'Physiology Kifi°SSL / Narcotics. a, ones 53 VI. Physiology of the Bones 56 VII, Joints 58 VIII. Varieties of Joints 61 IX. Fontanelles 63 X. Hygiene of the Bones 65 XI. The Vertebrae 70 XII. Cranial or Head Bones 76 XIII. Bones of the Face 78 XIV. Ribs and Sternum 80 XV. The Shoulder-girdle and Upper Extremities 82 XVI. Pelvic Girdle 86 XVII. Table of Bones in the Human Body . 93 CHAPTER Y. I. The Heart •• 103 11. Valves of the Heart 106 111. The Arteries 112 IV. The Capillaries 116 V. The Veins 118 VI. Influence of Alcohol on the Vascular System 121 THE VASCULAR SYSTEM. CHAPTER VI. RESPIRATION. I. Respiration Defined 131 11. The Lungs 133 111. Air, and its Relation to the Action of the Lungs 143 IV. Superior Costal,.lnferior Costal, and Abdominal Respiration. 148 CHAPTER VII. I. The Muscles Defined 156 11. Subdivisions of the Muscles 160 111. Physical Character of the Muscles 164 IV. Involuntary Muscles 174 THE MUSCLES. CONTENTS. CHAPTER VIII. ANATOMY AND PHYSIOLOGY OF THE NERVOUS SYSTEM. SECTION PAGE I. Composition and Division of Nervous Tissue 181 11. Nerve-fibres 184 111. Method of Termination of Motor and Sensory Nerves . . . 189 IV. Nerve-cells 195 V. The Brain and Spinal Cord 200 VI. Surrounding Membranes 208 THE ACTION OF ALCOHOL AND NARCOTICS ON THE NERV- OUS SYSTEM. CHAPTER IX. I. Effects of Prolonged Use # 215 CHAPTER X. THE ALIMENTARY CANAL. I. Structure and Function of the Alimentary Canal 226 11. The Alimentary Canal defined 231 111. The Several Organs in the Line of the Alimentary Canal . 247 IV. Classification of Alimentary Principles 252 Y. Important Articles of Food 258 VI. The Digestive Fluids 275 CHAPTER XI. SENSE-ORGANS AND SPECIAL SENSES. I. Olfaction, or the Sense of Smell ...*.. 300 11. Gustation, or the Sense of Taste 305 CHAPTER XII. I. The Eye 310 VISION. CONTENTS. CHAPTER XIII. SECTION PAGE I. The Ear 329 AUDITION, OR HEARING. CHAPTER XIV. SECRETION AND EXCRETION 336 I. The Kidneys 339 CHAPTER XV. ON THE INTEMPERATE USE OF ALCOHOL 34? APPENDIX. Emergencies, and How to Meet Them 353 Table of the Muscles of the Human Body 361 Notes 394 Glossary 401 Indkx 415 LIST OF ILLUSTRATIONS. FIG. PAGE 1. White Blood-cells 11 2. Blood-plaques and Rapid Formation of Clot 18 3. The Phenomena of Coagulation 22 4. Red Blood-cells 31 5. Connective-tissue Cells 40 6. Hyaline Cartilage 42 7. Fibro-cartilage 43 8. Bones of the Wrist and Hand 48 9. Parietal Bones 50 10. The Skeleton 52 11. Magnified Transverse Section of Compact Bone ... 54 12. Magnified Vertical Section op Compact Bone .... 55 13. Bones showing the Formation of the Right Elbow-joint. 57 14. Showing Ligaments of Ankle and Foot 59 15. Showing Left 'Knee-joint . . 60 16. Skull showing Sutures 62 17. Fcetal Skull showing the Fontanelles and Centres of Ossification of the Bones 64 18. Normal Thorax, Vertebral Column, and Pelvis . .67 19. Result of a Badly-set Fracture 68 X LIST OF ILLUSTRATIONS. FIG. , PAGE 20. Vertebrae 71 21. Occipital Bone and First Cervical Vertebra .... 73 22. Pelvic Bones 75 23. Left Shoulder-joint 83 24. Right Elbow-joint, Anterior View . ■ 84 25. Elbow-joint of Left Side, Internal View 85 26. Showing Bones and Ligaments op the Wrist and Hand. 87 27. Hip-joint 89 28. Bones of the Right Foot and Leg 90 29. Femur or Thigh-bone of an Adult 91 30. Femur of Child, showing the Parts before Ossification is Complete 92 31. The Heart 105 32. Heart with Anterior Surface cut away, showing its Cavities, Valves, etc 109 33. Pelvic Bones, Femur or Thigh-bone, Artery, etc. . . .113 34. Clavicle, Artery, Vein, Bone op the Arm, etc 115 35. Artery, showing its Coats and Branches 117 36. Superficial Veins of Upper Extremity uniting to Form a Large Vein 119 37. Veins, Arteries, Arm, and Forearm 120 38. Method of applying Tourniquet 125 39. Application of Tourniquet to Arm 126 40. Diagram of the Heart and Lungs 134 41. Showing the Relation of the Organs in the Thoracic and Abdominal Cavities 136 42. Epiglottis, Rings of the Trachea, Hyoid Bone, etc. . .138 43. Pulmonary Lobules, Bronchi, Trachea, Intercostal Muscles, etc 140 LIST OF ILLUSTRATIONS. FIG. PAGE 44. Representing the Termination of a Small Bronchial Tube, and Three Collections of Air-cells 342 45. A Solidified Lung as it occurs in Pneumonia 150 46. Diagram showing the Effects of Tight Lacing in Early Life 152 47. Muscles of Head, Neck, Face, and Ear 163 48. Poupart’s Ligament, Crest of the Ilium, and Muscles of the Leg 165 49. Left Arm, Anterior View, Superficial Muscles of the Shoulder, Arm, Forearm, and Hand 166 50. Right Arm, Superficial Muscles represented as cut away 168 51. Representing the Structure of Muscle-fibres and Cells. 170 52. Nerve-fibres and Nerve-cells 182 53. Multipolar branching Nerve-cell, showing the Nucleus and Nucleolus 196 54. Vertical Section of the Brain in the Median Line . 200 55. Surface of the Brain, viewed from Above 201 56. Brain colored to show the Different Cortical Areas. 203 57. Transverse Section of the Spinal Cord 208 58. Representing Part of the Bony Wall of the Cranium REMOVED TO SHOW THE FALX CEREBRI AND VENOUS SINUSES. 209 59. Dog, showing Gastric Fistula 230 60. Showing the Organs composing the Alimentary Canal. 233 61. Showing the relation of the Teeth to the Jaw-bones. 236 62. Tongue, (Esophagus, Epiglottis, and Trachea, Posterior View 240 63. Thoracic Duct, Vertebral Column, Lung-Cells, etc. . 243 64. Showing Glands and Cells of the Stomach, etc. . . . 246 LIST OF ILLUSTRATIONS. FIG. PAGE 65. Vertical Section through the Stomach, showing the ARRANGEMENTS OF ITS MUCOUS MEMBRANE IN LONGITU- DINAL Folds, etc 283 66. An Ulcerated Stomach caused by the Excessive Use of Alcoholic Drinks 290 67. The Eye, Right Side 311 68. The Eye, showing the Optic Nerve, Choroid with the Ciliary Nerves, Ciliary Processes, etc 314 69. Vertical Section through the Eye and Optic Nerve. 317 70. External, Middle, and Internal Ear 331 71. Internal Ear 333 72. Kidney 340 73. Malpighian Bodies, etc 343 74. Section of Healthy Skin 344 Anatomy, Physiology, and Hygiene. CHAPTER I. THE BLOOD. SECTION I. 1. Definition.—Blood is a liquid tissue. It is the most important of all the fluids of the body. It contains food in solution for all parts, and receives from the tissues the effete, poisonous matter which is produced by their action. 2. There are a great many kinds of blood to be found in the different divisions of the animal. kingdom. But any fluid which has for its work or function the regen- eration of animal tissues may property be called blood. 3. In many of the lower forms of life the blood is a very simple and colorless fluid, containing only a few granules of organic matter, with inorganic salts in solu- tion. In the first forms of life this simple fluid furnishes all the food that is necessary for the growth and develop- ment of all the tissues and organs of which these lowly- organized creatures are composed. It also contains all the products of physiological activity—secretions and 10 THE BLOOD. excretions, as well as air in solution for respiration. As yet there is no elaboration of parts or differentiation of structure for the performance of multiplied function. 4. If we continue our study of this branch of organic life, we notice a change taking place in the tissues of the body, certain parts becoming peculiarly modified and specialized for the performance of certain functions, until we reach the wonderful structure of man, present- ing the complex apparatus for locomotion—bones and muscles; a muscular pump for throwing blood to all parts of the body—the heart; special organs for secretions and excretions—the liver, kidneys, lungs, salivary and mammary glands, as well as the various glands con- nected with the alimentary and genito-urinary tracts. 5.' Now, as the structure of the bodies of animals becomes more complex, so the blood changes in its struc- ture from, at first, a simple colorless granular fluid, until in the higher vertebrates and in man we find the great vital fluid red in color and composed of many anatom- ical elements. The quantity of blood in the human body is from one-tenth to one-eighth of the weight, or from sixteen- to twenty pounds. SECTION 11. ANATOMY OF THE BLOOD*. 1. The blood is composed of two distinct parts—a liquid part and a semi-solid part. The fluid portion of the blood is called the liquor sanguinis or plasma, and floating in this are the cellular or corjDUScular elements (Fig. 1). ANATOMY OF THE BLOOD. 2. Plasma.—The plasma is the clear fluid part of the blood. It contains, in solution, all the proximate princi- ples in a condition to be used by the tissues, and can be divided into a liquid portion called serum and a solid part called fibrin. The serum is the plasma deprived Fig. 1. WHITE BLOOD-CELLS. a, a, a, a, a, a, “ phagocytes,” white»cells containing micro-organisms; h, Bacillus tuberculosis, the organism causing consumption or phthisis; V, white cell show- ing pseudopodia; c, same, showing process of reproduction by division; d, d, d, the appearance of white blood-cells after the addition of water; e, same, after addition of dilute acetic acid; in c, d, e the nuclei are visible; g, normal appear- ance of a white blood-cell; h, after the action of dilute alcohol. of the fibrin factors; it is not a natural constituent of the blood, being formed only after the blood is drawn from the body. 3. Fibrin is the name given to the solid portion of a blood-clot, and is composed of two factors, which are 12 THE BLOOD. called fibrinogen and fibrino-plastin or paraglobulin. While the blood is moving or circulating in the vessels of the body these factors do not combine; but when the blood is allowed to flow from a cut vessel they come together and form a fibrillated or stringy substance, which soon contracts into, a jelly-like mass which is called fibrin, holding in its threads or meshes the corpuscles of the blood, and squeezing out or expressing a clear or straw- colored liquid, which is the -serum. 4. The fibrin and corpuscles constitute the clot, while the serum is all the liquid part of the plasma. This natural formation of a clot performs an important func- tion in the arrest of hemorrhage. Were it not for this provision of nature, we would bleed to death whenever a vessel of any size became ruptured. 5. The plasma, in man, forms a little more than one- half of the whole volume of blood—exactly sixty-four parts of plasma and thirty-six parts of corpuscles in one hundred volumes. The plasma is heavier than water, having a specific gravity of 1028, and its reaction is alkaline. SECTION 111. BLOOD-CELLS OR BLOOD-CORPUSCLES. 1. A variety of names is given to the semi-solid constituents of the blood. They are called blood-cells, blood-disks, blood-globules, and blood-corpuscles all meaning the little round or ovoid bodies which swim about in the plasma. 2. In all vertebrates (animals possessing backbones) RED BLOOD-GLOBULES. the plasma contains at least two kinds of blood-corpus- cles, which differ in size, and especially in color. They are called colored and colorless, or red and white blood- cells. 3. In the higher vertebrates—viz. mammals, to which class man belongs—there exists a _ third cor- puscle, which is now considered a constant element of mammalian blood. These corpuscles are some- times called haematoblasts, but the name now gen- erally accepted is blood-plates or blood-plaques. They are small and colorless, increase in number in certain diseases, and are thought to have something to do in causing the coagulation of the blood (Fig. 1). 4. There also exist in the blood—in considerable numbers after a meal or during digestion, few in num- ber during the intervals of digestion—small granules, called by some writers elementary granules, by some globulins: they are probably fatty in their nature, and are derived from the chyle. SECTION IV. RED BLOOD-GLOBULES. 1. The red disks are the most numerous of all the cellular elements of the blood ; they are also smaller than the ordinary white corpuscles. The whole num- ber of red globules in the blood is enormous: various estimates have been made by different anatomists. One cubic millimetre (1 m. m.= in.) contains from 3,000,000 to 6,000,000. Power states that if all the red 14 THE BLOOD. corpuscles of the blood of an adult were put side by side, they would cover a surface of 3000 square yards. They vary in size from to 3-gVo °f an inch in diameter, and from 30V0 to wo o' °f an inch in thickness. They are homogeneous in their structure, and are not provided with a nucleus; no membrane invests them. 2. In having no nucleus they differ from the white globules. They are biconcave in shape, and thinner in the centre than at the circumference. This fact causes them to present a peculiar appearance when examined with the microscope. Being thinner in the centre than at the periphery, both parts cannot be in focus at the same moment; hence when the centre is light the pe- riphery is dark, and vice versa. Though called “ red corpuscles,” they only appear red when they, exist in great numbers. When viewed singly in the plasma they have a yellowish-green color, the yellow color being more marked in arterial blood, the greenish hue pre- dominating in venous blood. They possess some elas- ticity, and if deformed by pressure, as sometimes happens in passing through small capillaries, they rapidly regain their spherical shape. They also have the peculiar property of arranging themselves in rows resembling rouleaux of coin. This is due to the exudation of a sticky substance on their surface which causes them to adhere to each other when they come in contact. This is a post-mortem change, and does not occur while the blood is circulating in the vessels of the body. 3. If water be added to a specimen of blood, thereby diminishing the density of the plasma, the red blood- cells change their shape, swell up, and finally disappear. If the density of the plasma be increased, as by the RED BLOOD-GLOBULES. addition of a solution of sulphate of sodium, the cor- puscles become contracted, shrink, and present a wavy or zigzag outline, returning to their normal shape if the proper density of the plasma be restored. 4. The color of the red cells is due to the presence of a- coloring matter called haemoglobin, sometimes called hsemoglohnlin and hsemotocrystalline. This coloring matter has a great affinity for oxygen, and is important to re- member in connection with the part the red corpuscles play in respiration. It can be separated from the blood as beautiful crystals which vary in shape in different animals. 5. The red blood-cells of all vertebrates below mam- mals—i. e. fishes, amphibians, reptiles, and birds—con- tain a nucleus and are oval or angular in shape, and instead of being biconcave are biconvex. 6. In healthy human blood there exists from six hundred to twelve hundred red corpuscles for every white one. The red cells are heavier than the plasma in which they float, their specific gravity being 1088 to 1105. 7. Their origin is not accurately known. They are supposed by some to be formed from certain marrow- cells of bone; by others from the blood-plaques or white cells; and some think they originate de novo in the plasma in which they swim.' A relation is thought to exist between the size of the corpuscles and the activity of the animal—the smaller the corpuscle the more in- active the animal. There are many exceptions to this, but the higher wre go in the animal scale the smaller the corpuscles, being smallest in mammals and largest in low orders of reptiles. 16 THE BLOOD. 8. The following are the diameters of the red blood- corpuscles of some of the vertebrates (taken from Gulli- ver and Welcher): Man, 3 yVo i dog, sml cat, sheep, -g-oVir ? elephant, horse, 4gy 0; musk-deer, Tror! pigeon, toad, newt, ; proteus, mto 2vo i pike, ¥to o 5 shark, TTI¥2 ; mouse, yVm I black rat, yTIyy; brown rat, o¥lrT I- ferret, yTbT; camel (oval), long diameter, gyyy, short diameter, -g-gVe ; dromedary (oval), long diameter, y, short diameter, i Vir- ginia deer, ygW SECTION V. WHITE BLOOD-GLOBULES. 1. The white corpuscles of the blood of man are larger than the red, measuring from i° tsVo °f an inch in diameter. They are composed of an albuminous substance called protoplasm, which is transparent and sometimes granular, containing a clearly-defined central part called the nucleus, and not limited by a surround- ing membrane (Fig. 1). 2. The corpuscles have the peculiar power of send- ing out from their surface small prolongations called pseudopodia or false feet, by which they are enabled to change not only their shape, but their position as well. This movement of the white corpuscles very much re- sembles the motion exhibited by certain low forms of animal life called amoeba, and is called the amoeboid move- ment of the colorless corpuscles, the word amoeba mean- ing “ to change.” 3. The white corpuscles exist in the blood in the WHITE BLOOD-GLOBULES. proportion of one white to. every six hundred to twelve hundred red ones. They greatly increase in numbers during digestion and rapidly diminish during the inter- vals of digestion. They are much lighter than the red blood-cells, and are generally found occupying the sur- face of the clot when blood is permitted to coagulate slowly, helping to form the so-called buffy coat. They have a specific gravity of 1070. 4. A white blood-globule often contains more than one nucleus, and sometimes its granular matter is (in the blood of some animals, especially the horse) of a reddish color; which fact has led some writers to think that these corpuscles represent a transitional stage be- tween the white and red blood-cells. 5. The function of the white blood-cells is not known. They have the power, by their amoeboid movement, to penetrate the blood-vessels and gain access to the sur- rounding tissues. This occurs to a very considerable extent whenever any part of the body is injured, and they are probably concerned in the process of repair. They behave in a very peculiar manner within the blood-vessels, and if the circulation in the web of a frog’s foot or in its tongue be examined with a micro- scope, they seem to be sticky, to adhere to each other and to the sides of the blood-vessel, moving much slower than the red corpuscles, which occupy the centre of the vessel and glide smoothly and rapidly along. The white blood-cells are now considered to be identical with those cells found in the lymph, chyle, pus, mucus, and colostrum. The addition of acetic acid will make the nucleus more pronounced. 18 THE BLOOD. SECTION VI. BLOOD-PLAQUES AND ELEMENTARY GRANULES. 1. Constantly occurring in the blood of mammals are the third blood-corpuscles or blood-plaques, now regarded as a normal constituent of mammalian blood. Fig. 2. a, a, a, a, a, blood-plaques of various shapes; c, e, thread holding numbers of blood-plaques, obtained by suspending thread in blood ; g, shows formation of clot; /, strings of fibrin entangling in its meshes red and white blood-cells and blood-plaques. BLOOD-PLAQUES AND RAPID FORMATION OF CLOT. They are from xo-foo' ftoo °f an in°h in diameter, structureless, and without color, containing a few gran- PHYSICAL CHARACTERS OF THE BLOOD. ules, but probably not a nucleus, properly so called. They increase in numbers during many diseases, and are thought by Bizzozero to furnish the ferment which brings together the fibrin-factors to form a coaqulum, or clot (Fig. 2). 2. Elementary granules, called also granules and globulins, are supposed to be fatty particles derived from the chyle. They are not normal constituents of the blood, and are of no known physiological importance. SECTION VII. PHYSICAL CHARACTERS OF THE BLOOD. 1. The density of the blood varies somewhat within the limits of health according to the amount and kind of food taken. It also varies with the digestive act, and is greater in the male than in the female. The specific gravity of the blood at 60° F. is from 10.52 to 1057. 2. The temperature of the blood also varies in dif- ferent parts of the venous and arterial systems, being higher in the deep-seated tissues than in those near the surface. The average is given at from 98° to 100° F.— exactly, 98.6°. It is highest in the blood coming from the liver, where it is from 101° to 108°. The tempera- ture of the blood is greater in birds than in any other animals, reaching as high as 112°. 3. The blood has a very faint and peculiar odor, which is said to distinctly resemble that of the animal from which it is taken upon the addition of a small quantity of sulphuric acid. The plasma or liquid por- tion of the blood normally contains a small quantity of 20 THE BLOOD. common salt {chloride of sodium), three to four parts in one thousand, which gives it a salty or saline taste. Its reaction is alkaline. 4. The corpuscular portion of the blood is trans- parent, as well as the plasma, but when they exist to- gether, as they do when circulating under normal con- ditions in the circulatory system, they give rise to a fluid which has a density greater than the plasma and less than the corpuscles. When a ray of light enters a specimen ol blood it is refracted or broken as it passes through the plasma; then, entering a corpuscle—which has a greater density than the plasma—it is broken again and at a different angle; and so on, until finally it is lost. This is what causes the opacity of the blood. 5. A thin layer of blood is transparent, having a slight yellowish-green tinge. 6. In the arteries the blood is bright red; in the veins it is dark-blue or black. It changes its color in the capillaries of the system, losing oxygen and gaining carbonic acid gas; again, in the capillaries of the lungs losing carbonic acid gas and gaining oxygen. 7. The red color in the arterial system is due to the presence of oxygen gas combined with the coloring matter of the red cells {haemoglobin). The dark-blue or black color of venous blood is due to the presence of carbonic acid gas. 8. Under normal conditions of circulation and res- piration the blood parts with its carbonic acid gas in the lungs and gains oxygen, changing from black, im- pure, or venous blood to red, pure, arterial blood. It then goes to the left side of the heart, and is pumped to all the tissues and organs of the body, changing from PHYSICAL CHARACTERS OF THE BLOOD. pure, red, arterial blood to black, impure, or venous blood. It is then taken up by the veins and carried to the right side of the heart, thence to the lungs to be purified again, and made ready for another circuit of the body. 9. It sometimes happens that more arterial blood is sent to an organ than is necessary for the performance of its function. When this occurs all of the oxygen is not used by the tissues, and the blood in the veins re- turning from such a part is red. This takes place dur- ing the maximum activity of those glands which are concerned in the production of secretions and excre- tions. 10. Coagulation.—Where blood escapes from the body and comes in contact with the air it coagulates or sets into a jelly-like mass, forming a clot. When con- traction of the fibrin has fully taken place, a liquid will be found squeezed out and occupying a position above the clot or solid part. The liquid is the serum, and is of a pale straw color; the solid part is the clot or cras- samentum, and is composed of the fibrin and corpuscles (Fig. 3). 11. When coagulation has taken place slowly, the red blood-cells will be found in greatest numbers near the bottom of the clot, being heavier than the white cells, which are found in greatest numbers near the sur- face. When coagulation has been rapid, and the red cells have not had time to fall to the bottom, both red and white cells are found in all parts of the clot. 12. When coagulation has been slow, the clot will be firm ; when it has been rapid, the clot will be soft. 13. That part of a venous clot which is exposed to 22 THE BLOOD. the action of the air is red, the central part being dark. Fig. 3. Designed to show the phenomena of coagulation: a, fibrin with heavy red cells in its meshes; b, huffy coat containing mostly white cells; c, expressed serum. QUESTIONS. If the clot be divided by splitting it with a knife, a red blush will rapidly spread over the dark surfaces. This is due to the action of the oxygen of the air, driving out the carbonic acid gas and uniting with the coloring matter of the red cells. 14. Coagulation may be retarded by allowing the blood to flow into a smooth vessel containing one-seventh of its volume of a solution of sulphate of soda. It may be hastened by allowing it to flow into a vessel with rough surfaces, or into one containing bundles of small twigs or masses of thread. Coagulation takes place sometimes during life within the blood-vessels, but it is not a normal condition. QUESTIONS. SECTION I. Wliat is blood ? What does it contain for the body ? What does it receive from the tissues? How is this effete matter produced?(l). Are there many kinds of blood in the animal kingdom ? What properties will give to a fluid the name of blood ?(2). What kind of a fluid is the blood of the lowest animals? What does this simple fluid contain?(3). Is there a gradual increase in the complexity of the structure of animals from the lowest to the highest? What kind of apparatus has man for locomotion? circulation? secretion mid excretion?(4). Does the blood change in structure and complexity with the body of the animal ? What kind of blood is found in the higher vertebrates and in man ? What is the quantity of blood in the human body?(s). Of how many parts is the blood composed? What are they? What is the fluid part called ? What is the semi-solid part called ?(1). What is the plasma ? What does it contain ? Into how many parts can it be divided? What are they? What is the serum? Is it a natural con- SECTION 11. 24 THE BLOOD. stituent of the blood ? When is it formed?(2). What is fibrin? Of how many factors is it composed ? What are those factors called ? Do they come together while the blood is circulating in the vessels of the body? When do they unite? By their union what do they form? Does this fibrillated substance contract ? What kind of a mass does it form? What does it entangle in its meshes? What kind of a liquid does it squeeze out? What is the name of this liquid ?(3). What con- stitutes a clot? What is the liquid part of the plasma called? Does the formation of a clot prevent continued hemorrhage ?(4). What pro- portion of the volume of blood does the plasma form in man? Is it heavier or lighter than water ? What is its specific gravity ? What is its reaction?(s), SECTION 111. What names are given to the semi-solid constituents of the blood ? What do these names all mean ?(.!). How many kinds of corpuscles are found in the blood of back-boned animals ? Do they differ in size and color? What are they called ?(2). To which class of vertebrates does man belong ? Does the blood of mammals contain more than two kinds of corpuscles? What are these third blood-corpuscles called? Under what conditions do they increase ? Do they play any part in causing the blood to coagulate ?(3). Are there any other formed bodies in the blood in addition to those mentioned ? When are they increased as regards the digestive act? when diminished? What is their nature? their probable source?(4). Which are the most numerous of the cellular elements of the blood ? Are they larger or smaller than the white blood-cells? What can you say of their number? How many are in one cubic millimetre ? What part of an inch is a millimetre? If all the red blood-cells of an adult were put side by side, how much surface would they cover? What is their diameter ? Their thickness ? What can you say of their struc- ture? Have they a nucleus? Are they invested by a membrane?(l). How do they differ from the white blood-cells? What is their shape? Where are they thinnest? Can periphery and centre be in focus at the same time? What' appearance does this produce? What is their color in a thin layer? When are they red? What color predominates in arterial blood ? in venous blood ? Do they possess elasticity ? If de- formed, do they regain their shape under normal conditions of circula- SECTION IV. QUESTIONS. tion ? To what is their rouleaux arrangement due ? Does this occur while the blood is circulating in the vessels ?(2). When water is added to the blood, what is the effect on the red blood-cells ? If the plasma be rendei’ed dense by the addition of some salt, what is the effect on the red blood-cells?- How can their normal shape be restored?(3). To what is the red color of the red cells due ? Has this coloring matter an affinity for oxygen ? Can it be separated from the blood ? Do the crystals vary in shape in different animals ?(4). What is the character of the red blood-cells in the vertebrates lower than mammals? Why are they bi- convex ?(5). What is the relative number of red and white blood-cells in healthy human blood ? What is the weight of the red cells as com- pared with the plasma? What is their specific gravity ?(6). What is the origin of the red cells? Give some supposed sources of the red blood-cells? Is there any relation between the size of the red corpuscle and the activity of the animal? How does this rule hold when applied to animals high and low in the scale of life?(7). Give some diameters of red blood-cells in different animals?(B). SECTION V. What is the size of the white blood-cells in man? What is their shape when at rest? Of what are they composed? Do they contain a nucleus? Are they surrounded by a membrane?(l). What peculiar power is possessed by the white corpuscles? What enables them to change shape and position ? What is meant by the amoeboid movement of the white blood-cells? What does the word “amoeba” mean?(2). In what relative number to the red cells do the white cells exist in the blood ? When do they increase in numbers? When do they diminish? Are they heavier or lighter than the red cells? In what part of the clot are they generally found? What is their specific gravity V(3). Do the white cells ever contain more than one nucleus? Is their granular matter ever colored ? What are those white cells whose granular matter is colored supposed, by some, to represent?(4). What is the function of the white blood-cells ? Have they the power to penetrate the vessels? IV hen does this occur? Are they concerned in the repair of injured tissues? How do they behave within the lumen of the blood-vessels? V\ hat part of the lumen of the vessel is occupied by the red cells? How do they move? How do the white cells differ from those found in the lymph, pus, chyle, mucus, and colostrum? What is the action of acetic acid on the white blood-corpuscles ?(6). 26 THE BLOOD. SECTION VI. Are the blood-plaques regarded as normal constituents of mammalian blood ? What is their diameter ? What is their structure ? Have they a nucleus? Under what conditions are they increased in numbers? What is Bizzozero’s theory of their function ?(1). What are the ele- mentary granules supposed to be? Are they normal constituents of the blood ? What is their function ?(2). What causes the variation of the density of blood? Is it greater in the male or in the female? What is its specific gravity ?(1). Does the blood vary in temperature in different divisions of the vascular system ? Is it higher in superficial or deep-seated tissues? What is the average temperature of the blood ? In what animals does the blood reach the highest temperature?(2). What is peculiar about the odor of blood? How may it be developed? What is the reaction of the blood?(3). Is the corpuscular portion of the blood opaque or transparent ? What makes the normal circulating fluid opaque ?(4). What is the character of a very thin layer of blood?(5). What is the color of blood in the arteries? in the veins ? Where does it change its red color ? What gas does it lose ? What gas does it gain ? Where does it lose its black or dark-blue color? What gas does it lose? What gas does it gain?(6). To what is the red color in the arterial system due ? To what is the dark color of venous blood due-?( 7). Trace the current of blood and describe its changes from the right side of the heart to the point of starting?(B). Is there ever more arterial blood sent to an organ than is necessary ? When this takes place, what is the color of the blood in the returning veins of that organ ? When does this take place ? In what glands does it generally occur ?(9). What change takes place in blood when it escapes from the vessels and comes in contact with the air ? After contraction of the fibrin what kind of a liquid is found above the clot? What is the color of the serum? Of what is the clot composed?(10). In what part of a slowly-forming clot will the red cells be found ? When the formation has been rapid, where will they he found? Why? Where are the white cells found in a slowly-formed clot? Where in a clot of rapid formation?(ll). Under what conditions will a clot be firm ?(12). What is the color of that portion of a venous clot which is exposed to the air? What is the color of the central part? If the clot be divided, what causes the change of color of the central part ?(13). How may coagulation be retarded ? How hastened ? Does coagulation take place within the vessels during life ? Is it a normal condition ?(14). SECTION VII. CHAPTER 11. PHYSIOLOGY OP THE BLOOD. SECTION I. 1. The office of the blood is to supply all tissues and organs of the body with food for their growth and for the performance of their functions. The tissues and organs—with a few exceptions, as the enamel of the teeth, the nails, hair, and epithelium—are supplied with vessels through which the blood is pumped by the heart to all parts (arteries); another set of very fine vessels (capillaries), whose function is to distribute to the tis- sues the blood pumped by the heart through the arteries; and still another set (veins) whose work is to carry the blood back again to the right side of the heart, preparatory to its being sent to the lungs for purification. 2. The passage of the blood from the left side of the heart through the system—arteries, capillaries, and veins —to the right side is called the greater or systemic cir- culation ; the passage of the blood from the right side of the heart through the lungs to the left side is called the lesser or pulmonary circulation. 3. The plasma or liquid portion of the blood, some- times called the liquor sanguinis, is the menstruum or matrix in which the corpuscles float. It contains, prin- 27 28 PHYSIOLOGY OF THE BLOOD-. cipally, the food for the tissues, as well as certain worn- out, effete materials—ash—which are formed by tissue- activity or tissue-work. The food-materials exist in greater quantity in the arterial division of the vascular system; the effete, ashy matter predominating in the veins. 4. Colored Corpuscles.—The red cells of the blood carry oxygen to the tissues from the lungs, the tissues being unable to perform their work in the absence of this gas. They take the oxygen from the red blood- cells, and give up another gas—carbonic acid gas—which acts as a poison in the absence of oxygen, and causes the blood to change in color from red to dark-blue or black. 5. These important changes—loss of oxygen and gain of carbonic acid gas, and change from pure to impure blood—take place in the region of the small vessels which connect the arteries with the veins, called the capillaries. These vessels have but one very thin coat. SECTION If. WHITE BLOOD-CELLS. 1. The function of the leucocytes, or white blood-cells, is not exactly known. They are supposed by some writers to break up and form nuclei or kernels about which red cells form. They are probably concerned sometimes in the formation of new tissues, as when divided parts heal and become united. They are of importance in furnishing a principle—ferment—which assists in the coagulation of blood. They are also con- WHITE BLOOD-CELLS. 29 cerned in the destruction of tissues under certain con- ditions, as when animals lose some of their parts by gradual decay—atrophy—pieces of tissue having been recognized in their interior. 2. They probably perform an important service for the body in the destruction of certain micro-organisms (microscopical plants) which exist in the blood in great numbers in certain diseases, as pneumonia, cholera, typhoid fever, consumption (tuberculosis), erysipelas. Those white cells which feed upon these organisms have been called phagocytes or eating cells (Fig. 1). 3. Blood-Plaques.—Physiologists have no exact knowledge of the function of the blood-plaques. They are supposed by some to be nuclei for red blood-cells; by others to be formed from the disintegration of white blood-cells, therefore fragments of leucocytes; and by still others to be formed de novo from the plasma. They increase in numbers during pregnancy and whenever blood is rapidly formed in quantity (Fig. 2). 4. If we would have healthy tissues and organs, sound bodies, and perfect health, it is absolutely neces- sary that we have good nutritious blood, and that all the material, as well as organs concerned in its forma- tion and distribution, should be healthy in structure and perform their functions properly. A stomach which has its mucous membrane eaten into ulcers by the use of alcohol cannot secrete a healthy gastric juice for digestion; a liver contracted and hardened by the use of intoxicating liquids cannot furnish healthy bile; and a heart under the influence of alcohol does not properly distribute the blood. 5. Another important function of the blood is to 30 PHYSIOLOGY OF THE BLOOD. take up effete matter wherever it finds it in the tissues, and carry it to the various excretory organs—the kid- neys, liver, lungs, skin, and alimentary canal (though the liver, lungs, skin, and alimentary canal also have other functions)—whose work is to separate the poison- ous matter from the blood and put it in a condition to be discharged into the external world. SECTION 111. ACTION OF ALCOHOL AND NARCOTICS ON FRESHLY-DRAWN BLOOD. 1. The red blood-cells are said by many authors to be increased in size in the body by the free use of alco- hol. A number of other substances produce the same effect, as cold, oxygen, quinine, and the poor condition of the blood during many diseases. 2. The habitual use of morphia (the active principle of opium), fevers produced by the absorption of septic matters, violent exercise, and starvation cause the red blood-cells to become diminished in size. 3. When alcohol is added to a fresh specimen of blood on a glass slide, and examined with a micro- scope, a very small quantity of dilute alcohol causes the red blood-cells to appear larger, smooth, and to arrange themselves edge to edge; that is, they touch at some part of their circumference, and do not present the characteristic arrangement like piles of coin with their flat surfaces touching. Acted upon by a stronger solution of alcohol, they become distinctly smaller, have an irregular wavy or zigzag appearance, and tend to ACTION OF ALCOHOL AND NARCOTICS. 31 aggregate in masses, still showing the tendency, how- ever, to come together at their edges instead of at their flat surfaces. This irregular appearance of their cir- cumference may be due to the abstraction of some of the water of the cell by the alcohol (Fig. 4). Fig. 4. a, effect prod need by addition of other to specimen of fresh blood ; h, appear- ance caused by chloral hydrate; c, appearance produced by action of cocaine; d, d, effect produced by action of opium; e, effect produced by rapid drying; e ’ crenation by loss of water; /, /, effect of strong alcohol; g, normal appear- ance, surface view; h, side view; j, coin-like arrangement; k, exudation hold- mg them together; I, corpuscle of a frog; I', edge view; n, stroma of same. Red Bdood-Cedds. 4. Opium.—A strong alcoholic extract of opium 32 PHYSIOLOGY OF THE BLOOD. causes the red blood-cells to become rather dark and of a round, homogeneous, smooth appearance. They do not arrange themselves in piles like rouleaux of coin, and all over the field may be seen great num- bers of very small circular bodies resembling blood- plaques, with multitudes of small granules arranged in masses. Occasionally, under treatment with opium, a few of the red cells are irregular in outline, but this is probably caused by the alcohol used or by evapora- tion (Fig. 4), 5. Chloral.—A concentrated watery solution of hy- drate of chloral causes the red cells to break up, and they never arrange in piles with their flat surfaces touching. Numerous small globular buds are seen to develop on their surface, and often these buds are attached to each other like beads on a string. They may form chain-like strings, or break apart and exist as very small round bodies in masses (Fig. 4). 6. Cocaine.—Acted upon by a strong aqueous solution of cocaine (active alkaloid of Erythrox'ylon co'ca), the red blood-cells become dissolved, only a very few being seen in the field, and these are clear, with a faint and indis- tinct outline (Fig. 4). The plant which furnishes cocaine grows on the east- ern slopes of the Andes Mountains, and is used by the inhabitants of Bolivia, Chili, and Peru as an article of diet and as a medicine. It takes the place of the coffee, tea, opium, and hashish of other peoples. Recently it has been much used as a local application to prevent pain during minor operations in surgery. When habit- ually used for the pleasure of the effect it produces, it leads to the formation of a habit more terrible than ACTION OF ALCOHOL AND NARCOTICS. that of opium or alcohol, completely depriving its vic- tim of his higher intellectual faculties and judgment, and ending oftentimes in murder and suicide. 7. Tobacco and its Active Principle, Nicotia.— Strong solutions of tobacco have no perceptible influ- ence on the shape or size of the blood-cells, red or white. Its active principle, nicotia, causes the blood to become dark in color and the red cells to disintegrate. 8. White Blood-Cells.—Dilute alcohol causes the white blood-cells to become clear (making the nucleus more prominent), to develop little bladders or vesicles on their surface, and, in greater strength, to become dissolved (Fig. 1). 9. Quinine (Quininse Sulphas) arrests their move- ments and prevents them from passing through the walls of the small blood-vessels. Induced currents of electricity also arrest their movements, and, if too strong or oft repeated, finally kills them. 10. Alcohol in some form has been employed as a dressing for wounds and ulcers since the earliest times in the history of surgery. As used by the ancients, it was in the' form of wine with some astringent. In its most popular form now it is used as the camphorated spirit of wine, and is thought by many eminent surgeons to be the best of all dressing for wounds and ulcers. Its efficacy is in proportion to the alcohol it contains. 11. History.—Leeuwenhoek first saw the red cells of human blood in 1673. He described them in a paper published in 1674. Red blood-cells had been seen, how- ever, before this by Malpighi in 1661, while examining the blood of a hedgehog. William Hewson described the white blood-cells or leucocytes in 1774. 34 PHYSIOLOGY OF THE BLOOD. Table showing the Constituents of Blood, Red, White, Blood-Plaques, Granules. Corpuscles Fibringen, Fibrinoplastin, or Paraglobulin, Ferment, Blood. Fibrin. Liquor sanguinis or Plasma. Serum. Serine, Metalbumen, Water. Fibrin, Corpuscles, and generally | of the Serum. Clot QUESTIONS. SECTION I. What is the function of the blood ? How is the blood brought to the tissues ? Name some structures that are not supplied with vessels. What sends the blood to the tissues ? What is the function of the capillaries? the veins? Where do the veins carry the blood? Why is it sent from the right side of the heart to the lungs ?(1). What is the greater circu- lation ? Give both circulations, beginning with the right side of the heart.(2). What is the plasma? What does it contain? What part of the vascular system contains the most nutritive blood? In which division is the effete matter principally found ?(3). What do the red blood-cells carry from the lungs to the tissues ? Is oxygen necessary for tissue-work ? What gas is produced by tissue-waste ? Is carbonic acid gas (CO2) poisonous in the absence of oxygen ? What change in color does it produce in the blood ?(4). In what division of the vascular sys- tem does this important interchange of gases take place? How many coats have capillaries ?(6). SECTION 11. What is the function of the leucocytes ? Name some theories ad- vanced as to their use. Do they assist in the coagulation of the blood ? QUESTIONS. Are they concerned in tissue-formation and tissue-waste ?(1). Do they probably feed upon organisms which produce disease ? Name some dis- ease caused by micro-organisms. What special name have these bacteria- eating white blood-cells been given ? What does the word “ phagocytes ” mean ?(2). What is the function of blood-plaqties ? What are some theories as to their origin ? When are they increased in number ?(3). What is a necessary condition for healthy tissues and organs ? Can the stomach secrete good gastric juice when ulcerated by the use of alcohol ? Can the liver and heart act properly when diseased by the use of alco- hol? (4). What is the function of the blood as regards the effete matter of the system ? Where does the blood take it for elimination ?(5). SECTION 111. How are the red blood-cells affected in the body by the free use of alcohol? Name some other things which produce the same effect.(l). What produces a diminution in the size of the red blood-cells ?(2). What is the behavior of the red cells out of the body when treated with alco- hol ? Do they touch by their flat surfaces or at their edges ? Do they become smaller or larger ? When the alcohol used is very strong, what effect is produced as regards size, shape, and arrangement? To what is the irregular condition of their circumference probably due?(3). What effect is produced by the action of a strong alcoholic extract of opium on red blood-cells? What additional structures may be seen in the field? Are red cells ever irregular when treated with opium ? To what is this irregularity due?(4). What effect is produced by the action of chloral on the red blood-cells ?(5). What is the action of cocaine on the red blood-cells? Where does the plant from which cocaine is produced grow ? For what is it used by the inhabitants of those countries ? Is the drug ever used in surgery? For what purpose ? What conditions are produced by the constant use of it ?(6). How do strong solutions of tobacco affect the shape of the red cells ? What effect is produced by its active principle, nicotia?(7). What is the action of alcohol on the white blood-cells ?(8). What is the action of sulphate of quinia on the white cells? What effect have currents of electricity on them ?(9). Is alcohol employed as a local dressing for ulcers and wounds ? In what form was it used by the ancients ? In what form is it mostly used now?(10). Who first saw red blood-cells, and when? Who first de- scribed human red blood-cells, and when? When and by whom were the white cells described ?(11). Put upon the blackboard the table show- ing the constituents of the blood. CHAPTER 111. CELLS, TISSUES, AND ORGANS. SECTION I. 1. Cells.—Every tissue and organ of the body is com- posed of cells. A cell may be defined as a minute mass of protoplasm, having, generally, a spherical shape, and in its simplest form being homogeneous and destitute of granules, nucleus, and cell-wall. 2. Protoplasm is the name of the substance that first manifests the phenomena of life—motion, sensibility, the power to grow in size and to reproduce its kind. All plants and all animals, from the lowest to the high- est, begin their existence as a simple protoplasmic cell, and in the beginning it is impossible to tell whether the cell will be an animal or a plant. 3. The word protoplasm, which means “ first form,” was first used by Dr. Hugo von Mohl, in 1846, in describing the contents of certain vegetable cells. The word sarcode, meaning “ fleshy,” was used by Dujardin, in 1835, in describing the structure of some of the sim- plest forms of animal life. The protoplasm of Von Mohl and the sarcode of Dujardin are now regarded as being identical, as was shown by Cohn in 1850 and by Max Schultze in 1860. Bioplasm, sarcode, protoplasm, are terms 36 CELLS; TISSUES, AND ORGANS. used to denote the living matter of all plants and of all animals. 4. As stated above, the simplest cell, is homogeneous in structure and without a cell-wall. A typical cell, however, has a nucleus or kernel, a nucleolus, and a number of granules in its substance, the whole being surrounded by a membrane which is the product of the cell, and which is called the cell-wall. The cell-wall of plant-cells is a substance akin to starch, called cellulose; the cell-wall of animal cells contains nitrogen, and is albuminous in its nature. 5. The nucleus is first formed by an aggregation of the granules of the body of the cell. Cells always repro- duce their kind by the nucleus dividing first, then the protoplasm of the body proper of the cell. 6. A single cell forms the whole body and performs all the functions of the simplest plants and animals. These never attain a higher structure. All animals and all plants begin their existence as a cell, which by division and growth and union of newly-formed cells forms tissues, and these, uniting, form organs, which, when properly held together, constitute organic beings—animals and plants. 7. Tissues are formed by the union of cells. The cell first divides into two parts, the nucleus dividing first, each of these into two more, and so on until a mass of cells is formed. These now begin to unite or to fuse with each other, forming a tissue, as muscular tissue, nervous tissue, osseous and glandular tissue. The tissues are then properly arranged and combined to form organs, as muscles, bones, nerves, and glands. The cell- ular structure of plants generally persists with slight 38 CELLS, TISSUES, AND ORGANS. modifications, while in animals the special cell-struc- ture is generally masked by more perfect tissue- formation. 8. Tissues are formed by the aggregation of cells. If any organ be examined, it will be found to be com- posed of tissues which in turn are composed of cells. Take as an example the liver of one of the higher ani- mals as man. It is composed of definite portions called lobes, of which there are five. These, in their turn, are composed of lobules, and these of true liver-tissue, which is made up of a network of blood-vessels, fine biliary ducts, and liver-cells, the cells being the active parts. This starts with the liver, which is an organ made up of lobes, the lobes of lobules, the lobules of liver-tissue—the important part of which is the liver- cells. So we may go from the simple to the complex, starting with liver-cells, which are held together to form liver-tissue, this united to form lobules, the lob- ules forming lobes, and the lobes, five in number, constituting the normal organ, the liver. So the brain may be described as an organ composed of nervous tissue, fibres, and cells, supported by delicate tissue, neuroglia. The brain-cells are the active parts in the generation of nervous force, and the fibres conduct that force to some organ for its manifestation. 9. Under certain conditions ordinary protoplasmic cells may be changed into other structures, thus chang- ing one tissue into another. 10. Tissues are bound together to form organs, and organs are united to each other to form bodies by con- nective tissue. This name indicates that it is simply a CELLS, TISSUES, AND ORGANS. 39 medium of connection by which the various structures of the body are held together. 11. Ordinary connective tissue is composed of very delicate threads of animal matter, which are white and inelastic or yellow and elastic, arranged in a dense net- work, as in the skin; in a loose network, as in the sub- cutaneous tissue; or parallel, as in tendons, and having lodged between or upon them protoplasmic cells, or, as they are called here, fibrous connective-tissue cells or corpuscles. The tissue found in the tendons, skin, and subcutaneous tissue is of the white or inelastic variety. In yellow elastic tissue the corpuscles or cells are the same as in the white, but the fibres are yellow in color and will stretch. It is found lining the heart and blood- vessels, around the air-cells of the lungs, and in certain ligaments. The fibres of a connective tissue are held to each other to form bundles by a semi-fluid cement sub- stance of about the consistence of the white of egg. These bundles are held to each other by the same kind of inter- fibrous semi-fluid cement material. 12. Ordinary fibrous connective tissue may be changed into fatty tissue by the protoplasm of the fibrous connective-tissue cell or corpuscle becoming con- verted into fat. This sometimes happens in disease or under conditions of excessive nutrition, when more food is taken into the body than is needed to repair its waste or to perform its functions. The change begins by the appearance, here and there, of little droplets of fat in the protoplasm of the cell. These gradually increase, and small drops run together to form large ones, until all the protoplasm but a small quantity is removed and its place occupied by fat, which now fills all the interior 40 CELLS, TISSUES, AND ORGANS. Fig. 5. a, a, a, a, shows connective-tissue cells with pigment in their protoplasm ; b. same enlarged; i, its nucleus; c, a group of fat-cells held together by connective- tissue fibres, showing their nuclei near the surface. of the cell-wall, the nucleus being pushed to the inner surface of the wall and flattened. A fat-cell, then, is composed of an envelope of animal matter, with a CELLS, TISSUES, AND ORGANS. 41 flattened nucleus on its inner surface, surrounding a drop or mass of oil. During starvation or hibernation a fat-cell may be changed, by loss of its oil, into a proto- plasmic cell. A number of fat-cells are held together by very delicate fibres of connective tissue to form lobules, and these are held together to form lobes, and lobes ot fat are united to form continuous masses. (See Fig. 5.) 13. It sometimes happens that the protoplasm ol the cells contains granules of coloring matter, or pigment, of varying color—green, brown, black, blue, or yellow— thus changing an ordinary connective-tissue cell or cor- puscle into a pigmented connective-tissue cell or a pig- ment-cell. The protoplasm of the body and processes of the cell may be studded with granules of coloring matter, but the nucleus contains none. (See Fig. 5.) 14. Pigment-cells are found in the skin of fishes, amphibians, and reptiles, and give to them their varying color. They also occur in certain tissues of the eye in man and mammals. Darkness causes them to contract, and therefore the tissues in which they are found become lighter in color during such contraction. Sunlight causes them to relax and remain in a passive state, thus causing a tissue containing them to become darker. Certain animals have the power to change color at will, and in these cases the nervous system must regulate the contraction and relaxation of the pigment-corpuscles. The ground-lion (chameleon) is such an animal. 15. Cartilage is a connective tissue, the intercellular substance of which is transparent and firm (in hyaline cartilage), and the cells are provided with a capsule. Cartilage has no true blood-vessels, but gets its nourish- ment by a system of channels running through it from 42 CELLS, TISSUES, AND ORGANS. the perichondrium—a membrane which covers it and which contains blood-vessels and nerves (Fig. G). 16. There are three kinds of cartilage: hyaline, de- scribed above, in which the intercellular substance looks Fig. 6. HYALINE CARTILAGE. a, a, a, a, a, the matrix or intercellular substance; c, the yellow lines represent the capsule containing the cartilage-cells ; b, b, b, b, channels of communication between the cartilage-lacunse. like ground glass (hence its name), found on the articular surfaces of all bones, on the edges of the sternum, scapulae, and ilia, in the rings of the trachea and cartilages of the larynx. All the bones of the body except the tegu- mentary bones of the skull are preformed as hyaline cartilage. The angle of the inferior maxillary bone is CELLS, TISSUES, AND ORGANS. also preformed as hyaline cartilage, the remainder of the bone being preformed in membrane (Fig. 6). 17. In fibrous connective-tissue cartilage the inter- cellular substance is fibrous tissue, while the cells have a capsule and are called cartilage-cells (c, Fig. 6). Here is a tissue which is mixed. It is neither a true cartilage nor a fibrous tissue, hence its dual name. Yellow elastic cartilage is the same as fibrous connective-tissue carti- lage, the only differ- ence being that the fibres are yellow instead of white. Pibro-carti- lage is found between the bodies of the verte- brae and in the neigh- borhood of joints where true cartilage gradually merges into ligament- ous tissue. Yellow elas- tic cartilage is found in the Eustachian tube, in the ear, and in the two small cartilages of the larynx (Fig. 7). Fig. 7. a, a, a, cartilage; b, b, matrix of fibrous tissue. FI BRO-CARTILAGE, 18. Bone is a connective tissue, the cement substance which holds the fibres together being replaced by the inorganic salts of lime. 44 QUESTIONS. QUESTIONS. SECTION I. Of what is every tissue and organ of the body composed ? Define a cell(l). What is protoplasm? Name some of its properties. How do all plants and animals begin their existence ? Is it possible to tell at first whether a cell will be an animal or a plant ?(2). What does the word “ protoplasm ” mean ? When, by whom, and for what purpose was the word first used ? When, by whom, and for what purpose was the word “sarcode” used? What does sarcode mean? When and by whom was the identity of protoplasm and sarcode shown ? What other term is used to express the same thing as sarcode and protoplasm ?(3). Has the simplest cell a cell-wall? Name the parts of a typical cell. What forms the cell-wall? What is the difference between the cell-wall of an animal and that of a plant?(4). How is the nucleus first formed? How do cells reproduce ? What part of a cell divides first ?(5). How are tis- sues formed? How are organs formed ? How are bodies formed ?(6). Give some examples of tissues. What is peculiar about the structure of plants ? How do they differ in this respect from animals ?(7). Of Avhat are organs composed ? Of what are tissues composed ? Describe the formation of an organ from cells ? Begin with the formed organ, and resolve it into its constituent parts.(B). Do protoplasmic cells ever change into other structures?(9). What is connective tissue? What function does it per- form in the body ?(10). Of what is connective tissue formed ? How are the fibres arranged in skin ? in mucous membranes? in tendon? How many varieties of connective tissue ? Where is the white found ? Where is the yellow found ?(11). How are fat-cells formed ? Name the parts of a fat- cell. How are fat-cells held together ? What becomes of the fat-cells dur- ing hibernation and starvation ?(12). What are pigment-cells ? Of what color are they? Does the nucleus ever contain pigment?(l3). Where are pigment-cells found? Have they the power to contract? What effect has sunlight on them? What is the effect of darkness? Have any animals the power to change their color by an act ol the will?(14). What is cartilage? Has it any blood-vessels t How does it get its nour- ishment ?(15). How many kinds of cartilage are there? What is the character of the intercellular substance of hyaline cartilage ? Where is hyaline cartilage found ?(16). Describe fibrous connective cartilage. What is peculiar about a cartilage-cell ? Where is fibro-cartilage found ? Where is yellow elastic cartilage found?(l7). What is bone? What kind of material is between its fibres ?(18). CHAPTER IV. BONES. SECTION I. 1. Definition.—Bone is composed of a dense, unyield- ing groundwork or matrix supporting and containing a number of soft structures. 2. The groundwork or matrix of bone is the true osseous substance. It is formed of a network of fibrous connective tissue, the interfibrous cement substance of which is replaced by the inorganic salts of lime. 3. The soft structures of bone are the periosteum, marrow, blood-vessels, nerves, and lymphatics. 4. The periosteum (around the bone) is the name of a fibrous connective-tissue membrane which sur- rounds bone; to it muscles, tendons, and ligaments are attached. It contains in its meshes blood-vessels, nerves, and lymphatics, and can be separated into two distinct layers. The external layer is made up of fibrous connective tissue arranged in a dense, compact manner. It is strong and unyielding ; hence the ago- nizing pain caused by a bone felon. The internal layer is also formed of fibrous connective tissue, but the fibres are arranged in a loose manner, forming a soft bed or nidus in which are lodged the blood-vessels, nerves, and lymphatics. This layer contains cells (osteoblasts), pecu- 46 BONES. liar little bodies that have the power to make new bone, and is sometimes known as the osteo-genetic layer. It communicates with the marrow by means of the Haver- sian spaces and canals. Bone deprived of its periosteum would soon die. 5. Marrow, like the layers of the periosteum, is composed of fibrous connective tissue which is very fine and delicate, and which is arranged in a very loose, spongy network supporting arteries, capillaries, veins, and marrow-cells. 6. Marrow is found in the tubular portion of long bones and in the spaces of the cancellous or spongy part of flat and short bones. It communicates with the inner layer (osteo-genetic) of the periosteum, and, in fact, is originally formed from this layer. 7. There are two kinds of marrow—red and yellow. Red marrow is found in all young bones, in the ends of long bones, and in the Haversian spaces of short and flat bones. 8. Yellow marrow is found in old bones and in the tubular part of long bones. It is the same in structure as red marrow, the marrow-cells of which have been changed into fat. Red marrow is active in bone-forma- tion. It is also said to have the power to form red blood- cells. Yellow marrow is inactive so far as bone-making is concerned. SECTION 11. VARIETIES OF BONE. 1. According to the arrangement of the osseous tis- sue, there are two kinds of bone—compact and cancellous CLASSIFICATION OF BONES. or spongy. Compact bone is found where strength and protection are needed, as in the shafts of long bones and on the surfaces of short and flat bones. 2. Cancellous or spongy bone is found in the ex- tremities of long bones and in the bodies of short aqd flat bones. It affords increased surface for the forma- tion of joints, for muscular and ligamentous attachment, gives lightness, and diminishes shock. 3. Color.—Healthy bone is of a pinkish-white color. SECTION 111. CLASSIFICATION OF BONES. 1. For convenience of description, bones are classi- fied into long, short, flat, and irregular bones. 2. Long bones are found where great range of mo- tion is required, as in the extremities. They have two extremities (epiphyses) and an intermediate part—the shaft (diaphysis). The shaft is composed of compact bony tissue, is hollow in the centre, and contains mar- row. The extremities are composed mainly of cancel- lous bony tissue, generally covered with cartilage, and containing a number of irregular spaces (Haversian spaces) filled with marrow. 3. Examples of long bones are—the humerus, or arm- bone ; radius and ulna, or bones of the fore arm; femur, or thigh-bone; tibia and fibida, or bones of the leg; the metacarpal bones, or bones of the palm; and the pha- langes, or bones of the fingers and toes. 4. Short bones are found in those parts of the skele- ton having limited motion and great strength. They 48 BONES. Fig. 8. Bones of the wrist and hand, posterior view, right side, c, carpus. are generally bounded by surfaces and angles, and are CLASSIFICATION OF BONES. composed of spongy bone-tissne covered over with thin layers of compact bone. They are covered with perios- teum, and where they enter into the formation of artic- ulations are coated with cartilage. 5. Examples of short bones are—the bones of the carpus, or wrist-bone (Fig. 8); the bones of the tarsus, or ankle-bones (in part); and the patella, or knee-cap or knee-pan. 6. Flat bones are found where increased surface is needed for muscular attachment and where delicate parts are to be protected. They are covered with periosteum, and are composed of two layers of com- pact bone, between which is found cancellous bone. In the flat bones of the cranium the layers of com- pact bony tissue are called respectively the inner and outer tables of the skull. The spongy tissue between is called the diploe (Fig. 9). 7. Examples of flat bones are—the bones of the cranium—occipital, parietal, and frontal—which aid in closing the cranial cavity and assist in protecting the brain; sternum, or breast-bone, and ribs, which assist in forming the thorax and protect the heart and lungs; ossa innominata (nameless bones), or hip-bones, which, together with the sacrum behind, form the pelvic cavity and protect the delicate parts within. 8. Irregular bones are found in nearly all parts of the central or axial skeleton. They are composed of spongy bone covered with a layer of compact tissue. They are found where there* is limited motion and great strength, and where there is great surface for protection and muscular attachment. 9. Examples of irregular bones are—the vertebrse, or BONES. Fig. 9. Parietal bones, separated in the median line; shows method of formation of the sagittal suture. THE SKELETON. bones of the spinal column; the innominate, or hip- bones, which are also flat in part, but which are so irregular in shape that they have been named the ossa innominata, or bones without a name. Other irregular bones are—the hyoid, or tongue-bone; malar, or cheek- bone ; superior and inferior maxillary bones, or upper and lower jaw-bones. SECTION IV. THE SKELETON. 1. Skeleton is the collective name used for all the bones of the body. When it is situated within the body, as it is in man and all the higher vertebrate ani- mals (back-boned animals), it is called an endoskeleton ; when the hard parts for muscular attachment are devel- oped on the exterior of the body, as in crabs, lobsters, and insects, it is called an exoskeleton. 2. The skeleton of man is divided into the central or axial skeleton and the peripheral or appendicular skeleton (Fig. 10). 3. The axial or central skeleton is composed of the bones of the cranium and face, vertebrae, ribs, and sternum. 4. The appendicular or peripheral skeleton is com- posed of the scapula and clavicle, ossa innominata, and the bones of the upper and lower extremities. 5. The number of bones in the central or axial skel- eton is 74; the number in the peripheral or appendicu- lar skeleton is 126; the number in the complete skeleton being 200. This number does not include the teeth, BONES. FIG. 10.—THE SKELETON. a, shows the bones of the fore arm parallel; b, shows them crossed ; c, showing knee-pan or patella in position; d, show’s it turned down. ANATOMY OF BONES. which are regarded as not belonging to the true skele- ton, or a number of smaller bones—bones of the mid- dle ear and sesamoid bones. SECTION Y. ANATOMY OF BONES. 1. Bones are composed of laminae, or plates, of osseous tissue variously arranged in different parts of the skeleton. 2. Osseous tissue is ordinary fibrous connective tis- sue holding between its fibres inorganic salts of lime. These plates are perforated with numerous fine canals and contain larger oval or round spaces. The little canals are called canaliculi, and the spaces are called lacunae, or little lakes (Fig. 11). 3. The little lakes or lacunae contain a cell, and the little canals or canaliculi contain the finger-like pro- longations or processes of the cell. The lakes com- municate with each-other by means of the canaliculi, and the processes of one cell often touch those of neigh- boring cells. The cells with the processes are the bone- cells (b, Fig. 11). 4. In compact bone the laminae or plates of osseous tissue, with their lacunae, canaliculi, and bone-cells, are arranged in a concentric manner around open canals. This process may be simulated by winding a sheet of paper around a cylindrical stick, and then withdrawing the stick: the sheet of paper will represent the lamella or plate of bony tissue arranged in a concentric manner, 54 BONES. and the space previously occupied by the stick will rep- resent the canal. When a number of bony plates are Fig. 11. Magnified transverse section of compact bone, showing concentric arrange- ment of bone lamellae, b, b, b, b, concentric lamellae, showing lacunae and canaliculi: the black centre indicates the position of the Haversian canals. thus wound about a canal, it gives rise to a system of concentric lamellae; the canal with the surrounding plates forms an Haversian system. The number of laminae in the Haversian system varies, some canals being surrounded by more bony plates than others. ANATOMY OF BONES. The canals are called Haversian canals (a, Fig. 12) and they communicate with each other by means of branches, so that it is possible to go from one canal to the other (b, Fig. 12). Fig. 12. 5. These Haversian systems—concentric la- mellse and canals—when stood on end would fall down were they not held together by something. The same kind of bony tis- sue that forms the concen- tric lamellae holds them together. These uniting plates of bone are called interstitial or ground la- mellae. An idea of their arrangement can be ob- tained by imagining a number of sticks of chalk, with holes bored through them in their long axes, standing on end; the central opening would represent the Haver- sian canal, and the chalk would represent the concentric lamellae. Next imagine a sheet of paper with as many openings in it as there are sticks of chalk, put down in such a way that the sticks of chalk come through the openings. In this way the paper will be found between the sticks of chalk, and represents the arrangement of the interstitial or ground lamellm That part of the inter- stitial lamella which projects beyond the Haversian sys- Magnified vertical section of compact bone, a, a, a, a, a, Haversian canals; b, b, points of communication; c, c, c, c, c, c, c, lacunae and canaliculi. 56 BONES. terns takes a direction parallel with the long axis of the canals, and forms the circumferential lamella. 6. In cancellous or spongy bone the osseous lamellae are not arranged in a concentric manner, and do not form Haversian canals. They cross each other at dif- ferent angles, and form spaces which are sometimes regular and often irregular. These spaces contain mar- row and are called Haversian spaces, or cancelli. SECTION VI. 1. Bones subserve a very important function in th economy. They form the framework or groundwork of the body, and afford surface for the attachment of muscles and ligaments. Being acted upon by muscles, they assist in locomotion; hence are called the passive organs of locomotion. They enter into the formation of joints, diminish shock, and afford protection to many delicate parts. (Fig. 13, at e, d, shows formation of joint.) PHYSIOLOGY OF THE BONES. 2. By being impregnated with the salts of lime the bones become firm and unyielding and afford a support for the body. By containing a certain quantity of an- imal matter they also possess some elasticity and spring, and thus diminish shock and facilitate locomotion. In the disease mollitus ossium (soft bone) the bones lose their inorganic matter (chiefly the phosphate of lime) and become very soft and flexible. They will bend in any direction, and hence cannot support the weight of the body or afford proper points for the attachment of PHYSIOLOGY OF THE BONES. Fig. 13. Bones showing the formation of the right elbow-joint, a, humerus; 6, radius; e, ulna; d, surface for reception of ulna; e, surface for reception of head of radius, both covered with cartilage. muscles. Persons affected with this disease are com- pelled to lie in the recumbent posture, and are unable 58 BONES. to walk. When dried the bones become transparent, showing that they are composed almost entirety of animal matter. / 3. When bones contain an excess of inorganic mat- ter, they become very hard and brittle and are easily broken. The bones of old persons contain an excess of earthy matter, hence are easily broken, a simple fall being often sufficient to cause a fracture. The bones of the young contain an excess of animal matter, and will often bend before they will break. Bones broken in early life readily unite or knit by true bony union. Bones broken in old age often remain ununited or at best form a ligamentous union. Alcohol retards the union of bone by harming the digestive organs, pre- venting the formation of good blood, and destroying the white blood-cells, which are active in repairing injuries. 4. Muscles are attached to bone through the medium of the periosteum. 5. Were all the bones of the body united into one, locomotion would be impossible. The hands would be useless encumbrances were the bones of the wrist, palm, and fingers firmly soldered to each other. In order that we may execute all the motions necessary to our daily life, the bones of • our bodies occur in great numbers and come together in different ways to form joints. SECTION VII. JOINTS. 1. The structures that enter into the formation of joints are—bone, cartilage, ligaments, and synovial mem- JOINTS. hrane. Where bone enters into the formation of a joint it becomes expanded, and is composed of cancellous tis- sue with a layer of compact bony tissue surrounding it. Fig. 14. a, tibia; b, fibula; c and g', tendo Achilles; d, astragalus: e, medullary canal of tibia filled with marrow; /, os calcis, or heel-bone; g, g, g, g, ligaments; h, inter- osseous membrane. SHOWING LIGAMENTS OP ANKLE AND FOOT. The cancellous tissue diminishes shock, and thus pro- tects the delicate parts of the joint in jumping and striking. On account of the expansion of bone the joints are always larger than the parts above or 60 BONES. Fig. 15. SHOWING HEFT KNEE-JOINT. a, patella turned down; c, c, condyles of femur covered with cartilage; d,d, fat; e, femur; g, fibula; g’, tibia; h, h, h, ligaments. below, and afford a greater surface for the attach- ment of ligaments and muscles which am to hold the bones forming the joints together (Fig. 14). 2. The cartilage that enters into the formation of VARIETIES OF JOINTS. joints is of the transparent or hyaline variety. It caps the articular surfaces of the bones and acts as a buffer to diminish shock. It is not supplied with nerves, and hence is insensible to pain {d, Fig. 14; c, c, Fig. 15). 3. Ligaments are bands or straps of inelastic fibrous connective tissue which run from one bone to the other to hold them in proper position. When the ligaments be- come stretched or ruptured the joint becomes imperfect, and the bones may be displaced. Joints are also strength- ened by muscles and tendons running over them {g, g, g, Fig. 14; k, h, h, Fig. 15). 4. Synovial membranes are the oil-sacs of the joints. They are composed of very delicate connective tissue arranged in a dense manner, supporting blood-vessels and lined by from one to four layers of small flattened endothelial cells. They secrete a fluid for the lubrication of the joint, so that the motions can take place without friction. The name of this fluid is synovia. It resembles in consistence the white of an egg, and is clear or of a pale yellowish color. SECTION VIII. VARIETIES OF JOINTS. 1. Wherever bones come together they form an artic- ulation or joint. In some situations they are freely movable, in others slightly movable, and in still others immovable (Fig. 16). 2. There are several varieties of movable joints. Where motion can take place in but two directions, for- ward and backward, as in the elbow, a hinge-joint is 62 BONES. found. Where it can take place in all directions, as in the shoulder and hip, a ball-and-socket joint is found. A gliding joint is found where flat or nearly flat sur- Fig. 16. SKULL SHOWING SUTURES. a, sagittal suture; b, coronal suture; c, lambdoid suture ; e, mastoid portion; g, frontal bone; h, superciliary ridges; i, inferior maxillary bone; k, malar bone; r, superior maxillary ; p, parietal bone; s, squamous part of temporal; o, occipi- tal bone. faces of bone move on each other, as between the sternum, or breast-bone, and clavicle, bones of the carpus or wrist, and those of the scapula, or shoulder-blade, and clavicle, or collar-bone. 3. Examples of mixed joints are found in the ver- tebral column, where the bodies of the vertebras are con- fontanelt.es. nected by fibrous connective-tissue cartilage, giving great strength and limited motion, and in the articula- tions formed by the union of the ilia, or hip-bones, with the sacrum. 4. Immovable joints are found between the bones of the skull in adult life, the teeth, and the maxillary bones (Fig. 16). 5. Where the bones of the cranium unite they form sutures or seams, the most important of which are—the coronal, or crown, suture, between the frontal and two parietal bones; the sagittal, formed by the two superior borders of the parietal bones; the lamhdoid suture, formed by the posterior borders of the two parietal bones; and the occipital bone (Fig. 16). SECTION IX. FONTANELLES. 1. Where the two parietal bones unite with each other and with the frontal bone there is an absence of bony substance in early life, due to the incomplete ossi- fication of the parietal bones; and in this situation there is no bone separating the brain from external structures. An irregular space exists here through which the pulsa- tion of the brain-vessels may be felt and seen. 2. This appearance of the brain pulsation has been likened to the rising and falling of water in a fountain; hence these spaces have been called little fountains, or fontanelles (Fig. 17). 3. In very early life three of these little fountains 64 BONES. may be seen above the base of the skull: the one de- scribed above as existing between the frontal bone and the anterior superior angles of the parietal bones, called the anterior fontanelle; one between the posterior superior Fig. it. Foetal skull showing the fontanelles and centres of ossification of the bones. angles of the parietal bones and the superior angle of the occipital bone, called the posterior fontanelle; and one on each side at the posterior inferior angle of the parietal bones (Fig. 17). 4. The two last are closed at birth. The posterior one generally closes within a few months after birth, and the anterior one remains open, often, until the second year, when it is gradually closed by bone from the inner (osteo-genetic) layer of the periosteum. HYGIENE OF THE BONES. 65 SECTION X. HYQTENE OF THE BONES. 1. Healthy bone depends upon healthy marrow, healthy periosteum, healthy blood-vessels, and healthy nerves and lymphatics. These structures, in order to be healthy, must be properly taken care of and must be furnished with healthy blood. 2. The health of all the tissues and organs of the body, including the bones, depends upon a healthy digestive system, furnished with healthy food and drink, and kept in order by carefully obeying the laws of health. 3. Moderate active exercise, as walking and horse- back riding, facilitates digestion, the appropriation of new food-material by the body, the removal of worn-out matter, the introduction of oxygen, and the discharge of carbonic acid gas, and is thus conducive to healthy bone-growth. 4. Very active exercise, as running, jumping, and dancing, should never be violent or prolonged to the extent of causing marked fatigue. Violent exercise indulged in for a short time causes more profound res- piratory efforts, a more complete and thorough change of air in the deeper portions of the lungs, rapid appro- priation of oxygen by the tissues, hastened circulation of the blood, and active discharge of effete matter. Thus far it is beneficial, but when carried too far it often causes tissue-waste to an extent beyond repair, producing con- gestions and inflammations of various organs, ending in diseases which oftentimes cause death. 5. The so-called “ growing-pains ” of children, which BONES. are generally referred to the neighborhood of some joint in the extremities, are often produced by violent exer- cise. A severe shock to the bone, produced by a jump, causes a rupture of the delicate parts in the immediate vicinity of the joint, generally at the zone of greatest physiological activity. This causes an inflammation, pressure on the delicate nerve-endings, and pain. If the injury be slight, no further trouble is experienced than the “ growing-pains,” and the damage is soon re- paired. If the injury be extensive, however, inflamma- tions of the bone, periosteum, and marrow may be started which will prove a source of pain and trouble for many years. 6. Tight garments, unyielding bands, and bandages should never be worn, no matter how fashionable the dress or imperative the demands of fashion may be. They cause congestion of the vessels by pressure, turn back the blood, and interfere with the nutrition of the tissues. The liver, heart, and lungs have been driven from their normal position, and the stomach so squeezed and deformed by tight lacing as to be unable to per- form its function or to hold food enough to nourish an infant. The ribs have been so pushed in and deformed by the repeated application of tight, neat-fitting cor- sets that the liver after death has been found to bear the marks of their pressure. (See Fig. 18 for normal thorax; also Fig. 46.) 7. By compressing the ribs and muscles of the abdo- men to make a neat waist the intestines, liver, kidneys, spleen, pancreas, and stomach are crowded together and pushed up against the diaphragm, displacing the heart and lungs upward and interfering with respiration HYGIENE OF THE BONES. and circulation. Many cases of functional heart dis- ease, shortness of breath, and marked forms of indigestion and dyspep- sia in fashionable fe- males are occasioned by tight lacing. A notice- ably small waist is a deformity as little to be desired as a withered limb or a broken bone. Fig. 18. 8. Alcohol predisposes to the fracture of bones, by, in small quantities, stimulating the nervous system, exciting the muscular system, crip- pling the judgment of the unfortunate victim of its use, and causing him to do many unwise and dangerous things which he would not do in a sober state. In large doses it paralyzes the muscles and mad- dens the brain, so that they cannot take care of the bones and guard against accidents. Hos- pital statistics show that were it not for the intemperate use of alcohol in some form, NORMAL THORAX, VERTEBRAL COLUMN, AND PELVIS. a, a, a, ribs; 6, b, b, costal cartilages; c, c, c, c, floating ribs; d, sternum or breast-bone. 68 BONES. Fig. 19. at least one-third of the beds in the surgical wards could be dispensed with, thus showing that the inebriate not only deprives his wife and children of that physical and moral support which it is his natural and imposed duty to fur- nish, but he becomes a burden to him- self and a care and expense to others in the last days of his helplessness. 9. When bones are fractured or broken, they should be set at the ear- liest possible moment. Often the broken ends will adjust themselves. Especially is this true where the limb is put in the proper position to insure relaxation of the muscles. A patient with a broken bone, arm or leg, should never be handled until the limb is supported by some kind of splints. When the leg is broken, the patient should not be allowed to at- tempt to walk, nor should he be carried without first applying some supporting body or bodies to the sides of the limb; and the broken bone should never be examined through the clothing. This should be cut and not pulled off. By lifting a broken limb without first sup- porting it, an end of the bone may penetrate the skin and convert a simple fracture into a compound one. An um- brella, a cane, lath, long stick, or pieces of paper folded into thick layers and applied to each Eesult of a badly-set fracture, from a cast of the arm of the great African explorer Liv- ingstone. HYGIENE OF THE BONES. 69 side of the limb, with a handkerchief or twine to hold them fast, is all that is necessary while removing the patient to his home or waiting for the physician. When- ever practicable, hones should be set before the patient is 'moved. Once in proper position they should he let alone. Nature now must do the work of repairing. Unnecessary and unwise handling will be productive of useless pain and delayed union (Fig. 19). 10. Composition of Bone.—Bone contains about one- third organic or animal matter and about two-thirds in- organic or earthy matter. 11. The Chemical Composition of Bone, according to Berzelius, is as follows: Organic matter, Gelatine and blood-vessels .... 33.30 Phosphate of lime 51.04 Carbonate of lime 11.30 Fluoride of calcium 2.00 Phosphate of magnesia 1.16 Soda and chloride of sodium ... 1.20 100.00 Inorganic or Earthy matter. To this some chemists add 1 per cent, of fat. 12. By burning bone for some time the animal matter is consumed, leaving the earthy matter, which, though retaining the original shape, is very brittle, and will break to pieces by simply letting it fall upon the floor. 13- By acting upon bone with a dilute mineral acid the inorganic matter is rendered soluble and removed, leaving the animal matter, which still retains the shape, is very flexible, easily cut with a knife, and can be tied into a knot. 70 BONES. SECTION XI. THE VERTEBRAE. 1. The Vertebral Column.—The number of vertebrae in the back-bone, or spinal column, is twenty-six. Each vertebra or segment of the column is composed ol two parts—an anterior part or body (a, Fig. 20), and a pos- terior part or arch (Fig. 20). 2. The arch supports the following processes: two transverse, four articular, and one spinous (Fig. 20). 3. The arch is composed of two pedicles and two laminse. The two pedicles spring from the body at the junction of its posterior with its lateral surfaces. The two laminse are flattened continuations of the pedicles, and, after converging, fuse behind to form the spinous process. 4. The pedicles have a general direction backward, and often a little outward. The two laminse take a direction inward, and generally a little downward, thus enclosing an open space bounded in front by the pos- terior surface of the body, behind by the converging laminse and the anterior part of the spinous process, laterally by the inner surfaces of the pedicles and laminse. This opening, with those in the other vertebrse, forms, when all the segments are articulated, the spinal canal and lodges the spinal cord. 5. The bodies are the heaviest and most massive parts of the vertebrse (a, Fig. 20). They are composed of spongy tissue covered with a thin layer of compact tissue. They are flattened above and below, are rough, and have placed between them disks of fibrous connective tissue THE VERTERRJE. 71 Fig. 20. VERTEBRAE. a, lumbar; b, axis; c, atlas; d, typical dorsal vertebra; d, d, d, d, articular sur- aces between which the turning movements of the head take place. 72 BONES. which bind them closely together and act as elastic cushions for protection and to prevent shock. 6. The bodies of the vertebrae differ in shape and size in the different regions of the spine. In the cervical (or neck) region they are smaller than in any other region, except the coccygeal. Their greatest diameter is transversely, or from side to side, their smallest diam- eter being antero-posteriorly, or from before backward. Hence the to-and-fro (or forward and backward) motion in the neck is greater than the lateral, or from side-to- side, motion. The first cervical vertebra (called the atlas, because it supports the globe or head) has no body and no spinous process (Fig. 21). It articulates above with the condyles, or knuckles, of the occipital bone, and .between these bones the nodding motion of the head takes place (c, c, c, c, c, c, Fig. 21). The second cervical vertebra (b, Fig. 20) has developed upon ' its upper surface the body of the first. This process is pointed and in shape not unlike a tooth. It is called the odontoid process. This bone articulates above with the inferior surface of the first cervical vertebra (atlas), and between these surfaces the rotatory or turning mo- tions of the head take place (d, d, d, d, of h and c, Fig. 20). The seventh cervical vertebra is peculiar on account of its largely-developed spinous process, and is called the vertebra jprominens. All of the cervical vertebrae have holes or foramina in the bases of their transverse processes for the transmission of vessels. The number of cervical vertebra} is seven. 7. The Dorsal Vertebrae are twelve in number, and have the ribs attached to them on each side. Their bodies are larger and heavier than those of the cervical THE VERTEBRAE. FIG. 21.—OCCIPITAL BONE AND FIRST CERVICAL VERTEBRA. a, occipital; b, atlas; e, c, c, e, c, c, surfaces between which the nodding motion takes place. 74 BONES. region, and have their greatest diameter from before backward and their least diameter from side to side; hence there is greater lateral than forward and backward motion in this region. The bodies are thicker behind than in front, and when piled one upon the other cause this region to be concave in front and convex behind. These vertebrae bear articular surfaces on their bodies and (with few exceptions) on their transverse processes for articulation with the heads and tubercles of the ribs. The spinal foramen is round or nearly so, and smaller than in the cervical region, where it is triangular in shape and larger than in any other part of the spine {d, Fig. 20). 8. The Lumbar Vertebrse are heavy and massive (a, Fig. 20), thicker in front than behind; hence in this region there is a convexity in front and a concavity behind. When very marked this produces sway-back. The spinal foramen in this region is triangular in shape, larger than in the dorsal region and smaller than in the cervical. 9. The Sacrum, though one bone in adult life, is composed in early age of five bones. These become firmly united or ossified into one piece, forming the sacrum, which is pyramidal in shape, with its apex down and its base up, forming the posterior and upper boundary of the pelvic cavity, where it is wedged in between the two innominate bones at the sides, the lum- bar vertebrse above, and the coccyx below (6, Fig. 22). 10. The Coccyx is a small triangular bone composed in early life of four separate pieces, which become ossi- fied into one in the adult. It is pyramidal in shape, with its base up toward the apex of the sacrum and its THE VERTEBRAE. a, a, a, bodies of lumbar vertebrae ; b, sacrum; c, coccyx ;d,d,d, d, ossa innom- iuata; p, femur; p', its head exposed by cutting the ligament away; e, e, ligaments. FIG. 22.—PELVIC BONES. 76 BONES. apex down. All the vertebrae composing it are rudi- mentary and not well developed. It forms a movable articulation with the apex of the sacrum, which, how- ever, sometimes ossifies, so that the sacrum and coccyx practically become one bone (c, Fig. 22). SECTION XII. CRANIAL OR HEAD BONES. 1. The bones of the head or cranium are eight in number. They are modified vertebrae to contain the anterior enlarged part of the spinal cord, the brain. The names of the bones are—Occipital, two Parietal, Sphenoid, Ethmoid, Frontal, and two Temporal. 2. The Occipital bone is at the posterior part of the head, and forms the convex projection in this region. It articulates with the posterior borders of the two parietal bones in front, and its inner surface is concave and presents four depressions or concavities. The two upper ones receive ther posterior lobes of the cerebrum, and the two inferior ones the posterior lobes of the cerebellum. In its base is a large oval opening, the foramen magnum. This transmits the medulla oblongata, which is continuous below with the spinal cord (a, Fig. 21). 3. The two Parietal bones form the sides and vertex of the head. They articulate with the frontal bone in front and with the occipital behind (Fig. 9). 4. The two Temporal bones are situated at the sides and base of the cranium. Each temporal bone is divided into three portions: squamous, or scale portion; mastoid, or nipple or teat-like portion; and petrous, or hard, stone- CRANIAL OB HEAD BONES. 77 like portion. The mastoid portion {e, Fig. 16) forms the projection immediately behind the ear. It contains a number of spaces or cavities which communicate with the middle ear. These cavities are called the mastoid cells, and are separated from the brain above by a very thin plate of bone. Diseases of the throat may travel up the Eustachian tube into the middle ear, and then into the mastoid cells. 5. The Petrous portion is hard and stone-like, and contains the most important organs of hearing. 6. The Squamous portion is thin and translucent, and overlaps the inferior border of the parietal bone. The squamous portion has running outward and for- ward from its lower part the zygomatic process, which articulates with the malar or cheek-bone in front, form- ing the ridge which runs from the cheek backward to the anterior part of the ear. 7. The Sphenoid and Ethmoid are two very compli- cated bones wedged in at the base of the skull. They help support the brain, have a number of processes for the attachment of its membranes, and a number of openings for the transmission of nerves and blood- vessels. 8. The Frontal bone forms the forehead (g, Fig. 16). It articulates behind with the anterior borders of the parietal bones, and its internal surface lodges the ante- rior lobes of the cerebrum. At the upper part of the orbit, or cavity for the eyes, it presents a distinctly curved arch—the supraorbital arch—and running back- ward from this is the horizontal portion of the bone, articulating with the sphenoid behind and forming the roof of the orbit. Above the supraorbital arches, and 78 BONES. corresponding with the eyebrows, are two ridges of bone called the superciliary ridges (h, Fig. 16). They in- dicate the position of the frontal sinuses, which are open spaces developed between the two tables of the frontal bone, containing air and communicating with the nasal cavity. They are not developed in early life. SECTION XIII. BONES OF THE FACE. 1. There are fourteen bones in the face: two Superior Maxillary; two Nasal; two Inferior Turbinated; two Malar; two Palate; two Lachrymal; one Vomer; and one Inferior Maxillary. 2. The two Superior Maxillary bones (i, Fig. 16) are numbered among the largest bones of the face. Their nasal processes, with the nasal bones, form the sides and bridge of the nose. The anterior part of their bodies forms that portion of the face between the malar or cheek-bones above and the upper teeth below. Their palate processes, with the palate-bones, form the bony roof of the mouth or hard palate and the floor of the nasal cavities. Their inferior borders are thickened and present a number of openings—alveolar openings —for the reception of the roots of the upper teeth. 3. The Inferior Maxillary bone (i, Fig. 16) is the largest bone of the face. It has a body or curved horse-shoe- shaped portion, to which numerous muscles of the mouth and neck are attached, and the upper border of which is also thickened and contains a number of openings to BONES OF THE FACE. 79 receive the roots of the lower teeth. Arising from the body on each side at nearly a right angle are the two rami or branches. Each of these are bifurcated and pre- sent surfaces for muscular and ligamentous attachment. The posterior branch of each ramus is thickened and rounded, not unlike a knuckle. It is called the coiidyle, and articulates with the glenoid fossa on the under sur- face of the temporal bone. This joint makes it possible to open and close the mouth. 4. There are two Lachrymal bones, one on each side. They are situated at the inner and front part of the cavity for the eye. They are the smallest bones of the face, and are very delicate in structure. Their outer surfaces form part of the inner wall of the orbital cav- ities, their inner surfaces part of the outer wall of the middle openings of the nose. The anterior portion of the outer surface aids the nasal processes of the superior maxillary bone in completing the lachrymal groove, the upper part of which lodges the lachrymal sac, and the lower part helps to form the lachrymal canal, which lodges the nasal duct. This duct carries the tears from the under part of the eye to the inferior meatus of the nose, where they are evaporated by the air as it passes m and out during the acts of respiration. 5. The Malar bones are two in number, one on each side. They form the prominence of the cheek. 6. The Vomer is a long plate articulating above with the sphenoid and below with the superior maxillary and palate bones. It is situated vertically in the poste- rior part of the nasal fossse, forming the back part of the septum of the nose. 7. The two Inferior Turbinated bones—one on each 80 BONES. side—are scrolls of spongy bone situated horizontally, from before backward, in the nasal cavity, and attached to its outer wall. These bones separate the middle from the inferior meatus of the nose. 8. The Palate bones are two in number, one on each side. They are very irregular bones, and are situated between the sphenoid behind and the superior maxillary bones in front. They help form the roof of the mouth behind and the posterior part of the floor and sides of the nasal cavity. They also have processes entering into the formation of the floors of the orbital cavities. 9. The Nasal bones are two in number. They artic- ulate with the frontal bone above, with the nasal pro- cesses of the superior maxillary at the outer sides, and with each other in the median line, forming the bridge of the nose. SECTION XIV. RIBS AND STERNUM. 1. There are twelve ribs on each side (a, a, Fig. 18). They articulate with the dorsal vertebra behind, and, with the exception of the lower five, the sternum in front. The seven upper ribs are called the true, or ver- tebrosternal, ribs. The lower five are called the false ribs; of these the three upper ones are called the verte- hro-chondral, because they articulate with the vertebrae behind and the costal cartilages in front (5, b, b, Fig. 18). The lower two are called the vertebral—free or floating ribs. They have no attachment in front, but are at- tached to the vertebra behind (Fig. 18). BIBS AND STERNUM. 81 2. The direction of the ribs is from behind forward and from above downward. They are curved upon themselves, and run from the vertebrse behind to the sternum and costal cartilages in front, enclosing a cavity —thoracic cavity—which is bounded above by the root of the neck; behind by the dorsal vertebrae and ribs; laterally by the ribs ; in front by the sternum, costal cartilages, and ribs; and below by the muscular dia- phragm, which separates it from the abdominal cavity. This cavity contains the heart, lungs, and large blood- vessels. 3. The Sternum {d, Fig. 18) is a flat bone situated in the anterior part of the chest, forming the anterior boundary of the thoracic cavity. It is broader above than below, and consists of three parts. The first piece is called the manubrium, the second the gladiolus, and the third the ensiform or xiphoid appendix. It has been compared in shape to an ancient sword, and the three pieces named the handle, blade, and point. It has artic- ulating with it above on either side the clavicle or collar- bone, on the sides the costal cartilages. Its point is car- tilaginous and is free or imbedded in the muscles of the abdomen. A little below the episternal notch—which is between the two inner ends of the clavicles in the me- dian line—there can be felt an elevation running trans- versely which indicates the point of union of the first with the second piece. This ridge is opposite the second rib (i, Fig. 18), and is considered, by physicians, an im- portant landmark in examinations of the heart and lungs. 82 BONES. SECTION" XV. THE SHOULDER-GIRDLE AND UPPER EXTREMITIES. 1. There are two bones in the shoulder-girdle—the scapula and clavicle—and they serve to attach the upper extremity to the central skeleton (Fig. 23). 2. The Scapula, or shoulder-blade, is a flat triangu- lar bone situated at the upper and posterior part of the thorax. It is imbedded in a mass of muscles which serve to hold it to the body. It articulates with the outer end of the clavicle, and presents, above and in front, an articular surface to receive the head of the humerus, forming the shoulder-joint {h, c, Fig. 23). A very dis- tinct ridge of bone divides its posterior surface into two parts. This ridge is called the spine of the scapula, and can be felt running toward the median line from the outer and back part of the shoulder. It strengthens the bone and gives increased surface for muscular attach- ment. 3. The Clavicle, or collar-bone (g, Fig. 23), is shaped somewhat like the italic letter/. It is a strong bone, rather cylindrical in shape, articulates with the acromion process of the scapula externally, and with the upper end of the sternum internally. To it muscles of the neck and thorax are attached. This bone is frequently fractured in children, and when this accident occurs the hand of the injured side should be laid on the breast, the arm pushed back, and the shoulder raised. This puts the broken ends of the bone in the best possible position, which should be maintained until the arrival of the physician. THE SHOULDER-GIRDLE, ETC. 4. The Humerus is a long cylindrical bone articulat- ing with the head of the scapula above (b, c, Fig. 23) Fig. 23. a umerus; globular head of the same; c, glenoid cavity on head of scap- a or its reception; d, capsular ligament of the joint; e, scapula; /, its acromion process; g, clavicle; h, h, h, ligaments. LEFT SHOXJXUEE-JOINT. 84 BONES. and with the radius and ulna below (e, e, e, Fig. 24). This bone forms the arm, and has many muscles attached to it. Where it articulates with the scapula Fig. 24. EIGHT EEBOW-JOINT, ANTERIOR VIEW. a, a,- a, a, ligaments; 6, humerus sawed off; c, ulna: d, radius; e, e, e, articular end of the humerus covered with cartilage. it forms the shoulder-joint, and where it meets the radius and ulna it forms the elbow-joint (Figs. 24, 25). 5. The Radius (a, Fig. 25) is one of the bones of the forearm, and is placed external to the ulna. It is smaller above than below, and has developed on its upper extremity a rounded portion called the head, which articulates with the outer part of the lower end THE SHOULDER-GIRDLE, ETC. of the humerus above and with a depression on the outer surface of the upper end of the ulna at the side. Its lower end is large and rather flattened, and articulates with the scaphoid and semilunar bones of the first row of the carpus. When the palm of the hand is turned Fig. 25. ELBOW - JOINT OF LEFT SIDE, INTERNAL VIEW. a, radius; b, ulna. down, as in pronation, the lower end of the radius crosses the lower end of the ulna, while its upper end still retains its external position (h, Fig. 10). When the back of the hand is down, as in supination, the two bones lie parallel to each other (a, Fig. 10). 86 BONES. 6. The Ulna (c, Fig. 24; b, Fig. 25) is larger above than below, and enters more largely into the formation of the elbow-joint than the radius. Below it articulates with the side of the radius, but is separated from the bones of the carpus by the interposition of a triangular fibro-cartilage. The sharp point of the elbow is formed by the olecranon process of the ulna. 7. The Carpal bones, or bones of the wrist (c, Fig. 8 and Fig. 26), are eight in number, and are arranged in two rows. Those in the first row are—the scaphoid, semilunar, cuneiform, and pisiform; those of the second row are the trapezium, trapezoid, os magnum, and unciform. They are short bones, with their articular surfaces covered with cartilage. They give great strength and limited motion. The scaphoid, semilunar, and cunei- form bones, with the lower end of the radius and the lower surface of the interarticular fibro-cartilage at the lower end of the ulna, form the wrist-joint. 8. The Metacarpal bones, or bones of the palm, are five in number, one for each finger and the thumb. The phalanges are fourteen in number, three for each finger and two for the thumb (1, 1, 1, 1, 1, 2, 2, 2, 2, 2, Fig. 26). SECTION XVI. PELVIC GIRDLE. 1. There is one bone in the pelvic girdle on each side, the os innominatum: this is composed of three bones in early life, the ilium, ischium, and pubes (d, d, Fig. 22). 2. The two ossa innominata, with the sacrum and coccyx behind, form the bony wall of the pelvic cavity. PELVIC GIRDLE. 87 Fig. 26. SHOWING bones and ligaments of the weist and hand. The red coloring shows position of interossei muscles, posterior view: a, radius; ’ u*nai c, interosseous membrane; 1,1,1,1,1, metacarpal bones; 2, 2, 2, 2,2, Phalanges. 88 BONES. 3. The lower extremity is attached to tin, central skeleton through the os innominatum. 4. The Femur (Figs. 27 and 30), or thigh-bone, articulates with the cotyloid cavity or acetabulum on the outer side of the os innominatum (p, Fig. 22, and e, h, Fig. 27). It is a long bone, and helps form the knee- (c, c, Fig. 15) and hip-joints, has numerous muscles attached to it, and protects nerves and blood-vessels. In early life this bone is composed of a number of pieces —five—which are not solidly united until the twentieth year of age (Fig. 30). It articulates above with the in- nominate bone to form the hip-joint, and below with the tibia and patella to form the knee-joint (g', a, Fig. 15). The hip-joint is a ball-and-socket joint. The knee-joint is a hinge-joint. 5. The Tibia and Fibula ( Internal Cuneiform, Middle Cuneiform, External Cuneiform, ’ First, Second, Third, Fourth, Fifth, First Row, 5, 2 2 2- 2 2 2 2 2- 10 -14 -10 Phalanges, 14: ■ Second Row, 5, 10 Third Row, 4, 8- -28 Patella, or knee-pan, 1 on each side, 2- _ 2 126 3. History.—With the exception of the bones, the earliest medical men knew very little of the structure of the human body, for they were not permitted to dis- sect. Definite knowledge of human anatomy began with the foundation of the Greco-Egyptian school of medicine, founded at Alexandria in Egypt about three hundred and twenty years before Christ. The founders of the school licensed the dissection of human bodies, and medical men from all parts of the known world repaired there for instruction. This practice prevailed but a short time, and the dissection of the human body disappeared from history for twelve centuries. The Ro- mans, who gloried in the sight of blood in the arena and on the field of battle, not only burned their dead, but made dissection a crime, and not a single anatomist of any repute obtained his training in Rome. Even the celebrated Galen was compelled to go to Alexandria to see the human skeleton, and, as dissection was no longer QUESTIONS. practised there, he sent his students to the battle-fields of Germany to dissect the bodies of the slain. With the death of Galen ended the anatomic period in medicine, a. d. 200. He was at one time court-physician at Rome, was an extensive writer, and is said to have been pro- foundly versed in osteology. He described, individually, nearly all the bones of the human skeleton, and in his works there are few that are not named. QUESTIONS. SECTION I. Of what is bone composed? What does the matrix support?(l). Of what is the matrix formed ?(2). What are the soft structures of bone?(3). What is the periosteum? What is' attached to it? Into how many layers can it be separated? What is the character of the upper layer? Why is a bone felon so painful? What is the name of the inner layer of the periosteum? Is it as dense as the outer layer? What does this layer contain ? What are osteoblasts ? How does the inner layer communicate with the marrow? If the periosteum were cut away from bone, would the bone die?(4). What is the structure of marrow ?(5). How many kinds of marrow are there?(6). Where is red marrow found ?(f7). Where is yellow marrow found? How does it differ from red marrow ? Which is active in bone-formation ?(8). How many kinds of bone are there? What are they? Where is compact bone found ? Where is spongy bone found ?(1). For what pur- pose is bony surface increased ?(2). What color is healthy bone?(3). SECTION 11. Into how many classes are bones divided for description ? Name thera(l). Where are long bones found? Name the parts of a long bone. What kind of tissue composes the shaft? What kind of tissue is found in the extremities? What caps the ends of long bones ? What are the Haversian spaces? and what do they contain ?(2). Give ex- amples of long bones(3). Where are short bones found ? Of what are SECTION 111. 96 BONES. they composed? At what points are they coated with cartilage?(4.) Give some examples of short bones(s). Where are flat bones found? Of what are they composed? What covers them? What are the com- pact plates of bone covering the cranial bones, called ? What is the diploe?(6). Give some examples of flat bones(t7). Where are irreg- ular bones found? Of what are they composed?(B). Give some ex- amples of irregular bones (9). What is the skeleton ? What is meant by exoskeleton ? By endo- skeleton ? In what animals are exoskeletons found ? In what animals are endoskeletons found ?(1). Into how many parts is the skeleton of man divided? Name them (2). What bones compose, the axial skeleton ?(3). What bones compose the appendicular skeleton ?(4). How many bones in the central skeleton ? How many in the peripheral skeleton ? How many in the entire skeleton ? Ho the teeth belong to the skeleton ?(5). SECTION IV. SECTION V. Of what is bone composed?(l). What is osseous tissue? What are the canaliculi ? What are the lacunae ?(2). What do the lacunae contain ? What are in the canaliculi ? Do the lacunae communicate with each other? Do the processes of one cell ever touch those of its neighbor ?(3). How are the bony laminae arranged in compact tissue ? Describe the formation of Haversian canals and Haversian systems(4). What holds the Haversian systems together?(s). What are the circumferential lamellae? How are Haversian spaces formed ? Do they exist in cancellous bone ?(6). What part of the body do bones form ? How are they useful in loco- motion ?(1). What makes bone hard ? What makes it elastic ? What is the condition of the bones in the disease mollifies ossium? Can persons who have this affection walk ? Why not?( 2). Will the bones of old persons break easily ? Why ? Why will very young healthy bone bend? When the bones of the aged are broken will they unite or knit readily ? Why not ? How does alcohol act to retard bone-union ? (3). By what are the muscles attached to bone?(4). Would it be possible to walk were all the bones of the body united into one? In order that locomotion may be possible, how must our bones be arranged ? When bones come together, what do they form?(s). SECTION VI. QUESTIONS. 97 SECTION VII. What structures enter into the formation of joints? Why are the joints larger than parts of bone above Of below them ? What holds the bones forming a joint together ?(1). What kind of cartilage enters into the formation of joints ? How does it act to diminish shock ? Has car- tilage sensibility? Why not?(2). What are ligaments? When the ligaments become ruptured, what may happen to the joints? What other structures strengthen joints?(3). What are synovial membranes? Of what are they composed ? What kind of cells line the synovial sacs? What do they secrete ? What is the name of this fluid ? What does it resemble in looks and in consistence ?(4). SECTION VIII. How are joints or articulations formed ? As regards motion, how many kinds of joints are there?(l). What is a hinge-joint? In how many ways can motion take place in hinge-joints? Give an example of a hinge-joint. How is a ball-and-socket joint formed? What kind of motion will be permitted by a ball-and-socket joint? Give an example or examples of a ball-and-socket joint. How is a gliding joint formed ? Name some bones between which or by which gliding joints are formed (2). What are mixed joints? What advantage do mixed joints give? Give examples of mixed joints. What holds the different segments of the back-bone together ?(3). What are immovable joints? How are immovable joints formed? Are the bones of the cranium firmly united in early life? Give examples of immovable joints (4). What do the bones of the cranium form at their points of union ? Name the most important sutures or seams of the head. Between what bones is the coronal suture found? Between what bones is the sagittal suture found? Between what bones is the lambdoid suture found ?(5). SECTION IX. What are fontanelles? How are they formed? What can be seen and felt at the situation of the fontanelle?(l). What has given rise to the name “fontanelle” ? What does the word mean?f2). How many fontanelles may be seen above the base of the skull in early life ? Where is the anterior fontanelle? Where is the posterior fontanelle? Name the location of a third one(3). Which fontanelles are closed at birth? When does the posterior one close ? At what time does the anterior fontanelle generally close? What is the source of the bone that closes the fontanelles ?(4). 98 BONES. SECTION X. Upon the health of what structures does the health of bone depend ? How may these structures be kept in a healthy condition ?(1). Upon what does the health of all the tissues and organs of the body depend ?(2). What benefit is derived from moderate exex-cise? How does it affect bone-growth ?(3). To what extent should very active exercise be car- ried ? What effects are produced by very active exei’cise indulged in for a short time only ? What effects are produced by very active exercise when carried too far?(4). How are growing-pains in the region of joints often caused ? At what part of the joint does the injury generally take place ? How is the pain produced ? What effect is produced when the injury has been very extensive ?(5). Why should tight garments, bands, and bandages not be worn? Is it possible to produce deformity by the repeated application of tight articles of dress?(Q). How are respiration and cii’culation affected by tight lacing? Are functional diseases of the heart ever produced by tight lacing? What sometimes causes dyspepsia ?(7j. How does alcohol predispose to the fracture of bones ? Does the use of alcohol increase the number of surgical cases in the wards of hospitals ? Does the use of alcohol damage the user alone, or does it affect others as well ?(8). When should bones be set ? Will the broken ends ever adjust themselves? Should a broken limb be handled without first supporting it ? Should a patient be allowed to at- tempt to walk with a broken leg ? Should a broken bone be examined through the clothing? How should the clothing be removed? Why? What may be used as temporary supports to a broken bone while mov- ing the patient? If practicable, should a bone be set before moving the patient ? When once properly. set, should a broken bone be handled ? Why not?(9). What is the relative amount of animal and earthy matter in bone?(10). What is the chemical composition of bone?(ll). How may bone be deprived of its animal matter ?(12). How may it be deprived of its earthy or inorganic matter ? When can bone be tied into a knot?(13). SECTION XI, How many vertebrae in the back-bone? Of how many parts is each vertebra composed? Name them(l). How many processes does the arch support? Name them(2). What pieces compose the arch? From what part of the body do the pedicles spring? What are the laminae? How is the spinous process formed?(3). What is the direc- QUESTIONS. 99 tion of the pedicles? Of the laminae? What space do they inclose? Bound this opening. What does this opening, with those of the other vertebrae, form ? What does the spinal canal contain ?(4). What parts of the vertebrae are the heaviest ? Of what kind of tissue are they com- posed? What is their shape? Are their surfaces smooth or rough? What is placed between them? What function does it subserve?(s). Bo the bodies of the vertebrae differ in shape and size in the different regions of the spine ? Describe the cervical vertebrae. What motion is greatest in the neck? Why? What is peculiar about the first cervical vertebra? What is its name? Between what bones does the nodding motion of the head take place? What is peculiar about the second cervical vertebra ? Between what bones does the turning motion of the head take place? What is peculiar about the seventh cervical vertebra? W hat is peculiar about the transverse processes of all the cervical ver- tebrae? How many cervical vertebrae are there ?(6). How many dor- sal vertebrae are there? What is attached to their sides? Describe the bodies of the dorsal vertebrae. What motion is greatest in the dorsal region ? Why? Are the bodies of the dorsal vertebrae thicker in front or behind? What condition does this produce? What are found on the sides of these vertebrae? For what purpose? What is the shape of the spinal foramen ? What is its size as compared with the other regions of the spine Describe the lumber vertebrae. How is sway-back produced? What is the shape and relative size of the spinal foramen in the lumbar region ?(8). Of how many pieces is the sacrum composed? hen do they become united into one piece ? What is the shape of this bone ? Does its base look up or down? What cavity does it assist in ounding ? Between what bones is it situated ?(9). Of how many pieces \V-^le COCC'X comPosed? When do they unite? What is its shape? ith what bone does it articulate? Does it ever become firmly united fo this bone?(10). SECTION XII. How many bones in the head? What are these bones? What do tie} contain? What is the brain? Name these bones(l). Locate and t esciibe the occipital bone. With what bones does it articulate ?(2). ocate the parietal bones. With what bones do they articulate ?(3). heie aie the temporal bones situated? Of how many parts is each composed ! Describe the mastoid portion. What are the cells within this portion called ?(4). What is the character of the petrous portion ? hat important structures does it contain ?(5). What is the character of the squamous portion ? With what part of what bone does it artic- 100 BONES. ulate? What process has the squamous portion? With what bone does it articulate? What prominent ridge does it form?(6j. Where are the sphenoid and ethmoid bones situated ? Give a gross description of them(7). What does the frontal bone form? Describe as much of this bone as you can. With what do the frontal sinuses communicate? What do they contain ? Are they developed in early life ?(8). SECTION XIII. How many bones in the face? Name them(l). Describe the supe- rior maxillary bones. What part of the nose do they help to form ? What part of the face do their anterior surfaces form? What do their palate processes help to form? What is peculiar about their inferior borders? What teeth do they receive?(2j. How many parts has the inferior maxillary bone? What teeth does it receive? What joint does it help to form?(3). Where are the lachrymal bones situated? Are they large or small bones ? What two cavities do they assist in form- ing? What groove do they assist in forming? What does this groove contain? What does the nasal duct carry? What becomes of the tears after they enter the nasal cavity ?(4). How many malar bones are there? What do they form?(s). Describe the vomer. What does it assist in forming? With what bones does it articulate?(6). How many inferior turbinated bones are there ? What kind of bones are they ? In what direction do they run ? In what cavity are they found ? How does it divide this cavity?(7). How many palate-bones are there? Are they regular in shape, or irregular? What cavities do they assist in forming?(B). How many nasal bones are there? With what bones do they articulate? What part of the nose do they form?(9). SECTION XIV. How many ribs are there on each side? With what do they artic- ulate in front and behind? What are the seven upper ribs called? The lower five are called what? What is the name of the upper three of the lower five? Which are the free or floating ribs? To what are they attached behind ?(1). What is the direction of the ribs? What cavity do they help inclose? Bound the thoracic cavity. What sepa- rates it from the abdominal cavity below ? What does this cavity con- tain ?(2). What kind of a bone is the sternum? Where is it situated? Of how many pieces is it composed ? Name them. To what instrument of war has it been likened ? With what bones does it articulate ? What causes the ridge on the sternum opposite the second rib?(3). QUESTIONS. 101 SECTION XV. How many bones in the shoulder girdle ? Name them. What is their function ?(1). Describe the scapula. With what bones does it articulate? What joint does it help to form? (What kind of a joint is the shoulder-joint ?) What is the spine of the scapula ? What does it do?(2). What is the shape of the clavicle? With what bones does it articulate? What is attached to it? Is this bone frequently fractured? When this accident happens, into what position should the arm be P«t?(3). What kind of a bone is the humerus ? With what bones does it articulate? What part of the upper extremity does the humerus form? What is attached to it? What joints does it help to form? What kind of a joint is the elbow-joint ?(4). What is the radius? M hat is its position with reference to the ulna? What is the head of the radius? With what does it articulate? What is the shape of its lower end? With what bones does it articulate? In what position of the hand does the radius cross the ulna ? When do the bones lie paral- lel ?(5). Is the ulna larger above or below ? What joint does it help to form above? What separates its lower end from the bones in the first row of the carpus ? What forms the prominent point of the elbow?(6). How many carpal bones are there? How many rows do they form? Name the bones in the first row. In the second. What kind of bones are they? What covers their articular surfaces? Does great range of motion take place between them ? Do they form strong articulations ? Name the bones entering into the formation of the wrist- ,|oint(V). How many metacarpal bones are there? What part of the hand do they form ? How many phalanges are there ? How many for each finger? How many for the thumb?(B). SECTION XVI. How many bones in the pelvic girdle? Of how many pieces is each composed in early life? What are they?(l). What bones form the ony pelvis?(2). How is the lower extremity attached to the central skeleton ?(3). Describe the femur(4). Where are the tibia and fibula found? Which is the stronger bone?(s). Describe the fibula. With ■what bones does it articulate?(6). What bones form the malleoli?(7). How many bones in the tarsus? Name them(B). How many meta- tarsal bones? How many phalanges in the foot?(9). 102 BONES. SECTION XVII. How many bones in the central skeleton? Write the bones of this part of the skeleton upon the hlackboard(l). How many bones in the appendicular skeleton? Write them upon the blackboard(2). Did the earliest medical men know very much of the structure of the human body ? Why not ? From what period does definite knowledge of human anatomy date ? What advantages were offered to students of anatomy by the Alexandrian school ? Did the Duma ns permit the dissection of human bodies ? How did students of anatomy in Dome obtain material for dissection ? Who was Galen ? Did he possess a knowledge of the skeleton? When did he die?(3). CHAPTER V. VASCULAR SYSTEM. SECTION I. 1. The vascular system is composed of the heart, arteries, capillaries, and veins. It is a system of tubes or pipes to distribute blood to the tissues and lungs, and to return it to the heart again. 2. The lowest animals have no such system of tubes to bring them nourishment and to carry off their waste matter. They use the fluid in which they live as blood, and all parts of their bodies take from this fluid all that is necessary for their growth. It is only in the highest animals that there is a perfect circulatory system. 3. The heart is the great vascular pump of the body; it is the beginning and the termination of the circulatory apparatus. In the human being it is rather pyramidal in shape, with rounded sides, apex, and base. 4. It is situated in the thoracic cavity, with its base looking up and rather to the right side, its apex looking down and to the left. It is nearer the anterior part of the thoracic cavity than the posterior, and is situated between, and in inspiration nearly covered by, the lungs (Figs. 31, 40, 41). 5. Its base is partly on the right and partly on the 104 VASCULAR SYSTEM. left side, extending about one and a half inches to the right of the median line and three inches to the left. Its upper border is about on a line with the second costal cartilage, its lower border, or the upper border of the third rib. Its apex is between the fifth and sixth ribs, two and a half or three inches to the left of the median line, where it can be felt pulsating. 6. The adult heart weighs from ten to twelve ounces in the male, and from eight to ten ounces in the female. Although absolutely heavier in the male, relatively it is not. 7. The heart has four cavities: two auricles above and two ventricles below. The auricle of one side com- municates with the ventricle of the same side, but not with the opposite auricle. The ventricles, like the auricles, have no direct communication with each other (Fig. 32). 8. The cavities of the heart are called : right auricle and right ventricle, left auricle and left ventricle (e, e', g, g, Fig. 32). 9. The right auricle receives the venous blood from the heart itself, from the body and upper and lower extremities. By contracting, it throws its blood through the auriculo-ventricular opening of the right side into the right ventricle. 10. The right ventricle, receiving the blood from the right auricle, contracts and throws it through the pul- monary artery to the lungs, and forces it on to the left auricle (c, c, Fig. 32). 11. The left auricle, receiving the blood from the right ventricle by way of the four pulmonary veins from the lungs, contracts and throws it through the THE HEART. Fig. 31. HEART. a, a, a, a, pericardium cut and turned back; b, ascending vena cava; V, de- scending vena cava; c, aorta and branches; d, pulmonary artery; 1, ductus ar- teriosus, a vessel of foetal life; e, left auricle; e', right auricle; e", right ventri- cle ; e'", left ventricle. 106 VASCULAR SYSTEM. auriculo-ventricular opening of the left side into the left ventricle {e, g, Fig. 32). 12. The left ventricle, being filled with blood from the left auricle, contracts and throws it into the aorta, through the arteries, capillaries, and veins, back to the right auricle, the point of starting {e'", c, e', Fig. 31). 13. The passage of the blood from the right ventricle through the pulmonary artery, lungs, and pulmonary veins to the left auricle is called the lesser or pulmonary circulation. 14. The passage of the blood from the left ventricle through the aorta and other branches, capillaries, and veins to the right auricle is called the greater or sys- temic circulation. 15. The passage of the blood from the auricles to the ventricles, and from the aorta through the coronary arteries back to the right auricle, constitutes the cardiac circulation. SECTION 11. VALVES OF THE HEART. 1. The openings from the ascending and descending venae cavse, which bring the venous blood to the right auricle, are not provided with valves, and during the contraction of the right auricle the blood regurgitates into these vessels. Those circular muscular fibres of the auricle which extend to some distance on these vessels constrict their lumen, or diminish their diameter, during the auricular contraction, and act to some extent as valves to diminish the return flow of blood into these vessels. The coronary sinus, which returns the blood VALVES OF THE HEART. 107 from the substance of the heart, is provided with a valve. 2. The opening leading from the right auricle to the nght ventricle—auriculo-ventricular opening of the right side—is provided with a valve having three curtains or folds; this is called the tricuspid valve (a Fig. 32), and opens toward the ventricle, closes toward the auricle; thus permitting the blood to flow from the auricle into the ventricle, but not from the ventricle hack to the auricle. During the powerful contraction of the ventricle this valve is shut toward the auricle with a clicking sound, and is prevented from being thrown too far by the chordse tendinese, little tendinous cords which are attached by one end to the inner surface of the ventricle, and by the other to the valves. They act as guys or stay-chains to prevent invagination of the valves. 3. The tricuspid valve having closed during the contraction of the right ventricle, the blood is forced past the sigmoid or semilunar valve (c, c, Fig. 32) of the right side into the pulmonary artery on its way to the lungs. The sigmoid valve of the right side, called also the semilunar and pulmonary valve, is composed of three curtains, which are attached to the inner sur- face of the pulmonary artery at its junction with the upper part of the right ventricle. During the passage of the blood from the ventricle into the pulmonary artery these valves or curtains are applied against the inner surface of the pulmonary artery. After the ventricle has ceased its action, gravity and the contrac- tion of the pulmonary artery cause part of the column of blood to start back toward the ventricle. This causes 108 VASCULAR SYSTEM. these valves to become closed toward the ventricle, and regurgitation becomes impossible. 4. The openings of the four pulmonary veins lead- ing from, the lungs into the left auricle are not provided with valves {d, d, opening in e, Fig. 32). The same arrangement of the circular muscular fibres of the auricle exists here as on the right side of the heart. 5. The opening from the left auricle into the left ventricle—auriculo-ventricular opening of the left side— is supplied with a valve having two instead of three curtains, as on the right side; this valve is sometimes called the bicuspid, and sometimes, on account of its fancied resemblance to a turban or mitre worn by bishops and cardinals, the mitral valve (h, Fig. 32). It is so arranged as to permit the blood to flow from the left auricle into the ventricle, and to prevent the flow from the ventricle to the auricle. It presents the same arrangement of tendinous cords as seen on the right side. 6. When the left ventricle contracts, the blood, being prevented by the mitral valve from returning to the auricle, is forced past the semilunar valves of the left side into the aorta, and thence through the arteries, capillaries, and veins to the right auricle. The semi- lunar or sigmoid valves of the left side are also called aortic valves, and bear the same relation to the aorta that the pulmonary valves bear to the pulmonary artery. 7. The student should now endeavor to trace the blood as it goes through the greater and lesser circula- tions, holding in mind the condition of the valves during the activity or repose of the various cavities of the heart. VALVES OF THE HEART. Fig. 32. HEART WITH ANTERIOR SURFACE CUT AWAY, SHOWING ITS CAVITIES, VALVES, ETC. b, b, walls of left ventricle; a, wall of right ventricle; a', tricuspid valve and chordae tendineae; mitral valve; c, c, curtains of pulmonic valves ;d, d, four pulmonary veins bringing blood from the lungs; e, cavity of left auricle; e', cav- ity of right auricle; g, g, corresponding cavities of ventricles. 110 VASCULAR SYSTEM. 8. Starting with the right auricle filled with venous blood, this may be done as follows: The right auricle contracts, and throws the blood through the auriculo- ventricular opening of the right side into the right ventricle. During this time there is regurgitation into the ascending and descending vense cavse, but not into the coronary vein or sinus. The right ventricle, having been filled with blood from the right auricle, contracts, closes the tricuspid valve toward the auricle, and forces open the pulmonary valves toward the pulmonary artery and lungs, throws the blood through the lungs, and by the pulmonary veins into the left auricle. When the right ventricle has ceased its action, the pulmonary valves become closed and prevent a return of blood into its cavity. The left auricle, being filled with blood from the four pulmonary veins, contracts, and throws its contents into the left ventricle through the auriculo- ventricular opening of the left side. The left ventricle next contracts, closes the mitral valve toward the auricle, and forces open the aortic valves in the aorta to throw its blood through the arteries, capillaries, and veins back to the right auricle by the ascending and descend- ing vense cavse. After the action of the left ventricle ceases the aortic valves are closed, like those of the pul- monary artery, to prevent a reflux of blood into the ventricle. 9. The heart is muscular in structure, and is held in position by the great vessels coming from its base. There are two rather distinct layers of muscular substance forming the walls of the heart—an internal circular, which is peculiar to and surrounds each cavity, and an external oblique layer, which is common to and sur- VALVES OF THE HEART. rounds all cavities. The external layer surrounding the ventricles, at first superficial, runs in an oblique manner from base to apex and from the right to the left side, becomes deep-seated, pierces the deep layer, and appears on the inner surface of the ventricles as little fleshy projections or columns, called columnss carnex. To these are attached some of the tendinous cords which hold the curtains of the valves in place. 10. The muscular walls of the various cavities of the heart differ in thickness according to the amount of work they have to perform. 11. The thickness of the walls of the left auricle is about a line and a half; of the right auricle, about one line ; of the right ventricle, about two and a half lines; of the left ventricle, about seven lines. The left ven- tricle has a greater distance to throw the blood than the right ventricle, hence the greater thickness of its walls. 12. The heart is surrounded by a very delicate sac of fibrous connective tissue called the pericardium, whose function is to secrete a liquid so that the motions of the heart can take place without friction. 13. The number of pulsations in adult life is not far from 70 per minute, though the number may vary within the limits of health. The pulse of Napoleon I. is said to have beat but 40 times per minute. Dunglison records a case even lower than this, where the pulsations were only 36 per minute. The pulse of Sir William Congreve is recorded as never being less than 128 per minute. 14. The heart beats more rapidly in the extremes of life than in the prime of life, being very rapid at birth, when it pulsates 136 times per minute. From this time 112 VASCULAR SYSTEM. it gradually diminishes in frequency until the adult state is reached, after which it begins to increase in the later years of life. 15. The function of the heart is to pump blood, and circulation, like respiration, is a part of the great general process of nutrition; and the more perfect the respiratory apparatus, the more perfect must be the circulatory system. SECTION 111. ARTERIES. 1. Arteries is the name given to that part of the vascular system which carries blood from the heart to the capillaries. The name was given to them by Praxag- oras before they were known to contain blood and when they were supposed to contain air, the word signifying an air-bearing or air-containing tube or receptacle. It is now known that they carry blood, but they still retain their old name. 2. The arteries may be said to have their origin from the ventricles of the heart, where they begin as two main trunks—the pulmonary artery on the right side, and the aorta on the left side. They are supplied with valves only at their beginning (bc, d, Fig. 33 ; b, d, Fig. 34). 3. They are of a yellowish-white color, very elastic and strong. They divide repeatedly, becoming smaller and smaller as they approach the capillaries: this division is generally dichotomous; that is, each one divides into two branches, and each of these into two ARTERIES. oiore, and so on until they lose all of their coats but one, when they are known as capillaries. Fig. 33. 4. The arteries may be described as having four coats, or three coats and a lining membrane {a, Fig. 35). The lining1 membrane which is con- tinuous with that lining the cavities of the heart is known as the endo- thelial coat, and is com- posed of a single layer of flattened cells called endothelial cells. This layer is sometimes called the endangium, and not only lines the cavities of the heart and arteries, but, following out the di- visions of the arteries, it forms the only coat of the capillaries (c, Fig. 35), and is prolonged as the lining membrane of the veins back, to become continuous with the lin- ing of the right cavities of the heart. c> capillaries. The arrows show the direction of the blood-cur- rent. e, e, e, valves. 118 VASCULAR SYSTEM. SECTION Y. 1. The veins begin by radicles where the capillaries terminate; that is, a capillary grows into a vein by the addition of layers similar to those of the arteries (b, Fig_ 35; b", Fig. 33 ; Fig. 36; a, a, Fig. 37; c, Fig. 34). VEINS. 2. The veins are similar in structure to the arteries, though their coats are thinner and less elastic. In veins the adventitia is the thickest coat, and the first to appear when a capillary is changed into a vein. 3. The most striking peculiarity of veins is the presence of valves within their lumen to prevent a reflux of blood toward the capillaries. 4. These valves are situated at various intervals along the course of the veins, and are composed of the lining endothelium, the whole of the intima, and part of the media. They are very strong, and have their bases applied to the inner surface of the wall of the veins, their free edges meeting in the centre of the lumen (e, e, e, Fig. 35). 5. The valves do not occur in the very smallest veins. They generally exist in pairs, though three folds are often found in the human subject. In certain portions of the body—viz. the abdomen, lungs, and brain—the veins are not supplied with valves. 6. The action of the valves can be easily demonstrated in any of the superficial veins by preventing the onward flow of blood in the veins toward the heart, when they will swell up and present little elevations at the point of attachment of the valves: by pressing the finger along the course of the swollen vein it can be emptied VEINS. 119 toward the heart, but if the pressure be made in the opposite direction, they remain full, and the eleva- tions indicating the point of attachment of the valves become more pronounced. Fig. 36. 7. The veins, though thinner than the arteries, are stronger: they are less elastic and have less con- tractility: they progressive- ly increase in size until they form the two venae cavae, which empty the blood directly into the right auricle. 8. The capacity of the veins is from two and a half to four times the ca- pacity of the arteries (com- pare a, a with h of Fig. 37). In the brain the venous capacity is six times as great as the arterial. The flow of blood in the veins is more rapid than in the capillaries, and less rapid than in the arteries. 9. Generally speaking, arteries carry arterial or red blood, and veins carry blue or black or venous blood. There are some excep- tions, however, where arteries carry venous blood and a, a, a, a, superficial veins of upper ex- tremity uniting- to form a large vein; 1, a process of fascia running over the vein. 120 VASCULAR SYSTEM. where veins carry arterial blood. The pulmonary ar- tery, for example, carries the impure blood from the right ventricle to the lungs for purification, while the pul- monary veins carry the pure oxidized blood to the left auricle on its way to the . left ventricle to be sent to the system, i Fig. 37. 10. Any part of the blood completes the circuit of the system in about twenty-three seconds, and the whole mass of blood passes through the heart in about thirty-seven and a half seconds, assuming the heart to beat 72 pulsa- tions per minute, and the left ventricle to discharge all of its blood, which is from five to six ounces, and the quan- tity of blood in the body to be from one-tenth to one-eighth of the weight of the body (Flint). 11. The force exerted by the left ventricle, 51.5 pounds, is sufficient to throw the blood through the arteries, capillaries, and veins, and back to the right side of the heart; but gravity, muscular action, inspiration, and con- traction of the veins themselves, facili- tate the flow of blood through these vessels. a, a, a, veins; b, b, b, arteries; c, arm ; d, forearm. 12. Regular and deep inspirations increase the quan- tity of venous blood in the thoracic cavity, hastening the circulation in the liver, and diminishing the venous con- gestion in the head and upper extremities. INFLUENCE OF ALCOHOL. SECTION VI. INFLUENCE OF ALCOHOL ON THE VASCULAR SYSTEM. 1. Small doses of alcohol increase the frequency and force of the heart’s action, diminish its period of rest, and increase the pressure in the arteries. 2. This influence is independent of the nervous sys- tem, and is seemingly due to the direct action of the alcohol on the substance of the heart itself. 3. Toxic or poisonous doses of alcohol produce par- alysis of the heart and arrest its action by direct influ- ence on the heart-muscle. When alcohol is taken into the stomach it gains access to the blood, visits the heart, and if in too great quantity paralyzes this organ and produces death. 4. Authorities differ as to the manner in which al- cohol acts upon the heart, some contending that it pro- duces its effect through the nervous system, and others that it acts by direct contact with the heart-substance. In the reduction of temperature which follows, the in- gestion of large doses of alcohol, the vessels are dilated, and this dilated condition must be due to some effect produced by the alcohol on the vaso-motor nerves which supply the muscular coats of the arteries. The enlarged condition of the capillaries, which have no muscular tunic, is probably due to mechanical distension. 5. Alcohol circulating in the vascular system acts as an irritant to the heart as well as to the vessels, produ- cing inflammations and leading to atheromatous changes or fatty degeneration of the inner coats of the arteries, producing ulcers and diminishing their strength. 122 VASCULAR SYSTEM. 6. The blood of habitual users of alcohol, constantly passing through the heart surcharged with this irritant, not only produces irregular, and abnormally active con- tractions, forcing it to increased work without allowing it proper time for rest and appropriation of food, but it destroys its lining membrane by producing inflamma- tion and ulceration like that found in the arteries under similar conditions. When the action of alcohol is pro- longed, the muscular substance of the heart itself may be attacked and undergo a fatty degeneration, diminish- ing its ability to perform work. 7. After death the blood is generally found in the veins, being forced there by the post-mortem contraction of the arterial coats. The dense, strong, and thick structure of arteries causes them to remain open like tubes when cut across, while, with few exceptions, the veins collapse when empty. This is due to the thin walls of the veins as compared with the walls of ar- teries. The hepatic veins (veins of the liver) remain open when cut across, because their periphery is ad- herent to the liver substance. 8. History.—Hippocrates and the earliest anatomical writers knew nothing of the circulation of the blood, and they confounded the arteries with the veins. 9. Praxagoras was the first observer to notice the difference between the arteries and the veins, and lie gave the arteries the name they still bear, supposing them to contain air, and not blood. 10. This observer is supposed to have dissected the human body, and the open condition of the arteries after death probably led him to believe them to contain air. 11. Aristotle, the soldier, physician, and philosopher* INFLUENCE OF ALCOHOL. who founded the first Natural History Museum known to the world, lived after Praxagoras, and thought the lungs and heart communicated, and that air came from the lungs into the heart, and thence into the arteries. He knew the heart to be the source of arteries and veins. Historians give conflicting statements concern- ing his ideas of the arteries, some quoting his work as saying the aorta carries blood, while others contend that he believed this vessel to contain air. 12. Galen, who lived in the second century after Christ, first demonstrated that the arteries carried blood, and wrote a whole book to refute the idea that they carried air. He noticed that at all times, when an artery was wounded, blood gushed out. He afterward included a portion of one of these vessels between two ligatures, and demonstrated by opening it that it con- tained blood, and not air. He supposed the origin of the veins to be in the liver, showing himself not so far advanced in anatomy as Aristotle, who considered the heart the organ of sanguification. 13. Although the vessels were known to contain blood for many centuries, no approach to the knowledge of the circulation was made until 1553, when Michael Servetus described in a work on theology the passage of blood through the lungs. Cesalpinus first used the term “ circulation ” after the death of Servetus. 14. Fabricius, the teacher of Harvey, is supposed to be the first who observed the valves in veins; he is said to have described them in 1603, though he says that he saw them in 1574. Valves had been seen in the branches of the portal vein as early as 1545, though the}’’ were described by another name. 124 VASCULAR SYSTEM. 15. Harvey discovered the circulation and the action of the valves in 1616, and although he clearly demon- strated the direction of the blood-current in the arteries and veins, he did not see the connecting capillaries. Mal- pighi in 1661 was the first to see the capillary circulation, and completed the discovery of the circulation of the blood. 16. Hemorrhage.—Any flow of blood from the ar- teries, capillaries, or veins is denominated hemorrhage, whether there be rupture of the vessels or not. 17. The most frequent form of hemorrhage is prob- ably epistaxis, or ordinary nose-bleed. It is generally so simple as to be arrested by any of the many means so well known to almost every one. Occasionally, how- ever, it becomes so aggravated as to be dangerous to life, and then more active means must be employed for its arrest. The neck should be freed of all constricting articles of clothing,. that the blood in the superficial veins of the neck may not be retarded in its return to the right side of the heart; deep inspirations should be taken to deplete the veins of the head and neck; cold in any form may be applied to the nose, face, neck, and head; the patient should stand erect, and if, for example, the hemorrhage be from the left side of the nose, the left arm should be extended to full length above the head, while the fingers of the right hand compress the nose on the bleeding side. If the bleeding continue, it will be necessary to plug the anterior and posterior nares, and a physician must be called. 18. Accidents frequently occur in which vessels of large size are wounded, and the bleeding is so great that life may be endangered before the necessary surgical aid can be obtained. In emergencies of this kind the INFLUENCE OF ALCOHOL flow oi olood may be controlled by firm pressure on the injured vessel above and below the wound if it be an artery, for divided arteries bleed from both ends; below the wound if it be a vein. If pressure enough cannot be brought to bear by the fingers, the tourniquet may be applied (Figs. 3«S and 39). It is possi- ble to extemporize an efficient instrument of this kind by tying a knot in a handkerchief and applying it around the limb in such a manner that the knot lies directly over the course of the in- jured vessel; by tying the two ends of the handkerchief and running between it and the limb a stick, any amount of pressure may be ob- tained by twisting the handker- chief. In great emergencies a stone or other hard body of suitable size and shape may be included in the handkerchief in place of the knot. (See descriptions of Figs. 38 and 39.) Fig. 38. METHOD OF APPLYING TOURNIQUET. o, wound; 6,6, skin cut away, exposing the underlying mus- cles ; c, handkerchief applied around the limb; d, course of the vessel; e, stick used to tighten the grasp of the hand- kerchief; h, stone in the hand- kerchief to cause pressure on the artery; /, knee; g, leg; i, thigh. 19. When a vein is wounded, the blood is dark blue or black, and flows in a continuous stream. When an artery is wounded, the blood flows in an interrupted stream, and is bright red in color. 126 VASCULAR SYSTEM. Fig. 39. APPLICATION OF TOURNIQUET TO ARM. a, handkerchief; b, stick used to tighten it; a', stone in handkerchief over course of wounded vessel; a", integument covering the forearm; c, c', d, d’, muscles of arm ; e, artery; e', vein; /, wound; the red dotted line indicates the course of the artery. QUESTIONS. QUESTIONS. SECTION I. What is the vascular system ? What is its function ?(1). Have the lowest animals a special vascular system ? Where do they obtain their nutritive matter ?(2). What is the heart ? What is its shape in man?(3). In what cavity is it situated ? In what direction does its base look ? Its apex? Is it nearer the anterior or posterior part of the thoracic cavity? What is its relation to the lungs?(4), How far to the right of the median line does its base extend ? How far to the left ? What marks its upper border ? What is the position of its apex ? Can it be felt in this situation?(6). What is the weight of the adult male heart? Of the female heart?(6). How many cavities has the heart? Do the auricles communicate with each other ? Do the ventricles, in adult life, communicate with each other? Do the auricles communicate with the ventricles?(7). What are the names of the cavities of the heart?(B). From where does the right auricle receive blood ? Where does it throw the blood? through what and how?(9). From where does the right ventricle receive its blood? Where and through what does it send it?(10). From where does the left auricle receive its blood? Where, through what opening, and how does it send it?(11). From where does the left ventricle receive its blood ? Where, through what, and how does it send it?(12). What is meant by the lesser or pulmonary circu- lation ?(13). What is meant by the greater or systemic circulation ?(14). What is meant by the cardiac circulation ?(15). SECTION 11. Are the openings of the ascending and descending venae cavae into the right auricle provided with valves? What takes the place of valves here? Is the coronary vein or sinus provided with a valve?(1). Is the opening from the right auricle to the right ventricle provided with a valve? What is the name of this valve? How many curtains has it? In what direction does it open ? In what direction does it close? What is its condition during contraction of the ventricle? What are the chordae tendinese ? What is their function? To what are they attached ? (2). Where are the pulmonary valves? How many curtains have they? In what direction do they open? In what direction do they close ? What causes them to open ? What causes them to close ? What 128 VASCULAR SYSTEM. is the function of their valves ?(3). Are the openings of the pulmo- nary veins into the left auricle provided with valves ? What takes the place, to some extent, of valves here ?(4). Is the opening from the left auricle to the left ventricle provided with a valve ? How many curtains has it? Why is it called “mitral”? In what direction does it permit the blood to flow? Is it supplied with chordse tendinese ?(5). Where are the aortic valves ? In what direction do they permit the blood of the left ventricle to flow ?(6). Commencing with the blood in the right auricle, describe the lesser and greater circulations, mentioning the direction of the blood-current and condition of the valves during the various stages of activity and repose of the heart(B). What is the structure of the heart ? How is it held in position ? How many layers of muscular tissue has it ? What are they called ? What is the relation of each to the cavities of the heart ? Where are the columnse carnese ? What are they ? What is attached to them ?(9). Why do the walls of the cavities of the heart differ in thickness?(lo). What is the peri- cardium? Of what is it composed ? What is its function ?(12). What is the thickness of the walls of the right auricle? left auricle? right ventricle ? left ventricle ? Why are the walls of the left ventricle thicker than those of the right ?(11). What is the number of pulsations of the heart per minute in adult life? Does the number vary within the limits of health ? What was the pulse of Napoleon I. ? Of Sir W. Congreve?(l3). Does the heart beat more rapidly in adult life than in the extremes of age?(l4). What is the function of the heart? What is circulation? How is it related to respiration?(ls). SECTION 111. What are arteries? What does the word mean?(l). Where and how do the arteries begin? Have they valves?(2). Are the arteries elastic? How do they divide? Do they become smaller as they divide?(3). How many coats have they ? Name them. Describe and trace the innermost coat(4). Describe the structure and give the func- tion of the intima(s). Give the function of the elastic tissue in the aorta. What is meant by the dicrotic pulse ? How is it produced ?(6). Describe the structure of the media. In what size vessels is it best developed? Which is the thickest coat of arteries?(7). What is the position of the adventitia? Is it well developed in arteries? What is the function of the adventitia?(B). Describe the divisions and loss of the coats of arteries until they become capillaries(9). QUESTIONS. What are the capillaries? What two sets of vessels do they connect? Of how many layers are they composed ?(1). In wliat vessels does the blood come in closest proximity to the tissues ? When does it lose its oxygen and gain C02 ? Where does it part with its nutritive matter ? Where does it gain its effete matter ? How is effete matter produced in the human economy ?(2). Do the capillaries become smaller as they divide ? What regulates the flow of blood in them ? What is their capacity? Are they all ever full at the same time?(3). Are they of uniform diameter? What is their diameter in nervous tissue? in bone? What is their length ? SECTION IV. How do the veins begin? How do they increase in thickness?(l). What is the structure of the veins? What is their thickest coat?(2). What is peculiar about veins? What is the function of the valves?(3). Where are they situated? What is their structure? In what direction do they permit the blood to flow?(4). Are they present in the smallest veins? How do they exist, singly or in pairs? Are there any veins of the body not provided with valves? Name some of them(s). Describe a process by which the action of the valves in a vein can be demon- Are the veins as strong as the arteries? Do they increase or diminish in size as they approach the heart ? Where do they finally throw their blood? By what vessels?(7). What is the cap of the venous system? What is the condition of the blood-current in the veins ?(8). Do arteries ever carry impure blood ? Do veins ever carry pure blood? Give examples(9). In what time does any part of the blood complete the circuit of the system ? How long does it take all the blood of the body to pass through the heart ?(10). What is the force exerted by the left ventricle? Is it sufficient to throw the blood to the right side of the heart ? What other factors facilitate circulation in the veins ?(11). SECTION V. What is the effect of small doses of alcohol upon the heart ?(1). To what is this influence due?(2). What is the effect of large and poison- ous doses of alcohol upon the heart ?(3). In what way does alcohol act upon the heart? What causes the vessels to dilate ? What produces the enlarged condition of the capillaries ?(4). What is the action of alcohol SECTION VI. 130 VASCULAR SYSTEM. circulating in the blood on the lining membrane of the arteries?(s). What changes does the blood of drunkards produce in their hearts ?(6). In what vessels is the blood generally found after death ? Why ? What is the difference in the walls of arteries and veins ? When veins are cut across, will they collapse? Will arteries? Why not? What is peculiar about the veins of the liver—hepatic veins ?(7). Did the earliest medi- cal men know anything of the circulation ?(8). Who gave the arteries the name they still bear? What did he suppose them to contain?(9). Did Praxagoras dissect the human body ? What probably led him to believe the arteries to contain air?(10). What was Aristotle’s view of the circulatory apparatus?(ll). Who was Galen? When did he live? Did he suppose the arteries to contain air ? How did he demonstrate that they contained blood ? Where did he suppose the veins to origi- nate ?(12). Who first described the passage of blood through the lungs ? When? Who first used the term “circulation”?(l3). Who first saw the valves in veins? When did Fabricius describe them? When does he claim to have first seen them? Had they been seen prior to this? (14). Who discovered the circulation ? »When ? Who saw first the capillary circulation ? When?(ls). What is hemorrhage ?(16). What is the most frequent form of hemorrhage? How may it be arrested ? (17). When vessels are divided and the hemorrhage is alarming, how may it be arrested? If pressure is not effective, what can be done? On what side of the wound must the pressure be brought to bear if an artery is wounded? if a vein is wounded? Describe the application of a tourniquet(lS). When a vein,-is wounded, what is the color of the blood? How does it flow? When an artery is divided, what is the color of the blood? How does it flow?(19). CHAPTER VI. RESPIRATION. SECTION I. 1. Respiration is the absorption, appropriation, and destruction of oxygen, and the production and elimina- tion of carbonic acid gas (CO2) by the tissues. 2. The passage of air into and out of the lungs is not respiration, and the lungs are not the true organs of respiration, only in so far as they form a part of the general structure of the body. 3. Respiration goes hand in hand with circulation, and, like it, is a part of the general process of nutrition; and as animals cannot regenerate their tissues without blood, so it is impossible for tissues to perform their function without oxygen. The more active the animal and the more rapid the circulation, the more perfect must be the oxidation of the blood. 4. When the tissues of the body perform work, they consume mitritive materials from the blood, and use oxygen gas; produce various effete matters and carbonic acid gas. This is absorbed by the blood, and goes by the veins to the right side of the heart, where it is sent to the lungs; here it loses the carbonic acid gas and gains oxygen, red blood being produced from dark-blue blood by the gain of one gas and the loss of the other. 131 132 RESPIRATION. 5. This change of venous blood into arterial blood has been called by some “ respirationthis may be true to some extent, so far as the blood itself, as a tissue, is. concerned; but evidently the gain of oxygen in the lungs by the blood cannot be respiration, for the vital gas is only now in a condition to visit, with the blood, the tissues; and whenever the tissues consume the oxygen and produce carbonic acid gas, respiration may be said to have taken place. 6. The exact changes which the oxygen undergoes in the tissues before the production of carbonic acid gas is unknown: physiologists and physiological chemists have never been able to trace oxygen in the tissues to the point of its destruction, or to define exactly the changes which take place in its consumption and the production of carbonic acid gas. 7. All animals, from the lowest to the highest, need some oxygen to enable them to perform their nutritive acts. Some need more than others, but in all the tissues demand this gas; and all that is definitely known is, that oxygen is consumed during tissue-work and car- bonic acid gas is produced. When animals are deprived of oxygen they die; and death comes more quickly to those in which nutrition is active than to those which are sluggish and slow in their nature. The demand by the tissues for oxygen is more imperative than for food or drink. 8. The great object of the lesser circulation is oxida- tion of the blood: in the lungs the poisonous matter is exhaled, and the oxygen is taken in mainly by the color- ing matter of the red blood-cells. After the blood reaches the left side of the heart, it is sent through the LUNGS. 133 arteries to the capillaries; in the arteries the blood is uniform in its composition; in the region of the capil- laries it loses nutritive material and oxygen, and is changed into non-nutritious blood, which goes into the veins and back to the right side of the heart, to be sent to the lungs for purification. In the veins the blood is not of uniform composition, because as the different tissues vary in their action, so there must be a variety of excrementitious matters produced, and the blood re- turning, for example, from the brain, will not be of the same composition as that returning from the muscular system. In the lungs these differences are all corrected, and the mixed venous blood is changed into the uniform arterial blood. SECTION 11. LUNGS. 1. Lungs are simply organs of convenience, acting as the media through which the blood loses its carbonic acid gas and gains oxygen. They are membranous or saccular stations developed in the course of the blood- current, by which the blood in its passage through them is exposed to the air which they contain ; where the car- bonic acid gas and other effete matter is thrown out and where oxygen is taken in (Fig. 40). 2. The simplest animals have no lungs. In them one kind of tissue performs all the work, absorbing oxygen and discharging carbonic acid gas. Higher in the scale of animal life the whole exterior of the body absorbs oxygen. In many sea-worms little tufts or 134 RESPIRATION. fringe-like prolongations extend from the sides. They are delicate membranes covering vessels, and absorb the Fig. 40. DIAGRAM OF THE HEART AND LUNGS. 1, 2, 3, lobes of right lung; 4,5, lobes of the left lung; a, a, a, a, a, a, pleura turned back ; b, pericardium ; c, trachea ; d, heart. The red vessel coming from it rep- resents the aorta, the large blue one over the right, the pulmonary artery; the small blue one, the descending vena cava. oxygen which is in solution in the water. The gills of fishes are only masses of blood-vessels covered by a delicate membrane, and as the water bathes them the LUNGS. 135 oxygen which is in solution goes in and the carbonic acid gas comes out. The frog breathes by gills in the tadpole state, but when full grown it has lungs, and also breathes by the skin to some extent. Reptiles have well-developed lungs, which, like all respiratory organs for the introduction of oxygen into the blood-current and the elimination from it of carbonic acid gas, are thin membranous structures containing air and sur- rounded by delicate capillary blood-vessels. The lungs of birds, mammals, and hence of man, are all constructed on the same type, the necessary conditions being air on one side and liquid on the other side of a permeable mem- brane. Lungs are simply membranes supporting blood- vessels, and folded or doubled into sacs to occupy less room and at the same time to present a great surface. 3. The smaller the folds or sacs of lungs the greater the surface presented, and the larger the sacs of course the less surface. The lungs of amphibians and reptiles are coarse in structure; that is, the air-sacs are large. The lungs of birds and of man are fine in structure; that is, they are composed of great numbers of small sacs, and hence present a great surface separating the blood from the air. 4. The ventral or belly cavity of man is divided into two parts by a muscular horizontal partition; the name of this muscular partition is the diaphragm. The division below the diaphragm is called the abdominal cavity, and it contains the stomach, small and large intestines, liver, spleen, pancreas, and kidneys. The upper division is called the thoracic cavity, and contains the heart, with the great vessels coming from its base, and the lungs (Fig. 41). 136 RESPIRATION. Fig. 41. DESIGNED TO SHOW THE DELATION OF THE ORGANS IN THE THORACIC AND ABDOMINAL CAVITIES. 1,1,1,1, large intestine; a, bladder; c, stomach ; 2, 2, 2, 2, 2, lobes of the lungs; 3, 3, 3, pleura cut away ; 5, 5, 5, muscles showing ends of cut-off ribs ; 4, trachea; 7, spleen; 6, 6, liver, with the gall bladder; 9, 9, 9, diaphragm; 10, heart. LUNGS. 137 5. The thoracic cavity is bounded behind by the dorsal vertebrae; laterally, by the ribs; in front, by the sternum and cartilages, which attach this bone to the anterior ends of the ribs; below, by the diaphragm, and above, by the root of the neck. 6. It is wider from side to side than from before backward, and is longer posteriorly than anteriorly. It is much larger in all dimensions at its base below than at its apex above. 7. The diaphragm is dome-shaped, with its convex surface up toward the thoracic cavity, and its concavity down toward the abdominal cavity. It may be likened in shape to a palm-leaf fan, with its handle tacked to the backbone and the leaf pulled forward and fastened to the lower margins of the circumference of the thorax ; or to a parasol hoisted from the abdomen, the handle being pushed back against the anterior surface of the vertebrae and the margins made fast to the periphery of the thorax below. Its convexity is more marked during expiration. During inspiration it becomes more nearly flat. 8. Anterior to the opening which leads from the throat into the gullet or oesophagus is the opening into the larynx, which is the upper cartilaginous portion of the windpipe or trachea, which leads into the lungs (7, Fig. 42). 9. The larynx is the name of the cartilaginous box at the beginning of the trachea. It is rigid in its struc- ture, so that it will not collapse during the act of inspi- ration. In this box, stretched across its upper opening, are the four vocal cords—two superior, and two inferior ; the two inferior ones are alone concerned in phonation, 138 RESPIRA TION. and are called the true vocal cords. The two superior ones are called the false vocal cords'; they run from before backward, are close together in front, and are separated be- hind. Fig. 42. 10. The air enters be- tween the vocal cords, and this little slit-like opening is called the rima glottidis. Muscles are attached to carti- lages of the larynx in such a manner as to enable the cords to ap- proximate each other behind or to diverge, thus opening and mak- ing passive the aperture between them. 11. During inspira- tion the slit is opened, and air rushes into the trachea and its divis- ions, the bronchi. Dur- ing expiration they fall nearly together, leaving only a narrow opening. 12. The entrance to the glottis is closed dur- ing the act of deglutition by a little triangular leaf-like body called the epiglottis (1, Fig. 42). During the acts 1,, epiglottis; 2,2,2, 2,2, rings of the trachea; 4, 4, 4. posterior surface of the trachea, unoc- cupied by cartilage ; 3,3, hyoid bone; 7, open- ing into the larynx. LUNGS. 139 of breathing the epiglottis stands up and rests against the posterior surface of the tongue. It prevents the entrance of liquids and particles of solid food into the trachea. 13. Below the larynx is the trachea or windpipe, a tube about or 5 inches in length and -| of an inch in diameter, flattened on its posterior surface (4, 4, 4, Fig. 42). It is composed of connective tissue and some mus- cular substance, enclosing from sixteen to twenty carti- laginous bands or rings, which extend only around the anterior two-thirds of the tube, the posterior third con- taining no cartilage, but made up entirely of connective tissue and muscular fibres. The trachea and all its divisions are lined by mucous membranes and covered with epithelial cells. The mucous membrane contains many mucous glands, which moisten the inner surface of the tube; and the epithelial cells have little hair-like processes on their extremities called cilia, which are constantly moving from, within out, and tend to clear the tube of any excess of secretion. 14. The trachea divides into two branches called primary bronchi, one for each lung. The right bronchus is shorter, wider, and more horizontal in its direction than the left. The bronchi present nearly the same anatomy as the trachea; they enter the lungs, divide and subdivide, becoming smaller and smaller, until they open into a collection of air-cells called a pulmonary lobule, when they measure one one-hundred and twenty- fifth to one one-hundredth of an inch in diameter (Fig- -43, b, b, b, and c, Fig. 44). 15. After entering the lungs the character of the cartilages in the bronchi changes. They become plates, 140 RESPIRATION. and completely surround the tubes. In very small tubes the cartilages are lost entirely. Fig. 43. a, a, a, pulmonary lobules ; c, c, bronchi; d, trachea ; e, intercostal muscles ;/, ribs cut across ; 1,1, 1, 1,1, divisions of the bronchi ;g, vertebral column; h, aorta ; k, oesophagus ; 3, 3, thyroid gland. The arteries and veins are also seen ramifying and dividing. 16. The lungs till all the space in the thoracic cavity not occupied by the heart and large vessels coming LUNGS. 141 from it. They are suspended freely, and are not attached to the bony ■ wall in any part of its course (Fig. 41).. 17. When distended the lungs are roughly pyra- midal in shape, with their concave bases down and their rounded apices up; they are covered by a delicate mem- brane called the pleura, which secretes a liquid, that the motions produced by the respiratory acts may take place without friction. Inflammation of this membrane pro- duces pleurisy (a, a, Fig. 40; 3, 3, Fig. 41; 2, 2, Fig. 43). 18. The lungs are two in number—right and left. The right lung has three lobes, and the left lung two (Fig. 40). Each of these lobes is made of lobules which are about to of an inch in diameter, and the lobules are made up of collections of air-cells or vesicles which vary in size with age and in different parts of the lung. They are smaller early than late in life, and are larger nearer the surface than in the deeper parts. Their diameters vary from 1° tV °f an inch. They are a little deeper than broad, and the anatomy of one of these air-cells is the anatomy of all the cellular part of the lung (a, a, a, a and d, d, d, d, Fig. 44). 19. The walls of the air-cells are richly supplied with yellow elastic tissue, which, when we come to study the respiratory acts, we will learn performs a very im- portant function in expiration. The fibres of this tissue cross the air-cells in such a way that when one fibre contracts it acts upon more than one air-cell. .20. Interwoven with the yellow elastic tissue is a rich plexus of blood-vessels put very closely together. These are the capillaries of the lungs, provided with one thin coat. 142 RESPIRATION. 21. The air-cells are lined with thin flattened cells of epithelium which touch the capillary blood-vessels. The air-cells contain the air from the divisions of the bronchi; they are lined with epithelium and sur- rounded with capillary blood-vessels. The air in the Fig. 44. TO REPRESENT THE TERMINATION OF A SMALL BRONCHIAL TUBE AND THREE COLLECTIONS OF AIR-CELLS. a, a, a, air-cells ; d, d, d, d, same cut in two : c, small air-tube ; b, b, b, divisions of the same, with two represented as being split. air-cells is separated from the blood in the capillaries on their walls by only two very thin layers of cells, the one forming the lining of the air-cell, the other consti- tuting the wall of the capillary blood-vessel. Here we have again all that is necessary for respiration—air on LUNGS. 143 one side and blood on the other side of a permeable membrane. 22. The cells are united to form collections and lobules. The lobules are held together by connective tissue to form lobes, and the lobes—three for the right and two for the left—are held together to constitute the lungs. The weight of the lungs is forty-two ounces, the right weighing two ounces more than the left, which weighs twenty ounces. 23. The exact area presented by the air-cells of the lungs is not known, but when it is remembered that the air-cells are microscopic in their size, it will appear that the total area is very great. Different writers have given various estimates, ranging from 150 to 1500 square feet. The air-cells of the lungs of a toad can be seen with the unaided eye, but the air-cells of the lungs of man require the powers of the microscope for their examination. SECTION 111. 1. Air enters the lungs through the mouth, nose, larynx, trachea, bronchi, and their subdivisions in con- sequence of enlargement of the thoracic cavity. 2. This enlargement is made possible by the peculiar method of attachment of the ribs to the vertebral column and .sternum, and by the action of muscles. 8. The ribs are attached to the dorsal vertebrae by a movable articulation ; and their general direction is from behind downward, forward, and inward. The first rib is nearly horizontal in direction; that is, its anterior end 144 RESPIRATION. is nearly or quite on a level with its posterior end, while in the ribs below the anterior extremity is on a plane lower than the posterior. This condition is most dis- tinctly marked at the ninth rib. The ribs are also slightly twisted upon themselves. The seventh is the longest, and the first is the shortest rib. 4. The ribs are classified as long flat bones, and are so placed that their surfaces look in and out and their borders up and down. The borders are marked by ridges which serve to protect vessels and give attach- ment to muscles. 5, Between the ribs are spaces, extending from the sternum in front to the vertebral column behind. These are called intercostal spaces and vary in length and breadth in different regions. They are wider in front than behind (e, Fig. 43). 6. To the borders of the ribs the external and in- ternal intercostal muscles are attached (e, Fig. 43). Muscles are also attached to the posterior part of the ribs which come from the transverse processes of the dorsal vertebrae (levatores costarum). The first rib has two muscles, which come from the transverse processes of all the cervical vertebrae except the first and second {scalenus anticus and scalenus medius). The second rib also has a muscle attached to its outer surface, which comes from the transverse processes of the fifth, sixth, and seventh cervical vertebrae {scalenus posticus), and to the whole of the circumference of the base of the thoracic cavity the diaphragm is attached. 7. During ordinary inspiration the diaphragm de- scends, and the ribs are raised by the action of the above muscles (the sternal portion of the internal inter- LUNGS. 145 costals being the only part of these muscles which act in inspiration). This enlarges the thoracic cavity in all directions, increasing its vertical, transverse, and antero- posterior diameters. The lungs follow the movements of the thoracic walls, the air rushes in to prevent a vacuum, and the air-cells become distended. This act (inspiration) is active in man. 8. In extraordinary acts of inspiration, as during an attack of asthma, other powerful muscles which are attached to the vertebral column, scapula, sternum, ribs, and humerus are brought into play to assist in elevating the ribs. 9. During expiration the diaphragm becomes relaxed and ascends, while the ribs descend. This diminishes all the diameters of the thoracic cavity, and the lungs not only become compressed, but by virtue of the yellow elastic tissue in their walls the air-cells contract and aid in expelling the air. In man expiration is a passive act. 10. During ordinary expiration a few poorly-devel- oped muscles act. These are portions of the internal intercostals, infracostales, and triangularis sterni. 11. During prolonged or forced expiration the flat muscles of the abdomen (internal and external oblique and transversalis) contract with power, assisting in drawing down the ribs and pushing up the diaphragm. This action is well shown in blowing a wind instrument. 12. The lungs are of a light pink color in early life, but become darker, and are of an ash-gray or slate color in advanced life; they are also mottled with black, which is due to the deposition of carbon in their sub- stance. This black condition is found in the lungs of 146 RESPIRATION. those who spend a great part of their time in an atmo- sphere of smoke and coal-dust, and hence are constantly inhaling particles of unburnt carbon, which become lodged in the lung-tissue. When this accumulation of coal-dust is so great as to interfere with the function of the lungs, a disease called anthracosis is produced. This kind of lung is especially marked in coal-miners. 13. To the touch the lungs are velvety and smooth, and when pressed upon there is a crepitation, or crack- ling sound, caused by the escape of air from some of the air-cells. They are also elastic, and when removed from the thoracic cavity will collapse. Healthy lungs will float in water, and if pushed under will rise again to the surface. This is of importance in certain medico- legal questions. 14. The important gases concerned in respiration are oxygen and carbonic acid gas. The oxygen -which gains access to the blood in the capillaries of the lungs comes from the atmospheric air which is in the air-cells, where it exists as a mechanical mixture, mainly with nitrogen. A small quantity of carbonic acid gas and some vapor of water are always present in the atmo- sphere. The oxygen and nitrogen exist in the ratio of 20.9 to 79.1 by volume. The amount of moisture is very variable. The quantity of carbon dioxide ranges from 0.0004 to 0.0006. It is greater in the atmosphere of crowded cities than in the open country {Loomis). 15. The oxygen is taken from the lungs by the red blood-corpuscles, the coloring matter of which ('hsema- globin) has a great affinity for this gas, and is carried to the tissues for respiration. The oxygen unites with the hsemaglobin to form oxyhasmaglobin. LUNGS. 147 16. The tissues have a greater affinity for the oxygen than the coloring matter of the red blood-cells, and have the power to take this gas from the red blood-cells and use it in the processes of nutrition. When the tissues consume oxygen, they produce some carbonic acid gas. This is mainly taken up by the plasma or liquid portion of the blood, though some of it is taken up by the red cells. 17. The blood carries the carbon dioxide to the capillaries of the lungs, where it goes through the deli- cate walls of these vessels and mixes with the air in the air-cells, while the oxygen of the air goes into the capil- laries to unite with the hsemaglobin of the red blood- cells. 18. The carbon dioxide exists in the blood in simple solution in the plasma, and also to some extent in com- bination with bases to form salts—carbonates and bicar- bonates ; that which is in solution simply diffuses from the blood into the air, while the salts are probably destroyed by some other acid uniting with the base and liberating the carbon dioxide. A small quantity of free acid probably always exists in the lungs (pneumic acid), which is destroyed in breaking up salts to liberate C02 (carbon dioxide). That carbonic acid gas which is taken up by the red blood-cells is probably liberated by the oxyhsemaglobin, which acts as an acid. 19. Carbon dioxide is not poisonous in the presence of sufficient oxygen, and those gases which are so dan- gerous to life are such as have so strong an affinity for the red blood-cells that even in the presence of oxygen they retain their position. Among these, the most im- portant is carbon monoxide. Carbon monoxide cannot 148 RESPIRATION. be used by the tissues, and as it prevents oxygen from entering into the red blood-cells, asphyxia is produced, which soon ends in death. 20. The stifling atmosphere of a poorly-ventilated and crowded room is not due so much to the presence of carbon dioxide as to the absence of oxygen and the presence of various organic emanations. 21. The quantity of air consumed in twrenty-four hours is between three and four hundred cubic feet. The volume of oxygen consumed is not far from of the volume of air inspired. In hospitals and places of public gatherings at least six to eight hundred cubic feet should be allowed for each person, and as much more as possible,' unless facilities are convenient for the frequent change of the air. 22. A certain quantity of oxygen consumed is not represented by the carbon dioxide exhaled. It prob- ably unites with hydrogen to form water in the body. 23. Age, sex, exercise, digestion, and sleep all modify the quantity of oxygen consumed and the amount of carbon dioxide exhaled. SECTION IV. 1. The quantity of air which remains in the lungs after a forced expiration is called the residual air, and is about 100 cubic inches. 2. The quantity of air which remains in the lungs after an ordinary expiration is 200 cubic inches, 100 cubic inches of which can be expelled by a forced ex- piration; this 100 cubic inches is the reserve air. LUNGS. 149 3. The air which goes in and out with each re- spiratory act is called the tidal or breathing air. It is simply sufficient in quantity to fill the trachea and larger divisions of the bronchi, and is estimated at about 20 cubic inches. 4. The air which can be taken into the lungs and air-passages after an ordinary inspiration by a forced inspiratory act is called the complemental air, and is 110 cubic inches. 5. The quantity of air which can be expelled after a forced inspiration is 230 cubic inches, and represents the breathing capacity of the lungs. The extreme capacity of the lungs must include the residual air, which will make 330 cubic inches. 6. The number of respirations in health is from six- teen to twenty per minute. This number varies, how- ever, even within the limits of health. The number of respirations increases with the increased frequency of the heart-beat, there being generally four beats of the heart to one respiratory act. 7. The respirations are more frequent in early than in adult life. They also increase in frequency in old age. Early in life there is no difference in the fre- quency of the respirations in the sexes. In women they are less frequent than in men of the same age. 8. Physiologists describe different types of respiration, of which there are three—superior costal, inferior costal, and abdominal type. 9. The abdominal type predominates in young chil- dren, and if observed while breathing the abdomen will be seen to move with each respiratory act. This type, combined with the inferior costal, predominates in the 150 RESPIRATION. Fig. 45.—A, A, solidified lung as it occurs in pneumonia, above which at 1 is represented cavities due to abscesses; 2, 2, shows air-cells containing air. The ramifications of the bronchial tree and vessels are also shown. LUNGS. 151 male. In the female the superior costal type predomi- nates, and the upper part of the breast is seen to fall and rise with each respiratory act. This is probably caused by lacing, which confines and limits the action of the abdominal muscles and the play of the lower ribs. In the females of savage tribes,' who have never worn tight clothing, the abdominal type predominates. 10. The lungs act to some extent as excretory or- gans, eliminating, in addition to carbonic acid gas, a small quantity of the vapor of water, organic matter, and a trace of ammonia. 11. When'alcohol is taken into the system a portion of it is eliminated by the kidneys, skin, and lungs, the greater part being consumed in the tissues by oxidation. When large quantities have,.been ingested the kidneys are relatively active in elimination. When small quan- tities have been taken, the lungs are relatively more ac- tive in its elimination than when large doses have been ingested. The habitual use of alcohol produces con- gestion and inflammation of the lung-tissue, leading to pneumonia and consumption (Fig. 45). 12. In order to properly perform their function the air-cells should be supplied with a sufficient quantity of pure air, which can be accomplished by regular and deep breathing in a pure atmosphere. Deep inspirations not only more perfectly change the air in the deeper portions of the lungs, but distend the air-cells, favor the absorption of any exudation that might be in them, and increase the surface of blood-vessels exposed to the air. They also facilitate the circulation in the liver. 13. The walls of the thorax and abdomen should not be restricted in their natural movements by the appli- 152 RESPIRATION. Fig. 46.—Diagram designed to show the effects of tight lacing in early life, re- sulting in permanent deformity of the thoracic walls. Compare with Figs. 45 and 41, which are normal. QUESTIONS. 153 cation of tight articles of clothing. The lungs follow the movements of the diaphragm and thoracic walls, and when these are interfered with the lungs are unable to become distended, the air-cells are not properly in- flated, the air is not sufficiently changed in the deep portions of the lung, the blood cannot be properly oxi- dized and purified, and the nutrition of all the tissues must suffer (Fig. 46). 14. In order that the lungs may play with ease in the cavity of the thorax, the body should be kept erect and the shoulders thrown well back. This position facilitates the action of those muscles concerned in modifying the dimensions of the thoracic cavity, and enables the air to enter the respiratory passages at the best possible advantage. QUESTIONS. SECTION I. What is respiration ?(1). What are the lungs ?(2). What must tissues have in order to perform their function ?(3). What change takes place in the tissues when they work? Where does the blood lose its poison- ous gas, C02? and where does it gain oxygen ?(4, 5). Are the changes concerned in the formation of C02 in the tissues well known ?(6). Do all animals need oxygen? Do the tissues need it constantly?(7). De- scribe the change which takes place as the blood passes through the lungs. What change takes place as it passes through the tissues of the body ? Is the composition of the arterial blood the same in all divisions of the vascular system ? Is the venous blood the same in structure in all veins ?(8). SECTION 11. What kind of organs are the lungs? What is their function?(l). What takes the place of lungs in the simplest animals ? Describe the respiratory organs of some of the lower animals. What kind of struc- 154 RESPIRATION. ture is necessary in a breathing organ ?(2). What is the structure of the lungs of amphibians? of birds and mammals?(3). Into how many cavities is the belly cavity of man divided ? What muscle divides it ? What are the divisions called? What does each cavity contain?(4). Bound and describe the thoracic cavity(s, 6). What is the shape of the diaphragm during the respiratory acts?(7). Where is the opening into the larynx ?(8). What is the larynx ? What important structures does it contain ? Describe the vocal cords. Which are the true cords ? (9) What is the rima glottidis ? What enables the cords to move ? (10) What is the condition of the slit during the respiratory acts?(ll). What closes the entrance to the glottis ? What is its position during the acts of breathing? What does it do during the act of deglutition?(l2). Describe the trachea(l3). Describe the bronchi(l4, 15). Where are •the lungs situated ? Are they attached to bone ?(16). What is their shape when distended ? What covers them ? What is the function of the pleura? What is pleurisy?(l7). How many lungs are there? Describe their structure(lS). Describe the structure of an air-cell(19- 21). Describe the formation of a lung from the air-cells. What is the weight of the lungs ?(22). How much surface is presented by the air- cells of the lungs of man? Can the cells be seen with the unaided eye?(23). SECTION 111. What causes the air to enter the lungs? What causes this enlarge- 2). Describe the attachment and direction of the ribs(3). How are the ribs classified ? How do their borders and surfaces look? (4). Describe the intercostal spaces(s). Describe some of the muscular attachments to the ribs(6). Describe the changes of the thoracic cavity during ordinary inspiration, and the action of some of the muscles con- cerned. Do any additional muscles act during extraordinary inspi- ration ?{7, 8). Describe the changes of the thoracic cavity during ex- piration. What is the condition of the air-cells at this time?(9). What muscles act during ordinary expiration ? What muscles act during forced and prolonged expiration ?(10, 11). What is the color of the lungs in early life? in old age? Name some causes of discoloration of lung-tis- sue(l2). How does lung-tissue feel to the touch? What causes the peculiar sound when it is pressed upon ? Will healthy lung-tissue float in water?(l3). How does the oxygen exist in the air-cells? Give the relative quantities of nitrogen and oxygen in the atmospheric air. Does the air contain any C02?(14). How does the oxygen reach the 155 QUESTIONS. tissues ? What is the union of oxygen and the coloring matter of the blood called ?(15). Why does the oxygen leave the blood and go to the tissues ? What kind of gas do the tissues produce when they use oxygen ? How is this gas taken up by the blood ?(16). What does the blood do with the (CO2) carbon dioxide ? What gas then enters the blood ?(17). How does the carbon dioxide exist in the blood ? How is that which exists as bicarbonates, etc. liberated in the lungs ?(18). Under what conditions are gases poisonous and dangerous to life ?(19). What causes the poisonous gases of poorly-ventilated apartments ?(20). How much air is* consumed in twenty-four hours ? How much oxygen ? How many cubic feet should be allowed for each person in crowded pub- lic buildings ?(21). Is all the oxygen consumed represented by the C02 exhaled ? What becomes of the lost oxygen ?(22). Name some things that modify the quantity of oxygen consumed(23). SECTION IV. What is the residual air? How much is it?(1). What is the reserve air? its quantity ?(2). What is the tidal air? its quantity?(3). What is the complernental air? its quantity?(4). What is the breathing capacity of the lungs? What is the extreme capacity of the lungs?(s). How many respirations per minute in health ? How many beats of the heart to one respiratory act?(6). How do the respiratory*acts vary in frequency at the different ages of life? Are they more frequent in the male or female ?(7). How many types of respiration are there ? Name them(B). Describe these types. What probably causes the superior costal type in females ? What is the type of breathing in the females of savage tribes ?(9). Name some substances thrown off by the lungs. (lO). What becomes of alcohol when taken into the system ? What dangerous changes are induced in the lungs by its excessive use ?(11). How can the air-cells be furnished with pure air? Name some advan- tages of deep inspiration(l2). Describe the effects of tight lacing on the shape of the thoracic cavity, and its dangerous effects on respiration (13). What should be the position of the body in order that the respi- ratory acts may take place to the best advantage ?(14). CHAPTER VII. MUSCLES. SECTION I. 1, Muscles may be defined as the active organs of locomotion, the bones, especially those of the extremi- ties, being the passive organs of locomotion. 2. Animals are enabled to move from place to place in quest of food and to perform work by the action of the muscles upon their bones. But animals very low in the scale of life also have the power of motion, though they have no muscles at all. In these, how- ever, the motion is due to the contraction of the proto- plasm of which they are composed, the simplest forms sending out portions of the body which act temporarily as feet. Those forms a little higher in the scale have parts of their structure modified into little hair-like processes on their surface called cilia, which move all in one direction, and faster in one direction than in another, thus enabling the animal to move through the water, or, when its body remains at rest, creating cur- rents in the water which may bring it food. 3. It is only in the higher divisions of the animal kingdom that distinct muscular tissue makes its ap- pearance. In the lowest forms of life all parts, or any 156 MUSCLES. 157 part, of the body perform any or all functions necessary to the existence of that form of life; but in higher ani- mals certain parts perform certain functions or do cer- tain work for all other parts, whereby they are exempted from doing many other things that are necessary for the existence and life of the animal to which they belong. 4. In the simplest animals any part of the body can feel, move, secrete, excrete—in a wmrd, do anything that is necessary to be done—but in the highest animals cer- tain parts are concerned with sensation alone {nerves), and have nothing to do with motion (except to stimu- late the muscles); other parts are concerned with motion {muscles), and do no part of the work of nerves; and still other parts are for support and protection {bones), and have nothing in common, so far as function is con- cerned, with either nerves or muscles. Of course, in higher animal life the integrity of structure and func- tion of every part depends upon the presence and healthy action of all other parts; that is, bones could not assist in locomotion unless the muscles were nor- mally active, and muscles could not properly act unless the bones (or their equivalents) and the nerves were performing their duties properly. 5. All animals that have muscles are not supplied with bones, yet they have certain parts peculiarly de- veloped to receive the insertion of the muscles, and which, so far as locomotion is concerned, take the place of bones. This is the case in those invertebrates whose external parts are developed into hard crusts or shells, as the lobster, crab, bee, etc., the muscles being attached to the inner surface of the shell or crust, which is a 158 MUSCLES. modified skin, and which is called the exoskeleton. It serves for protection as well as for muscular attachment. 6. Contractility is one of the properties of muscular tissue, and when the fibres of a muscle undergo con- traction, the two ends approach the centre and they become thicker and shorter. This power to contract is one of the fundamental properties of protoplasm, like sensibility and the power to appropriate food for growth and the ability to reproduce its kind in a new form. Just why protoplasm, or its special modification muscular tissue, contracts, no one has as yet explained. All that can be said in this direction is, that under cer- tain conditions muscular tissue will behave in this peculiar manner. It is just as wonderful that mus- cular tissue should contract as that nervous tissue should generate and transmit nervous force. 7. Contractility, then, is one of the so-called phe- nomena displayed by muscular tissue. This con- traction, or shortening and thickening, of muscular fibres can be induced in a variety of ways—by the application of mechanical or chemical stimuli, as acids, alkalies, cold, heat, or direct injury by a blow; by the passage of electricity through their substance or the nerves that supply them. The cause generally given for muscular contraction is the transmission through their nerves of some influence generated by the cellular matter of the brain. Still, muscular tissue will respond, for a time, by contraction to the application of a stimulus when entirely separated from the nervous system, show- ing that it has an irritability of its own. 8. This is shown in an admirable manner when the heart of an animal is suddenly extirpated: though re- MUSCLES. 159 moved from all connection with the central nervous system, yet the heart keeps up its contractions spon- taneously for a time—that is, without the application of a stimulus, unless the air be considered as such—and after these spontaneous actions' have ceased, contractions can be induced by simply pricking the surface of the organ with a pin. This can be done again and again, the heart at first responding by several contractions to each application of the stimulus, until finally each prick of the pin provokes but one contraction, and later no contraction at all. 9. After the external application of the stimulus fails to elicit a response, the heart may be made to con- tract by pricking or simply sticking its internal surface. This continues for a time, when the organ ceases alto- gether to respond to a stimulus applied either exter- nally or internally. If it now be allowed to rest for a time, and especially if -it be bathed in blood, it regains to some extent its powers of contraction; but a time comes when no treatment can induce a contraction in the dead muscle, and physiologists say it has lost its “ chemical and physical integritywhich means no more than that those changes which take place in its substance by which it is enabled to produce the phe- nomenon of motion no longer occur, and that it dies because it is not in a condition for these changes to take place. 160 MUSCLES. SECTION 11. 1. Muscles vary in color in different animals. Gen- erally they are white in cold-blooded animals, such as fishes, frogs, and reptiles, and red in warm-blooded ani- mals, as birds and mammals. There is an exception to this in the muscles of the breast of the partridge, pheasant, common fowl, etc., which are white. The muscles of the spider are yellow. The muscles in man are red, and this is true of all the animals of the class to which he belongs. SUBDIVISIONS OF THE MUSCLES. 2. Muscles are divided into smooth and striated mus- cles. Generally speaking, all the muscles of the insect tribe and the voluntary muscles of animals possessing a backbone are striated, while the involuntary muscles are non-striated or smooth. 3. Voluntary or striated muscles are those that are under the influence of the will; they are presided over by the cerebro-spinal nervous system, and can be called into action at any time. The greater number of the muscles of the body are of this variety, especially the muscles of locomotion. By an act of the will we can flex and extend the forearm, run, jump, or walk. Such actions are called voluntary, and are executed by volun- tary or striated muscles. 4. Involuntary, non-striated, or smooth muscles are those that are not under the influence of the will; they are stimulated to action and governed by the sym- pathetic nervous system, and it is impossible to influ- ence their action by any force of the will. Such mus- cles are found in the arteries and veins, iris of the eye, SUBDIVISIONS OF THE MUSCLES. 161 walls of the alimentary canal (oesophagus, stomach, small and large intestines). The iris is the muscular curtain suspended behind the cornea and in front of the most important refracting media of the eye. It presents in its centre the opening called the pupil (sometimes called the sight), which increases and di- minishes in size with the varying amount of light it receives. It contracts and becomes small when exposed to a bright light, and in the dark it dilates and becomes large. It governs the amount of light admitted to the eye. It is impossible by an act of the will to directly influence the movements of the iris. The iris also receives filaments from the third nerve {motor oculi). 5. The various parts of the alimentary canal move during digestion, and it is impossible, for example, to regulate the movements of the stomach, induced by the presence of food, by any direct act of the will. So the blood-vessels vary in their size in obedience to the de- mands of nutrition, yet no act of the will can modify their diameter. 6. The heart, though involuntary in its action, re- sembles voluntary muscular tissue in that it is striated, though it differs from it in other points of structure— in possessing no sarcolemma, and in the inosculation and branching of its fibres and central position of the nuclei. 7. There are certain muscles in the human body which generally have an involuntary action—muscles of respiration—but which can be arrested for a certain time by an act of the will. Normally, when we breathe the diaphragm contracts and relaxes without attracting our attention, but if we desire we can by an act of the 162 MUSCLES. will cease to breathe for a time, and the diaphragm ceases its action. It is impossible, however, for us by any direct act of the will to cause the heart to cease its pulsations. Muscles like those of respiration may be called, so far as their action is concerned, mixed muscles. 8. There are certain muscles in the human body which may be called hollow muscles: they contain a cavity. Such are the heart, arteries, stomach, intes- tines, and bladder. There are other muscles which surround openings into the body, and which are some- times called hollow muscles; they are more properly described as flat muscles arranged in a circular or oval manner. Examples of muscles of this kind are to be found surrounding the eyes (orbicularis palpebrarum), mouth {orbicularis oris), and the extremity of the large intestine called the rectum, which is closed by the exter- nal sphincter ani muscle (Fig. 47). 9. Hollow muscles have no attachment to bone, the heart, for example, being held in place by the large vessels coming from its base. The sphincter muscles that close the mouth and rectum have no bony attach- ment, while the muscle closing the eye has a bony origin (Fig. 47). 10. The greatest number of muscles are attached to bones, and are under the influence of the will. There are other muscles under the control of the will attached to the skin, but they are poorly developed. Among muscles of this kind may be mentioned the occipito- frontalis (which enables us to move the scalp and to raise the eyebrows); the three muscles of the ear, which belong to the same class, and can be moved by some people; the flat platysma-myoides, occupying the side of SUBDIVISIONS OF THE MUSCLES. 163 Fig. 47. 1,1,1, muscles of the ear; 2, 2, the bellies of the occipito-frontalis; 3, orbicu- laris palpebrarum ; 4, orbicularis oris; 5, sterno-cleido mastoid; 6, trapezius ; 7, 7, 7, fascia covering the temporal muscle. MUSCLES OF HEAD, NECK, FACE, AND EAR. 164 MUSCLES. the neck and blending with many of the facial mus- cles, which can be used by many persons in shaking or twitching the skin in this region. Nearly all of these muscles have some bony point of attachment; they are very poorly developed in the human subject, and are often spoken of by anatomists as rudimentary muscles (Fig. 47). SECTION 111. PHYSICAL CHARACTER OF THE MUSCLES. 1. The weight of the muscles is more than three and a half times the weight of the bones, and the bulk of the muscles is more than six times the bulk of the bones. The bones in the recent state of a person of medium weight weigh about twenty-two pounds. 2. Muscles are generally attached to bones through the medium of the periosteum and tendons or aponeuroses. 3. The periosteum is the name of the membrane which surrounds all bones except at their articular sur- faces. Tendons are bundles of fibrous connective tis- sue terminating a muscle. Aponeuroses are flattened tendons. 4. Muscles form the great bulk of the body, and in addition to assisting in locomotion they act as easy cushions or chairs protecting the bones from direct ex- ternal violence. 5. The voluntary as well as the involuntary muscles present a great variety in shape and in the arrangement of their fibres, as well as in their size and strength. 6. The smallest muscle in the human body is prob- ably in the middle ear (stapedius). It is said to be about MUSCLES. 165 one-sixth of an inch in length and to weigh not more than one grain. The longest mus- cle is probably the sartorius, which runs from the sharp point at the anterior part of the hip (