water 
has for anhydrous sulphate of copper is greater than that of the alcohol, and 
the latter readily gives it up. As soon as the anhydrous sulphate regains its 
water of crystallization it assumes a blue color again. 
Everywhere in the sections it will be seen that the glomeruli 
or their capsules are entirely free from color, while all the 
tubules possessing the rod-epithelium have a more or less blue 
color, according to the quantity of indigo-carmine excreted. 
The lumina of the convoluted and other tubules are generally 
filled with the crystallized indigo-salt. In examining sections, 
it soon becomes evident that the convoluted tubules and that 
part of Henle’s loop which possesses the rod-epithelium, alone 
excrete the indigo-salt, while the other tubules merely contain 
it in their lumen, the salt having been washed down, as it were, 
from above by the water filtered through the capillaries of the 
glomeruli. 
Instead of using the sulphindigate of soda, Heidenhain, in his second series 
of experiments, substituted a solution of uric acid in caustic soda. The renal 
artery was injected with alcohol containing acetic acid. The result showed 
that urate of soda, like the indigo-salt, was excreted only by the tubules pos- 
sessing the rod-epithelium. The capsules were entirely free. The addition of 
acetic acid to the alcohol caused the uric acid to be precipitated in the shape 
of rhomboid crystals within the tubules. In this condition Heidenhain found 
them. The hypothesis set down by Bowman, years ago, that the tubules of 
the kidney excrete the solid constituents of the urine merely, while the glome- 
ruli serve as a filter for the fluid portion, is therefore correct. 
If the quantity of indigo solution injected into the jugular 
be small, and the animal killed soon after, the kidney being 
treated as above detailed, the microscopic sections exhibit 
the following appearance: glomerulus and capsule are not 
acted upon ; the narrower branch of the loop and the collect- 
ing tubules are free from any crystallized salt, and their epi- 
thelium clear. In the convoluted tubules and the broad part 
of the loop, the following phenomena may also be observed: 
their lumina are entirely free from any deposit of indigo-car- 
mine, though here and there the rod-epithelium is not stained. 
In the greater number it is colored of a light blue color. In some 
the rods and nuclei are uniformly stained ; in others the rods 
alone show the blue color, while the nuclei are not stained. 
This constitutes the first stage of the excretion of indigo-car- 220 
MANUAL OF HISTOLOGY. 
mine through the kidneys. If a larger quantity of indigo 
solution be injected, and the animal dealt with as above, the 
second stage of the excretion is seen. Here, again, the glome- 
ruli, the capsules, and the collecting-tubules are free from 
color, the rod-epithelium stained blue, and their nuclei dark 
blue (Fig, 101, F). In a few of the convoluted tubules and the 
ascending broad branches of the loop, crystals of indigo-salt 
Pig. 101.—Kidney of dog. Natural injection of secreting portion, artificial injection of artery, vein, 
and capillaries. Transverse section through cortical substance : A, afferent vessel, filled with injected 
material; B, efferent vessel, also filled with injection; B, glomerulus, injected and lying within its cap- 
sule: epithelium of latter distinctly seen: I), capillaries surrounding the convoluted tubules, and dis- 
tended with the injection; at this point four capillaries are seen to unite and form a vein: C, convo- 
luted tubule, filled with crystals of indigo-carmine; F, convoluted tubule, in which the nuclei have a 
dark color. The striations of Heidenhain are beautifully shown in the convoluted tubules, x 200. 
fill the lumina. So, also, in some of the descending narrow 
branches of the loop. In the third stage the rods are color- 
less, while their nuclei are still blue. Masses of the indigo- 
salt fill the lumina of the convoluted, looped, and collecting 
tubules; the glomeruli and their capsules are colorless. In 
the last stage, the salt is contained in the lumina of the col- 
lecting tubules only, all the rest of the gland being free from 
it, and consequently colorless. From the above it will be THE KIDNEY. 
seen that the rod-epithelinm alone excretes the indigo-salt, and 
it may be presumed, therefore, that the function of the glome- 
ruli is to act as a filter for the fluid portion of the urine. Thus 
the salt is washed from the convoluted into the collecting 
tubules, and thence into the pelvis of the kidney. The action 
of absolute alcohol on a solution of sulphindigate of soda is to 
precipitate that salt. It is this action within the kidney which 
fixes the dye, as above set forth. 
Beautiful specimens may also be obtained by various modi- 
fications of the above process. 
The following formulfe and results are given by Heidenhain: 
1. Rabbit or dog; section of spinal cord, injection of only 5 c.c. of the in- 
digo solution, the animal being killed after ten minutes. Result: pyramidal 
portion and boundary layer free from indigo-blue. In the cortical substance, 
some of the convoluted tubules are filled with the crystalline salt; in the 
greater number the epithelium is colored of a uniform blue, the nuclei possess- 
ing the same tint; the lumen is usually free. 
2. Same conditions as above, excepting that 20 or 25 c.c. of the solution 
is injected. Medulla free from indigo blue. In the cortex a great many of the 
tubules are filled with the pigment, while the epithelium is stained blue, the 
nuclei of a deep blue color. 
3. Same conditions as in 2, excepting that the animal is killed one hour 
after injection. Nuclei of the rod-epithelium stained deep blue, rods clear; 
convoluted and collecting tubules filled with crystals of pigment. 
Instead of using absolute alcohol for injecting the renal 
artery, the writer’s carmine-glycerine fluid may be employed. 
After having injected the artery in this way, the kidney is 
placed in a vessel of absolute alcohol, and divided into small 
pieces while immersed in that fluid. The glycerine being anhy- 
drous, prevents the diffusion of the indigo-salt within the kid- 
ney, while the alcohol fixes the pigment. Sections should be 
made from the cortex and medulla, and mounted permanently 
in resinous turpentine. If the glycerine injection has been suc- 
cessful, all the glomeruli and capillaries will be filled with a 
transparent red mass (Fig. 101). If the indigo excretion has 
reached the third stage, the collecting tubules in the medulla 
will be filled with blue crystals of indigo-carmine, and the vasa 
recta with a red mass, the two arranged in alternate rows. 
Such specimens leave nothing to be desired in the way of 
demonstrating the structural relations just described. 222 
MANUAL OF HISTOLOGY. 
BIBLIOGRAPHY. 
Ferrein. Mem. de I’acad., p. 502. Paris, 1753. 
Muller. De glandularum, etc. Leipz., 1880. And Unters. lib. d. Eingew. d. 
Fische. Berlin, 1845. 
Husciike. Lehre d. Eingeweide. Leipz., 1844. 
Gerlach. Muller’s Archiv, p. 378, 1845, and p. 102, 1848. 
Yirciiow. Virchow’s Archiv. Bd. XII., p. 310. 1857. 
Beer. Die Bindesubstanz d. Mere, etc. Berlin, 1859. 
Ludwig. Handb. d. Phys. Bd. 11., p. 638. And Wiener med. Wochen. 1864. 
Roth. Diss. Bern, 1864. 
Chronsczewski. Virchow’s Archiv. Bd. XXXI., p. 153. 1864. 
Sciiweigger-Seidbl. Die Mere, etc. Halle, 1865. 
Stilling. Ein Beitrag, etc., Diss. Marburg, 1865. 
Hufner. Vergl. Anat. u. Phys. d. Harn. Leipz., 1866. 
Lindgrbn. Z. f. rat. Med. 1868. 
Gross. Essai sur la structure microscopique des reins. Strassbourg, 1868. 
Isaacs. Jour, de la phys. Tome. 1., p. 577. 1858. 
Ludwig. Strieker’s Manual. 1871. 
Eberth. Centralb. f. d. med. Wiss., p. 227. 1873. 
Henle. Eingeweidel., 3 Aufi. 1874. 
Frey. Mikroskop. 6 Aufi. 1877. And Handb. 4 Aufi. 1874. 
Heidenhain. Schultze’s Archiv. Bd. X. 1874. And Pfliiger’s Arch. Bd. IX, 
1874. 
Schachowa. Enters, üb. d. Mere. Diss. Bern, 1876. 
Nussbaum. Beitr. z. Anat. und Phys. d. Mere Sitzungsber. d. Mederrh. u. Sw. 
Bonn, 1877. 
Runeberg. Nord. Med. Ark. XL, 3. No. 13. 1879. 
Henschen. Akad. Afhandling in Upsula. Stockholm, 1879. 
Klein and Smith. Atlas of Histology. Part XL 1880. CHAPTER XV. 
THE MALE EXTERNAL AND INTERNAL ORGANS OF GENERATION, 
WITH THEIR GLANDULAR APPENDAGES. 
Dr. J. HENRY C. SIMES, 
Lecturer on Histology, University of Pennsylvania. 
Penis.—The copulative organ of the male consists of erec- 
tile tissue, and is made up of three bodies, each enclosed in a 
fibrous membrane, the tunica albuginea. Two of these bodies 
are termed corpora cavernosa; the third corpus spongiosum; 
through the latter the urethra passes. 
The tunica albuginea consists of connective tissue and elas- 
tic fibres, with some smooth muscular elements. From the in- 
ternal surface of this membrane arise numerous trabecuhe, or 
bands, composed of the same tissue as the membrane; they 
divide and subdivide, forming a very intricate reticulum. The 
cavities thus formed freely communicate one with the other, 
and are lined with a single layer of flattened endothelial plates. 
This system of intercommunicating lacunae is in reality nothing 
but a true venous network. It is in direct communication with 
the veins of the organ. By the overfilling of these cavities with 
blood the erectile state is produced. 
Externally, the tunica albuginea is surrounded by loose 
subcutaneous tissue, in which numerous elastic fibres are pres- 
ent. Longitudinal bundles and a few oblique fibres of involun- 
tary muscle are also found in this areolar tissue. The skin cov- 
ering the penis is thin, and possesses numerous fine hairs, 
which have an increased length as the root of the organ is 
approached; they are connected with ordinary sebaceous 
glands which open into their follicles. Sudorific glands are 
also present in the skin of this organ. The internal leaf of 
the prepuce resembles closely a mucous membrane; papillae 
are numerous, but there is an absence of hairs, and the seba- 224 
MANUAL OF HISTOLOGY. 
ceous follicles glands) are sometimes difficult to find 
in the adult. In new-born children, however, these glands are 
abundant and well developed. The convoluted glands are here 
absent. 
The extremity of the penis terminates in a cone-shaped 
body, the glans penis, which has a cavernous structure very 
similar to that in the body of the organ, and differing only 
in the size of the meshes and 
the trabeculae, the former being 
smaller and the latter more deli- 
cate. The external or mucous 
surface of the glans is covered 
with a laminated pavement epi- 
thelium, the cells of the upper 
layer being quite flat, those of 
the middle layer ribbed, while in 
the lowest hiyer they are colum- 
nar. There are numerous elastic 
fibres in the mucous membrane 
of the glans, and many single 
or branched papillae are seen, 
some containing club - shaped 
nerve-terminations. 
The system of blood-vessels 
in connection with the penis con- 
sists of arteries, veins, capilla- 
ries, and cavernous spaces. The 
modes of communication between 
these several vascular structures 
are three : a direct passing of the 
blood from the larger arterial to 
the larger venous branches; a 
somewhat coarse venous reticu- 
lum communicating with a system of arterioles; and, finally, 
a direct capillary anastomosis. 
Fig. 102.—Transverse section through the in- 
jected glans : a, epithelium of the urethra ; b, 
tunica mucosa; c, corpus cavernosum urethrae ; 
cl, corpus cavernosum glandis; e, mucous mem- 
brane of the glans; /. epithelium of the glans. 
Klein. 
The lymphatic system of the penis is represented by lymph- 
spaces, capillaries, and large trunks. The former, the spaces, 
are oblong in shape, and occur in the loose subcutaneous tissue 
surrounding the tunica albuginea; they communicate with a 
capillary system, which is disposed in longitudinal meshes. 
The large lymph-trunks formed from these smaller vessels are THE MALE ORGANS OF GENERATION. 
situated along the dorsum of the organ, and communicate with 
the lymph-glands in the pelvis and those of the groin. 
The nerves and their terminations in the penis are derived 
from the cerebro-spinal and sympathetic systems. In the loose 
tissue external to the tunica albuginea large medullated fibres 
are observed; these give off smaller branches which enter the 
cavernous structure, and may be followed for some distance as 
medullated or non-medullated fibres. In this same tissue are 
found, at the root, shaft, and vicinity of the corona glandis, 
Pacinian corpuscles. They are oval in shape, and have their 
long diameter parallel to the long axis of the penis. These 
bodies have also been met with in the cavernous structure. 
The glans is especially rich in nervous elements, and here are 
found bodies known as the “genital nerve-corpuscles,” situated 
in the tissue of the mucous membrane at the base of the papil- 
lae. These bodies are round in shape, vary in size from 0.1489 
to 0.2001 mm. in diameter, and have characteristic constrictions 
upon their surface, giving them a mulberry-like appearance. 
The ordinary terminal bulbs of Krause are also met with in 
this location. 
The urethra of the male serves as the excretory canal for 
the urine and seminal fluid. An anatomical division is made 
into the prostatic, membranous, and spongy parts. The canal 
is lined with a mucous membrane, external to which there is a 
fibrous layer rich in elastic fibres, having a cavernous struc- 
ture ; external again to this is the muscular coat, composed of 
involuntary muscular fibres arranged in two layers, an internal, 
or longitudinal, and an external, or circular. There are also 
numerous fasciculi of oblique fibres, which serve to connect the 
two layers. 
The histological structure and arrangement of the three 
parts of the urethra are unlike, and must be separately 
studied, (a) In the prostatic portion the mucous membrane 
lies in longitudinal folds. A laminated epithelium covers the 
inferior wall, while the sides and superior wall are lined with 
a transitional variety. The prominence of this portion of the 
urethra, the colliculus seminalis, is composed of elastic tissue 
and smooth muscular cells, which form a cavernous structure. 
Throughout this spongy tissue, near the surface, are seen 
glands similar to those found in the prostate. Eaceraose glands 
(Littre’s glands), imperfectly developed, lined with cylindrical 226 
MANUAL OF HISTOLOGY. 
epithelial cells in their acini, and at their orifices with lami- 
nated epithelium, are also present. The muscular tissue in 
this part of the urethra is intimately connected with that of 
the prostate ; its fasciculi have generally a longitudinal direc- 
tion, and send off oblique bundles into the mucous mem- 
brane. (5) The membranous por- 
tion of the urethra has its mucous 
membrane covered by an epithe- 
lium similar to that met with in 
the prostatic portion. The glands 
of Littre are absent. Beneath the 
mucous membrane a long-meshed 
erectile tissue of a cavernous na- 
ture is found. Here the organic 
muscular layer is poorly devel- 
oped, and it is covered by trans- 
verse bundles of striped muscular 
fibres, the musculus uretJiralis. (c) 
Passing to the spongy portion, the 
mucous membrane is found thrown 
into longitudinal folds, which are 
in places connected by transverse 
ones, forming depressions, known 
as the lacunce Morgagnii. These 
are not glandular in their nature. 
The epithelium covering the mu- 
cous membrane in this portion is 
mostly cylindrical, but as it ap- 
proaches the meatus urinarius 
gradually assumes a pavement 
character. Glands of Littre are found throughout this part. 
The muscular elements are even less prominent here than in 
the membranous portion. 
Fig. 103.—Transverse section through 
the spongy portion of the urethra (corpus 
cavernosum urethras): 6, tunica mucosa : c, 
muscular cords; d, vascular spaces of the 
corp. cavern. ; e, glands; /, excretory duct 
of gland ; g, longitudinal muscles; ft, tunica 
albuginea. Klein. 
Well-developed and numerous papillae are seen projecting 
from the mucous membrane of the urethra into the epithelium. 
They possess a single capillary loop, or several loops are ob- 
served, especially in the fossa navicularis. These papillae are 
absent or imperfectly developed at the points where a transitional t 
epithelium is met with. Here the capillaries are arranged to con- 
stitute a reticulum beneath and parallel to the epithelial covering. 
The nerves of the urethra are found forming a network THE MALE ORGANS OF GENERATION. 
227 
around the muscular coat, similarly as elsewhere, in connection 
with smooth muscular fibres. Small nerve-fibres have been 
traced into the epithelial lining. Collections of ganglionic 
nerve-cells are found on the posterior surface of the membra- 
nous portion; in the dense connective tissue at the posterior 
portion of the bulb ; and lastly, in the network of nerve-fibres 
around the vessels at the side of the bulb. 
The lymphatic system of the urethra is found in the mu- 
cous membrane, near the epithelium. It consists of a network 
of vessels with longitudinally arranged meshes ; they are con- 
nected with the lymphatic vessels of the bladder, and also open 
into the lymphatic canals of the glans penis. 
Cowpefs glands.—These organs, two in number, are situ- 
ated in the striated muscular tissue which surrounds the mem- 
branous portion of the urethra. They are lobulated, oval, and 
belong to the racemose group of glands. They are composed 
of acini and excretory ducts which unite to form a single duct 
for each gland, and discharge into the bulbous portion of the 
urethra. The acini constituting the several lobules are separated 
by connective tissue intermixed with smooth muscular fibres; 
they possess a structureless membrana propria, and are lined 
with columnar cells, which are imbricated upon their outer thin 
portions. The ducts are lined with flattened columnar cells, 
and a layer of smooth muscular fibres is seen running along 
them. A capillary network surrounds the glandular structure. 
The prostate may be described as a glandular organ, pecu- 
liar in having its stroma composed of involuntary muscular 
elements. Externally it possesses a connective-tissue envelope 
which is united to bands of smooth muscular fibres that run 
in every direction, and constitute the cortical substance of 
the organ. From this cortex numerous bands or trabeculae 
of a similar muscular nature proceed, forming an intricate 
network, and making up the greater part of the gland ; in the 
meshes of this reticulum is placed the glandular structure. 
The thickness of the cortex, or the amount of glandular sub- 
stance, varies according to the position, whether behind or in I 
front of the urethra, and it is found that the glandular struc- 
ture is comparatively more developed behind and in the lower 
portions than in front of the urethra. 228 
MANUAL OF HISTOLOGY. 
The arrangement of the glandular elements is similar to 
that in the racemose glands, and consists of excretory ducts ter- 
minating in glandular vesicles or acini. The ducts which have 
their orifices in the urethra at its prostatic portion, and upon 
its inferior wall, are here lined with a transitional, or, when 
large, with a pavement epithelium, which gradually changes 
Fig. 104.—Transverse section through the caput gallinaginis: «, epithelium of surface; b. vesicuia 
prostatica ; c, epithelium of the vesicuia ; d. muscles ; e, ejaculatory duct: /, excretory duct of the pros- 
tatic glands; g, upper wall of the urethra ; muscles running vertically. From a child. Klein. 
into a columnar variety as the ducts penetrate the organ. The 
basement-membrane is structureless, and is invested by a mus- 
cular layer. The acini are also lined by a columnar epithelium 
and possess a structureless membrana propria; their shape is 
usually pyriform, and they have a diameter varying between 
0.1254 and 0.23 mm. The epithelial cells of the acini frequently 
contain granules of brownish pigment. THE MALE ORGANS OF GENERATION. 
229 
Transversely striated muscular fibres are also met with in 
the prostate, both anterior and posterior to the urethra, ex- 
tending into the cortical substance, and between the glandular 
structure in the interior of the gland. 
The blood-vessels of the organ come from the large trunks 
surrounding it; they pass into its structure and form a reticu- 
lated capillary system around the glandular substance. 
Medullated nerve-fibres are found surrounding the cortex 
in connection with groups of oval ganglionic centres. Paci- 
nian bodies are also ob- 
served in the cortex of the 
prostate, and in its interior 
are small medullated nerve- 
fibres which form a reticu- 
lum. 
A peculiar structure is 
found in the upper and pos- 
terior part of the prostate. 
It has the appearance of a 
duct, with walls resembling 
an artery, in so far as it 
consists of an internal longi- 
tudinal, a middle circular, 
and an external longitudi- 
nal coat. The middle coat is composed mostly of smooth mus- 
cular elements, while the external and internal coats are only 
partly made up of them. The interior of this structure is filled 
with a rich vascular network, pigment particles, and smooth 
muscular fibres. 
Fig. 105.—Transverse section through the central 
glandular substance of the prostate. From an adult. 
Klein. 
The vesicula prostatica, which forms a cul-de-sac in the 
middle of the prostate, beneath the middle lobe, opening by a 
duct at the summit of the colliculus seminalis, possesses a 
fibrous wall in which there are smooth muscular cells and is 
surrounded by a thin layer of cavernous tissue ; it is lined by 
a laminated epithelium, into which small conical papillm pro- 
ject ; small branched and tortuous glands are also found open- 
ing into its cavity. 
The testicles are glandular organs which secrete the sper- 
matic fluid, and are in the male organism the sexual represen- 
tatives of the ovaries in the female. 230 
MANUAL OF HISTOLOGY, 
The glandular structure, together with the of "the 
testicles, is enveloped by a dense fibrous membrane, the tunica 
albuginea. This is surrounded by a serous sac, the tunica 
vaginalis 'propria. Finally the testicle and spermatic cord are 
invested by the tunica vaginalis communis and the whole is 
contained in the scrotum. 
The tunica albuginea upon its external surface, or that 
covered by the tunica vaginalis propria, is smooth and shin- 
ing ; it consists of dense connective tissue with some elastic 
fibres ; upon the posterior border of the testicle it increases in 
thickness, and is here termed the corpus Highmori, or medias- 
tinum testis, which passes into the gland. It also sends off 
from its whole internal surface numerous bands or trabeculae, 
the septula testis, which run toward the mediastinum, and 
divide the interior of the testicle into conical lobules, having 
their apices directed toward the corpus Highmori. These tra- 
beculae contain smooth muscular fibres and blood-vessels. It 
is in these lobules or spaces that the secreting elements of the 
gland are situated. 
The serous sac, or tunica vaginalis, has its visceral layer, the 
tunica adnata, intimately united to the tunica albuginea over 
the testicle, but it is loosely attached to that over the epididy- 
mis. This membrane consists of connective tissue traversed 
by delicate elastic fibres, and lined on its surface with a layer 
of polyhedral cells, varying in size and containing oval nuclei 
with one or two nucleoli. Upon the upper portion of the tes- 
ticle and sharp edge of the epididymis, the tunica adnata is 
frequently found to possess tufted excrescences; these pro- 
cesses are covered by several layers of flattened epithelial cells, 
or a single layer of round or cylindrical-bodies. A capillary 
loop is seen extending into the tufts. 
The parietal layer of the tunica vaginalis propria consists 
of connective tissue, elastic fibres, and epithelium, as in the 
visceral layer. 
The tunica vaginalis communis, which covers the tunica 
vaginalis propria, is composed above of a loose, laminated con- 
nective tissue, but it becomes more dense below. Between 
this tunica and the tunica propria unstriped muscular fibres 
are found, while upon its external surface there are the striped 
fibres of the cremaster muscle. Small non-vascular peduncu- 
lated excrescences are also found upon this surface. The mem- THE MALE ORGANS OF GENERATION. 
231 
brane is connected externally by connective tissue with the 
muscular layer of the scrotum, the dartos. 
The muscle of the scrotum, the dartos, consists of numerous 
smooth muscular fibres, arranged singly or forming a more or 
less continuous layer. 
The skin of the scrotum is peculiar in containing consider- 
able pigment, while there is an absence of fat in the subcu- 
taneous tissue. Hairs, large sebaceous follicles, and sweat- 
glands are also present in the skin of the scrotum. 
The hydatid of Morgagni is a structure found upon the 
anterior surface of the head of the epididymis, and is thought 
to be the remains of Muller’s duct. It is met with in two 
forms, either as a vesicle containing a clear fluid (with cells, 
and nuclei—ciliated epithelial cells are also at times present), 
and connected to the epididymis by a solid fibrous peduncle, or 
as a flattened structure possessing scarcely any stalk, which 
is simple or divided into lobules; the latter form is most fre- 
quently seen. At times it is found to communicate with the 
canal of the epididymis. 
Between the head of the epididymis and the vas deferens, 
situated upon the posterior edge of the testicle, a small organ 
is seen, consisting of several whitish nodules. Each nodule is 
composed of a tube forming a number of convolutions and ter- 
minating in a club-shaped extremity. The tubes contain a 
clear fluid and are lined by a cylindrical epithelium, the cells 
of which are undergoing degeneration. Until ten years of age 
this organ is fully developed; after this period it experiences 
degeneration. This structure is known as the organ of Gir- 
atdes, and represents the remains of the Wolffian bodies. 
The glandular or parenchymatous structure of the testicle 
consists of canals or seminiferous tubules about 0.1128 to 
0.1421 mm. in diameter ; are folded on themselves sev- 
eral times so as to constitute lobules, and are situated in the 
spaces formed by the trabeculm of the tunica albuginea. The 
tubules not only are folded but divide and subdivide, anasto- 
mose, and terminate by loops. Toward the apices of the lob- 
ules the tubules gradually become more straight, fewer in 
number, and pass into the corpus Highmori, forming the 
rete testis. From the upper part of the rete emerge twelve to 
seventeen larger tubules which pass through the tunica albu- 
ginea, after which again become convoluted and form a 232 
MANUAL OF HISTOLOGY. 
number of conical lobules, named the coni vasculosi, which 
form the head of the epididymis. These tubules gradually 
unite to form a single canal, which is much convoluted, and 
develops an elongated body, the body and tail of the epididy- 
mis. The convolutions becoming less and less marked, the 
tube, increased in calibre, then leaves the testicle and ascends, 
at first somewhat spirally, but soon after in a perfectly straight 
course, constituting the vas deferens. Before this duct is 
formed, a short csecal branch, named the vas aberrans, is at- 
tached to the tube. 
The seminiferous tubules either take their origin from blind 
extremities or anastomoses, the former being more frequently 
met with in children. Surrounding the tubules there is seen 
a framework of connective tissue, which proceeds from the 
septa. This intertubular connective tissue is distinctly lam- 
inated, and each lamella is formed of a fenestrated endothe- 
lial membrane, and a fenestrated connective-tissue membrane, 
which thus constitute numerous communicating spaces, that 
are the rootlets of the lymphatic system of the testis. The 
number of lamellae between the seminal tubes varies, and their 
relation to the tubes is very intimate, but depends upon the 
amount of fluid present in the interlamellar lymph-spaces. 
Groups of peculiar cells are found between the lamellae of the 
intertubular connective tissue. These cells have been observed 
by histologists, and by most are thought to be connective-tissue 
corpuscles. Klein, however, says they are epithelial in nature, 
and derived from the epithelial columns of the Wolffian body. 
In the meshes formed by this reticulated fibrous tissue are 
located the seminiferous tubules, the membrana propria of 
which is thought, on the one hand, to be structureless, or, on 
the other, to be composed of oval, flattened corpuscles, placed 
at regular intervals, which form an endothelial membrane. The 
tubules are found filled with corpuscles. Those at the periphery 
covering the membrana propria are round or polygonal in form, 
upon transverse section. In children, the cells of the tubules 
contain a finely granular and pale substance, but in adults 
they are filled with yellow pigment. Two typical forms of cor- 
puscle are observed, one with dark granular nuclei, the other 
with bright ones that have or have not nucleoli. The number 
of nuclei varies ; usually there are one or two ; but they may 
reach thirty or more. Many variously formed cells are seen, THE MALE ORGANS OF GENERATION. 
233 
which fact is held to indicate active proliferation. These bodies 
are termed seminal cells, and in the embryo are said to possess 
contractility and amoeboid movement. 
The seminiferous tubules upon entering the corpus High- 
mori lose their special external coat, which blends with the 
connective tissue of this region. Their epithelial lining con- 
sists of cylindrical cells with short cilia. After leaving the 
corpus Highmori and increasing in size, they have an additional 
coat of smooth muscular fibres, which, further down in the 
body of the epididymis, consists of two layers, an internal and 
an external or longitudinal, coat. The epithelium lining the 
canal of the epididymis is composed of cells with long, oval 
nuclei, and provided with long tufts of cilia. Indeed, the lar- 
gest cilia found in the human body are upon the large cylindri- 
cal cells, which, cover the upper part of the canal of the epi- 
didymis. Beneath this layer of ciliated bodies is a second of 
small, polyhedral ones with round nuclei. 
The vas deferens, which may be considered as analogous 
in many respects to the excretory duct of a glandular organ, 
is made up of an external or fibrous coat, a middle or mus- 
cular, and a mucous membrane, which is located most inter- 
nally. Covering this membrane are epithelial elements which 
differ in the various parts of the duct. At the beginning there 
is a single layer of cylindrical cells, between which, sometimes, 
there are spindle-shaped bodies; the former possess delicate 
cilia. At about four centimetres from the epididymis the cilia 
are lost, but the character of the cells remains the same, ex- 
cept that a striated border can be seen in many. In children, 
a difference exists between the extra- and intra-abdominal por- 
tions of the duct. The former, or extra, is lined by a lami- 
nated epithelium, composed of a superficial layer of short 
cylindrical cells, beneath which are one or two layers of round 
or polyhedral cells. All these corpuscles have a relatively 
large nucleus. The intra-abdominal portion of the duct has a 
lining similar to that observed in the adult. 
The mucous coat is made up of connective tissue and elas- 
tic fibres, the former consisting of intersecting fasciculi, the 
latter of a close network. The membrane is thrown into 
two or three longitudinal folds or rngm. Near the lower end 
of the vas deferens, in the ampulla, the longitudinal folds 234 
MANUAL OP HISTOLOGY. 
are connected by transverse ones, and thus depressions are 
formed. 
The muscular coat consists of smooth muscular fibres ar- 
ranged in three layers : an inner, or longitudinal, which is 
feebly developed ; a middle, or circular, which is substantial in 
character, and an external or longitudinal. This coat is less 
developed in young children than in adults. 
In the external fibrous coat, or tunica adventitia of the vas 
deferens, are found bundles of smooth muscular fibres running 
longitudinally. They are derived from the cremaster interims, 
which muscle is well developed at the origin of the vas deferens, 
but gradually diminishes in size as it enters the abdominal cavity. 
The vas deferens possesses a dense plexus of medullated 
nerve-fibres, the spermatic plexus, situated in the tunica ad- 
ventitia. From this plexus several smaller trunks proceed 
which penetrate into the muscular and mucous coats. Scat- 
tered along these nerve-trunks are seen small ganglion-cells, 
which are round or oval. 
The blood-vessels of the testicle come from the internal 
spermatic artery and enter the gland partly at the corpus 
Highmori and partly upon its surface. They surround the 
seminiferous tubules as a capillary plexus of large meshes. 
The epididymis receives its blood from the deferential artery, 
and also to some extent from the vessels of the testicle. The 
vas deferens possesses a rich capillary network in its muscular 
coat and also in its mucous membrane beneath the epithelium. 
The nerves of the testicle come from the internal spermatic 
plexus ; their mode of termination has not as yet been satis- 
factorily explained, Letzerich, however, describes fine nerve- 
fibres in the testicles of mammals; they penetrate the connec- 
tive tissue and raembrana propria, terminating between this 
layer and the first row of cells in dark granular masses! 
The lymphatic system of the testicle consists of a series of 
lacunae, lined with endothelial cells, which surround the semi- 
niferous tubules; in the interstitial connective-tissue, these 
communicate with canals from which others are given off to 
the connective-tissue septa of the lobules. Beneath the tunica 
albuginea another network of lymphatic canals is also found, 
which penetrate the tunic, especially upon the dorsum of the 
organ, and finally, uniting with the lymphatics of the epididy- THE MALE ORGANS OF GENERATION. 
235 
mis and tunica vaginalis, form several large trunks, winch fol- 
low the spermatic cord. Distinct networks of lymphatic ves- 
sels are found in the vascular and nervous layers of the sper- 
matic cord, and some are seen close to the muscular coat of the 
vas deferens. 
The seminal vesicles, designed as receptacles for the fluid 
secreted by the testicles, are, with some slight modifications, 
similar in structure to the vas deferens. They are composed 
of a mucous, muscular, and fibrous coat. The mucous mem- 
brane is covered with a superficial layer of cylindrical and a 
deep layer of polyhedral-epithelial cells, and is thrown into 
folds, longitudinal and transverse, forming depressions. The 
muscular coat consists of three layers, an internal or longi- 
tudinal, a middle or circular, and an external or longitudinal. 
The fibrous coat is abundantly supplied with networks of ves- 
sels and nerves. Here the ganglionic collections are highly 
developed, each corpuscle being quite large and containing a 
single nucleus, or even at two. 
The ejaculatory ducts are, histologically, similar to the last 
described organs. As they approach the prostate their cylin- 
drical epithelium gradually changes into the transitional va- 
riety, and subsequently into the laminated pavement, as they 
approach their point of outlet in the urethra. Their mucous 
membrane is uneven from the longitudinal and transverse 
folds. After entering the prostate the muscular substance of 
the ducts undergoes cavernous transformation. 
When the testicle attains its full physiological develop- 
ment, which occurs in man at puberty, there is secreted by the 
organ a peculiar fluid, the semen or sperma. This fluid is 
whitish, slimy, and colorless, and has an alkaline or neutral re- 
action. Semen examined as discharged from the orifice of the 
urethra, in coitu, appears as a very different fluid, having re- 
ceived the secretions from the various accessory glands of the 
generative system. It is now more fluid, opaque, strongly al- 
kaline in reaction, and has acquired a peculiar odor. Placed 
under the microscope there is seen suspended in a hyaline fluid 
an infinite number of moving thread-like bodies called seminal 
filaments, spermatozoa, spermatozoids, seminal elements, etc. 
They are divided into a head, body or middle portion, and tail. 236 
MANUAL OF HISTOLOGY. 
The shape of the head is pyriform, the broad paid being con- 
nected with the body ; each has an average length of 0.0045 
mm., and its breadth is about half as much. The middle por- 
tion or body is about 0.0061 mm. long, while the tail measures 
about 0.0406 mm. Both the body and 
head of the seminal elements seem to 
be rigid, the terminal thread or tail 
having an active motion. From this 
description it will be seen that a com- 
parison of its structure with that of a 
ciliated epithelial cell is admissible, and 
indeed'quite reasonable. 
The way in which spermatozoa are 
formed is still imperfectly known, and 
two different views claim our attention. 
They are as follows : a. The nucleus of the seminal cells 
moves to the periphery, then at the opposite side the proto- 
plasm of the cell is elongated into a caudal appendage; the 
nucleus continuing to advance causes the protoplasm to be- 
come more and more elongated, and it is ultimately lengthened 
into a thread-like tail, while the nucleus, with its thin layer of 
protoplasm, constitutes the head. b. In this view the columnar 
or prismatic-shaped cells, the most external layer of cells fill- 
ing the seminal tubules, are thought to be the spermatozoa- 
producing elements. The inner remaining cells of the tu- 
bules experience no further development. During the active 
stage of the gland the spermatic cells become elongated, and 
extend into the centre of the tubule ; their free extremities 
become enlarged, and have a number of buds or club-like pro- 
jections, eight to twelve, developed upon them. In each bud 
is formed a nucleus; these nuclei eventually become the 
heads of spermatozoa, and the protoplasm is further developed 
into the body and tail. The cells from which the spermatozoa 
have their origin are named svermatoblasts. 
Fig. 106.—Seminal elements of 
man: a, undeveloped ; 6, mature. 
St. George. 
Klein, in his recent “ Atlas of Histology,” gives a very ex- 
tended description of the development of spermatozoa. Ac- 
cording to this writer there are several layers of epithelial 
cells lining the inside of the membrana propria of the seminal 
tubules. These layers he divides into an outer and inner. 
The outer, situated next to the membrana propria, embraces 
the germ-cells of Sertoli. The inner layer, those nearer the THE MALE ORGANS OE GENERATION, 
237 
lumen of the tubule, are tlie seminal cells of Sertoli. These 
latter are usually arranged in two or more layers, polyhedral 
in shape when placed closely together, but more spherical when 
next to the lumen of the tubule ; they are uniform in size and 
contain a single nucleus. The nucleus is spherical, possesses 
no limiting membrane, and contains a convolution of thick 
fibrils, or rods, in a transparent matrix, A more minute ex- 
amination of the nucleus shows that the fibrils are arranged in 
certain definite forms, which indicate changes preparatory to 
division, as has been pointed out by Strassburger, Hertwig, 
Flemming, and others. The various forms, taken by the nucleus 
before dividing, correspond to what is termed the “convolu- 
tion,” the “basket,” the “wreath,” the “monaster,” or the 
“ dyaster.” The entire process of the indirect division of the 
nucleus is termed by Flemming haryokinesis. 
Toward the lumen of the tube the above-described cells are 
seen with their nucleus either dividing or divided into two 
daughter-nuclei. From these daughter-nuclei are developed 
the daughter-cells, or spermatoblasts, and by an interesting 
series of changes the spermatozoa are formed. 
“The nucleus of the spermatoblasts at first retains its spher- 
ical shape, but is invested in a distinct membrane, the convo- 
lution of fibrils changes into a honey-combed reticulum, some- 
times with one or two nucleoli, and the nucleus is not placed 
in the centre but in the periphery of the cell.” 
“ Next the nucleus becomes uniform in its substance and 
transparent, all traces of a reticulum have disappeared. The 
cell-substance has collected at one end of the nucleus as an 
elliptical granular mass, and appears separated from it by a 
transparent, clear bag.” 
“ In the next stage the nucleus becomes flattened and dis- 
coid, so that when viewed from the surface it is broad and cir- 
cular, but appeals narrow and staff-shaped when seen in profile. 
The cell-substance at this time is drawn out into a cylindrical 
or club-shaped granular body, separated from the nucleus by 
a shorter or longer clear tube, the former clear bag. At the 
front part of the nucleus is seen a short and tapering curved 
projection, and at its hind end—viz., that directed toward the 
clear tube and cell-substance—there is also to be found a short- 
pointed process extending into the clear tube Just named.” 
“In the next stage the nucleus becomes more flattened and 238 
MANUAL OF HISTOLOGY. 
oblong. In tlie last stage the granular body lias become 
changed into a long, thin, and homogeneous filament.” 
“In what relation do, then, these different parts of the fully 
formed spermatozoon stand to the parts of the developing ele- 
ment—that is, the spermatoblast? A comparison shows at 
once that the head of the ripe spermatozoon is the changed 
nucleus of the spermatoblast; that the filament, or tail, is de- 
rived from what has been mentioned above as the granular 
body of the original cell. The middle piece of Schweigger- 
Seidel is an outgrowth of the nucleus of the spermatoblast, 
that is, of the head, the spermatozoon, and the clear tube of 
the developing spermatozoon, described above as embracing 
the hind part of the nucleus and separating the latter from 
the granular body, is the sheath which, in some instances 
(triton and salamander), is observable on the middle piece of 
the fully formed spermatozoon.” 
In short, the head of the spermatozoon is derived from the 
nucleus, while the tail has its origin from the body of the sper- 
matoblast. 
BIBLIOGRAPHY. 
COOPER, A. Obs. on the Struct, and Dis. of the Testis. London, 1830. 
Wagner. Muller’s Archiv. 1836. 
Panizza, B. Osservazioni anthropo-zoot.-fisiol. Pavia, 1836. 
Valentin. Ueb. d. Verl. d. Blutgef. im Penis d. Menschen. Muller’s Arch. 1838, 
Kobelt. Die mannl. u. weibl. Wollustorgane. Freiburg, 1844. 
Kolliker. Gewebelehre und Yerhandl. d. Wiirzb. med.-phys. Ges. 1851. 
Kohlrauscii. Zur Anat. u. Pbys. d. Beckenorgane. Leipzig, 1854. 
Sappet. L’urethre de I’homme. 1854. 
Leydig, F. Zur Anat. d. mannl. Gescblechtsorg. in Zeitschr. f. wiss. Zool. Yol. 11. 
And Histologic. 1857. 
Jarjayay. Rech. anat. sur I’urethre de I’homme. Paris, 1857. 
Merkel. Gottinger Nachrichten. No. 1, p. 7. 1863. And Arch. f. mikr. Anat. 
Yol. 1., p. 309. 1865. 
St. George, y. La Yalette in Arch. f. mikr. Anat, Yol. 1., p. 403. 1865. And 
Strieker’s Manual. 
Pettigrew, in Proo. Roy. Soc. Yol. XY., p. 244. 1866. 
Schweigger-Setdel, in Virch. Arch. Yol. XXXYIL, p. 235. 1866. 
Balbiana. Journal de I’anat. et de la phys., p. 218. 1868. 
Letzericii, in Virch. Arch, Yol. XLIL, p. 570. 1868. 
Stieda. TJeber den Ban des Menschen-Hoden, Arch. f. mikros. Anat. Yol XTY., 
p. 17. 1877. 239 
BIBLIOGRAPHY. 
Sertoli. Sulla struttura di canalicoli seminif. del testicoli. Arch. p. le scien. 
med. Yol. 11., p. 107. 1877. 
Menzel. Ueber Spermatozoen. Arch. f. klin. Chir. Yol. XXI., p. 518. 1877. 
Valentin, in Zeitschr. f. rat. Med. Yol. XVIII., p. 31. Yol. XXI., p. 89. 1879. 
Langer, in Wien. Sitz. Yol. XLVL, p. 120. 1879. 
Rouget. Compt. rend. Yol. IY., p. 903. 1879. 
Frey, Heinrich. Histology and Histochemistry of Man. 1880. 
Klein, E., and Smith, E. Noble. Atlas of Histology. 1880. CHAPTER XVI. 
THE FEMALE EXTERNAL AND INTERNAL ORGANS OF GENERA 
TION, WITH THEIR GLANDULAR APPENDAGES—PLACENTA. 
Dr. J. HENRY C. SIMBS, 
Lecturer on Histology, University of Pennsylvania. 
The external female genitals are tlie labia majora, labia 
minora, and clitoris. 
The labia majora are folds of skin, the subcutaneous tis- 
sue of which contains a large amount of adipose tissue. Their 
internal surface has the nature of a mucous membrane, while 
externally it is similar to the common integument. Here hairs, 
sebaceous glands, remarkable for their large size, and sweat- 
glands, are found. The papillae, vessels, nerves, and Pacinian 
corpuscles do not differ from those found elsewhere in the skin. 
The labia minora may be considered as folds of mucous 
membrane. They are covered by a laminated pavement-epi- 
thelium and the deepest layer contains pigment granules. 
Conical vascular papillae are seen beneath the epithelium. 
In the connective-tissue framework of the mucous membrane 
smooth muscular elements are found. Capillary networks are 
seen on the surface beneath the epithelium, and in the sub- 
stance of the membrane, from which arise small veins, consti- 
tuting a plexus, and giving this structure the character of an 
erectile tissue. Upon the external surface of the folds are found 
sebaceous glands without hairs. These glands are. absent at 
birth. There is no adipose tissue in the labia minora. 
The clitoris is covered by a mucous membrane which is a 
continuation of that of the labia minora, and to which it is 
similar in structure, in so far as epithelium, mucous tissue, and 
papillae are concerned. The mucous membrane covering the 
glans of the organ is found to have those peculiar nerve-termi- 
nations in its structure, the genital nerve-corpuscles, which THE FEMALE ORGANS OF GENERATION. 
have been described as existing in the mucous membrane of 
the glans penis. 
Beneath the mucous membrane of the clitoris are found the 
corpora cavernosa and glans ; the latter is in connection with 
both bulbi vestibuli, which correspond to the corpus spongio- 
sum urethrae of the male. These structures consist of erectile 
or cavernous tissue, which, like that in the penis, is made up of 
a vascular network, mostly venous in character, and erectile in 
nature ; they are also surrounded by a fibrous tunic analogous 
to the tunica albuginea of the penis. 
The vestibule has its mucous membrane, which is a con- 
tinuation of the mucous membrane of the clitoris, thrown into 
a number of folds. Opening upon its surface are numerous ori- 
fices of racemose mucous glands. These glands are collected 
into groups around the orifice of the urethra and vagina. They 
consist of branched ducts, which at their deeper parts are de- 
veloped into a number of acini; they are lined with a simple 
epithelium ; at their orifices they have the laminated pavement- 
epithelium of the mucous surface. These glands vary in diame- 
ter between 0.5 mm. to 2.5 mm. The vessels of the vestibule 
form a network near the mucous surface, and are connected to 
the capillary loops in the papillae. 
Opening upon each side of the vaginal entrance is the orifice 
of the duct belonging to the gland of Bartholine. These or- 
gans, two in number, are analogous to Cowper's glands in the 
male. They belong to the racemose group, and are composed 
of ducts and acini, which have an epithelium lining of cylin- 
drical cells. 
The hymen consists of a duplicature of the mucous mem- 
brane of the vagina. Its laminated epithelium is similar to 
that of the vestibule. The papillm are numerous, long, simple 
or multiple, and project from 0.2 to 0.8 mm. into the epithelial 
covering. The vascular and nervous supply is very abundant. 
The vagina consists of an external coat of connective tissue, 
a middle coat of muscular tissue, and an internal mucous coat. 
The mucous membrane is uneven, thrown into ridges and papil- 
lary elevations, which are especially well-marked in the neigh- 
borhood of the vaginal entrance. The epithelium lining the 
canal is a laminated pavement-epithelium, into which the vas- 242 
MANUAL OF HISTOLOGY. 
cular papillae of the mucous membrane extend. In the latter 
coating are found numerous elastic fibres in the fasciculi of 
connective tissue; bundles of smooth muscular cells are also 
present. Tubular glands, lined with ciliated columnar epithe- 
lium at their fundus, have been described as existing in the 
mucous membrane of the vagina by Preuschen. Hennig also 
speaks of similar glands being present in this membrane. The 
submucous tissue is very vascular and loose in texture. The 
muscular coat consists of an internal longitudinal and an ex- 
ternal circular layer of smooth muscular fibres, between which 
are many oblique connecting fasciculi. The external fibrous 
tissue is loose in texture, and has embedded in it the external 
venous plexus. 
The vascular system of the vagina is composed of arteries, 
veins, a venous plexus, and capillaries. The plexus is met 
with in the folds of the vagina. It is a cavernous structure 
possessing smooth muscular fibres, and has an arrangement of 
trabeculm similar to that found in other erectile organs. 
The lymphatics and nerves of the mucous membrane of the 
vagina are abundant. The latter form networks in which there 
are found ganglion-cells, in groups or single; as in the male 
genitals, these cells are of two sizes. The ultimate terminations 
of the nerve-fibres are as yet undetermined. The fluid secreted 
by this membrane has an acid reaction. 
The urethra possesses a raucous membrane covered by a 
transitional epithelium at its upper portion, the superficial 
layer of cells being short cylinders, which gradually become 
shorter, until the deepest layer is seen made up of rounded cells. 
The lower portion of the canal has a lining of laminated pave- 
ment-epithelium similar to that of the vestibule. The mucous 
membrane has numerous papillae extending into the epi- 
thelium. In this layer are seen at places many lymph-corpus- 
cles, sometimes amounting to an infiltration, when it may be 
considered as adenoid in nature. The submucous tissue is 
mostly composed of venous networks ; it is in fact a cavernous 
tissue. As in the male, there are present in the mucous mem- 
brane the glands of Littre, seen especialty abundant near the 
meatus urinarius. The muscular coat of the urethra consists 
of an internal longitudinal and an external circular layer of 
smooth muscular fibres ; in the external layer are also the THE FEMALE ORGANS OF GENERATION. 
transversely striated muscular fibres of the urethral muscles. 
The external fibrous coat of the urethra consists of wavy con- 
nective-tissue fasciculi, which have a longitudinal and circular 
course. 
The uterus possesses an external covering of serous mem' 
brane, the peritoneum ; anteriorly it is more intimately con- 
nected with the organ than posteriorly, while at the sides the 
layers are separated, in order to permit the passage of blood- 
vessels, lymphatics, and nerves into the uterine substance. 
The tissue composing the greater part of the uterus is formed 
of smooth muscular fibres, the arrangement of which is very 
irregular, but three more or less distinct layers have been de- 
scribed. The external one, which is relatively thin, consists 
mostly of fibres running longitudinally, although many circu- 
lar fasciculi are seen. The middle layer exceeds the others in 
thickness, its fibres take a longitudinal, transverse, or oblique 
direction, while the internal layer is essentially circular, and 
forms the sphincters of the uterus. The contractile elements 
of these muscular layers are intimately united together by a 
cementing substance, forming fasciculi or bundles, which are 
again held together by connective tissue in which elastic fibres 
are found. The shape of the cells in the normal uterus is fusi- 
form, frequently very long, and in transverse section round or 
oval, with several angles. The nucleus is always single, rod- 
like or oblong in shape. 
The mucous membrane lining the uterus is closely connected 
to the muscular tissue. It has no connective-tissue framework 
of fibres, but its structure resembles the stroma of lymphoid 
organs, in which the framework is made up of spindle and 
fusiform cells. The surface of this membrane varies in differ- 
ent parts; at the fundus and body it is smooth, except at the 
orifices of the Fallopian tubes, where there is a slight folding ; 
in the canal of the neck it is thrown into numerous branching 
folds, the joliccß paZmatce. At the upper end of the isthmus of 
the cervix a distinct border indicates the termination of the 
mucous membrane of the body. The epithelium covering this 
portion of the membrane is columnar in shape, and provided 
with short cilia. There are found in the mucous membrane 
of the fundus and body numerous tubular glands, which are 
either simple tubes or they divide about their middle, and ter- 244 
MANUAL OF HISTOLOGY. 
minate in blind ends; frequently they have a spiral course, 
corkscrew-like ; but generally their direction is vertical to the 
plane of the membrane; they open into the cavity of the 
uterus. The existence of a membrana propria in these glan- 
dules. utriculares is denied by some, or if present it is only 
toward the orifice of the gland. In the pregnant organ, how- 
ever, an extremely delicate, structureless membrane, in which 
oval nuclei are found, is thought to represent such a structure. 
The cells lining these glands are prismatic in shape, their broad 
ends directed outward ; the slender extremities projecting into 
the lumen of the gland are provided with cilia. 
The mucous membrane lining the canal of the cervix is 
denser and thicker than that of the body. It possesses a con- 
nective-tissue investment which lies between it and the muscu- 
lar layer, and it also differs from the lining of the body in the 
presence of folds, which constitute the plicse palmatse. The 
epithelium covering this portion of the uterus is made up of 
cylindrical ciliated cells, in the upper two-thirds of the canal, 
but as the external os uteri is approached it gradually as- 
sumes the laminated pavement variety. Minute papillm, pro- 
vided with a capillary loop, are found in the lower half of the 
canal. The folds of membrane consist of a firm fibrous tissue, 
a few smooth muscular elements, and a scanty amount of elas- 
tic fibres. Here are also located the mucous follicles of the 
cervix, or, as some histologists consider them, depressions only 
of the mucous membrane; they are lined with a cubical epi- 
thelium, and possess a structureless membrana propria, which 
is intimately connected to the connective tissue. From an 
occlusion of the orifices of these follicles there are developed 
small retention cysts containing mucoid fluid, usually round or 
oval, and measuring 0.3 to 0.5 mm. in length ; they are known 
as the omila Nahothi. The fluid secreted by the mucous mem- 
brane of the uterus differs from that of the vaginal mucous 
membrane in having an alkaline reaction. 
The mucous membrane covering the intra-vaginal portion 
of the uterus is a continuation of the vaginal raucous mem- 
brane, consisting of a similar structure, and composed of a 
connective-tissue framework with papillae projecting into its 
covering of laminated pavement-epithelium. At times this por- 
tion is found to contain the ovula Nabothi. 
The uterus is a very vascular organ ; a capillary network is THE FEMALE ORGANS OP GENERATION. 
found in the muscular coat and mucous membrane. In the 
latter such reticula are seen to surround the glands. The veins 
are very large, possess delicate walls, and are valveless. In the 
cervical portion, a more regular distribution of vessels is met 
with, and their walls are unusually thick. 
Numerous lymphatic vessels are found beneath the peri- 
toneal covering of the uterus, and arched passages are seen 
ending in loops or blind extremities under the mucous mem- 
brane of the cervix. Lymph clefts and vessels are also met 
with in the intermuscular connective-tissue. 
The nerves of the uterus are derived from the genital sper- 
matic ganglia. On the posterior wall of the neck a large 
ganglionic mass is met with, from which most of the nerves 
have their origin. Nervous filaments may be followed as far 
as the mucous membrane, and a few histologists have traced 
them into the papillae of the cervix, while in the muscular coat 
they are said to terminate in the nuclei of the muscular ele- 
ments. 
During the physiological function of menstruation and 
gestation the uterus experiences certain modifications. In the 
former there is an increase in the size of the organ, owing mostly 
to the great increase of blood in the vessels ; the glands of the 
mucous membrane are also increased in size. The discharge of 
blood during this period is due either to a rupture of the dis- 
tended capillaries, or a diapedesis, in which the walls remain 
uninjured. On microscopical examination of the menstrual 
fluid it is found to contain, besides the blood-elements, numer- 
ous uterine epithelial cells. 
The modifications of the uterus during gestation occur es- 
pecially in the muscular elements, which are greatly hyper- 
trophied, and there is also a new formation of them. The 
blood-vessels, lymphatics, and nerves also experience an in- 
crease in size, the latter by a thickening of their perineurium. 
The mucous membrane of the body of the uterus during gesta- 
tion is separated from the uterus, previously becoming thicker, 
softer, and more vascular, and constitutes the decidua. The 
cervical portion of the mucous membrane does not participate 
in this metamorphosis ; it retains its epithelium, and secretes a 
mucous plug, which fills the canal of the cervix during preg- 
nancy. Subsequent to delivery a new mucous membrane and 
glands are developed on the cavity of the uterus, and the hy- MANUAL OF HISTOLOGY. 
pertrophied and newly formed muscular elements undergo 
retrograde development and fatty metamorphosis. 
The Fallopian tubes, or temporary ducts of the ovary, con- 
sist of an external covering furnished by the peritoneum, rich 
in connective tissue and blood-vessels ; a muscular coat made 
up of an outside layer of longitudinal, and an inside layer of 
circular involuntary muscular elements ; and, finally, an in- 
ternal mucous membrane. A division of the tube is made into 
two parts: that toward the uterus, into which it opens, the 
much narrower portion, is the isthmus, while the free half is 
the ampulla, which terminates in the fimbriae. The mucous 
membrane, upon transverse section of the tube, in the narrow 
portion, is seen thrown into simple longitudinal folds, while in 
the ampulla the folds are much more complicated, and in a 
transverse section have a dendritic appearance. The epithelium 
covering the mucous membrane consists of ciliated columnar 
epithelial cells. The movements of the cilia occasion a current 
in the direction of the uterine opening. There is an absence of 
glands in the mucous membrane of the Fallopian tubes. The 
same histological elements are present in the fimbriae as in 
other portions of the tube, of which they are a direct contin- 
uation. 
The ovary for histological study may be divided into two 
parts, the cortex and medullary substance; covering the cor- 
tex is a layer of columnar epithelial cells, named the ovarian 
or germ epithelium (Fig. 107). In a perpendicular section, the 
germ-epithelium is here and there seen to extend down into 
the substance of the organ and form tubes—the ovarial tubes. 
The cortical substance or parenchymal zone consists of several 
layers of dense connective tissue, in which are found ovarial 
tubes and ovarian follicles. The most external follicles are im- 
perfectly developed, while those lying deeper are more highly 
developed and contain the ovum. Internal to the cortex is the 
medullary substance or vascular zone, in which are numerous 
blood-vessels, giving it the nature of a cavernous tissue. 
The stroma of the ovary consists of fibrillar connective tis- 
sue. In the vascular zone it is somewhat loose in texture, and 
contains a network of elastic tissue. There are also found in 
this zone fasciculi of smooth muscular fibres, which follow the THE FEMALE ORGANS OF GENERATION. 
large and medium sized arteries, at times constituting a slieatli 
for the vessels. In the stroma of the parenchymal zone the 
connective-tissue forms an outer layer of short, dense fibres 
Fig. 107.—From the ovarium of a rather old bitch; portion of a sagittal section, a, germ-epithelium; 
6, b, ovarial tubes ;c, c, younger follicles; d, older follicle ; <2, discus prollgerus, with egg ;/, epithelium 
of a second egg in the same follicle; g, tunica fibrosa folliculi: h, tunica propria follicull; i, follicular 
epithelium (membrana granulosa); k, collapsed degenerated follicle; I, vessels: m, m, cell-tubes of the 
parovarium, both longitudinal and transverse sections; y. tubular sinking in of the germ-epithelium into 
the substance of the ovary; 2, commencement of the germ epithelium close to the lower border of the 
ov&ry. Waldeyer. 
which run in every direction, and an inner one abounding in 
cells, in which the follicles are seen. 
The blood-vessels enter the ovary at the hilum. The arteries 
have a spiral, corkscrew-like course through the organ. At 
the hilum the veins form a convoluted mass, the bulb of the 248 
MANUAL OF HISTOLOGY. 
ovary. A capillary reticulum surrounds tlie follicles, and is 
situated in their internal membrane. 
The stroma of the hilum contains numerous lymphatics, 
which have an arrangement similar to that of the veins. Sur- 
rounding the follicles in their external lamina is found a dense 
network of lymphatics. 
The nerves enter the ovary at the hilum with the arteries, 
and they have been followed into the stroma between the large 
follicles, but their ultimate terminations have not as yet been 
ascertained. 
The follicles of the ovary, or Graafian follicles, consist of a 
connective-tissue wall separable into two layers: an internal, 
which contains the small capillaries, and an external, contain- 
ing the large blood-vessels and lymphatics. The outer layer is 
made up of the same connective tissue as the stroma of the 
ovary, in which are numerous spindle-shaped cells. The inter- 
nal layer consists of connective tissue, in which are numerous 
and variously shaped cells, fusiform, stellate, and small round 
bodies, the latter possessing amoeboid movement; there are 
also seen larger round or polygonal-shaped cells. This layer of 
corpuscles is the membrana granulosa. Within the follicle, 
and distending it, is an albuminous fluid holding a few bodies 
in suspension. Situated in the follicle, usually at that part 
most distant from the surface of the ovary—although this is 
not a rule without exception, since it is also found immediately 
below the most superficial part of the follicle—the ovum is 
found surrounded by a collection of cells of the granular mem- 
brane, known as the discus proligerus. Two kinds of cells 
form the discus proligerus, the follicular and egg epithelium ; 
the latter lie in immediate contact with the vitelline membrane, 
and are closely adherent to it. 
An examination of the mature ovum demonstrates it to 
measure 0.28 to 0.1879 mm. in diameter; it is spherical in 
shape, ana is a typical cell, consisting of an investing mem- 
brane, the vitelline membrane, or zona pellucida, which is 
a dense, transparent, homogeneous substance, apparently 
pierced by numerous minute pores. This membrane is prob- 
ably developed from the cells of the discus proligerus, and from 
the layer described as the egg epithelium. The cell-contents, 
protoplasm, or vitellus is a granular mass composed of albu- 
minous and fatty particles, and a more or less distinct reticu- THE FEMALE ORGAN'S OF GENERATION. 
lum of fine fibrils. Within the vitellus is seen the nucleus or 
germinal vesicle (also presenting a delicate reticulum of fibrils), 
situated eccentrically, spherical in shape, measures 0.037 to 
0.451 mm. in diameter, shining, transparent, and contains the 
nucleolus or germinal spot, which is a highly retractile body, 
finely granular, supposed to be non-vesicular, and measures 
0.0046 to 0.0068 mm. in diameter. 
The mature Graafian follicle, which is seen on the surface 
Fig. 108.—A, primordial egg of the human being; 8 months’ foetus. B, primordial follicle of the 
rabbit. C, primordial follicle of a dove. T), a somewhat older follicle of the same animal; commence- 
ment of the formation of the subordinate yolk. E, blind end of the ovary of an ascaris nigrovenosa; 
germinal vesicles (some of which possess a germinal spot and Schrbn’s “granule”) in a diffuse mass of 
protoplasm. F, egg of the ascaris nigrovenosa from about the middle of the ovary; Schron’s granule ; 
commencement of the deposition of yolk-matter. G, egg from a follicle (2 mm. in diam.) of the rabbit: 
a. egg epithelium ; b, striated zone with radiating striae; c, germinal vesicle : d, germinal spot; e, yolk. 
Waldeyer. 
of the ovary, giving rise to a prominence, ruptures during the 
menstrual period and empties its contents, viz. : the ovum, 
fluid contents, and discus proligerus into the Fallopian tube. 
The cause of the rupture is an increase in the contents of the 
follicle, and a fatty metamorphosis of the cells of the wall of 
the follicle. As a result of this rupture of the Graafian vesi- 
cle, there is formed a yellow body, the corpus luteum, which 250 
MANUAL OF HISTOLOGY. 
reaches its fall development in a few weeks after the raptur- 
ing of the follicle, or when impregnation has occurred after the 
lapse of two or three months. It consists of a central portion, 
at first red, becoming gray, and a peripheral portion, yellow in 
color, thrown into folds. These folds are made up of the in- 
ternal membrane and cells. The central portion in a fresh 
corpus luteum consists of a very vascular tissue, in which are 
seen, numerous large cells, containing a red coloring substance 
and hsematoidin crystals. A retrograde metamorphosis occurs 
in the yellow body, supposed to be due to a want of nutrition 
caused by a wasting of the arteries, and there only remains a 
white cicatrix, the corpus albicans. The time required for 
the disappearance of a corpus luteum when impregnation has 
taken place—a true corpus luteum—is several months, lasting 
to the end of gestation; but for the disappearance of a false 
corpus luteum, or when impregnation has not occurred, it only 
requires a few weeks. It is, however, to be remembered, that 
every Graafian follicle with its contents does not reach full de- 
velopment ; most of them experience fatty or colloid metamor- 
phosis. 
The ovaries have their origin from the Wolffian bodies. A 
thickening of the epithelial covering is early observed upon 
the side of these bodies; at the same time and place a cellular 
projection growing from the connective tissue of the organ is 
noticed. From this increase of epithelium the Graafian folli- 
cles and ova are developed, later the ovarial epithelium ; from 
the connective tissue is built up the vascular system of the ovary. 
The Graafian follicles are developed from collections of cells, 
irregular in shape, or, as they are named, ora chains, consisting 
of small-sized peripheral cells, which later form the rnembrana 
granulosa, and the primordial ova ; these last are recognized 
by their large size, granular or reticulated protoplasm and 
central position. The ova chains are sometimes enclosed in a 
homogeneous rnembrana propria, forming a tubular structure, 
as in the cat; this membrane, however, is not found in all ani- 
mals. These chains are developed by an ingrowth of the epi- 
thelial cells covering the surface of the ovary. 
The parovarium, or remains of the Wolffian body, situated 
in the broad ligament, is made up of twelve to fifteen tubules, 
which possess a rnembrana propria, lined by a single layer of 
ciliated epithelium, and contain a transparent substance. THE FEMALE ORGANS OF GENERATION. 
251 
The placenta is divided into a uterine and foetal portion. 
The former consists of cells irregular in shape, containing one 
or several nuclei, and at times one or more nucleoli. These 
cells are separated by an intercellular substance, either hyaline, 
granular, or fibrous in nature. Fusiform cells, in which a rod- 
shaped nucleus is seen, are also found, and are thought to in- 
dicate the presence of smooth muscular elements. The tufts 
upon the surface of the uterine placenta, which divide and sub- 
divide, pass quite deeply into the foetal placenta, yet no direct 
transformation of them into the foetal tissue can be demon- 
strated ; they appear to terminate in fibrillated tissue, which 
contains none of the cellular elements of the uterine placenta. 
The blood-vessels of the uterine placenta are arteries and 
veins, with no intermediary capillary system ; they communi- 
cate by means of sinuous spaces, limited by placental tissue 
only. These spaces are said to possess a delicate limiting wall; 
this statement, however, has not been confirmed. 
The foetal placenta is developed from the chorion, the villi 
or tufts of which growing into the uterine follicles- are covered 
by a columnar epithelium. The blood-vessels in the villi do 
not lie directly in contact with the wall of the villus, but are 
separated from it by a perivascular space. Besides a direct 
communication of the arteries and veins, there is also a capil- 
lary system present in the villi. Connective tissue accompa- 
nies the vessels into the villi from the chorion. The variety of 
connective tissue here met with is the mucoid, consisting of 
round, spindle, and stellate-shaped cells, with a structureless 
intercellular substance. There is a direct transformation of 
this mucoid connective tissue into the connective tissue of the 
chorion. 
BIBLIOGRAPHY. 
Bischofp. Beitr. zur Lebre v. d. menschl. Eihhllen. 1884. 
Valentin, in Muller’s Arch., p. 536, 1838. 
Goodsik. Auat. and Path. Researches. Edinburgh, 1845. 
Kobelt. Der Nebeneierstock des Weibes. Heidelberg, 1847. 
Steinun. TJeber d. Entw. d. Graaf. Foil. u. Eier d. Saugeth., Mittheil. d. Zu- 
richer naturf. Gesellsch. 1847. 
Robin. Arch, gener. de med. Vol. XVII., p. 358 and 405. 1848. And Vol. 
XVIII., p. 357. Also Gaz. med. No. 50. 1855. 
Rainey, in Phil. Trans., 11. 1850. 252 
MANUAL OF HISTOLOGY. 
Schroder van DEI! Kolk. Waarnemingen oves het Maaksel van de menschl. 
Placenta, etc. Amsterdam, 1851. 
Smith, Tyler-. Med. Chir. Trans. Yol. XXXV., 378. 1853. 
Remak. Unters. neb. d. Entwick. d. Wirbelthiere. Berlin, 1855. Med. Cemr. 
Zeit. No. 43. 1801. No. 3. 1863. 
Klebs, in Vircli. Arch. Yol. XXVIII. 1863. 
Pflugbr, E. Ueb. d. Eierstocke d. Saugeth. u. d. Menschen. Leipzig, 1863. 
Spiegelberg. Virch. Arch. Yol. XXX, p. 466. 1864. 
Kamenew. Enters, d. Blutgef. d. Mutterth. d. Placenta, Medicinsky Westnik. 
No. 13. 1864. 
Cornil, in Jour, da I’anat., p. 386. 1864. Unters. aus d. phys. Labor, zu Bonn, 
p. 173. Berlin, 1865. 
Polle. Die Nervenverbr. in d. weibl. Genital. Gsttingen, 1865. 
His, in Arch. 1 mikr. Anat. Yol. 1., p. 151. 1865. 
St. George, v. La Yalette, in Arch. f. mikr. Anat. Yol. lE, p. 56. 1866. 
Perier. Anat. et phys. de I’ovaire. Paris, 1866. 
Stricker. Wien. Sitz. June, 1866. 
Langiians, in Virch. Arch. Yol. XXXVIII., p. 543. 1867. 
Frankenhauser. Die Nerven. d. Gebarmutter. Jena, 1867. 
Jassinski. Zur Lehre ueb. d. Struct, d. Placenta. Virch. Arch. 1867. 
Virchow. Bildg. d. Placenta, in Gesamm. Abhandlungen. 1853. 
Bidder. Ueb. Hist. d. Nachgeb., in Holst’s Beitr. z. Gyniicol. 11. 1867. 
Ercolani. Giamb. delle gland, otricolare, etc. Bologna, 1868. 
Pltkol, in Arch. f. mikr. Anat. Yol. V., p. 445. 1869. 
Friedlander. Unters. ueb. d. Uterus. 1870. 
Hennig. Der Catarrh d. inn. weibl. Geschlechtsorg. 1870. 
Waldeyer. Eierstock. u. Ei. Leipzig, 1870. 
Lott and A. Rollet. Untersuchungen. 11. Leipzig, 1871. 
Langhans. Unters. ueber d. menschl. Placenta. Arch. f. Anat. u. Phys. 1877. 
Leopold. Stud. ueb. d. Uterus-schleimhaut. Arch. f. Gyn. Yol. XL, p. 110 and 
443. 1877. Also Yol. XII., p. 169. 1877. 
Hennig. Ueber Driisen der Vagina. Arch. f. Gyn. Yol. XII., p. 488. 1877. 
Fodlis, The Development of the Ova, and the Structure of the Ovary, etc. Jour, 
of Anat and Phys. Yol XIII.. p. 353. 1878-79. 
Frey, Heinrich. Histology and Histochemistry of Man. 1880. 
Klein, E., and E. Noble Smith. Atlas of Histology. 1880. CHAPTER XVII. 
THE RESPIRATORY TRACT. 
Lecturer on Anatomy and Physician to Department for Diseases of Chest, Long Island 
College Hospital. 
BENJAMIN F. WESTBROOK, M.D., 
The respiratory tract includes the nares and, perhaps, the 
pharynx, but as the latter is more commonly associated with 
the function of deglutition, and the former contain in their 
upper portions the organs of one of the special senses, they 
have been assigned to other portions of this work. This chap- 
ter is devoted exclusively to the consideration of those parts 
which are concerned in the respiratory process. As the pleura 
forms a part of the lung, and facilitates the movements of 
breathing, its structure may properly be described under this 
section. 
The air-tubes are in general made up of three layers: an 
outer of connective tissue and elastic fibres ; a middle, muscu- 
lar and cartilaginous; and an inner of mucous membrane. 
Their structure is more complex in the upper, and simpler in 
the lower portions of the respiratory passages. 
The larynx.—The muscles of the larynx are of the striped 
or voluntary variety. 
The ligaments and membranes are composed of yellow elas- 
tic fibres with some white fibrous tissue. Their structure can be 
easily demonstrated by the process of teasing or by employing 
the reagents ordinarily used for this class of tissues. The la- 
teral thyro-hyoid and the inferior thyro-arytenoid ligaments 
have the following peculiarities of structure : the lateral thyro- 
hyoid ligament usually encloses a small piece of hyaline carti- 
lage about the size and shape of a large grain of wheat. It 
is known as the cartilage triticea. In adult males it is usually 
calcified. It may be incorporated either with the cornu of the 
hyoid bone or with the superior cornu of the thyroid cartilage. 254 
MANUAL OF HISTOLOGY. 
The inferior thyro-arytenoid ligaments, or true meal cords, 
are made up almost entirely of yellow elastic fibres stretched 
across from the thyroid cartilage in front, to the vocal processes 
and adjacent anterior borders of the arytenoids behind. The 
elastic bundles originate, anteriorly, in a mass of connective 
tissue which occupies the angle of the thyroid. Posteriorly, 
many of the fibres are prolonged into the arytenoid cartilage, 
converting that part of it into reticular tissue. These liga- 
ments are continuous below with the lateral crico-thyroid mem- 
branes, and are described by some anatomists1 as their superior 
borders. 
The innermost fibres of the internal thyro-arytenoid mus- 
cle mingle with the outer fibres of this ligament, some ending 
in or taking their origin from them. The intimate relation be- 
tween the muscle and the ligament can be seen in a vertical sec- 
tion through the larynx. 
Of the laryngeal cartilages, the three larger are of the 
hyaline variety. Horizontal sections show a broad central area 
with two zones between it and either the outer or inner sur- 
face. The appearance of the zones or bands is thus described 
by Kheiner :2 “1. A thin peripheral portion, appearing to the 
naked eye as a narrow, bluish, opalescent band, which con- 
sists of a transparent and longitudinally striated matrix with 
elongated cartilage-cells arranged parallel to the surface. 2. 
The intermediate layer, a narrow, whitish, opaque band, con- 
sisting of a dull yellowish ground-substance with numerous 
large mother-cells containing fatty daughter-cells, 8, The 
broad central layer, with a perfectly transparent homogeneous 
matrix and few cells. The intercellular substance increases, 
relatively to the contained cells, from without inward, and, in 
the interior, presents numerous large spaces in which no cells 
are found. In the thyroid and cricoid cartilages the outer 
peripheral zone is thicker and more easily distinguished than 
the inner.” 
The following peculiarities are to be noted : the central por- 
tion of the thyroid, viz., that part which forms the anterior 
projection or angle, is distinguished by the great number and 
small size of its cells. It is penetrated by numerous fibres 
2 Quoted by Merkel in Anatomie u. Phys. des inensch. Stimxn- u. Sprach-Organs. 
Leipzig, 1863, S. 166. 
1 Quain’s Anatomy, eighth edition, Yol. 11., p, 284. THE RESPIRATORY TRACT. 
from that mass of connective tissue from which the vocal cords 
take their origin. After prolonged maceration in some alka- 
line solution, this cartilage can be separated into three parts— 
two lateral and an anterior or median. 
The arytenoids are not composed exclusively of hyaline 
cartilage. The vocal process, as already mentioned, presents a 
yellow reticulated structure, the fibres of which are continuous 
with those of the true vocal cords. The apex has also a re- 
ticular structure when there is no joint between it and the 
cartilage of Santorini. The elastic tissue is then continuous 
with that which connects it with the corniculum. A hori- 
zontal section through the arytenoid at the level of the vocal 
process shows the reticular structure of the process, the hya- 
line character of the body of the cartilage, and the gradual 
transition from one to the other. 
The three cartilages already described are subject to calci- 
fication and partial ossification. This occurs more frequently 
and at an earlier age in the male than in the female. It also 
begins at a later date in those who have been castrated. It 
makes its first appearance at the points of muscular attach- 
ment. As the cartilages undergo calcification they increase in 
size, so that the calcified larynx of old age is larger than that 
of the young adult. The matrix also splits up into a fibrous 
texture, not affected by acetic acid. 
The cornicula laryngis or cartilages of Santorini and the 
cuneiform cartilages of Wrisberg, as well as the sesamoid 
cartilages (when they exist) are of the reticulated variet}r. 
The cartilago triticea is hyaline and prone to calcification. 
The epiglottis consists of reticular cartilage. On transverse 
section, however, the intercellular substance is seen to be a 
spongy elastic substance, granular on section ; at the periphery 
yellow fibres are present. The elastic cartilage should be ex- 
amined with a high power. 
The mucous membrane of the lar3mx varies in its structure 
in different situations. On the laryngeal surface of the epi- 
glottis it is thin. 
The epithelium in the upper half is in several layers. The 
deepest cells are somewhat columnar or pyramidal in form, 
while the superficial ones are fiat. The lower half is covered by 
a stratified, columnar, ciliated epithelium. The epithelium rests 
upon a thin, apparently structureless basement-membrane. 256 
MANUAL OF HISTOLOGY. 
The mucosa is made up of delicate connective-tissue fibres, en- 
closing in their meshes a series of lymph-spaces. Connective- 
tissue cells are also found here, and some elastic fibres. There 
are a few small papillae in the upper portion. The submucous 
layer is thin, contains many elastic fibres, and is continuous 
with the perichondrium. It contains the racemose mucous 
glands, whose ducts open upon the surface. Some of the larger 
glands are lodged in the depressions of the cartilage, and some 
are even situated on its anterior aspects, their ducts passing 
through to the posterior side. 
In the submucous tissue there are lymphatic follicles, some 
of which are arranged about the mucous glands and their ducts. 
The membrane covering the false vocal cords, arytenoid 
cartilages, and ary-epiglottic folds, as well as that lining the 
ventricles and inferior compartment of the larynx is thicker 
and more loosely attached to the subjacent parts. It is covered 
by stratified columnar, ciliated epithelium, except upon the 
edge of the false vocal cords and over the inner surfaces of the 
arytenoids, where it is of the pavement variety. The mucosa 
contains a large amount of tymphoid tissue, which holds in its 
meshes lymphoid cells. Closed lymph-follicles are also found 
in the submucous tissue of the false vocal cords and on the 
floor of the ventricle.1 That portion of the mucous membrane 
which covers the true vocal cords is thin, more closely attached, 
and has no mucous glands. In its anterior half it has numer- 
ous small papillae (0.07 to 0.08 mm. in height, Coyne) project- 
ing at the edge and on the superior and inferior surfaces of the 
cord. They are composed of connective tissue, with many elas- 
tic fibres. Their vascular supply is slight. The membrane in 
this situation is covered by stratified pavement-epithelium, 
continuous posteriorly with that which covers the inner sur- 
faces of the arytenoids. Numerous racemose glands send their 
ducts obliquely upward and inward to discharge their secretion 
upon the upper and under surfaces of the vocal cords. 
In front of the corniculum laryngis, on either side, is a col- 
lection of racemose glands surrounding the cartilage of Wris- 
berg. Another collection is found between the arytenoids. 
The epithelium can be examined, either by scraping it from 
the surface, or in sections. The mucous glands are best seen 
1 Coyne : Archiv. d. Physiologic, p. 92, 1874. THE RESPIRATORY TRACT. 
257 
in sections of the hardened larynx. They are lined by cubical 
glandular epithelium. The capillary blood-vessels of the laryn- 
geal mucous membrane are small with wide meshes, giving the 
membrane a paler appearance than that of the pharynx. 
The lymphatics are numerous in the mucous and sub- 
mucous layers. They may be injected with Berlin blue, by 
puncturing the submucous tissue. 
In the nervous filaments are ganglion cells. The mode of 
termination is not definitely known. But in the mucous 
membrane of the epiglottis end bulbs have been found. The 
methods of examination will be found elsewhere. 
The trachea and 'primary bronchi.—The rings of the trachea 
and bronchi are composed of hyaline cartilage. Longitudinal 
sections of these rings show that the cells lying near the peri- 
phery, underneath the perichondrium, are flattened, and ar- 
ranged with their long axes parallel to the surface. Internally 
they are oblong and perpendicular to the former. 
The ends of the incomplete rings are connected, posteriorly, 
by a layer of smooth muscular fibres, which are attached to 
the fibrous tissue of the perichondrium. The attachment is 
to the inner aspect of the ends of the cartilages, so as to throw 
the muscular layer forward of the most posterior projection of 
the rings. 
These muscular fibres also exist in the spaces between the 
rings, where they are attached, on either side, to the fibrous 
tissue of the tube. Outside of the transverse fibres are a few 
filaments which have a longitudinal direction. They are at- 
tached to the fibrous membrane. 
The fibrous membrane which encloses the cartilages and 
completes the framework of the tube is composed of connective 
tissue containing a considerable portion of elastic tissue, par- 
ticularly in its external portion. The outer layer of the fibrous 
membrane encloses both the cartilages and the muscle fibres. 
The inner layer is thin and lies between the rings and the 
glandular layer. 
The mucous membrane is covered by several layers of epi- 
thelial cells, the deeper being more or less spherical or ovoid, 
whilst the superficial ones are columnar and ciliated. The 
columnar cells, losing their cilia, are continued into the ducts 
of the mucous glands. These glands are very numerous, and 
often of considerable size. They are racemose, the acini being 258 
MANUAL OF HISTOLOGY. 
lined with cubical epithelium. Owing to the distention of some 
of the gland-cells by mucus or by the action of reagents, they 
assume a rounded form, and the nuclei are pressed against the 
attached ends of the cells. Such corpuscles are known as 
“goblet” cells. Some of the larger glands project posteriorly 
outside of the fibrous membrane, but the great majority of them 
are situated internally to that structure, and then form a dis- 
tinct layer, the “glandular layer.” They are most abundant 
in the spaces between the cartilages. Their ducts pierce the 
Fig. 109.—Transverse section of bronchial twig, 6 mm. in diameter : a, outer fibrous layer; b, muscu- 
lar layer ; c, inner fibrous layer (mucosa) ; d. epithelium. Magnified 30 diameters. F. E. Schulze. 
mucous membrane obliquely, so that the entire length of a 
duct is not usually found in a section of the tracheal wall. 
At short intervals, between the columnar cells of the surface, 
other cells are found, of a spindle shape, or somewhat stellate. 
These cells send processes upward to the surface and down- 
ward into the basilar membrane, where they become contin- 
uous with other branched cells. The prolongation which passes 
upward to the surface is usually single, though it may occasion- 
ally send off a delicate filamentary branch, which is lost in 
the cement substance between adjacent cells. 
The process, sometimes double, which passes downward 
connects with a tissue in the mucosa which resembles the 
lymph canalicular system of other parts. It is made up of 
a network of branched cells, or connective-tissue corpuscles, 
which line a series of spaces, that in turn communicate with 
the lymphatic capillaries of the mucous membrane. Sikorsky 
injected a watery solution of carminate of ammonia into the THE RESPIRATORY TRACT. 
259 
bronchial tubes of cats and dogs while the animals were liv- 
ing, and found, 'post-mortem, that the carmine had penetrated 
through the interepithelial cells above described into the lym- 
phatic vessels below. 
The interepithelial cells have a small nucleus which stains 
more deeply with hsematoxylon than do the nuclei of the ordi- 
nary epithelial cells. In vertical section they are more opaque 
than the epithelia, and, when seen on the surface of the mem- 
brane, appear as dark spots among the ciliated cells. 
The lymphatic capillaries join to form larger trunks which 
run along the sides of the bronchi communicating freely with 
each other and with those of the neighboring blood-vessels. 
They are called by Klein the peribronchial lymphatics. 
Beneath the mucosa, and between it and the mucous glands, 
are numerous bundles of yellow elastic tissue having a longi- 
tudinal direction. Some of the bands are quite thick, particu- 
larly in the posterior wall, and raise the mucous membrane in 
longitudinal folds. 
The mucous membrane of the trachea and bronchi has a 
rich network of capillaries. The racemose glands are also sup- 
plied with a vascular network which ramifies in the fibrous tis- 
sue by which they are surrounded. The natural injection of 
these vessels, which occurs in cases of bronchitis in the human 
subject, is often sufficient for their examination. 
The mode of termination of the nerves has not been ascer- 
tained. 
The trachea should be hardened in chromic acid or Mullers 
fluid, followed by alcohol. The sections may be stained in 
hsematoxylon. In order to preserve the ciliated epithelium, it 
is well, as Professor Rutherford suggests, to cut the sections 
with the freezing microtome. The lymphatics can be injected 
by puncture. 
The smaller bronchi and lungs.—Beyond the primary bron- 
chi (or first division of the trachea) the muscular fibres encircle 
the tubes inside of the cartilaginous and fibrous layer ; indeed, 
the primary divisions show the first sign of this new arrange- 
ment. The cartilages change from incomplete rings to irregu- 
larly shaped plates, which are found on all sides of the tubes, 
but their microscopic structure remains unaltered. The longi- 
tudinal elastic fibres are contained between the muscular and 
mucous coats. The tubes divide and subdivide generally in a 260 
MANUAL OF HISTOLOGY. 
dichotomous manner, diminishing gradually in calibre, the 
combined area of the branches, however, always exceeding that 
of the trunk from which they spring. No change occurs in 
their structure, except a gradual thinning of their walls, until 
they reach a diameter of about 1 mm., when the cartilages 
disappear and the attenuation is more marked. The circular 
muscular fibres continue to exist, as also the longitudinal elas- 
tic fibres, but the mucous glands disappear. After a still 
further division the tubes are diminished to a diameter of .20 
to .30 mm., the muscular fibres become more sparse, and the 
epithelium is reduced to a single layer of low, somewhat cubi- 
cal cells, which are still ciliated. These are the lobular bronchi, 
each one going to a single pulmonary lobule. The lobular 
bronchi each give off ten to fifteen smaller tubes, known as the 
terminal bronchi or bronchioles. They are straight and cylin- 
drical, their walls are very thin and 
delicate, and their epithelial cells 
gradually lose their cilia and become 
flattened plates. Each bronchiole 
leads to a smaller division of the lob- 
ule, called an acinus or lobulette.1 The 
bronchioles divide into short canals, 
the alveolar passages, usually three 
for each acinus. Their walls are thin 
and bulge outward on all sides, form- 
ing, externally, little projections or 
Fig. 110.—A system of alveolar pas- 
sages with, infundibuli from an ape’s 
lung: rt, terminal bronchial twig; 6, b, 
infundibula; c, c, alveolar passages. 
Magnified 10 times. F. E. Schulze. 
elevations; internally, shallow depressions or cavities which 
open into the calibre of the tube. They also give off; secondary 
branches, called infundibula, which have groups of such little 
cavities attached to, and opening into them. The little cavities 
are the alveoli or air-cells of the lung. Erom this description 
it will be seen that each lobule has ten to fifteen acini or lobu- 
lettes, and that the lobulette is made up of alveoli or air-cells, 
which open into common spaces or infundibula, which in turn 
communicate with the alveolar passages. The alveoli, which 
are connected with the infundibula, are called terminal alve- 
oli ; those which open on the sides of the alveolar passage are 
called the parietal alveoli. The latter are called, by Dr. Wa- 
ters, the bronchial alveoli. The alveolar passages, infundibula, 
1 Dr. Waters : The Anatomy of the Human Lung, London, 1860. THE RESPIRATORY TRACT. 
261 
and alveoli have a flat pavement epithelium resting on an ap- 
parently structureless basement-membrane. Outside of this are 
numerous elastic and muscular fibres, curving around the cavi- 
ties, and holding in their meshes the capillary blood-vessels. 
The muscular fibres are very numerous in the walls of the al- 
veolar passages and infundibula. The alveoli have a diameter 
of .1 to .4 mm., but their size varies greatly according to the 
degree of inflation of the lungs. 
Fig. 111.—Section through an infundibulum : a, entrance from the alveolar passage into the infundi- 
bulum ; 6, nuclei of smooth muscular cells. Magnified 30 diameters. P. E. Schulze. 
The epithelium in the alveoli of the fetal lung is columnar 
in shape, so that a section of such a lung resembles a section 
of a glandular organ. But when the alveoli are distended at 
birth, the cells change their form. In transverse sections, either 
real or optical, of the alveolar walls, the epithelial plates pro- 
ject more or less into the cavity, according to the degree of dis- 
tention of the lung. This change of shape undoubtedly occurs 
during life with the alternating expansion and contraction of 
the thorax, and should be tafcen into account in considering 
the pathological changes of inflammation, collapse, etc. By 
injection of a weak solution of silver nitrate per cent.) into 
the bronchi of a fresh lung, and its subsequent immersion in 262 
MANUAL OF HISTOLOGY. 
alcohol, the lines between the epithelial plates can be demon- 
strated. The nuclei can be stained with carmine. 
Some of the cells are converted into hyaline plates. The 
alveolar epithelium of the human lung is not so readily demon- 
strated as that of animals, principally because too long a time 
usually elapses between death and the post-mortem dissection. 
In some traumatic cases an autopsy can be made early, and as 
Fig. 112.—Interior of an alveolus. Lung injected with a solution of nitrate of silver to show the lines 
between the alveolar epithelial cells. P. E. Schulze. 
favorable opportunity had of examining these structures. They 
can be shown very well in fresh sections cut with Valentin’s 
knife. 
The spaces between the alveoli and acini contain the elastic 
fibres mentioned above, together with a few oval connective- 
tissue nuclei and muscular elements. The lobules are held 
together by thin septa of connective tissue. The connective 
tissue is also found in the angles of division of the lobular 
bronchi and bronchioles. 
The muscle-cells may be identified by their elongated, 
fusiform nuclei. A further proof of their existence is found 
in certain cases of cirrhosis of the lung, in which many distinct 
muscular fibres are found in the new connective tissue.1 
The branches of the pulmonary artery follow the course 
1 Buhl: Lungenentz. Tuberculosis, u. Schwindsucht, Munchen. 1873, S. 358. THE RESPIRATORY TRACT. 
263 
of the bronchi as far as the lobules. The lobular branches 
are terminal arteries—i.e., they do not anastomose with each 
other. They break up into very small branches, which encircle 
the alveoli and supply the capillary plexuses of their walls. 
These capillaries are very small, and the network so fine that, 
when injected, the open spaces are not as wide as the vessels 
themselves. This, however, will vary with the degree of dis- 
tention of the lung. Between two adjacent alveoli only one 
Pig. 113.—Section of luiman lung injected through the pulmonary artery: a, a, free alveolar margins; 
6, small arterial branch ; c, c, alveolar walls seen in transverse section. F. B. Schulze. 
capillary plexus is found, the branches of which are seen to 
pursue an undulating course, projecting, first, into the cavity 
on one side, then into that on the other. These unite again 
into veins which run irregularly through the lobules to unite 
upon the bronchi and follow their course to the root of the 
lung. The peculiarities of the pulmonary veins are, Ist, that 
their united calibre does not exceed (if it equals) that of the 
arteries ; 2d, that they have no valves. The bronchial vessels 
supply the coats of the bronchial tubes and the surrounding 
connective tissue and the pulmonary pleura. 
But the line of demarcation between the bronchial and pul- 
monary circulations is indistinct on the venous side, as injec- 
tions thrown into the bronchial arteries fill the pulmonary 264 
MANUAL OF HISTOLOGY. 
veins and capillary plexuses and overflow into the pulmonary 
arteries.1 
It appears from this that part of the blood from the bron- 
chial arteries does, or may, return through the pulmonary veins. 
In their course through the lung, the pulmonary arteries lie 
upon the upper and anterior aspect of the bronchial tubes, 
while the veins are found on their inferior surface. The bron- 
chial arteries follow the tubes and divide with them. 
The lymphatics of the alveolar septa are a series of lacunar 
spaces lined by branched connective-tissue corpuscles, whose 
nuclei have already been described as being visible in ordinary 
sections of the lung. 
In sections of a lung treated with silver nitrate the forms 
of the cells are distinguishable. According to Klein the pro- 
cesses of these cells pass upward between the epithelial plates 
of the alveoli so as to bring the cells into direct communica- 
tion with the cavity, just as we have seen the interepithelial 
cells of the bronchial mucous membrane send certain processes 
upward between the columnar epithelia and others downward 
to the cells of the lymph lacunae. On examining the epithelium 
of an alveolus, small, round, dark spaces are seen between the 
cells ; these are said by Klein to be the projecting processes of 
the branched cells of the lymph lacunar system. The ends of 
these processes, both here and on the bronchial mucous mem- 
brane, are called pseudo stomata, in contradistinction to the 
true stomata of the serous membranes. 
The small spaces, or lacunae, open into lymphatic radicles, 
which have a regular endothelial lining. These pass inward 
toward the root of the lung, upon the bronchi and the walls 
of the vessels. On the vascular walls they communicate freely 
with each other, and at times completely invest the vessel with 
a lymphatic sheath like that of the cerebral vessels. In this 
situation they are called perivascular lymphatics. The peri- 
vascular and peribronchial lymphatics communicate freely. At 
the surface of the lung there is a plexus immediately beneath 
the pleura (subpleural lymphatics) from which trunks of some 
size run to the root of the lung. They communicate with the 
perivascular system and with the pleural cavity. The final 
termination of all these channels is in the bronchial glands. 
1 Dr. Waters. THE RESPIRATORY TRACT. 
265 
The nerves of the lungs are derived from the sympathetic 
and pneumogastric. Their mode of termination is not known. 
For the examination of the general structure of the lung it 
may be inflated and dried pretty rapidly in the sun or by a 
fire. For more careful examination it should be hardened in 
chromic acid, Muller’s fluid, or alcohol. The hardening fluid 
should be injected into the air-passages. 
In order to distend the vesicles it is well, before placing the 
lung in the hardening fluid, to inject the bronchi with simple 
gelatine. The vessels may also be injected with a colored 
mass. The lungs of the lower animals are used for these 
demonstrations, owing to the difficulty of obtaining normal 
human lungs in a perfectly fresh condition. The investigation 
of the lymphatics is attended with great difficulty. They may 
be demonstrated by the puncture method. Klein found that 
on injecting the blood-vessels, under high pressure, with Ber- 
lin blue or silver nitrate, some of the capillaries ruptured, and 
the fluid passed into the perivascular lymphatics. 
The pleura.—The pleura, like the other serous membranes, 
consists of a connective-tissue ground-substance covered by a 
single layer of polygonal endothelial cells. In the costal pleura 
the subserous connective tissue is more abundant, and its at- 
tachment to the thoracic wall is not so firm as is that of the 
pulmonary pleura to the lung. The structure of the pleura is 
most conveniently studied in the smaller mammals. It can 
also be demonstrated in young children. 
To demonstrate the endothelium of the surface, the thorax 
of a recently killed animal should be opened, care being taken 
not to rub or otherwise injure the pleura. The surfaces are to 
be washed by pouring distilled water over them, in order to 
remove the serum, and then a weak solution of silver nitrate 
(i—I per cent.) allowed to flow over them. After a few mo- 
ments the surfaces are bathed with pure water. The diaphragm- 
atic or mediastinal portion is then excised with scissors, 
immersed in distilled water or glycerine, and exposed to the 
daylight until it takes a light reddish-brown color. It may 
now be floated on to a slide, carefully smoothed by traction at 
the edges, and mounted in glycerine. The portion excised 
should be large, so that it can be manipulated without touch- 
ing the part which is to be examined. For this reason it is well 
to take with it some of the surrounding structures, e.g., the 266 
MANUAL OF HISTOLOGY. 
entire diaphragm, with the mediastinal portion, together with 
the heart and pericardium. 
It will be seen that the endothelium is composed of a great 
number of polygonal plates whose edges are glued together by 
a substance which has been stained brown or black by the sil- 
ver. Nuclei are seen in many of them, or they can be shown 
by staining with carmine or hsematoxylon. Small openings 
are to be seen in certain localities surrounded by cells of a 
more cubical form, with large, distinct nuclei. In other places 
small dark spots are seen between the cells. The openings are 
known as stomata, and communicate with lymphatic vessels 
running beneath the endothelium. The dark spots wz pseudo- 
stomata, and are similar in their nature to the pseudo-stomata 
of the alveoli and bronchial mucous membrane ; i.e., they are 
the ends of processes of the branched cells of the ground-sub- 
stance reaching up between the endothelial plates. In order 
to demonstrate the ground-substance or connective-tissue layer 
of the pleura, the fresh surface is carefully pencilled with a 
soft brush dipped in the fluid of the abdominal cavity, or in 
artificial serum. After washing with distilled water, the solu- 
tion of silver nitrate is poured over it, and it is treated as be- 
fore. On examination, the branched connective-tissue cells 
are seen communicating with each other by their processes. 
Blood-vessels and lymphatics are also seen, and in a favor- 
able place the endothelium of the latter is seen to be continuous 
with the branched cells. These cells line the cavities of the 
connective tissue, and belong to the lymph lacunar system. 
The lymphatic vessels accompany the blood-vessels, some- 
times ensheathing them. They are identified by the shape of 
their endothelial cells, which are wider and more polygonal in 
form than those of the veins. It will be seen from this descrip- 
tion that the serous membrane is a lymphatic structure. Its 
cavity communicates by means of the stomata with the lym- 
phatic vessels below, while, by means of the pseudo-stomata, 
it communicates with the lacunar spaces which are lined by 
the branched cells. To demonstrate the pulmonary pleura, , 
the lungs should be excised, moderately distended with air' 
(which is retained in them by ligature of the trachea), treated 
with silver nitrate, as already described, and then immersed in 
alcohol. After a few days sections are made parallel to the 
surface. THE RESPIRATORY TRACT. 
267 
If the lung be pencilled before it is treated with the silver 
solution the deeper structures can be examined. The sections 
should be mounted in glycerine with the external surface 
upward. The appearances here are similar to those already 
described. The capillary lymphatic-vessels communicate with 
the superficial pulmonary branches forming tlie subpleural 
lymphatics. 
The endothelial cells of the pulmonary pleura vary in 
shape according to the degree of distention of the lung. In 
the lung which has been inflated before hardening, the cells 
appear as flat plates, but in the atelectatic lung of a foetus, or 
the collapsed lung of an animal that has breathed, they are 
cubical or even columnar in shape. This difference is most 
marked in the guinea-pig, owing to the presence of a layer of 
muscular-fibres beneath the pleura of that animal. The tops 
of the cells which have this pyramidal shape are not flat as in 
true columnar epithelium, but rounded. This change of shape 
simply indicates that the cells accommodate themselves to 
changes of space. These changes, in a lesser degree, must be 
occurring constantly during life, with the movements of respi- 
ration. On the costal pleura, the stomata are only found in 
the intercostal spaces. 
Attached to the lower border of the lung are minute ap- 
pendages, the “pleural appendagesforming a sort of fringe 
connected with the pleura. Some are visible to the naked 
eye, some microscopic. The larger are made up of connective 
tissue and blood-vessels, and, exceptionally, nervous fibres in 
the larger ones. They are covered by round cells, sometimes 
resembling epithelium. The smallest ones are structureless, 
and in general have no epithelial covering.1 
BIBLIOGRAPHY. 
Coyne, P. Recherches sur I’anatomie normale de la muqueuse du Larynx. Ar- 
chives de Physiologic, p. 92.' Paris, 1874. 
Stirling. Nervous Apparatus of the Lung. Brit. Med. Journal. Vol. 11., p. 401. 
1876. 
Cadiat. Des rapports entre le develop, du pounaon et la structure. Jour, de 
I’anat. et de la Phys., No. 6, p. 591. 1877. And, Structure et devel. du 
poumon. Gaz. Med. de Paris, No. 17, p. 214. 1877. 
1 Luschka : Anatomie des Menschen, Bd. L, S. 298. 268 
MANUAL OF HISTOLOGY. 
Grancher. Note sur leslymphat. du poumon. Gaz. Med. de Paris, No. 9, p. 103. 
1877. 
Aeby. Die Gestalt d. Bronchialbaumes u. die Homol. d. Lungenlappen beim 
Menschen. Med. Centralbl., No. 16, p. 290. 1878. 
Seiler, C. Researches on the Anatomy of the Vocal Cords. St. Louis Med. and 
Surg. Journal, p. 333. April 5, 1880. And, Minute Anatomy of the Larynx, 
Normal and Pathological. Archives of Laryngology. Vol. L, Nos. 1 and 2, 
and to be continued. 1880. 
Kolliker, A. Bau der Lunge des Menschen. Yerh. der phys.-med. Gesellschaft 
in Wurzburg. N. F. XVI. 1-24. 1881. 
Pansch, A. Unteren u. oberen Pleuragrenzen. Arch. f. Anat. 111-121. 1881. CHAPTER XVIII. 
THE SKIN. 
A. R ROBINSON, M.D., 
Lecturer on Normal Histology in the Bellevue Hospital Medical College, New York. 
General plan of arrangement.—The integumentum commu- 
ne., or skin, forms the external covering of the body, which 
it mechanically protects, and at the same time is endowed 
with certain physiological functions. The surface of the skin 
in some parts of the body is smooth and soft; in others it 
is more or less uneven and rough. This latter condition 
depends upon the presence of pores, hairs, furrows, and 
ridges. The pores correspond to the surface openings of the 
hair-follicles, sebaceous and sweat-glands. The hairs vary 
in amount of development according to their situation. In 
the so-called hairy regions they are largest; other parts are 
provided only with a soft down (lanugo hairs). There are 
no hairs on the palms of the hands and soles of the feet, the 
dorsal surfaces of the terminal phalanges of the fingers and toes, 
the glans penis, and inner surface of the prepuce. The fur- 
rows are either long and deep, or short and superficial. The 
former are chiefly found in the flexures of the joints, and cor- 
respond to the folds in the derma produced by movements of 
the joint. The latter run between the papillary elevations, 
and, by crossing each other, divide the surface into a number 
of polygonal or lozenge-shaped fields. This division is well- 
marked on the backs of the hands. These superficial furrows 
are more developed on the extensor than on the flexor surfaces 
of the extremities, and in the lumbar region more than on the 
anterior surface of the abdomen. Their direction is dependent 
on the degree of the tension of the skin. The ridges correspond 
to the papillae, and are most developed on the palmar surfaces 
of the last digital phalanges. The color of the skin varies in 270 
MANUAL OF HISTOLOGY. 
individuals according to race, and in the same individual ac- 
cording to the part of the body. The dark skin of some races 
depends upon the presence of pigment in the cells of the rete 
Malpighii. In the white race, dark pigment is usually pres- 
ent in greatest quantity in the areolse of the nipples and in 
the scrotum and labim. 
General structure.—The skin is composed of the follow- 
ing parts: epidermis, corium, subcutaneous connective tissue, 
Fig. 114.—Diagrammatic perpendicular section through the normal skin: a, epidermis; f>, rete Mal- 
pighii; c, papillary layer; d, corium; e, panniculus adiposus; /, spirally bent end of excretory sweat- 
duct :p, straight portion of excretory duct of sweat-gland; h, coil of sweat-duct; i, hair-shaft; k, root 
of hair; I, sebaceous gland. After Keumann. 
blood-vessels, nerves, lymphatics, sweat and sebaceous glands, 
hairs, and nails. 
A perpendicular section through the skin shows (Fig. 114) 
three well-marked layers; the most superficial is called the 
epidermis proper, a, b ; the middle layer is the corium or cutis, 
d ; and the deepest layer the subcutaneous connective tissue, e. 
The limit of the epidermis at its place of union with the corium 
is sharply defined, but the corium and subcutaneous connec- THE SKIX. 
271 
tive tissue gradually merge into eacli other, the boundary be- 
tween them being only an artificial one. 
Commencing with the epidermis, we will describe in detail 
the minute structure of the different tissues and organs of the 
skin, omitting only the lymphatics. 
Description of the different layers.—The epidermis is 
generally subdivided into several layers, with specially distinc- 
tive names for each layer; but though such a division has 
some practical value, histologically it 
is incorrect, as the cells of the lowest 
layer are transformed, at some period 
of their existence, in their movement 
toward the free surface, into the cells 
of the other layers. Examination with 
high powers also shows that the chan- 
ges in the molecular constitution or 
chemical condition of the cells of the 
epidermis changes which produce 
differences in their appearance are 
Fig. 115.—a. rete cells; 
lar layer; c, stratum lucidum; d, 
corneous layer; e, inter-papillary rete 
Malpighii; f, cutis papilla. 
quite gradual. Consequently, sharply defined layers are not 
found. For practical reasons, however, it is well to adopt the 
usual classification. In Fig. 116 these layers are shown. 
Another division is into Malpighian and corneous layers 
only, the former comprising the rete and the granular layer, 
and the latter the stratum lucidum and corneous layer. The 
Malpighian layer, as compared with the corneous layer, pre- 
sents a more or less dark, granular appearance, while the latter 
is homogeneous, and its cells have a lamellar arrangement. 
The rete Malpighii consists of nucleated corpuscles, rich in 
protoplasm, granular in appearance, and disposed more or less 
in parallel strata, the elements of the different layers differing 
somewhat from each other as regards their size and shape. The 
lowest layer consists of columnar-shaped cells arranged pali- 
sade-like, with their long axes more or less perpendicular to the 
surface of the corium. Where the papillae are well developed, 
this perpendicular arrangement is not so marked. The base of 
some of these bodies terminates in a pointed extremity, which 
passes a short distance into the underlying corinra. Each of 
them has an oval nucleus. The cell-body consists of a small 
quantity of slightly granular, shining protoplasm. The cor- 
puscles of this layer are not united to each other by bands, as 272 
MANUAL OF HISTOLOGY. 
in tlie other layers. The next two or three strata consist of 
more or less polygonal-shaped bodies, each with a spherical 
nucleus. The cells of these layers are large, their contours 
sharpty defined, and they contain more or less pigment. It is 
this substance deposited in the corpuscles that gives the charac- 
teristic color to the different races of mankind. Their cell-bod- 
ies are larger in proportion to the nucleus than in the first layer. 
In the succeeding layers the cells increase in size and are more 
granular in appearance, the cells and nuclei become flatter as 
they approach the granular layer, and, finally, lie with their long- 
axes parallel to the surface. The granular structure which in 
the lowest layer is most marked around the nucleus, gradu- 
ally extends toward the margin of the cells, as the surface is 
approached, so that finally a clear area is seen around the 
nucleus, whilst the remainder of the cell-body is markedly 
granular. At the same time the cell-body becomes firmer and 
the nucleus smaller. 
All the cells of the rete Malpighii, except those of the first 
row, are united to each other by filaments (Martin, Bizzozero, 
Heitzmann), the so-called pricldes of Max 
Schultze (Fig. 116). These uniting filaments 
or bands vary much as regards their size 
and length in different parts of the body. 
They are most distinct wherever the Mal- 
pighian layer is well developed, but are 
thicker and longer in the lower row's of 
cells than in the upper. At the stratum 
lucidum they cease to exist. Between 
Fig. 116.—“ Prickle” cells 
of the rete. x 1600. 
neighboring corpuscles the length of these bands is in direct 
proportion to the distance between the borders of the cell- 
bodies. Hence, where three or four cells meet at one place, 
as in the centre of Fig. 116, the minute filaments are much 
longer than those uniting the bodies of closely adjoining cells. 
Examining these prickle-cells with the microscope, alternate 
dark and light bands are seen between the cell-borders. With 
a low power, these light bands appear to consist of spaces be- 
tween the connecting filaments, the dark lines being the con- 
necting filaments, but with a high power the latter can be 
recognized as spaces between the former. The light bands 
can be traced from the surface of one cell to the surface of 
another, whilst the dark lines are the spaces between these THE SKIN. 
273 
bands. These connecting cords sometimes divide and anas- 
tomose with each other, forming a sort of network between the 
cells. In this case, the dark spaces do not always extend 
from one cell-body to another, since they may correspond to 
the space between anastomosing filaments. These bands are 
therefore not the prickles of adjoining cells, which interlock 
with each other, but are true connecting filaments between 
cells of a common origin, and which have not yet become sepa- 
rated from each other. The connecting bands or fibres gradu- 
ally diminish in length and thickness from below upward, and 
finally cease to exist when the granular layer is reached. 
The spaces between the bands are filled with an inter- 
cellular albuminous substance, and they may be regarded as 
minute channels for the conveyance of nutriment to the cells 
of the epidermis. The above view of the “prickles” corre- 
sponds very closely with that held by Dr. Martin, and differs 
from that of later observers, who maintain that the dark lines 
are connecting bands, and the light lines the spaces between 
them. 
Owing to the close union of the Malpighian elements it is 
very difficult to isolate them. Perhaps the best way to accom- 
plish this result is by long immersion in iodized serum. Fig. 
117 represents a cell isolated in this manner. Here 
the bands have been torn apart and the cell-surface is 
studded with thorn-like projections. Hardening in 
chromic acid, with subsequent boiling in a moderately 
strong solution of potash, causes a separation of the 
ht-ibo- 
lated “prickle” 
«*u- 
mucous layer from the corium and a falling apart of the rete 
cells (Biesiadecki). The structure of the corpuscles, however, 
can be best studied when their normal relations with each 
other are preserved. Variations in the number of cellular lay- 
ers are of normal occurrence in the rete, although this portion 
of the skin shows the least variation as regards its thickness. 
The arrangement of the elements in these different strata is the 
same in all parts of the body, and appears to be independent 
of the thickness of this layer. 
As regards the direction of the long axes of the cells there 
is a gradual passing from the perpendicularly seated cells of 
the first layer to the horizontally lying cells of the uppermost 
row. The lower surface of the rete adapts itself to the upper 
surface of the corium, and between the papillae projects dowm 274 
MANUAL OF HISTOLOGY. 
ward and forms the interpapillary rete Malpighii. Wandering 
lymphoid cells are frequently present in the rete. They are 
especially numerous in some pathological conditions. They 
(Fig. 118) are elongated spindle-shaped bodies lying between 
the rete cells, and sending out minute processes. They color 
deeply in carmine, have a 
small nucleus, and are most 
numerous in the lower part 
of the rete mucosum. 
The granular layer (Fig. 
115, IS) consists of one or two 
strata of flattened, granular- 
looking bodies, which, in 
perpendicular section appear 
spindle - shaped, with their 
long diameter parallel to the 
free surface of the epidermis. 
In this stratum the cells are 
no longer connected with each 
other by bands, as in the pre- 
ceding layer. The nuclei of 
Pig. 118.—Horizontal section of skin through a 
papilla. The migrating cells are observed as dark 
bands between the epithelial cells and amongst the 
connective tissue of the papilla, Pagenstecher. 
these corpuscles are very distinct, and flattened in the same 
direction as the cell-body. The latter has a very coarsely gran- 
ular appearance, which is most marked near the nucleus, and 
gradually diminishes in degree as the periphery of the cell is 
approached. The structure of these bodies is best shown with 
hmmatoxylon. 
The stratum lucidum, also called the stratum of Oehl, is 
composed of at least three layers (Fig. 115, c). It presents a 
clear, homogeneous, or striated appearance. Within the flat- 
tened cells composing it, a staff-shaped nucleus is found. The 
cells of this layer are formed from those of the granular stra- 
tum. In their movement to the free surface the latter become 
less granular and the inter-granular substance grows more trans- 
parent and shining (Unna). This change from a granular to a 
homogeneous translucent appearance commences around the 
nucleus, whence it gradually extends to the periphery of the 
cell. The nucleus, also,’ usually becomes invisible. 
In vertical section the corneous layer appears (Fig. 115, d) 
to be composed of wavy fibres and horny, transparent cells 
of various sizes and shapes. This variation in bulk and form THE SKIH. 
275 
depends in great measure upon the thickness of the layer. 
The nearer we approach to the stratum lucidum, the more dis- 
tinct are the cells. If the layer is very thin the cells appear 
as elongated, flat, or curved bodies, giving to this part of the 
epidermis a fibrous appearance. When the corneous stratum 
is thick these cells present various forms and sizes. The cor- 
puscles of the lower layers color in carmine, are poly- 
gonal or spindle-shaped, and frequently contain a shrivelled 
nucleus. As the surface is approached they grow flatter and 
drier, are more bent upon themselves, and color less and less in 
carmine. The nucleus also becomes invisible. The most su- 
perficial layers are composed of elongated, flat, dried-up cells, 
the so-called epidermic scales. These bodies are best studied 
after they have been subjected to the action of liquor potassae, 
which causes them to swell up. 
The corpuscles of the stratum corneum are arranged in lay- 
ers as in the other parts of the epidermis, but the elements 
forming a layer are more closely united with each other than 
with those of the adjoining layers. Hence this stratum can be 
separated into lamellae, as occurs in some pathological states 
of the skin. It accompanies, for example, the formation of 
some vesicles, where the exuded liquid, prevented from pass- 
ing toward the surface, accumulates between the layers, and 
thus separates them from each other. 
The corneous layer participates in the elevations and de- 
pressions of the underlying layers. This causes the undulat- 
ing or wavy appearance of the lamellae, as observed in sections 
where the papillae are well developed. It varies greatly in 
thickness in different parts of the body, and reaches its great- 
est development on the palms of the hands and soles of the feet. 
Its thickness does not depend upon the rete Malpighii, as it 
sometimes forms a thin layer where the rete is thick, and vice 
versa. 
The subcutaneous connective-tissue layer of the skin con- 
sists principally of connective-tissue bundles, which, coming 
from the underlying fasciae of the muscles or from the peri- 
osteum, pass in an oblique direction to the corium. These 
fasciculi are generally cylindrical in form, and variable in size ; 
by their anastomoses or divisions they form larger or smaller 
networks, with correspondingly large or small interfascicular 
spaces. Generally large bundles anastomose with each other 276 
MANUAL OF HISTOLOGY. 
in tins layer, and hence a loose connective tissue is formed. 
Within this layer adipose tissue is found in greater or less 
quantity. are collected into masses or lobules, the 
number of cells which form a lobule varying greatly in num- 
ber. Each of these latter may be regarded as a fat-gland, as it 
is provided with an afferent artery, a capillary plexus between 
the corpuscles, and one or more efferent veins. Several lobules 
are sometimes united together in the form of an acinous-like 
gland, and are likewise seen to be surrounded by a general 
sheath of connective tissue. The individual fat-cells are round, 
flattened, polyhedral, or oval-shaped, the form depending upon 
the degree and direction of the pressure exerted upon them. 
Owing to the amount of fat-tissue so often found in this layer, 
it has been called the panniculus adiposus. Such fat-lobules 
are absent in the penis, scrotum, labise minorse, eyelids, and 
pinna. The corresponding spaces in these regions are tra- 
versed by fine connective-tissue bands or single fibrils. From 
this adipose tissue fat-columns pass upward in a somewhat 
oblique direction to the bases of the hair-follicles, especially 
to those of the fine hairs. Their long axes form a slight angle 
with the axes of the follicles, and they are nearly parallel to 
the erector pili muscles (Warren). In cases of starvation, in 
the so-called wasting diseases, and in all acute diseases at- 
tended with excessive loss of tissue, the fat-cells disappear to 
a greater or less extent. The skin, in such instances, becomes 
correspondingly flaccid and wrinkled. Adipose tissue gives to 
the skin its tension and fulness, and to the body its appear- 
ance of roundness or plumpness. Obesity consists in an exces- 
sive production of fat-cells. 
The interfascicular spaces differ in size in proportion to the 
amount of lymph present, and to the closeness of the anasto- 
moses between the bundles. In oedema the lymph-spaces are 
increased in size proportionately to the increased amount of 
liquid present. The interfascicular spaces all communicate 
with each other, as is shown by the rapidity with which a 
hypodermically injected liquid can be dispersed by manipu- 
lation. 
The connective-tissue cells of this layer and of the corium 
consist of branched cells (Ravogli) which surround the white 
fibrous bundles and send in processes between the fibres. Ac- 
cording to some observers, these cells are epithelioid in charac- THE SKIX. 
277 
ter. The elastic-tissue fibres are developed from the processes 
of the branched cells. 
Besides connective-tissue fibres and cells, lymphoid corpus- 
cles are present in this layer. They exist in greatest number 
near the blood-vessels and glands. In this situation they are 
of a roundish form, but in the parts distant from the blood- 
vessels they are more or less spindle-shaped, and are to be 
regarded as wandering cells. 
The convoluted part of the sweat-glands and the lower part 
of the hair-follicles of deep-seated hairs lie in this layer. 
Blood-vessels, lymphatics, and nerves are present. The 
blood-vessels are large, and after giving off small branches to 
the hair-follicles, sweat-glands, and fat-lobules, pass upward 
to the corium. 
Pacinian corpuscles are found in connection with some of 
the nerves. For a description of these bodies the reader is re- 
ferred to the article on the nerves. 
The principal part of the corium consists of white fibrous and 
elastic tissue, the latter increasing in amount with advancing 
age. Here the white fibrous tissue forms a much denser, firmer 
structure than in the previous layer. It consists of deep 
oblique, and superficial horizontal bundles. The latter com- 
prise fine bundles of connective tissue which ran parallel with 
the surface of the skin, and by their division and anastomoses 
form a very fine network with small interfascicular spaces. 
From this layer bundles pass upward into the papillae, and 
these form a second denser network. The deeper layer is 
formed by a continuation upward of the subcutaneous con- 
nective-tissue bundles. These pass upward in an oblique direc- 
tion, and as they reach the corium divide into fasciculi. Here 
they continue to divide and anastomose with each other and 
with fibres from the horizontally running bundles. The anas- 
tomoses are very close ; hence, the corium is formed of a dense 
network of connective tissue, except in those parts which are 
traversed by blood-vessels, lymphatic vessels, nerves, hair-folli- 
cles, and sebaceous and sweat glands. Immediately around 
the hair-follicles, sweat-ducts, and sebaceous glands the con- 
nective tissue is dense, and the fibres run parallel with the di- 
rection of the organs. Owing to the greater size of the connec- 
tive-tissue bundles in the lower part of the corium, and the 
consequent looseness of the network formed by their anasto- 278 
MANUAL OF HISTOLOGY. 
Moses, this part of the corium has been called the pars reticu- 
laris corii, in contradistinction from the finer network formed 
in the upper part, to which the name pars papillaris has been 
applied. But neither between these two parts nor between the 
subcutaneous layer and the corium is there any sharp dividing 
line, the transition being a gradual one. 
As already mentioned, the size of the interfascicular spaces 
depends upon the closeness of the anastomosis between the 
bundles and fibres. The direction of the bundles corresponds 
with that taken by the blood-vessels. 
The connective-tissue corpuscles of the corium resemble 
those found in the subcutaneous layer, and also bear the same 
relation to its connective-tissue bundles. From the upper 
portion of the corium fibres pass upward to make the papillae. 
The form of the papillae is very variable in different parts of 
the body. Where they are most developed, as on the inner 
surface of the terminal phalanges of the fingers and toes, they 
are conical in shape. In some other regions they form only 
slight elevations on the corium, giving a wave-like appearance 
to its upper surface. They consist of a close network of white, 
fibrous connective tissue combined, especially in the central 
part of the papilla, with a large number of elastic fibres. Those 
papillm which contain tactile corpuscles are called nerve-pa- 
pillae. 
The corium is separated from the stratum mucosum by a 
thin, transparent basement-membrane, containing oval nuclei. 
Its under surface is not sharply defined, and from it prolonga- 
tions pass upward between the cylindrical cells of the rete, 
giving this surface a notched appearance similar to that ob- 
served on the inner margin of the internal sheath of the hair- 
follicle. 
Elastic fibres are present in large numbers in the corium, 
especially in its upper paid, where they form a network around 
and between the white fibrous tissue-bundles. In the lower 
part of the corium they form a large network, which becomes 
finer as the surface is approached. The number of elastic 
fibres increases with advancing years. With this increase of 
elastic fibres there is a corresponding decrease of the white 
fibrous connective-tissue cells (Ravogli). Numerous wander- 
ing cells are met with in the corium, especially in the vicinity 
of the blood-vessels and glands. Hair-follicles, sebaceous THE SKIN. 
279 
glands, sweat-ducts, nerves, lymphatic vessels, and non-striated 
muscles are also present in tins layer. For a fuller descrip- 
tion of the intimate structure of the connective-tissue bundles 
and cells, see the subject of connective tissues. 
Blood-vessels.—Only the corium and subcutaneous tissue 
are provided with blood-vessels. The arterial blood-vessels 
supplying the skin form two parallel horizontal layers, a su- 
perficial and a deep one. The deep layer lies in the subcuta 
neons tissue, and consists of large vessels running parallel to 
the general surface. From this horizontally lying deep layer, 
branches are distributed to the sweat-glands and fat-follicles of 
this region. The principal branches, however, pass perpendicu- 
larly or obliquely upward through the corium to its upper part, 
and form immediately beneath the papillae (after free branch- 
ing and anastomosis) a superficial horizontal layer, the stratum 
subpapillare. From the vessels ascending 
through the corium branches are given off to 
the hair-follicles, sebaceous glands, and gen- 
eral tissue of the corium. From the stratum 
subpapillare small branches pass upward into 
the papillae, where they become capillary ves- 
sels, which proceed to the summit of the 
Fig. 119. Blood-ves- 
sels of the papilke: a, 
stratum subpapillare; b, 
papilla. 
papilla. (See Fig. 119.) Before reaching this point, however, 
they frequently divide into two or more branches. Frequently, 
those papillae in which tactile corpuscles are seated have no 
blood-vessels. 
The veins are arranged on the same plan as the arteries: 
they form a superficial and a deep layer, and have their origin 
in the papillae. From the superficial layer larger vessels pass 
downward, receiving blood from the veins of the hair-follicles, 
sebaceous glands, and the general tissue of the corium, thus 
forming a deep subcutaneous layer or venous network. 
Nerves.—Medullated and non-mednllated nerve-fibres are 
present in the skin. They are found in combination in the nerve- 
trunks of the subcutaneous tissue, the medullated fibres being 
most numerous in those regions of the skin where the Pacinian 
and tactile corpuscles are most abundant. In the subcuta- 
neous connective-tissue region, and in the lower part of the 
corium, some nerve-fibres leave the nerve-trunks and pass to 
the glands, blood-vessels, and Pacinian corpuscles found in this 
region. In the corium some of the fibres lose their medullary 280 
MANUAL OF HISTOLOGY. 
sheath, and afterward continue their course as non-medullated 
fibres. The nerve-bundles pass upward in a more or less oblique 
direction from the subcutaneous connective tissue through the 
corium to the subpapillary network of blood-vessels, around 
which they form a plexus. From this subpapillary plexus 
medullated fibres run upward and pass into the tactile cor- 
puscles. 
The non-medullated nerve-fibres form a reticulum around 
the blood-vessels of the pars reticularis corii and the capilla- 
ries of the papillae. They consist of thick or fine, smooth, 
varicose fibres with numerous nuclei. These fibres proceed 
from the network around the subpapillary blood-vessels up- 
ward toward the rete Malpighii, and either pass directly into 
the rete or run for a short distance parallel to its under sur- 
face, and then finally enter that layer. Within the epider- 
mis the fibres run between the cells and terminate in a manner 
not yet definitely known. Their mode of division and termina- 
tion within the epidermis is probably similar to that occurring 
in the cornea. Within the papillae the nerve-fibres frequently 
divide before entering the rete. 
The manner of distribution and termination of the non- 
medullated nerve-fibres can only be studied successfully in tis- 
sue stained with gold chloride. The tissue must be fresh, and 
a weak solution of the gold chloride used. When sufficiently 
stained the tissue is placed in distilled water slightly acidu- 
lated with acetic acid and exposed to the light. 
The Pacinian corpuscles are found in greatest abundance in 
the skin of the fingers, toes, palm of the hand, sole of the foot, 
but also occasionally in other regions of the skin. Their struc- 
ture is described in the article on the nervous system. 
Tactile corpuscles.—As already mentioned, some of the 
medullated nerve-fibres forming the plexus surrounding the 
subpapillary blood-vessels, pass upward and enter the so-called 
tactile corpuscles. These corpuscles are generally seated in the 
papillae, but occasionally they are found in the subpapillary 
region, i.e., the upper part of the corium. The majority of 
the papillae containing such corpuscles have no blood-vessels. 
They are more or less oval in form, and can be easily recog- 
nized under the microscope by their dark contours and by the 
oblique lines produced by the transversely running connective- 
tissue fibres of the outer surface of the corpuscle. There may THE SKIN. 
281 
be two or more corpuscles within a single papilla (Thin), but 
each corpuscle invariably has a special nerve passing into it. 
Frequently, however, an appearance as if two corpuscles were 
present is produced by a single corpuscle having the shape 
of a figure 8. The medullated nerve-fibre, in passing to the 
corpuscle, pursues a more or less curved course, and usually 
enters it at or near its lower extremity. It may, however, en- 
ter at any part of the corpuscle, and sometimes winds around 
it for a considerable distance before entering. After entering 
the corpuscle the medullary sheath is lost, and its course now 
becomes difficult to pursue, except in the case of very small 
or young corpuscles. The intimate structure of these bodies 
and the arrangement of their formative elements are still mat- 
ters of discussion and uncertainty. The external portion of a 
corpuscle appears to be composed, in great part, of larger or 
smaller bundles of white, fibrous connective tissue anastomos- 
ing with each other and running transversely, or in a spiral 
direction, to the long diameter of the corpuscle. This part 
of the corpuscle differs, as regards 
irregularity of surface, with the size 
and the manner in which the fibrous 
fascicles divide and anastomose. The 
coarser the bundles and the anastomo- 
ses the more irregular will be its sur- 
face. Between the fibres are found 
oval or round bodies which color deep- 
ly in gold, and have been regarded as 
elastic elements (Thin). Other obser- 
vers consider them as connective tis- 
sue, or nerve-fibres. Some of these 
bodies undoubtedly represent the 
nerve-fibre in transverse or oblique 
section ; for the nerve pursues a more 
Pig. 120.—Tactile corpuscle, show- 
ing termination of nerve : a, corpuscle; 
6, nerve, cut obliquely; c, apparent 
division of nerve-fibre; e, similar ap- 
pearance as at c; /, blood-vessel; g, 
rete cells; h, nerve-fibre cut trans- 
versely. 
or less zigzag course within the corpuscle, and, consequently, 
a section of the body will probably show the nerve cut across 
in one or more places (Fig. 120, b). The arrangement of the 
elements forming the central part of the corpuscle is not yet 
thoroughly understood. These bodies have hitherto been 
usually regarded as end-organs—that is, it has been believed 
that the medullated nerve-fibre terminates within the corpuscle, 
hence the name, tactile corpuscle. Observers, however, have 282 
MANUAL OF HISTOLOGY. 
not agreed as to the mode of termination of the nerve, and 
some have maintained that it has not been clearly proven that 
they really do terminate in the corpuscle. From specimens 
which I have recently obtained I am led to believe that the 
nerve does not terminate within the corpuscle, but passes on 
into the rete Malpighii. 
The best corpuscles for studying this point are small ones, 
as in these a section is more likely to include the entire upper 
extremity of the corpuscle at the same time that it is not too 
thick for examination with the microscope. Even in a small 
corpuscle, however, unless the nerve passes onward in a direct 
level with the corpuscle after leaving it, the nerve, in a vertical 
section, will be cut across, and it will, therefore, be impossible 
to follow it from the corpuscle into the rete. I believe the 
nerve frequently, perhaps generally, changes the direction of 
its course after leaving the corpuscle, and hence we often see 
a transverse section of the nerve at the upper extremity of the 
corpuscle. In Fig. 120 is seen the location of the termination 
of the nerve-fibre as observed in one of my specimens. In 
one place its course between the rete cells was very indistinct, 
though recognizable. The nerve passed obliquely upward be- 
tween the cells of the rete to the space between the second 
and third rows of cells, where it assumed a longitudinal di- 
rection. At the commencement of the curve the nerve ap- 
peared to have undergone division (c). After passing a short 
distance horizontally it ran almost perpendicularly downward, 
and near g was lost to view. At eit appeared to have again 
undergone division. According to the appearances here fig- 
ured the corpuscles are not the structures in which the nerve 
terminates, the latter passing from the corpuscle (as a non- 
inedullated fibre) into the epidermis, where it divides and 
probably terminates in the same manner as the other nerves. 
This mode of termination cannot be regarded as strange, as we 
have already seen that some medullated nerve-fibres lose their 
medulla deeper in the corium, and afterward continue their 
course as non-medullated fibres. 
The tactile' corpuscles are found in greatest number in 
the ends of the fingers. They are also present on other parts 
of the hand and on the foot, and sometimes in the lips and 
nipple. 
The sweat-glands.—The sweat-glands—glandules sudor if- THE SKIX. 
283 
ercB—are found in the skin of all parts of the body except that 
of the glans penis and margin of the lips. They are most nu- 
merous in the palms of the hands and the soles of the feet, 
where they number, according to Krause, 2,685 to 2,736 to the 
square inch. 
A sweat-gland is composed of two parts, viz.: the gland 
proper, or secreting part, and an excretory duct. The gland 
proper lies in the subcutaneous tissue, 
and consists of the lower part of the sweat- 
gland rolled and coiled upon itself into a 
more or less globular form, the tube ter- 
minating in a cul-de-sac, the blind extrem- 
ity generally lying in the centre of the coil. 
The diameter of the secreting tube is 
greater than that of the excretory duct. 
The former is composed of secreting cells, 
unstriped muscular fibres, and a basement- 
membrane. The cells (glandular or secret- 
ing epithelial cells) are polygonal in shape 
and form only a single layer. They are 
strongly granular in appearance and have 
a very distinct nucleus. Their basal end 
is sometimes notched where they are in- 
serted into the basement-membrane. In 
normal conditions these bodies are never 
found in the sweat-fluid, but in inflamma- 
tion of the surrounding connective tissue 
they frequently become separated from 
Fig. 121.—Lower part of a 
sweat-gland: a, excretory duct; 
b, coil of secreting-tube; c, se- 
creting-tube cut transversely; 
d, blood-vessels cut across. 
the basement-membrane. Oil-globules are frequently seen in 
the cell-body, and are to be regarded as a normal constituent 
of the corpuscles. 
The basement-membrane is a thin, transparent structure, 
lying beneath the epithelial cells and composed of flat endo- 
thelial elements, as shown by the action of silver nitrate on 
the fresh tissue. 
In certain glands, especially those of the axilla, a layer of 
unstriped muscular fibres is found external to the basement- 
membrane. These fibres are present in only a small number 
of sweat-glands ; by their contraction they assist in the expul- 
sion of the secreted sweat. They are the smallest unstriped 
muscular fibres met with in the human body. 284 
MANUAL OF HISTOLOGY. 
The sweat-glands are surrounded by a somewhat loose 
fibrous connective tissue, from which fibres pass inward and 
form a closer network between the coils of the gland. Some 
of the fibres run parallel, and others transversely or obliquely, 
to the long diameter of the convoluted tube. A large number 
of lymphoid cells are always present in this interglandular 
connective tissue. The sweat-glands are richly supplied wuth 
blood-vessels. 
The excretory duct passes upward from the gland proper 
in a more or less vertical direction through the different layers 
of the skin to its free surface, where it opens with a funnel- 
shaped orifice. In passing through the corium it pursues a 
straight or slightly wavy course, and enters the lowest part 
of the inter-papillary rete. The structure of this part of 
the excretory duct differs from that of the gland proper, in 
the shape of the cells, the absence of muscle-fibres, and the 
presence of a cuticula. This cuticula lines the inner surface 
of the epithelial coating and limits the lumen of the duct. 
As the rete Malpighii is entered there are generally two or 
more layers of cells lining the duct, the number increasing 
as the rete is approached. The transition from secreting cells 
to lining cells is gradual, so that the presence of a cuticula 
decides the nature of the tube. The basement-membrane 
corresponds in structure wuth that of the gland proper. The 
fibres of surrounding connective tissue run parallel with the 
duct. 
As the duct approaches the rete Malpighii its epithelial 
cells increase in number and form two or more layers, which 
are really only a continuation downwuird of the cells of the 
rete. When the duct enters the rete it loses its basement- 
membrane and is formed only of the cells of the mucous layer, 
which have become more or less flattened and spindle-shaped. 
The direction of the duct through the rete is sometimes straight 
and sometimes spiral. 
In passing through the stratum corneum the duct pursues 
a spiral direction on account of the horizontally flattened cells 
of this layer (see Fig. 114, /), and the number of spirals pres- 
ent depends upon its thickness. The largest number is found 
in the palms of the hands and soles of the feet, where it may 
amount to twenty or more, whilst on some parts of the body 
there is not even a single complete spiral. The wall of the THE SKIN. 
285 
duct is formed of the cells of the corneous layer, and the duct 
opens on the free surface at the summit of the ridges. 
The formation of the sweat-glands commences in the fifth 
month of foetal life by the pushing of epithelial cells from the 
rete mucosum into the cutis. In the seventh month the epi- 
thelial cells form a canal, and the lower end of the tube be- 
comes dilated and somewhat twisted. In the ninth month the 
tube is coiled upon itself to form the gland proper. According 
to Ranvier, who believes that the muscular fibres lie between 
the epithelial cells and the basement-membrane, the muscle- 
cells arise from the external cells of the gland proper by a 
process of simple differentiation. The lumen of the tube is 
formed not by a softening down of the central cells, but by the 
formation of the cuticula, which occurs first at the lowest part 
of the excretory duct (Ranvier). 
The sebaceous glands.—The sebaceous glands are seated in 
the corium and are in close connection with the hair-follicles. 
When the hairs are large the sebaceous glands appear as ap- 
pendages to the hair-follicles into which their ducts enter, and 
by which their contents are carried to the free surface. As 
regards the small downy, or lanugo hairs, they may be said to 
open into the ducts of the sebaceous glands, the ducts of the 
latter having in this case a much greater diameter than in the 
previous instance. They also open directly on the free surface. 
The sebaceous glands are almost without exception acinous 
glands, the number of lobules forming a single gland, ranging 
from two to twenty, or more. The largest glands are seated in 
the nose, cheeks, scrotum, about the anus, and in the labia. 
Occasionally the secreting portion of a sebaceous gland con- 
sists of a single tubule, or sac, whose duct opens into a hair- 
follicle. 
Every sebaceous gland is composed of two parts, viz.: the 
secreting portion, or gland proper, and the duct. The gland 
proper is formed of a basement-membrane, or sac, externally, 
and secreting cells, or their products, internally. The basement- 
membrane is continuous with the transparent membrane de- 
scribed as lying directly beneath the rete Malpighii and above 
the corium, and has a similar structure. This basement-mem- 
brane passes from the sebaceous gland to the hair-follicle, where 
it forms the inner layer of the hair-sac. The membrane of the 
sebaceous gland is surrounded externally by bands of dense 286 
MANUAL OF HISTOLOGY. 
connective tissue containing blood-vessels, nerves, and lym- 
phatics. 
The secreting part of the gland (Fig. 122, t) is composed of 
layers of cells very similar to the cells present in the epidermis, 
those of the outer part corresponding to the cells of the rete 
Malpighii. The first layer of cells, viz., those seated upon the 
basement-membrane, is composed of cylindrical, or cubical, 
cells, like those of the rete. They have a very distinct nucleus. 
Further inward the cells become larger, more or less polyhe- 
dral in form, and contain fat, which obscures or conceals the 
nucleus. If the fat is extracted the nucleus can be seen lying 
in the centre of the space previously occupied by the fat. The 
nearer the centre of the gland the greater the quantity of fat 
in the cells. The most external layer of cells contains but a 
small quantity. In the centre of the gland, free fat, fat-crys- 
tals, and remnants of epithelial cells are found. 
The duct of the sebaceous gland is similar in structure to 
that of the gland proper. Externally is the basement-mem- 
brane, lined inside by epidermis-like cells, containing more or 
less fat, and enclosing a central cavity through which the seba- 
ceous matter passes to reach the hair-follicle or the free surface. 
The contents of this canal are fat, fat-crystals, and remnants 
of epithelial cells. Internal to the polyhedral cells of the duct 
are the cells of the corneous layer of the epidermis, which di- 
minish in number in proportion to the distance from the free 
surface. 
In large hairs the duct of the sebaceous gland opens at an 
acute angle into the hair-follicle near its upper third, and the 
gland proper lies about on a level with the middle third of the 
hair-follicle. 
At the place of union of the hair-follicle with the sebaceous 
gland the cells of the latter become continuous with the cells 
of the external root-sheath of the hair. This latter root-sheath 
becomes continuous above with the cells of the rete Malpighii. 
The development of the sebaceous glands commences at the 
third month of foetal life, as a projection downward and out- 
ward of a part of the external root-sheath of the hair, at the 
place where the future opening of the duct will be situated.1 
It consists, at first, entirely of epithelial cells, which by sub- 
sequent multiplication and further projection downward, form 
the sebaceous gland. THE SKIN". 
Muscles.—Striated and non-striated muscles are present in 
the skin. The former are found both in the smooth and in the 
bearded parts of the face, and also in the nose. They arise from 
the deeply seated muscles, and passing vertically, or more or 
less obliquely, upward between the hair-follicles and the glands 
of the skin, terminate in the corium. 
The non-striated muscles are very numerous, and run either 
in a parallel or in an oblique direction to the general surface 
of the skin. Those lying parallel with the general surface run 
either in a straight or circular direction. When they run in a 
straight direction and anastomose with each other they form 
a network, as in the scrotum, prepuce, and perinmun). Tlie 
straight running muscles are found, especially in the scalp and 
in the axilla, both above and below the sweat-glands. Where 
the muscles have a circular course, as in the areola of the nip- 
ple, a continuous ring muscle is formed. 
The majority of the muscles running in an oblique direc- 
tion have a special relation to the hair-follicles. The muscle 
arises from the internal sheath of the hair-follicle and passing 
obliquely upward, skirting the lower surface of the sebaceous 
gland, terminates in the upper part of the corium (Fig. 122, n). 
Occasionally two muscles, situated on opposite sides, arise 
from a single hair-follicle sheath. A muscle in its course up- 
ward frequently divides into two or more bundles, these sec- 
ondarjr bundles afterward pursuing different directions from 
each other, and sometimes uniting with fibres from other mus- 
cles, form a network in the corium. Sometimes an entire 
muscle, or a secondary bundle, passes upward into a papilla 
of the cutis and is inserted into the dense fibrous connective tis- 
sue directly beneath the rete Malpighii. Occasionally several 
secondary bundles run nearly parallel with each other and ter- 
minate either separately in the corium, or conjointly, after 
uniting. 
The skin is provided with other muscles which have no spe- 
cial relation to the hair-follicles, but pass more or less verti- 
cally upward from the subcutaneous tissue to be inserted in 
the corium. 
The number of muscles present in the skin varies in differ- 
ent regions of the body. They are most numerous in the scro- 
tum. The order of frequency in the different parts of the body 
is as follows : Scrotum, penis, anterior part of perinseum, scalp, 288 
MANUAL OU HISTOLOGY. 
forearm, thigh, arm, shoulder, forehead, abdominal wall, ax- 
illa, fore-leg, face, volar and dorsal surfaces of the hands and 
feet (Neumann). They are less 
developed on the flexor than on 
the extensor surfaces. 
The size of the individual mus- 
cles varies according to the person 
and the region of the body. It is 
impossible, therefore, to recognize 
with certainty a slight hypertro- 
phy or atrophy of these structures. 
For information as to their 
blood, lymph, and nerve supply 
see the article on unstriped muscle. 
The hair.—The parts to be 
studied in connection with the hair 
proper are the hair-follicle and 
the hair-papilla. The hair proper 
is a cylindrical structure seated 
within the hair-follicle and upon 
the hair-papilla. Its base lies 
embedded either in the subcuta- 
neous connective tissue or in the 
corium. The portion of the hair 
proper within the follicle is called 
the root of the hair, and the re- 
mainder the shaft of the hair. 
The true hair-follicle includes all 
that part of the hair-sac below 
the place where the sebaceous 
duct enters the hair-follicle. It 
is of very variable size and con- 
sists of a blind extremity and a 
funnel-shaped orifice (a). The 
follicle is narrowed just below 
this funnel-shaped orifice and 
forms the so-called neck of the 
hair-follicle (5). This is the nar- 
rowest part of the follicle, and 
Pig. 122.—Hair from beard: a, canal of 
exit; 6, neck of hair-follicle ;c. lower part of 
hair-follicle ; d, external sheath of hair-folli- 
cle ; e, internal sheath of hair-follicle; /, ex- 
ternal root-sheath of hair; £/, internal root- 
sheath of hair; h, cortical substance; k, me- 
dulla of hair; I, root of hair : m, fat-cells; n, 
arector pili; o, papillae of skin ; p, papilla of 
hair: s, rete muoosum; i, sebaceous gland ; 
ep, stratum corneum, which is continued into 
the follicle. Biesiadecki. 
is the place where the duct of the sebaceous gland enters. 
From the neck downward the hair-follicle increases in size, be- THE SKI IST. 
289 
ing largest at its lower end, where it rests upon the papilla. 
Below the neck we have the follicle and the root of the hair. 
The follicle consists, anatomically, of three layers: the ex- 
ternal, middle, and internal hair-follicle sheaths. 
The external sheath of the follicle {d) consists of connective- 
tissue fibres, which extend from the upper corium and running 
parallel to the long axis of the hair-follicle surround the base 
of the latter and send some fibres into the papilla. The fibres 
forming the inner portion of this sheath are arranged much 
more closely than the fibres forming the external part. In this 
latter situation there is no sharp dividing line between the 
sheath and the surrounding loose connective tissue, the one 
merging gradually into the other. Within this sheath run the 
special blood-vessels and nerves of the hair-follicle. 
The middle sheath of the follicle consists of a few transverse- 
ly running connective-tissue fibres, between which lie oval nuclei 
imbedded in a granular substance. These latter, probably, 
represent organic muscle-cells. This sheath begins at the neck 
of the follicle and, surrounding its lower part, passes also within 
the papilla. In this tissue is a close network of blood-capil- 
laries. Nerves have not as yet been observed, though they 
probably exist. 
The internal sheath of the follicle is composed of a trans- 
parent, homogeneous-looking structure—the basement-mem- 
brane, which is not altered by the action of acids or alkalies. 
It is merely a continuation of the transparent membrane found 
between the rete mucosum and the corium, which it resembles 
in its structure. It contains neither blood-vessels nor nerves. 
The external surface is smooth, but the internal surface has a 
notched appearance, caused by prolongations inward between 
the cells of the external root-sheath of the hair. 
The hair-papilla is formed from the stroma of the hair-fol- 
licle sheaths, especially from that of the middle sheath. It 
consists of connective-tissue fibres, between which are found 
numerous round cells. The internal follicle sheath separates 
it from the root of the hair. Within the papilla are found 
one or more arteries and veins besides non-raedullated nerve- 
fibres. The papilla has a narrow neck, a thicker body, and 
a conical apex. It is, on an average, twice as long as it is 
broad. The breadth is in direct proportion to the length of 
the hair. 290 
MANUAL OF HISTOLOGY. 
The hair-follicles and hairs stand obliquely to the surface 
of the skin. Their direction varies in different regions of the 
body, and depends upon the structure of the connective tissue 
of the corium and the degree of its tension. The contents of 
the hair-follicles are the external and internal root-sheaths and 
the hair proper. 
The external root-sheath (/) adjoins the inner follicle sheath 
and consists of rete cells continued into the hair-follicle from 
the general rete mucosum layer of the skin. This sheath does 
not extend as far as the lowest part of the follicle, generally 
ending about on a level with the apex of the hair-papilla, 
though it is sometimes continued as far as the base of the 
latter. All the different kinds of cells present in the epi- 
dermis are also found in this sheath as far down as the neck 
of the follicle. Beyond this point the cells of the rete Mal- 
pighii only enter into its formation. The number of rows of 
cells forming it is subject to great variation. It diminishes 
as the base of the follicle is approached, so that finally the 
sheath is formed of a single row of cells. At the neck of 
the follicle the sheath is usually narrower than directly above 
or below this point, owing to the pressure to which the cells 
are here subjected. Their form is very similar to that of 
the corresponding cells of the rete mucosum. Those of the 
deepest row are cylindrical, and those of the second row 
polyhedral. In the other rows the cells are flatter, with the 
exception of the most internal row, where all these bodies 
are large and round. This last row is not subject to the same 
changes as the others, and has been considered to be a distinct, 
independent row of cells (Unna), The nuclei of all the cells 
color strongly in carmine, hsematoxylon, etc. Nerve-fibres have 
been described as running between the cells of this sheath 
(Langerhans). 
The internal root-sheath {g) lies in direct contact with the 
external root-sheath. It is usually described as consisting of 
two layers, an external one, also called the sheath of Rente, 
and an internal one, or sheath of Huxley. Strictly speak- 
ing, this division into two sheaths is incorrect, as it has been 
shown (Unna) that the two sheaths supposed to be distinct 
have a common origin from the cylindrical epithelial cells sur- 
rounding the neck of the hair-papilla at its lowest part. These 
cells color very deeply in carmine. They surround the root of THE SKIN. 
291 
the hair like a sheath. In the thick hairs of the beard the 
sheath consists of three rows of cells—the external row, after- 
ward forming Henle’s sheath, and the two inner rows of cells, 
the sheath of Huxley. In finer hairs there are only two layers of 
such cells. These corpuscles are originally similar in structure, 
having a very granular appearance and an indistinct nucleus. 
The sheath is thinnest where the hair-papilla is broadest. 
The cells of the external layer (Henle’s) become paler and lose 
their nuclei earlier than those of the inner layer, so that on a 
level with the upper part of the papilla there is a marked dif- 
ference in the appearance of the two layers of cells. Formerly 
it was supposed (Biesiadecki) that Henle’s sheath commenced 
at this point and was a product of the external root-sheath, 
corresponding in this respect with the corneous layer of the 
epidermis. The cells of Huxley’s layer afterward become 
transparent also and lose their nuclei, and can then no longer 
be distinguished from the cells of Henle’s layer. The internal 
root-sheath is now formed of transparent, non-nucleated, spin- 
dle-shaped, or flattened bodies which surround the hair-cuti- 
cula as far as the neck of the hair-follicle. 
Within the internal root-sheath lies the hair proper, which 
consists of a knobbed extremity, the root of the hair, and a 
cylindrical portion, the shaft. Between the hair proper and 
Huxley’s layer lies the hair-cuticula. This latter consists of 
two rows of cells—an external one, closely united with Hux- 
ley’s layer, and an internal one, united to the hair-shaft. They 
both arise from the cylindrical cells seated directly upon the 
upper part of the neck of the papilla to the inside of the cells 
producing the internal root-sheath. The cells of the inner 
cuticula (the hair-cuticula) are at first round, then cuboid in 
form, and finally, long and prismatic. Above the papilla they 
are more elongated, and commence to overlap the cells above 
them. With the flattening out of the cells they assume the 
form of rhomboid or ovoid plates, so that above the free sur- 
face of the skin one cell partly covers the bodies of four or five 
others. At first they lie perpendicularly to the long axis of the 
hair, but afterward they are parallel with it. Above the papilla 
they form spiral rows around the hair shaft, so that in any sec- 
tion of this part the cells appear of a long cylindrical or spin- 
dle-shape. The external or root-sheath cuticula consists at 
first of round cells which afterward flatten and lie in the same 292 
MANUAL OF HISTOLOGY. 
direction as the flat cells of the previous cuticula. Before the 
internal root-sheath is pierced by the growing hair both cuti- 
culse are composed of similar cells. 
The root of the hair consists of cells closely resembling 
those of the rete mucosum. The corpuscles seated directly 
upon the basement-membrane of the papilla are cylindrical in 
form, and the more superficial ones polyhedral. Near the hair- 
shaft they are spindle-shaped and firmer. The lower cells of 
the central part of the root of the hair are round, have a large 
nucleus, and a small amount of cell-body. Afterward the cell- 
body increases in size. They bear a close resemblance to em- 
bryonic corpuscles and color deeply in carmine. In the upper 
part of the root of the hair the cells of the external part of the 
bulb become oblong, spindle-formed, and, finally, are lengthened 
out like fibres, in which condition they 
form the fibrous part of the hair-shaft. 
The pigment in the root of the hair is 
sharply limited externally by the cells 
of the hair-cuticula. 
The shaft of the hair consists of a 
central part or medulla, and a fibrous 
portion covered by the hair-cuticula. 
The medulla consists of polyhedral 
cells containing fat and pigment gran- 
ules. Toward the free end of the hair 
it becomes smaller, and finally ends 
near the point. The fibrous portion 
forms the principal part of the hair- 
shaft, and consists of flattened, fusi- 
form cells, containing numerous spin- 
dle-shaped granules. 
Fig. 133.—Transverse section of 
the hair beneath the neck of the hair- 
follicle : «, external sheath of the hair- 
follicle ; b, transversely cut blood-ves- 
sels ; c, inner sheath of hair-follicle; 
d. basement-membrane of hair-follicle; 
e, external root-sheath cells of Hen- 
le‘s layer ; g, cells of Huxley's layer; 
h, cuticula; I, hair-shaft. Biesiadecki. 
From the foregoing description of 
the hair and its follicle it is clear that 
in transverse sections it will present 
different appearances, according to the 
situation in which the section is made. A description of trans- 
verse sections in different regions of the hair is here unneces- 
sary. We reproduce, however, above, a figure from Biesiadecki, 
which will sufficiently explain this matter (Fig. 123). 
A hair increases in length by the formation of new elements 
in its root, and they, by their subsequent elongation and move- THE SKIN. 
293 
ment upward, push the shaft of the hair and its cuticula before 
them. The structure of an adult hair can be best studied in 
the stiff, gray hairs of the beard. For the study of the origin 
of the root-sheaths young hairs should be chosen. There are 
still many points in regard to the structure of the skin and its 
appendages which appear to be rather doubtful, owing to our 
insufficient knowledge. The first development of the hair-fol- 
licle takes place at the end of the third or beginning of the 
fourth month, and it originates as a projection downward of 
the cells of the rete mucosum. It is seen as a finger-shaped 
collection of rete cells surrounded by the connective tissue of 
the corium. The papilla is formed later. By the numerical 
increase of round cells the follicle is enlarged, and the external 
cells are pushed sideward, thus forming the external root- 
sheath. The origin of the other parts of the hair has been 
already described. The first hairs are always of the lanugo 
kind—that is, they are fine hairs, with a very short hair-folli- 
cle. In certain regions the hairs always remain fine ; in other 
parts they give place to thicker ones. In the latter case a pro- 
longation downward of the external root-sheath takes place. 
This forms the hair-papilla. The papilla of the first hair atro- 
phies, the hair falls out, and its place is occupied by a thick 
hair. The permanent hair grows to a certain length, which 
varies in different persons and in different parts of the body. 
If a hair has reached its proper term of existence it falls out 
and is replaced by a new hair, which grows from the old 
papilla. A hair ceases to be produced when no new cells are 
formed in the hair-root. The last-formed cells become con- 
verted into the hair proper, and form a conical or knobbed ex- 
tremity to the lower end of the hair-shaft. 
The nails.—The nail is merely a modification of the epi- 
dermis, and differs from the stratum corneum only in being 
harder and firmer. It is a longish, four-sided, hard, elastic, 
transparent, dense, fiat body, situated in a fold of the skin on 
the dorsal surface of the terminal phalanges of the fingers and 
toes. It is slightly curved in its long diameter, the convex sur- 
face being above and the concave below. Its posterior and two 
lateral sides are connected with the other structures of the skin; 
the anterior side is free. The fold of skin in which the pos- 
terior and two lateral surfaces are imbedded increases in depth 
from before backward, and at the posterior margin is continued 294 
MANUAL OF HISTOLOGY. 
forward for a short distance on the surface of the nail. This 
fold of skin is called the nail fold, and the tissue upon which 
the nail is seated is termed the bed of the nail. That part of 
the nail imbedded in the flesh posteriorly is the root of the nail, 
and the remainder its body. The flesh underlying the root— 
tire corium—is called the matrix, and that underlying the body 
of the nail the bed of the nail proper. The matrix and bed of 
the nail proper are separated by a more or less convex line, gen- 
erally easily seen through the nail and known as the lunula. 
The bed of the nail is composed of corium and rete Malpighii 
tissue. There is no fat in its subcutaneous tissue. The rete 
here dips down between the papillae of the corium as in other 
parts of the skin. The papillae in the matrix project forward, 
and are shorter and closer together than in the bed of the nail 
Fig. 124.—Transverse section of the nail through the bed of the nail proper: a, nail; 6, loose cor- 
neous layer beneath it: c, mucous layer ; cl, transversely divided nail ridges; e, nail-fold without papillae; 
f. the horny layer of the nail-fold which has pushed forward on the nail; <J, papilla; of the skin of the 
finger. Biesiadecki. 
proper. In this latter structure the papillae also project for- 
ward (Fig. 124, d) and increase in length as the free margin of 
the nail is approached. The rete Malpighii covers the papillae 
of the nail, forming cones, which fill the space between the 
papillae. In the bed of the nail proper the transition from rete 
cells to horny cells is very rapid, whilst in the matrix it is 
gradual. Consequently, this portion of the nail is softer than 
the other. It is from the matrix that the nail is formed, and 
from the corneous cells of the body of the nail that the nail is 
made thicker. The soft cells are directed forward and become 
more horny as they advance. The under surface of the nail- 
fold covering the posterior part of the nail is provided with 
epidermis, which is continued forward a short distance on the 
upper surface of the nail. THE SKIN. 
The tissue of the nail is nourished by blood from the bed of 
the nail and from the nail-fold. Nails grow more rapidly in 
children than in adults, and more rapidly in summer than in 
winter. The rapidity of growth varies according to the person 
and the particular nail. The rate of growth in individual nails 
can be learned by observing the rate of progress toward the free 
margin of the white spots seen on nails. 
The nail begins to form in the third month of intra-uterine 
life as a fold covered with a layer of embryonic epidermic cells. 
In the fourth month a layer of new cells, which afterward be- 
come the horny cells of the nail, appear between the rete Mal- 
pighii and the embryonic epidermic corpuscles. At the fifth 
month the epidermic covering disappears and the nail lies ex- 
posed. Between the sixth and eighth months the nails are 
somewhat firm, but do not quite extend to the ends of the 
fingers. At the eighth month the nails are well developed and 
extend to the extremities of the fingers. 
For the microscopical study of the horny part of the nail, 
sulphuric acid, or caustic soda, or potash must be employed to 
soften the corpuscles. For the other structures of the nail no 
special procedure is necessary. 
BIBLIOGRAPHY. 
Wagner. Muller's Archiv. 1852. 
Meissner. Beitrage z. Anat. u. Phys. d. Haut. Leipzig, 1853. 
Oehl, E. Annali urdv. di med. 1857. 
Krause. Die term. Korp. d. einf. Sens. Nerven. Hannover, 1860. 
Sciiroen. Contrib. alia anat. fisiolog. e patholog. della cute umana. Torino, 1865. 
Aufphamer. Wurzburger Yerhandlungen. Band I. 1869. 
Tuomsa. Arch. f. Dennat. 1873. 
Lott. Ueber den feineren bau u. die pliys. Regeneration des Epitbels. Leipzig, 
1874. 
Thin. Journal of Anat. and Phys. Yol. YIII. 1874. 
Reynold. Ueber die Knaiieldriisen des Menschen. Yirchow’s Archiv. Bd. LXI. 
1874. 
Unna, P. Archiv f. mikrosk. Anat. XII. 1876. 
Fischer, E. Ibid. 
Ravogli. Med. Jahr. Wien. H. I. 1879. 
Ranviek. La France medicale. January, 1880. CHAPTER XIX. 
THE CENTRAL NERVOUS SYSTEM. 
E. W. AMIDON, M.D., New York City. 
The spinal dura mater is a serous membrane. Its structure 
from without inward is: first, loose connective tissue; then dense 
fibrous tissue; lastly, a layer of lymph-vessels and endothe- 
lium. If one tears, with forceps, a shred from the outer surface 
of the dura mater, fresh or hardened, stains with hgematoxylon, 
teases, and examines in glycerine, there is seen a loose network 
of connective-tissue bundles containing free and fixed connec- 
tive-tissue cells, blood-vessels, minute nerves, and some fat- 
cells. This layer is continuous with the loose adipose tissue 
which normally surrounds the dura mater. The denser tissue 
next in order may be treated in the same way, and perhaps a 
few spindle-shaped connective-tissue cells and elastic fibres 
may be isolated. 
On transverse section, however (a very difficult thing to 
make, by the way), the bulk of the membrane is seen to be a 
dense mass, 0.5—1.0 mm. thick, composed of longitudinal and 
horizontal connective-tissue bundles, interspersed here and 
there with elastic fibres. In this layer blood-vessels and nerves 
are very scanty and small. 
Xext, immerse a piece of dura mater, as fresh as possible, 
in a one per cent, solution of nitrate of silver. Leave it for sev- 
eral hours, and then expose it for a few minutes to the sunlight. 
When a brown tint is developed on the inner surface, remove 
it, wash it in distilled water, and strip off the internal surface 
with forceps. 
The shreds of tissue thus obtained show beautifully the 
structure common to all serous membranes : first, a delicate en- 
dothelial layer (see Fig, 125), consisting of flat, unequal, irreg- 
ularly shaped cells, most of which are furnished with large, THE CENTRAL NERVOUS SYSTEM. 
297 
round nuclei; here and there are seen stomata marked by an ag- 
gregation of nuclei, which are all located at the edge of the cells 
surrounding a stoma; secondly, irregularly disposed lymph- 
spaces and vessels. The lymph-spaces appear as irregular, 
transparent patches lying just under the endothelium, and 
the lymph-vessels are 
seen as varicose chan- 
nels, which begin by 
a blind extremity, an- 
astomose freely, re- 
ceive tributaries, and, 
finally, empty by a 
constricted orifice 
called a stoma. Their 
walls are in places 
thin, but more often 
thick and irregular 
from the aggregation 
Fig. 125.—Diagram representing the internal surface of the 
dura mater treated with nitrate of silver. Shows endothelium 
with nuclei and intercellular masses of protoplasm and a lymph- 
channel, L.c., lined by delicate endothelial cells, which termi- 
nates at S, an opening called a stoma about which is an aggre- 
gation of nuclei, x 300. 
of masses of protoplasm along the sides. The capillary lymph- 
atic radicles are lined by a very delicate endothelial layer, 
which can only be demonstrated in completely successful sil- 
ver preparations. Some are seen to contain lymph-corpuscles, 
others are found empty. 
The spinal arachnoid is also a serous membrane, much more 
delicate, however, than the dura mater. Its extreme thinness 
allows it to be examined in the fresh state or stained by car- 
mine or hsematoxylon. It is seen to be essentially a large- 
meshed connective-tissue network, containing many elastic 
fibres. Good silver preparations demonstrate an endothelial 
coat and a lymph system similar to, but more delicate than 
that of the dura mater. It is doubtful whether blood-vessels 
exist in the arachnoid in its normal state. 
The spinal pia mater consists of a small amount of connec- 
tive tissue, holding together a vascular plexus. It is firmly 
adherent to the cord, dips into all its fissures, and is intimately 
connected and continuous with the connective-tissue frame- 
work of the cord. The pia mater is best studied by means of 
fresh specimens stained in hsematoxylon, as this demonstrates 
beautifully the different coats of the small vessels. 
The spinal fluid should be clear, and contain only a few 
lymph-corpuscles; but it usually, when examined post-mor- 298 
MANUAL OF HISTOLOGY. 
tern, contains some blood-corpuscles and swollen epithelial 
cells. 
General histology of the spinal cord.—The spinal cord is 
composed of connective tissue, blood-vessels, nerve-structures, 
and epithelium. 
The connective-tissue framework or neuroglia of the cord 
is constructed as follows: At tolerably regular intervals the 
pia mater at the periphery of the cord sends off prolonga- 
tions which form septa, dividing the white substance into a 
large number of prisms (base outward). From each of these 
septa smaller branches spring, forming a delicate network, or 
stroma, which encloses the nerve-fibres. Generally one, but 
sometimes two or more fibres are contained in the same mesh. 
At the points of junction of these ultimate fibres are seen, 
here and there, small branching cells, the so-called spider- or 
neuroglia-cells. This fibrous structure reaches to the central 
gray matter and penetrates it by very delicate processes, which 
chiefly accompany the nerve-fibres. 
Three large prolongations of pia mater are of constant oc- 
currence, viz., the posterior median septum and a less complete 
septum on either side, dividing the posterior column into two ; 
the larger, anterior, or column of Burdach; and the smaller, 
posterior, or column of Goll. The connective-tissue elements 
are best brought out by hsematoxylon. 
The blood-vessels of the cord are derived from its pia mater, 
follow its prolongations, and are most numerous in the gray 
matter, especially that of the anterior horns. In transverse 
sections there will be seen a clear space about all the blood- 
vessels. This is the perivascular space or lymph-channel, in 
which all the blood-vessels are contained. During life these 
sheaths probably serve a double purpose : an auxiliary nutri- 
ent function by lymph-circulation ; and a means of accommo- 
dating the ever-varying degrees of vascular distention. In 
some diseases they become enormously dilated. They are all 
connected with the space between the pia mater and the cord, 
and an injection forced into this space will follow the blood- 
vessels for long distances. These perivascular spaces are also 
said to be lined with endothelium. 
The vessels of the cord present no other peculiarities. Their 
structure is best brought out by the use of a dilute luematox- 
ylon solution, or by the slow carmine staining. The perivas- THE CENTRAL NERVOUS SYSTEM. 
299 
cnlar canals may be more clearly demonstrated by forcing a 
colored gelatine injection at any point under the spinal pia 
mater—care being taken, if the cord is cut, to secure the ends 
of the sections by ligatures. 
Nerve-elements of the cord.—The consideration of the ner- 
vous elements of the cord will now be taken up in a general 
way, and the peculiarities of different regions explained later. 
The white substance of the cord contains, besides the blood- 
vessels and neuroglia already mentioned, myelinic nerve-fibres 
of different sizes. These fibres pursue a vertical course, with 
the exception of those forming the root-radicles and commis- 
sures. 
On examination with a low power, the wdiite substance, in a 
transverse section stained with carmine, seems to be a collec- 
tion of minute rings, each with a red dot in the centre. More 
highly magnified, the transverse section of a nerve-fibre appears 
as a delicate, rather irregular circle, on the circumference of 
which, in some cases, are seen nuclei resembling those of the 
sheath of Schwann, but which are really nuclei of the neurog- 
lia. Next comes a broad ring of colorless, transparent mate- 
rial, the medullary or myelinic-sheath, which very often ex- 
hibits concentric lamination. Lastly, usually in the centre, is 
seen the solid axis-cylinder. 
When these fibres pursue a more or less horizontal direc- 
tion they give the appearance of broad, clear bands traversed 
by longitudinal red fibres (axis-cylinders). The myelinic fibres 
average about 5y1 in diameter. Fibres, when isolated by 
teasing, present the varicose aspect of myelinic nerve-fibres, 
which lack the sheath of Schwann. To demonstrate this they 
are best treated when in the fresh state by osmic acid (see p. 
114), the result being a black myelinic sheath and brownish 
axis-cylinder. 
The gray matter is composed of nerve-cells, medullated and 
non-medullated nerve-fibres, and an amorphous matrix. The 
most striking elements are the cells of the anterior horns. 
These, whether teased from specimens fresh or hardened in 
chromic acid, or whether examined in sections, always present 
the same general appearance. They are large, multipolar cells, 
having a slightly granular, protoplasmic body, a large, oval 
1 = xnicromillimetre = toVu millimetre. 300 
MANUAL OF HISTOLOGY. 
nucleus, and a round nucleolus. These cells are polyhedral in 
form, as is shown by the fact that sections made in all direc- 
tions give them the same pyramidal or polygonal outline. In 
nearly all the large cells there is in some part of the body an 
aggregation of granules, which are often distinctly pigmented, 
giving the appearance of a heap. 
Striations of the body have been frequently described and 
depicted (Schultze, Schmidt, etc.), and this appearance has 
been attributed by some to plications of a very delicate invest- 
ing membrane, by others to ex- 
pansions of the ultimate nervous 
fibrillse, of which the axis-cyl- 
inder was thought to be com- 
posed. The motor cells average 
about 40 y. in diameter. The 
cell-processes vary in number. 
Most of them are bifurcating. 
One, however, connected witli 
nearly every cell, can be fol- 
lowed for a long distance with- 
out dividing, and when the cell 
is situated near the anterior 
rootlets this process joins them 
and acquires a myelinic sheath. 
Pig. 196.—Diagram of a motor-cell from the 
anterior horn of a human cord in the cervical 
enlargement, x SOO. 
This is called the axis-cylinder process. The branching pro- 
cesses are called the protoplasmic processes, and are supposed 
by some to freely anastomose with those of other cells. This 
anastomosis, if it exist at all, is very delicate, and difficult of 
demonstration. 
A certain number of the cells of the anterior horns, espe- 
cially those located in the lateral region of the cornua, present 
an elongated, fusiform aspect, and appear to have but two 
processes. The nerve-cells in the posterior horns are of an 
elongated oval or fusiform shape, their long diameter corre- 
sponding in direction with that of the posterior horn. They are 
very much smaller than the anterior cells, and less numerous. 
Their average diameter is about 15 y. They are seldom seen 
to have processes. 
The myelinic nerve-fibres of the gray matter are seen prin- 
cipally in the anterior horns, and converging from the cell- 
groups to form the anterior root-radicles. Here and there fibres THE CENTRAL NERVOUS SYSTEM. 
301 
appear in transverse section, which, singly or in bundles, pur- 
sue a longitudinal direction. 
Amyelinic fibres are found everywhere in the gray matter 
pursuing various courses. The gray commissure is composed 
almost completely of amyelinic fibres connecting the lateral 
gray masses. 
Besides the above-described elements the gray substance 
seems to have a structureless or slightly granular matrix, in 
which the other elements are embedded. In the study of the 
spinal gray matter osmic acid and carmine preparations are by 
far the most useful, although much is to be learned by the ex- 
amination of fresh specimens teased in serum. To study the 
cells, cut out a piece from the anterior horn of a fresh cord 
and tease in serum. A preliminary treatment with osmic acid 
or ammoniacal carmine is sometimes advantageous. 
The epithelium of the spinal cord lines the central canal. 
The most internal layer is of the cylindrical, ciliated variety. 
On account of the difficulty in obtaining fresh specimens the 
cilia are never seen in the human cord, though they undoubt- 
edly exist. The epithelial cells, as they do exist in the human 
cord, have a square base, taper to a slender thread toward 
the apex, which penetrates the layer of young, round epithe- 
lial cells, and is lost in the granular central gray matter. The 
cells of the second layer are round, granular, and thickly 
crowded. 
The subepithelial tissue, for some distance around the cen- 
tral canal, consists of embryonal cells in a granular matrix. 
The central canal1 has no constant shape, varies greatly in 
size, and is often choked with desquamated epithelium. Its 
position, as its name indicates, is in the middle of the gray 
commissure, on a line passing between the anterior fissure and 
posterior septum. The general features of the spinal cord hav- 
ing been pointed out, the peculiarities of different regions will 
now be shown. 
Special study of the different portions of the cord.—The 
cord will be studied from below upward. The mode of study 
will mainly be by sections made after Clarke’s method. The 
cord, after slitting the dura mater with the scissors up the 
front and back, is cut in segments 3 ctm. long, which adhere 
1 Sometimes double. See Seguin; Am. Jour. Med. Sci., p. 427. 1872. 302 
MANUAL OF HISTOLOGY. 
to the undivided dura mater. Thus prepared it is suspended 
in Muller’s fluid (see p. 15), or dilute chromic acid (see p. 
14), until hardened. The segments are then embedded in 
a microtome (see p. 16), and horizontal, transverse sections 
made. These are washed in distilled water and stained with 
carmine or hsematoxylon (see p. 23). A few minutes’ immer- 
sion in alcohol previous to this manipulation makes the tissues 
take the coloring more quickly. After staining and washing, 
dehydrate the sections with alcohol and absolute alcohol, make 
transparent with oil of cloves, and mount in Canada balsam or 
dammar varnish (see p. 23). 
Hidden in the cauda equina is found the filum terminate, 
which is the end of the cord. Sections near its end exhibit lit- 
tle of the structure of the cord. At a point where it is 1.5 mm. 
in diameter it presents the appearance of a peripheral nerve, 
except that it has an opening—the central canal—in its centre. 
Its transverse section shows a collection of large and small 
myelinic nerve-fibres pursuing a vertical direction. 
A little higher up, where the filum measures 2 mm. in diam- 
eter, there is little difference, except that the central canal is 
nearer the surface (anterior) and surrounded by a small amount 
of gray matter. How and then there are seen small, oval nerve- 
cells in the region posterior and external to the central canal. 
A little higher still, where the filum is 3 mm. in transverse 
and 2 mm. in antero-posterior diameter, back of the central 
canal on each side, where the future posterior horn is to be, 
there is a small collection of spindle-shaped cells. 
Sections from a region a little above this present an entirely 
different picture. The gray substance is here much more devel- 
oped and occupies the larger part of the section. It is divided 
into a club-shaped anterior horn, containing a few large poly- 
hedral cells, and a posterior horn which is rounded and formed 
of peripherally directed nerve-fibres and oblong nerve-cells. 
From this point up sections gradually become more circular 
and develop more and more a resemblance to the structure of 
the cord, until, at a point where the sections are about 3.5 mm. 
in diameter, the anterior fissure and posterior septum become 
well marked. The anterior horns contain few cells, and the 
fibres emanating from them pursue a very oblique course down- 
ward through the anterior columns. 
From the lateral gray matter arise bundles of nerve-fibres THE CENTRAL NERVOUS SYSTEM. 
303 
which curve around the posterior horn, and, meeting similar 
fibres from the posterior columns, together form the posterior 
nerve-root. These two bundles form an arciform structure sur- 
rounding the round extremity of the posterior horn. (See Fig. 
127.) The gray commissure occupies one-third the diameter of 
the cord. The central canal is large, slit- 
like, and antero-posterior in direction. To 
summarize then, there seems to be in the 
Ilium terminale, especially its lower por- 
tion, a preponderance of the posterior or 
sensory part of the cord. 
About two centimetres from the end of 
the cord nearly the same picture is pre- 
sented. The transverse section is circular 
and about 6 mm. in diameter. Many large 
nerve-cells appear at the outer side of 
the anterior cornua, mostly at their junc- 
tion with the posterior horns. Fibres from 
Pig. 127.—Three sections 
of the filum terminale: a, its 
transformation into the coccy- 
geal nerve; b, section higher 
up before the giving off of the 
last sacral filaments; c, its 
commencement. 
this cell-group, instead of running a direct course, curve 
backward and inward (see Fig. 127), then run forward and 
emerge from the anterior horns. Many oval cells appear in 
the posterior horns, which now reach the surface of the sec- 
tion, and the posterior roots begin to show their origin from 
the posterior columns and horns. 
In the lumbar enlargement trans- 
verse sections have a circular shape. 
(See Fig. 128.) The white substance 
here predominates, and has but one 
peculiarity, which will be noticed in 
greater or less prominence through- 
out the remainder of the cord. At 
the bottom of the anterior fissure is a 
broad band of white substance called 
the white commissure. This is formed 
of myelinic nerve-fibres, which pursue 
a course from the base of the anterior 
horn of one side, forward, across the 
median line and downward to join the 
Pig. 128.—Three diagrams show- 
ing the relations of gray and white 
matter in different regions of the cord: 
«. lumbar enlargement; b. mid-dorsal 
region ; c, cervical enlargement. 
anterior column of the opposite side at a lower level. (See 
Fig. 129.) The anterior horns in the lumbar region are large 
and square, as are also the cells contained in it. The gray 304 
MANUAL OF HISTOLOGY. 
commissure is narrow, and tlie central canal lias its long diam- 
eter placed transversely to the cord. 
Transverse sections in the dorsal region are circular and 
8 mm. in diameter. The white commissure is thin, otherwise 
the same structure as in the lumbar region is observed. The 
anterior horns are narrow and sparsely filled with rather small 
multipolar cells. ISTo continuous tracts of nerve-fibres can be 
traced through the anterior columns, as their course is so oblique 
(downward) as to give almost a transverse section of the bun- 
dles. The posterior horns, just behind the gray commissure, 
are swollen out, and contain a number of large nerve-cells— 
some multipolar, some oval. They approach the type of the 
cells in the posterior horns. This collection of cells is called the 
column of Clarke. 
Transverse sections in the cermcal enlargement measure 
about 14 mm. The antero-posterior diameter is about 11 mm. 
The white commissure in this region presents about the same 
characteristics as in the lumbar region. The anterior horns are 
fan-shaped; the anterior roots 
curve forward, outward, and 
downward. The central canal is 
triangular. The posterior horns 
are slender, and contain a few 
small nerve-cells. The posterior 
roots are also more intimately 
connected with the posterior 
horns than lower down. 
Flo. 129.—Diagram of transverse section of 
the cord in the upper cervical region, showing 
coarse connective-tisane reticulum in left half 
of diagram, commencing decussation of the 
lateral columns across the base of the anterior 
horn into the opposite anterior column, taking 
the place of the anterior commissure lower 
down, and the root of the spinal accessory, 11 : 
A.H. anterior root; P.R. = posterior root. 
In this figure and in others small crosses must 
be understood as nerve-cells. 
In the upper cermcal region 
the gray matter assumes more 
the shape of the dorsal gray 
matter. In the lateral region, at 
the junction of the anterior and 
posterior horns, longitudinal bun- 
dles of myelinic nerve-fibres begin to appear. These bundles 
curve over (see Fig. 129), and pass rather obliquely upward 
and outward through the lateral columns, emerging nearer the 
posterior than the anterior horns. They are joined by fibres 
curving back from the cells of the anterior horns, and also 
emanating from the central gray matter. In this structure is 
seen the first appearance of the spinal portion of the spinal 
accessory root-fibres. The longitudinal bundles mentioned THE CENTRAL NERVOUS SYSTEM. 
305 
evidently come from cells of the anterior horns lower down. 
Some of the fibres, passing back from the anterior horns to Join 
the root, are seen to arise directly from the motor cells. 
In taking leave of the cord, the introduction of a diagram1 
showing its regional anatomy, looked at from a physiological 
standpoint, is deemed ad- 
vantageous. It will enable 
the microscopist to properly 
record localized lesions. 
In studying the spinal 
cord by means of horizon- 
tal transverse sections, it is 
of the utmost importance, 
particularly in pathological 
cases, to know which is the 
right or left side, and whe- 
ther one is looking at the 
upper or under surface of a 
section. Of so much impor- 
tance is this knowledge, 
that some means must be 
employed to acquire it. 
Fig. 130.—Diagram of transverse section of the 
spinal cord: A, anterior median fissure; P, posterior 
median septum; 1, columns of Goll; 2, columns of 
Burdach ; 3, direct cerebellar column; 4. crossed pyra- 
midal column; 5. lateral column ; fi, anterior funda- 
mental column; 7, direct pyramidal column; 8, pos- 
terior gray horns; 9. anterior gray horns; stippled 
part, gray matter; shaded part, cesthesodio system; 
unshaded part, kinesodic s3-stem. 
One of the best means is a method devised by Dr. E. C. 
Seguin, and published in the translator’s note appended to 
Schultze’s article on the spinal cord, in the American translation 
of Strieker’s “ Histology,” p. 647. He there recommends, be- 
fore placing the segment of the cord in the microtome, that a 
slight longitudinal incision be made in the right lateral column. 
By this means all the sections have a nick in the right lateral 
column, and can easily be placed. This method, however, has 
many drawbacks. One is that it is a process easily forgotten 
during the manipulations. Another more serious drawback is 
the fact that, make the incision slight as you can, the resulting 
nick often causes extensive fissures and crumbling of the lateral 
column or whole section, especially in pathological or over- 
hardened specimens. 
The requirements by the new method are two: Ist, the 
sections must be nearly horizontal; and 2d, they must be suf- 
1 Dr. E. C. Seguin ; Lectures on Localization, in N. Y. Medical Record, April 27, 
1878, p. 323. 306 
MANUAL OF HISTOLOGY. 
ficiently well stained and transparent to demonstrate the con- 
stituent parts of myelinic nerve-fibres. The mode of determi- 
nation depends entirely on the fact that the anterior roots 
pursue an obliquely descending course through the anterior 
columns, and for this reason horizontal sections cut the ante- 
rior rootlets obliquely. (See Fig. 181.) 
What is the natural inference to draw from this fact % It is 
this : let the reader look at the upper surface of a transverse 
section of the spinal cord and bring the anterior roots into the 
field ; that is, let him look down the anterior column. He 
readily perceives that the central ends of the anterior root- 
fibres are nearer his eye than the peripheral ends. He sees 
that while the central ends are at the focus, the peripheral 
ends are beyond the focus, and he needs to bring the eye nearer 
to define them. This nearing the focus also gives the fibre- 
bundle an apparent peripheral motion, while increasing the 
focal distance causes an apparent central motion. 
The application of this method to a chance section is easy 
Suppose we examine the anterior 
columns of a section and find by 
focussing that the central ends of 
the anterior root-fibres are farther 
from the eye than the peripheral 
ends. We will immediately know 
we are looking up the cord or at 
the under surface of the section. 
How, all it is necessary to do is 
to turn over the section, either in 
your mind or on the slide, and put 
the anterior horns forward. The 
section is then in position. 
Fig. 131.—Diagram of vertical section 
of human cord through the anterior and 
posterior columns and the anterior horns. 
It is intended to demonstrate how a trans- 
verse, horizontal section. S, cuts the an- 
terior nerve-roots obliquely. (Prom Ar- 
chives of Medicine, August 1, 1879, p. 70.) 
In sections of the cord where 
the anterior roots do not show, the 
posterior roots may be used in a similar wa}q as they, too, pur- 
sue a slightly descending course. Their use is not so easy, as 
the fibres are short and pursue a slightly wavy course. In 
sections or fragments of sections, where neither of these struc- 
tures avail, a study of the course of the fibres in the anterior 
white commissure will lead to detection. These fibres pursue 
a course downward and across the median line, from the base of 
one anterior horn into the anterior column of the opposite side. THE MEDULLA OBLONGATA. 
307 
In sections of the upper cervical region the spinal accessory 
roots may be made use of, remembering, however, that they 
pursue a course obliquely upward through the lateral columns. 
The application of these rules to the medulla will be pointed 
out later on. 
Note.—To demonstrate the obliquity of the anterior rootlets, find, by a trans- 
verse section, the exact direction of the anterior rootlets, and then make longi- 
tudinal sections through the anterior column and horn on this line. 
THE MEDULLA OBLONGATA. 
In the upper part of the cervical region changes take place 
in the arrangement of the elements of the cord transforming it 
into the medulla oblongata. The changes are as follows : be- 
fore the external signs 
of decussation ap- 
pear, it is seen that 
the fibres of the later- 
al columns change 
their vertical course 
and bend forward and 
inward. This fact is 
demonstrated by the 
oblique sections of 
bundles and fibres. A 
little higher these 
bundles and fibres 
can be traced across 
the gray matter be- 
Fig. 132.—Diagram of the medulla, pons, etc., natural size, to 
show the direction of sections for displaying the different nuclei 
and roots : ll', line of section to show the early decussation of the 
lateral columns and spinal accessory tract; 11, line of section to 
show the spinal accessory tract and decussation of the pyramids; 
11 & 12, region of the spinal accessory and hypoglossal; 10, pneu- 
rnogastrio; 9, glosso-pharyngeal; 8, acoustic; 6& 7. abdncens 
and facial; 5, trigeminus; 4, patheticus ;3, motor oculi; c. (/., 
corpora quadrigemina ; c. c., crus cerebri. 
■i • t , i , -i 
lima 1110 anterior norn 
into the opposite an- 
terior column, which is to become by this addition the anterior 
pyramid. The decussating fibres take the place of the ante- 
rior commissure lower down, and the fibres pass upward and 
forward across the median line. The fibres of the anterior 
columns do not decussate at all, but give way to and mingle 
with the fibres from the lateral columns. 
The shape and structure of the anterior horns are about the 
same as lower down. The posterior horn expands suddenly at 308 
MANUAL OF HISTOLOGY. 
its peripheral extremity into a bulbous termination (see Fig. 
133), from which the posterior root emerges. The central gray 
matter between the two horns is traversed and intersected by 
the decussating fibres from the lateral columns. Numerous pro- 
longations from this gray matter spread out into the lateral 
columns, presenting a coarse reticulum, called thq formatio 
Fig. 133.—Diagram of transverse section of 
human medulla below external decussation of 
pyramids, showing bulbous posterior horns: 
FR, formatio reticularis; 11, spinal accessory- 
root and decussation of the lateral columns. 
Fig. 134.—Diagram. Decussation of the pyra- 
mids, shows decussation of the lateral columns, 
the swelling of the posterior horns, the shrink- 
age of the anterior horns, the spinal accessory 
root 11, and a partial decussation of the posterior 
columns behind the central canal. 
reticularis. The gray commissure is very broad, the central 
canal having its long diameter directed antero-posteriorly. 
In sections at the decussation of the pyramids proper, i.e., 
where they are seen to decussate externally, a slightly different 
picture is presented. The lateral columns have nearly disap- 
peared, having now almost all entered into the decussation, 
which is here very broad (see Fig. 134), and presents a peculiar 
zigzag appearance from the interweaving of bundles of fibres 
from the opposite lateral columns. These fibres, after curving 
around the anterior columns for a short distance, seem to dis- 
appear by assuming a vertical direction. The club-shaped ex- 
tremities of the posterior horns remain, while the rest is pushed 
back into the posterior columns, and contains many large cells. 
The anterior horns are also displaced backward, pushed 
back by the anterior columns increased in size by the addition 
of the lateral col umns. Hence, the anterior roots have a longer 
path through the anterior columns and approach the type of 
the hypoglossal nerve-roots seen a little higher up. (See Fig. 
135.) The spinal accessory nerve curves out and back from the 
lateral gray matter where a group of cells is situated. THE MEDULLA OBLOXGPATA. 
309 
Let us next take up a section involving the lower end of 
the olivary body. We have the following view presented. 
The section is slightly cordiform. (See Fig. 185.) The decussa- 
ting fibres at the base of what remains of the anterior fissure, 
which has all along become shallower, now forms the com- 
mencement of the raphe, a structure which extends all through 
the rest of the medulla and pons, separating the two motor 
tracts. The union of the lateral and anterior columns now 
nearly complete, forms the anterior 
pyramids. The fibres here have a 
general vertical direction, except 
that a broad band which emerges 
from the decussation at the bottom 
of the anterior fissure, curves around 
the margin of the anterior pyramid, 
and then, sometimes in the sub- 
stance, sometimes at the surface of 
the medulla, almost completely sur- 
rounds it, the bundle becoming lon- 
gitudinal on the posterior surface. 
These bear the name of the arciform 
fibres. The rest of the white matter 
is so cut up as to render it hardly 
Fig. 135.—0ne half of section at lower 
end of the olives: 11, upper spinal acces- 
sory root; 12, lower hypoglossal roots. 
divisible into regions. The central canal, which is very long 
antero-posteriorly, has almost coalesced with the gradually 
deepening posterior furrow soon to become the fourth ventricle. 
The gray matter originally in the cord is now collected 
about the central canal. Anterior and external to the central 
canal there is a small group of multipolar cells. This is the 
remnant of the anterior horns, which have been continually 
crowded back by the accumulation of fibres in the anterior 
pyramids. These cells in every respect are similar to those in 
the anterior horns. Their processes give origin to fibres wdiich 
course forward in two or three bundles through the white 
matter of the anterior pyramids, and emerge at about the 
junction of the anterior pyramids and the lateral white mass. 
A little farther back in the gray matter, behind the central 
canal, is a small group of nerve-cells the remains of the spinal 
accessory nucleus, from which a few fibres run in a straight 
course outward and slightly backward, through the lateral 
white matter. Additional collections of gray matter now begin 310 
MANUAL OF HISTOLOGY. 
to appear. In the posterior region is a large tract (see Fig. 135) 
containing scattered groups of many small cells evidently con- 
nected with the arciform fibres. This is probably a part of 
the lower origin of the pneumogastric. A little in front and 
external to this is a small group of larger nerve-cells which 
help to form the lower sensory origin of the fifth nerve. Still 
farther forward in the lateral region is a large collection of 
multipolar nerve-cells. Although this group is traversed in 
many directions by fibres, single and in bundles, still it seems 
to give rise to fibres which run back and upward, evidently to 
curve upon themselves and join the peripheral fibres of the 
spinal accessory root. (See Figs. 135 and 137.) 
Farther forward still there is a collection of small cells 
arranged in a wavy line (see Fig. 135), the commencement of the 
olivary nucleus. Through this the roots of the hypoglossus 
all pass. Some seem to be lost in it, others appear to arise 
from it, but this is probably due to the arrangement of roots 
often seen to curve into the nucleus and then out again. As 
this is the first appearance of the olivary body, it will be well 
here to describe it. 
THE OLIVARY BODY. 
The olivary nuclei are situated in the medulla, under the 
oval projections on its anterior surface called the olivary bodies. 
The nucleus consists of a strip of gray matter arranged in gen- 
eral like a piece of fluting folded on itself, so as to form almost 
an ellipse. From the concavities of the fold on either side pro- 
ceed bundles of fibres, the external ones joining the formatio 
reticularis, the internal ones passing into the raphe. Their 
connection with the hypoglossal roots is probably not im- 
portant. The intimate structure of the olivary fold is that of a 
dense gray matrix holding numerous small polyhedral cells 
having delicate protoplasmic processes. 
Let us now go a trifle higher (see Fig. 137), and observe that 
in sections the central canal, which has all along been elongat- 
ing and receding backward, now opens into the apex of the 
fourth ventricle. There is now, therefore, quite a deep notch in 
the posterior part of the section, covered with the same cylin- 
drical epithelium which lined the central canal. On each side, THE OLIVARY BODY. 
311 
and in front of the bottom of the fourth ventricle, lies a large 
group of multipolar cells, the hypoglossal nucleus, from which 
bundles of fibres course forward through the olivary body, 
which is here much enlarged and more complex than in the 
last section. On the inner side of the hypoglossal roots in 
the olivary region is an elongated mass of gray matter con- 
taining small cells, called the parolinary nucleus. There is 
an oval group of fusiform cells at, behind, and external to 
the hypoglossal nucleus, from which indistinct and broken 
bands of fibres pass outward to emerge from the lateral re- 
gion of the medulla. This constitutes the upper spinal acces- 
sory nucleus and root. Behind this nucleus, forming the 
Pig. 136.—Diagram showing structure of 
one fold of the olivary nucleus : C, centripe- 
tal fibres; P, peripheral fibres, x 64. 
Pig. 137.—0ne-half transverse section of 
the human medulla at the point of fusion of 
the central canal and the posterior fissure to 
form the fourth ventricle : 11, spinal acces- 
sory root; 12, hypoglossal root; B, raphe. 
eminence on each side of the fourth ventricle, is a large mass 
of gray matter containing a great number of small nerve-cells, 
which also seems to be, rather indistinctly connected with 
the sjiinal accessory root. External to this nucleus is a con- 
tinuation of the collection of large cells seen in the section 
lower down, the lower sensory nucleus of the fifth. In front 
of the spinal accessory root is seen a group of multipolar cells 
not so large as in preceding sections. The peripheral circular 
fibres in this region are confined to the anterior and external 
aspect of the medulla, and are still seen to be in connection 
with the raphe by the arcuate fibres which traverse obliquely 
the intervening nervous tissue. 
From this point to the middle of the olives, sections differ 312 
MANUAL OF HISTOLOGY. 
little, except that in this space the root-fibres of the spinal 
accessory seldom appear, although figured by most writers. 
The region formerly occupied by the spinal accessory nucleus 
contains a group of small cells which form part of the pneu- 
mogastric nucleus. The fibres 
between this nucleus and the 
point of exit of the pneumo- 
gastric root run so obliquely 
upward, that no direct connec- 
tion between them can be traced. 
It is in sections at the mid- 
dle of the olives that the pneu- 
mogastric begins to appear dis- 
tinctly. Most of its fibres seem 
to be connected with a small 
group of cells situated in the 
gray matter, at the junction of 
the funiculi graciles and the 
restiform body. The gray mat- 
Fig. 138.—One-half transverse section of the 
human medulla through the middle of the olives: 
4, fourth ventricle ; 10, pneumogastric root; 12, 
hypoglossal root. 
ter of the restiform bodies is filled with small cells and con- 
tains many fibres having a peripheral direction posterior to the 
pneumogastric root—the beginning of the auditory nucleus 
and root. The olivary body here reaches its highest develop- 
ment and greatest dimensions. 
Behind the olivary body is a small group of cells, from 
which scattered fibres pass backward and 
inward toward the pneumogastric nucle- 
us. But most of them are lost by as- 
suming a longitudinal direction. This is 
probably the lower facial nucleus, to be 
described farther on. The arciform fibres 
are chiefly confined to the surface of the 
anterior pyramids and the olivary bod- 
ies. The fibres of the raphe pursue, in 
great part, an antero-posterior direction. 
Sections through the medulla at the 
upper part of the olivary bodies differ 
little from the former sections. But a 
Fig. 139.—0ne - half trans- 
verse section of the human me- 
dulla through the upper part of 
the olives bringing the glosso- 
pharyngeal tract (9.) and the 
lower part of the acoustic nucleus 
(8') into view. 
small segment of the olivary bodies is present, and only a few 
of the hypoglossal roots remain. (See Fig. 139.) External to the 
remains of the hypoglossal nucleus is a nucleus of small cells THE OLIYAEY BODY. 
313 
giving origin to a bundle of fibres, which pass out laterally Just 
as does the pneumogastric lower down. This is the glosso- 
pharyngeal nerve and root. Farther still from the median 
line, in the floor of the fourth ventricle, is seen a group of 
small cells, the commencement of the acoustic nucleus. Scat- 
tered nerve-cells arising here pursue an obliquely forward and 
outward direction, making the lower margin of the auditory 
root. 
Transverse sections of the medulla Just at the edge of the 
pons bring the acoustic region into view ; the upper olivary 
body is here visible. Behind this are scattered a few large cells, 
from which fibres pass backward to form higher the facial root. 
Fig. 140.—One-half transverse section of 
the human medulla just below the edge of the 
pons, showing acoustic nucleus and roots which 
enclose the inferior cerebellar peduncle I. 0. 
P.: I, internal root; B, external root; u. up- 
per olivary nucleus; Lf, lower facial nucleus. 
3 diams. 
Pig. 141.—Diagram of a transverse 
section just above the edge of the pons, 
having the obliquity given it in Fig. 139, 
6& 7: 6, abducena root; 7, facial root. 
For other explanations, see text. 
Occupying the floor of the fourth ventricle is a large mass of 
gray matter, from which the acoustic arises. This gray matter 
contains many small round and some multipolar cells. The 
nerve has two roots, one internal, the other external. (See 
Fig. 140.) The former arises from fibres emerging from the 
raphe near the fourth ventricle and from the gray matter Just 
external to it, and pursues a course downward and forward 
through the lateral white matter. This root, at its point of 
emergence, is Joined by fibres from the posterior root curving 
around the surface of the medulla, like, if not identical with, 
the arciforra fibres. The external root has also one origin from 
the gray matter near the median line, and curving outward on 314 
MANUAL OF HISTOLOGY. 
the floor of the fourth ventricle (forming the linece transfer see) 
it receives additions from the lateral gray mass, and emerges 
from the medulla a little behind the internal root, which, how- 
ever, it soon joins. 
It is seen that the two roots embrace a column of white 
matter, which is the inferior peduncle of the cerebellum. (See 
Fig. 140.) In sections just above the edge of the pons, having 
the oblique direction given in Fig. 132, the region of the sixth 
and seventh nerves comes into view. The view presented here 
is different from that in the medulla below. In place of the 
narrow band of arciform fibres which covered the anterior re- 
gion of the medulla, nearly the anterior half of this section is 
composed of transverse, arciform fibres. Imbedded in this 
structure is a longitudinal bundle of white matter, the contin- 
uation of the anterior pyramid. The posterior half of the 
section contains the structures under consideration. 
From a group of multipolar cells at the floor of the fourth 
ventricle, some distance from the median line, several bands of 
fibres pass forward and slightly outward, in a somewhat sim- 
ilar way to the hyiDoglossal roots lower down. This is the 
nucleus and root of the abducens nerve. 
Internal to and behind the abducens nucleus, in almost 
all sections, is seen an oval bundle of what at first sight ap- 
pears to be longitudinal nerve- 
fibres. Closer examination, how- 
ever, shows the fibres to be not 
straight but looped, and in suc- 
cessful sections the following ap- 
pearances are presented. Behind 
the anterior pyramids and out- 
side of the abducens root is seen 
a group of multipolar cells oc- 
cupying the same location as the 
group called the lower facial nu- 
cleus, lower down. Arising from 
Fig. 142.—Diagram of course of fibres in 
the “ genu ”of the root of the facial nerve: n, 
fibres coming from the nucleus; g, the “genu,” 
or coil where the fibres change their direction 
R, the root proper of the facial nerve. 
this, and pursuing a course backward and inward, are numer- 
ous fibres ; these reach the oval bundle before mentioned, enter 
it, curl upon themselves (see Fig. 142), and emerge at about 
their point of entrance. The fibres mentioned as appearing 
longitudinal undoubtedly come from the lower facial nucleus, 
and curl upon themselves like the rest. THE OLIYAEY BODY. 
315 
Some fibres (commissural) join the root from the raphe, and 
others seem to arise from the abducens nucleus, though this is 
denied by many authors. The fibres which seem to arise from 
the abducens nucleus are probably fibres from the anterior 
nucleus of the facial, which do not traverse the coil (“genu,” 
as it is called), but enter the root directly. 
The facial root thus formed goes directly outward at first 
toward the external angle of the fourth ventricle, then turns 
sharply forward to emerge at the junction of the pons and 
medulla external to the sixth root. Many authors, first of 
whom was Clarke, describe an inferior nucleus of the facial 
nerve, supposing it to innervate the lips and mouth, basing 
their assertions as much on the seat of lesion in labio-glosso- 
pharyngeal paralysis as on anatomical evidence. There can 
be but little doubt as to its existence, and probably it corre- 
sponds to the group of cells seen in Figs. 187 and 138. 
Sections of the pons above this point soon begin to show 
traces of the fifth nerve, (See 
Fig. 143.) The picture we get 
in transverse sections at the 
emergence of the fifth root is, 
in front, two large bundles of 
longitudinal nerve-fibres sur- 
rounded by the arciform fibres 
and separated by the raphe; 
behind, the gray matter of the 
fourth ventricle, which here is 
pentagonal in shape and is 
covered in by the base of the 
cerebellum, the inferior vermi- 
Pig. 143.—Diagram showing origin and course 
of the trigeminus nerve. 
form process. Emerging from the gray matter in front of the 
external corner of the ventricle, and also joined by fibres from 
above and below, is a large bundle of fibres which pursue a 
diagonal course outward and forward, to emerge from the side 
of the pons. This is the sensory root of the fifth nerve. Inter- 
nal to this root, just after its formation, is seen in successful 
sections a large group of multipolar cells sending off fibres, the 
motor root, which join the sensory root and emerge with it. A 
collection of large, oval, pigmented cells here underlie the exte- 
rior part of the fourth ventricle and form the locus cceruleus. 
It seems to have an indistinct connection with the trigeminal 316 
MANUAL OF HISTOLOGY. 
sensory root, and Meynert makes it one of its points of 
origin. 
The sensory root is reinforced by fibres from a group of 
large oval cells external to the fourth ventricle and by the so- 
called descending branch (Meynert), which is seen in trans- 
verse section in the same location com- 
ing from regions still higher up. Some 
fibres also come from the raphe and 
arcuate fibres, and others from the low- 
er sensory origin of the fifth, which 
occupies a lateral position in all the 
sections up from the spinal accessory 
region of the medulla. 
Higher in the pons, where the ante- 
rior motor tracts or pyramids, before 
mentioned, begin to separate into the 
crura cerebri, the fourth nerves are 
seen. They are supposed to arise from 
a nucleus at the floor of the fourth ven- 
Fig. 144.—Diagram showing ori- 
gin of the third and fourth nerves 
from the gray matter about the aque- 
duct of Sylvius: c. c., crus cerebri; 
3, third nerve; 4, fourth nerve. 
tricle lower down, curve around the outer wall of the ventricle, 
decussate in the median line in the valve of Yieussens, and 
pass from the pons behind the tubercula quadrigemina. From 
this point they curve forward around the crura, on the outer 
side of which they appear at the base of the brain. 
At about this point and a little higher are seen bundles of 
fibres emerging from the gray matter containing small cells, 
in front of the fourth ventricle, diverging and pursuing an 
arcuate course through the crura, to converge again and emerge 
from the inner side of each crus. (See Fig. 144.) This consti- 
tutes the nucleus of origin, the course and point of emergence 
of the third nerve—a view hard to get unless just the right 
obliquity is given to the section. 
Imbedded in the crus, in the region through which the third 
nerve passes, is a collection of pigmented cells forming the locus 
niger. Higher the crura separate and enter their respective 
hemispheres. Their further course is better shown by a trans- 
verse vertical section of the hemispheres at the large part of 
the thalamus opticus. (See Fig. 145.) 
Here we see a great part of the substance of the crus flat- 
tened in form passing upward, between the optic thalamus and 
a gray mass called the nucleus lenticularis, forming what is THE CEEEBELLUM. 
317 
denominated the internal capsule. The posterior third of the 
internal capsule is distributed to the posterior part of the 
hemisphere, and when destroyed produces loss of sensibility 
on the opposite side of the body. The anterior two-thirds of 
the internal capsule is distributed to the middle or motor re- 
gion of the hemisphere, and its destruction causes a paralysis 
Pig. 145.—Modified from Charcot’s diagram to show position, relation, and distribution of the inter- 
nal capsule as seen in a vertical transverse section of the brain on a level with the greatest development 
of TO, thalamus opticus : 10, location of the internal capsule : NL, nucleus lenticularis ; EC, external 
capsule ; D, claustrum ; NO ; nucleus caudatus ; MRC, motor regions of cortex cerebri; 1, fibres repre- 
senting the radiation of the internal capsule vertically to the motor region of the cortex.—Prom “ Lec- 
tures on Localization,” by Dr. E. C. Seguin : New York Medical Record, p. 142, August 24,1878. 
of the opposite side of the body. The fibres expanding from 
the internal capsule, joined by those emanating from the gan- 
glia at the base and the corpus callosum, form a fan-shaped 
expansion of white fibres called the corona radiata. 
THE CEEEBELLUM. 
The white centre of the cerebellum, formed from the ex- 
pansion of the peduncular tracts, incloses a collection of gray 
substance, the corpus dentatum. This body, visible in all 
sections, bears some resemblance to the olivary body in the 
medulla, on account of its irregular, dentated outline. Its 
greater consistence causes it to stand out in a section from the 
surrounding tissue. In intimate structure this body consists 318 
MANUAL OU HISTOLOGY. 
of a collection of small fusiform and polyhedral cells with 
minute processes, imbedded in a basis-substance much more 
dense than the surrounding white matter. The body is made 
to appear striated in a peripheral direction by bundles of 
fibres and blood-vessels pursuing a parallel course. 
The surface of the cerebellum, deeply gashed by sulci and 
their subdivisions, presents, on section, its well-known com- 
pound, arborescent appearance. This arrangement of the gray 
matter causes the greatest possible surface to come in con- 
tact with the blood-current furnished by the pia mater, and 
hence secures the greatest nutrition of the elements of the 
cortex. The gray matter of the cortex is easily divisible into 
an external or granular layer, a middle or cellular layer, and 
an internal or nuclear layer. The latter consists of a vast 
number of small granular cells about the size of white blood- 
corpuscles, which take staining fluids with great avidity. The 
middle stratum is a clear space in which there is a single layer 
of large corpuscles, called the cells of Purlcinje, 10 to 40 /u in 
diameter. They 
are scattered at 
some distance 
from each other, 
and present pe- 
culiarities pos- 
sessed by no other 
cells in the body. 
The cells are of 
large size, vary- 
ing in form from 
fusiform to flask- 
shaped, accord- 
ing to the plane of 
Fig. 146.—Diagram of the cerebellar cortex, showing the large cells of 
Purkinje. 
the section. Their central side is round, and in most cases has 
no processes. Often the usual rounded contour of the cell- 
body is broken by an angle, seemingly the remains of a broken 
process. Here and there a large non-branching axis-cylinder 
process is seen emerging from the base of a cell and pursuing 
a course parallel to the cortex. That these basal processes 
exist in all cases, and ultimately acquire a myelinic sheath, 
there is no doubt. (See Fig. 146.) 
From the peripheral side large arborescent processes spring, THE CEREBRAL GANGLIA. 
319 
which pursue quite a direct course through the external or 
granular layer and disappear when near the periphery. The 
primary processes, one or two in number, have a tendency to 
spring from the cell-body at an obtuse angle, and give off at 
almost right angles to themselves the straight peripheral pro- 
cesses already mentioned. The nuclei of these cells are oval 
and coarsely granular; the nucleolus is round and small. 
The cortex proper consists of a granular matrix vertically 
striated by the cell-processes and parallel blood-vessels. There 
is also a moderate sprinkling of small round cells and nuclei 
similar to those in the third layer. The cortex is very vascular. 
THE CEREBRAL GANGLIA. 
As examples of these structures the optic thalami and cor- 
pora striata may be taken. They are collections of gray matter 
through which part of the fibres, emanating from the crura to 
help form the corona radiata, pass. 
In the corpus striatum these fibres pass through in bundles 
visible to the naked eye, which gives to this body its striated 
appearance. These bundles radiate toward the periphery of 
the body, thus leaving ever increasing spaces between them. 
These spaces at the base of the body, at the point of entrance 
of the bundles from the crura, are narrow, filled with nerve- 
fibres running in horizontal, vertical, and diagonal directions, 
seemingly commissural in nature, and multipolar cells few in 
number, large, and resembling somewhat cells of the anterior 
horns of the spinal cord, whose processes mingle with the fibres 
mentioned. Nearer the periphery of the organ, where the bun- 
dles of fibres are more widely separated, the intervening mass of 
fibres and cells abruptly changes to a finely granular gray ma- 
trix, holding in its substance numerous small blood-vessels 
and small nerve-cells, mostly round—some, however, triangular 
in shape, similar to those of the second layer of the cere- 
bral cortex. They have large nuclei and many delicate pro- 
cesses. 
The optic thalami consist of a mixture of gray matter and 
fibres, not, however, so regularly arranged as in the corpus 
striatum. The gray matter contains a few oval cells having 
many delicate processes. 
The cerebral ventricles.—Continuous with the central canal 320 
MANUAL OH HISTOLOGY. 
of the cord, and doubtless like it in function, the cerebral ven- 
tricles resemble it in their structure. They are lined through- 
out with a structure called the ependyma. This consists first 
of a finely granular layer covering all the nervous matter 
bounding the ventricles. Besides the minute granules, this 
layer contains a few small nuclei here 
and there, but no fibres. On its free 
surface rests a single layer of cylin- 
drical epithelium. The cells of this 
layer have square free ends, while 
they are anchored by one or more 
delicate processes which emerge from 
the attached end and pierce the sub- 
jacent granular-matrix. These epi- 
Fig. 147.—Diagram illustrating the 
structure of the ependyma of the cere- 
bral ventricles. 
thelia in the fresh state undoubtedly have cilia. This layer 
of epithelium is apt to be arranged in folds, giving a section 
of the ependyma a wavy appearance. 
The choroid plexus of the lateral ventricles has for its basis 
an artery which enters the descending horn of the lateral ven- 
tricle from the base of the brain. This artery gives off along 
its course short arterial trunks which repeatedly subdivide, and 
each ultimate arteriole terminates in a convoluted capillary 
loop, resembling the Malpighian tuft of the kidney. Some 
of the twigs seem to end in a cse- 
cal extremity ; but it is doubtful 
whether they do, the preparations 
giving this appearance being prob- 
ably artificial. The peculiarity of 
the choroid plexus is that all the 
vessels composing it, large and 
small, are covered by a layer of 
polyhedral epithelial cells, each 
having one, sometimes two large 
nuclei. This presents a beautiful 
example of the so-called tesselated 
epithelium, each cell being sepa- 
Fig. 148.—Diagram showing structure 
of the choroid plexus of the lateral ven- 
tricles. 
rated from its neighbor by a transparent intercellular sub- 
stance. This epithelial covering causes the tufts of the choroid 
plexus to resemble, in a degree, the villi of the chorion. The 
best plan in studying the choroid plexus is to use hsema- 
toxylon, or alcoholic specimens slightly teased. THE CEREBRAL GANGLIA. 
321 
The cerebral dura mater differs from the spinal in the fact 
that, its outer surface serving as periosteum, it lacks the layer 
of loose connective tissue present in the spinal dura mater. 
Its bulk consists of two layers of dense fibrous tissue running 
in opposite directions. The inner serous surface is coated with 
endothelium and lymphatics. The outer or periosteal surface 
is the most vascular. The cerebral differs from the spinal arach- 
noid only in being perhaps a little more closely attached to 
the pia mater. The pia mater of the brain is extremely vascu- 
lar, and shows more beautifully than the spinal membrane the 
system of perivascular spaces. 
The cerebral cortex.—The cerebral cortex is a thin sheet of 
gray matter spread on the outer surface of the hemispheres. 
The outer surface of the hemispheres is grooved by furrows 
(sulci) less deep in proportion to their size, and less regular 
than those of the cerebellum. The convolutions produced by 
these sulci, although seemingly very irregular, still have a cer- 
tain symmetry in different brains by which they can be classi- 
fied and named. A definite knowledge of these facts is neces- 
sary for an understanding of the current literature on the 
subject and of properly recording cases. 
The fetal hemisphere at an early date is smooth. Furrows 
soon begin to appear, the first and most important of which is 
thq fissure of Sylvius, extending upward and backward, from 
about the anterior third of the base of the brain, and they?s- 
- of Rolando, running from near the posterior extremity of 
the fissure of Sylvius upward to the superior longitudinal fis- 
sure. One after another the other fissures appear, till in the 
adult brain they seem innumerable. Even here, however, there 
is a certain constant arrangement of fissures and convolutions 
on which a nomenclature may be based. 
The original fissures of Sylvius and Rolando remain. From 
the anterior inferior part of the frontal lobe three furrows run 
obliquely upward and backward toward the two fissures just 
named, dividing the frontal region into the three frontal con- 
volutions, while a convolution in front of the fissure of Rolando 
receives the name of the ascending frontal or anterior central 
convolution. A similar convolution behind the fissure is called 
the ascending parietal or posterior central convolution. The 
parietal region is irregularly divided from above downward, 
as is also the temporo-sphenoidal and occipital region. The 322 
MANUAL OF HISTOLOGY. 
base of the brain is also divided into a series of basal frontal, 
temporal and occipital convolutions. By far the most impor- 
tant region of the cortex, according to our present knowledge, 
is that along the fissures of Sylvius and Rolando, the so-called 
motor tract of the hemispheres. The exact physiological func- 
tions of the anterior frontal, the occipital, temporal, and basal 
Fig. 149.—Modified from Ferrier; letters and figures the same: S, fissure of Sylvius; c, fissure of 
Eonaldo; po, parieto-occipital fissure; A, ascending frontal gyrus; B, ascending parietal gyrus; F2, 
third frontal gyrus ; P2/i gyrus angular is ; circle 1., seat of lesions which (on the left) cause aphasia; 
circle 11., seat of lesions which convulse or paralyze the upper extremity of the opposite side; dotted 
circle 111., seat of lesions which probably convulse or paralyze the face on the opposite side; dotted oval 
IV., seat of lesions which probably convulse or paralyze the lower extremity of the opposite side. These 
districts receive their blood-supply chiefly from the middle cerebral artery.—From Lectures on Localiza- 
tion by Dr. F. C. Seguin: N. Y. Medical Record, October 19,1878, p. SOI. 
regions of the hemispheres, is not known, inference, however, 
making them the seat of general and special sense, vaso-motor, 
psychic centres, etc., etc. 
The middle or fronto-parietal region, however, is the proven 
seat of motor centres for the face, limbs, and body, and the 
faculty of articulate language. The centre for speech occu- 
pies the region at the base of the third frontal convolution 
and the island of Reil on the left side, a similar location on 
the right side being occupied by a centre for articulatory 
movements. A little higher on the ascending frontal and 
parietal convolutions is an area having control over the move- 
ments of the tongue and face. Still higher is found a larger 
space, the centre for the arm of the opposite side. A larger 
space at the junction of the fissure of Rolando and the su- THE CEREBRAL GANGLIA. 
323 
perior longitudinal fissure, including a tract on tlie inner 
aspect of the hemisphere, called the paracentral lobule, is the 
centre for movements of both extremities, especially the lower. 
On account of the anatomical variability of the convolutions 
in different brains, these centres must be allowed some lati- 
tude, and should not be made so small and exactly located 
as they are by some authors. Their location has been pretty 
definitely determined, however, by experimentation on animals, 
and lesions in man, such as trauma- 
tisms, neoplasms, abscesses, hemor- 
rhages, atrophy following amputa- 
tions, retarded development, etc. 
Possessing such important proper- 
ties we should naturally expect the 
cerebral cortex to be a very complex 
structure, and so it is. 
Minute structure of the cortex.— 
In order to get a satisfactory view of 
the elements of the cortex, great care 
has to be exercised in making sections. 
It is not enough to make a section 
exactly perpendicular to the cortex. 
The plane of the section must exactly 
coincide with the direction of the fibres 
of the corona radiata as they enter the 
convolution. This can be rather easily 
accomplished by paying close atten- 
tion to the arrangement of the white 
Pig. 150.—Diagram showing the 
elements and relation of parts in the 
cerebral cortex. (See text.) 
and gray matter in the piece from which the sections are to 
be made. Cuts with any obliquity will give erroneous impres- 
sions as to the exact shape and structure, especially of the 
cellular elements of the cortex. The cortex cerebri is generally 
divided into five layers, but it is easily divisible into three only. 
The outer layer, lying immediately under the pia mater, is 
more transparent than the rest, and is composed of a fine net- 
work of neuroglia containing many quite large openings, giving 
it a spongy appearance. It also contains a few large, round 
nuclei, and a small number of triangular nerve-cells. 
The second layer, thicker than the first, consists of a gray 
basis-substance, dense and granular, holding an immense num- 
ber of small, triangular and conical cells, their apex being di- 324 
MANUAL OF HISTOLOGY. 
rected toward the periphery and often drawn out into a slen- 
der axis-cylinder process, while from their base several delicate 
processes are given off. These cells all have large nuclei and 
nucleoli. Here and there are seen larger conical cells, which 
will be described with the next layer. The characteristic fea- 
ture of the second layer, however, is the presence of a great 
number of small, round cells and free nuclei similar to those in 
the third layer of the cerebellar cortex. 
In the third layer the matrix is still more dense, and con- 
tains, besides a few small triangular cells, round cells, and free 
nuclei, a large number of large conical corpuscles, the so-called 
“giant cells” of the cortex, the distinguishing feature of this 
layer. When isolated from their surroundings these cells ap- 
pear like cones winch taper gradually from a broad base to a 
very slender apex, which, when it attains the size of an axis- 
cylinder, can be traced for a long distance without showing a 
division. This undoubtedly terminates in a myelinic nerve- 
fibre. The base of the cell is not square, but crenated and 
notched by the giving off of numerous delicate basal processes 
which are lost in the granular matrix. 
The cells all have nuclei and nucleoli, most of which are 
round, but some of which seem also to have a triangular shape 
corresponding to the cell-body. The cells average 25 \x. in 
diameter. A great difference is made in the apparent shape of 
the cell by obliquity of the section. If the line of section is 
moderately oblique, it shortens the cells ; if still more oblique, 
it makes them very short and blunt; while if the section is at 
right angles to their axis, all the cells appear round and of 
various sizes. In the deepest parts of this layer the giant-cells 
gradually disappear, and the gray matter of the cortex merges 
into the white matter. In the two inner layers of the cortex 
there are seen many fibres and bundles of fibres having a ver- 
tical direction, which, with the blood-vessels (the largest of 
which being perpendicular to the surface), give the cortex a 
somewhat striated appearance. 
We see, then, that the only difference between the second 
and third layers of the cortex is the greater number of small 
cells in the second and the greater number of large cells in the 
third, while the division of the third layer into three, as is 
accepted by most authors, seems purely arbitrary, there being 
a gradual gradation into the white substance. BIBLIOGRAPHY. 
325 
Some writers1 lay mucli stress on the difference of structure 
of the cortex in different regions of the hemisphere. It is true 
that, in the non-excitable or sensory regions, the cortex is thin- 
ner and perhaps less highly organized; but here are met the 
same elements as form the cortex in the motor region (centre, 
for the arm, for instance). (See Fig. 150.) Even the giant-cells 
are found less numerously than in the motor regions. Another 
fact demands attention, that is, that the structure of the cortex 
is the same at the bottom of a fissure as on the surface of a 
convolution, and for this reason lesions of the sides and bottom 
of fissures should receive as much attention as those of the 
surface of the convolutions, implicating, as they do, equally im- 
portant structures. 
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Sevan Lewis and Clarke, H. The Cortical Lamination of the Motor Area of 
the Brain. Proceedings of the Royal Society, Vol. XXVII. 1879. 
Cerebellum. 
Hess, N. De cerebelli glorum textura. Dorpat, 1858. 
ScnuLTZE, F. E. Ueber den feineren Bau der Rinde des kleinen Gehirnes. Ros- 
tock, 1863, 
Central Nervous System. 
Deiters, Otto. Untersuchungen iiber Gehirn und Riickenmark des Menschen und 
der Saugethiere. Braunschweig, 1865. 327 
BIBLIOGRAPHY. 
Deecke, Theodore. Perivascular Spaces in the Nervous System. American Jour- 
nal of Insanity. January, 1874. 
Waldeyeu. Beitrage zur Kenntniss der Lymphbahnen des Centralnervensyst. 
Arch. f. mikr. Anat. 1879. 
Rest even, W. H. The Structure and Functions of the Olivary Bodies. St. Bar- 
tholomew’s Hospital Reports. 1879. 
See, Marc. Sur la communication des cavites ventriculaires de I’encephale avec les 
espaces sous-arachnoi’diens. Revue mensuelle. 1879. 
Broca, P. Localisations cerebrates. Revue d’anthropol. 1879. 
Betz. Structure de I’ecorce cerebrale. Rev. d’anthrop. 3. S. IY. 426-438. Paris, 
1881. 
Laehr. Pacchionischen Granulationen. Allg. Ztg. f. Psychiat. XXXVIII. 101- 
105. 1881. 
Spitzka, E. C. Notes on the Architecture of the Oblongata. New York Med. 
Journ. XXXIV. 333-240. 1881. CHAPTER XX. 
THE EYE, 
C. H. WILLIAMS, M.D., Boston, Mass. 
The eyelids are very complicated structures. Their exter- 
nal coating is formed of skin, which is modified for the special 
purpose it has to serve in this situation. Beneath the skin is a 
loose sheet of connective tissue ; still more internally is the lit- 
tle orbicularis palpebrarum muscle ; behind this again is loose 
connective tissue, which shades oil gradually into the tarsus. 
This latter is not formed of cartilage, as was formerly sup- 
posed, but of dense fibrous tissue. The conjunctiva tarsi 
lines the inner surface of the tarsus. The skin of the lids 
exhibits the usual layers of horny, serrated, and cylindrical 
epithelium. At the upper portions the papillae are sparsely 
developed and short, but they gradually increase in size and 
number as they approach the free edges. A peculiarity of this 
skin are the pigment-cells, which are scattered throughout the 
cutis. They are more abundant in brunettes than in blondes. 
At the confronting margins of the lids are found the cilia 
or eyelashes, which resemble the ordinary larger hairs in their 
formation and mode of growth ; they are placed in two or 
three rows, are well supplied with pigment, and have a definite 
direction given to them by the deep follicles from which they 
grow. 
Ordinary sweat-glands are quite numerous, especially in the 
upper portions of the lid ; at the lower border we occasionally 
find them in a modified form, opening into sebaceous follicles 
near or just behind the cilia; they have a long and wide ori- 
fice, and the tubules are filled with fine granular matter, con- 
taining occasional roundish masses resembling particles of 
albumen. 
Beneath the cutis is a loose connective-tissue layer through THE EYE. 
329 
which numerous blood-vessels and nerves pass; behind this, 
and covering the whole extent of the lid, are bundles of the 
orbicularis palpebrarum ; some small fasciculi of this muscle 
are also found at the lower and inner angle of the lid, enclosing 
the openings of the Meibomian glands. These bundles, known 
as the musculus ciliaris Riolani, have fibres which are among 
the smallest of the striped variety of muscular tissue. 
Behind this layer is a thin sheet of loose connective tissue, 
which merges without any sharp boundary line into the tar- 
sus ; this latter body forms a leaf-shaped plate about twenty 
millimetres in length by one millimetre in thickness, and is 
composed of very dense connective-tissue fibres separated only 
by minute lymph-spaces; it has few blood-vessels or nerves, 
and serves to give the requisite stiffness to the looser tissues of 
the lid. 
The Meibomian glands are imbedded in the tarsus. Their 
excretory ducts, which are directed at right angles to the pal- 
pebral margin, have their openings on the surface of the lid 
near its posterior angle. They are lined with epithelium, which 
at the external orifice is similar to that in the superficial parts 
of the skin ; more internally it is serrated, while in the acini of 
the gland it has a cuboidal shape. These glands have a straight 
central tube, around which the acini are clustered, and into 
which they discharge the sebum, a material composed of epi- 
thelial cells that have undergone fatty degeneration. This 
oleaginous substance serves to moisten the edges of the lid and 
to prevent the overflow of tears. 
Above the Meibomian glands, and in part imbedded in the 
tarsus, are the acinous glands, which have their openings on 
the surface of the conjunctiva fornicis. Above these glands 
the smooth muscular fibres of the little palpebralis muscle of 
Muller are inserted, through a tendon, into the upper part of 
the tarsus; the fibres of this muscle are quite large and have 
peculiar irregular cells with pigmented nuclei scattered 
throughout them. 
To prepare sections from the lids they should be pinned flat 
on a piece of cork and then immersed in Muller’s fluid1 for 
eight days. After being washed in water they are placed in 
absolute alcohol until sufficiently hard ; or they may be hard- 
1 See chapter on General Methods. 330 
MANUAL OF HISTOLOGY. 
ened by placing in the ordinary £ per cent, solution of chloride 
of gold. This last method shows very clearly the nerves of 
the lid and conjunctiva, which take a deep violet or mauve 
color. For rapid work the lids may be hardened in a saturated 
solution of picric acid. They may then be stained with picro- 
carmine or hsematoxylon, and mounted in glycerine or balsam. 
(See chapter on General Methods.) 
The caruncula laclirymalis is a small, rounded mass of 
skin; it is placed between the lids at their inner angle, and 
contains hairs, vessels, and glands, such as are found else- 
where in the cutis. Its office is to prevent the overflow of tears. 
The conjunctiva.—Just behind the tarsus, and separated 
from it by a thin layer of fibrillated connective tissue, is the 
conjunctiva, which, after lining the inner surface of the lid, 
passes backward as a loose connecting fold (fornix) to the 
sclera, over which it is reflected forward as far as the margin 
of the cornea. The conjunctiva consists of an external or 
epithelial layer and a tunica propria or proper investing mem- 
brane. There is also a subconjunctival layer. 
The lower portion of the conjunctiva, where it takes its 
origin from the margin of the lid, is quite smooth ; but near 
the upper edge of the tarsus it becomes more or less infiltrated 
with lymph-cells, and is thrown into numerous folds, which 
have sometimes been mistaken for glands. The epithelial ele- 
ments of this part vary much in shape ; in general there are 
two layers: a superficial one, composed of cylindrical bodies 
which are a continuation of the superficial strata of the skin, 
and a deeper one of small, round cells, representing the changed 
cylindrical elements of the Malpighian layer or rete mucosum. 
The tunica propria consists of fine connective-tissue fibres, 
in which a few elastic fibrillse are interspersed. The subcon- 
junctival layer resting immediately upon the tarsus is very 
thin. That part of the conjunctiva forming the fornix has an 
abundant subconjunctival tissue, which is composed of loose 
elastic fibres and vessels ; the epithelial layers are also thicker 
here, and small racemose glands, supposed to secrete mucus, 
are also found there. 
On the conjunctiva covering the bulb the epithelium con- 
tains here and there the large mucus-cells corresponding to 
the goblet-cells of the intestines. It gradually begins to change 
its character and passes over into the variety which is seen in THE EYE. 
the cornea, and, in fact, is continuous with it. The tunica 
propria has an abundant supply of blood-vessels, and is loosely 
connected with the sclera by fibres, which become more numer- 
ous and firm in the vicinity of the corneal margin. 
The nerves of the conjunctiva may be seen by cutting small 
pieces of fresh conjunctiva from a pig or calf and examining 
them in aqueous humor, or in a 1 per cent, aqueous solution of 
common salt—care being taken to support the cover-glass at 
the sides, in order to avoid pressure. The nerve-fibres can then 
be seen passing under the epithelium ; they can be distin- 
guished with certainty by their annular constrictions (anneaux 
constricteurs); after penetrating a short distance, however, 
they lose their medullary sheath and form open networks 
under the epithelium ; a few fibres find their way toward the 
surface between the epithelial cells. 
The gold method is of special use in exposing the finer 
nerve-branches. The question of the manner in which the 
nerves ultimately end is still a point in dispute. 
The lymph-spaces of the conjunctiva are quite numerous, 
especially near the corneal border; here they are narrow, and 
finally pass forward to unite with the tymph-spaces of the cor- 
nea, from which they can be injected by means of a solution 
of alkanet-root in turpentine.1 
The normal conjunctiva does not have any true papillae, but 
on the tarsal portion the surface often has small papilliform 
projections covered with epithelium. 
The cornea.—This tunic is covered with stratified epithe- 
lium {a), comprising layers of flat, serrated, and cylindrical 
cells. Directly beneath these is the anterior limiting or Bow- 
man's membrane {b); this is a clear, homogeneous stratum, 
which differs from the substantia propria of the cornea only in 
containing no lymph-spaces or cells. It can be divided up 
into the same fine fibres as the cornea itself, and its inner bor- 
der has no distinct limit, the fibres passing directly into the 
corneal tissue ; when this layer has been destroyed, as by a 
perforating ulcer or wound, it is not regenerated. 
The substantia propria of the cornea (b, c) is made up of 
lamellae, like the leaves of a book ; these lamellae, which at 
ffrst appear homogeneous, can be separated into fine fibres, Just 
1 See chapter on General Methods. MANUAL OF HISTOLOGY. 
like other connective-tissue membranes, by dissolving out the 
cementing substance in a 10 per cent, solution of common salt. 
With the exception of the fibres arcuatce, which curve for- 
ward through several strata in the anterior portions of the 
cornea, the fibres pursue the same direction as the layers ; but, 
although most of the fibres run parallel to the surface of the 
cornea, yet they may have a different direction in each layer, 
Fig. 151.—Meridional section through the cornea of the human adult, from an eye hardened in Mill- 
er’s fluid. The section was colored with carmine, and made transparent by the oil of cloves. Kollett. 
so that when viewed from above the fibres will appear to cross 
one another. This explains the formation of the stellate fig- 
ures which are sometimes observed after the injection of fatty 
substances into the cornea, or by the infiltration of bacteria 
between the fibrils. 
In the intertibrillar material are found the lymph-canals 
and spaces, which contain the fixed corneal corpuscles (Fig. 
152). These spaces are stellate and broad when seen from above, 
but thin and spindle-shaped on side view; they have numer- 
ous branches and bran chiefs given off from them at right 
angles (lymphatic channels) (Fig. 153, A). The spaces and 
branches usually lie in the plane of the lamellse, anastomose 
freely with one another, and are filled with the corneal corpus- 
cles and lymph (Fig. 152, B). THE EYE, 
In life these fixed bodies nearly fill the lymph-spaces and 
conform to their size and shape ; they are fiat corpuscles, usu- 
ally nucleated, and have short, sharp-pointed processes, which 
pass out into the minute lymph-canals. In the lymph-spaces 
of the cornea are also found, even in normal conditions, a few 
migratory cells, resembling white blood-corpuscles; they are 
very numerous when the cornea has been irritated, and can 
be seen in a frog's cornea, which 
has been kept five to fifteen 
minutes in serum or aqueous 
humor in a moist chamber, and 
examined without pressure on 
a warm slide. 
Beneath the substantia pro- 
pria of the cornea we find the 
posterior limiting layer, or 
BescemeV s membrane (d) (Fig, 
lol). This is transparent, ap- 
parently homogeneous, rolls up 
when cut, is intimately connect- 
ed with the posterior fibres of 
the cornea proper, and is lined 
on its inner surface with endo- 
thelium (e). It contains no cel- 
Pig, 152. —Lymph spaces and canals, A; fixed 
corneal cell, partly filling these spaces, B. After 
Waldeyer. 
lular bodies, but, like the anterior limiting layer, can be sepa- 
rated into fibrillse, and appears to represent a concentration of 
the corneal fibres rather than a separate structure. 
The endothelium is a single layer of flat cells lining the 
anterior chamber. Blood-vessels are found only in the normal 
cornea at the periphery, where they form a fine network con- 
necting with the conjunctival and scleral vessels. 
The nerves enter the cornea at the posterior part of the 
periphery ; they soon lose their neurilemma and medullary 
sheath, and pass forward obliquely, as small axis-cylinders, 
toward the epithelial layer; here they divide up into branch- 
lets, often having a ganglionic enlargement at the point of divi- 
sion. Under the epithelium these delicate fibres form a net- 
work which sends some very minute filaments upward between 
the epithelial cells. Their further course is unknown. 
To separate the cornea into its constituent fibres, small pieces 
should be soaked for twenty-four hours in a concentrated ph 334 
MANUAL OF HISTOLOGY. 
cric acid solution ; they can then be washed in water and easily 
picked to pieces. In order to see the arrangement of the fibrillse 
in the different layers, the cornea of a rabbit should be pricked 
with a needle in several places; then some highly infectious 
fluid, as the exudation in puerperal peritonitis, is to be brushed 
over the surface, and in a few days an infiltration will have 
taken place throughout the interfibrillar substance. We shall 
then see the lines of pus-cells crossing one another in different 
directions, and sometimes collections of micrococci forming 
stellate figures. 
A very delicate preparation of the fixed corneal cells may 
be made by removing a fresh cornea, and then immersing it 
from three to six hours in aqueous humor, in a moist chamber. 
In examining it take care, as before mentioned, to avoid any 
pressure upon the cover-glass. 
It is easier, however, to demonstrate the cells and lymph- 
spaces by staining with silver or gold. To do this the nictitat- 
ing membrane of a live frog should be cut off or held to one 
side by an elevator ; the exposed cornea is then placed near the 
mouth of a test-tube, in which some water has been raised 
to the boiling point; when the epithelium begins to appear 
opaque it should be carefully wiped off with a fine cloth; a 
i per cent, aqueous solution of nitrate of silver is then applied; 
when the cornea has become thoroughly white by this method, 
it is to be removed, washed in a weak solution of common salt, 
placed in distilled water, and exposed to the light until it be- 
comes brown. It should then be cut at the edges and mounted 
in glycerine. In ten or fifteen minutes it will be transparent 
and ready for examination. Instead of removing the epithe- 
lium by steam, a solution of silver nitrate (4 per cent.) may be 
used, the lids being held out of the way until the epithelium 
appears whitish ; this outer layer is then removed, and the 
same process repeated as before. The substantia propria as- 
sumes a brown color, and the corpuscles appear as lighter spaces 
in it. The nuclei may be exposed by haematoxylon. 
The best preparations, both for the lymph-spaces and the 
nerves, are made with chloride of gold. A fresh cornea, pref- 
erably one from a live pigeon, is removed immediately after 
decapitation and immersed for five minutes in lemon-juice, 
then washed in distilled water, placed for fifteen minutes in a 
1 per cent, solution of chloride of gold, again washed, and this THE EYE. 
335 
time soaked for twenty-four hours (well protected from the 
light) in a 2 per cent, solution of formic acid. After another 
washing in distilled water the cornea should be cut in two and 
placed in glycerine; one portion can then be separated into 
thin layers, by tearing with fine forceps or needles. 
Examine in glycerine for the corneal corpuscles, nerves,' 
and lymph-spaces, which latter appear dark on a light blue 
or red background ; or the piece may be imbedded in wax or 
some such material, and sections made parallel to the surface 
of the cornea. The remaining half of the specimen is to be 
imbedded or held in liver or pith. Transverse sections may 
then be made. These will exhibit on lucky sections the fine 
plexuses of nerve-filaments under the epithelium, with occa- 
sional fibres passing up between the individual corpuscles. 
The different layers of the cornea will be well shown, also the 
narrow corneal cells (as seen on side view), together with the 
remains of the endothelial layer on the inner surface. 
The peripheral portions of the cornea are particularly inter- 
esting. We have here the transitions from cornea to conjunc- 
tiva and sclera, the origin of the ciliary muscle, the ligament 
of the iris, and the numerous vessels of the part. 
The epithelium of the cornea (a) forms a gradual transition 
into the epithelium of the conjunctiva, but the anterior limit- 
ing membrane (Bowman’s) becomes thinner as it approaches 
the edge of the cornea, until finally it merges with the fibres 
of the anterior corneal layers into the tunica propria of the 
conjunctiva. 
No sharp boundary line has been demonstrated between 
the cornea and the sclera. Under the microscope the fibres 
appear to have no distinct limit; the lymph-spaces also of the 
cornea are continued directly into the sclera, and the scleral 
and corneal fixed corpuscles are much the same. 
The posterior limiting membrane [DescemeVs) (c), like the 
anterior, becomes gradually thinner and loses itself in a small 
bundle of scleral fibres which surround the edge of the mem- 
brane and form the anterior support to the ligamentum pec- 
tinatum iridis. 
The endothelium (Fig. 153 e,) passes uninterruptedly over 
this ligament {e') and is reflected forward over the anterior sur- 
face of the iris (e") to the edge of the pupil. 
In the angle between the iris and cornea, forming buttresses, 336 
MANUAL OF HISTOLOGY. 
as it were, to hold the iris in position, is the ligament of the 
iris (d), composed of loose connective tissue with an abundant 
open mesh work, enclosing spaces {Fontana?s spaces), (/), which, 
on the one hand, connect with the anterior chamber by small 
openings lined with endothelium, and on the other with the 
lymph-spaces of the cornea and sclera, as may be shown by 
injecting a solution of aniline blue into the anterior chamber. 
Fio. 153.—Corneal margin from a meridional section of the human eye : a. a', external epithelium of 
the cornea; a', a", epithelium of the conjunctiva bulbi; b, b'. b', corneal tissue; bb', b'', b", sclerotica ; 
k, conjunctiva; v, v', canal of Schlomm; c, c', membrane of Descemet; d, process of the iris: J, iris; e. 
endothelium of the membrane of Descemet; e'. e', eof the ligamentum pectinatum iridis; e", e", e", of 
the iris ;/, mesh work of the space of Fontana; m, musculus ciliaris. Bollett. 
At the inner part of the sclera, close to its Junction with the 
cornea and the ligament, is the canal of Schlemm («, r>'), a ring- 
shaped passage, oval on section. It is lined with a single layer 
of endothelium, varies in size in different specimens, often ap- 
pearing as if divided into two parts, and, according to Wal- 
deyer, probabty connects with the anterior chamber and also 
with the scleral veins. 
Through this passage and Fontana?s spaces the fluid of the 
anterior chamber is supposed to escape from the globe, and it 
is worthy of note that in glaucoma, with increased intra-ocular 
tension, we find the iris attached to the periphery of the cor- THE EYE. 
nea over a circular space wliicli would entirely cover these 
probable channels of exit. 
Preparations of these parts can be made from eyes which 
have been placed in Muller’s fluid while quite fresh and al- 
lowed to remain in it three to four weeks, the fluid being re- 
newed from time to time. Hsematoxylon is well adapted for 
coloring them, and they may be preserved in glycerine. 
The sclera.—ln the sclera we find the same minute struc- 
tures as in the cornea, i.e., bundles of fibres, cementing sub- 
stance, lymph-spaces, and fixed corpuscles. The fibres, how- 
ever, are not laminated, as in the cornea, but run in various 
directions, weaving a very dense tissue, so that the lymph- 
canals have a correspondingly tortuous course. 
Chemically there is a difference between the two, as the 
sclera is found to yield on boiling a true connective-tissue 
gelatine; the cornea, on the other hand, a substance resem- 
bling chondrine. We find also in the sclera, near the foramen 
for the optic nerve, a few pigment-cells. 
The sclera is covered by the conjunctiva from the corneal 
border to the insertion of the recti muscles, and the fibres of 
the subconjunctival tissue pass directly into it. From the en- 
trance of the optic nerve to these muscular insertions, and even 
passing up between them, the scleral portions of Tenon's cap- 
sule form the covering, which consists of delicate filaments of 
connective tissue passing directly into the sclera itself. On the 
inner surface the sclera is covered with a large-celled endothe- 
lium lining the perichoroidal %pace. At the round opening 
for the entrance of the optic nerve, the outer fibres of the optic 
nerve sheath pass directly into the outer scleral layers; the 
inner portions of the sheath partly mingle with the inner 
layers of the sclera, and partly, after the addition of some true 
scleral fibres, form the lamina cribrosa, a fine, sieve-like net- 
work of fibrous tissue, which stretches across the opening in 
the sclera on a level with its inner surface. This lamina can 
be easily shown in specimens where the delicate nerve-fibres 
which pass through its openings have been macerated out. 
The sclera is perforated in the equatorial region by the 
trunks of the rence vorticosce; they are accompanied by the 
lymph-vessels which form the connection between the pericho- 
roidal and Tenon’s lymph-spaces. The direction of the canal 
through which they pass is so oblique that it is supposed to be 338 
MANUAL OF HISTOLOGY. 
easily contracted in diameter by any increase in intra-ocular 
pressure. 
The arteries of the sclera, with their thick adventitial coats, 
the peculiar sheaths of the veins and capillaries, as also the 
nerves, are best studied in hematoxylon preparations. A solu- 
tion of silver nitrate (a quarter to one per cent.) will expose 
the endothelial cells, while sections of the tissue may be 
made from specimens preserved in alcohol or Muller’s fluid. 
The tunica vasculosa, consisting 
of the choroid, ciliary body, and 
iris, forms one continuous mem- 
brane through which the principal 
blood-supply of the eye is carried. 
The choroid.—This tunic lines 
The sclera from the entrance of the 
optic nerve to the junction of sclera 
and cornea, and is united to it at 
those points ; over the remaining 
portion there is a loose connection 
formed by scattered fibres and the 
numerous vessels and nerves which 
pass through the sclera to the cho- 
roid. The meshes of the open 
network between the layers of 
the choroid and the sclera form 
lymph-sacs the perichoroidal 
spaces—which connect with the sac 
enclosed in Tenon’s capsule, and 
this in turn unites with the su- 
fig. 154. - sciera,«; choroid, ch; ret- 
ina, r; perichoroidal space, pi h; lamina 
suprachoroidea, sc; lamina chorio-capilla- 
ria, cc; lamina vitrea, v ; layer of pigment- 
cells between choroid and retina,p. After 
Merkel. 
pra-vaginal space surrounding the 
~„ - . ' 
Sfleatll Ot the ODtIC HCIVe. 1116 
. n 
dlOrOld COHSIStS Ot SCVeml layers, 
" ' 
with limits not distinctly marked. 
The lamina suprachoroidea (Fig. 154, sc) lies next the 
sclera, and consists of fine elastic and connective-tissue fibres, 
holding in their meshes pigmented and transparent cells: 
the first are stellate, often with projecting arms by which 
several are joined together; the latter resemble lymph-cor- 
puscles. 
The layer of large vessels is traversed by branching arteries 
and veins ; between them are numerous pigmented corpuscles, THE EYE. 
339 
while the whole is held together by the firm connective-tissue 
network which extends throughout the entire choroid. 
The lamina chorio-capillaris {cc) consists of a network of 
fine vessels, interspersed with pigment, and extends over the 
whole inner portion of the choroid. 
The vitreous layer («) is very closely connected with the 
lamina chorio-capillaris; though it appears homogeneous, 
fibres may be detected in it after long maceration in a ten per 
cent, solution of common salt. Where this layer covers the cil- 
iary processes the surface is no longer smooth, but has fine, 
elevated ridges upon it; here the membrane also is thicker, 
and is more easily affected by reagents. 
The dense lamina of hexagonal pigment-cells between the 
choroid and retina has sometimes been classed with the former, 
although it belongs more properly to the retina. 
The long and short posterior, and the anterior ciliary arte- 
ries, furnish the numerous blood-vessels which constitute the 
great mass of the choroid. 
The short posterior ciliary arteries, four to six in number, 
give off some twenty branches which penetrate the sclera, 
pursuing a straight course near where the optic nerve enters ; 
then, continuing their course in a tortuous manner, they divide 
into fine networks which supply the greater part of the lamina 
chorio-capillaris. About the entrance of the optic nerve they 
also form a network of fine vessels, and even send occasional 
branches to anastomose with vessels from the sheath and cen- 
tre of the optic nerve. 
The two long ciliary arteries penetrate the sclera in a very 
oblique course, a little anteriorly to those last mentioned, and 
in the horizontal meridian; they pass forward in the outer 
lamina of the choroid without branching until they reach the 
ciliary muscle ; here they divide, and penetrating the muscle, 
form near the periphery of the iris a circle {circuius arteriosus 
iridis major) by uniting with the artery of the opposite side. 
The anterior ciliary arteries, eight to ten in number, arising 
from muscular branches of the ophthalmic artery, penetrate 
the sclera near the insertion of the recti tendons; they also 
unite with the circle just described, which forms the principal* 
distributing point for the vessels of the iris and ciliary body. 
From this circle also are sent back a few small branches to unite 
with the choroidal capillaries, and there is formed the sole con- 340 
MANUAL OF HISTOLOGY. 
nection between the short posterior or choroidal arteries pro- 
per and those which supply the circulus arteriosus. A small 
amount of the blood which returns from the capillaries of the 
choroid, ciliary body and iris finds its exit from the eyeball 
through the veins accompanying the anterior and posterior 
ciliary arteries, but by far the larger part is collected by the 
large veins in the outer layers of the choroid (venae vorticosae), 
converging so as to form four or six great trunks, which perfo- 
rate the sclera obliquely in the equatorial region, and empty 
into the ophthalmic vein. 
The long and short ciliary nerves supply the tunica vascu- 
losa with fibres from the third and fifth pair and the sympa- 
thetic. The long nerves, two or three in number, are branches 
of the nasal division of the ophthalmic nerve ; the short, ten to 
fifteen in number, arise from the ciliary ganglion. These nerves 
penetrate the sclera near the optic nerve, and then, passing for- 
ward on the outer portion of the choroid, form, in the ciliary 
muscle, a fine plexus with ganglionic corpuscles at the nodal 
points of the meshes; from this plexus fibres are distributed 
to the cornea and iris. 
At the junction of the anterior and middle thirds of the 
eyeball the choroid undergoes a change, the membrane be- 
comes thinner, the capillaries turn back toward the veins, only 
a few vessels continuing forward in a straight course. 
In this region the retina also undergoes a change and loses 
all its nervous elements, the connective tissue supporting fibres 
alone being continued forward under the name of thepars cili- 
aris retinae. The very narrow zone between the points where 
these changes occur and the irregular line formed by the begin- 
ning of the ciliary processes is called the orbiculus ciliaris, 
and the line of origin of these processes the ora serrata. 
The ciliary body.—Crossing the orbiculus, the choroid is 
seen raised in radial folds, some seventy in number, which in- 
crease in size until they reach the thickness of a millimetre. 
This increase is caused by the development of smooth muscular 
fibres in addition to the usual constituents of the choroid. 
These fibres arise just behind the canal of Schlemm, from 
the sclera and cornea ; passing backward, they together form 
a ring, which on section appears as a right-angled triangle, 
with the base turned toward the anterior chamber, and the hy- 
pothenuse toward the vitreous (Fig. 155). THE EYE. 
341 
This triangle consists largely of the fibres of the ciliary mus- 
cle, which are divided into meridional fibres, or those which 
occupy the side next the sclera, and radial fibres, which pass 
Fig. 155.—Section through the ciliary region of a hypermetropic eye. Ivanof. 
from the point of origin to the hypothenuse ; the circular fibres 
of Muller’s muscle lie next to the base of the triangle, and are 
concentrically arranged. 
In highly myopic eyes the meridional and radial fibres 
Pig. 156.—Section through the ciliary region of a myopic eye. Ivanof. 
are strongly developed (Fig. 156), while the circular fibres are 
scarcely seen, and the angle of the ciliary body at the point of 
origin is changed from a right to an acute angle. 342 
MANUAL OF HISTOLOGY, 
In very hypermetropic eyes, on the contrary, the circular 
fibres are abundantly developed (Fig. 155), the meridional fibres 
are shorter, while the angle at the point of origin of the mus- 
cle becomes somewhat obtuse, so that by these changes one can 
determine, even in a microscopic section, what considerable 
refractive error the eyes have had. 
The meridional fibres are either prolonged some distance 
into the stroma of the choroid and end in a delicate fringe, or 
they terminate at the anterior and outer layers of this mem- 
brane in stellate knots with fine anastomosing branches. 
The radial fibres form a looser network than the last, but 
also have the same terminal interlacement of their fibres; the 
circular fibres form fewer anastomoses, and only those bundles 
\yhich lie next to the radial fibres are extensively connected 
with them. 
The nerves of the ciliary body are derived from the plexus 
formed in its stroma by the ciliary nerves; the vessels are 
largely supplied from the circulus iridis major, lying in the an- 
terior part of the body. 
The iris arises from the anterior side of the ciliary body, 
and from the connective tissue surrounding the fibres of the 
ciliary muscle ; it is also attached to the cornea and sclera by 
the ligamentum pectinatum. (See Fig. 158). 
It consists of a loose connective-tissue stroma, which sup- 
ports a rich vascular network, a complete muscular structure, 
and the nerves. It is covered anteriorly by a continuation of the 
endothelium of the cornea, and posteriorly by a thick layer of 
pigment-cells continuous with those which line the ciliary body. 
The vessels arise from the circulus, have adventitial coats which 
are thick in proportion to their calibre, and pass radially to 
the margin of the pupil, where they form a network of fine 
capillaries, the circulus arteriosus iridis minor, ending final- 
ly in veins which return in the same general direction as the 
arteries, but lie beneath them, emptying finally into the venae 
vorticosae. 
Near the margin of the pupil, and forming a ring about 
it 1 mm. in breadth by TV mm. in thickness, is the sphincter 
muscle of the iris. It is composed of unstriped muscular tissue, 
and is situated in the posterior portion of the iris. 
The dilator muscle, at its inner border, is in close connection 
with the sphincter, and its fibres run radially to the periphery THE EYE. 
343 
of tlie iris, where they are woven into a thick anastomosing 
circle. 
The nerves of the iris are derived from the ciliary plexus; 
at the periphery they divide and scatter in various directions: 
the pale fibres to the posterior layers, forming a fine network 
about the dilator muscle; the fibres with a medullary sheath 
to the anterior portion; another set supplies the sphincter 
muscle—these being, in the order of description, the branches 
possibly of the sympathetic, sensory, and of the third pair. 
The posterior surface of the iris, which, near the pupil, rests 
upon the anterior capsule of the lens, is covered with a thick 
layer of densely pigmented cells, the uvea, which can rarely be 
so separated as to determine their shape, and which appear to 
have no distinct limiting membrane behind them. 
This layer extends from the pupil, where it meets the endo- 
thelium of the anterior surface, back to the pigment of the 
ciliary body, with which it is continuous and from which it can 
be distinguished by having no connective tissue covering it. 
The pigmented cells, which are more or less thickly scat- 
tered through the stroma of the iris, determine the color of 
the anterior surface. 
Transverse sections through the sclera and choroid are best 
made from eyes hardened in Muller’s fluid. An eye which has 
been injected with colored gelatine, introduced through the 
aorta after that vessel has been tied beyond the carotids, will 
show the fine meshes of the chorio-capillaris, when the pigment- 
layer covering the choroid has been brushed away under gly- 
cerine. Such injections are best made on albinotic rabbits. 
Good sections of the ciliary body can be made from eyes 
hardened in alcohol or Muller’s fluid, and the blood-vessels 
can be easily seen in injected specimens. The muscular tissue 
of this body and the iris may be examined in specimens treated 
with a 30 to 40 per cent, solution of potash. Carmine may 
then be used to color. The vessels of the iris are best seen in 
the eyes of a young albino rabbit, injected with colored 
glycerine or Berlin blue. 
The retina lines the whole inner surface of the choroid as 
far as the ora serrata; it is composed of nervous elements, 
connective tissue, and blood-vessels. 
The following division into well-marked layers from within 
outward has been generally adopted. (See Fig. 157). MANUAL OF HISTOLOGY. 
a, membrana limitans interna. 
b, optic nerve fibre-layer. 
c, ganglion-cell layer. 
d, inner granular layer. 
e, inner nuclear layer. 
f, outer granular layer. 
g, outer nuclear layer. 
membrana limitans externa. 
i, layer of rods and cones. 
Pigment layer, 
The fibres of tfie optic nerve generally lose their medullary 
sheath at the lamina cribrosa, and proceed 
thence as naked axis-cylinders through the 
opening in the choroid to the level of the 
retina, where they spread over its entire in- 
ner surface to form the nerve-fibre layer, 
which is thick in the vicinity of the nerve, 
but gradually decreases as it approaches 
the ora serrata, where it ends. 
At the macula lutea the fibres do not 
form a distinct layer, but, curving toward 
this spot from above and below, are lost 
in the layer of ganglion-cells, either entering 
them or passing on to the inner granular 
layer. 
The ganglion-cell layer consists of large 
branching cells in most places but one row 
deep, though near the macula there may 
be two or more layers. They are very 
transparent, have no visible cell-wall, and 
are provided with a varying number of pro- 
jecting arms ; when fresh they contain fine 
granular matter with a clear, large nuclei 
and nucleoli, and appear finely fibrillated. 
They receive an axis-cylinder on their 
inner side, and on the outer send out 
Pig. 167.—Transverse sec- 
tion of the retina. After Ze- 
hender. 
branches which ultimately divide into fine fibrillse, and are 
lost at the inner granular layer in a tangled network. It is 
probable, however, that some of these fibres are connected 
with the cells of the inner nuclear layer. 
The inner granular layer partly surrounds the ganglion- THE EYE. 
345 
cells and forms a sort of spongy network between these and 
the inner nuclear layer; its composition is still a matter of 
doubt, but it appears to be made up of a more or less homo- 
geneous substance, in which are numerous fine openings filled 
with some material of a peculiar refractive power. It does not 
belong to the nervous substance of the retina, and when placed 
in a 10 per cent, solution of common salt, dissolves, leaving the 
supporting connective-tissue fibres unaffected. 
The inner nuclear layer is made up of numerous oval cells 
with large nuclei; they belong mostly to the nervous tissue, 
but scattered among them are also cells of the supporting con- 
nective-tissue framework. 
The nerve-cells resemble small bipolar ganglion-cells, hav- 
ing two fine processes, the inner of which probably connects 
with the ganglion-cell layer, or directly with the optic nerve 
fibres. Near the macula these cells are more numerous ; to- 
ward the ora serrata they gradually decrease in number. 
Next comes the outer granular layer, a thin stratum re- 
sembling the inner in appearance and composition; here the 
fine fibres from the outer and inner nuclear layers become lost 
in a tangled mass. 
Between this layer and the membrana limitans externa is 
the outer layer of nuclei, made up of a number of oval cells, 
connected more or less closely with the inner ends of the rods 
and cones. 
The larger nerve-fibres, which pass through the outer gran- 
ular layer, are Joined to the nuclei of the cones, which lie di- 
rectly within the membrana limitans and are connected to a 
prolongation of the base of the cones themselves. The smaller 
fibres pass to the nuclei of the rods, which form an irregular 
layer at varying distances from the limiting membrane, and 
from which fine tangled fibres pass to the base of the rods. 
These nuclei resemble those of the inner layer; they con- 
tain a small amount of granular matter with a nucleus and nu- 
cleolus, and sometimes exhibit, as the result of post-mortem 
changes, peculiar transverse stripes. 
Directly beyond the membrana limitans externa, and rest- 
ing upon it, are the rods and cones, each composed of an outer 
and inner member. 
The rods are small, cylindrical bodies of high refractive 
power; when fresh they appear homogeneous, but with the 346 
MANUAL OF HISTOLOGY. 
beginning of decomposition, which occurs very quickly, the 
inner half appears as if filled with a finely granular substance, 
while the outer exhibits transverse striations, and finally 
breaks up into small disks, which can only be distinguished 
from those of the outer segment of the cones by their red color 
(visual purple of Kuhne), which soon fades on exposure to 
light. 
The inner segment of the cones is larger than that of the 
rods ; it tapers rapidly toward the outer part, where it is filled 
with a peculiar oval-shaped body ; the outer segment does not 
equal that of the rods in height, but divides into similar disks. 
The pigment-layer, in which the ends of the rods and cones 
are imbedded, consists of a single layer of hexagonal cells, 
more densely pigmented in the part next the retina, and by 
some observers said to be provided with fine processes, which 
are lodged between the rods and cones. This pigment is more 
dense at the macula and varies with the color of the person, 
being most abundant in negroes, whereas it is absent in albi- 
nos ; from this layer, according to Kuhne, the visual purple 
of the rods is reproduced. 
At the macula lutea, which is situated a little to the outer 
side of the entrance of the optic nerve, the ganglion-cell and 
inner nuclear layers have their greatest thickness. The fibres 
which pass from the outer granular to the outer nuclear layer 
are lengthened and run in a more horizontal direction toward 
the fovea, which forms a slight depression in the centre of the 
macula. 
Over this fovea the layers of nerve-fibres and ganglion-cells 
are absent, and the other laminse become so much thinned 
that the membrana limitans interna approaches nearly to the 
nuclear layer; the rods are also absent, and the cones be- 
come lengthened and slightly convergent. 
The membrana limitans interna lies between the retina and 
vitreous body ; it is a transparent homogeneous structure, and 
from its outer surface spring the connective-tissue fibres which 
form the supporting framework for the nervous part of the 
retina. 
These fibres arise in the form of thin fenestrated plates, 
connected together by numerous arms ; they soon contract, 
however, to smaller radiating bands, which surround the gan- 
glion-cells and pass on to the inner nuclear layer, where they THE EYE. 
347 
contain occasional nuclei. From this point they again ex- 
pand into broader sheets, which, after surrounding the outer 
nuclei, are united to form the membrana limitans externa. 
This membrane lies just at the base of the rods and cones, and 
it is provided with numerous holes, through which those struc- 
tures pass ; from its outer surface fibres extend up between 
the rods and cones to form supporting sheaths. 
The blood-vessels of the retina come from the arteria cen- 
tralis retinae, which usually divides into two or more branches 
at the entrance of the optic nerve ; these vessels lie in the layer 
of nerve-fibres, and, arching above and below the macula, give 
off numerous fine branches, from which capillaries penetrate 
as far as the inner nuclear layer. The larger retinal vessels are 
surrounded by lymph-spaces, which probably unite with those 
of the optic nerve. 
At the periphery the retina becomes much thinned, and at 
the ora serrata the nervous elements are discontinued, the con- 
nective tissue alone being prolonged over the ciliary body to 
its anterior angle, thus forming the pars ciliaris retince. 
This membrane consists of long cylindrical cells of varying 
shapes; they rest on the pigment and are covered by a thin 
stratum, which sends processes between them and seems to be 
a prolongation of the membrana limitans interna of the retina. 
It is very difficult to prepare good sections of the retina, 
but the following plan is recommended: enucleate with care 
the eye of a frog or some small animal, and immediately sus- 
pend it in a well-stoppered bottle containing a small bit of 
solid osmic acid : when sufficiently hard the posterior portion 
of the eye can be cut in pieces and sections made by imbed- 
ding or holding between pieces of liver. 
Another method is to place the eye unopened in Muller’s 
fluid for some two weeks, frequently changing the fluid; af- 
terward harden in alcohol. Sections may then be made in the 
same manner as before. 
To obtain the separate constituents, place a fresh retina in 
aTV per cent, aqueous solution of osmic acid for fourteen days, 
then in glycerine for seventeen days; after this, place a small 
piece on a slide in glycerine, with the cover-glass so arranged 
that no pressure is made upon the specimen ; now tap gently 
on the centre of the glass until the motion of the fluid causes 
the retina to fall apart. 348 
MANUAL OF HISTOLOGY, 
The optic nerve, after leaving the optic canal, passes through 
the orbit surrounded by three coverings, continuations of the 
cerebral membranes. 
The dural coat, composed of dense connective tissue with a 
few elastic fibres, forms the outer covering ; the fibres are at- 
tached to the periosteum, where the nerve leaves the bony canal, 
and where it enters the eyeball they are continued directly into 
the outer layers of the sclera. 
Within this covering, and separated from it by a very nar- 
row space, are the delicate fibres of the arachnoidal coat, 
and the lymph-space between the two is called the subdural 
space. 
Within the arachnoidal coat, and separated from it by a 
wide lymph-space, is the pial coat closely surrounding the 
nerye-fibres, and sending processes of connective-tissue be- 
tween their bundles. This membrane passes into the inner 
layers of the sclera, and also sends numerous fibres to the la- 
mina cribrosa. Its outer surface is covered with endothelium, 
and between it and the arachnoid coat is the subarachnoid 
space, which reaches to the inner layers of the sclera, and is 
continuous with the same space in the brain. 
The optic nerve itself, closely surrounded by its vagina 
fibrosa, passes forward through the orbit, receiving the central 
artery and vein at about 15 to 20 mm. from the sclera. These 
vessels pass to the centre of the nerve and lie in a connective- 
tissue sheath until they emerge on the inner surface of the eye- 
ball to branch over the retina. 
On cross-sections of the nerve, bundles of connective tissue 
are seen to pass inward from the pial sheath and form a cross- 
network, through the openings of which the nerve-fibres pass. 
On longitudinal sections the connective tissue appears in 
irregular fenestrated sheaths; this tissue can also be demon- 
strated by macerating thick sections in a | per cent, solution 
of chromic acid and then brushing out the nerve-elements. 
These nerve-filaments themselves are extremely small, but 
vary somewhat in size. They consist of an axis-cylinder sur- 
rounded by its medullary sheath; they are grouped in large 
bundles which pass through the meshes of the connective tis- 
sue. The fibres appear to be held together by a kind of homo- 
geneous albuminous substance—neuroglia, and have on their 
surface occasional nucleated corpuscles, distinguished from THE EYE, 
349 
those of the connective tissue by being larger and more irregu- 
lar in shape. 
Blood-vessels are found not only in the centre of the nerve, 
but also scattered through various parts of the connective tis- 
sues. 
At the lamina cribrosa there is an anastomosis with the ves- 
sels of the circle of Haller, which, coming from the short poste- 
rior ciliary arteries, forms a vascular circle in the sclera, about 
the entrance of the optic nerve. 
Where the nerve-libres pass through the sieve-like openings 
of the lamina cribrosa they lose their medullary sheath, and 
from that point pass on to the nerve-fibre layer of the retina 
as transparent axis-cylinders ; but in rare cases the sheaths are 
continued from the optic disk some little distance over the 
retina, and are seen with the ophthalmoscope as very white 
patches radiating out from the disk, or following the vessels 
and gradually fading into the general color of the fundus by 
a fine, fringe-like border. 
The vitreous body is a transparent, Jelly-like mass, of spher- 
ical shape, with a depression at the anterior part, in which the 
lens rests. It is bounded behind and on the side by the retina, 
in front by the lens with its attachments, and appears to have 
no true hyaloid limiting-membrane of its own. It is very diffi- 
cult to demonstrate any definite structure in this substance ; 
toward the periphery it appears to be arranged somewhat in 
concentric layers, but in the centre is more homogeneous. 
From the optic disk to the lens there is a small canal about 
1 mm. wide in front and spreading out behind; it is lined 
with very transparent cells, and filled with a substance more 
fluid than the rest of the vitreous ; it marks the position of the 
arteria Tiyaloidea, which is usually obliterated at about the 
seventh foetal month. 
The vitreous body also contains numerous corpuscles, espe- 
cially near the periphery ; these consist of round lymph-cells, 
stellate cells, with one or more nuclei, and irregular arms, and 
of branching cells which seem to have a transparent vesicle 
filling up a part of their interior. The vitreous contains no 
nerves, and after birth no blood-vessels; it may be examined 
fresh or hardened in a \ per cent, solution of chromic acid. 
Sections may be colored blue with aniline, and preserved in 
glycerine. 350 
MANUAL OF HISTOLOGY. 
The lens (Fig. 158) is a transparent, biconvex body, sur- 
rounded by a structureless, elastic capsule, which is thicker in 
front where it touches the iris, and thinner behind where it 
rests in the fossa patellaris of the vitreous. 
The inner surface of the anterior capsule is covered with a 
single layer of hexagonal epithelial cells, which become longer 
near the equator of the lens, and gradually pass over into the 
lens-fibre. 
After birth these fibres consist of long, transparent tubes, on 
section resembling flattened hexagons closely joined together 
by their serrated edges; they are 
arranged in concentric meridional 
layers with their broad side out- 
ward. They do not pass around 
the entire circumference of the lens, 
but arise on the anterior surface 
from three lines, which, uniting at 
the axis, make a figure like an in- 
verted Y, with the arms set at an 
angle of about 20° to each other; 
on the posterior surface this star 
is reversed, the Y standing upright. 
In adult life the rays are more 
numerous, and the fluid contents 
of the tubes become more solid and 
of greater refractive power, espe- 
cially toward the centre of the lens. 
Fig. 158. Meridional section through 
axis of the human lens. Babuchin. 
On a meridional section of the 
lens one sees the concentric ar- 
rangement of the lens-fibres, and near the equator a collection 
of nuclei (the nuclear zone). These nuclei belong to the lens- 
fibres, each one of which originally had one, although in 
adult life they are found more abundantly in the peripheral 
region. 
The fibres of the supporting ligament of the lens {the zonula 
cillaris) are attached to the anterior and posterior capsule near 
the equator ; from here they converge to the apex of the ciliary 
body, to which they are fastened. 
The fibres form for the most part an anterior and posterior 
layer, and have occasional nuclei, especially toward the ora 
serrata; between these layers is the canal of Petit, the result THE EYE. 
351 
of post-mortem changes, which quickly destroy the delicate 
fibres that ordinarily fill this space. 
Specimens for study may be made in the following way: 
harden an eye for fourteen days in Muller’s fluid ; then open, 
remove the lens, and preserve in alcohol. Sections may be 
made in any direction ; they should be colored with hema- 
toxylon and mounted in glycerine. 
To examine the epithelium under the anterior capsule, a 
piece of capsule should be peeled olf from a fresh lens and ex- 
amined with or without previous staining. Single lens-fibres 
or groups of fibres may be obtained by macerating a portion 
of lens in dilute sulphuric acid (i per cent.), or in a | per 
cent, solution of chromic acid, after which it can be easily 
separated into its elementary parts. 
The lachrymal gland is situated under the upper and outer 
edge of the orbital wall, resting partly in a shallow fossa of the 
frontal bone, to which it is attached by firm bands of connec- 
tive tissue. 
It is an acinous gland, divided into a larger upper portion 
{glandula Galeni), some 20 mm. long, 10 wide, and 5 thick, and 
a lower part of about half the size {glandula Monroi) ; they are 
supplied with blood by a branch of the ophthalmic artery, and 
with nerves from the fifth pair. 
The connective tissue which envelops the gland also ramifies 
through its substance, dividing it into numerous small alveoli, 
in which are the true secreting cells of the gland, and from 
which fine ducts pass out to coalesce, and finally discharge on 
the free surface of the conjunctiva fornicis at its upper and 
outer part. 
The upper part of the gland is quite dense, but in the lower 
portion the alveoli are less closely packed, and often near- 
ly surrounded by the orbital fat. The alveoli are covered 
by a fine membrane composed of flat cells with numerous 
branches or processes, which spread in various directions and 
serve to unite the cells of the investing membrane, and also the 
different alveoli ; they form a shell which is surrounded on its 
outer side by a distinct lymph-space, and on its inner surface 
is lined by the secreting cells of the gland., 
If these lymph-spaces have been injected with Berlin blue, 
and especially if the blood-vessels are injected with some other 
color, the arrangement of the lymph-spaces can be very well 352 
MANUAL OF HISTOLOGY. 
seen. The openings from the alveoli are at first lined with 
fine, flat cells ; then, as the tube grows larger, they assume the 
character of cylindrical epithelium. 
BIBLIOGRAPHY. 
Graepe tr. Saemisch. Handbuch der gesammten Augenheilkunde, Vol. I. 
Leipzig, 1874. 
J. Orth. Cursus der normalen Histologie. Berlin, 1878. 
A. Alt. Lectures on the Human Eye. New York, 1880. CHAPTER XXI. 
THE EAE. 
Bt DRS. WILLIAM P. WHITNEY and CLARENCE J. BLAKE, of Boston. 
Following the natural order are to be considered, first, the 
external ear with the meatus externus ; secondly, the middle 
ear with the Eustachian tube; and thirdly, the internal ear 
(membranous labyrinth and cochlea). 
External ear.—This includes the auricle, the meatus exter- 
nus, and the membrana tympani. 
The auricle is formed by a cartilaginous plate, 1-2 mm. in 
thickness. The fine elastic fibres of this plate, which is of the 
reticular variety of cartilage, can be traced into the perichon- 
drium, and even into the subcutaneous tissue. Both perichon- 
drium and subcutaneous tissue are rich in elastic fibres, the 
latter varying greatly in amount in different parts of the ear, 
being very sparingly developed on the concave surfaces, where 
the skin is closely adherent to the perichondrium, and immov- 
able in consequence, but more abundant on the convex sur- 
faces, where the skin is movable ; it forms, together with the 
fat enclosed in its meshes, the bulk of the lobule. 
The cutis covering the auricle is a direct continuation of 
that covering the face, and is well provided with downy hairs 
and sebaceous glands. These latter reach their greatest devel- 
opment in the depressions of the auricle, especially the concha. 
The external meatus consists of a cartilaginous and an os- 
seous portion. The former only differs in structure from the 
auricle into which it passes, in the presence of the ceruminous 
glands. These are tubular glands, having a coil at the bottom. 
They consist of a membrana propria, on which is a layer of 
cubical epithelium, and are the analogues of the sweat-glands. 
In the osseous portion of the meatus the glands are sparingly 
found, and the hairs are fewer and finer. Otherwise there is 354 
MANUAL OF HISTOLOGY. 
no difference between tlie two portions, except that the carti- 
lage is replaced by bone. 
The ear of a new-born child can be easily removed with the 
cartilaginous part of the meatus, and when hardened in Mul- 
ler’ s fluid and afterward in alcohol, and imbedded in paraffine 
or hardened liver, furnishes sections which, when colored with 
hsematoxylon, show the different relations very clearly. The 
osseous portion must first be decalcified by allowing the bone 
to hang freely in a weak (i per cent.) solution of chromic 
acid, often renewed, during several months. The specimens 
are then to be well washed, hardened in alcohol, and prepared 
as above. 
At the inner end of the external meatus, and separating it 
from the middle ear, is stretched the membrana tympani. The 
tympanic ring, with the membrane attached to it, is to be care- 
fully separated from the surrounding parts by means of bone- 
scissors, and placed for five to fifteen minutes in a weak solu- 
tion (two to five per cent.) of formic or acetic acid. It should 
then be well washed in distilled water, and the external layer 
of epithelium removed by a camel’s-hair brush, and finally 
stained with hsemotoxylon and mounted in glycerine. In spe- 
cimens thus prepared there are to be distinguished three lay- 
ers, viz.: an external or cuticular layer, a middle or fibrous 
layer (membrana propria), and an internal or mucous layer. 
The cuticular layer is composed of simple pavement-epithe- 
lium, without glands or hairs. It is thickest at the periphery, 
and over the handle of the hammer, and along its edge. 
The fibrous layer (membrana propria) consists of two sets 
of flattened, spindle-shaped fibres, with long, thin connective- 
tissue corpuscles imbedded in them, and which have a close 
analogy with the fibres of tendons. The outer series, lying 
directly beneath the cutis, radiates from the handle of the 
hammer toward the periphery, while the inner series circles 
about the handle. At the periphery the two series interlace 
with each other and with a few fibres coming from the cuticu- 
lar and mucous layers to form the so-called tendinous ring, in 
which are also to be found a few scattered cartilage-cells. This 
ring is joined to the annulus tympanicus by a thin periosteum. 
(The handle of the hammer is joined to the membrana tympani 
by a cartilaginous formation which stands in close relation to 
the membrana propria. This is a shallow groove of hyaline 355 
THE EAR. 
cartilage, in which the handle of the hammer lies, kept in place 
by the mucous layer which passes over and is firmly adherent 
to it; the upper part of this furrow ends in a sort of cartilagi- 
nous cap, into which the processus brevis fits.) Transverse 
sections made after hardening the membrane in Midler’s fluid 
and alcohol, and then imbedding, give the best idea of these 
relations. 
The inner or mucous layer is formed of flat epithelium, sup- 
ported on a reticulated layer of connective tissue, and directly 
continuous with the epithelial lining of the middle ear. The 
arterial supply is furnished by a small arteriole, which follows 
the handle of the malleolus, and gives off lateral capillaries 
anastomosing with others coming from small branches which 
enter at the periphery. The blood is collected into venous 
trunks which pass out in a similar manner. Fine nerves are 
said to be found in close connection with the vessels. They 
apparently come from the sympathetic system. 
The middle ear.—In order to obtain a clear idea of the rela- 
tions and structure of the middle ear a fresh temporal bone* 
with the soft parts still adherent, must be decalcified by soak- 
ing for a long time in a \ per cent, solution of chromic acid, 
which should be frequently changed; it is then to be washed 
in distilled water for twenty-four hours, and hardened in alco- 
hol, when it will be ready for cutting. 
A section from a specimen thus prepared shows that the 
whole middle ear is lined by a layer of pavement-epithelium, 
supported upon two layers of connective tissue, one serving as 
a submucous layer and the other as a periosteum. This tis- 
sue is thrown into ridges corresponding to the bony promi- 
nences, in the hollows of which the vessels and nerves lie. Ac- 
cording to Kessel the submucous layer is provided with oval 
expansions, recalling the Pacinian bodies found in the mesen- 
tery of the cat. The existence of muciparous glands in the 
human tympanum has yet to be confirmed. A plexus of nerves 
is described as distributed in the subepithelial tissue, in the 
nodal points of which are found scattered ganglion-cells. The 
lining of the tympanum passes directly into that of the mastoid 
cells, and has there the same general arrangement. 
The Eustachian tube.—In direct communication with the 
tympanum stands the Eustachian tube, composed like the ex- 
ternal ear of a cartilaginous and an osseous portion. The car- 356 
MANUAL OF HISTOLOGY. 
tilage, which gives tlie name to the anterior part of the tube 
that stands in connection with the pharynx, is in the form of 
a hook (Fig. 159, 2), with its short end directed downward and 
inward. At the bend of the hook the opposing surfaces of car- 
tilage cannot quite apply themselves to each other, and there 
is thus left a little air-space between them, which Ruedinger 
has termed the safety-tube (Fig. 159, 9), The cartilage is of the 
hyaline variety, with small cells, which are much smaller and 
more numerous at the periphery, thus forming a sort of peri- 
Eig. 159.—Transverse section of Eustachian tube and surrounding parts: 1, median cartilaginous plate; 
2, lateral cartilaginous hook; 3, musculus dilator tub® ; 4, musculus levator veli palatini; 5. flbro-carti- 
lago basilaris; 6 and 7, acinous glands; 8. deposit of fat in the lateral wall: 9, safety-tube ; 10, accessory 
fissure; 11, fold of the mucous membrane; 13, adjacent tissues. Ruedinger, 
chondrium. The cartilage is joined to the osseous portion by 
a narrow band of iibro-cartilage. 
The musculus dilator tubse (Fig. 159, 3), which goes to form 
the membranous (muscular) portion of the tube, is joined to 
the short end of the hook along the whole length of the carti- 
laginous portion. The muscle is of the striped variety, and is 
inserted into the perichondrium by means of a very short, flat 
tendon. 
The entire tube is lined with a mucous membrane (Fig. 159, 
11), continuous at one end with that of the pharynx, and at the THE EAR. 
357 
other with that of the tympanum. This membrane consists of 
several layers of cylindrical epithelial cells, the upper or inner 
of which have their broad surfaces directed inward and carry 
cilia. In the other la}mrs the epithelia are wedge-shaped. The 
epithelium rests upon a basement-membrane, beneath which is 
a layer of connective tissue (Fig. 159, 5), in which lie the muci- 
parous glands (Fig. 159, 6, 7), which are similar to those of 
the pharynx and oesophagus, and lined with wedge-shaped 
epithelium. These glands are absent in the safety-tube. A 
plexus of nerves arising from the pharyngeal and tympanic 
plexuses has been demonstrated, the final distribution of which 
to the glands is probable. 
Before leaving the middle ear a short mention of the os- 
sicula and their mode of articulation is in place. The bones 
are composed of an internal spongy and an external compact 
portion. The former is very rich in blood-vessels. These 
bones are covered in early life by the mucous membrane only, 
but in later life there is also a thin periosteum to be seen. 
Their articulation with each other is constructed similarly to 
that of the larger joints ; i.e., their articular ends are sur- 
rounded by a capsule in which is a synovial fluid. The method 
of union of the foot-plate of the stapes with the fenestra ovale 
is a little more complicated. The bottom and edges of the plate 
are covered with a thin film of hyaline cartilage. The edges of 
the window are also covered with cartilage, which is united to 
that of the plate by means of a fine network of elastic tissue. 
The base of the plate rests upon a firm connective-tissue layer, 
a continuation of the periosteum lining the inside of the scala 
tympani, and called the ligamentum baseos-stapedis. 
The muscles connected with the ossicula belong to the 
striped variety, and are connected to the bones by tendons, 
which are covered by the mucous membrane wherever they 
pass through the tympanum. 
The internal ear.—The internal ear consists of Wo portions, 
to which the auditory nerve is finally distributed, and which 
are the essential parts concerned in the perception of sound. 
These are the membranous labyrinth and the cochlea. 
In man and the higher vertebrates both of these parts are 
enclosed within bony walls, a circumstance which makes their 
histological study a matter of considerable difficulty. In fishes, 
however, although the cochlea is represented merely by a small 358 
MANUAL OF HISTOLOGY. 
diverticulum (the lagena), the membranous labyrinth is fully 
developed, and, as it is large and easy of access, has always 
been a favorite object for demonstration. Its method of prep- 
aration will be given here, while that for the cochlea will be 
described farther on. 
The membranous labyrinth.—Our knowledge of this part 
has been chiefly derived from studies upon the pike (esox In- 
dus), perch (perca fluviatilis), or cod (gadus morrhua). The 
head is divided longitudinally in the median line, and the brain 
carefully removed by means of the handle of a scalpel, when 
there is seen directly behind the eye a second cavity filled with 
a grayish translucent mass, composed principally of fat and a 
sort of mucous tissue. This can be removed with the aid of 
fine forceps, and there is usually drawn out at the same time 
more or less of the semicircular canals with their ampullae and 
the remains of the utricle and saccule. With a little practice, 
and by carefully freeing the canals from the short, bony chan- 
nels by which they are held in place, the membranous laby- 
rinth, with a portion of the acoustic nerve, can be removed 
entire. 
Within the utricle and saccule are found the otoliths, con- 
cretions of lime. After the lime has been removed by means 
of a weak acid, they show a coarse, fibrillated structure on 
section. These serve as a ready means of distinguishing be- 
tween the saccule and utricle, as the largest otolith (called 
sagitta) and the smallest (asterix) occupy the saccule, the 
former lying on the expansion of the acoustic nerve in the sac- 
cule proper, while the latter lies on the expansion of the nerve 
in that part of the saccule called the lagena, and which corre- 
sponds to the cochlea of the higher animals. The medium-sized 
stone (lapillus) lies upon the expansion of the nerve in the utri- 
cle. The otoliths are embedded in a mucilaginous mass lying 
directly upon the termination of the nerve. In the higher ani- 
mals they are represented by cretaceous particles in the macula 
acustica. 
The labyrinth thus removed is to be placed, during twenty- 
four hours, in a 1 per cent, solution of osmic acid, and then 
carefully washed in distilled water. In order to obtain the 
separate cells, the point where the nerve enters (known by its 
darker color) is to be carefully teased with fine needles and 
examined in glycerine. To obtain good sections, the por- THE EAR. 
359 
tions of the canal where the nerve terminates, and the simi- 
lar portion of the saccule and utricle, are to be placed for 
twenty-four hours in a saturated solution of gum arabic in 
water, and then directly into strong alcohol for twenty-four 
hours longer, when they will be ready for embedding. The 
sections, made with a sharp razor, kept well wet witli alcohol, 
are to be deprived of their gum by passing a stream of distilled 
water beneath the cover-glass, the water being replaced by a 
solution composed of one part of a saturated solution of ace- 
tate of potash and four parts each of glycerine and water. 
The structure and arrangement of the semicircular canals, 
except at the points of expansion of the nerve, is as follows : 
In the osseous fishes the canals lie embedded in a mass of adi- 
pose tissue, and are held in place by very short bony tubes ; 
in the cartilaginous fishes (shark, skate) they lie in canals hol- 
lowed out in the cartilage, while in man and the higher verte- 
brates they are surrounded by bony walls. 
In man the membranous part does not entirely fill up the 
bony canals, but is adherent to the lining periosteum at one 
point, and to the rest of the wall by bands of connective tissue 
(called Ugamentum labyrinthi canaliculorum et sacculorum), in 
the interstices of which the perilymph circulates. In the fishes 
the walls of the tubes and ampullae, as well as of the utricle 
and saccule, are composed of what has been termed spindle- 
cartilage. This consists of a homogeneous ground-substance, 
like that of ordinary cartilage, in which lie embedded long, 
spindle-shaped connective-tissue corpuscles, anastomosing with 
each other in all directions, like the corpuscles of the cornea. 
The whole is lined with a pavement-epithelium. In man the 
structure is different. Here there are to be distinguished three 
layers, viz., externally, a layer of connective tissue, composed 
of fibrous tissue with numerous nuclei. This is connected at 
one point with the periosteum, and passes into the ligamenta 
labyrinthi canaliculorum at the other points of the circumfer- 
ence ; secondly, of a hyaline layer, the tunica propria ; this is 
raised into papilliform projections in certain parts of the tube. 
The internal layer is composed of simple pavement-epithelium. 
The distribution and termination of the nerve is as follows [ 
in the fishes: The acoustic nerve divides into two branches, 
the cochlear and vestibular, each of which gives off three fila- 
ments. Those from the cochlear portion supply the saccule, 360 
MANUAL OF HISTOLOGY. 
lagena, and ampulla frontalis; those from the vestibular 
branch go to the utricle and the ampullae of the horizontal and 
sagittal semicircular canals. The termination of the nerves in 
the saccule and utricle is called macula acustica, and in the 
ampullae, crista acustica. 
The macula is a small, roundish spot, slightly projecting 
above the surface. Thin sections through it show the presence 
of three layers of bells. Directly upon the wall proper of the 
canal lies a single row of small, round epithelial cells with 
large nucleoli (Fig. 160, 1). ISText come several rows of cells hav- 
Pig. 160.—Section through the ampulla frontalis of esox lucius: 1, basal cells; 2, cells with thread- 
like prolongations: 3, cylindrical cells, with cilia. After Kuhn. 
ing a round or oblong (spindle-shaped) central portion, from 
which are given off two filiform prolongations, the one passing 
inward and standing in close connection with a fine plexus of 
nerves lying in the layer of round cells mentioned above; the 
other also passing inward, but ending either as a free cilium 
between the layer of cells next to be described, or being joined 
to their inner extremity (Fig. 160, 2, and Fig. 161). 
The inner layer consists of several rows of cylindrical epi- 
thelial cells, having the end, which is directed inward, tapering 
into a fine filament connected with those of the middle layer, as THE EAE 
already described. The free surface of these cells is provided 
with numerous hairs (Fig. 160, 3). 
tially the same as that of the ma- 
cula, with the exception that the 
crista rests upon an infolding of 
the wall called the septum nerveum 
(Fig. 160, sep. nerv.), and has on 
each side two half - moon - shaped 
prominences of cylindrical epithe- 
lium called the plana semilunata 
(Fig. 160, pi. sem.), into which no 
nerves have been traced. At the 
point where the macula and plana 
semilunata pass into the epithe- 
lium lining the rest of the canal, 
there is found an intermediate form 
of cell, larger than the ordinary 
epithelium, and separated one from 
another by a fine web of connective 
tissue. These have received the 
name of protoplasmic cells, but as 
yet their function has not been 
discovered. 
The arrangement of the cells in the crista acustica is essen 
Covering the crista in the place 
of an otolith is a gelatinous mass 
in the form of a cup, having a stri- 
ated appearance, and into which 
the fine hairs of the internal sur- 
face project. This is considered as 
a cuticular formation, and is sup- 
posed to act as a damper (Fig. 160, 
cupula). 
The nerve, after passing through 
the wall at the point opposite the 
crista or macula, loses all its 
sheaths, and forms a fine plexus in 
the outermost layer of cells, and 
Fig. 161.—Separate cells from the ma- 
cula, showing the connection of the cylin- 
drical cells with the cells having thread- 
like processes, and also the passage of these 
processes to the surface between the cells. 
Kuhn. 
this plexus has been found to communicate with the inner 
filaments of the middle layer of cells, the internal filaments of 
which ended as free cilia or were joined to cells of the inner 362 
MANUAL OF HISTOLOGY. 
layer which were provided with cilia upon their free surface. 
This can be best understood by a study of Figs. 160 and 161, 
In man the arrangement, as well as can be followed, is almost 
identical with that of fishes. 
The cochlea.—There is no easy method of obtaining good 
preparations of the cochlea, but that by which the best results 
have been obtained is as follows : The portion of the temporal 
bone containing the internal ear from a recently killed animal 
(young cat, dog, or bat) is hardened for twenty-four hours in 
i to 1 per cent, solution of osmic acid in distilled water, 
then placed in Muller’s fluid for a week, and decalcified by a 
0.01 per cent, solution of chloride of palladium. After decal - 
cification it is to be washed in distilled water for a few minutes, 
then soaked for twenty-four hours in a concentrated aqueous 
solution of pure gum arabic, and finally placed directly in 
strong alcohol for twenty-four hours. After this hardening the 
preparations are ready to be embedded in soap or hardened 
liver, and cut. The razor is to be kept well wet with alcohol 
while cutting. The sections are to be placed directly upon a 
slide, and the gum removed by passing a stream of distilled 
water under the covering-glass. 
Small portions of the lamina spiralis can also be taken from 
the fresh cochlea, after opening it carefully with the bone-for- 
ceps, and placed in the vapor of osmic acid or in a i to 1 per 
cent, solution of the same for a few (twelve to twenty-four) 
hours. The preparations thus treated may be teased in gly- 
cerine, and the separate cells obtained. 
The sections are to be made in a direction parallel with the 
long axis of the cochlea, and if the central shaft (modiolus) is 
cut through, the following picture will be presented : On each 
side of the modiolus are seen sections of the canal of the coch- 
lea, divided by a thin partition (the lamina spiralis, Fig, 162, 
L sp) into an upper portion (the scala vestibuli, Fig. 162, SF) 
and a lower (the scala tympani, Fig. 162, ST). The scala ves- 
tibuli is further subdivided by means of a delicate membrane, 
named after its discoverer the membrane of Reissner (Fig. 162, 
f, fi), which passes off at an angle from the middle of the 
lamina spiralis and is inserted into the wall of the cochlea.1 
The portion of the canal thus cut off forms the ductus cochle- 
aris (Fig. 162, e, et), and in it lies the peculiar body in which 
the nerve terminates, and which is called the organ of Corti. THE EAE. 
363 
The scala tympani is a blind canal, having at one extremity 
the membrane which covers the fenestra rotunda, and at the 
upper part terminating in the cupula of the cochlea, where it 
Pig. 162.—Section of the cochlea of a human embryo at the fourth month, a. a, a, cartilaginous 
incasement of the cochlea; 6. b, perichondrium; c, mucoid tissue matrix of the modiolus; d, d, cartila- 
ginous septa of the individual turns of the cochlea; e—e4, sections of the ductus coohlearis ;/, Reiss- 
ner’s membrane; g, membrana tectoria. somewhat lifted up from the subjacent parts ;h, rudiment of the 
stria vascularis; i, rudiment of the subsequent organ of Corti; L up, lamina spiralis; Gl, Gl,. ganglion 
spirale with various efferent and afferent bundles of nerves; ST, scala tympani; SF, scala vestibuli; 
STX, SVi,SSt,Tt, muccid tissue where later the seal® of the last cochleal turn will be. 3.1. Waldeyer. 
is said to enter into communication with the scala vestibuli 
by a minute opening, the helicotrema. 
The scala vestibuli stands in direct communication with the 
perilymphatic space of the vestibular sacs, while the ductus 
cochlearis is in communication with the saccule by means of 
a slender canal (the canalis reunions). The walls of the two 
scalae are formed of a thin periosteum, on the surface of which 364 
MANUAL OF HISTOLOGY. 
there can be shown, by means of the silver method, a layer of 
endothelium. This proves that the canals are of the nature of 
serous cavities. 
The lamina spiralis is composed of an osseous and a mem- 
branous portion. The osseous portion reaches about one-half 
the distance from the modiolus to the opposite wall, and on its 
outer and vestibular portion is a mass of connective tissue 
called crista spiralis (Fig. 163, Or.), the upper lip of which is 
called labium vestibulare (Fig. 163, I/O.), while the lower lip is 
called labium tympanicum (Fig. 163, Lt.)\ the space between the 
two lips has received the name of recessus internus. The crista 
spiralis is divided by a number of parallel furrows, which gives 
the surface a regular toothed appearance when seen from the 
vestibular surface. Hence, the portions between the furrows 
are called “ auditory teeth.” 
The under (vestibular) of the two lips is connected with 
the membrana basilaris (Fig. 163, Hn, Zp'\ which is com- 
posed of two layers of finely fibrillated connective tissue, 
and is covered on its tympanic surface by a layer of endothe- 
lium, and on the surface turned toward the ductus cochlearis 
by the organ of Corti and its supporting cells. The inner 
layer of this fine connective tissue is directly continued into 
the bases of the pillars of the organ of Corti next to be de- 
scribed. 
The organ of Corti, so named from its discoverer, is a com- 
plicated arrangement of cells in which the nerve terminates, 
and of other cells and their modifications, which apparently 
act as supports to these and as modifiers of the sound. The 
cells proper, in which the nerve terminates, have received the 
name of hair-cells, from the ciliated appendages which they 
carry (Fig. 163, a, a", a", a"), wdiile the peculiar modified cells 
which are their chief support are called the pillars. 
The pillars (Fig. 163, are two slender, slightly shaped 
bodies, of a finely fibrillated structure, showing, however, in 
their early stages, the presence of nuclei. They stand upon 
the membrana basilaris, and are apparently to be directly fol- 
lowed into the fine layer of connective tissue beneath them. 
They are arranged in two rows, named inner and outer, ac- 
cording to their situation as regards the modiolus. The pillars 
are inclined toward each other, and the space between them is 
named the tunnel. The head of the outer is a little enlarged THE EAE. 
and rounded, lying in a shallow depression in the head of the 
inner pillar, thus resembling a ball and socket-joint (Fig. 163, 
gia). The heads of the pillars, when seen from the surface, have 
Fig. 163.—Section through the ductus cochlearis of a young dog: R—r', Beissner’s membrane; Los 
and Los', vestibular and tympanic plates of the osseous lamina; gsp, ganglion spirale; n, fine nerves 
passing through the habenula perforata at Hn; Or, crista spiralis; in, its vestibula or upper lip; 
rm, Mt, in', the membrana tectoria (Corti’s membrane); Sxpi, recessus internus clothed with epithe- 
lium; ft and fa, inner and outer pillars of Corti, a and a", a", a", inner and outer hair-cells, between 
the latter are seen the flask-shaped cells, r, r, r ; Tn, nerve passing through the tunnel to reach one of 
the outer hair-cells ; Hz, Henson’s prop-cells ; Sp, Zp' zona pectinata ; gia, inner and outer heads of the 
pillars of Corti; Kp, plate called phalynx, which, when joined with its neighbors, forms the lamina reti- 
cularis, in which the ends of the hair-cells are supported; Lsp, liganaentum spirale; Sv, stria vascu- 
laris. After Lavdowsky. 366 
MANUAL OF HISTOLOGY. 
prolongations shaped a little like the bones of the fingers, and 
hence called phalanges (Fig. 163, Kp). These enclose spaces be- 
tween them, through which the ends of the hair-cells project. 
The network thus formed is called the lamina reticularis, and 
gives a very peculiar appearance when this portion of the organ 
is viewed from above. 
Corresponding to the pillars are rows of hair-cells termed 
inner and outer—a single row of the former (Fig. 168, a) and 
four rows of the latter (Fig, 168, a'\ ar\ a"). The shape of 
the cells of the inner row is cylindrical, having their base pro- 
longed into a fine thread expanding into a foot-stalk, which 
passes into the membrana basilaris. The top of the cell which 
passes through the opening in the lamina reticularis is pro- 
vided with fine cilia. The four rows of cells in connection with 
the outer pillar are of the same shape as those of the inner 
row, but, in addition, are joined at their lower part to peculiar 
cells shaped like a flask, large and rounded at the bottom, and 
tapering to a long and narrow neck. The tops of these cells 
reach to the lamina reticularis, but do not pass through it 
(Fig. 163, r, r, r, and b). Immediately adjoining the outer rows 
of hair-cells are several rows of cylindrical epithelial cells (Hen- 
son’s prop-cells) (Fig. 163, H.z), which pass gradually into the 
short cubical epithelium forming the zona pectinata (Fig. 163, 
Zp to Zp') adjoining the epithelial lining of the ductus cochle- 
aris. 
The course of the nerve has already been followed to the 
ganglion spirale. From this point a number of fine trunks 
pass through a canal in the osseous portion of the lamina spi- 
ralis to the lower lip of the crista, which they leave as naked 
axis-cylinders by a number of small holes, called the habenula 
perforata (Fig. 163, Hri). After entering the ductus cochle- 
aris they divide into two chief bundles, one distributed to the 
inner hair-cells, and the other, passing between the bases of 
the inner pillars, crosses the tunnel and then again passes be- 
tween the outer pillars, and terminates finally in the outer 
hair-cells. Beyond the fact that they apply themselves directly 
to the surface of the hair-cells, their mode of ultimate ending 
is not known. 
From the upper edge of the crista spiralis, lying directly 
upon it and covering the whole of the organ of Corti, is the 
membrana tectoria (Corti’s membrane) (Fig. 163, Mi), a homo* 367 
BIBLIOGRAPHY. 
geneous mass in which indistinct striations are to be seen. 
This is of the nature of a cutioular formation, and probably 
acts as a damper, preventing excessive vibrations of the organ 
of Corti. 
BIBLIOGRAPHY. 
Ruedinger. The Eustachian Tube, etc. Strieker’s Histology, New York. 1872. 
Trahtmann. Der gelbe Fleck am Ende des Hammergriffes. Arch. f. Ohrenheilk., 
Vol. XL, p. 99. 1876. 
Urbantschitsch. Zur Anat. d. Gehdrknochelchen des Menchen. Arch. f. Ohren- 
heilk., Vol. XL, p. 1. 1876. 
Politzek. Ueber Anastomosen d. Gefassbezirk d. Mittelohres u, d. Labyrinths. 
Arch. f. Ohrenh., Vol. XL, p. 237,1877, and Wien. med. Woch., No. 30. 1876. 
Weber-Liel. Die Membrana tympani secundaria. Monatsschr. f. Ohrenh eilkunde, 
No. 4. 1876. 
Laydowsky. Ueber d. akust. Endapparat d. Saugethiere. Arch. f. mikros. 
Anat., Vol. XIII., p. 417. 1877. 
Kuhn. Untersuch. hber den hautigen Labyrinth der Knochenfische. Arch. f. mikr. 
Anat., Vol. XIV., p. 264. 1877. 
Moldenhauer. Beitr. zur. Anat. u. Entwickel. d. Menschl. Gehororganes. 
Arch. f. Ohrenheilkunde, Vol. XL, p. 235. 1877. 
Doran. Morphology of the Mammalian Ossicula Auditus. Trans. Linn. Soc., 
London, Second series, Vol. I. 1877. 
Ueber-Lieli. Der Aqueductus cochleae beim Menschen. Monatsschr. f. Ohrenheilk., 
Vol. XIII., No. 3, p. 33, 1878-79, and Virch. Arch., Vol. LXXVII., p. 207, 
1879; also Arch. f. Anat. u. Phys., Phys. Abtheilung, p. 188. 1878. 
Cisope. Ueber d. Gehdrlabyrinth d. Knorpelfische. Sitz. d. Naturf, Gesellsch. an 
d. K. Universit. zu Kasan. May, 1879. (Russian.) 
Pritchard. The Organ of Corti in Mammals. The Lancet, 1876, p. 552, and 
Proc. Roy. Soc., Vol. XXIV., No. 168, p. 346, 1878 ; also The Termination of 
the Nerves in the Vestibule and Semicircular Canals of Mammals. Quart. 
Journ. Micros. Sc., New Series, No. 64, Vol. XXI., p. 398. 1879. 
Minot, C. S. Recent Investigations of the Histology of the Scala Media Cochleae. 
American Journal of Otology. April, 1881. PART 111. 
CHAPTER XXII. 
THE NASAL FOSS.E, PHARYNX, AND TONSILS. 
Br D. BRYSON DELAVAN, M.D., 
Member of the American Laryngological Association. 
The restibulum nasi is that part of the nasal canal which 
is surrounded by the anterior cartilages of the nose. It is cov- 
ered by a continuation of the exterior skin, which gradually 
assumes the characteristics of a mucous membrane and pos- 
sesses several layers of pavement-epithelium, the uppermost 
of which is composed of horny cells. This epithelium extends 
backward to the anterior margin of the inferior turbinated 
bone and the commencement of the inferior nasal duct, where 
it becomes ciliated. The integument has also vascular papillae, 
with both simple and compound loops, and in the lower part 
of the nose long, stiff hairs (vibrissae), as well as large sebaceous 
follicles. It is sparingly supplied with blood-vessels. The 
nerves are derived from the trigeminus, and consist of fila- 
ments, which probably end in terminal bulbs. 
The respiratory region.—The nasal fossae proper, with the 
exception of a limited part known as the olfactory region, may 
be regarded as a continuation of the respiratory tract. Each 
fossa communicates with four sinuses: the frontal, the sphe- 
noidal, the maxillary or antrum Highmorianum, and the pos- 
terior ethmoidal. The mucous membrane covering the respira- 
tory region and its accessory sinuses is called the Schneiderian 
or pituitary membrane. It is devoid of papillm, and is covered 
with a cylindrical ciliated epithelium, like that of the trachea, THE XASAL FOSSAE, PHARYXX, AND TOXSILS. 
the ciliary current being invariably toward the choanse (poste- 
rior nares). It contains, also, goblet-cells. Under the epithe- 
lium is a true membrana mucosa, which forms at the same 
time a periosteum for the bones, and is composed almost en- 
tirely of connective tissue, scantily permeated, if at all, with 
elastic tissue-elements. The mucous membrane may be divided 
into two varieties: a thinner membrane, covering the internal 
surface of the turbinated bones and the accessory sinuses, and 
the thicker membrane of the nasal fossae proper. 
The thinner membrane contains many acinous glands. In 
the adjacent cavities they are less abundant, excepting upon 
the internal wall of the maxillary sinus. Here, and in the 
sphenoidal sinus, the glands consist of several cylindrical 
tubes with connecting single oblong acini. The epithelium of 
the latter is pyriform, while in the tubes it is cylindrical. The 
mucous membrane itself is pale in color, and scantily supplied 
with blood-vessels. Special nerve-terminations have been de- 
scribed in Ihese sinuses. These are probably nothing more 
than terminations of fibres from the great sympathetic, having 
at their extremities ganglionic cellules. 
The thicker membrane covers the lower part of the nasal 
septum and the inferior and middle turbinated bones. It is 
lined with the same ciliated epithelium, and in the anterior 
two-thirds of the turbinated bones forms only a delicate, 
slightly corrugated covering for the subjacent parts. Poste- 
riorly, however, its surface is thrown into numerous thick 
folds, evidently designed to increase the extent of surface of 
the mucous membrane. 
The membrana mucosa forms a fibrous network, which 
passes between the glands and vessels and connects the mu- 
cous membrane with the periosteum. Its characteristics re- 
semble more nearly those of periosteum, so that it may properly 
be classed as a part of the latter. The glands of this region 
vary somewhat from the acinous type, and are composed of 
tortuous tubules, having many sinuses and oblong offshoots. 
They are lined on their inner surface with low cylindrical epi- 
thelium, and sometimes assume a circular, sometimes an oval 
or tubular shape in the microscopic section. The thickness of 
the pituitary mucous membrane is due not only to its mucous 
glands, but more particularly to the existence in it of true erec- 
tile tissue, as well as venous plexuses. (See p. 160). These are 370 
MANUAL OF HISTOLOGY. 
most abundant at the posterior extremity of the inferior tur- 
binated bones. Some of these vessels are prolonged throughout 
the continuity of the bone on the lateral as well as the median 
side, to appear with greater frequency at the anterior extrem- 
ity, without, however, regaining the number or size which they 
possessed at their origin. Where they are less numerous the 
remaining space is almost entirely occupied by large mucous 
glands. 
In the bony framework of the inferior turbinated bone, large, 
bright interspaces are seen in the fine trabecular substance, 
which are filled with fibrous tissue containing pale lymphoid 
cells. In this fibrous tissue are usually found transverse sec- 
tions of delicate vessels, the walls of which are apparently 
composed of fibrous tissue. In order to reach the outer sur- 
face these vessels either perforate the bone or lie in recesses 
separated from the soft parts only by the periosteum. In the 
middle three-fifths of the bone, where the osseous structure 
contains the largest cavities, we find in the vicinity of the ves- 
sels large, round, and polygonal, glistening cells, analogous to 
marrow-cells. A recent author believes most of the above- 
mentioned vessels to be lymphatics. The arteries of the infe- 
rior turbinated bone do not number more than three or four, 
and are derived from the posterior nasal artery. 
The olfactory region is situated in the uppermost portion 
of the nasal cavity. Its inferior limit in man has not yet been 
accurately determined. According to the generally received 
views of Schultze and Ecker, it is probably limited to the roof 
of the nasal fossae, the superior turbinated bone, and the cor- 
responding part of the septum. The mucous membrane of this 
region is of a dull, yellowish brown color, and is perceptibly 
thicker and softer than that of the respiratory region. This 
color proceeds from fine pigment-molecules, which are em- 
bedded partly in the bodies of the cylindrical epithelial cells, 
and partly in the cells of an especial gland-formation found 
here. Soon after death, however, it becomes unrecognizable. 
Under the microscope the olfactory region is seen to be bound- 
ed by a tolerably well-defined, serrated border, although isl- 
ands of ciliated epithelium, such as is found in the respira- 
tory are frequently found scattered about in different 
parts of it. The differences of structure in the olfactory mu- 
cous membrane depend upon the character of the epithelium, THE NASAL FOSS.E, PHARYNX, AND TONSILS. 
371 
the occurrence of peculiarly constructed glands—Bowman’s 
glands—and upon the relations of the nerves. 
The fundamental layer of the mucous membrane is com- 
posed of a finely fibrillated connective tissue, rich in cells, the 
arrangement of which is determined by the numerously dis- 
tributed glands, nerves, and vessels which it contains. As in 
the other regions of the nasal cavity, the mucosa seems to pass, 
without a well-defined limit, into the periosteum. In many 
places aggregations of small pigmented nuclei are found, some 
in the shape of long strips lying near the nerve-branches, some 
in other situations, in rounded or irregular groups. 
The olfactory epithelium attains a considerable thickness. 
It consists of a single layer of very elongated cells, which 
Schultze has proved to be of two kinds, epithelial cells and 
olfactory cells. 
The olfactory cells are slender, delicate structures, in which 
may be distinguished a cell-body and two prolongations going 
in opposite directions—the one to the periphery, the other cen- 
trally. The bodies of the olfactory cells are not all located in 
the same plane of the epithelial stratum. The majority, how- 
ever, occupy its deeper portions. The cell-body appears spin- 
dle-shaped or pyriform. It is finely granulated, and has in its 
central and widest portion a spherical, light-colored, ill-de- 
fined nucleus. The peripheral prolongation is generally rod- 
shaped, but now and then presents slight sinuosities. It is 
sharply outlined and homogeneous, and its free extremity, in 
some animals (amphibia and birds), has a tuft of the most deli- 
cate hairs, which project above the surface of the epithelium. 
In man this is not the case. The opposite prolongation is ex- 
tremely delicate and perishable, and, by some methods of 
preparation, resembles the finest nerve-fibrils, sometimes cov- 
ered with varicosities, at others entirely smooth. It runs con- 
tinuously and undivided as far as the base of the epithelial 
stratum, where it appears to meet the final radiations of the 
olfactory nerve, partly intertwines with these radiations, and 
then escapes further investigation. 
The indifferent epithelial cells appear in the form of an 
elongated cylinder with a very fine, granulated cell-body and 
an ellipsoid nucleus. Near the latter the cell suddenly con- 
tracts into a slender, very pale, centrally directed prolongation, 
the inferior end of which becomes somewhat wider, and 372 
MANUAL OF HISTOLOGY. 
brandies into a number of delicate filaments, by means of 
which the cell is attached to the fundamental layer of connec- 
tive tissue. These widened extremities of the cells often con- 
tain a brownish, partly nuclear, partly diffused pigment. 
Viewed upon the plane surface, the number of olfactory cells 
is apparently larger than that of the cylindrical cells. Each 
one of the latter, however, is generally surrounded by six of 
the olfactory cells, which completely fill the intermediary 
spaces between the cylindrical bodies. Both varieties of cells 
are so accurately adjusted to each other that, especially in the 
wider portion of the epithelial cells, fine longitudinal furrows 
may be seen, into which the peripheral continuations of the 
olfactory cells have been received. 
The surface of the epithelium is covered by a delicate mem- 
brane, discovered by Yon Brunn, and called by him the mem- 
brana limitans olfactoria. He has compared it to the membrana 
limitans externa of the retina, and describes its free surface as 
being plane and even, while its lower surface covers completely 
the rounded terminations of the epithelial cells. The periph- 
eral prolongations of the olfactory cells pass through this 
membrane, and terminate with bare extremities at the level of 
its free plane. 
The olfactory nerves.—The branches from the olfactory 
ganglia which emerge through the apertures of the lamina cri- 
brosa are composed entirely of non-medullated filaments, which 
resemble embryonic nerve-fibres. They next anastomose in the 
deeper layers of the mucous membrane, and form a dense 
plexiform meshwork, which sends fine branches toward the 
surface. In these branches the axis-cylinders are broken up 
into numerous, very fine, varicose fibrils, which ascend to the 
limit of the epithelial layer, where they are lost. Most au- 
thors agree with Schultze that there is a distinct connection 
between the nerve-fibrils and the olfactory cells. Exner be- 
lieves that the nerve-fibrils connect with the epithelial cells 
also. He argues, moreover, that intermediary forms, between 
the two varieties of epithelium, are found, which would prove 
that they are not different structures, but one and the same. 
Neither of these views has yet been established. 
Bowman* s glands, peculiar to the olfactory mucous mem- 
brane, are found in it in large numbers. They occupy almost 
the whole thickness of the mucous membrane, their bodies be- THE NASAL EOSSiE, PHARYNX, AND TONSILS. 
373 
ing located in the deeper layers of the connective tissue. In 
man their shape varies somewhat from that of simple tubules, 
as several glandular tubes ordinarily unite in a common excre- 
tory duct, so that, in some cases, the gland almost appeals 
racemose. The glandular cells are partly round, partly irreg- 
ular in shape, and have many pale nuclei, together with a 
brownish-colored pigment. 
THE PHARYNX. 
The mucous membrane of the pharynx is, in general, simi- 
lar to that of the mouth. It consists essentially of a stratified 
pavement-epithelium, a rather loosely woven submucosa, which 
contains aggregations of mucous glandules, and a tunica pro- 
pria composed of fibrillary connective tissue and furnished 
with papillae. The papillae are smaller than those found lower 
down in the oesophagus. The mucous glandules are most 
abundant in the superior part of the pharynx. The mucous 
membrane of the vault of the pharynx, and in the vicinity of 
the isthmus of the fauces, where it becomes continuous with the 
mucous membrane of the nasal cavity, to some extent assumes 
the characteristics of the latter. In this region the connective 
tissue is more or less thickly interspersed with lymphoid cells. 
It is provided, moreover, with ciliated cylindrical epithelium. 
In adults this epithelium extends some distance backward until 
it passes into the stratified pavement variety. In children, 
however, ciliated epithelium lines the whole naso-pharynx. 
In the upper and lateral parts of the pharynx are found cer- 
tain aggregations of adenoid tissue, most abundantly in the 
vault of the pharynx, extending from one Eustachian tube to 
the other. This tissue is generally quite diffuse, but is identi- 
cal in its structure with the lingual follicular glands and with 
the tonsils, and from this resemblance it has derived the name 
“pharyngeal tonsil.” 
THE TONSILS. 
The tonsil consists essentially of a reduplication, more or 
less extensive, of the oral mucous membrane, containing in its 
folds an abundance of the so-called adenoid tissue. MANUAL OF HISTOLOGY. 
Its gross structure varies in different animals. In some tlie 
organ is entirely absent. Its simplest form is found in the rab- 
bit, where it resembles a large lingual follicular gland. In man 
its usual shape is ovoid. Its average vertical diameter is 20 
fram., and its transverse diameter 13 mm. Its surface is per- 
forated by a varying number of slit-like and circular depres- 
sions, the common orifices of the system of cavities which it 
contains. If the tonsil of the rabbit be considered a single 
follicular gland, we have in man a multiplication of this to the 
number of from eight to eighteen, the interval between each 
gland forming a “lacuna tonsillaris,” crypt, or one of the sys- 
tem of cavities mentioned above. There are also in the interior 
of the tonsil single larger cavities, each of which includes sev- 
eral follicular folds and procures their common discharge at 
the periphery. The crypts generally are filled, more or less, 
with a yellowish substance composed of fat-molecules, detached 
pavement-epithelium, lymph-corpuscles, small molecular gran- 
ules, and cholesterin-crystals, which probably proceed from 
retained and decomposed epithelial matter, and perhaps now 
and then from the bursting of follicles whose cells have in- 
creased by proliferation and have undergone retrograde meta- 
morphosis and fatty degeneration. In its minute anatomy the 
tonsil is for the most part like other so-called adenoid glands. 
In common with the rest of the oral cavity, it is invested with 
a thick covering of pavement-epithelium, which rests upon a 
delicate endothelioid basement-membrane. Following this is a 
tolerably compact mucosa, formed of interlacing bands of 
fibrous connective tissue and containing many connective-tis- 
sue corpuscles. In the normal adult tonsil this structure is so 
delicate that sometimes it is hardly recognizable. From it 
bands of connective tissue extend centrally into the larger ton- 
sillary folds, and the whole forms essentially both an enclosure 
and a framework for the adenoid tissue or proper substance of 
the gland, as well as a nidus for its vessels. The minute struc- 
ture of the adenoid tissue of the tonsil does not differ from 
that of other follicular glands (those of the intestine, etc.), de- 
scribed elsewhere. Occasionally in the tonsil the adenoid tis- 
sue extends so near the periphery as to penetrate the mucosa 
and encroach upon the epithelial layers. This is especially 
the case in the walls of the crypts, where the epithelium com- 
monly exists in a modified form, or is altogether wanting. The BIBLIOGRAPHY. 
375 
tonsil is supplied abundantly with racemose mucous glands, 
which are most numerous in the neighborhood of the hilus. 
Here, also, may be found small bundles of muscular fibres 
apparently independent. 
BIBLIOGRAPHY. 
Kolliker. XJeber das Geruchsorgan von AmpMoxus. Muller’s Archiv fur Anat. 
und Physiol. 1843. 
Kohlrausch. J. Muller’s Archiv, pp. 8, 149. 1853. 
Ecker. In Berichte iiber die Yerhandlungen zur Beforderung der Naturwiss. 
No. 13. Fribourg, 1855. 
Schulze, Max. XJeber die Endigungsweise der Geruchsnerven und die Epithelial- 
gebilde der Nasenschleimhaut. Monatsberichte der konigl. Acad, der Wis- 
sensch. Berlin, 1856. 
Ecker. XJeber die Geruchsschleimhaut des Menschen. Zeitschrift f. wiss. Zoologie. 
VIII., p. 305. 1856. 
Ecker, A. Bericht iiber die Fortschritte, Anatomie und Physiologic f. d. Jahr 
1856, p. 117. Yon Henle und Meissner. 
Todd and Bowman. The Physiological Anatomy of Man. 11. London, 1856. 
Seeberg. Disquisitiones Microscopicas de textura membranse pituitariaa nasi. Diss. 
Inaug. Dorpati, 1856. 
Kolliker. Ausbreitung der Nerven in der Geruchsschleimhaut von Plagiostomen. 
Sitzber. der physik.-med. Gesellschaft, T. VIII., pp. 31. Wiirtzburg, 1857. 
Erichsen. De textura nervi olfactorii ejusque ramorum. Th. inaug. Dorpat, 
1857. 
Hover. De tunicas mucosas narium structura. Berolini, 1857. 
Eckhardt. XJeber Endigungsweise der Geruchsnerven. Beitrag zur Anatomie 
und Physiologic. 4. Abhand., p. 97. 1858. 
Gastaldi. Nuovi Ricerche sopra la terminazione del nervo olfactorio, in memorie 
de I’Acadi. reale della Scienza de Torino. XVII., p, 373, 1858. 
Funke, O. Lehrbuch der Physiologic. 3. Auflage. 1858. 
Kolliker. Handbuch der Gewebelehre. 8. Auflage, p. 680. 1859. 
Hover. XJeber die mikroskopischen Verhiiltnisse der Nasenschleimhaut. In Muller’s 
Archiv f. Anat. und Physiolog., 1861, p. 387; 1860, p. 6. 
Clarke, Lockhart. XJeber den Ban des Bulbus olfactorius und der Geruchs- 
schleimhaut. Zeitsch. f. wissens. Zoologie. XI. 1863. 
Walter, G. XJeber den feineren Bau des Bulbus olfactorius. Virchow’s Arch., T. 
XXII, p. 361. 1863. 
Henle. Handbuch der systematischen Anatomie des Menschen. Bd. 11. Braun- 
schweig, 1866. 
Zernoff. XJeber das Geruchsorgan der Cephalopodon. Bull, de la Soc. imp. des 
sc. nat. de Moscow. 3e serie. XLII. 1869. 
Exner. Weitere Studien iiber die Structur der Riechschleimhaut bei Wirbelthie- 
ren. Sitzungsberichte der k. Akad. der Wissenschaften. Wien. Band LXV. 
3. Abth. 1873. Et Bd. LIU. 1867-1869. 376 
MANUAL OF HISTOLOGY. 
Heidenhain, A. Ueber die acinosen Driisen der Schleimhaute, ins besondere der 
Nasenschleimhaut. Diss. Inaug. Breslau, 1870. 
Schulze, Max. Untersuchungen über den Ban der Nasenscbleimhaut. In Abhand- 
lung. d. naturforsch. Gesellschaft. VII. Halle, 1873. 
Babuchin. Das Gerucbsorgan. In Strieker’s Handbuch. 1873. 
Martin. Studies from the Physiol. Lab. in the University of Cambridge. I. 1873. 
Cisopf. Zur Kenntniss der Regio Olfactoria. Centralblatt. 1874. 
Bigelow, H. J. On the Anat. of the Turbinated Corpora Cavernosa. Boston, Med. 
and Surg. Journal. April, 85, 1875. 
Shopield, R. N. A. Taste-Goblets in the Epiglottis of the Dog and Cat. Journal 
of Anat. and Physiol. X., p. 475. 1876. 
Honigsciimied. Ztschr. f. wiss. Zool. XXIX., S. 355. 1877. 
Dayis, C. Die becherformigen Organe des Kehlkopfes. Arch. f. mikroskop. Anat., 
XIV., S. 158. 1877. 
Podwisotzky. Anatomische Untersuchungen iiber die Zungendriisen des Menschen 
und der Saugethiere. Inaugural Dissertation. Dorpat, 1878. 
Lowe. Beitrage zur Anatomie der Nase und Mundhohle. S. 80. Berlin, 1878. 
Zuckerkandl. Ueber die norm, med.-path. Anat. der Nasen- und angrenzenden 
Hohlen. All. Wien. med. Ztg., No. 51. 1879. 
STEINBRUGGE, H. The Histology of the Inferior Turbinated Bones and of the Tele- 
angiectatic Fibromata Arisiug from These. Archives of Otology, New York, 
Oct., 1879. CHAPTER XXIII. 
THE MOUTH AND TONGUE. 
D. BRYSON DEL AVAN, M.D., 
Member of the American Laryngological Association. 
With the exception of a few remarkable modifications, the 
structure of the mucous membrane of the buccal cavity is the 
same throughout. 
The tunica propria consists of fibrillated connective tissue, 
made up of tolerably minute bundles of intertwining filaments. 
Between these appear many delicate, elastic fibres. Toward 
the epithelium this structure becomes less distinct, and an ex- 
ceedingly delicate, filamentous network is developed. The con- 
nective-tissue cells with their nuclei, on the other hand, become 
more marked. The surface of the tunica propria contains 
many slender papillae, which penetrate more or less deeply 
into the epithelial covering. They have, also, the above-men- 
tioned filamentous structure, but contain few cellular elements. 
The transition of the tunica propria into submucous connec- 
tive tissue is, in general, hardly perceptible. The latter, how- 
ever, contains fewer elastic filaments and broader bundles of 
connective tissue. The epithelium lining the buccal cavity is, 
throughout, stratified pavement. The mucous membrane of 
the mouth varies in different regions as to the thickness of its 
different strata, the height of its papillae, and the condition of 
the submucous tissue. It is thickest and firmest in the gums 
and near the palate—particularly in the posterior section of the 
hard palate—and thinnest in its reduplications, e.g., the froe- 
num linguae, glosso-epiglottic fold, and the pillars of the fau- 
ces. Its firmness in the above places is due to the density of 
the submucosa, which forms, with the underlying periosteum, 
one compact mass of connective tissue. 378 
MANUAL OF HISTOLOGY. 
Elsewhere the mucosa is looser, so that the mucous mem- 
brane is readily thrown into folds. It is thickest wherever it 
has intervening layers of glands. In some places, especially 
in the lips and soft palate, the submucosa is crossed by bun- 
dles of striped muscular fibres, which are connected partly 
with the submucosa, and partly with the tunica propria. The 
papillce of the mucous membrane are most developed at the 
margin of the lip and its immediate vicinity, as well as on the 
gums, attaining here a height of 0.5 mm., and often termina- 
ting in a double point. In the reduplications of the mucous 
membrane (the fraenum linguae, etc.), and partly in the region 
of the hard palate, the papillae are very small, sometimes rudi- 
mentary. The thickness of the epithelial layer is proportion- 
ate to the height of the papillae. Beginning at the vermilion 
border of the lips, and going backward, the epithelial cov- 
ering becomes progressively thicker, and is thickest at the 
posterior margin of the lip, decreasing rapidly on the pos- 
terior surface. Upon the cheeks and on the anterior surface 
of the hard palate the epithelium is of medium thickness ; 
it is thinnest on the floor of the mouth and on the above- 
mentioned reduplications. There are, however, deviations in 
these proportions, especially in the hard palate, where the 
papillae are in some cases absent. Moreover, the tunica pro- 
pria sometimes assumes an almost tendinous character. Cer- 
tain important aggregations of glands, the so-called mucous 
glandules, are found lodged in the submucous connective tis- 
sue of the mouth. These are the labial, bucchl, palatal, and 
molar glandules. They are found as white, sharply defined 
knobs, visible to the naked eye upon the posterior surface of 
the lips, as well as upon the cheeks, palate, and bottom of the 
buccal cavity. In some cases they are aggregated into a few 
large clusters, while in others they are more scattered and 
smaller. The orifices of their ducts are best seen in the lining 
membrane by everting the lips or cheek. They belong to the 
acinous type, and have a short duct, generally somewhat 
curved, relatively wide, but somewhat contracted at the ori- 
fice. The greatest width of the tubes is at their place of seg- 
mentation. On the branches themselves are smaller ramifica- 
tions, which either terminate directly with globular or ellipsoid 
alveoli, or previously divide into one or more twigs. It often 
happens that a small group of acini, with a narrow common 379 
THE MOUTH AND TONGUE. 
duct, situated near a larger duct, discharge into the latter near 
the surface of the mucous membrane, appearing like a small 
accessory glandule. The walls of the glandules consist of a 
structureless basement-membrane, upon the interior surface of 
which are superimposed cylindrical, clear, almost homogene- 
ous-looking cells, with oblong nuclei. 
As for the connection of the buccal mucous membrane with 
the underlying structures, different conditions obtain in differ- 
ent regions. Its connection with the hard palate and gums 
has been described above. Where it is superimposed upon a 
sharply defined muscle, e.g., over the floor of the mouth, and 
over the sublingual gland, it passes into the connective-tissue 
sheath of the part. 
The blood-vessels of the mucous membrane are arranged in 
two systems of superficially extended networks. The deeper 
one, located in the submucosa, is composed of the mutually 
anastomosing branches of the afferent and efferent vessels. 
From this network many smaller vessels penetrate into the 
tunica propria, which, by division into still smaller branches, 
and by frequent anastomoses with one another, form the more 
superficial and finer-meshed vascular net. In both nets the 
venous and arterial branches run tolerably parallel. From the 
sujDerficial network very fine branches enter the papillae, where, 
according to their size, they form either capillary nets or sim- 
ple loops. 
The lymphatics form wide networks in the submucosa, 
and narrow nets in the tunica propria. Single small vessels 
cross those of the vascular nets. That lymphatics pene- 
trate the papillae is doubtful. The nerves of the buccal mu- 
cous membrane form in the submucosa more or less dense 
plexuses, in which many separations of the single nerve-fibrils 
may be noticed. Thence numerous filaments, partly isolated, 
partly arranged in small bundles, and always medullated, 
ramify, and radiate in wider ramifications toward the super- 
ficial layers of the mucous membrane. A certain number 
of nerve-fibrils approach the papillae, to implant themselves 
either at their bases or at the centre of their apices, some- 
times even at their extremities, in the terminal bulbs of 
Krause. Such fibrils are most abundant in the lips and in the 
anterior surface of the velum palati, and in smaller quantity in 
the cheek and bottom of the mouth. Nerve-fibrils may some- 380 
MANUAL OF HISTOLOGY. 
times be seen also with double contours, which wind, during 
their course, into a coil in the superficial layers of the mucous 
membrane. 
THE TONGUE. 
Although the mucous membrane of the tongue is, in the 
general details of its construction, similar to that of the rest of 
the buccal cavity, it nevertheless presents some striking pecu- 
liarities, mainly due to the configuration of its upper surface. 
This is covered by many closely aggregated prominences of 
the mucous membrane—the lingual papilla—which give it a 
roughened, fungoid appearance. Upon the under surface of 
the tongue the papillae are absent, but the mucous membrane 
here contains a large number of follicular glands. The lateral 
edges of the tongue are here and there covered with lingual pa- 
pillae, which are often arranged in rows, and toward the base 
of the tongue are replaced by the so-called fimbria lingua. 
Besides simple papillae, analogous to those of the skin, the lin- 
gual mucosa is studded with three distinct varieties of com- 
pound papillae—the filiform, the fungiform, and the circum- 
vallate. These are distinguished from the ordinary papillae of 
the mucous membrane, not only by their large size and their 
peculiar shapes, but also by their complicated structure, by the 
arrangement of their secondary papillae, and the conditions of 
their epithelial coverings. Between these three forms are 
several intermediary ones. The filiform papilla are found all 
over the dorsum of the tongue, anterior to the line of the cir- 
cumvallate papillae. Not only in different individuals, but 
also in the same tongue, there are marked variations in their 
form. At the tip and lateral edges of the tongue they are 
always smaller, and their filaments are wanting or merely ru- 
dimentary. Toward the centre of the tongue they gradually 
become larger and more abundant, and attain their highest 
development in the angle made by the circumvallate papillae. 
Their shape is that of a truncated cone, which has at its 
free extremity a central hollow or depression, around which is 
arranged, in a circular manner, a collection of thread-like pro- 
jections, or secondary papilla). Like the rest of the mucous 
membrane of the tongue, they are covered with stratified pave- 
ment-epithelium. In the secondary papillae of the larger fill- THE MOUTH AJSTD TOXGUE. 
form papillae tlie epithelium is of the horny variety, and its 
arrangement is imbricated, the lower margin of each scale over- 
lapping the upper border of the scale next below it. In the 
axes of the filiform papillae large-sized arterial and venous 
capillaries extend. Each secondary papilla contains a vascu- 
lar loop. The papillae of smallest size contain a fine network 
of vessels, and in the posterior part of the tongue simple capil- 
lary loops. Neither the filiform papillae nor their secondary 
papillae contain nerve-fibrils. The latter are found, however, 
at the base of the papillae, where they end in rounded terminal 
bulbs. 
The fungiform papilla, are larger than the filiform, and 
their epithelial covering is much thinner. They appear as 
rounded prominences, somewhat constricted at the base, and 
covered upon the sides and top with many cone-shaped second- 
ary papillae. The free surface of some fungiform papillae is 
smooth, the secondary papillae being farther apart. These are 
found most commonly at the lateral edges of the tongue, and 
are the so-called lenticular papillae. The distribution of the 
fungiform papillae is rather irregular, and it varies in different 
individuals. At the base of the tongue, and generally at its 
lateral portions, between the filiform papillae, they are some- 
times scarce and sometimes quite abundant. Toward the tip 
of the tongue they are smaller, while they are larger in the 
region of the circumvallate papillae. They are covered with 
several layers of pavement-epithelium, the deeper strata of 
which are formed by smaller polygonal prickle-cells. In this 
epithelial covering, upon the surface of the fungiform papillae, 
are constantly found peculiar bodies, called the “taste-goblets.” 
The taste-goblets vary in size and shape in different ani- 
mals, and also in the same animal, according to the locality 
in which they are found. They usually resemble a short- 
necked flask, their longest diameter being the longitudinal. 
The lower part of the taste-goblet rests upon the submucosa ; 
the body, and more especially the part which corresponds to 
the neck of the flask, is surrounded by epithelial cells. Every 
taste-goblet has at the surface of the epithelium an opening 
called a p>orus, which word is frequently used not only to des- 
ignate the exterior opening, but also for the entire short canal 
in the epithelial layer. The diameter of the porus is from 
.0064 to .0198 mm. It is surrounded by two and sometimes by 382 
MANUAL OF HISTOLOGY. 
three similarly formed cells. Sometimes the porns is formed 
by a single perforated cell. The short canal in the epithelial 
cells is surrounded in like manner. In each taste-goblet two 
varieties of cells may be distinguished—the exterior or super- 
ficial cells, called roof- or supporting-cells, and the interior, or 
central cells, called taste- or rod-cells. The roof-cells, which 
may be considered as modified epithelial cells, surround the 
taste-goblets as petals envelop a bud. Their arrangement with 
relation to one another is imbricated. The cells themselves 
are long, narrow, spindle-shaped, and curved, and each one 
has a well-marked nucleus. The peripheral end of the cell is 
pointed, while the central extremity is sometimes ramified. 
The taste- or rod-cells are long, slender, and highly refractive. 
A nucleus of unusual size almost entirely fills their bodies, while 
their extremities pass into two distinct prolongations—the pe- 
ripheral or superior, and the central or inferior. The peripheral 
prolongation is moderately broad, and has a short, delicate 
extremity, which resembles a small rod or hair. Hence the 
name rod-cell. These rods are located inside the short canal, 
and rarely project above the porus. The inferior prolongation 
is divided into several rootlets. The connection of nerve-fila- 
ments with the taste-goblets has never yet been conclusively 
demonstrated, although all authorities agree as to the proba- 
bility of such connection. Many aggregations of ganglionic 
cells, of greater or less size, are found in the course of the 
nerve-bundles, near the circumvallate as well as near the fili- 
form papillae. In the fungiform papillae the nerves enter the 
axis of the papillae as small trunks, composed of fibres with 
double contours. These divide into single nerve-filaments, 
some of which terminate in bulbs, which are located in the lat- 
eral surfaces of the fungiform papillae, under the secondary 
papillae. The fibrils which run into the axis pass into pale ter- 
minal filaments, and disappear in a brush-like extremity in a 
granular mass composed of neurilemma—its nuclei, and nu- 
merous circular granules—the gustatory granules. These last 
consist of a globular nucleus, surrounded by a very small 
amount of cell-protoplasm. The resemblance of the above to 
the interior roof-cells of the acoustic terminal apparatus, and 
to the rods and cones of the retina, is striking. 
The conical or secondary papillae are of the same general 
construction as the fungiform throughout; but they present THE MOUTH AND TONGUE. 
383 
the following differences of appearance: their epithelial cover- 
ing is thicker, and stratified somewhat after the manner of the 
filiform papillae, the taste-goblets are absent upon their sur- 
face, and the nerve-fibres, so far as they can be traced, termi- 
nate in bulbs. 
The circumvallatepapilla, about nine in number, are situ- 
ated at the back part of the tongue. They form an irregular 
row on each side and incline slightly from before backward 
toward the median line. At their point of junction is the fora- 
men ccecum of Morgagni. Each circumvallate papilla consists 
of a broad, flat elevation of the mucous membrane, which is 
surrounded with a fossa. Its surface is covered with small 
secondary papillae, and the epithelium is like that of the 
fungiform papillae. Taste-goblets are found abundantly upon 
the lateral edges and toward the centre of the papillae. The 
blood-vessels are arranged as in the fungiform papillae, and 
each secondary papilla contains a vascular loop. The nerves 
are derived from the glosso-pharyngeal. They consist of single 
pale nerve-fibres, which form a network in the centre of the 
papillae and ascend toward its peripheral surface. 
The papilla foliates, or fimbriae linguae, consist of several 
folds of the mucous membrane at the lateral edges of the 
tongue. Between them are scattered a few fungiform papil- 
lae, and they contain a considerable number of taste-goblets. 
Many excretory ducts of acinous glands empty at the bases of 
these folds. 
The sublingual mucous membrane includes that of the floor 
of the mouth. Both are of the same structure, and pass into 
each other by means of a reduplication, the frsenum linguae. 
The secreting glands of the root of the tongue are of two 
varieties—serous and mucous. The mucous glands are like 
those elswhere in the buccal cavity. Their ducts are some- 
times lined with ciliated epithelium. The glands themselves 
are not found in the neighborhood of the taste-goblets. The 
serous glands, on the other hand, are found most abundantly 
in those parts of the tongue which are most richly supplied 
with taste-goblets. Their ducts open into the grooves which 
are lined by the taste-goblets. 
The follicular glands, which form the collections of adenoid 
tissue found at the base and at the sides of the tongue, are not 
true glands, but rather elevations of the mucous membrane 384 
MANUAL OF HISTOLOGY. 
caused by circumscribed collections of adenoid tissue found in 
the tunica propria. They resemble glands, in that they gener- 
ally possess a cavity of variable size which terminates at the 
surface of the follicle. The mass of adenoid tissue which com- 
poses the follicle is surrounded by fibres of connective tissue, 
which are sometimes so compactly woven as to form almost a 
capsule around it. Sometimes this capsule is wanting, but a 
gradual transition of the two neighboring forms of tissue is 
never seen. Above, the adenoid tissue extends as far as the 
epithelium, so that the papillae of the mucous membrane either 
disappear altogether or are only to be found occasionally, and 
then of small size. This adenoid tissue is in all its essentials 
similar to that found in the tonsils, the vault of the pharynx, 
and at scattered points in the adjacent tissues. 
The so-called mucous corpuscles of the saliva are probably 
lymph corpuscles which have escaped from the adenoid tissue 
just mentioned. 
BIBLIOGRAPHY. 
Albinus. Academicarum Annotationum. Lib. I. S. 58. (Quoted by J. Honig- 
schmied.) Leidoe, 1754. 
Bopp. Die Verrichtungen des fiinften Nervenpaares. Leipsig, 1882. 
Blsasser, in F. Majendie Lehrbucb der Physiologic, aus dem Franzosischen iiber- 
sefczt mit Anmerkungen und Zusiitzen von D. C. L. Elsasser. 3 Aufl. I. Tu- 
bingen, 1834. 
Mayer, J. F. 0. Neue Untersucbungen aus dem Gebiete der Anatomie und Pby- 
siologie. S. 25 und 26. Bonn, 1842. 
Bruhl. Ueber das Mayer’scbe Organ an der Zunge der Haus-Saugethiere oder die 
seitliche Zungenrucken-Driise derselben. Yierteljahrscbrift far wiss. Veter- 
inarkunde. I. S. 165. Wien, 1851. Kleine Beitrage zur Anatomie der Haus- 
Siiugetbiere. Wien, 1850. 
Kolltker, A. Microscopische Anatomie. 11. Specielle Gewebelebre. 2. Halfte. 
1. Abth. Leipzig, 1852. 
Schwalbe. Das Epitbel der Papillae vallatae. Vorlauflge Mittbeilung. Arch. f. 
microscop. Anat. 111. S. 504. 1867. Derselbe Ueber die Geschmacks- 
organe d. Saugethiere und des Menschen. Arch, f. microscop. Anat. IV. S. 
154. 1867. Und M. Schultze, Erklarung der Entdeckung der Schmeck- 
becher von G. Schwalbe betreffend. Arch. f. mikroskop. Anat. YIII. S. 660. 
1872. 
Loyen. Beitrage zur Kentniss vom Bau der Geschmackswarzchen der Zunge. Arch, 
f. mikroskop. Anat. IV. S. 96. 1867. 
Schwalbe. Zur Kentniss der Papillae fungiformea d. Saugethiere. Centralblatt 
f. d. med. Wiss. Nr. 28. S. 438. 1868. BIBLIOGRAPHY. 
385 
Von Wyss. Ueber ein neues Geschmacksorgan auf der Zunge des Kaninchens. 
Centralblatt f. d. med. Wiss. Nr. 35. S. 548. 1869. Derselbe, Die becher- 
formigen Organe der Zunge. M. Scbultze. Arcb. fur mikroskop. Anat. VI. 
S. 238. 
Krause. Die Nervenendigung in der Zunge des Menschen. Gottinger Nacbrichten. 
S. 423. 1870. 
Verson. Beitrage zur Kentniss des Keblkopfes und der Trachea. Sitzgsbr. der 
wiener Acad. 1 Abth. LVII. S. 1093. 1868. Derselbe, Kehlkopf und 
Trachea in Strickers Handbuch der Lehre von den Geweben. I. S. 456. 
Leipzig, 1871. 
lIoNIGSCiiMJED, J. Beitrage zur mikroskop. Anatomie der Geschmacksorgane. 
Ztschr. f. wissensch. Zool. XXIII. S. 414. 
Exner. Med. chirurg. Rundschau, Juni Heft. S. 400. Wien, 1872. 
Ditlevsen. Endersogelse over Smagldgene paatungun hos patte dyrene og men- 
nesket. Kopenhagen, 1872. Referat in Hoffmann und Schwalbe Jahresb. I. 
Lib. S. 211. 1872. 
Honigschmieu. Ein Beitrag lib. die Verbreitung der becherformigen Organe auf 
der Zunge der Saugethiere. Centralbl. f. d. med. Wiss. No. 26. S. 401. 
1872. 
Henle. Handbuch der system. Anatomie des Menschen. 11. 2. Aufl. S. 878. 
1873. 
Von Ebner, Ritter. Die acinosen Driisen der Zunge und ihre Beziehungen zu den 
Geschmacksorganen. Gratz, 1873. 
Sertoli, E. Osservazioni suite terminazioni dei nervi del gusto. Gazetta Medico- 
Veterinaria. IV. 2. Separatabdruck. Deutsch in Molesch. Enters. XI. 
4. Heft. S. 403. 1874. 
Hoffmann, A. Ueber die Verbreitung der Geschmacksorgane beim Menschen. 
Arch. f. pathol. Anat. LXII. S. 516. 1875. 
Watson, W. Spencer. Diseases of the Nose and its Accessory Cavities. London, 
1875. 
Von Brunn. Entersuchungen liber das Riechepithelium. Arch. f. mik. Anat. 
No. 11. 1875. 
Krause, W. Allgemeine und mikroskop. Anat. Hannover, 1876. 
Voltolini. Address delivered December 15, 1876, before the Silesian Association 
for National Culture. 
Krause. Lehrbuch. Hannover, 1876. 
Kolliker. Ueber die Jacobson’schen Organe des Menschen. Festschrift zu Rineckers 
Jubilaum. Leipzig, 1877. 
Ponchet et Tourneux. Precis d’histologie humaine. 1878. 
Luschka. Das Epithelium der Riechschleimhaut des Menschen. Centralbl. f. die 
med Wissenschaft. Nr. 22. 1877. 
Wundt. Lehrbuch der Physiologic des Menschen. Stuttgart, 1878. CHAPTEE XXIV. 
THE ALIMENTARY CANAL. 
Curator of the St. Luke’s and St. Francis’ Hospitals, etc., New York City. 
Bt EDMUND C. WENDT, M.D., 
The human alimentary canal is a tube of great length, ex- 
tending from the mouth to the anus. There are considerable 
variations of its calibre in the different regions of the body 
through which it passes. The two external openings of the 
digestive tract are continuous with the cutaneous surface of 
the body. Throughout its entire extent we find several super- 
imposed layers or membranes, which are from within outward : 
1, a mucous membrane with its submucosa ; 2, the muscular 
coat; and 3, a fibrous layer. In addition to these fundamental 
strata, we encounter certain special structures, which charac- 
terize the various parts of the canal. The buccal cavity and 
pharynx are elsewhere described ; we begin, therefore, with a 
consideration of 
THE (ESOPHAGUS. 
The walls of this section of the tract are directly continuous 
with those of the pharynx, and have an average thickness of 
from three to four millimetres. In the (Esophagus, in addition 
to the four pharyngeal coats, a new layer appears between the 
epithelial stratum and the submucous tissue. This new struc- 
ture has received the name of muscularis mucosae. Hence, the 
different layers of the oesophagus are from within outward : 
1. The mucous membrane. 
2. The muscularis mucosae 
8, A submucous layer. 
4. The muscular coat. 
5. A fibrous envelope. 
The mucous membrane presents comparatively long, coni- 387 
THE (ESOPHAGUS. 
ent papillae of more or less dense connective tissue, containing 
looped blood-vessels, and lined throughout by stratified pave- 
ment-epithelium. These papillae attain a marked degree of 
development in the adult only. In infancy their future pres- 
ence is indicated by a 
outline at the internal attached 
border of the epithelial stratum. 
This latter portion of the. mu- 
cous membrane contributes 0.22 
—0.26 mm. toward the entire 
oesophageal thickness of about 
4.0 millimetres. 
The muscularis mucoscE con- 
sists chiefly of longitudinal, un- 
striped muscle-cells. They are 
disposed in bundles of differ- 
ent sizes, separated by varying 
amounts of connective tissue. 
Toward the inferior portion of 
the oesophagus these bundles 
approach each other, displacing 
the interposed tissue, and form- 
ing finally one continuous mus- 
Fig. 164.—Transverse section through the 
lower part of the oesophagus of the newly-born 
child; a, a, epithelium ;b, mucosa; c, muscu- 
laris mucosae ; d, submucous tissue ; e, layer of 
circular muscular fibres ; f, longitudinal muscu- 
lar layer ; (/, external fibrous layer ; h, h, two of 
the ganglia of Auerbach. Klein. 
cular layer. The thickness of this layer varies between 0.2 
and 0.3 mm. 
The submucous layer is made up of fasciculated connective 
tissue and elastic fibres. It contains groups of fat-cells, and 
lodges the mucous glands. The latter closely resemble the 
glands found in the mouth. They consist of pyramidal or poly- 
gonal secreting-cells with conspicuous rounded nuclei, and ducts 
lined by cylindrical epithelia. The lower portion of the oesoph- 
agus contains smaller and more superficial acinous glands. 
In this region they are also found in greater abundance, and 
around the cardiac orifice they form almost a complete ring. 
The muscular coat has an inner circular and an outer longi- 
tudinal layer. In man it is formed of both varieties of muscle- 
cells, the striped and unstriped. The upper portion is composed 
of striped muscle only, whereas the lower half consists exclu- 
sively of the unstriped variety. Below the upper one-eighth of 
the oesophagus smooth muscle-cells first begin to be blended 
with the other variety; they rapidly increase as we proceed 388 
MANUAL OF HISTOLOGY. 
downward, until at about the middle of its course the striped 
fibres entirely disappear, being replaced by continuous layers 
of unstriped muscle-cells. 
Thq fibrous envelope consists of connective tissue and elastic 
fibres, arranged so as to form a thin, peripheral, sheath-like 
membrane. 
Blood-vessels and lymphatics are found in less abundance 
in the oesophagus than in the mouth and pharynx. The for- 
mer are arranged in the shape of capillary networks in the 
mucosa. The papillary loops, already mentioned, take their 
origin from these reticula. The larger branches are found in 
the submucosa. The lymphatics occur as plexuses; one is 
situated superficially in the mucous membrane, and communi- 
cates by capillary vessels, with a second larger one, placed in the 
submucosa. The glands are said to have special lymphatics. 
Nerves.—An elaborate account of the mode of distribution of 
nerves in the oesophagus is given in Ranvier’s “ Lemons d’ana- 
tomie generate,” 1880, p. 366 et seq. The following brief sum- 
mary gives the main.points : Nervous filaments proceeding from 
the pneumogastrics find their way to the striped muscles, where 
they terminate in the well-known eminences ordinarily found in 
that tissue. These terminal bodies are seen to be very numer- 
ous, a fact which corresponds to the importance and complex- 
ity of nervous action concerned in the process of deglutition. 
The terminal distribution in the unstriped muscle presents no 
striking peculiarity. Between the two layers of the muscle- 
coat we find an arrangement analogous to Auerbach’s gangli- 
onic plexus, but the ganglia and their nerve-cells are larger and 
appear to be more numerous than in the intestine. The nerve- 
fibres proceeding from the vagus are medullated; those from 
the ganglionic plexus belong of course to the non-medullated 
variety. 
THE STOMACH. 
The serous covering of this organ has the same general 
structure as all visceral peritoneum, being composed of a con- 
nective-tissue membrane lined by fiat endothelial cells. 
The muscular coat of the stomach is divisible into three 
layers, composed of, 1, external longitudinal fibres; 2, middle 
circular; and 3, internal oblique fibres. All of these belong THE STOMACH. 
389 
exclusively to tlie unstriped variety of muscle-cells. A 
thickening of the inner circular layer constitutes the pyloric 
sphincter. 
The submucous layer is composed of loose connective tis- 
sue, and it is for this reason that the mucous membrane is so 
freely movable over the muscular coat. It is, moreover, owing 
to this peculiarity that, 
whenever and wherever 
muscular contraction takes 
place, the mucous mem- 
brane presents numerous 
folds, ridges, and eleva- 
tions. Thus, we may find 
in a perfectly healthy stom- 
ach appearances quite an- 
alogous to those described 
by pathologists as the so- 
called etat mamelonne of 
gastritis. 
Tire muscularis mucosce 
frequently presents two lay- 
ers of unstriped muscle- 
cells—an outer longitudinal 
and an inner circular one. 
In some regions we observe 
only one layer of longitu- 
dinal muscle-cells. 
The gastric mucous mem- 
brane is covered by a single 
layer of columnar epitheli- 
um, containing goblet-cells 
in greater or less abun- 
dance, These goblet-cells 
Fig. 165.—Transverse section through the fundus of 
the stomach in a child : a, a, cylindrical epithelium; 
6, &, peptic tubes; c, c, muscularis mucosas ; d, d, sub- 
mucous tissue ; e, circular muscular layer: /, longi- 
tudinal muscular layer ; g, peritoneum ; h, h, ganglion 
of Auerbach. Klein. 
represent ordinary epithelia, which appear to be bulged out 
by mucoid contents. At the cardiac extremity of the stomach 
there is a sharp, serrated line of demarcation between the 
oesophageal and gastric epithelial lining. The surface-epithe- 
lium forms one continuous stratum, and is continued down 
into the ducts of the gastric glands. The latter occur in two 
distinct varieties, viz., peptic glands and pyloric glands. 
Thq peptic glands, also called gastric glands, are cylindrical 390 
MANUAL OF HISTOLOGY. 
tubules, nearly straight or slightly tortuous, with often a single 
rounded csecal extremity. However, the latter is sometimes 
double by dichotomous division, or we find many such blind 
terminal branches. Hence, we may speak of simple peptic 
glands and compound peptic glands. They are all placed ver- 
tically to the surface, 
and consist of a homo- 
geneous basement-mem- 
brane with a lining of 
secreting epithelia. (Fig. 
166.) The basement- 
membrane contains flat- 
tened nuclei, and at its 
inner aspect it is fur- 
nished with flat, branch- 
ing adventitial cells. 
Each gland is divisible 
into a duct and gland 
proper. The latter, 
again, consists of a neck, 
body, and fundus. 
Usually, two, three, 
or even more of these 
glands, have a common 
duct. The length of the 
entire structure varies in 
the different gastric re- 
gions from 0.4—2.0 mm., 
in accordance with the 
thickness of the entire 
mucous membrane in the 
respective parts. The 
duct, amounting to 
about one-fourth of the 
whole length of the tube, 
is lined with one contin- 
Pig. 166.—A, simple gastric gland; P, parietal; and 0, 
chief cells. B. compound gastric gland. Only the outline, 
denoting the membrana propria, is drawn. 
uous layer of columnar epithelial cells, similar to the surface 
epithelium of the rest of the stomach. The neck, the thin- 
nest portion of the minute tube, has similar cells; but they 
appear shorter, darker, and have a smaller ovoid nucleus. As 
regards its breadth, the body stands about midway between 391 
THE STOMACH. 
the neck and the fundus, which latter is the thickest portion 
of the entire gland. In the neck we also find, in addition to 
the cells already described, other corpuscles placed externally 
to the former. They are the parietal cells (Heidenhain), or 
delomorphous cells (Eollett), the former variety being termed 
chief cells (Heidenhain), or adelomorphous cells (Eollett), or 
simply peptic cells. The parietal cells occur as spheroidal, 
oval, or polygonal, rather opaque, sometimes very granular 
bodies, which lie beneath the basement-membrane, but com- 
monly outside the layer of ordinary chief cells. In the body 
of the gland-tube we again meet with these two forms of lin- 
ing-corpuscles. Here, however, the columnar or chief cells are 
longer than in the neck, and their bodies generally appear 
more transparent, while the nuclei, again spheroidal, are situ- 
ated nearer the external than the internal border. Klein de- 
scribes the substance of these cells as consisting of a delicate 
reticulum, with a small amount of a hyaline interstitial sub- 
stance in its meshes. The same author, also, invariably finds 
an intra-nuclear network. Others have been less fortunate in 
finding such appearances. The parietal cells of the body in 
all respects resemble those of the neck. As the fundus is ap- 
proached their number grows comparatively less. 
Thq pyloric glands, which some histologists insist on call- 
ing mucous glands, are lined throughout by a single layer of 
epithelium. This is composed of the ordinary columnar cells 
of the gastric surface. But the corpuscles here appear to be 
somewhat compressed, so that they seem less transparent than 
elsewhere. They are known to undergo certain changes dur- 
ing their passage from activity to rest. Examined in the 
latter condition, we find them more granular, and apparently 
smaller or shorter, than during and immediately after secre- 
tion. These glands have long ducts, each one serving for sev- 
eral secreting tubules. Their bodies are branched, and usually 
appear somewhat tortuous. When such glandules become 
somewhat more complex and grow larger (a change which nor- 
mally takes place in the duodenum), they are called Brunner’s 
glands. 
Dr. Edinger has recently {Archiv f. mikr. Anat., Yol. 
XVII., p. 198) asserted that the gastric glands contain in 
reality only one kind of cellular element. He based his 
opinion on results obtained by treating the almost living mu- 392 
MANUAL OF HISTOLOGY. 
cons membrane with osmic acid, after Hussbaum’s method. 
By him the chief cells are said to develop into parietal cells, 
through an increas > of their volume and a filling up with the 
gastric ferment. The considerations which led him to form 
this opinion are as follows; 1, the occurrence of bodies which 
represent transition-forms between chief cells and parietal 
cells; 2, the analogy of this assumed metamorphosis of gas- 
tric corpuscles {i.e., the conversion of chief cells into parietal 
cells), with similar changes, known to occur in other glands 
during active secretion ; 3, the fact that many animals which 
secrete pepsin have only the parietal cells ; 4, the results of an 
examination of the mucous membrane of starving animals, 
which revealed only the chief-cell form of gastric corpuscles; 
and 5, the apparent discrepancy in the descriptions of these 
bodies by competent histologists—some observers regarding 
the chief cells, others the parietal cells, as exclusively pepsin- 
ogenous. 
Still more recently, Stdhr has (Verhandl. d. pTiys.-med. 
Gesel. in Wurzburg, 1881, p. 101) studied the histology of the 
gastric epithelium. His specimens were derived from the fresh 
stomach of a criminal immediately after execution of the latter. 
The man had taken no nourishment for some hours before his 
death. The principal conclusions of Stdhr are: 1, the epithe- 
lia of the mucous glandules are not destroyed during the pro- 
cess of secretion, but, like those of the true gastric glands, con- 
tinue their existence; 2, the parietal groups of cells represent 
those portions of the mucous corpuscles which have not un- 
dergone mucoid metamorphosis, being made up of unaltered 
protoplasm. 
From the above contradictory statements it appears that 
even to-day our intimate knowledge of the gastric mucous 
membrane, and especially its epithelia, is far from being in a 
satisfactory condition. It will have to be reserved for future 
investigations to dispel the uncertainty still existing with re- 
gard to some of the most interesting details of the physiologico- 
histological characteristics of the inner coat of the stomach. 
The blood-vessels of the stomach have an arrangement simi- 
lar to that of the oesophagus. In the mucous membrane, how- 
ever, we find abundant plexuses of capillary vessels surround- 
ing the gastric glands. These networks intercommunicate, and 
just beneath the surface-epithelium they become especially THE STOMACH. 
393 
close. From tins point the veins take their origin. The ve- 
nous rootlets unite in a stellate manner to form larger branches, 
which descend almost vertically and empty into a venous retic- 
ulum situated between the glandular layer and the muscularis 
mucosse, and just above a similar arterial network. 
Lymphatics abound in the stomach. They appear to 
arise from superficial loops, which, anastomosing between the 
Pig. 167.—Lymphatics of the gastric mucous membrane of the human adult. Frey. 
glandular tubules, reach the fundal zone of these structures. 
There they form a network, and this is in communication 
with a plexus of larger vessels, situated in the submucous 
tissue. 
The distribution of the gastric nerves does not differ mate- 
rially from that of the small intestine, in the description of 
which this matter will receive more particular attention. Gan- 
glion-cells are frequently found both in the muscular layer 
and the submucosa ; in the latter we have a tolerably distinct 
plexus of nerve-filaments and ganglion-cells. 
Of the normal occurrence in the walls of the stomach, of 
true lymphoid follicles, the author has been unable to find 
convincing evidence. Nevertheless some writers assert that 
they are always to be found there. 394 
MANUAL OF HISTOLOGY. 
THE SMALL INTESTINE. 
Tlie serous coat presents no structural characteristics pecu- 
liar to itself, closely resembling the gastric peritoneum. It 
encloses a muscular coat and the mucous membrane, which are 
held together by connective tissue. The average thickness 
of these layers does not, in man, exceed 1.0 mm., of which 
three-fourths belong to the muscular, and one-fourth to the 
Vis. IGB.—Longitudinal section of the small intestine of a rabbit: Z, Z, villi; J, crypts; Pp, a Peyer's 
patch; K, cap of a follicle ; S, submucosa; m. m, muscularis mucosae ; R, circular muscular layer ; L, 
longitudinal muscular layer; P, peritoneum. Verson. 
mucous coat. Of course, the contracted or relaxed condition 
of the intestinal tube at the time of measurement will appre- 
ciably influence these figures. But they represent the general 
ordinary average. 
The muscular coat has an external longitudinal and an in- 
ternal circular layer. Between the two we find Auerbach’s THE SMALL INTESTINE, 
395 
plexus myentericus of flat nerve-fibres, which will be described 
farther on. The muscle-coat becomes gradually thinner as we 
pass from the duodenum to the ileo-csecal valve. In the for- 
mation of this thickened fold the longitudinal layer does not 
participate. 
The unstriped muscle-cells have an average length of 0.255 
mm., and are about 0.005 mm. broad. They are arranged in 
bundles, surrounded by connective-tissue bands, with which 
elastic elements are abundantly interwoven. 
The mucous membrane is thrown into folds, and is studded 
with closely placed projections, called villi. The general di- 
rection of these folds, the ralmilce connirelites Kerkringii, is 
parallel to the transverse course of the circular muscle-layer. 
They run parallel to one another, or join at acute angles. 
The mill jut out into the lumen of the intestinal canal, as 
variously shaped projections, of an average length of 0.04—0.6 
mm,, and an average breadth of 
0.06—0,12 mm. In general their 
form may be said to be conical or 
cylindrical; but we always en- 
counter a great variety of shapes, 
in accordance with the varying 
states of contraction in the mus- 
cularis mucosse. Each villus con- 
sists of a large-meshed reticulum 
of connective tissue, infiltrated, as 
it were, with leucocytes, and con- 
taining flattened corpuscles, which 
resemble endothelial cells. One or 
several spaces, situated in the cen- 
tre of every villus, constitute the 
origin of the lacteal tubes. Ac- 
cording to Briicke, these chyle- 
vessels are covered by thin, but 
Fig. 169.—Section of a villus from the 
intestine of a rabbit: a, epithelium; 6, 
stroma; o, central cavity. Verson. 
not continuous bundles of smooth muscle-fibres. Their walls 
show only a single layer of ordinary endothelial cells, with 
clear oval nuclei. The free surface of the villi, like that of the 
stomach, is covered by a single layer of columnar epithelium. 
Each cell presents, in the recent state, a finely striated hyaline 
band at its unattached border. This structure has, at different 
times, received various interpretations, and even now opinions 396 
MANUAL OF HISTOLOGY, 
are much divided as to its true significance. Some histologists 
regard the striae as indicating so many minute pores for pur- 
poses of absorptive transmission ; others believe that the jux- 
taposition of numerous delicate rods explains the peculiar ap- 
pearance ; and Klein has lately asserted them to be merely 
prolongations of the fibrils of the cell-substance composing 
the epithelia. These striae are always seen to run parallel to 
the long axis of the cells. 
Krause also described as of normal occurrence, a basal pro- 
cess extending at an obtuse angle from the attached surface of 
these bodies, and inserted into the delicately serrated border 
of the villi. Near its attached border each epithelium presents 
a bright ovoid nucleus, with one or more distinct nucleoli. 
Besides the ordinary corpuscles, we find interposed between 
them the so-called goblet-cells. These are derived from the 
former by mucoid infiltration of the cell-body, which is there- 
fore conspicuously bulged out. Lymph-corpuscles also occur 
between the epithelia. 
Immediately beneath this layer we find a delicate, homo- 
geneous basement-membrane, composed of flattened cells, re- 
sembling endothelia. 
The muscular is mucosce, or muscle of Brucke, is made up of 
a single or double layer of smooth muscle-cells. When double, 
an inner circular may be distinguished from an external longi- 
tudinal coat, both being always very attenuated. 
The submucous layer is formed of connective tissue, the 
supporting framework of which contains lymphatics, blood- 
vessels, nerves, and often groups of fat-cells. 
The glands of the small intestine are those of Brunner and 
the crypts of Lieberkiilm. In addition to these, however, there 
occur numerous lymphoid follicles, which, when found singly, 
are known as the solitary follicles, and, when grouped together, 
as agminated glands, or Peyeds patches. The solitary or 
closed follicles are real lymphoid glands, and, like these, con- 
sist of reticulated connective tissue, the meshes of which are 
replete with lymph-corpuscles. The jejunum, ileum, and colon 
all contain such follicles, but the agminated glands occur in 
the ileum, abounding especially at its lower part. Around 
each follicle we find a ring of villi and glands, which arrange- 
ment goes by the name of corona tubulorum (Muller). The 
follicles receive an enveloping layer of fibro-connective tissue. THE SMALL INTESTINE. 
397 
Brunner's glands lie in the submucosa, where they form 
closely crowded tubules, separated by a small amount of con- 
nective tissue. Smooth muscle-cells, starting from the muscu- 
. laris mucosm, are often seen to pass between them. These con- 
voluted tubules resemble and correspond to the gastric glands, 
but have here attained a much greater degree of development. 
Fig. 170.—Vertical section through a human Payer’s patch, with its lymphatics injected : a. intestinal 
villi with their lacteais ; b, Lieberkiihnian glands: c, muscular layer of the mucous membrane; d, apex 
of the follicle; e, middle zone of the follicle; /, basis portion of the follicle ; (j. continuation of the lacteals 
of the intestinal villi into the mucous membrane proper: h. reticular expansion of the lymphatics in the 
middle zone: i, their course at the base of the follicle ; Ic, continuation into the lymphatics of the submu- 
cous tissue; I, follicular tissue in the latter. Frey. 
They also appear to have been pushed down, as it were, from 
the mucous into the submucous layer. 
An individual gland consists of its long duct lined by col- 
umnar epithelium, and the branched tubules, which frequently 
have terminal clusters, resembling true acini. They are, how- 
ever, only secondary or tertiary diverticula, so that Brunner’s 
glands really conform to the compound tubular type of secret- 
ing structures (Renant). Each ultimate diverticulum has an 
external membrana propria composed of flattened endothelial 
cells, and a lining of cylindrical, columnar, or prismatic secret- 
ing epithelia, containing oval nuclei. 
Histologists have described minute capillary channels pro- 
ceeding from the central lumen of the gland, between the se- 
creting-cells, ending just underneath the membrana propria. 
The author believes these intercellular channels, as they have 398 
MANUAL OF HISTOLOGY. 
been called, to be tlie artificially altered cement-substance al- 
ways present between such adjacent cells. Brunner’s glands 
abound only in the duodenum, but a few may occasionally be 
seen lower down the intestine. Their ducts, after traversing 
the muscularis mucosae, ascend almost vertically between the 
crypts, opening on the free surface of the mucous membrane. 
Tig. 171.—Crypts and interfollicular connective tissue, from the intestine of the rabbit: K, crypt; 
a, a, epithelium; cl, adenoid tissue, from which the cells have been removed by pencilling; T, fibrous 
tissue on the opposite side. Verson. 
These crypts represent open spaces within the so-called 
follicles of Lieberlaohn, which are tubular glands placed verti- 
cally in the intestinal mucous membrane, existing throughout 
its entire extent. 
They form a continuous layer, except where the upward 
projection of a lymph-follicle creates an interruption. These 
glands open at the base of the villi, the epithelial covering of 
the latter being continued down into the tubular depressions 
which they constitute in the mucous membrane. The cells of 
this stratum naturally appear broader at their attached than at THE SMALL INTESTINE. 
tlieir free extremities. A continuation of the villous basement- 
membrane forms the membrana propria of the crypts of Lie- 
berkuhn. External to this we find the surrounding connective 
tissue, which is disposed in reticula, containing many leuco- 
cytes in its meshes. Hence it is also known as adenoid tissue. 
The blood-vessels enter and leave the intestine at the me- 
senteric margin. The arteries, generally accompanied by one 
or two veins, pierce the muscle-coat, giving off branches which 
form networks in those layers, then enter the submucosa, where 
they run parallel to the surface of the mucous membrane, and 
finally send off vertical arterioles at the base of the villi. The 
latter ascend on one side of the villus, and then suddenly 
divide into a dense capillary network. This division takes 
place near the middle, the capillaries then spreading out to the 
apex and periphery. Here they become quite superficial, being 
covered by the epithelial lining only. The venous rootlets of 
the villus are generally two, or even three in number. About 
the glands and follicles we encounter special networks with 
variously shaped meshes. 
Lymphatics are found in all the layers of the intestinal 
canal. Those of the serous coat empty into the large mesen- 
teric trunks. In an inward direction we also find a network of 
lymph-capillaries between the two layers of the muscle-coat. 
The submucous layer contains the perifollicular lymph-sinuses 
situated at the base of these bodies, and a reticulum of larger 
channels, many of which are found provided with valves. The 
lymphatics of the mucous membrane are present in the shape 
of capillary networks surrounding the intestinal glands. 
In the villi we note, as already stated, one or more central 
lacteals, communicating at the base of these structures with 
the lymph-vascular networks situated around and between the 
glands. 
The nerves of the intestine are known as the plexus of 
Auerbach, and of Meissner. The former, situated between 
the circular and longitudinal fibres of the musculosa, is com- 
posed of flattened nerve-branches, made up of numerous ulti- 
mate fibrils. Small nodules, containing characteristic gan- 
glion-cells, are also found, while little twigs are given off from 
the plexus myentericus, to be distributed to the layers of the 
musculosa. 
The plexus of Meissner is situated in the submucous tis- 400 
MANUAL OF HISTOLOGY. 
sue. Its component nerves are less flattened, but are likewise 
provided with ganglia containing variously shaped ganglion- 
cells. This plexus also gives origin to the secondary networks 
of the muscularis mucosm, and is besides connected by certain 
branches with Auerbach’s plexus. 
THE LARGE INTESTINE. 
The histological structure of the colon, broadly speaking, 
very nearly resembles that of the preceding section of the ali- 
mentary canal. The lining epithelium of the mucous mem- 
brane presents the same characteristic appearances as in the 
Fig. 172.—Section of the large intestine of a rabbit: J, crypts of Lieberkiihn ; a, epithelium ; 6, mu- 
cosa ; m, muscularis mucosse ; s, subnmcosa: H, circular muscular layer; L, longitudinal muscular layer; 
p, peritoneum. Verson. 
small intestine. The mucosa of the colon is, however, devoid 
of villi; but it shows numerous crescentic folds. The muscu- 
laris mucosse will be found to answer to the description already 
given of that layer in the small intestine. 
The submucosa also shows the same morphological compo- 
sition, but appears to be much richer in deposits of fat-cells. 
Aggregations of lymph-follicles are not generally found, but 
large, conspicuous solitary glands abound throughout. 
The crypts of Lieberkiihn are identical with the glands of THE EECTUM. 
401 
the same name found in the small intestine. As we approach 
the rectum an increase in their length becomes apparent. 
In the vermiform appendix we find the collection of solitary 
lymph-follicles so closely placed that the space left between 
adjoining glands does not equal in diameter that of these struc- 
tures themselves. 
The longitudinal layer of the muscle-coat is quite thin be- 
tween the tsenise coli, or flat longitudinal bands of the large 
intestine. These bands themselves represent thickened layers 
of the musculosa. It appears that the circular fibres are espe- 
cially developed in the portions between the sacculi of the 
caecum and colon. 
The Mood-vessels are arranged after the same plan as in the 
small intestine. In the submucosa are contained large trunks, 
running parallel to the surface. Capillaries arise from these, 
and ascend almost vertically between the crypts of Lieberkuhn, 
the capillary network surrounding those structures being only 
moderately developed. 
As regards the lymphatics, they have a distribution similar 
in all essential respects to that found in the small intestine. 
The nerves likewise imitate in their structure and arrange- 
ment those encountered in the small intestine. Meissner’s 
plexus appears to be provided with comparatively large gan- 
glia and relatively small component cells. The plexus of 
Auerbach also attains conspicuous development in the large 
intestine. 
THE EECTUM. 
The internal sphincter ani represents a thickening of the 
circular layer of the muscle-coat. In its upper portion the 
rectal mucous membrane is like the same structure of the large 
intestine. Lower down we find the columnar epithelium grad- 
ually replaced by stratified pavement-epithelium. 
The follicles of Lieberkuhn are large and long. Finally, 
the mucous membrane gradually passes into the ordinary in- 
tegument surrounding the anal orifice. 
The blood-vessels, lymphatics, and nerves resemble in their 
distribution those of the colon, and are devoid of characteristic 
peculiarities. 402 
MANUAL OF HISTOLOGY. 
BIBLIOGRAPHY. 
Bcehm. De glandularum intest. struct, penit. Berol., 1835. 
Henle. Symbol, ad anat. vill. intest. Berol., 1837. 
Bischoff. In Muller’s Archiv, p. 503, 1838. 
Wasmann. De digestione nonnulla. Berol., 1839. 
Middeldorpp. De glandulis Brunnianis. Yratisl., 1846. 
Brettauer and Steinach. Unt. iiber d. Cylinderepithel. Vienna, 1857, 
Leyjdig. Histologie. 1857. 
Auerbach. Ueber einen Plexus myentericus. Breslau, 1862. 
Auerbach. Yircb. Arch., Vol. XXXIII., p. 340. 1865. 
Letzerich. In Virchow’s Archiv, Vol. XXXVII., p. 232. 1866. 
Eimer. Zur Geschichte der Becherzellen. Berlin, 1868. 
Schwalbe. Arch. f. mikros. Anat., Vol. VIII., p. 92. 1872. 
Heidenhain. Arch. f. mikros. Anat., Vol. VIII., p. 279. 1872. 
Gerlach. Ber. d. sachs. Ges. der Wiss. Leipzig, February, 1873. 
Krause. Handb. d. menschl. Anat., Band I, 1876. 
F. Hoffmann. Die Follikel des Diinndarms beim Menschen. Munich, 1878. 
Sertoli. Contribuzioni all’ anatomia della mucosa gastrica. Arch, di med. veter. 
Fasc. 3, p. 15. 1878. 
Rudinger. Beitr. z. Morphol. d. Gaumenseg. u. des Verdauungsapp. Stuttgart, 
1879. 
H. Sew all. Devel. and Regen. of the Gastric Gland, Epithel., etc. Journal of 
Phys., Vol. I, p. 321. 1879. 
Edinger. Zur Kenntniss d. Drixsenzellen d. Magens. Arch. f. mikros. Anat., Vol. 
XVII., p. 198. 1879. 
Ranvier. Les muscles de I’oesophage. Journ. de micrographie, 111., p. 9. 1879, 
Renaut, G. Note sur la structure des glandes a mucus du duodenum. Gaz. med. 
de Paris, No. 41, 1879, and Progres med., No. 23, p. 439. 1879. 
Ranvier. Leqons d’anat. generate. Paris, 1880. 
P. Stohr. Ueber das Epithel. des menschl. Magens. Verhandl. der phys.-med. 
Gesellschaft in Wurzburg, p. 101, 1881, CHAPTER XXV. 
THE SPLEEN, PANCREAS, THYMUS, THYROID AND PINEAL 
GLANDS, AND PITUITARY BODY. 
Professor of Physiology in the Woman’s Medical College, New York City. 
BrC. L. DANA, A.M., M.D., 
THE SPLEEN. 
General structure.—This organ is composed of connective 
tissue and muscular fibres, containing Malpighian corpuscles, 
pulp-substance, blood-vessels, lymphatics, and nerves. An 
outline of the general arrangement of these several elements 
will make subsequent details clearer. 
Within its peritoneal investment the spleen has, in the 
first place, an elastic fibrous capsule ; this envelops the organ 
and passes into its interior at the hilum. From the internal 
surface of the capsule are given off fibrous bands and pro- 
cesses—the trabeculae, which interlace and form a fine network. 
In the meshes of this network is a soft, reddish substance—the 
splenic pulp. The arteries, entering at the hilum, run along 
the trabeculae and end in capillaries, which gradually break up 
in the parenchyma. Attached to the walls of the .arterioles 
and bathed in the spleen-pulp are little bodies, called the 
Malpighian corpuscles. The veins begin in the pulp, and, 
gradually enlarging, pass out alongside the arteries. The 
blood thus passes out of the capillaries into the spleen-pulp, 
and from thence is collected by the veins. It passes through 
the blood-paths in the pulp much as the lymph passes through 
lymph-paths in the lymphatic glands. 
This unique structure is now to be considered in detail. 
Thz peritoneal or serous coat of the spleen resembles the 
peritoneum elsewhere. It is, in man especially, very firmly 404 
MANUAL OF HISTOLOGY. 
adherent to the fibrous coat beneath it, and closely invests the 
organ. It is reflected off at the hilnm to form the gastro- 
splenic omentum, and also at the upper border, where it in- 
vests the suspensory ligament. 
Thq fibrous coat, or capsule of the spleen, is white in color, 
and thicker than the serous coat. It is composed of fibrous 
tissue, which is permeated very extensively by elastic fibres. 
Mingled with them are a few smooth, muscular elements. At 
the hilum this fibro-muscular coat surrounds the vessels and 
nerves and passes into the substance of the spleen with them, 
forming what is called the “capsule of Malpighi.” It invests 
the arteries and veins as far as their finer branches, and gives 
off fibrous processes, which have a diameter of W mm. to 
2 mm., and which help to make up the trabecular frame- 
work of the spleen. This framework is formed by processes 
sent off from the internal surface of the spleen’s fibrous coat, 
which join with the processes sent off from the capsule of 
Malpighi, and interlace until a firm network is made. In this 
structure lie embedded the spleen-pulp and the Malpighian 
corpuscles. The fibrous sheath of the veins has a somewhat 
peculiar arrangement. It becomes at once intimately adherent 
to the venous walls, uniting them closely with the surrounding 
parenchyma. As the veins grow smaller this fibrous coat splits 
into bands containing muscle-cells, which lie longitudinally 
along the vessel-wall. These bands do not entirely surround 
the vessel, however, but allow the thin endothelium and in- 
tima to be seen between them. They finally leave the veins 
to join the trabecular framework. The tissue composing this 
framework is made up, like the capsule, of elastic and other 
fibres, with a good many smooth muscle-fibres arranged longi- 
tudinally along their course. 
Malpighian corpuscles.—The Malpighian or spleen corpus- 
cles are so intimately connected with the arteries that it will 
be necessary first to trace in part the course of the latter. The 
arteries of the spleen enter at the hilum, enclosed in a common 
sheath with the veins and accompanied by the lymphatics. 
They divide and subdivide very rapidly. When they have 
reached a diameter of about two-tenths of a millimetre, the 
veins leave them and take an independent course. At this 
point of separation, or even sooner, the outer connective-tissue 
coat of the artery begins to be transformed into the ordinary THE SPLEEN. 
405 
adenoid tissue; the fibrillse become more delicate and interlace 
in a coarser mesliwork ; in the interstices are lymph-cells and 
at the nodal points are small nuclei. Klein describes large, flat- 
tened endothelioid cells, “ endothelioid plates,” flxed upon the 
reticulum. This lymphoid tissue surrounds the artery in a 
loose coat of variable thickness. At certain points there is a 
local hyperplasia of it; it becomes massed into little ovoid or 
spherical bodies, which are called Malpighian corpuscles. 
These have a diameter of to T\ mm. They are attached 
like buds to the artery, or, not rarely, the artery pierces them 
centrally or eccentrically. When thus pierced the lymphoid 
change in the arterial coats extends much deeper. The cor- 
puscles resemble very closely the follicles in the solitary glands 
of the intestine, as well 
as those of the lymphatic 
glands (Fig. 173). They 
are composed of the same 
retiform connective tis- 
sue, in the meshes of 
which are lymphoid cells, 
with occasionally yellow 
or brown pigment. This 
retiform tissue becomes 
denser near the external 
part of the corpuscle, 
but no distinct envelop- 
ing membrane exists. In- 
deed, the external sur- 
face is generally connect- 
ed by fibrillse with the 
Fig. 173.—Prom the spleen of the Tropidonotus natrix : 
a. follicle, with its capillary plexus ; b, septum, with venous 
plexus. Muller. 
branching cells of the spleen-pulp surrounding it. Toward 
the centre the retiform tissue is more open. The cells within 
the meshes are lymph-cells of various sizes. They have an 
average diameter of mm. The smaller ones have a single 
nucleus, the larger may have several. An arterial twig enters 
the corpuscle either from the attached artery or from the out- 
side. It divides at once into capillaries, which, as a rule, have 
no regular arrangement. They receive an adventitia of lymph- 
oid tissue. Most of them soon lose this adventitia, their walls 
become rich in nuclei, branching processes are given off, and 
the structural character of the vessel is lost. They finally 406 
MANUAL OF HISTOLOGY. 
break up entirely, and their contents pass out at the periphery 
of the corpuscles into the meshes of the pulp. It is to be 
noted that the Malpighian corpuscles are the only parts of the 
spleen where capillaries exist to any extent. The arteries going 
to the pulp for the most part break up at once. 
The spleen-corpuscles differ from the lymph-follicles, par- 
ticularly, in having fewer capillaries, no lymph-paths, and in 
containing pigment in their meshes. The number of Malpig- 
hian corpuscles in a spleen of ordinary size, as estimated by 
Sappey, is about ten thousand ; but this applies to lower ani- 
mals. In man they are smaller and less numerous. Pro- 
tracted disease is thought to diminish the number. 
The spleen-pulp.—This is a soft, reddish brown substance, 
looking, when squeezed out, like grumous blood. On expo- 
sure to the air it acquires a redder hue. Under the microscope 
it is found to present a honeyconibed appearance, in the meshes 
of which are numerous lymph-corpuscles, fragments of red 
blood-corpuscles, so-called nuclei, and pigment-granules. Thus, 
we have really only a modified form of adenoid tissue. Klein 
considers that the network is made up of the large, flat endo- 
thelioid cells above referred to. Processes branching from 
these and uniting with each other form the meshes. I have 
been unable to make out the structure as Klein describes it, 
and his own observations and plates do not demonstrate it 
satisfactorily. The branching endothelioid cells are connected 
with the breaking-up and the beginning of the blood-vessels, 
but do not form the whole pulp reticulum. 
The fibrillee of this retiform tissue are connected with the 
external surface of the Malpighian corpuscles, with the lym- 
phoid tissue that ensheaths the small arteries, with the fibrous 
trabeculae of the spleen itself, and with the cell-nuclei of the 
walls of the arterioles, capillaries, and venous radicles. From 
these points they branch and interlace, enclosing the cellular 
and other elements in their meshes. These branching fibrillse 
are, as in other lymphoid tissue, of a pale, granular appearance. 
The cells enclosed in the meshes are not crowded so closely 
together as are those in the Malpighian corpuscles (Fig. 174). 
They are of different sizes ; the small ones are sometimes de- 
scribed as free nuclei. The larger ones have one, two, or more 
nuclei within them. These larger cells often contain red blood- 
globules in various degrees of disintegration, a fact which gives THE SPLEEX, 
407 
rise to the opinion that one of the functions of the spleen is to 
destroy them. The pigment-grannies are found both without 
and within the cells, and occasionally even stain the nodal 
nuclei of the sustentacular tissue. The pigment is yellowish, 
brown, or black, and there is enough of it to give a charac- 
teristic dark color to the gross ap- 
pearance of the spleen. In addition 
to the pulp-elements mentioned, there 
are, according to Fremke and Kolli- 
ker, small, yellowish nucleated cells, 
which are possibly young red blood- 
globules. 
The pulp-substance thus described 
has arterioles and capillaries ending 
and veins beginning in it. The blood 
flows from the former, through the 
spaces between the cells, into the lat- 
.tt•, • . , i 
ter. Here is every opportunity, there- 
Fig. 174.—Prom the sheep’s spleen 
(double injection) ; a, reticular frame- 
work of the pulp; 6, intermediate pulp- 
current ; c, its continuation into the 
venous roots with incomplete walls; d, 
venous branch. Frey. 
fore, for the blood to recruit itself with new white corpuscles, 
and to enrich itself with albuminous and pigmentary matter 
from disintegrated, red globules. The analyses of the blood 
in the splenic vein seem to show that it does do this. 
Blood-vessels.—We have already described, to a certain 
extent, the general arrangement of the blood-vessels, but some 
further particulars remain to be noticed. 
The splenic artery, the largest branch of the coeliac axis, 
passes to the spleen in a course so tortuous as to shorten its 
length in a straight line by one-third. It enters the gastro- 
splenic omentum, divides generally into six branches, and 
passes into the spleen at the hilum, where, in common with the 
vein, it becomes surrounded by the capsule of Malpighii. The 
branches then rapidly subdivide and decrease in size, but with- 
out anastomosing. When about two-tenths of a millimetre in 
diameter they leave the veins and receive their sheaths of lym- 
phoid tissue and Malpighian bodies, as has been described. 
They then end for the most part in capillaries, which pass to 
the Malpighian bodies and there break up in the way above 
described. But there are other capillaries which pass into the 
pulp-substance, where their walls gradually melt away, so to 
speak, into the retiform tissue that surrounds them. If one 
follows this change with a microscope, he will see the capil- 408 
MANUAL OF HISTOLOGY. 
lary tube becoming thinner and more freely studded with 
nuclei; from some of these nuclei processes are sent out which 
connect with the fibrillse of the pulp. At this stage injections 
into the capillaries pass freely out into the surrounding tis- 
sue. The exact point where the capillary wall merges into 
the sustentacular tissue can hardly be determined. 
The venous radicles begin in a somewhat similar way to 
that in which the capillaries end (Fig. 174), The sustentacu- 
lar fibrillse (endothelioid plates ?) appear to arrange themselves, 
first of all, in a circular manner, occasionally interlacing at 
right angles (Fig. 175). Lying within and upon the fibrillse 
thus arranged are 
oval cells with promi- 
nent nuclei. These 
nuclei are often con- 
nected with the sus- 
tentacular fibrillse 
outside. These cells 
are not adherent to 
each other at first, 
but, as the radicle be- 
comes more perfect, 
they unite to form a 
complete wall; the 
external layer of cir- 
cular fibrillse then 
becomes metamor- 
phosed into a tunica 
Fig. 175.—From the pulp of the human spleen, brushed preparation 
(combination): a, pn)p strand with the delicate reticular framework : 
transverse section of the cavernous venous canal; c, longitudinal sec- 
tion of such an one; <l, capillary vessel in a pulp tube, dividing up at 
e; /, epithelium of the venous canal; g, side view of the same; h, its 
transverse section. Frey. 
intima ; finally, the thick oval cells are replaced by flat endo 
thelial cells, and the complete venule is formed. 
Having shown how this vascular channel begins, we turn, 
for convenience of description, to its other end. The splenic 
vein enters the hilum, just as the artery does. As it subdi- 
vides, however, it loses both tunica adventitia and tunica me- 
dia. The internal tunic remains and becomes firmly united 
with the fibrous trabeculae of the spleen, so that, on section, 
the venous wall does not collapse, but appears like a part of 
the parenchyma. After several subdivisions the veins begin 
to anastomose, and they finally form a closely reticulated ar- 
rangement of like-sized vessels having an average diameter 
of t4o- to yfo- mm. These are called the cavernous veins. The THE SPLEEN. 
409 
brandies from them subdivide, pass into the pulp, and end in 
the venous radicles we have described. 
It is proper to state that some authors (Gray, Billroth, 
Kolliker) believe that the capillaries connect directly with 
these cavernous veins, pouring the blood into the lacunae which 
they form. Others (Key, Stieda) believe that the sustenacular 
tissue of the pulp is not composed of branching fibrillse, but 
of collapsed capillaries, which connect the arteries with the 
venous radicles. Such views cannot now be sustained. 
The lymphatics of the spleen occur in two sets; one, the 
trabecular, forms a close plexus in the external capsule and 
sends deep branches along the trabeculae, to communicate with 
the deep or perivascular set. This perivascular set arises from 
the lymphoid sheaths of the arteries, and at first has no dis- 
tinct channels. True lymphatics are soon formed, however, 
which run along the arteries, generally one on each side. At 
the hilum they unite with the trabecular set, and, passing along 
the gastro-splenic omentum, enter the neighboring lymphatic 
glands. 
The nerves are derived from the solar plexus (right and left 
semilunar ganglia and right pneumogastric). They enter the 
hilum and follow the course of the arteries ; along their terminal 
ramifications, according to Muller, are oval ganglia, through 
which a single fine capillary runs. On section of the nerves of 
the spleen the organ dilates, and on electrical stimulation it 
contracts. 
Development.—The spleen is present in all vertebrates ex- 
cept the septocardia and myxenoids (Muller). 
The organ is developed entirely from the mesoblast, and, 
according to Peremeschko, is intimately related in its origin 
with the pancreas, from which it is an offshoot. Its shape can 
be recognized in the twelfth week. The capsule, trabeculae, and 
retiform connective tissue, are first formed ; then the cells and 
Malpighian bodies appear, the latter at about the middle of 
intra-uterine life. 
Preparation of spleen for microscopical examination.— 
The methods of preparing the spleen for examination are in 
general like those for preparing lymphoid tissue anywhere. 
The organ is very soft, and the object to be aimed at is to 
harden it without interfering too much with its intimate struc- 
ture. A good method is that of Klein. The spleen should be 410 
MANUAL OF HISTOLOGY. 
first washed out with i per cent, solution of common salt until 
the fluid from the vein is clear. Then inject per cent, solu- 
tion of osmic acid or Muller’s fluid for twenty minutes. Then 
place the spleen in Muller’s fluid for ten days, at the end of 
this time small bits should be cut off and hardened in alcohol, 
when it may be stained and mounted in the ordinary way. 
The spleen of man is best prepared (E. Klein) by placing small 
bits in a large excess of per cent, chromic acid for a week. 
Then change it to a J per cent, solution, and in three days from 
this to a i per cent, solution. Finally, bits are to be placed in 
alcohol and hardened in the usual way. 
I have obtained excellent sections, however, which answered 
very well for demonstrations, by freezing the spleen of the 
living cat with the ether-spray, making sections at once, and 
staining them with Bismarck brown. In this way the retiform 
tissue even may be seen. 
THE PANCREAS. 
The pancreas is a compound racemose gland. It is com- 
posed of a central duct, which sends off branches that divide 
and subdivide until they end after the usual manner of race- 
mose glands, by opening into collections of little vesicles or 
acini. This mode of structure divides the gland into small 
lobules, between which runs areolar connective tissue. The 
same tissue envelops the whole organ. 
In each of the lobules will be found a number of acini 
grouped around the terminal extremity of a duct. These 
acini consist of a basement-membrane; lining this and almost 
filling the acinus are cubical epithelial cells. The basement- 
membrane is composed of flat, stellate cells. Owing to their 
branching, they do not form a completely homogeneous mem- 
brane. The epithelial cells lining the acini are nucleated and 
compressed closely together. Their internal portion, next the 
lumen, is granular ; the external part is clear. This granular 
part represents (Heidenhain) the mother-ferment, zymogen, 
which is transformed subsequently into trypsin. It varies in 
extent with the activity of the gland. During such activity 
the cell is smaller and the granular part less. Between the 
cells (Langerhaus, Saviotti) fine intercellular passages similar 411 
THE PANCREAS. 
to those in the liver-lobules have been described (Fig, 176). 
These intercellular passages are claimed by some, however, 
to be branching processes from the cells of the basement-mem- 
brane. Others regard them as albuminous cement substances, 
holding the secreting 
corpuscles together. 
Langerhaus describes 
branching centro-acinal 
cells connected on either 
side with similar inter- 
epithelial cells. (See Pit- 
uitary Body.) 
The excretory duct 
of the pancreas is com- 
posed of a basement- 
membrane lined with 
cells; at the lower por- 
tion small mucous 
glands open into it. The 
basement-membrane is 
thickened with fibrous 
tissue at first; but, as 
the duct divides up into 
smaller branches, this 
disappears. The lining 
cells are columnar in 
shape near the mouth of the duct; passing back, however, 
they grow shorter and more flat. Finally, on reaching the 
acini, they resemble endothelial cells, and, as such, line the 
axial cavity of the acinus. Here they form the centro-acinal 
cells referred to above. 
Fig. 176.—Glandular canals of the rabbit’s pancreas, after 
Saviotti; a, Larger excretory duct; 6, that of an acinus ; c, 
finest capillary ducts. Frey. 
The blood-vessels of the pancreas are numerous, and form a 
close capillary plexus around the basement-membrane of the 
acini. 
The lymphatics probably arise from between the acini. 
They pass out with the blood-vessels. 
The nerves are supplied from the solar plexus; through 
this fibres come from the vagus. They end, according to Pflfi- 
ger, in a manner similar to that of the salivary glands ; fine 
terminal filaments pass through the basement-membrane into 
the lining cells of the acini. Section of the vagus stops the 412 
MANUAL OP HISTOLOGY. 
secretion of the pancreas for a short time ; stimulation of its 
central end does the same. On section of all the nerves going 
to the gland, there is a paralytic tlow of the pancreatic juice. 
Development.—The pancreas appears very early in foetal 
life, developing from a mass of mesoblastic tissue in the duo- 
denal wall. It is probable that hypoblastic tissue from the 
same region passes into it from the ducts. 
THE THYMUS GLAND. 
The tlrymus gland is an organ whose function is unknown ; 
it may be classed, however, on account of its structure, with 
the lymph-glands, its tissue being of the adenoid type. It is 
loosely enclosed in a vascular connective-tissue capsule, which 
sends septa and processes into the interior of the-organ. These 
divide it up into small lobules of the size of a pin’s-head to 
that of a pea. Within the lobules are the characteristic ele- 
ments of the gland—the follicles—which are also known as the 
acini, alveoli, or granules. Running spirally through each of 
the two long lobes is a central band or canal, and, upon unrav- 
elling the gland, the various lobules are seen to be arranged 
about this. 
• The fibrous capsule is made up chiefly of white connective 
tissue, mingled with which there are fine elastic fibres and stel- 
late connective-tissue cells. At a few of the nodal points of the 
larger reticulating fibres are found peculiar cavities, lined with 
fusiform cells and containing a few tymph-corpuscles. They 
are probably connected with the lymphatics, and the fibrous 
capsule seems, as a whole, to be slightly touched with a 
lymphoid metamorphosis. The external surface of the cap- 
sule is covered with a single layer of flat epithelial cells. Deep 
in the capsule is a rich plexus of vessels, and scattered spar- 
ingly through it are medullated nerve-fibres. 
The follicles.—Enclosed in each of the lobules, and making 
up its substance, are from ten to fifteen, or even fifty (Frey), 
small, spherical or polyhedral bodies. These are the follicles 
of the gland. They are from TV to Tso mm. in diameter, and 
resemble very much the follicles in the lymphatic glands and 
Peyer’s patches, but present a more embryonal aspect. They 
are held closely together by the surrounding tissue, which THE THYMUS GLAXD. 
413 
sends septa down between them for a short distance (Fig. 177). 
On section each follicle is found to be composed of a cortical 
and medullary portion. The medullary portion is often only 
a cavity, and, as a rule, is found to connect, by a passage 
through the cortex, with a general cavity in the centre of the 
lobule. This latter cavity again connects with the spiral cen- 
tral canal. The follicle is composed of reticular connective 
tissue, in whose meshes are cells and the thymic Juice. The 
reticulum forms an adventitia for the blood-vessels. In the 
cortical portion this reticular tissue is made up of small, nucle- 
ated cells, with long, fine, branching processes. In the medul- 
lary portion, when present, the reticular cells have large nuclei, 
and tlieir processes are 
coarse and short. Within 
the meshes of the structure 
thus described are cells, 
fat-globules, capillaries, 
and a peculiar, transpar- 
ent, acid, viscid, albumi- 
nous fluid the thymic 
juice. The cells are: 1, 
lymph-corpuscles, which 
exist in the greatest abund- 
ance ; 2, large, granular, 
nucleated cells of various 
sizes—many of these have 
long processes, and they 
help to form, partly by a 
Fig. 177.—Portion of the calf’s thymus, after His: The 
rings of the arterial branches (a) and venous branches (6) 
with the capillary net-work (c) and the cavities of the 
acini (d). Frey. 
process of vacuolation (Watney), the concentric corpuscles ; 
3, giant cells ; 4, the concentric corpuscles of Hassall. These 
last consist of one or more cells, around which are arranged 
concentric layers of flat, epithelioid cells. This concentric en- 
velope suggests the epithelial cylinders seen in carcinomatous 
growths. One or two of these corpuscles may be enclosed in 
another common envelope, thus forming a compound concen- 
tric corpuscle. These corpuscles are strongly refractive, and 
are readily stained with carmine. They lie near the arteries, 
and have an intimate relation with them. According to Afan- 
assien, indeed, they are developed from the endothelium of the 
arterial wall. There is a vascular plexus about the follicles, 
from which capillaries pass into the interior, forming a fine net- 414 
MANUAL OF HISTOLOGY. 
work. They generally pass in as far as the medullary portion 
or central cavity, and form a ring about this. 
The central canal, or band of the thymus, is lined with a 
vascular membrane, and communicates with the central cavi- 
ties of the lobules and follicles. Along its interior the bulg- 
ings of attached vesicles, or groups of the same, may be seen. 
Many authorities consider that the central cavities in the 
follicles and lobules are produced artificially by the break- 
ing down of the very delicate tissue. There is much proba- 
bility that this is the case. More investigation, however, is 
needed, and meanwhile the cavities and canals are described 
as above, since it is extremely rare to find a human thymus in 
which they do not appear to exist, no matter how careful the 
preparation. 
The blood-vessels.—The thymus is not a very vascular 
gland. Its arteries are distributed in the capsule and along 
the central band. From these parts they pass unaccompanied, 
as a rule, by the veins, to the interlobular tissue, and are dis- 
tributed to the follicles, as has been described. 
The lymphatics accompany the blood-vessels along the 
central band. From there it is stated (His) that they pass to 
the interlobular tissue and are distributed around the follicles, 
communicating by minute channels with the centre of the fol- 
licle. This latter point, however, lacks confirmation. 
Development.—The thymus gland is found in all vertebrates 
except amphioxus (Huxley). It is developed, like the lym- 
phatic glands, from the mesoblastic layer, and can be seen 
early in foetal life. It appears first as a closed tube, which is 
probably (Quain) a mass of embryonic cells enclosed in a mem- 
branous capsule. Along this projections bud out which are 
gradually transformed into lobules. By the twelfth week it 
has become well developed. 
The thymus is an organ of foetal and infant life only. It 
grows rapidly until the second year, when it begins to undergo 
a fatty degeneration and atrophy. By the seventh or eighth 
year it is a small, fatty mass. This degeneration of the thy- 
mus takes place in all the animals which have the gland. 415 
THE THYROID BODY. 
THE THYROID BODY. 
Tlie thyroid body is a dark red, vascular organ, composed 
of two lobes. It seems very possible that we may now legiti- 
mately call it a secreting gland, whose product acts upon the 
red blood-cells, and is carried away by the lymphatics. 
The entire organ is enclosed in a thin, but firm, fibrous cap- 
sule. This sends off processes to the interior, which interlace, 
forming a sponge-like network. This network is thin, however, 
and does not make up much of the substance of the gland. A 
few elastic fibres run in it. Enclosed in the meshes of the frame- 
work thus formed are the vesicles of the gland. These are 
very numerous and make up the bulk of the organ. They are 
minute, spherical, ovoid, or flattened bodies, whose diameter 
is from Tfo mm. in the embryo to 2 mm. in the adult, and are 
grouped into small lobules of various sizes. They consist of 
a homogeneous connective-tissue basement-membrane, lining 
which is a single layer of epithelial cells, the whole enclosing 
a yellowish, transparent, viscid fluid. The 
lining-cells, in adults, measure about Tfg- 
mm. in height and mm. in width. They 
contain nuclei, and sometimes nucleoli. 
They are loosely connected to the base- 
ment-membrane, and, with extra-uterine 
life, begin to break away into the interior 
of the vesicle. Baber describes fine, longi- 
tudinal striae passing from the base toward 
the apex of the cell. These cells have a 
tendency to undergo colloid degeneration. 
The cell-body swells up, and bursting, the 
contents spread out in the vesicle-cavity, 
there to undergo or complete the metamor- 
phosis (Fig. 178) mentioned. According 
Fig. 178.—Colloid metamor- 
phosis : a, Gland vesicle of the 
rabbit; 6, commencing colloid 
metamorphosis of the calf. 
Frey. 
to Baber, however, the cells which undergo this degenera- 
tion come from the connective tissue surrounding the vesicles. 
They pass through the vesicle-wall into its cavity, and there 
gradually break up. This change goes on at the expense of 
the vesicle-wall and the intervesicular tissue, so that in time 
the gland, without being much enlarged, may appear, on sec- 
tion, almost like a single colloid mass. 416 
MANUAL OF HISTOLOGY. 
The normal fluid contents of the vesicle coagulates with 
heat and alcohol, without losing its transparency. Floating in 
it are granules, cells, and occasional translucent, curiously 
shaped bodies called sympexions (Robin). The cells come 
from the vesicle-wall and the intervesicular tissue. Many of 
them have lost their nuclei. The “sympexions,” if they uni- 
formly occur, have not been shown to have any significance. 
Baber has recently announced the very interesting fact that 
large numbers of colored and colorless blood-corpuscles are to 
be found in the vesicle-cavities of the thyroid of man and lower 
vertebrates. The colored cells, which largely preponderate, are 
in a state of partial disintegration. This explains the yellowish 
color of the vesicle-contents, and the inference is drawn that the 
thyroid has the function of destroying red blood-corpuscles. 
The blood-vessels of the thyroid are quite numerous. They 
ramify in the capsule along the trabeculae, and finally form a 
rich plexus about the vesicles, but do not penetrate the inte- 
rior. The walls of the veilis are united firmly to the fibrous 
reticulum of the gland, so that when a section of them is made 
they do not collapse. 
The lymphatics form large and numerous trunks, both on 
the surface and in the interior of the organ. They originate 
by coecal extremities lying in the tissue between the vesicles. 
These unite to form trunks which surround the lobules, and 
give off branches that pass to the capsule. There a thick, per- 
ipheral network is formed, from which lymph-trunks pass to 
the thoracic and right lymphatic ducts. They contain a viscid 
substance like that in the vesicles themselves, and it seems 
probable that they have something to do with carrying off this 
fluid. 
The nerves are from the middle and inferior cervical gan- 
glia, but not (Frey) from the pneumogastric. They enter the 
gland along the trabeculae and pass between the vesicles. Gan- 
glion-cells, either single or in groups, are met with in their 
course. The mode of termination is not known, more than 
that they seem to dwindle away into fine, terminal fibres, that 
are lost in the connective tissue. THE PITUITARY BODY. 
417 
THE PINEAL GLAND. 
The pineal gland, or conarium, is a small body, about the 
size of a pea, resting upon the nates and covered by the back 
part of the corpus callosum. It consists of a fibrous capsule 
and framework, lying in which are vesicles, cells, blood-ves- 
sels, and sabulous matter. There is generally a cavity near the 
base of the gland. 
The interior of the structure is divided into a cortical and 
medullary portion. The former is composed of little vesicles, 
resembling those of the pituitary body. The central portion 
is filled with nerve-cells and sabulous matter, the latter lying- 
in the cavity at the base. The nerve-cells are of two kinds: 
one, large, -fa mm- in diameter, and giving off long pro- 
cesses ; the other, very small, T-}w mm. in diameter, and giving 
off processes, in the adult. Nerve-fibres run among these 
cells, and connect them to the medullary substance of the 
cerebral lobes and to the crura cerebri. They are considered, 
by Meynert, to be ganglion-cells giving origin to fibres in the 
crura cerebri. 
The sabulous matter is composed of corpora amylacea and 
of earthy salts combined with animal matter. The earthy 
salts are: phosphate and carbonate of lime, phosphate of am- 
monia, and magnesia (Stromeyer). 
There is no doubt that the pineal gland contains consider- 
able nervous tissue. It is not yet determined, however, whether 
it should be considered a ganglionic centre or a structure of 
similar character to the suprarenal capsules. 
THE PITUITARY" BODY. 
The pituitary body {hypophysis cerebri) is notable for the 
peculiarity of its development and its uniform presence in all 
vertebrates. It is a small, reddish gray, vascular mass, ovoid 
in shape, and situated in the sella turcica. It is composed of 
two lobes, anterior and posterior, the former being the large]'. 
In structure, the body, in its anterior lobe, has some resem- 
blance to the suprarenal capsules, being composed of a con- 
nective-tissue framework, in which lie blood-vessels and closed 
vesicles. These latter consist of a homogeneous membrane en- 418 
MANUAL OF HISTOLOGY. 
closing nucleated and nucleolated cells, mostly epithelial in 
character. These cells generally line the interior of the vesicle 
and nearly fill its cavity, so that on section the vesicle looks 
somewhat like an acinus of the pancreas. In the centre there 
is often a branched nucleated corpuscle connected with a simi- 
lar cell on one or the other side (Klein). The cells vary much 
in size. In the connective tissue around the vesicles are lym. 
phatic spaces and blood-vessels. 
The posterior lobe is smaller, darker, and more vascular 
than the anterior. During foetal, and perhaps infant life, it 
has a cavity in its interior lined with ciliated epithelium and 
connected by the infundibulum with the third ventricle. 
Development.—The pituitary body is formed by a diverticu- 
lum from the future mouth (buccal epiblast), which projects 
up to be transformed eventually into the anterior lobe ; and 
another diverticulum from the wall of the vesicle of the third 
ventricle, which projects down to form the posterior lobe 
(Quain). Epiblastic and mesoblastic tissue are thus united in 
the organ. The posterior lobe retains its nervous elements in 
the lower animals, but in man contains little besides connective 
tissue and blood-vessels. 
BIBLIOGRAPHY. 
The Spleen. 
Muller, Wm. Ueber den feineren Bau der Milz Leipzig und Heidelberg, 1865. 
Peremeschko. Beitrage zur Anatomie der Milz, und Ueber die Entwicklung der 
Milz. Sitzungsberichte der k. k. Akademie. Zu "Wien, 1867. 
Stricker, S. Manual of Histology. 1873. 
Quain. Elements of Anatomy. New York, 1877. 
Bacelli. Venous Circulation of the Spleen. Med. Times and Gaz., Yol. 1., p. 583. 
1878. 
Sappey. Traite d’anatomie descriptive. Bme ed. rev. et amel. 1879. 
Ranyier, L. Traite technique d’histologie. 1879 et seq. 
Klein, E. Quarterly Jour. Mic. Science. No. LX., p. 363. 1875. Also, Atlas of 
Histology. Par. XIII. 1880. 
Frey. Histology. 1880. 
The Pancreas. 
Pfluger, E. F. W. Strieker’s Manual of Histology. 1878. 
Renaut, J. Sur les organes lympho-glandulaires et le pancreas des vertebres. 
Compt. rend. Acad, des Sciences. Yol. LXXXIX., p. 347. Paris, 1879. 
Foster, M. Physiology. 1880. BIBLIOGRAPHY. 
419 
The Thymus Gland. 
Watney, H. Note on the Minute Anatomy of the Thymus. Proc. Roy. Soc., Yol. 
XXVII., p. 369. London, 1878. 
AfaNASSIEN. Structure of Thymus. Archiv fur mikroskopische Anatomie, Band 
XIV., Heft 134. 
The Thyroid Body. 
Boechat, P. A. Thesis on the Structure of the Thyroid Gland. 1873. 
Baber, E. Oreswell. Researches on the Minute Structure of the Thyroid Gland. 
Philosophical Transactions Lond. Roy Soc., Vol. CLXVL, Pt. 3, p. 557. 1876. 
Proc. Royal Soc., Vol. XXVII., p. 56. London, 1878. 
Zeiss Otto. Mikroskopische Untersuchungen iiber den Ban der Schilddrlise. Strass- 
burg, 1877. 
Poincare, M. Contribution a I’histoire du corps thyroide. Jour, de I’anatomie, 
Klein, E. Atlas of Histology. Par. XIII. 1880. 
p. 133. 1877. 
Journal de medecine, de chirurgie et de pharmacologic de Bruxelles, Vol. LXIX., 
p. 805. 1880. 
The Pituitary Body. 
Klein, E. Atlas of Histology. Par. XIII. 1880. CHAPTER, XXVI. 
THE THICK CUTIS YEEA. 
J. COLLINS WARREN, M.D. 
The portions of the skin usually selected for histological 
purposes are those in which the papillae or hairs are best shown. 
The glands are also carefully described ; but little attention, 
however, has been given to the anatomy of the cutis vera as an 
organ by itself, consequently those parts have not been ex- 
amined where it is found in its most highly developed form. 
The skin varies greatly in thickness; on the inside of the 
arms and thighs, and on the anterior aspect of the body gen- 
erally, it is much thinner than behind. In the former case, 
particularly in delicate women, it is exceedingly soft and plia- 
ble, a thin fold being easily raised and rolled between the 
thumb and finger. In the latter it is exceedingly thick in the 
back and shoulders of hardy adults, appearing as a veritable 
hide, being much thicker than the skin of many pachyderma- 
tous animals. Here it measures 5.5 mm. and even more in 
thickness ; when tanned it resembles sole leather. This struc- 
ture is composed of bundles of fibres interwoven in various di- 
rections. On the surface of these bundles lie the flat connective- 
tissue cells, disposed in rows and occupying the intervals, the 
tissue being somewhat analagous to tendon. The cutis is, in 
fact, a sort of tendon or aponeurosis ; from its under surface 
it sends out fibrous prolongations of considerable size, and in 
some animals these are actually attached to muscles.1 In man 
we find them dipping down into the subcutaneous fat, in the 
back forming a very dense and firm mesh-work. Fatty tumors 
IM. Renaut: Anatomie generale de la peau; Annales de Dermatologie et de 
Syphilographie ; Tome neuvieme, No. 5 ; Satterthwaite : New York Medical Jonrna1, 
July, 1875. 421 
THE THICK CUTIS YEEA. 
growing in this part of the panniculus adiposns are, for this 
reason, extremely difficult to enucleate. 
The papillae are but imperfectly formed, and are represented 
by an undulating line. At short intervals are the follicles of 
the lanugo hairs, which penetrate only the superficial layers of 
the cutis, the sweep of whose fibres would be otherwise un- 
broken were it not for the 
existence of a structure, 
hitherto undescribed,1 which 
connects the bases of the 
hair-follicle with those parts 
in which we find the root of 
the longer hairs imbedded 
—the panniculus adiposus. 
This consists of a nearly 
vertical cleft, or slender col- 
umnar-shaped space, ex- 
tending from the last-named 
structure in a somewhat ob- 
lique direction through the 
deeper and middle layers of 
the cutis, and terminating 
, ,-I i » ,i -Pn'l 
at me Dase or me lOlllCle 
-1 . •> , . , m-i . 
wliicn rests upon it. Tins 
. . -i • 
space is occupied by adipose 
Fig. 179.—Section of skin from back of an adult, 
showing columna adiposa and lanugo hair. Magnified 
about eight diameters : «. epidermis: &, erector pili mus- 
cle ; d.fat column ;e, sudoriparous gland ;f, cutis vera; g, 
adipose tissue; /i, hair; k, cdne fibreux ; p, lateral cleft. 
tissue in its entire length ; hence, the term “fat-columns,” or 
“ fat-canals,”2 would seem to be an appropriate name. 
The length of this space (in very lean individuals the fat is 
absent, and we then see a delicate mesh-work of connective tissue, 
and the trunk of a blood-vessel) is about 4 mm. ; its width 
rather exceeds that of the hair-follicle above. Its long axis is 
placed at a slight angle to that of the follicle, which in most 
cases is nearly perpendicular to the surface, and is nearly 
parallel to that of the erector pili muscle (5). At about the 
middle of this axis are given off two horizontal prolongations, 
usually partially filled with fat-tissue, appearing like a pair of 
lln the latest treatises of the skin, no such structure is described. See Die Haut- 
krankheiten fur Aerzte und Studirende von Dr. Gustav Behrend. Berlin, 1879; Patho- 
logic und Therapie der Hautkrankheiten von Dr. Moriz Kaposi. Wien, 1879. 
2 Xote on the Anatomy and Pathology of the Skin, by J. C. Warren. Boston Medi- 
cal and Surgical Journal, April 19, 1877. 422 
MANUAL OF HISTOLOGY. 
extended arms, or the remaining branches of a leafless trunk (p). 
Near this point is suspended the coil of a sweat-gland {e\ held 
in place by a few delicate fibres which find their insertion at 
the top of the canal or cleft. The duct of the gland runs to the 
top of this space, whence it may be traced to the side of the 
hair-follicle, whence it finds its way to the surface. (In dogs 
the sweat-duct opens directly into the follicle, a short distance 
from its mouth.) The fibres of the cutis appear, in vertical sec- 
tions, to terminate abruptly at its edges. There does not ap- 
pear to be any structure resembling a “limiting membrane.” 
At its base there is sometimes a slight widening of the cleft, 
and on the side toward which its axis leans, the fibres of the 
cutis collect to form a bundle which penetrates the subcutane- 
ous fat (Cone fibreux de la 
peau—k, Fig. 179). The upper 
extremity is rounded off in 
somewhat dome-shape. 
The erector pili muscle, tak- 
ing its origin from the papillary 
layer of the cutis, is inserted 
partly into the base of the fol- 
licle, which its fibres embrace, 
and partly into the apex of the 
fat-canal; in some sections the 
fibres seem to penetrate this 
space, but probably surround 
it, although some of them may 
be attached to those delicate 
Pig. 180.—Section of skin from the shoulder of 
an infant, magnified seventeen diameters: a, epi- 
dermis ; 6, erector pili muscle; c, sebaceous gland ; 
d, fat-column; e, sudoriparous gland; a, adipose 
tissue; h, hair. 
bands of fibrous tissue which traverse the column of fat-cells. 
The muscle lies on-the side corresponding with the inclination 
of the hair externally, and appears almost continuous in its 
direction with the fat-column beneath it. 
The sebaceous gland lies between the muscle and the follicle 
at the apex of the angle made by them ; a lobe is found also 
on the opposite side. 
The number of these columns corresponds to the number of 
hairs, as they are not found elsewhere. In some sections of 
skin, half an inch in length, as many as five may be counted ; 
they are seen to best advantage in the thickest portions of the 
skin, but may be found on the shoulders and arms, breast, ab- 
domen, and lower extremities. At some points they appear THE THICK CUTIS YEEA. 
423 
as slight indentations in the section ; at others as long canals. 
They are well shown in the skin of an infant (Figure 180), and 
in a foetus of nine months. In the pig, the lower border of the 
cutis appears to the naked eye, when seen in section, like the 
teeth of a saw. Under the microscope, the apex of each inden- 
tation contains the bulb of a hair. In thick hides these inden- 
tations become clefts or canals, and we find frequently a 
sweat-gland situated at about the middle of each. The canals 
are oblique, as are also the hair-follicles, and the axes of the 
two are more nearly parallel than those in the human subject. 
In thin skins the canals are either so short as hardly to pass 
for such, or, if the hair is not of sufficient length to extend to 
the bottom of the cutis, absent. A thick skin and the ex- 
istence of downy hairs are, then, the conditions necessary for 
the presence of this structure in its most marked forms. I have 
not found them in the face, although in some individuals they 
probably exist there, nor in the thinner skin already alluded to. 
In the lip of the rat the long hairs are imbedded in a transpa- 
rent, mucous-like connective tissue, and their roots are sur- 
rounded by numerous bands of muscle. It is interesting to 
note the fact, that under each root are to be found vertical rows 
of fat-cells, arranged end on end like the beads of a rosary, but 
there appears to be no cleft in the surrounding tissue to en- 
close them. In order to obtain a preparation of skin which 
shows these structures in their entire length, the section must 
be made vertical to the surface, and in a direction which corre- 
sponds with the inclination of the cleft of the hair above the 
surface. This coincides with the fine folds or “grain” of the 
skin. Sections made in any other direction give but a frag- 
ment of the canal, which appears then nearly as an isolated 
lobule of adipose tissue. Even with these precautions it is 
difficult to obtain a good specimen, unless the razor is guided 
by the eye and, as in embryonic skin, the canals are not large 
enough to be seen, it is greatly a question of luck whether a 
good section can be obtained. 
The blood-vessels are well shown by an injection of Berlin 
blue in the foetus near full term. In each canal, as well as in 
the intervals between them, the arterioles which nourish the 
cutis ascend from the subcutaneous system of vessels, which 
forms a fine net-work in the panniculus adiposus. Those in 
the canals, on reaching the lateral clefts, bifurcate, giving a 424 
MANUAL OF HISTOLOGY. 
branch on either side, which anastomoses sparingly through 
subdivisions with the adjacent arterioles in the middle layer of 
the cutis, and give origin to the papillary and sub-papillary 
network of capillaries, which here can be considered as one 
and the same. At the point of bifurcation of the main vessel, 
branches are given off which ascend farther in the canal and 
form a delicate net-work surrounding the sudoriparous gland 
(“ Wundernetz ”), The anastomosis of the vessel about the 
hair-follicle is particularly rich and line, and unites intimately 
with the superficial layer of capillaries. The hair-follicle, with 
its subjacent fat-column, thus forms the centre of a rich system 
of arterioles and capillaries, which extend from the panniculus 
adiposus to the papillae. 
The lymphatics.—The following experiments were made to 
determine the question of the presence of lymphatics in these 
canals, and also to observe to what extent fluids and particles, 
pressed up from below, could be forced to the surface. 
Skin was taken from the body of a lean adult, twenty-four hours after death. 
A small amount of the loose areolar tissue was left adherent to its lower sur- 
face. The skin being prepared by warming for a few minutes in water of 
about 90° P., Berlin blue was injected, by means of a subcutaneous syringe, 
into the loose areolar tissue, which was rapidly distended by the fluid. The 
specimen was then thrown into strong alcohol, A similar fragment of skin 
was stretched like a drum, over the end of a brass cylinder, to which it wTas 
firmly attached by an open brass cap and screws. The cylinder being held 
vertically, Berlin blue was poured upon the skin, the upper surface of which 
looked downward. A rubber cork, perforated by a glass tube, was securely 
fastened to the top of the cylinder, and the tube was connected with an appa- 
ratus designed to exert any atmospheric pressure required. Pressure sufficient 
to raise a column of mercury twenty-eight millimetres was continued for an 
hour and a half, the skin being pressed out with great force in dome-shape 
at the bottom of the cylinder, which was kept during this time in blood-warm 
water. The specimen was then placed in alcohol. It was observed that the 
injection mass had gone, at one or two points, to the surface, and on making- 
vertical sections of the skin the next day, the cutis was found to be penetrated 
by the mass in vertical blue lines, which united at various intervals by hori- 
zontal branches, occasionally so numerous as to present an almost continuous 
blue surface. The subcutaneous areolar tissue was almost uniformly colored 
blue. 
Opinions on the character and distribution of the lymphat- 
ics of the skin seem to differ. For instance, Neumann de- 
scribes them as vessels distributed through the skin in two THE THICK CUTIS VERA. 
425 
horizontal layers—a superficial and a deep one—the vertical 
connection between the two being found only at comparatively 
rare intervals.1 Renaut regards the skin as a lymphatic sponge, 
the minutest ramification being but the space between the bun- 
dles of fibres ; the coarser differing from these in having an 
endothelial lining (connective-tissue cells?), there being in 
neither case a true wall, which is found only in the lymphatic 
vessels of the subcutaneous tissue.2 Vertical sections taken 
from the specimens of skin injected by puncture, showed a 
similar, but not so complete an injection, as was effected by 
Pig. 181.—Injected lymph-system magnified about eight diameters: a, epidermis ; /, cutis vera; g, 
adipose tissue; h, hair. 
the present method. The latter seems to possess special ad- 
vantage, as a larger lymph surface is exposed at one time. 
Fig. 181 shows the route taken by the Berlin blue, which, as 
will be seen, ascends in nearly vertical columns through the 
fat-canals to the base of the hair-follicles, going round the 
sides of the sweat-gland. When a slight amount only had 
passed into the canal, a medium power of the microscope 
showed the blue lying in and staining the tissue accom- 
panying the ascending blood-vessel in the so-called “ perivas- 
cular space.” The lateral clefts were filled with the mass, 
1 Zur Kenntniss der Lymphgefasse der Haut, von Isidor Neumann. 
2 Renaut. Op. cit. MANUAL OF HISTOLOGY.. 
which extended far enough to communicate with that com- 
ing from an adjacent column. From this point there is a 
delicate and freely anastomosing network, marking out the 
spaces between the bundles of fibres of the cutis. The lateral 
anastomosis, lower down, is not so free, and in the uppermost 
layers, owing probably to the compression of the bundles of 
fibres, there is little blue to be seen. From the top of the canal 
the injection surrounds the base of the hair-follicle, on one side 
ascending vertically and giving oil horizontal branches, and 
on the other following the interval between the lower border of 
the erector pili muscles and the fibres of the cutis. The main 
route is through the canals, there being no penetration from 
below elsewhere. A similar method of injection of these spaces 
is seen in certain forms of disease. A subcutaneous, round- 
celled sarcoma infiltrating the skin, gave a similar configura- 
tion. Also that form of congenital nsevus which develops in 
the panniculus adiposus, and in a few days after birth begins 
to appear on the surface. Another instance is that variety 
of purulent infiltration of the subcutaneous tissue, which is 
most frequently seen under thick skin and known as carbun- 
cle. The wandering cells find their way to the surface through 
these canals, and thus give the characteristic, punched-out 
appearance to the skin. 
It is evident from these examples that a free communication 
exists between the interspaces of the fibrous bundles of the 
cutis, and the subcutaneous tissue, and that this is effected by 
no closed system of vessels. 
The special function of these canals is not so evident. In 
addition to furnishing a, route for the blood-vessels and lym- 
phatics, there would seem to be some connection with the hair 
and its apparatus. The constant relation which they bear to 
this structure, and the erector pili muscle, would suggest an 
arrangement designed to facilitate the action of the muscle, 
according to Biesiadecki.1 This muscle, by its contraction, 
raises the hair from the position which it occupies, nearly hori- 
zontal to the surface, to a vertical one. Any movement of the 
root of a lanugo hair would be well nigh impossible, imbedded 
in the dense tissue of the cutis, were it not for a yielding 
structure like that of the columns, an elongation of which 
1 Strieker’s Handbucb der Lebre von den Geweben des Menscben und der Tbiere. THE THICK CUTIS VERA. 
427 
would aid the contraction of the muscle. In specimens where 
the muscle is found in a state of contraction, the hair-follicle 
is bent like a bow, the root being drawn through the arc of a 
circle. The presence of fat near the hair-bulb is made possible 
by this structure, a condition which is constant with all hairs. 
That the fat is not an incidental feature of their structure, 
which might be considered merely a cleft for the transmission 
of vessels, is rendered probable by the observation of rows of 
fat-cells beneath each hair in the lip of the rat, where no special 
channels exist, and, also, by the fact that such columns of fat 
do not accompany the nutrient vessels of the skin, in those 
parts where the hairs are not found. It seems, therefore, 
probable, that this structure has some bearing upon the nu- 
trition of the hair. 
Sweat-glands are found not only in these canals, but else- 
where in the thick cutis ; the coil of the gland is then usually 
situated at a level a little below the middle of the cutis vera, 
and not in the subcutaneous adipose tissue, as in thin skin. CHAPTER XXYII. 
URINARY EXCRETORY PASSAGES; SUPRARENAL CAPSULES. 
Bt EDMUND C. WENDT, M.D., 
Curator of the St. Luke’s and St. Francis’ Hospitals, etc., New York City. 
The renal pelvis, the calices, ureters, and bladder, all consist 
essentially of three layers, which are an inner mucous mem- 
brane, a middle muscular coat, and an external fibrous layer. 
In the 
RENAL PELVIS 
we find the mucous membrane lined with stratified epithelium, 
the cells of which are large and variously shaped. Three dif- 
ferent forms are readily distinguished. The most superficial 
layer consists of flat or polyhedral cells of various sizes, each 
one containing a round or oval nucleus, or, as frequently hap- 
pens, two nuclei. Peculiar dark granules, often of large size, 
surround the nucleus, and are quite distinct from the finely 
granular protoplasm of these cells. Then comes a layer of 
conical or club-shaped bodies, each one again furnished with 
a round or oval nucleus. Every cell also possesses a long 
basal process, which appears to attach it to the subjacent 
tissue. The bulbous portion of these corpuscles is turned 
outward in the direction of the surface. Wedged in between 
the processes Just mentioned we find the third variety of 
cellular elements. These are oval or rounded bodies contain- 
ing ellipsoid nuclei. At the renal calices we find a sharp line 
of demarcation between the cylindrical columnar epithelium 
of the papillary ducts and the stratified pavement epithelium 
of the pelvis. The epithelial layer has a thickness here of 
0,045-0.09 mm. 
The connective-tissue portion of the mucous membrane is 
devoid of papillae, contains sparse elastic fibres, and is rich in THE URETERS. 
429 
fixed corpuscles, the Inoblasts of Krause. There is no true 
basement-membrane. Below this stratum we find a submu- 
cous layer, which is abundantly furnished with elastic tissue, 
and contains a few simple acinous glands with ducts having a 
lining of cylindrical epithelium. 
The muscular coat is composed of bundles of smooth mus- 
cle-cells forming an inner layer, with a peripheral direction of 
its constituent anatomical elements, and an outer layer concen- 
trically arranged. The “papillary sphincter” is but a thick- 
ening of this latter layer. 
The external fibrous layer forms a thin connective-tissue 
membrane, not always clearly marked here, whereas in the ure- 
ters and bladder it is found to be well developed. 
The blood-vessels of the pelvis are derived from the renal 
artery and vein, and form capillary networks characterized by 
polygonal meshes. The lymphatics and nerves are found to 
have the same distribution as in the ureters. 
THE URETERS 
have a structure which closely resembles that of the renal pel- 
vis. The mucous membrane shows the same varieties of epithe- 
lium ; its connective-tissue components are similarly arranged ; 
and the external investing membrane is composed of the same 
kind of tissue already described. But in addition to the two 
muscular layers, which here attain a greater development, we 
find a third muscle coat, so that we can now distinguish an in- 
ternal and external longitudinal from a middle circular layer 
of muscular elements. 
Engelmann has described a close reticulum of blood capil- 
laries lying immediately under the epithelial stratum, but its 
existence is made doubtful by the negative statements of other 
authors. 
Glandular bodies are not found in the ureters. The peri- 
pheral layer of fibrous connective-tissue possesses conspicuous 
elastic bundles in the lower portion of the ureters. 
The distribution of the blood-vessels is like that of the pel- 
vis already described. The lymphatics are well developed here, 
forming several networks in the different layers of the ducts. 
Nerves are likewise readily distinguished, some of the nerve- 430 
MANUAL OF HISTOLOGY. 
fibres being also furnished with ganglion cells. Their mode of 
termination in the muscular layer is not definitely known, but 
may be assumed to resemble that of ordinary smooth muscu- 
lar-tissue. 
THE BLADDER 
has the same type of structure as the ureters, but contains, in 
addition, a serous covering in its upper portion. The different 
coats of the bladder are, however, much thicker than the cor- 
responding layers in the other urinary excretory passages. 
The epithelial lining of the mucous membrane shows the 
three varieties of its cellular elements in a clearly defined man- 
ner. 
The connective-tissue stratum presents no noteworthy pe 
culiarities, if we ex- 
cept the comparative 
abundance of simple 
acinous glands. 
The bundles of 
muscle-cells in the 
muscular-coat inter- 
lace, forming irregu- 
lar, long-stretched 
meshes. This irregu- 
lar arrangement pre- 
vents the distinct rec- 
ognition of successive 
layers, each with a 
largely prevailing di- 
rection. Nevertheless, 
. Pig. 182.—Epithelium of the urinary bladder, a, a cell of the 
second layer; 6, a cell of the first layer ; c, shows the first, second, 
and third layers of the epithelium in connection. Obersteiner. 
we find in the external portion of the muscle-coat some pre- 
dominance of longitudinal bundles, together with an abundant 
supply of elastic fibres. The anterior wall and vertex of the 
bladder show this arrangement very conspicuously, in fact the 
muscle-fibres have here received a separate name, that of detru- 
sor urines. The vesical neck shows a tolerably distinct thicken- 
ing of its circular muscle-fibres, which is known as the sphincter 
vesiccs. It should always be borne in mind that the arrange- 
ment of the muscular coat is apt to vary in different individuals, 
the description here given will, however, be found to apply to 
the majority of cases. SUPRARENAL CAPSULES. 
431 
The Mood-vessels form a capillary network in the mucous 
membrane, which is situated about midway between the epi- 
thelial stratum and the muscular coat. In other respects they 
present no peculiarity worthy of note. 
The lymphatics are less abundant in the bladder than in 
the ureters. They, also, lack noteworthy peculiarities or 
special features of interest. 
Plexuses of nerve-fibres are found in the subserous connec- 
tive-tissue, and also in the muscular coat. Microscopic ganglia 
and groups of ganglion cells are also met with. 
SUPRARENAL CAPSULES. 
The suprarenal capsules (,glandules suprarenales) are small 
flattened bodies, two in number, situated somewhat above and 
Fig. 183.—Cellular groups and trabeculae o£ the cortical substance, from the suprarenal capsule of the 
Frog. Eberth. 
in front of the upper end of either kidney. They are usually 
triangular or semilunar in shape, although round and oval 
forms are also met with. In structure they resemble the so- MANUAL OE HISTOLOGY. 
called blood-vascular glands, 
They belong to the ductless variety of glands 
but their function is not known. 
Each suprarenal body consists 
of a capsule inclosing the paren- 
chyma, which shows a cortical and 
medullary substance. The cap- 
sule is formed of ordinary connec- 
tive tissue containing many deli- 
cate elastic fibrils. Externally it 
is surrounded by loose connective 
tissue, containing a greater or less 
proportion of adipose tissue, and 
internally it sends out trabeculae, 
which traverse the entire organ, 
thus constituting and completing 
its frame-work. 
The cortical substance, as its 
name implies, occupies the exter- 
nal portion of the suprarenal body. 
It has an average thickness in man 
of 0.28 to 1.13 mm., is of a yellow- 
ish color, and may be divided into 
three layers or zones. The lim- 
its of demarcation between these 
layers are much less marked, 
however, than the corresponding 
boundary line between the corti- 
cal and medullary portions. In 
the human being the external layer 
of the cortex is distinctly separate 
Fig. 184.—Perpendicular section through 
the suprarenal capsule of man :1, cortex; 2, 
medulla; a, capsule; 6, layer of outer cell- 
groups ; c, layer of cell-trabeculas (zona fasci- 
culata); <l, layer of inner cell-groups ; e. med- 
ullary substance; /, transverse section of a 
vein. Eberth. 
from the middle one, but the latter shows no such sharp limit 
against the innermost layer. 
The cortex is a friable substance, 
and its broken surface presents 
a striated appearance. Owing to 
rapid post-mortem changes, the 
cortex in man is usually found 
to be separated from the medul- 
lary portion by a dirty brownish 
substance, containing modified 
blood and cortical corpuscles. 
Fig. 185.—Single cells and cell-groups of the 
outermost cortical layer. Human suprarenal cap- 
sule. Eberth. 433 
SUPRARENAL CAPSULES. 
Tlie three layers of the cortex are an external one, or zona 
glomerulosa; a middle one, or zona fasciculata; and an in- 
ternal one, or zona reticularis. 
The external layer consists of rounded or oval groups of 
cells, separated by delicate connective-tissue trabeculae, which 
spring from the capsule. Similar cells are found throughout 
the entire cortex. They have been called the parenchymatous 
bodies or cells, although a better name is cortex corpuscles. 
In structure they resemble ordinary cells, consisting of poly- 
Fig. 186.—Horizontal section through the outermost cortical portions of the suprarenal capsule of the 
Horse, a, blind termination of a cylinder; 6, groove-shaped and cylindrical cortical trabectilae; c, stroma. 
Eberth. 
hedral masses of protoplasm furnished with spherical nuclei 
and conspicuous nucleoli. Their protoplasm has a coarsely 
granular character, and, as a rule, contains more or less fat in 
greater or smaller droplets. 
The middle layer contains cortical corpuscles which are ar- 
ranged in almost parallel rows, and are so closely packed that 
this portion acquires a distinctly striated appearance. These 
cellular columns have received various names. By Ecker they 
were called gland tubules, Kolliker termed them cortical cylin- 434 
MANUAL OF HISTOLOGY. 
ders, Ebertli described tliem as cylindrical cell-trabeculae, or 
cortical trabeculae, and Krause named them cellular pillars. 
These cellular rows, columns, or streaks, are by no means 
always cylindrical, for on cross-section they frequently present 
a semilunar, oval, or bean-shaped appearance. Their inner 
and outer terminations have a rounded shape, and near the 
former place they seem to anastomose with one another. At 
Fig. 187.—Vertical section through the the cortical portion of the suprarenal capsule of the Horse, a, 
capsule; &, cell-trabecuhe; c, cell-groups. Eberth, 
the peripheral end they sometimes appear groove-shaped, or 
in horse-shoe form. 
Connective-tissue processes communicating with the cap- 
sule are found between the cell columns, but the latter are not 
completely isolated by them. These connective-tissue streaks *• 
also send off transverse or oblique fibres, so that occasionally 
the cells of the middle layer seem to be inclosed in basket-like 
meshes. In addition to fat-droplets, granules of pigment are SUPRARENAL CAPSULES. 
435 
found in the cells of the innermost portion of the middle 
layer. 
The internal layer is made up of irregularly arranged cor- 
tical corpuscles. Nearly all the cells of this layer contain 
pigment granules. The connective-tissue here forms a reti- 
culum, with variously shaped meshes, which contain greater 
or smaller heaps of cells. 
The medullary substance has a whitish-gray appearance, and 
is of a more delicate consistency than the cortex. It consists 
Fig. 188.—Vertical section through the medullary substance of the suprarenal capsule of the Cow. 
a, blood-vessels; b, trabecul® of medullary cells. Bberth. 
of a network of connective tissue, which contains in its meshes 
the medullary corpuscles. These are pale cells with spherical 
nuclei and large nucleoli. They may assume various shapes. 
In man they are generally of an irregularly stellate or polyg- 
onal form. Their protoplasm is finely granular, and they con- 
tain, as a rule, much less fat and pigment than the cortical 
corpuscles. Kolliker finds that they resemble the nerve-cells 
of the central nervous system, but he adds that they cannot 
be regarded as such nerve-elements. The medullary cells 
assume a yellow or brownish color when treated with chromate 
of potash ‘or chromic acid. Since the cortex corpuscles are \ 
not thus colored, this peculiarity may serve to distinguish one 
cellular variety from the other. 
The connective-tissue framework of the medulla is called its 436 
MANUAL OF HISTOLOGY. 
stroma, and its meshes in man have an oval or rounded form, 
so that, as a rule, the cell-groups have a similar shape. On the 
whole, we find a smaller proportion of connective tissue in the 
medulla than in the cortex. 
The blood-vessels of the suprarenal capsules occupy the 
stroma, and are found in great abundance. The arterial vessels 
arise from the aorta, the phrenic and renal arteries, and the 
coeliac axis. About twenty small branches pierce the capsule, 
and are distributed mainly to the cortex. The medullary sub- 
stance is very rich in venous plexuses. Capillary networks 
are found in both cortical and medullary portions. The veins 
uniting form one principal branch, which passes out at the hi- 
lus of the organ. The right suprarenal vein empties its blood 
into the vena cava inferior, the left one into the vena renalis 
sinistra. 
Lymphatics were seen by most observers only at the sur- 
face of the suprarenal capsules. Klein, however, has recently 
asserted that there exists between the cells “an anastomosing 
system of narrower and broader clefts, channels, and lacunm, 
which belong to the lymphatic system.” This applies to the 
zona fasciculata. In the other portions of the organ the same 
writer also finds lymph-spaces, and lymph-sinuses, occupying 
the regions “between the septa and trabeculae of the frame- 
work on the one hand, and the cell-groups on the other.” 
The nerves occur in comparatively greater abundance in 
these organs than in any other glandular structures of the hu- 
man body. Kolliker was able to count thirty-three branches 
in a single suprarenal capsule of a man. They are derived 
from the renal plexus, the pneumogastric and phrenic nerves, 
and semilunar ganglion. Very fine or medium-sized, dark-bor- 
dered fibres are commonly encountered, and they abound espe- 
cially in the medulla. Ganglion-cells are also frequently seen, 
and Virchow has traced them into the interior of the organ. In 
the cortical substances they are of rare occurrence. The terminal 
distribution of the nerves has not been hitherto ascertained, 
and it appears to be still a matter of doubt whether they ter- 
minate in the suprarenal body at all. 
Development.—ln mammals the suprarenal capsule has an 
independent origin in a collection of tissue between the Wolff- 
ian bodies behind the mesentery and in front of the abdomi- 
nal aorta. (Kolliker.) The mesoderma at this point assumes 437 
BIBLIOGRAPHY. 
a special structure. Certain of its cells form more or less cyl- 
indrical masses with a reticulated appearance. Between these 
cellular groups a network of blood-vessels is soon found, so 
that the whole structure is now not unlike embryonal hepatic 
tissue. In rabbits, Kolliker saw the first traces of these bodies 
about the twelfth or thirteenth day. On the sixteenth day 
they had already attained a length of 1.56 mm., and occupied 
a position along the vertebral column from the first to the fourth 
and part of the fifth lumbar vertebra. On cross sections of em- 
bryos sixteen days old, Kolliker found that the suprarenal cap- 
sules were distinctly separate at their upper borders, whereas 
their lower ends were joined together to form a single organ. 
The same writer also found a nervous ganglion at the coalesced 
central portions of somewhat older embryos. 
Behind the suprarenal capsules a second sympathetic 
ganglion was discovered. Bemak and v. Brunn do not in all 
respects corroborate the statements of Kolliker. The latter 
was unable to ascertain any existing relationship between the 
nervous system and the suprarenal capsules. 
BIBLIOGRAPHY. 
Bergmann. Be glandulis suprarenalibus. Biss, inaug. Gottingen, 1839. 
Ecker. Ber feinere Ban der Nebennieren beim Menschen und den vier Wirbelthier- 
klassen, 1846. Article “ Blutgefiissdriisen ”in Wagner’s Handworterbuch der 
Physiologie, Bd. IV. 1849. 
H. Frey. Art. “ Suprarenal Capsules” in Todd’s Cyclopaedia of Anat. 1849. 
Remak. Untersucbungen ueber der Entwickelung d. Wirbelthiere. Berlin, 1853- 
Virchow. Zur Cbemie der Nebennieren. Virchow’s Archiv, 1857. 
Leydig. Lehrbuch der Histologie, 1857. 
B. Werner. Be capsulis supraren. Borpat Bissertatio. 1857. 
Vulpian. Gaz. med., p. 659. 1856; p. 84, 1857. Gaz. hebd., p. 665, 1857. 
G. Harley. The Histology of the Suprarenal Capsules. Lancet, June sth and 
12th, 1858. 
Barkow. Anat. Enters, ueber die Harnblase. 1858. 
Palladino. Estratto del bulletino dell’ ass d. nature med. Anno 1., No. 5. 
Napoli. 
Burckhardt. Virchow’s Arch., Vol. XVII., p. 94. 1859. 
G. Joesten. Archiv fur phys. Heilkunde, S. 97. 1864. 
A. Moers. Virchow’s Archiv, Bd. XXIX., S. 336. 
Henle. Anatomic des Menschen. Bd. 2. 1866. 438 
MANUAL OF HISTOLOGY. 
Arnold, Jul, Ein Beitrag zu der feineren Structur und dem Chemismus der Ne- 
bennieren. Virchow’s Archiv, Bd. 85, S. 64. 1866. 
Holm. Ueber die nervosen Elemente in den Nebennieren. Sitzungsberichte der 
Wiener Akademie. Ed. 58, 1. Abtheilung. 1866. 
Grandry. Structure de la capsule surrenale. Journal de I’anatomie et de la physi- 
ologie. 1867. 
Kolliker. Handbuch der Gewebelehre. 5. Aufl. 1867. 
Eberth. Strieker’s Archiv. 
Kisseleff. Centralblatt, No. 23. 1868. 
Botjyin. Over der bouw en de beweging der Ureteres. Utrecht, 1869. 
Engelmann. Zur Phys. d. Ureters. Pfliiger’s Arch., Yol. 11., p. 243. 1869. 
Obersteiner, in Strieker’s Manual. 
Unruh. Archiv f. Heilkunde, p. 289. 1873. 
v. Brtjnn. Archiv f. mikr. Anat., Yol. VIII., p. 618. 1873. 
Egli. Arch. f. mikros. Anat., Yol. IX., p. 653. 1873. 
Hamburger. Zur Histol. d. Nierenb. u. d. Harnleiter. Arch. f. mikr. Anat., 
Yol. XVII., p. 14. 1879. 
See also the text-books of Frey, Krause, Kolliker, and Henle. 
Braun. Ueber Bau u. Entw. der Nebennieren bei Reptilien. Zool. Anzeiger, Yol. 
11., No. 27, p. 238. 1879; und Arbeiten aus d. zool.-zootom. Institut in 
Wurzburg, Yol. V., p. 1. 1879. 
Kolliker. Entwickelungsgeschichte des Menschen. Leipzig, 1879. 
Klein, and S. Noble Smith. Atlas of Histology. 1880. CHAPTER XXYIIL 
THE MAMMARY GLAND. 
BzW. H. PORTER, M.D., and EDMUND C. WENDT, M.D., of New York City. 
General considerations.—By virtue of its intimate associa- 
tion with the function of reproduction, this organ occupies a 
distinctly peculiar position among the glands of the body. In 
the male it persists through life in the same rudimentary form 
which characterizes the mamma of both sexes at birth. Only 
in the female, and in her only at certain times, does this organ 
attain its complete histological maturity. It may be borne in 
mind, however, that in a few anomalous cases, male beings sup- 
plied with fully developed mammary glands have been ob- 
served. 
After conception, and as pregnancy advances, progressive 
evolution takes place within the mamma. This unfolding 
process at length culminates in exaggerated tissue-metamor- 
phosis, which in other organs we should scarcely hesitate to 
call pathological. In fact, Virchow and his followers all main- 
tain that the secretion of milk is the direct result of a fatty 
degeneration of mammary epithelium, and similar in all essential 
respects to the processes involved in the elaboration of the seba- 
ceous material from the cutaneous glands of that name. Bill- 
roth, indeed, calls the mamma? cutaneous fat-glands [Hautfett- 
druseri), and he does this in consideration of the mode of their 
development, and because they are placed immediately be- 
neath the integument. In spite of these statements, however, 
we must maintain that the mamma? are radically different from 
ordinary sebaceous glands, and that the processes of secretion 
in the two sets of glands are quite distinct. The grounds on 
which we base this opinion will be amplified farther on. The 
secretory activity of the gland, consisting in the elaboration 
of milk, is, as a rule, called into play only during the period 440 
MANUAL OF HISTOLOGY. 
of rapid growth and development already alluded to. In ex- 
ceptional instances, however, lacteal fluid may be secreted 
during the extra-puerperal period. 
The mammae belong to the class of compound acinous or race- 
mose glands, and, like the other organs of this group, consist of 
a framework or stroma, and a proper secreting structure or 
parenchyma. As they appear to the naked eye, the bulk of 
the breasts is not their secreting parenchyma, but ordinary 
adipose tissue. This Alls out the intervals between the lobes 
and lobules, and gives to the entire 
organ its smooth, round form. The 
different lobes have separate secretory 
ducts, which open upon the nipple. 
These ducts ramify throughout the 
substance of the gland tissue, and 
ultimately carry upon their terminal 
branches the clusters of secreting vesi- 
cles, called acini or alveoli. Accord- 
ing to Zocher and Hen nig, the true 
glandular substance has not a rounded 
shape, but shows a grouping into three 
principal divisions, one of which ex- 
Flo. 189.—Terminal vesicles and 
stroma from the gland of a nursing 
woman. Langer. 
tends far up in the direction of the axilla. It is separated 
from the axillary lymphatic glands only by a small amount of 
adipose tissue. This would explain the ease, readiness, and 
frequency with which these glands become implicated in ma- 
lignant disease of the mamma. 
Since the glands at birth differ very widely from the mammte 
of adult women, and still more widely from those of pregnancy, 
it will be convenient to consider the histology of the organ under 
different aspects. This will be necessary, however, only with 
regard to the acini and the epithelia therein implanted, as these 
alone show such wide morphological divergencies in the dif- 
ferent phases of existence. 
The nipple (teat, mamilla, papilla mamma) is the one struc*- 
ture belonging to the mamma which is least liable to modifica- 
tions of tissue due to age and sex. It generally assumes the 
shape of a pigmented conical or cylindrical projection, at the 
apex of which the galactophorous ducts have their terminal 
openings. It is composed principally of a rather loosely woven 
connective tissue, containing abundant corpuscles, and provided THE MAMMARY GLAND. 
441 
with elastic fibrils. This conjunctive tissue forms a supporting 
framework for the milk-ducts traversing the nipple. The latter 
show walls of rather dense fibrous tissue, with a large pro- 
portion of elastic elements, and are provided with a lining 
of one row of short cylindrical cells. As the external orifice 
is approached, these cells begin to take on the character 
of the ordinary epidermic corpuscles of the integument. 
Partsch has found in many animals that the secreting paren- 
chyma accompanied these ducts almost to their mamillary 
orifices. 
The occurrence of unstriped muscle in the nipple, accords 
with the fact of its erectile properties. But the exact mode of 
distribution of these elements is still a matter of controversy 
among histologists. From the researches of Winkler and 
Kolessnikow, recently confirmed by Partsch, it would appear 
that they occur not in the ducts themselves, but form an in- 
complete ring around and external to the same. In or around 
the smaller galactophorous ducts, muscle-cells cannot be unmis- 
takably recognized, though some authors have described their 
occurrence there. 
As regards the structure of these smaller galactophorous 
ducts {ductus lactiferi, milk-ducts) it is quite simple. Their 
membranous walls consist of a delicate and closely woven 
reticulum of connective tissue, with a large admixture of fine 
elastic fibres. Henle, Meckel, and Kolessnikow have described 
smooth muscle-cells in these canals, but, as already stated, 
Partsch and others have denied their existence. At any rate, 
on cross-sections the contracted condition of some of the larger 
ducts results in a stellate appearance of their lumina, whereas 
the smaller ducts always appear round or oval. 
The larger ducts traced into the gland tissue are found to 
be provided with saccular dilatations immediately beneath the 
nipple. These milk-reservoirs {sinus ductuum lactiferorum, 
sacculi lactiferi, or ampulla') may be sto 8 mm. broad, and thus 
become distinctly perceptible to the naked eye. Below these 
dilatations the ducts again grow narrower, and by numerous 
divisions and subdivisions form a system of ramifying tubes, 
which terminate in the secreting alveoli. The structure of the 
larger ducts does not materially differ from that of the smaller 
ones. Their walls are, of course, considerably thicker, and 
there is found in addition a greater proportion of elastic tis- 442 
MANUAL OF HISTOLOGY. 
sue. All the different kinds of ducts show a lining composed 
of a single layer of short cylindrical cells, containing ellipsoid 
nuclei. The character of the lining cells is, however, gradually 
changed as the acini are approached, near which it merges into 
the alveolar epithelium by insensible gradations. 
Surrounding the nipple is a variously pigmented ring, called 
the areola mammae. Its surface is slightly corrugated, and 
this circumstance, taken in connection with its pigmentation, 
results in the production of the marked contrast it presents to 
the very white and soft integument covering the other portions 
of the female mamma. The areola is also provided with abun- 
dant unstriped muscle-fibres. Some of the latter surround the 
nipple in concentric rings, others pursue a radial course. The 
sudoriferous and sebaceous glands of the areola are conspic- 
uously developed, and lanugo hairs are also found. The fa- 
miliar changes which go on in the areola simultaneously with 
the development of pregnancy, are mainly due to increased 
blood-supply and additional pigmentation. The areola is also 
provided with small granules of secreting parenchyma. Some 
of these grains empty the products of their secretory activity 
by special recurrent ducts into the main excretory canals. But 
there are others which have special openings upon the free sur- 
face of the areola. Usually, little papillary eminences mark 
the presence of such orifices. These scattered bits of mam- 
mary parenchyma are known as the glandules aberrantes of 
Montgomery. Kolliker and others regard them as largely 
developed sebaceous glands. 
The arteries of the mamma are chiefly derived from the 
internal mammary artery and the long thoracic. The veins 
empty into the thoracic branches and cephalic vein. Both 
arterial and venous vessels proceed subcutaneously from the 
periphery to the nipple, whence branches are given off in a 
posterior direction. They are not guided in their course by 
the distribution of the milk-ducts, but are distributed to the 
glandular parenchyma in such a way that each lobule has its 
own separate supply. Finally, under the areola the veins of 
the nipple form a circular anastomosing chain, known as the 
circulus venosus of Haller. Capillary vessels surround the 
acini, forming networks with rather close meshes. Of course, 
the varying states of expansion and contraction in the ultimate 
alveoli, which conditions correspond to phases of activity and THE MAMMAEY GLAXO. 
443 
rest, will materially affect the size and shape of the capillary 
networks. They are, however, much less distinct and con- 
spicuous during the period of lactation than in the quiescent 
state of the gland. Rauber found in the glands of pregnant 
animals that the blood-vessels were not in immediate contact 
with the walls of the secreting vesicles, being separated from 
them by interposed lymph-channels. Coyne, Langhans, and 
Kolessnikow have also described these perialveolar lymph- 
spaces. Their presence is, indeed, readily demonstrated by 
injections with nitrate of silver solutions. In actively secreting 
glands these channels are sometimes packed with leucocytes, 
which also infiltrate the stroma of the organ. 
Lymphatics are plentiful in the mammary gland. We find 
them subcutaneously, as well as deep in the interior of the 
organ. Coyne, in 1874, described the perialveolar lymph- 
spaces, already mentioned, for the human mamma, and Koless- 
nikow, in 1870, perialveolar lymph-spaces for the mammary 
gland of the cow. Langhans succeeded in injecting a rich net- 
work of periacinal lymph-vessels, likewise lymph-channels 
around the excretory ducts and the lacteal sinuses. The lar- 
gest lymph-vessels are retro-glandular. They are without 
valves. The lymph-vessels of the nipple resemble those of 
the skin. There seems to be no free communication between 
the lacunal and interstitial spaces of connective tissue of the 
glands, and the proper lymph-channels. 
The principal lymph-vessels of the mamma, both deep and 
superficial branches, proceed to the glands of the axilla. But 
some of the mammary lymphatics also communicate, through 
intercostal branches, with the thoracic lymphatic glands. 
These are points worthy of remembrance in studying the mode 
of dissemination in mammary tumors. 
Nerves abound less in the secreting structure of the mam- 
ma than in its integumentary apparatus. The majority are of 
spinal origin, although the sympathetic system is by no means 
excluded from representation. Branches from the fourth, 
fifth, and sixth intercostal nerves—the so-called rami glandu- 
lar es—accompany the milk-ducts, and ramify within the organ. 
Satisfactory evidence concerning the manner of their ultimate 
termination has, however, not been hitherto obtained. Most 
of the nerves in the interior of the organ belong to the vascular 
or vaso-motor variety, and many are seen to accompany the 444 
MANUAL OF HISTOLOGY. 
blood-vessels. Eckliard has given the most elaborate descrip- 
tion of the nerve-sup ply of the human mamma. 
Structure of fully expanded gland.—lmmediately before, 
during, and after lactation, the mamma appears as a distinctly 
lobulated organ, having a pinkish or yellowish hue, and resem- 
bling in consistence the human pancreas or salivary gland. 
The different lobuli are made up of numerous ultimate 
acini, having, as a rule, a rounded, pyriform, or slightly poly- 
hedral shape. They are of nearly uni- 
form size, and are closely placed, being 
separated from one another by only 
sparing amounts of connective tissue, 
and the capillary vascular channels 
therein contained. Elastic fibres and 
smooth muscle-cells also occur, though 
not constantly, between the alveoli of 
the lobules. Lymphoid elements, as 
well as branched connective-tissue cor- 
puscles, are always encountered there 
in greater or less abundance. In addi- 
tion to these elements, large granular 
corpuscles containing nuclei are found. 
They are most numerous along the 
course of the blood-vessels, and appear 
Pig. 190. Transverse section 
through the terminal vesicles of the 
gland in a nursing woman, showing 
interalveolar capillaries. Langer. 
to be identical with the so-called plasma cells of Waldeyer. 
Creighton, however, also describes similar cells in the interior 
of the alveoli, and believes that both are identical, maintain- 
ing that they are derived from the acinous epithelium. 
According to this author’s description, such cells are “ not 
infrequently seen in the tissue outside a lobule in rows three 
or four deep ; again, they are found in the interfascicular spaces 
among the lymphoid-cells,” that have been already mentioned. 
These large, granular, and nucleated corpuscles are said to be 
filled with a bright yellow or golden pigment. Now, Creighton 
has pointed out that the periodical subsidence of the mammary 
function is accompanied by the formation of much corpuscular 
waste material. And the production of these remarkable yel- 
low cells, which finally leave the gland by way of the lymph- 
vessels, is, according to him, but a final phase of this process. 
The mammary epithelium which paves the acini has been 
variously described as consisting of flat polyhedral (Reinhard); THE MAMMARY GLAND. 
445 
cubical, cylindrical (Kolessnikow); small polyhedral (Langer); 
and prismatic (Kehrer) cells. This discrepancy of opinion re- 
ceives its explanation from the fact that the epithelial cells 
Fig. 191.-—Lobule of a mamma near the resting state. Numerous large pigmented cells within the 
acini aiid in the interlobular fibrillar tissue. Creighton. 
have a different appearance in the various conditions interven- 
ing between full activity and complete rest of the gland. 
Creighton has given a very satisfactory description of mam- 
mary epithelium. He states that in the fully expanded gland 
“ the floor of an acinus in section is covered by a mosaic of 
polyhedric epithelial cells, usually to the number of fifteen 
or twenty, while in the larger elongated 
acini as many as thirty may be counted. 
The cells are usually pentagonal or hex- 
agonal, and the corners are sometimes 
rounded. In each cell there is a central 
round nucleus, which colors brightly 
with the staining fluid, and a broad fringe 
of protoplasm, which stains less deeply.” 
The nucleus varies in its relative size, 
generally having a diameter equal to 
about one-third that of the entire cell. 
Fig. 192.—Fully expanded aci- 
nus, showing mosaic of polyhedral 
cells. Creighton. 
“In a profile view of an acinus, the epithelium appears as a 
circlet of oblong cells, in which the nucleus at the centre occu- 
pies almost the entire thickness of the cell. The mammary 
epithelial cell may therefore be described as a flattened poly- 
hedric body, with a thickness about one-half of its breadth. 
The substance of the nucleus is apparently homogeneous, with 446 
MANUAL OF HISTOLOGY. 
a deeper line of staining round the margin ; a nucleolus is not 
always prominently seen.” 
Structure of involuted mamma.—Having thus briefly indi- 
cated the main histological features of a fully evolved gland, 
we are now prepared to examine the mamma in a condition of 
advanced involution. By involution, in this sense, is meant 
the periodical return to inactivity, and not to final retrograde 
metamorphosis, which culminates in complete senile atrophy. 
The glandular lobules, then, in the involuted organ are again 
found to be composed of closely crowded alveoli. But all the 
lobules appear to have become smaller, and 
their acinous components are likewise shrunk- 
en. The basement-membrane of the latter 
does not appear to be materially altered, but 
its cellular contents are considerably changed. 
In place of the beautiful mosaic characteristic 
of the active gland, there now appears only 
an aggregation of nucleated corpuscles to the 
number of five or ten. Creighton describes 
them as “nothing else than a somewhat ir- 
regular heap of naked nuclei, with no fringe 
of protoplasm round them, and in size little, 
if at all, larger than the nucleus alone of the 
perfect epithelium.” This description, how- 
ever, applies only to hardened specimens, for 
in fresh preparations the nuclei, as a rule, 
Fig. 193. Involuted 
mammary lobule, showing 
the nuclear contents of the 
alveoli. Creighton. 
show a broader or narrower surrounding zone of protoplasm. 
As regards the diameter of the involuted acini, it is about one- 
fourth that of the actively secreting alveoli. 
Owing to the shrinkage in the glandular parenchyma, the 
blood-vessels and excretory ducts, as already stated, are more 
prominent in an involuted than in an active gland. 
It is not our purpose here to trace, step by step, the various 
processes by which a gland passes from the resting state to 
that condition of complete evolution which is alone compatible 
with active secretion. For the details of this interesting subject, 
the reader is referred to the work of Creighton, We may, how- 
ever, very briefly summarize this author’s account of the trans- 
formations in question. The one essential circumstance char- 
acterizing the whole change is a process of vacuolation, which 
Creighton assumes to take place in the secreting cells. “The THE MAMMARY GLAND, 
most definite and unmistakable form of vacuolation is the sig- 
net-ring type.” This process is, according to him, a true one 
of endogenous cell formation, resulting in this instance in the 
formation of milk. Moreover, large, granular, nucleated cells, 
filled with a bright yellow or golden pigment, “found both 
within the alveoli and in the interfibrillar spaces without them” 
Pig. 194.—Vacuolation of alveolar epithelium. From the udder of a ewe shortly after the end of lac- 
tation. The cells in situ are vacuolated cells, with the usual thin and. for the most part, uncolored hoop 
or ring of the vacuole, and the deeply stained peripheral mass. Creighton. 
characterize the last stage of involution, “and the pigment 
that belongs to them is to be . found strewn over the lobules 
that have reached the resting state.” Finally, Creighton as- 
serts that “the various forms of cells that characterize the 
various stages of involution must have resulted from a trans- 
formation de now of the renewed epithelium, and not from 
successive changes upon the same cell.” Each epithelial cell, 
therefore, that is used up in the formation of milk, has been at 
one time a perfect polyhedral corpuscle or fully equipped cell, 
and “has rapidly undergone the cycle of changes whereby 
its whole substance has been converted into milk.” 
A distinguishing feature of one stage of evolution which 448 
MANUAL OF HISTOLOGY. 
deserves to be mentioned, is “ the presence in the cavities of 
the acini of a peculiar granular material, the coagulated con- 
dition of a fluid.” Partsch has also described the occurrence 
of this granular mass within the alveoli, and he states that the 
secreting epithelia, though of normal size, were furnished with 
shrunken nuclei, and showed numerous light spots, as if the 
cells were perforated and sieve-like. It 
would appear that this writer has ob- 
served the stage of vacuolation with- 
out, however, interpreting the same in 
Creighton’s sense. 
Creighton also describes in certain 
glands the connective-tissue stroma as 
crowded with cellular elements, which 
he considers equally with the pigmented 
corpuscles as waste-cells of the secre- 
tion. Others (Winkler, Brunn, and par- 
ticularly Rauber) have assigned a far 
different significance to these bodies, as 
will appear farther on. Finally, Creigh- 
ton explains that the secretion of the 
mammary gland “ may be said to be pro- 
duced by a transformation of the sub- 
stance of successive generations of 
Fig. 195.—Acini from a partly 
expanded gland, some of them 
filled with a granular material, 
From the mamma of a pregnant 
cat. Creighton. 
epithelial cells, and in the state of full activity that transfor- 
mation of the substance is so complete, that it may be called a 
deliquescence,” 
Although Creighton’s investigations did not extend to the 
human mammary gland, there is ample ground for the belief 
that changes of evolution and involution similar to those which 
he has described in animals, constantly take place in the hu- 
man female as well. And even if we accept only some of his 
views on the inter-relations of physiological action and histo- 
logical appearance, the discrepancy still existing in the de- 
scriptions given by different authors will receive a more rational 
explanation than has hitherto been offered by writers on this 
subject. Certainly some of his assertions appear rather fanci- 
ful in their far-reaching novelty, nevertheless they deserve the 
attentive consideration which we have, at least, in part bestowed 
on them. 
From the results of our own examinations, we are unable 449 
THE MAMMARY GLAHD. 
to concede in all respects tlie correctness of Creighton’s inter- 
pretations. The evidences of epithelial destruction for purposes 
of milk secretion, are not positive and convincing. In the Har- 
derian gland, as well as in the mamma, we have observed the 
extrusion of fat-droplets from cells replete with them without 
destruction of the cell itself. Partsch agrees with us in assum- 
ing that the cells may burst or otherwise discharge their con- 
tents, and yet retain enough protoplasm to maintain their vital- 
ity ; and also that the vital contractions of the protoplasm 
may force out the oil-globules without destruction of the epi- 
thelium. What Creighton has called vacuolation does not mean 
death to the cells concerned in this action, for they retain their 
nuclei and sufficient protoplasm to become re-established as 
perfect epithelia. That this reformation of old epithelium 
takes place, is proven by the fact that a new formation by 
proliferation has never been observed, and by the additional 
circumstance that the mammary acini never show more than 
a single layer of lining-corpuscles, and, moreover, always show 
this layer complete. 
In this, as in many other respects, the mamma closely re- 
sembles the Harderian gland, more particularly of the roden- 
tia, as described by one of the writers in a monograph. The 
basement-membrane of the acini in every particular also corre- 
sponds in the two kinds of glands, being in both a homoge- 
neous, apparently structureless membrane, with superimposed 
branched adventitial cells, the so-called Stutzzellen of German 
writers. A basket-shaped reticulum, such as has been described 
by 8011, Ganger, Kolessnikow, Moullin, and others, is never 
found to constitute this membrana propria, although artifi- 
cially, appearances simulating a structure of this kind are 
readily obtained, and have been interpreted by several histolo- 
gists as natural occurrences. 
In the cutaneous sebaceous glands the secreting vesicles are 
filled with several superimposed layers of epithelia, and it is 
this circumstance which leads to an entirely different mode 
of secretion. For there it would indeed appear that the cells 
undergoing- fatty degeneration become detached from their 
bases and find their way into the narrow lumen of the acinus. 
The older or inner generation of cells thus vanishing is replaced 
by new corpuscles formed by gradual proliferation from the 
peripheral zone. 450 
MANUAL OF HISTOLOGY. 
Member's mews on the mamma and the lacteal secretion are 
somewhat startling, but must occupy our attention here. From 
a series of very carefully conducted examinations, principally 
on the glands of guinea-pigs during and after pregnancy, he 
feels Justified in concluding that milk owes its orgin to the 
entrance of countless leucocytes into the lumen of the gland- 
vesicles. The emigrated lymphoid elements, he believes, pene- 
trate the alveolar walls, passing through the single layer of 
epithelial cells which line them. Arrived in the interior of an 
ultimate acinus, the leucocytes undergo fatty metamorphosis, 
and thus at length furnish the most essential and characteristic 
ingredient of milk, viz., the milk-globules. Rauber, therefore, 
discards the notion that the formed particles of the lacteal 
secretion originate in the glandular epithelium, and represent 
the elaborated products of its functional activity. He also 
denies that previously formed milk globules, or colostrum cor- 
puscles, ever pass through the alveolar walls. Thus the prim- 
itive opinion advanced by Empedocles, describing milk as white 
pus, is in a measure revived, and milk is held to be directly 
derived from the white corpuscles of the blood. 
Preparations of mammary glands taken from animals still 
suckling their young, according to him, invariably show the 
intraglandular lymph-vessels replete with leucocytes, the stro- 
ma similarly infiltrated, identical corpuscles in greater or less 
abundance within the vesicles, and transitional forms between 
lymphoid-corpuscles and milk-globules. These claims, granted 
to be facts, and considered in conjunction with the circum- 
stance that epithelial proliferation is not seen, would certainly 
go far to make Rauber’s theory seem a somewhat plausible 
one. Nevertheless, we require corroborative evidence from 
others, before his views can be accepted as anything more than 
an ingenious hypothesis. 
Rauber has also described the occurrence of a delicate stri- 
ation within the epithelial cells of the alveoli. These strise are 
said to be in all respects similar to those found in the secreting 
elements of certain portions of the salivary glands and the 
tubules of the kidneys. 
As regards the corpuscles of Donne, or colostrum bodies, 
most authors regard them as the products of desquamation of 
the alveolar epithelium, the latter being in a condition of fatty 
degeneration (Winkler, De Sinety, Buchholtz, and others). THE MAMMAEY GLAND. 
451 
Some histologists, like Strieker, hold that oil-globules may be 
expelled from the interior of fat-filled cells without disintegra- 
tion of their protoplasmic bodies. It is an undoubtable fact 
that colostrum corpuscles, when managed with proper precau- 
tions, may be seen to yield droplets of fat under the micro- 
scope, just as amoebae reject similar contained particles. Rau- 
ber, however, maintains that these bodies represent leucocytes 
in various stages of fatty metamorphosis, and he calls such 
corpuscles, when found in the gland vesicles, galactoblasts. 
In the gland of Harder, one of the writers has found the 
spacious gland vesicles lined with very large epithelia ; and 
these cells were in many animals entirely fat-filled. They se- 
creted a greasy substance not unlike thick milk. Yet destruc- 
tion of the cell-body did not occur, at least evidences of such 
a process could not be obtained. Partsch has therefore antici- 
pated the authors in their conclusion that the secretion of milk 
is accomplished in much the same way in which the creamy pro- 
ducts of the Harderian gland are formed, i.e., without total 
destruction of epithelial cells. According to our view, then, 
and it nearly coincides with the opinion of Strieker, Winkler, 
and especially Partsch, the cells containing the fat-globules 
may, indeed, burst and discharge their contents, but the nu- 
cleus and sufficient protoplasm are retained to enable the epi- 
thelium to recuperate, and in the course of time again and 
again discharge its contents. Along with this mode of milk 
secretion, a second process occurs. This consists of the gradual 
extrusion of oil-droplets, the cell body remaining entirely in- 
tact, since the mere vital contractions of the protoplasm suf- 
fice to drive out one milk-globule after another. 
When the activity of the gland is suddenly heightened in 
the period immediately before childbirth, some few epithelial 
cells are desquamated. These, appearing in the milk of most 
women, are identical with the bodies known and described as 
colostrum corpuscles. 
Of other anatomical constituents of normal milk, we only 
find the milk- or oil-globules. They are suspended in the fluid 
emulsion which milk truly represents, in countless numbers. 
They vary in size from 0.002 to 0.009 mm. A very delicate 
fringe of protoplasm adheres to their periphery, and it is for 
this reason that they may appear to become stained when sub- 
mitted to the action of proper dyes. 452 
MANUAL OF HISTOLOGY. 
DEVELOPMENT OF THE GLAND. 
Like the other cutaneous glands of the body, the mamma 
is first formed by a proliferation inward of certain epidermal 
cells. In other words, the breast results from a downward 
extension of epiblastic corpuscles. The first unmistakable indi- 
cation of the future gland is seen about the third or fourth month 
of pregnancy. At that time it consists of a solid plug, or pro- 
Pig. 196.—1. Rudimentary form of gland 
inhuman fcetus: a, b, epidermis: c, aggrega- 
tion of cells ; d, connective tissue layer. 2. From 
a seven-months1 foetus : a, central substance ; 
b, larger, and c, smaller outgrowths. Prey. 
Pig. 197.—Embryonal mamma: a, cen- 
tral mass, with b. and c, variously shaped 
outgrowths. Prey. 
cess, extending downward from the rete-mucosum of the skin. 
This has been called Drusenfeld, by Huss. From the internal 
end of this solid process, spronts, or offshoots, are developed, 
and they represent the future separate glands constituting the 
mature organ. These buds have a pyriform, or club-like shape, 
and are surrounded ordinary embryonal connective tissue. 
The further growth of the gland takes place by a process of 
continuous extension and subdivision, but indications of the 
latter are not always found at birth. Ducts are already visible 
in the new-born infant, but the aggregations of cells represent- 
ing the future acini, remain without lumina for a much longer 
period. 
Th. Kolliker describes as a constant occurrence, especially 
marked in the breasts of female infants, the dilatation of a 
greater or smaller number of milk-ducts. Such ectatic-canals DEVELOPMENT OF THE GLAND. 
453 
have their Inmina filled with desquamated epithelial cells, and 
a whitish, granular material. Formerly, these occurrences were 
considered to be exceptional, and were regarded as having a 
pathological significance. During the first year of extra-uterine 
life, this characteristic process of progressive dilatation may 
assume such large dimensions, that the mamma may come to 
resemble cavernous tissue, the ectatic spaces of which are 
paved with flattened epithelium. Within certain limits, Kolli- 
ker regards this as a perfectly normal physiological event. But 
he adds that an exaggerated process of this kind may result in 
early mastitis. Such an occurrence, he thinks, may explain 
the rudimentary development of the breasts observed in some 
women of otherwise normal growth. 
The post-embryonal growth of the mamma has been care- 
fully studied by Danger, and his results and conclusions having 
been confirmed by the investiga- 
tions of Kolliker, Huss, and others, 
must still be received as represent- 
ing the true condition of things, in 
spite of the novel and heterodox 
views advanced by Creighton. 
Up to the time of puberty, the 
growth of the breast is very grad- 
ual and quite insignificant, even in 
females. Then, however, the ducts 
begin to rapidly ramify in all di- 
rections, and, by offshoots from va- 
rious points, true acini are at length 
developed. But they remain of 
small size until the stimulus of 
Pig. 198.—Transverse section of glandu- 
lar vesicles in a virgin. Langer. 
pregnancy causes a further evolution. In the male, the exist- 
ing ducts, as a rule, atrophy with advancing age. The evolu- 
tion changes which the mamma undergoes during pregnancy, 
have already been set forth, and there remain to be considered 
only those final phases of metamorphosis which take place in 
the climacteric period of life. 
These are readily understood, consisting essentially of a 
complete atrophy of all the secreting acini. Simultaneously 
with these atrophic changes the epithelia of the galactophorous 
ducts become flattened, and finally shrink, so as to form only 
squamous plates, which line the ramifying processes of connec- 454 
MANUAL OF HISTOLOGY. 
tive tissue representing the former lactiferous canals. The 
terminal portions of these larger duct-remnants are sometimes 
connected with minute channels, the latter being the remnants 
of collapsed smaller ducts. In some measure we tind a com- 
pensatory production of fat, which partly replaces the faded 
acini. The breasts of old women, therefore, consist of fibrous 
tissue, with a large proportion of elastic elements, fat-cells, and 
the remnants of the ducts. It may be remarked that the latter 
frequently show cystic dilatations, the cavities being filled with 
a dirty, slimy fluid. The blood and lymph-vessels, but especi- 
ally the latter, participate in the general atrophy of the tissues. 
This succinct account concerning the histogenesis of the 
mammary gland, does not, as already intimated, represent the 
unchallenged opinion on its first development. For Creighton, 
in the remarkable work already cited, radically opposes the 
view that the mamma takes its origin from the epiblast. He 
believes, on the contrary, that it starts from the mesoblast, or 
connective-tissue layer of the embryo, and not the upper epi- 
thelial layer or epiblast. According to him, moreover, and his 
conclusions are based on developmental studies, chiefly of the 
guinea-pig’s gland, the process may be justly described as a 
centripetal one, whereas the current view represents this gland- 
develpoment as essentially centrifugal. We have already ex- 
pressed our adherence to the current view, attributing this 
growth to extension from a central point. Nevertheless, it 
seems proper to briefly give the conclusions of Creighton, es- 
pecially since they appear to be singularly corroborative of the 
account given by Goodsir of this process, as early as 1842, an 
account which has apparently remained almost unnoticed by 
workers in this branch of scientific medicine. 
Creighton then concludes his inquiry as follows ; 
u 1. The mammary acini of the guinea-pig develop at many 
separate points in a matrix-tissue. The embryo cells from 
which they develop are of the same kind that give origin to 
the surrounding fat-tissue. The process of development of the 
mammary acini is, step-for-step, the same as that of the fat- 
lobules.” 
“2. The ducts of the mamma develop from the same matrix- 
tissue, by direct aggregation of the embryonic-cells, along 
predetermined lines. The ducts develop, in the individual 
guinea-pig, before the acini, whereas, in the phylogenetic sue- DEVELOPMENT OF THE GLAND. 
455 
cession, the ducts are a later acquisition. This reversal of the 
order of acquisition of parts is in accordance with the prin- 
ciple stated by Herbert Spencer, that ‘under certain circum- 
stances the direct mode of development tends to be substituted 
for the indirect.’ ” 
Hints regarding the histological study of the mamma.— 
The evolution of the mammary structure progresses pari passu 
with the development of its functional activity. It is the stim- 
ulus of pregnancy which determines both. Nevertheless, 
even during the period of its fullest physiological bloom, i.e.t 
during lactation, variations in the degree of functional activity 
normally take place. Moreover, the same gland may contain 
lobules which are comparatively at rest, and others which are 
at the full height of activity. This should always be borne in 
mind in interpreting the results of histological inspection of 
this organ, lest erroneous impressions be conveyed. 
The alveolar epithelial cells will, therefore, not be found 
alike in the different acini, nor yet even in the same vesicle. 
We may find cuboidal cells, and cylindrical ones, and flattened 
corpuscles, and in addition, various transitional forms between 
these types. 
The nucleus will appear round, or oval, and about 6-7 g in 
diameter. Sometimes two nuclei may be found in one cell. 
The radiating striation observed by Rauber in many cells, has 
already received mention. It is a noteworthy fact that the 
cells themselves contain only a very small proportion of fatty 
granules, whereas the intra-alveolar lumen is often replete 
with the same. 
In order, then, to study the histology of the gland at the 
high-water-mark of its functional activity, animals should be 
chosen which have either just given birth to their young, 
or are about to do so. For the normal conditions of the 
human mamma are rapidly transformed by post-mortem change, 
if not previously altered in consequence of the disease which 
caused the death of the individual. The organ may be exam- 
ined fresh, or else hardened and then cut in sections to be 
stained and mounted in the ordinary manner. 456 
MANUAL OF HISTOLOGY. 
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Von Brunn. Gottinger Nachrichten, No. 19. 1874. 
Labbe and Coyne. Traite des tumeurs benignes du sein. 1876. 
Buchholtz. Das Verhalten der Oolostrumkorper, etc. Gottingen, 1877. 
De Sinety. Sur le develop, et I’histol. comp, de la mamelle. Gaz. med. de Paris, 
No. 6, p. 68. 1877. 
Kolessnikow. Die Histologic der Milchdriise der Kuh. Virchow’s Archiv. Bd. 70, 
p. 531. 1877. 
Schmid, H. Zur Lehre von der Milchsecretion. Wurzburg, 1877. 
Wendt. Ueber die Hardersche Driise der Saugethiere. Strassburg, 1877. 
Winkler. Bau der Milchdriise. Jahresber. d. Ges. f. Natur. u. Heilkunde. Dres- BIBLIOGRAPHY. 
457 
den, 1874. Beitr. zur Histol u. Nervenverth. in d. Mamma. Archiv f. Gyna- 
kol. Yol. XI. 1877. 
Kolliker, Th. Beitrage zur Kenntniss der Brustdriise. Yerh. d. phys.-med. Ges. 
zu Wurzburg. 1879. 
Rabber. Ueber die Absonderung der Milch. Sitzber. d. naturf. Gesel. zu Leip- 
zig, pp. 30-84. 1879. Also, Bemerkungen ueber den feineren Bau der Milch- 
driise. Schmidt’s Jahrb. 1879. 
Ratjber. Ueber den Ursprung der Milch. Leipzig, 1879. 
Billroth. Die Krankheiten der Brustdriisen. Deutsche Chirurgie. Lieferung 
41. 1880. 
Partsch. Ueber den feineren Bau der Milchdriise. Breslau, 1880. 
Moullin. The Membrana Propria of the Mammary Gland. Journ. of Anat. and 
Phys. April, 1881. 
Saepptigen, A. Zur fein. Anat. d. Milchdriise wahrend der Lactationsperiode. 
Med. biol. acad. imp. d. sc. de St. Petersb. XI. 13-40. 1881. 
Talma, S. Beitrag z. Histogenesis d. weibl. Brustdriise. Arch. f. mikr. Anat. 
XX. 145-159. 1881-82. 
Rein G. Untersuch. u. d. embryonale Entwicklungsgeschichte der Milchdriise. 
’ Ibid. XX. 431-501. 1881-82. APPENDIX A. 
THE LYMPHATIC SYSTEM. 
W. R. BIRDSALL, M.D. 
The principal contributions which have been made to this 
subject, since the chapter on the lymphatic system was writ- 
ten, are by Drs. George and F. E. Hoggan, in several articles 
cited below, including observations on the lymphatics of the 
pancreas, the bladder, and of cartilage, besides the article pre- 
viously referred to on the lymphatics of muscular tissue and 
the skin. The views of these authors are decidedly at vari- 
ance with those of many observers. They hold that the injec- 
tion methods are not suited to demonstrate the course of the 
lymphatics, as the injection fluid follows channels in the con- 
nective tissue which are not true lymphatics. By an ingenious 
method of warming mounted specimens, from which the water 
had not been entirely removed by alcohol, they were able to 
trace the flow of the vapor thus formed along the interstices of 
the connective tissue external to the lymphatics, which, in their 
opinion, represent what others have described as lymphatics or 
41 plasma channels,” They regard silver staining as the only re- 
liable method, for it alone reveals the crenated outline of the 
endothelial cell, which they consider the necessary element in 
the constitution of lymphatics. Gold and hsematoxylon solu- 
tions are used as accessories in double staining. The details of 
these methods are too extended to be recited here, but should 
be read in the original by the student. They devise what they 
term “histological rings,” consisting of an outer ring, which 
crowds over an inner one, upon which the membrane or tissue 
has been spread, in the same manner that the parchment head of 
a tamborine or drum is stretched. All reagents are applied to 460 
APPENDIX. 
the specimen while so fastened, even to the abstraction of 
water by alcohol, and rendering transparent by oil of cloves. 
When possible, the tissue is not detached from the body of the 
animal until the specimen is finished. Very small and lean 
animals are used, as rats and mice. 
They have “failed to find evidence of the existence of such 
structures as ‘stomata,’” and believe that the peri-vascular 
and peri-neural sheaths “have no existence in fact,” while 
they consider erroneous the view that the “branched cells stand 
in formal connection with lymph-channels ; or that the cells or 
cavities in which they lie are lymphatic radicles.” 
Klein has contributed an article on the lymphatics of the 
skin, in which he reiterates his former assertions, and combats 
the opposing views Just referred to. 
BIBLIOGRAPHY. 
Hoggan, G-. and F. E. On the Lymphatics of Cartilage and of the Perichondrium. 
Jour. Anat. and Phys., XV., 131-136. London, 1880-81. 
Ibid. On the Comparative Anatomy of the Lymphatics of the Mammalian Urinary 
Bladder. Ibid., XY., 355-877. 
Ibid. On the Lymphatics of the Pancreas. Ibid., XV., 475-495. 1881. 
Klein. On the Lymphatics of the Skin. Quart. Jour. Mic. Sci. 1881. 
Jogkdain. Sur les sacs-sous-cutaines et les sinus lymphatiques de laregione cepha- 
lique dans la rana temporaria. Compt. Bend., Acad. d. Sc. XCIII., 597- 
600. Paris, 1881. APPENDIX B. 
THE SALIVARY GLANDS. 
Bt EDMUND C. WENDT, M.D., 
Curator of the St. Luke’s and St. Francis’ Hospitals, etc., New York City. 
General remarks.—Modern physiological research has im- 
parted a new stimulus to histological investigations. For the 
fact is now well established that, in many tissues and organs, 
functional activity, alternating with rest, represent phases of 
life, each accompanied by distinctly recognizable morphologi- 
cal changes. No organs or class of organs have been more 
carefully, industriously, and, withal, ingeniously studied, in 
this direction, than the salivary glands. But although abun- 
dant new evidence has thus been accumulated, it cannot be 
said that the testimony of different authors has so far suc- 
ceeded in harmonizing conflicting views and contending theo- 
ries. It will be the aim of the writer to avoid, as much as pos- 
sible, theoretical and controversial reasonings, and present the 
subject in its present aspect of real knowledge. 
All the glands constituting this group belong to the com- 
pound acinous type. Here, at the very outset, we are con- 
fronted by the assertions of Grot and Klein, who positively 
declare that the salivary glands are exclusively made up of 
convoluted tubules. From the repeated examination of numer- 
ous specimens of different glands, the writer is satisfied that the 
acinous preponderates very decidedly over the tubular form, 
and hence it is more correct to give them the former name. 
It may also be mentioned, in this connection, that Her- 
mann has described the normal occurrence of a compound 
tubular mucous gland found in intimate relationship with the 
submaxillary of man and several animals. Heidenhain, how- 
ever, demonstrated that the organ described by Hermann really 
corresponds to the sublingual gland. 462 
APPENDIX. 
The salivary glands lie enclosed in a connective-tissue 
capsule of varying thickness. From this envelope tra- 
becles are given off, and, traversing the organ in all directions, 
divide it into secondary lobes and lobules. In this support- 
ing frame-work leucocytes are found in greater or less abun- 
dance, surrounding the inter-lobular ducts and vessels. In 
addition, large plasma cells (Waldeyer), or Ehrlich’s corpuscles 
(Mastzellen), are commonly encountered. The excretory ducts 
form a system of ramifying tubes, terminating in the secreting 
acini or vesicles. 
the acini {Alveoli, Ultimate Secreting Vesicles). 
Each acinus consists of a membrana propria (basement mem- 
brane) lined by a varying number of secreting cells. 
In fresh specimens, derived from recently killed animals, the 
membrana propria invariably appears as a very delicate, trans- 
lucent, and apparently structureless membrane. In sections of 
hardened glands, flattened, oval nuclei are found studding this 
membrane. 
8011, Heidenhain, Lavdovsky, and, in fact, most recent au- 
thors, assert that the membrana propria is composed of fiat, 
branching cells, which form a basket-like reticulum, containing 
the secreting corpuscles. The writer cannot agree to this view. 
Branching, nucleated bodies of the kind described by these au- 
thors are, indeed, readily visible after suitable modes of prep- 
aration. But they usually lie outside of the membrana pro- 
pria, being superimposed to afford the necessary additional 
strength to this extremely delicate membrane. Pfiiiger de- 
scribed them as multipolar ganglion cells. But his views are 
clearly erroneous, having been refuted by all later investigators, 
with but few exceptions. One of these, Kupffer, claims to 
have succeeded in demonstrating the direct entrance of nerve- 
fibrils into the glandular acini in the cockroach {blatta orien- 
talis). But even this author failed to corroborate the assertions 
of Pfiiiger with regard to man and the higher animals. 
According to the observations of the author the membrana 
propria is a nucleated connective-tissue membrane. In the foetus 
it is first formed in the following way : Solid proliferating plugs 
of epithelia, representing the future parenchyma, grow into 
the surrounding embryonic tissue. The layer of connective- APPENDIX. 
tissue cells immediately adjoining the epithelia gradually as- 
sumes a flattened shape. At length these corpuscles coalesce 
and form a richly nucleated membrane. In later life some of 
the nuclei atrophy and disappear, but a certain number usu- 
ally persist. For this reason the membrana propria in adult 
glands appears as a homogeneous membrane, containing a vary- 
ing number of nuclei. The branched cells are superimposed, 
or lie beneath it; but while they are found to adhere to it, they, 
nevertheless, do not form true constituent elements of the mem- 
brane in question. 
THE SECRETING CELLS. 
The epithelia of the proper gland substance, usually line the 
basement membrane, in a single layer of nucleated, pyramidal, 
cuboidal, or polyhedral cells. In structure they differ rather 
widely in the various glands belonging to this group. It will 
be well, therefore, to consider, separately, first the cells of the 
albuminous glands, and then those of the mucous type. 
1. Albuminous glands.—Formerly these were known as 
“serous” glands, since the product of their secretion was ap- 
parently a serous fluid. Recently, however, Heidenhain has 
demonstrated the abundant presence of albuminoid matter 
therein. Glands of this type are, therefore, more properly 
called albuminous. The parotid gland of man and mammals 
generally, the lachrymal glands, the submaxillary glands of 
certain animals, and the larger portion of the human submax- 
illary gland, are included in this category. 
In fresh specimens the cells of their alveoli appear to be 
so completely filled up with darkly granular matter that their 
boundaries are either invisible or quite obscure. Sections of 
hardened glands, however, show the intercellular boundary lines 
clearly marked. The form of these corpuscles is now seen to be 
either somewhat rounded or polygonal. Each one is, as a rule, 
provided with a pale, spherical nucleus, occupying a periphe- 
ral position, i.e,9 approaching the membrana propria. In hard- 
ened specimens of resting glands, the nuclei commonly assume 
a stellate or angular form, the result of shrinkage. As regards 
the size of the salivary epithelia, their average diameter is 
0.015 mm., the nuclei measuring 0.006 mm. It should be borne 464 
APPENDIX. 
in mind, however, that many cells fall considerably below this 
average, whereas others measurably exceed it. 
2. The mucous glands.—ln the simplest glands of this 
type, the alveoli contain a single layer of large, clear, trans- 
parent, columnar cells, al- 
most identical in appear- 
ance with the so-called 
goblet cells of the alimenh 
ary canal. In recent speci- 
mens the nucleus is found 
round or oval, but in hard- 
ened glands it appears quite 
fiat. In all cases it almost 
lies in contact with the 
membrana propria. 
But the glands of this 
variety contain, in addition 
to the simple mucous cells 
just described, smaller and 
Fig. 199.—Section of mucous gland at rest, showing 
crescents of Giannuzzi, Lavdovsky. 
very granular bodies, which are known as the crescents or 
lunulce of Griannuzzi. They usually occur in semilunar groups, 
and are found external to the mucous cells, and Just beneath 
the basement membrane. The individual cells of such groups 
are not always provided with a nucleus. In some, however, 
two nuclei appear. 
Isolated mucous cells (maceration of fresh gland in iodized 
serum or chromate of ammonia), appear to be furnished with a 
distinct cell-membrane. 
A protoplasmic process also juts out from the vicinity of 
the nucleus. While in situ these processes are placed in appo- 
sition to the membrana propria. They become deeply tinged 
in stained specimens. The contents of these mucous cells is a 
clear substance, containing a few granules, and giving the char- 
acteristic micro-chemical reactions of mucin. 
As regards the granular crescents, their behavior under the 
application of different chemical reagents leaves no doubt as to 
the albuminoid nature of their cell-substance. There is an in- 
finite variety in the proportion of albuminous cells to crescents. 
For we find in some glands a very marked preponderance of 
one variety of corpuscular elements over another, whereas in 
others they are about equally distributed. APPENDIX. 
465 
Having thus briefly indicated the characteristic appearances 
of the cellular constituents of the alveoli, as found in glands 
which had been at rest before being examined, we are now 
prepared to appreciate the morphological changes occurring 
in the active organs. 
In the quiescent state of the gland, then, the protoplasm of 
its alveolar cells is gradually converted into a material resem- 
bling the ultimate product 
of secretion. It is but na- 
tural, therefore, to And in 
gland cells, which have 
enjoyed prolonged rest, a 
small proportion of pro- 
toplasm. In fact, as has 
been already stated, the 
quiescent gland is marked 
by the coarsely granular 
appearance of the secret- 
ing corpuscles, and by a 
Fig. 200.—Mucous gland with changes due to incipient 
secretion. Lavdovsky. 
more or less complete obscurity both of cell-boundaries and 
nuclei. In the mucous glands this is due to the abundant 
presence of mucigenous material, destined later to become 
converted into mucin. 
But let a proper stimulus now waken the dormant activity 
of the gland, and interesting 
changes are at once inaugurat- 
ed. The cells gradually lose 
their granular aspect, distinct 
boundary lines become visible, 
and the nucleus appears. In 
glands exhausted by protracted 
secretion or excessive stimula- 
tion, we accordingly find con- 
spicuous nuclei, shrunken al- 
veolar corpuscles, and small 
granular cells closely resem- 
bling the crescents of Giannuzzi. 
The entire alveolus appears re- 
Fig. 201.—Mucous gland with structural altera- 
tion of advanced secretion. Lavdovsky. 
duced in size. At length, in typical mucous glands, the large, 
clear, mucous cells are found to have entirely disappeared. Ilei- 
denhain and his followers have concluded, from these easily 466 
APPENDIX. 
demonstrable and constantly recurring phenomena, that the 
mucous cells suffer actual destruction, and that restitution of 
the alveolar epithelium occurs in consequence of proliferation 
of the parietal cells. 
The writer cannot accept this interpretation. His own obser- 
vations point to the probability that actual disintegration of the 
secreting cells occurs only under pathological conditions. The 
mucous cells disgorge the mucin which has been formed within 
them by protoplasmic metamorphosis, they alter their appear- 
ance considerably, but nevertheless they continue to exist. It 
is by a constant renewal of their protoplasm that they are thus 
able to secrete for a period of indefinite length. Destruction 
and recuperation, growth and decay, are thus constantly tak- 
ing place at the same time and in the same cell. 
EXCRETORY DUCTS. 
The lobar, and larger interlobular ducts have essentially 
the same structure. That is, we find a basement membrane 
lined with a double layer of large columnar cells, and sur- 
rounded by a varying amount of connective tissue. The 
nucleus is oval and sharply defined, and it is generally found 
in the middle of the cell. A longitudinal striation is often 
distinctly seen in these epithelia, giving them the appearance 
of being traversed by minute rodlets. Lateral anastomoses 
have been described between these rodlets by Klein. In 
fact, this author finds networks of various kinds in all the 
cellular constituents of glands, and even in most nuclei. But 
his assertions in this respect are not confirmed by most recent 
authors, and certainly in fresh specimens, such reticula are 
conspicuously absent. When they do occur it seems that they 
are but the anatomical expression of protoplasmic coagulation. 
The interlobular ducts or salivary tubes {Speichel-Hohren) of 
Pfluger have only a single layer of columnar epithelia, the ex- 
ternal portion of which (that nearest the basement membrane) 
is characterized by longitudinal fibrillse, or rods. At about 
the middle of each cell, there is a large, round or oval nucleus. 
Between the intralobular ducts of larger calibre and the al- 
veoli, there is found still another variety of excretory channels. 
These are the intermediate or intercalated ducts. They are APPENDIX. 
467 
lined with relatively long, spindle-shaped corpuscles (parotid 
gland), or small, cuboidal cells (submaxillary of different ani- 
mals). 
Quite recently Klein has also described “ a distinct, narrow, 
short bit,” found intermediate between the salivary tubes and 
the intercalated part. 
This he calls the neck, 
and points out the simi- 
larity of such an arrange- 
ment with the transition 
of the duct into the al- 
veolus of the pyloric 
glands. 
A structure of this 
kind is indeed often seen, 
but it is also frequently 
Fig. 202.—Glandular acini with intercalated portion of duct. 
Ebner. 
absent, so that we are not justified in regarding it as a con- 
stant anatomical feature. Finally, the presence of smooth, 
muscle fibres in the main ducts is a fact which deserves to be 
mentioned. 
Blood-vessels and lymphatics.—A beautiful and dense ca- 
pillary plexus surrounds the acini of the salivary glands. But 
the vascular walls are not in immediate contact with the 
membrana propria, being separated therefrom by lymph- 
spaces. When the latter contain much fluid, the distance be- 
tween capillary wall and basement membrane will thus be 
materially greater than when only a small amount of liquid is 
present in these lymph-channels. The arteries and veins are 
devoid of peculiarities deserving of special mention. 
In addition to the perivascular lymphatics, just mentioned, 
there are found channels around the ducts and acini. Both 
sets of vessels are connected, however, by abundant anasto- 
moses. Yalves are present in these lymph-vessels, and lateral 
pouches corresponding to them. This gives rise to a sacculated 
appearance, which is so characteristic of their course. 
Nerves.—Medullated fibres are readily seen to enter the 
salivary glands at the hilus. They follow the course of the 
main duct, forming a plexus around its larger ramifications. 
From this reticulum, which is provided with collections of 
ganglia of varying dimensions, secondary medullated fibrils 
arise, and are distributed between the smaller lobules. Gan- 468 
APPENDIX. 
glion cells, but of smaller size, are still found here, hlon-me- 
dnllated fibres are at length given off from the other nerves, and 
may be traced to the acini. But concerning their terminal dis- 
tribution, we have as yet no definite knowledge, only a num- 
ber of more or less acceptable statements and theories. 
Most conspicuous among these is Pfluger’s, because couched 
in words of most positive assurance. Briefly stated, this au- 
thor regards the secreting cells as the real nerve terminations. 
And he bases this conviction on what he claims to have ac- 
tually seen, viz., the direct entrance of axis cylinders into the 
glandular epithelia. 
But, with a few exceptions, presently to be mentioned, all 
recent observers have failed to corroborate Pfluger’s assertions. 
These exceptions are Patenko, who claims to have seen 
nerve-endings in the uterine glands; Kupffer, wdio, as already 
stated, saw similar terminations in the so-called salivary bodies 
of the cockroach {hlatta orientalis), and Openchowski. The 
latter asserts that, in the glands of the nictitating lid of frogs, 
he has discovered unmistakable evidence of the direct entrance 
of nerve-fibrils into secreting epithelia. Such fibres, he says, are 
continuous, with an intracellular reticulum. Finally Palladino, 
ten years ago, described somewhat similar appearances. 
It does not seem desirable to enter more fully into the vari- 
ous details of pending controversies concerning the termination 
of nerves indifferent glands. What has been briefly described, 
is what we actually see, and not the imaginary pictures drawn 
by enthusiastic observers. 
Intra-alveolar networks and capillary secreting ducts have 
been very minutely described by different authors. As regards 
the latter there can be no doubt that an albuminoid intercellu- 
lar cement-substance, which may be displaced by any fluid in- 
jected with sufficient force into the main duct, has given rise 
to appearances simulating the existence of minute channels 
between the secreting cells. In the light of our present knowl- 
edge it may be definitely asserted that capillary excretory 
ducts, possessed of walls of their own, do not constitute real 
structural features of the salivary glands. 
The same also applies to the reticulum which many have i 
claimed to exist within the acini of all these glands. Proto- 
plasmic coagulation, resulting from the different hardening 
processes and methods of preparation, must be held accounta- APPENDIX. 
469 
ble for the net-like appearance referred to. In the living gland 
such a reticulum is not found. 
BIBLIOGRAPHY. 
Giannuzzi. Bericht d. Sachs. Gesel. d. Wiss. 1867. 
Kolliker. Gewebelehre. 1867. 
Pfluger. Die Endigung d. Absonderungsnerven in den Speicheldriisen, Bonn, 1869. 
Also, Strieker’s Manual. 
8011. Beitr. z. mikrosk. Anat. d. Driisen. Berlin, 1869. 
Krause. Arch. f. Anat. u. Physiol., p. 9. 1870. 
Ewald. Beitr. z. Histol., etc., d. Speicheldriise, etc. Berlin, 1870. 
Ebner. Ueber die Anfange d. Speichelgiinge. Arch. f. mikros. Anat. Vol. VIII. 
1873. 
Ebner. Die Acinosen Driisen. d. Zunge. Graz, 1873. 
Kupffer. Arch. f. mikros. Anat. Vol. IX. 1873. Also, Beitr. z. Anat. u. Phys. 
Leipzig, 1875. 
Xussbaum. Die Fermentbildung in d. Driisen. Bonn, 1876. Also, Ueber den Ban 
u. die Thiitigkeit d. Driisen. Arch. f. mikros. Anat. Vol. XIII. 1877. 
Lavdoysky. Zur fein. Anat. d. Speicheldriisen. Arch. f. mikros. Anat. Vol. 
XIII. 1877. 
Langley. Untersuch. aus d. phys. Inst, zu Heidelberg. Vol. I. 1878. 
Bermann. Ueber d. Zusammensetzung d. gland. Submax. Wiirzburg, 1878 
Hebold. Beitr. zur Secret, u. Regeneration d. Schleimzellen. Bonn, 1879. 
Beyer, G. Die Glandula sublingualis, etc. Diss. Breslau, 1879. 
Langley, J. N. On the Changes in Serous Glands during Secretion. Jour. Phys., 
Vol. 11., p. 361. 1879. Also. On the Structure of Serous Glands in Rest and 
Activity. Proc. Roy. Soc., p. 377. 1879. 
Heidenhain. Studien d. phys. Inst, zu Breslau. IV. 1868. Also, Vol. V. of Her- 
mann’s Handbuch d. Physiologie. 1880. 
Nitot, E. Recherches anat. sur la glande Sous-max., etc. Arch, de Phys. Vol. 
VII., p. 374. 1880. 
Openchowski. Histologisches zur Innervation der Driisen. Arch. Physiol. Vol. 
XXVII., p. 333. 1883. 
Klein. On the Lymphatic System and Minute Structure of the Salivary Glands 
and Pancreas. Quart. Jour. Micros. Soc. April, 1883. INDEX. 
ACINI of expanded mamma, 444 
of liver, 188 
of lung, 260 
of pancreas, 410 
Adenoid tissue, 69 
of lymph-glands, 178 
Adventitia of capillaries, 148 
of arteries, 151, 155 
Afferent vessels of kidney, 206 
Aglobulie intense, 88 
Air-cells of lung, 260 
Alcohol and acetic and muriatic acids, 15 
and acetic acid mixture, 14, 15 
ALIMENTARY CANAL, 386 
general considerations, 386 
Lakge Intestine, 400 
blood-vessels of, 401 
lymphatics of, 401 
nerves of, 401 
structure of, 400 
(Esophagus, 386 
blood-vessels of, 388 
fibrous envelope of, 388 
layers of, 386 
lymphatics of, 388 
mucous membrane of, 386 
muscular coat of, 887 
muscularis mucosae of, 387 
nerves of, 388 
submucous layer of, 387 
Rectum, 401 
sphincter ani of, 401 
structure of, 401 
Small, Intestine, 394 
blood-vessels of, 399 
Brunner’s glands of, 397 
corona tubulorum of, 396 
follicles of Lieberkiihn of, 398 
glands of, 396 
lymphatics of, 399 
ALIMENTARY CANAL— 
Small Intestine— 
mucous membrane of, 395 
muscular coat of, 394 
muscularis mucosas of, 396 
nerves of, 399 
plexus of Auerbach, 399 
plexus of Meissner, 399 
Peyer’s patches of, 396 
serous coat of, 394 
solitary follicles of, 396 
submucous layer of, 396 
valvulas conniventes of, 395 
villi of, 395 
Stomach, 388 
blood-vessels of, 392 
compound peptic glands of, 390 
etat mamelonne of, 389 
lymphatics of, 393 
mucous membrane of, 389 
muscular coat of, 388 
muscularis mucosas of, 389 
nerves of, 393 
peptic glands of, 389 
pyloric glands of, 391 
serous covering of, 388 
submucous layer of, 389 
Vermiform Appendix, 401 
Alizarine, 28 
Alum carmine, 27 
Alveoli of lung, 260 
Ammonia bichromate, 14 
Amoeboid movement, 39, 40 
Anastomosis of capillaries, 148 
Angle of aperture, 11 
of lenses, 10 
Aperture, angle of, 11 
Apparatus, general, for microscopical 
work, 1, 2, 3, 4 
Appendix vermiformis, 401 472 
INDEX, 
Arachnoid, spinal, 297 
Archil, staining with French, 28 
Arciform fibres of medulla oblongata, 
394 
Bibliography— 
of teeth, 108 
of thymus gland, 419 
of thyroid body, 419 
of urinary excretory passages and su- 
prarenal capsules, 437 
Areola of mamma, 443 
Arnold’s borax carmine staining, 23 
Arrangement of object, 6 
Arteria centralis retinse, 347 
hyaloidea, 849 
Arteries, 153 
Arterioles, 153 
Auerbach, intercalated areas of, 147 
plexus of, 123, 399 
Auricle of ear, 353 
Axis-cylinder of nerve-fibres, 110 
EARTHOLINE, glands of, 241 
Beale, spiral fibre of, 123 
Bed of nail, 294 
Bibliography— 
of alimentary canal, 403 
of blood, 54 
of blood-vessels, ICI 
of bone, 101 
of brain, 326 
of cartilage, 88 
of central nervous system, 326 
of cerebellum, 320 
of connective substances, 81 
of ear, 367 
of epithelium, 61 
of eye, 353 
of female organs of generation, 251 
of general methods, 32 
of kidney, 223 
of liver, 199 
of lymphatic system, 183, 460 
of male organs of generation, 238 
of mammary gland, 456 
of mouth and tongue, 384 
of muscle, 140 
of nasal fossae, pharynx, tonsils, 375 
of nervous system, 127 
of pancreas, 418 
of pituitary body, 419 
of respiratory tract, 267 
of salivary glands, 469 
of skin, 295 
of spinal cord, 325 
of spleen, 418 
Bichromate of ammonia, 14 
preparation of nerves with, 115 
Bichromate of potassium, 14 
Bigelow’s studies on cartilage, 87 
Bile-ducts, 191 
Bismark brown, 26 
Bladder, 430 
BLOOD, 34 
amoeboid movements of leucocytes 
of, 39 
Brownian movement in leucocytes of, 
39 
circulation of, examined during life, 
45 
curara for paralysis of frogs, 45 
globules of, in different fluids, 38 
granules of, 39 
hsematoblasts of, 47 
heating slide for the study of, 40 
liquor sanguinis, or plasma of, 34 
red corpuscles of, 34 
action of acids on, 43 
of alkalies on, 44 
of carbonic acid on, 42 
of distilled water on, 41 
of electricity on, 44 
of salt solution on, 40 
counting of, 48, 53 
crenation of, 45 
development of, 47 
examination of, 47 
haemochromometer for estimat- 
ing richness, 53 
haemoglobin of, 53 
internal structure of, 46 
Keyes’s method of counting, 50 
Malassez’s method of counting, 
50 
measurement of, 36 
number of, 37 
stroma of, 46 
third corpuscular element of, 48 
white or colorless corpuscles of, 48 
Blood-corpuscles, nucleated, 95 
Blood-crystals, 53 INDEX 
473 
BLOOD-VESSELS, 143 
methods of injecting, 30 
of bladder, 431 
of choroid, 337 
of cornea, 333 
of iris, 343 
of kidney, 213 
of large intestine, 401 
of liver, 186 
of lung, 363 
of lymph-glands, 179 
of mamma, 443 
of mouth, 379 
of oesophagus, 388 
of optic nerve, 349 
of ovary, 247 
of pancreas, 411 
of penis, 234 
of retina, 347 
of skin, 279 
of small intestine, 399 
of spinal cord, 398 
of spleen, 407 
of stomach, 393 
of suprarenals, 436 
of testis, 234 
of thymus, 414 
of thyroid, 416 
of uterus, 245 
Arteries, 151 
adventitia of, 151, 155 
external elastic coat of, 155 
internal elastic coat of, 152 
internal fibrous coat of, 153 
intima of, 153 
media or musculosa of, 154 
muscular and elastic types of, 153 
Arterioles, 152 
Capillaries, anastomosis of, 148 
endothelial desquamation, 147 
endothelium, 143 
genesis, reproduction, and regen- 
eration of, 150 
intercalated areas of, 147 
intracellular network, 143 
intranuclear network, 143 
perithelium or adventitia of, 148 
ramification of, 149 
structure of, 146 
varieties of, 145 
Coccygeal Gland of Luschka, 158 
BLOOD-VESSELS— 
Corpora Cavernosa, ICO 
general remarks on, 143 
Intercarotid Gland, IGO 
lymphatics of, 161 
nerves of, 161 
perivascular spaces, 161 
varieties of, 142 
vasa vasorum, 161 
Veins, 155 
distinction between veins, arte- 
ries, and capillaries, 156 
internal elastic coat of, 157 
internal fibrous coat of, 157 
points of difference from arte- 
ries, 156 
structure of, 156 
valves of, 158 
venules, 156 
Boehmer’s hgematoxylon, 23 
BONE, 89 
cancellous tissue of, 94 
chondro-porosis, 98 
compact tissue of, 89 
corpuscles of, 90 
development of, 96, 99 
formation of callus in, 100 
formation of, from cartilage, 97 
from membrane, 98 
Haversian canals of, 91 
Howship’s lacuna; of, 100 
intermediary cartilage of, 97 
lacunae of, 91 
lamellae of, 90 
marrow of, 95 
cells of, 95 
myeloplaxes, 95 
primary cavities of, 98 
red, 95 
yellow, 95 
metaplastic, 98 
naphthaline yellow for staining, 37 
osteoblasts, 96, 98 
osteoclasts, 100 
osteoporosis, 99 
periosteal processes of, 94 
periosteum of, 95 
points of ossification, 98 
preparation of, 92 
Sharpey’s fibres of, 94 
varieties of, 89 474 
INDEX, 
Borax carmine, 23 
Bowman’s capsules of kidney, 204 
glands of nose, 373 
membrane, 79, 331 
Brain, method of hardening, 15 
Branched corpuscles of connective tissue 
67 
CARTlLAGE— 
perichondrium of, 86 
purpurine for staining, 85 
reticular or yellow elastic, 85 
varieties of, 83 
Spina’s views on, 87 
Cartilages of bronchi, 257 
of larynx, 354 
Cartilago-triticea of larynx, 253 
Caruncula lachrymalis, 330 
Cavernous tissue, 160 
Cells, giant, 95 
of liver, 189 
Cellular tissue, 63 
Cement of teeth, 105 
Central canal of spinal cord, 301 
CENTRAL NERVOUS SYSTEM, 296 
Bronchioles, 260 
Bronchi, primary, 257 
smaller, 259 
Brownian movement, 39 
Brunner’s glands, 397 
Burdach, column of, 298 
/CALCIFICATION of cartilage, 84 
of cartilages of larynx, 255 
Callus, formation of, 100 
Calyx of kidney, 216 
Canal, central, of spinal cord, 301 
of Petit, 350 
of Schlemm, 336 
Canals, dentinal, 104 
intermediate, of liver, 184 
semicircular, 359 
Capillaries, 142 
Capillary bile-ducts, 193 
Capsule, internal, of brain, 317 
of kidney, 310 
of liver, 183 
of spleen, 404 
of suprarenal bodies, 433 
of Tenon, 337 
of thymus, 413 
of thyroid, 415 
Capsules, suprarenal, 431 
Carmine, alum, 37 
CARTILAGE, 83 
Bigelow’s studies on, 87 
capsules of, 82 
corpuscles of, 82, 83 
division of, 86 
structure of, 87 
daughter-cells, 84 
fibrillation of, 83 
fibrous, 86 
hyaline, 83 
calcification of, 84 
methods of studying, 84 
intercellular substance of, 83, 87 
intermediary, 97 
parenchymatous, 83 
Cerebellum, 317 
cells of Purkinje of, 318 
corpus dentatum of, 317 
cortex of, 319 
cerebral ganglia, 319 
cerebral ventricles, 319 
Cerebrum, 321 
cortex of, 321 
convolutions of, 821 
fissure of Rolando, 331 
of Sylvius, 321 
island of Reil, 323 
meninges of, 321 
minute structure of, 333 
cortex of, 323 
motor tract of hemispheres, 322 
paracentral lobule, 323 
choroid plexus, 820 
corona radiata, 317 
corpus striatum, 319 
ependyma, 330 
internal capsule, 317 
locus caeruleus, 315 
niger, 316 
medulla oblongata, 307 
arciform fibres of, 309 
central gray matter of, 308 
decussating fibres of, 307 
formatio-reticularis of, 308 
raphe of, 307 
nucleus lenticularis, 316 
Olivary Body, 310 
glosso-pharyngeal, root of, 313 
hypoglossal, nucleus of, 311 INDEX, 
475 
CENTRAL NERVOUS SYSTEM— 
Olivaky Body— 
nucleus and root of abducens 
nerve, 314 
parolivary nucleus of, 311 
roots of fifth nerve, 315 
upper spinal accessory, nucleus 
of, 811 
optic thalami, 319 
pons, 315 
spinal arachnoid, 297 
spinal cord, 298 
amyelinic fibres of, 301 
blood-vessels of, 298 
central canal of, 301 
cervical enlargement of, 304 
column of Burdach of, 298 
column of Clarke of, 304 
column of Goll of, 298 
dorsal region of, 304 
epithelium of, 301 
filum terminale of, 302 
general histology of, 298 
gray commissure of, 304 
gray matter of, 299 
lumbar enlargement of, 303 
methods of study of, 305 
myelinic fibres of, 300 
nerve-elements of, 299 
neuroglia-cells of, 298 
root radicles of, 299 
special study of different portions 
of, 301 
white commissure of, 303 
white substance of, 299 
spinal dura mater, 296 
spinal fluid, 297 
spinal pia mater, 297 
Cerebellum, 317 
Cerebral ganglia, 319 
meninges, 321 
ventricles, 319 
Cervical enlargement of spinal cord, 304 
Chalice cells, 60 
Chamber, moist, 42 
Chloride of gold, 28, 29 
Chondro-porosis, 98 
Ihoroid coat of eye, 338 
plexus, 320 
Cilia of eyelids, 328 
Ciliary body, 340 
Ciliated epithelium, 58 
Circle of Haller, 349 
Circulation of blood, 45 
Circulus venosus of Haller, 442 
Clarke, column of, 304 
Clitoris, 240 
Coats of arteries, 152 
Coccygeal gland, 158 
Cochlea, 362 
Cohnheim’s muscular areas, 136 
Colostrum, 450 
Columnar epithelium, 60 
Column of Burdach, 298 
of Clarke, 304 
of Goll, 298 
Columns, muscular, 138 
Commissure, gray, of spinal cord, 304 
white, of spinal cord, 303 
Conjunctiva, 330 
fornicis, 329 
tarsi, 328 
CONNECTIVE SUBSTANCES, 62 
branched corpuscles of, 67 
corpuscles of, 65 
development of, 64, 65 
fibrillated, 66 
growth and development of, 79 
intercellular substance of, 64 
lymphoid corpuscles of, 67 
of mesentery, 68 
plasma-cells of, 67, 74 
reticular form of, 66 
of liver, 188 
of nerves, 126 
of skin, 275 
Contraction, study of muscular, 135 
Convoluted renal tubules, 205 
Corium, 277 
Cornea, 331 
preparation of, 25 
Corneal corpuscles, 75 
tissue, 75 
Corneous layer of skin, 274 
Corniculum of larynx, 255 
Corona radiata of brain, 817 
tubulorum, 316 
Corpora cavernosa, 160 
Corpus albicans, 250 
dentatum cerebelli, 817 
luteum, 249 
Corpuscles, colostrum, 450 476 
INDEX 
Corpuscles, corneal, 75 
fixed, of cornea, 332 
lymphoid, of lymph-glands, 178 
of skin, 277 
Malpighian, of spleen, 404 
of bone, 90 
of cartilage, 82, 83 
of Donne, 450 
of muscle, 136 
tactile, 124 
of skin, 280 
of tendon-tissue, 73 
yellow, of mamma, 444 
Corpus striatum, 319 
Cortex cerebri, 321 
Cortex of cerebellum, 319 
of kidney, 201 
of suprarenal capsules, 432 
Corti’s membranes, 366 
organ, 362, 364 
Cowper’s glands, 227 
Development of ovary, 250 
of pancreas, 412 
of sebaceous glands, 266 
of spleen, 409 
of suprarenals, 436 
of sweat-glands, 282 
of teeth, 105 
of thymus, 414 
Diaphragms, 5 
Dilator muscle of iris, 342 
Direct light, 5 
Division of cartilage corpuscle, 84, 186 
Double staining with borax carmine and 
indigo carmine, 22 
with eosine and aniline colors, 24 
Doyere’s eminence, 126 
Drusenfeld of mamma, 452 
Duct, cystic, 198 
of pancreas, 411 
thoracic, 174 
Ducts, ejaculatory, 235 
galactophorous, 441 
Ductus communis, 198 
Dura mater, spinal, 296 
Creighton’s views on the mamma, 445, 
446, 454 
Crista acustica, 360 
spiralis, 364 
Crystalline lens, 350 
Curara for producing paralysis, 45 
Cuticula of teeth, 107 
Cylindrical epithelium, 60 
Cystic duct, 198 
Czermak, interglobular spaces of, 103 
TjARTOS, 231 
Daughter-cells of cartilage, 84 
Decidua, 245 
Deiter’s, protoplasmic processes of, 120 
Dentine, 103, 106 
Dentinal canals, 104 
globules, 104 
teeth, 106 
Descemet’s membrane, 79, 333 
Detrusor urinse, 430 
Development of blood-corpuscles, 47 
of capillaries, 150 
of bone, 96 
of enamel, 108 
of fat-tissue, 168 
of hair, 293 
of lymphatics. 175 
of mamma, 452 
of nail, 295 
TIAR, 353 
Eustachian tube, 355 
External ear, 353 
auricle of, 353 
meatus of, 353 
membrana tympani of, 354 
Internal ear, 357 
“auditory teeth” of, 364 
cochlea of, 362 
Corti’s membrana tectoria of, 
366 
crista acustica of, 360 
crista spiralis of, 364 
Henson’s prop-cells of, 366 
labium tympanicum of, 364 
labium vestibulare of. 364 
lamina reticularis of, 360 
lamina spiralis of, 362 
macula acustica of, 360 
membrana basilaris of, 364 
membrane of Reissner, 362 
membranous labyrinth of, 358 
modiolus of, 362 
organ of Corti, 362, 364 
otoliths of, 358 
recessus internus of, 364 INDEX. 
477 
Ear- 
Internal ear— 
saccule of, 358 
scala tympani of, 362 
scala yestibuli of, 362 
semicircular canals of, 359 
utricle of, 358 
zona pectinata of, 366 
Middle ear, 355 
glands of, 355 
structure of, 355 
Ectasia of milk-ducts, 452 
Efferent vessels of kidney, 206 
Ejaculatory ducts, 235 
Elastic fibres of skin, 277 
Elastic tissue, 77 
fibres of, 77 
networks of, 78 
of ligamentum nuchas, 79 
perforated membrane of, 79 
Electricity, action of, on blood, 44 
Embedding specimens, 15, 16 
Enamel, 102 
Enamel organ, primary, 107 
secondary, 107 
Endoneurium, 126 
Endothelium, 80 
and stomata of lymphatics, 169 
germinating, 165 
vascular, 143 
Eosine, 24, 25 
and hasmatoxylon, 25 
Ependyma, 320 
Epidermis, 271 
Epididymis, 231 
Epiglottis, 255 
Epineurium, 126 
Epithelium, 56 
bacteria of, 57 
ciliated, 58 
columnar or cylindrical, 60 
granules of, 61 
networks of, 61 
pigmented, 58 
squamous or flattened, 57 
structure of, 61 
Epithelium of bladder, 430 
of collecting tubules of kidney, 211 
of involuted mamma, 446 
of looped renal tubules, 210 
of lung, 261 
Epithelium of mamma, 444 
of mouth, 377 
olfactory, 371 
of renal tubules, 206 
of spinal cord, 301 
of thyroid, 415 
Erector pili muscles, 422 
Etat mnmelonne of stomach, 389 
Eustachian tube, 355 
Expanded mamma, structure of, 444 
External ear, 353 
External elastic coat of arteries, 155 
EYE, 328 
arteria hyaloidea of, 349 
caruncula lachrymalis, 330 
Ciliary body of, 340 
in hypermetropic eye, 342 
in myopic eye, 341 
Choroid, 338 
blood-vessels of, 339 
lamina chorio-capillaris of, 339 
lamina suprachoroidea of, 338 
nerves of, 340 
structure of, 338 
Conjunctiva, 380 
lymph-spaces of, 331 
Cornea, 331 
blood-vessels of, 333 
Bowman’s membrane of, 331 
Descemet’s membrane of, 338 
fibrse arcuate of, 332 
fixed corpuscles of, 332 
lamellae of, 331 
nerves of, 333 
preparation of, 334 
Eyelids, 328 
conjunctiva fornicis, 329 
conjunctiva tarsi, 328 
cilia of, 328 
Meibomian glands of, 329 
muscle of Muller, 329 
orbicularis palpebrarum, 328 
Eiolani’s muscle of, 329 
tarsus of, 328 
Fontana’s space of, 336 
Iris, 342 
blood-vessels of, 343 
dilator muscle of, 342 
ligament of, 336 
nerves of, 343 
sphincter of, 342 478 
INDEX, 
EYE— 
Iris, uvea of, 343 
Lachrymal gland, 351 
glandula Galeni of, 351 
glandula Monroi of, 351 
Lens, 350 
canal of Petit, 350 
ligament of, 350 
ligamentumpectinatum iridis, 335 
Optic nerve, 348 
blood-vessels of, 349 
circle of Haller, 349 
neuroglia of, 348 
subdural space of, 348 
vagina fibrosa of, 348 
Orbicularis ciliaris, 340 
Ora serrata, 840 
Retina, 343 
arteria centralis of, 347 
blood-vessels of, 347 
ganglion-cell layer of, 344 
inner granular layer of, 344 
inner nuclear layer of, 345 
layer of rods and cones of, 345 
macula lutea of, 344, 346 
membrana limitans externa of, 
345 
membrana limitans interna of, 
346 
outer granular layer of, 345 
outer layer of, nuclei of, 345 
pars ciliaris of, 347 
pigment layer of, 346 
preparation of, 347 
Schlemm’s canal, 336 
Sclera, 337 
lamina cribrosa of, 337 
perichoroidal space of, 337 
structure of, 337 
Tenon’s capsule of, 337 
tunica vasculosa of, 338 
venEe vorticosse of, 337 
vitreous body, 349 
fossa patellaris of, 350 
Fibrse arcuatte of cornea, 332 
Fibres, muscular, 128 
Fibrillation of cartilage, 83 
Fibrous cartilage, 86 
tissue, 66 
Filum terminale of spinal cord, 302 
Fimbriae of tongue, 380 
Fissure of "Rolando, 321 
of Sylvius, 321 
Fluid, spinal, 297 
Follicles of Lieberkuhn, 398 
of lymph-glands, 176 
of thymus, 412 
Fontana’s spaces, 336 
Foramen caecum of tongue, 383 
Formation of bone, 97 
of callus, 100 
Formatio reticularis of medulla oblongata, 
308 
Fossae nasales, 368 
Freezing section-cutter, 17 
French archil, 28 
Frog’s bladder, muscle of, 129 
Frommann’s lines, 113 
p ALACTOBLASTS, 451 
Galactophorous ducts, 441 
Gall-bladder, 197 
Ganglia, cerebral, 319 
Ganglia of spinal cord, 120 
Ganglionic bodies, 119, 121 
corpuscles of brain, 72 
Gas-chamber, 43 
Gelatinous tissue, 63 
Genital organs, female, 240 
male, 223 
Germinating endothelium, IGS 
Giant-cells, 95 
Gibbes’ double, triple, and quadruple 
staining, 26 
Giraldes, organ of, 231 
Gland, coccygeal, 158 
inter-carotid, 160 
lachrymal, 351 
pineal, 417 
thymus, 412 
thyroid, 415 
Glands, Bowman’s, of nose, 872 
lymphatic, 176 
1 Meibomian, 329 
Fallopian tubes, 246 
Fat-canals of cutis vera, 421 
Fat-cells of skin, 276 
Fat-columns of cutis vera, 421 
Fat-tissue, 73 INDEX. 
479 
Glands of Bartholine, 241 
of bile-ducts, 191 
of bronchi, 258 
of Brunner, 397 
of Cowper, 227 
of larynx, 256 
of middle ear, 355 
of small intestine, 366 
of tongue, 383 
peptic, 389 
pyloric, 391 
sebaceous, of skin, 285 
sudoriparous, 282 
Gians clitoridis, 241 
penis, 224 
Glandulae aberrantes mammae, 442 
Glandula Galeni, 351 
Monroi, 351 
Glandules of mouth, 378 
Glisson’s capsule, 183 
Glosso-pharyngeal root, 313 
Goblet cells, 60 
Gold, chloride of, 28 
Goll, column of, 298 
Graafian follicles, 248 
Granular layer of skin, 274 
Gray matter of spinal cord, 299 
Green coloration of nuclei, 25 
Growth, post-embryonal, of mamma, 453 
Hints regarding study of mamma, 455 
Horny teeth, 100 
Howship’s lacunae, 100 
Hyaline cartilage, 82 
Hydatid of Morgagni, 231 
Hymen, 241 
Hypermetropia, ciliary body in, 342 
Hypoglossal nucleus, 311 
TLLUMINATION, 4 
J- Induline, 27 
Infundibula of lung, 260 
Injecting fluids, 30, 32 
Injection of blood-vessels, 30, 31, 32 
of cutis vera, 424 
of kidney, 214 
of liver, 185 
of lymph-glands, 179 
of lymphatics, 169 
Instrument, care of, 7 
Intercarotid gland, 160 
Intercalated portions of renal tubules, 211 
Intercellular substance of cartilage, 83 
of connective tissue, 04 
Intermuscular tissue, 74 
Internal capsule of brain, 317 
Internal elastic coat of arteries, 152 
of veins, 157 
Internal ear, 357 
Internal fibrous coat of arteries, 153 
of veins, 157 
Intima of arteries. 152 
Invertebrates, muscle of, 133 
Involuntary muscle-fibre, 128 
Involuted mamma, histology of, 446 
lodized serum, 38 
Irrigation, method of, 41, 67 
Iris, 342 
diaphragm, 5 
Island of Beil, 322 
Ivory, 103 
53 
Haemoglobm, 53 
Haem at oblasts, 47 
Haematometers, 50, 53 
Haematoxylon, preparation of nerves in, 
118 
solution, 23, 24 
Hailes’s microtome, 19, 20 
Hair, 288 
Haller, circle of, 349 
circulus venosus of, 442 
Hamilton’s preservative fluid, 20 
Hand section-cutter, 16 
Hardening of brain, 15 
Haversian*canals of bone, 91 
Heart, muscular fibres of, 140 
Heidenhain, rods of, 207 
Henson’s prop-cells, 366 
Hepatic artery, 186 
cells, 189 
TYARYOKINESIS, 237 
Keyes’s method of counting blood' 
globules, 51 
KIDNEY, 201 
afferent vessel of, capsule of, 206 
blood-vessels of, 213 
Bowman’s capsules of, 204 
calyx of, 216 480 
INDEX. 
KlDNEY— 
capsule of, 216 
collecting tubules of, 205 
convoluted tubes of, 205 
efferent vessel of capsules of, 206 
epithelium of collecting tubules, 211 
of looped tubules of, 210 
of tubules of, 206 
general plan of structure of, 201 
boundary layer, 201 
cortex, 201 
medulla, 201 
medullary rays, 201 
injection of, 214 
intercalated portions of tubules of, 
211 
looped tubules of, 209 
lymphatics of, 216 
membrana propria of tubules of, 203 
method of preparing sections of, 208 
natural injection of tubules of, 216, 
220 
nerves of, 216 
rods of Heidenhain, 207 
stroma of, 215 
tubules of, 203 
vasa recta of, 214 
Kleinenburg’s hEematoxylon, 23 
Klein’s hsematoxylon, 24 
Klein’s method of studying the omentum, 
166 
Kuhnt, hohlcylinder of, 114 
Lenses, high, testing of, 10 
kinds of, 6 
measuring angle of, 10 
testing of, 8 
Leucocytes, 39, 48 
Lieberkiihn’s follicles, 398 
Ligament of iris, 336 
of lens, 350 
Ligaments of larynx, 253 
Ligamentum pectinatum iridis, 335 
Light, direct, 5 
oblique, 5 
Liquor sanguinis, 34 
LIVER, 183 
acini of, 183 
bile-ducts, capillary, 192 
Mayer’s views on, 196, 197 
natural injection of, 193 
walls of, 196 
bile-ducts, larger, 191 
blood-vessels of, 186 
capsule of, 183 
cells of, 189 
central veins of, 184 
connective tissue of, 188 
cystic duct, 198 
ductus communis, 198 
fat-droplets in cells of, 190 
gall-bladder, 197 
coats of, 198 
glands of bile-ducts, 191 
Glisson’s capsule of, 183 
general plan of structure of, 183 
hepatic artery, 186 
hepatic lobules, 183 
injection of, 185 
interlobular septa of, 188 
interlobular veins of, 184 
intermediate canals of, 184 
intralobular veins of, 184 
lymph-vessels of, 198 
nerves of, 199 
sublobular veins of, 185 
Lobule, paracentral, 323 
Lobules of liver, 183 
Lobulettes of lung, 260 
Locus cseruleus, 315 
niger, 316 
Looped renal tubules, 207 
Lumbar enlargement of spinal cord, 303 
Lungs, 257 
T ABIA MAJORA, 240 
minora, 240 
Labium tympanicum, BG4 
vestibulare, 364 
Labyrinth, 358 
Lachrymal gland, 351 
Lacunas, Howship’s, 100 
Lacunas of bone, 91 
Lamellae of bone, 90 
Lamina chorio-capillaris, 339 
cribrosa of sclera, 337 
reticularis of ear, 366 
spiralis, 362 
suprachoroidea, 338 
Large intestine, 400 
Larynx, 253 
Lens, 350 INDEX, 
481 
Lunula of nails, 294 
Luschka’s gland, 158 
Lymphangeal nodules, 167 
tracts, 167 
Lymphatic glands, 176 
Lymphatics of bladder, 481 
of blood-vessels, 161 
of kidney, 216 
of large intestine, 401 / 
of larynx, 257 
of liver, 198 
of lung, 264 
of mamma, 443 
of mouth, 379 
of oesophagus, 388 
of pancreas, 411 
of small intestine, 399 
of spleen, 409 
of stomach, 393 
' of suprarenals, 436 
of testis, 234 
of thymus, 414 
of thyroid, 416 
LYMPHATIC SYSTEM, 163,459 
artificial injection of lymphatics, 169 
cysternso lymphaticae, 170 
development of fat-tissue, 168 
endolymphangeal tracts, 167 
endothelium and stomata, 169 
general histology of, 164 
germinating endothelium of, 165 
glands of, 175 
adenoid or reticular tissue of, 
178 
afferent and efferent branches of, 
176 
follicles of, 176 
injection of, 179 
lymphoid corpuscles of, 178 
medulla and cortex of, 176 
methods of studying, 179 
nerves of, 179 
Ranvier’s plan of injection of, 180 
sinuses of, 177 
stroma of, 176 
vessels of, 179 
Klein’s method of studying omentum, 
166 
lymphangeal nodules or patches of, 
167 
lymphangeal tracts of, 167 
LYMPHATIC SYSTEM— 
lymphatic radicles, course and ter- 
mination of, 168 
lymphatics, 175 
development of, 175 
of mesentery, 165 
of tendons, 175 
lymphatic vessels, 172 
intimate structure of, 173 
topographical peculiarities of, 174 
variations in shape of, 173 
lymph-spaces, 175 
subarachnoid and subdural, 175 
modern views on, 163 
nerves of peritoneum, 172 
perilymphangeal tracts, 167 
plasma-cells, 164 
plasmatic channels, 165 
pseudo-stomata, 171 
Ranvier’s taches laiteuses, 168 
views on false stomata, 170 
relations to connective tissues, 163 
retrospective view of, 181 
sap-canaliculi of, 165 
stomata of, 165 
stomata vera of, 171 
thoracic duct, 174 
Lymphoid cells of brain, 72 
Lymphoid corpuscles of connective tissue, 
67 
of lymph-glands, 178 
of skin, 277 
Lymph-spaces, subarachnoid, 175 
Lymph-vessels of penis, 234 
Macula acustica, seo 
lutea, 344, 346 
Malassez’s method of counting blood-cor- 
puscles, 50 
Malpighian corpuscles of spleen, 404 
layer of skin, 271 
Mammary epithelium, 444 
MAMMARY GLAND, 439 
areola of, 442 
blood-vessels of, 442 
circulus venosus of Haller of, 442 
colostrum bodies, or corpuscles of 
Donne, 450 
development of, 452 
Driisenfeid, 452 482 
INDEX. 
MAMMARY GLAND— 
ectasia of milk-ducts, 453 
galactoblasts of, 451 
galactophorous ducts of, 441 
general considerations on, 439 
glandulae aberrantes of, 443 
growth of, 453 
Creighton’s views on, 454 
Harderian gland, similarity with, 449 
lymphatics of, 443 
membrana propria of, 449 
milk-globules, 451 
milk-reservoirs of, 441 
nerves of, 443 
nipple or mamilla of, 440 
Partsch’s views on milk-secretion, 451 
Ranker’s views on the mamma and 
the lacteal secretion, 450 
structure of fully expanded gland, 444 
acini of, 444 
Creighton’s views on, 445 
epithelium of, 444 
plasma-cells of, 444 
yellow cells of. 444 
structure of involuted mamma, 446 
Creighton’s account of, 446 
epithelium of, 446 
vacuolation of epithelium of, 447 
study of, 455 
Stutzzellen of, 449 
Wendt’s views on secretion of milk, 
449, 451 
Mammilla, 440 
Marrow of bone, 95 
Measurement of red blood-corpuscles, 35 
Meatus auditorius externus, 353 
urinarius of female, 348 
of male, 226 
Media or musculosa of arteries, 154 
Medulla of suprarenal capsules, 435 
oblongata, 307 
of kidney, 201 
Medullary rays of kidney, 201 
Meibomian glands, 329 
Meissner’s plexus, 123, 399 
Membrana basilaris of ear, 364 
limitans olfactoria, 373 
propria of mamma, 449 
propria of renal tubules, 203 
tectoria of ear, 866 
tympani, 354 
Membrane of Bowman, 79 
of Corti, 866 
of Descemet, 79 
of Reissner, 363 
Meninges of brain, 331 
of spinal cord, 896 
Metallic solutions, 88, 89 
Metaplastic bone, 98 
Methods for preparing objects, 18 
of preparing tissues, 14 
of studying hyaline cartilage, 84 
of studying spinal cord, 305 
Methyl-green, 89 
and induline, 87 
Micrometer, stage, 7 
Microscope, how to use, 4 
testing of, 7 
Microtome, Hailes’, 19, 30 
Vincent’s, 81 
Middle ear, 355 
Milk-ducts, 444 
Milk-globules, 451 
Milk-reservoirs, 441 
Miller's picro-carmine, 83 
Mirrors, 5 
Modiolus, 363 
Moist chamber, 48, 43 
Molybdate of ammonia, 15 
Morgagni, hydatid of, 331 
Motor tract of hemispheres, 323 
MOUTH AND TONGUE, 377 
Mouth, 377 
blood-vessels of, 379 
epithelium of, 377 
glandules of, 878 
lymphatics of, 379 
nerves of, 379 
submucous tissue of, 377 
tunica propria of, 377 
Tongue, 380 
circumvallate papillae of, 383 
glands of, 383 
filiform papillae of, 380 
fimbriae of, 380 
foramen coecum of, 383 
fungiform papillae of, 381 
papillae foliatae of, 383 
taste-goblets of, 381 
Mucous membrane of larynx, 855 
of oesophagus, 386 
of small intestine, 395 INDEX, 
483 
Mucous membrane of stomach, 389 
Mucous tissue, 63 
Muscle, 128 
Oohnheim’s areas of, 136 
columns of, 138 
conclusions regarding structure of, 137 
fibres of, 128 
of frog’s bladder, 129 
of fly, 133 
of heart, 140 
of human embryo, 132 
of invertebrates, 133 
of the “lucky bug” or gyrinus, 
134 
of water-beetles, 133 
NASAL FOSSAE, PHARYNX, and TON- 
SILS, 368 
Nasal Fossae, 368 
Bowman’s glands of, 372 
indifferent cells of, 371 
membrana limitans, olfactoria of, 
372 
mucous membrane of, 368 
olfactory cells of, 371 
olfactory epithelium of, 371 
olfactory nerves of, 372 
olfactory region of, 370 
thicker membrane of, 369 
thinner membrane of, 369 
respiratory region of, 368 
vestibulum nasi, 368 
Pharynx, 373 
mucous membrane of, 373 
pharyngeal tonsil of, 373 
Tonsils, 373 
involuntary, 128 
nuclei and corpuscles of, 136 
peculiarities of, associated with differ- 
ent functions, 138 
polarized light for the study of, 137 
red and white, of rabbit’s leg, 138 
sarcolemma, 130 
striation of fresh, fibre, 131 
study of contraction of, 135 
termination of, in tendon, 139 
transverse sections of, 136 
vascular supply of, 138 
voluntary fibre, 130 
of Muller, 329 
of Riolani, 329 
termination of nerves in, 125 
Muscles of skin, 287 
Muscular coat of oesophagus, 387 
of small intestine, 394 
of stomach, 388 
fibres of heart, 140 
Muscularis mucosae of oesophagus, 387 
of small intestine, 396 
of stomach, 389 
Musculosa of arteries, 154 
Muller’s fluid, 14 
muscle, 329 
Myelinic fibres of spinal cord, 301 
nerve-fibres, 109, 116 
Myeloplaxes, 95 
Myopia, ciliary body in, 341 
Natural injection of liver, 193 
of kidney, 216, 220 
Nerve-elements of spinal cord, 299 
Nerve-fibres, varieties of, 109 
Nerves of bladder, 431 
of blood-vessels, 161 
of choroid, 340 
of cornea, 333 
of iris, 343 
of kidney, 216 
of large intestine, 401 
of larynx, 257 
of liver, 199 
of lung, 265 
of lymph-glands, 179 
of mamma, 443 
of mouth, 879 
of oesophagus, 388 
of ovary, 248 
of pancreas, 411 
of penis, 225 
of peritoneum, 172 
of skin, 279 
of small intestine, 399 
of spleen, 409 
of stomach, 393 
of suprarenals, 436 
of thyroid, 416 
of uterus, 245 
olfactory, 372 
Naboth, ovuia of, 244 
Nail-fold, 294 
Nails, 293 
Naphthaline yellow, 27 
Nerve-terminations, 109 484 
INDEX. 
NERVOUS SYSTEM, 109 
Auerbach’s plexus, 123 
axis-cylinder, 110 
connective tissue of nerves, 126 
Deiter’s protoplasmic processes, 120 
Doyere’s eminence, 126 
endoneurium, 125 
epineurium, 126 
fibres of Remak, 117, 118 
preparation of, in hsematoxylon, 
118 
Frommann’s lines, 113 
ganglia of cranial and spinal nerves, 
130 
ganglia of spinal cord, examination 
of, 120 
ganglionic bodies, 119 
of human brain, 121 
of sympathetic system, 121 
Gasserian ganglion, examination of, 
in frog, 120 
general histology of, 109 
hohlcylinder of Kuhnt, 114 
incisions of Schmidt, 111 
Meissner’s plexus, 123 
methods of nerve-termination, 109 
motorial plate, 126 
myelinic fibres, 109 
nerves, modern conceptions of, 
116 
myeline or medulla, 110 
Pacinian bodies, 124 
perineurium, 127 
preparation by bichromate of am- 
monia, 115 
preparation in osmic acid and picro- 
carmine, 118 
Ranvier’s nodes, 110 
sheath of Schwann, 110 
spiral fibre of Beale, 123 
staining of, in osmic acid, 113 
staining of, in picro-carmine, 111 
staining of, with silver nitrate, 
112 
tactile corpuscles, 134 
termination of nerves, 123 
in muscle, 125 
in epithelial bodies, 126 
varieties of nerve-fibres, 109 
Nervous system, central, 296 
Network of epithelial cells, 61 
Neumann, dentinal sheath of, 104 
Neuroglia, 70, 71 
fibrillae of, 72 
of optic nerve, 348 
of spinal cord, 298 
Nipple, 440 
Nitrate of silver, 29 
staining of nerves with, 112 
Norris and Shakespeare’s method of dou 
ble staining, 33 
Nose, 368 
Nose-piece, 5 
Nuclei, green coloration of, 25 
of muscle, 136 
Nucleus and root of abducens, 314 
lenticularis of brain, 316 
of hypoglossus, 311 
parolivary, 311 
OBJECT, arrangement of, 6 
size of, 8 
Oblique light, 5 
Odontoblasts, 104 
Odontomata, 105 
(Esophagus, 386 
Olfactory epithelium, 371 
nerves, 373 
region, 370 
Olivary body, 310 
Optic nerve, 348 
thalami, 319 
Ora serrata, 340 
Orbicularis ciliaris, 340 
palpebrarum, 338 
Organ of Corti, 363, 364 
of Giraldes, 831 
ORGANS OF GENERATION, FEMALE, 
340 
Clitoris, 340 
corpora cavernosa of, 841 
genital nerve corpuscles of, 840 
glans of, 341 
Glands of Bartuoline, 241 
Hymen, 241 
Fallopian Tubes, 346 
ampulla of, 246 
fimbriae of, 246 
isthmus of, 246 
Labia majora, 240 
Labia minora, 240 485 
INDEX. 
ORGANS OF GENERATION, FEMALE— 
Ovary, 346 
ORGANS OF GENERATION, MALE— 
Scrotum, 281 
blood-vessels of, 247 
corpus albicans of, 250 
corpus luteum of, 249 
development of, 250 
Graafian follicles of, 248 
nerves of, 248 
stroma of, 246 
tubes of, 246 
Parovarium, 250 
Placenta, 251 
Urethra, 242 
meatus urinarius of, 242 
Uterus— 
changes of, during menstruation 
and gestation, 245 
decidua, 245 
glands of, 244 
mucous membrane of, 243 
plicae pal matte of, 243 
nerves of, 245 
os uteri, 244 
ovula Nabothi, 244 
vessels of, 245 
Vagina, 241 
vascular system of, 242 
Vestibule, 241 
bulbi vestibuli, 241 
ORGANS OF GENERATION, MALE, 223 
Cowper’s Glands, 227 
Epididymis, 231 
blood-vessels of, 234 
Ejaculatory Ducts, 235 
Hydatid of Morgagni, 231 
karyokiuesis, 237 
Organ of Giraldes, 231 
Penis, 223 
blood-vessels of, 224 
genital nerve-corpuscles of, 225 
glans penis, 224 
lymph-vessels of, 224 
nerves of, 225 
tunica albuginea of, 223 
Tyson’s glands of, 224 
Prostate Gland, 227 
acini of, 228 
blood-vessels of, 229 
epithelium of, 228 
nerves of, 229 
vesicula prostatica of, 229 
dartos of, 231 
semen or sperma, 235 
seminal vesicles, 235 
spermatoblasts, 236 
Spermatozoa, 225 
structure of, 236 
development of, 236 
Testicles, 229 
blood-vessels of, 234 
corpus Highmori of, 230 
lymphatics of, 234 
mediastinum of, 230 
nerves of, 234 
rete testis, 231 
seminiferous tubules of, 231, 233 
septula of, 230 
tunica adnata of, 230 
tunica albuginea of, 230 
tunica vaginalis communis of, 230 
Urethra, 225 
colliculus seminalis of, 225 
lacunas Morgagnii of, 226 
lymphatics of, 227 
meatus urinarius of, 226 
membranous portion of, 226 
musculus urethralis of, 226 
nerves of, 226 
papillae of, 226 
prostatic portion of, 225 
spongy portion of, 226 
structure of, 225 
vas aberrans, 232 
Vas defekens, 232, 233 
ampulla of, 232 
muscular coat of, 234 
nerves of, 234 
Organs of respiration, 253 
Osmic acid, staining of nerves with, 113 
Osmic acid and picro-carmine, preparation 
of nerves in, 118 
Osmic and chromic acids, 15 
Osmic and oxalic acids, staining with, 28 
Ossification, points of, 98 
Osteoblasts, 96, 98 
Osteoclasts, 100 
Osteo- or vaso-dentine, 105 
Osteoporosis, 9 
Os uteri, 244 
Otoliths, 358 486 
INDEX. 
Ovary, 246 
Oviducts, 246 
Ovula Nabobhi, 244 
Plasma of connective tissue, 67 
of mamma, 444 
Plasmatic channels, 165 
Pleura, 265 
Pleural appendages, 267 
Plexus, choroid, 320 
of Auerbach, 399 
of Meissner, 399 
Polarized light in the study of muscle 
137 
Pons varolii, 315 
Potassium bichromate solution, 14 
Preparation of bone, 92 
of cornea, 834 
of fresh object, 13 
of tissues, 13, 14 
of mamma, 455 
of microscopic objects, 12 
of retina, 347 
spleen, 409 
Preserving fluid, Wickersheimer’s, 29 
Preservative fluid, Hamilton’s, 20 
Prickle cells, 58 
of skin, 272 
Prop-cells, Henson’s, 366 
Prostate gland, 227 
Pseudostomata, 171 
of pulmonary lymphatics, 264 
Pulp of spleen, 406 
of teeth, 102, 105 
Purpurine for staining cartilage, 85 
Purkinje, cells of, 318 
granular layer of, 104 
Purpurine, 28 
Pyloric glands, 391 
Radicles of lymphatics, 168 
Ramification of capillaries, 149 
Ranvier’s nodes, 110 
purpurine, 28 
laches laiteuses, 168 
Raphe of medulla oblongata, 309 
Rauber’s views on the mamma, 450 
Rectum, 401 
Red blood-corpuscles, 34 
Reil, island of, 322 
Reissner, membrane of, 362 
Remak, fibres of, 117 
Renal pelvis, 428 
tubules, 203 
pACINIAN BODIES, 134 
Pancreas, 410 
acini of, 420 
blood-vessels of, 411 
centro-acinal cells of, 411 
development of, 412 
excretory duct of, 411 
lymphatics of, 411 
nerves of, 411 
trypsin, 410 
zymogen, 410 
Panniculus adiposus, 277 
Papillae of cutis vera, 421 
of hair, 289 
of tongue, 880 
Papillary sphincter, 429 
Paracentral lobule, 823 
Parenchymatous cartilage, 83 
Parolivary nucleus, 311 
Parovarium, 250 
Partsch’s views on secretion of milk, 451 
Pavement endothelium, 80 
Pelvis, renal, 428 
Penis, 223 
Peptic glands, 389 
Perichondrium, 86 
Perineurium, 126 
Periodontium, 108 
Periosteum, 95 
Perithelium, 148 
Perivascular spaces, 161 
Petit, canal of, 350 
Peyer’s patches, 396 
Pharyngeal tonsil, 373 
Pharynx, 873 
Pia mater, spinal, 297 
Picro-carmine, 23 
staining of nerve-fibres with, 111 
Picro-hasmatoxylon and eosine, 26 
Pigmented epithelium, 58 
Pigment of retina, 346 
Pineal gland, 417 
Pituitary body, 417 
Placenta, 251 
Plasma, 34 
cells, 164 INDEX. 
487 
RESPIRATORY TRACT, 258 
Larynx, 253 
calcification of cartilages of, 255 
cartilages of, 254 
cartilage triticea of, 253 
corniculum of, 255 
epiglottis of, 255 
glands of, 256 
ligaments and membranes of, 253 
lymphatics of, 257 
mucous membrane of, 255 
nerves of, 257 
Santorini’s cartilages of, 255 
vocal cords of, 254 
Wrisberg’s cartilages of, 255 
Lungs, 259 
acini or lobulettes of, 260 
alveolar passages of, 260 
alveoli or air-cells of, 260 
blood-vessels of, 263 
bronchioles of, 260 
epithelium of alveoli of, 261 
infundibula of, 260 
lymphatics of, 264 
nerves of, 265 
pleural appendages, 267 
pleura of, 265 
pseudostomata of lymphatics of, 
264 
septa of, 262 
smaller bronchi, 259 
subpleural lymphatics, 237 
terminal arteries of, 263 
Trachea and Primary Bronchi, 257 
cartilage rings of, 257 
glands of, 258 
mucous membrane of, 257 
Rete Malpighii, 271 
Reticular or yellow elastic cartilage, 85 
Reticular form of connective-tissue, 66 
Retina, 342 
Retzius, stripes of, 103 
Riolani’s muscle, 329 
Rolando, fissure of, 321 
Root of hair, 288, 292 ; of nail, 294 
Sarcolemma, 130 
Satterthwaite’s section-cutter, 17 
Scala tympani, 362 
vestibuli, 362 
Scales of epidermis, 275 
Schlemm’s canal, 836 
Schmidt, incisures of, 111 
Schreger, lines of, 105 
Schwann, sheath of, 110 
Sclera, 337 
Scrotum, 231 
Sebaceous glands, 285 
Section-cutters, 16, 17 
Semen, 235 
Semicircular canals, 359 
Seminal vesicles, 235 
Seminiferous tubules, 231 
Septa of lung, 262 
Shaft of hair, 288, 292 
Sharpey’s fibres of bone, 94 
Sheath of Schwann, 110 
Sheaths of hair, 289 
Silver, nitrate of, 29 
Sinuses of lymph-glands, 177 
Size of object, 8 
SKIN, 269 
blood-vessels of, 279 
Corium op, 277 
pars papillaris, 278 
pars reticularis of, 278 
corneous layer of, 274 
elastic tissue fibres of, 277 
epidermic scales, 275 
Epidermis, 271 
general plan of arrangement of, 
269 
general structure of, 270 
granular layer of, 274 
Hair, 288 
development of, 293 
papillae of, 289 
root of, 288, 292 
shaft of, 288, 292 
sheaths of, 289 
lymphoid corpuscles of, 277 
muscles of, 287 
Nails, 293 
bed of, 294 
body of, 294 
development of, 294 
lunula of, 294 
SACCULE of labyrinth, 358 
Salivary glands, the, 461 
Salter, incremental lines of, 105 
Santorini's cartilage, 255 
Sap-canallculi, 165 488 
INDEX. 
SKIN— 
Nails— 
Striation of muscle, 131 
Stroma of kidney, 215 
Stutzzellen of mamma, 449 
Subdural spaces of optic nerve, 348 
Submucous layer of oesophagus, 387 
of small intestine, 396 
of stomach, 389 
Subpleural lymphatics, 267 
Sudoriferous glands, 282 
Suprarenal Capsules, 431 
blood-vessels of, 436 
capsule of, 432 
cortical substance of, 432 
external layer of, 433 
internal layer of, 435 
middle layer of, 433 
zona fasciculata of, 433 
zona glomerulosa of, 433 
zona reticularis of, 436 
development of, 436 
lymphatics of, 436 
medullary substance of, 435 
nerves of, 436 
Sweat-glands, 282 
Sylvian fissure, 321 
Sympexions of thyroid, 415 
nail and fold, 294 
root of, 294 
nerves of, 279 
panniculus adiposus of, 276 
rete Malpighii, 271 
prickle cells of, 272 
Sebaceous Glands op, 285 
development of, 286 
stratum lucidum of, 274 
stratum subpapillare of, 279 
subcutaneous connective-tissue layer 
of, 278 
fat-cells of, 276 
Sweat-Glands op, 282 
development of, 285 
tactile corpuscles of, 280 
Slide for heating, 40 
Small intestine, 394 
Sperma, 235 
Spermatoblasts, 236 
Spermatozoa, 235 
Sphincter of iris, 342 
ani, 401 
papillary, 429 
vesicse, 430 
Spinal cord, 298 
fluid, 397 
Spina’s views on cartilage, 87 
Spleen, 403 
blood-vessels of, 407 
development of, 409 
fibrous coat or capsule of, 404 
general structure of, 403 
lymphatics of, 409 
Malpighian corpuscles of, 404 
nerves of, 409 
preparation of, 409 
pulp of, 406 
serous coat of, 403 
Squamous epithelium, 57 
Stage diaphragms, 5 
micrometer, 7 
Stevenson, plan of imbedding, 16 
Stomach, 388 
Stomata of lymph-vessels, 165 
vera, 171 
Stratum intermedium of tooth, 108 
lucidum of skin, 274 
subpapillare of skin, 279 
rmCTILB CORPUSCLES, 124 
Tarsus of eye, 328 
Taste-globlets of tongue, 381 
TEETH, 102 
cement of, 105 
dentinal canals of, 104 
dentinal globules of, 104 
dentinal fibres of tomes, 104 
dentinal sheath of Neumann, 104 
dentine or ivory, 103 
development of, 105 
cuticula, 107 
dentinal teeth, 106 
dentine, 106 
homy teeth, 106 
primary enamel organ, 107 
secondary enamel organ, 107 
stratum intermedium of, 108 
tooth papilla, 107 
tooth-sac, 107 
development of enamel of, 108 
enamel, 102 
granular layer of Purkinje, 104 INDEX. 
489 
TEETH— 
Tissue, elastic, 77 
incremental lines of Salter, 105 
interglobular spaces of Czermak, 103 
interglobular substance, 105 
fat, 73 
fibrous, 66 
gelatinous, 63 
intermuscular, 74 
mucous, 63 
tendon, 72 
lines of Schreger, 105 
parallel stripes of Retzius, 103 
parts of, 102 
periodontium of, 108 
pulp of, 102, 105 
odontoblasts, 104 
odontomata, 105 
osteo- or vaso-dentine, 105 
Tendons, lymphatics of, 175 
Tendon-tissue, 72 
Tenon’s capsule, 337 
Termination of muscle in tendon, 139 
Testicles, 229 
Testing lenses, 8, 10 
microscope, 7 
Thalami optici, 319 
THICK CUTIS VERA, 420 
blood-vessels of, 423 
erector pili muscles of, 422 
fat-columns or fat-canals of, 421 
fibrous prolongations of, 420 
injection of, 424 
lymphatics of, 424 
papillae of, 421 
Third corpuscular element of blood, 48 
Thoracic duct, 174 
THYMUS GLAND, 412 
blood-vessels of, 414 
capsule of, 412 
cells of, 413 
central canal of, 414 
development of, 414 
follicles of, 412 
lymphatics of, 414 
thymic juice of, 413 
THYROID BODY, 415 
blood-vessels of, 416 
capsule of, 415 
epithelium of, 415 
lymphatics of, 416 
nerves of, 416 
sympexions of, 416 
vesicles of, 415 
Tissue, adenoid, 69 
cellular, 63 
connective, 63 
corneal, 75 
Tissue, compact, of bone, 89 
Tomes, dentinal fibres of, 104 
Tongue, 380 
Tooth-sac, 107 
Tonsil, pharyngeal, 373 
Tonsils, 373 
Trachea, 257 
Triple staining, 26 
Trypsin, 410 
Tubules of kidney, 203 
Tubules, seminiferous, 231 
Tunica vasculosa of sclera, 338 
Tympanum, 354 
Types of arteries, 152 
Tyson’s glands, 224 
TTRETERS, 429 
Urethra, female, 342 
male, 225 
URINARY EXCRETORY PASSAGES, 
428 
Bladder, 430 
blood-vessels of, 431 
epithelium of, 430 
connective tissue of, 430 
detrusor urinae of, 430 
lymphatics of, 431 
muscular coat of, 430 
nerves of, 431 
sphincter vesicas, 430 
Renal Pelyis, 428 
fibrous layer of, 429 
mucous membrane of, 428 
muscular coat of, 429 
papillary sphincter of, 429 
vessels and nerves of, 429 
Ureters, 429 
mucous membrane of, 429 
muscular layers of, 429 
vessels and nerves of, 429 
Uterus, 243 
Utricle of labyrinth, 358 
Urea, 343 490 
INDEX, 
VACUOLATION of mammary epithe 
Hum, 447 
Vagina, 241 
Valves of veins, 158 
Valvulae conniventes, 395 
Vas aberrans, 232 
Vasa recta of kidney, 214 
Vas deferens, 282 
Vasa vasorum, 161 
Veins, 156 
central, of liver, 184 
interlobular, of liver, 184 
intralobular, of liver, 184 
sublobular, of liver, 185 
Tense vorticosse of sclera, 337 
Ventricles of brain, 319 
Venules, 156 
Vermiform appendix, 401 
Vertebrates, muscle of, 130 
Vesical epithelium, 430 
Vesiculse seminales, 235 
Vessels of muscle, 138 
Vestibule of vagina, 241 
Vestibulum nasi, 368 
Villi of intestine, 395 
Vincent’s microtome, 21 
Violet de Paris, 29 
Vitreous body, 349 
Vocal cords, 254 
Voluntary muscle-fibre, 130 
WARM-SLIDE, 40 
’' Waxy change, methyl-green for, 29 
Wendt, method of triple staining, 26 
views on endothelial desquamation, 
147 
views on secretion of milk, 449, 451 
White blood-globules, 39, 48 
White substance of spinal cord, 299 
Wickersheimer’s preserving fluid, 29 
Wrisberg’s cartilage, 255 
"YELLOW CELLS of mamma, 444 
170XA FASCICULATA of suprarenal, 
433 
glomerulosa, 433 
reticularis, 433 
pectinata of ear, 366 
Zymogen, 410 
APPENDIX A. 
The Lymphatic System, 459. 
New methods, 459. 
Views of G. and E. E. Hoggan, 459. 
Blood-vessels of, 467. 
Excretory ducts of, 466. 
Nerves of, 467. 
Secreting cells of, 463 
1. Albuminous glands, 468. 
2. Mucous glands. 464. 
APPENDIX B. 
The Salivary Glands, 461. 
Intra-alveolar reticulum, 468. 
Acini of, 462.