PHYSIOLOGY 
 
 AND 
 
 HYGIENE 
 
 CALIFORNIA 
 STATE SERIES 
 
GIFT OF 
 W. H* Ivle 
 
 EDUCATION UPT. 
 
CALIFORNIA STATE SERIES SCHOOL TEXT-BOOKS 
 
 PHYSIOLOGY AND HYGIENE 
 
 COMPILED BY THE 
 
 STATE TEXT-BOOK COMMITTEE 
 
 AND APPROVED BY THE 
 
 STATE BOARD OF EDUCATION 
 
 GJUT 
 
 1 ' 
 
 SACRAMENTO 
 W. W. SHANNON, SUPERINTENDENT STATE PRINTING 
 
3d 
 
 COPYRIGHT, 1906, BY 
 THE PEOPLE OF THE STATE OF CALIFORNIA 
 
 COPYRIGHT, 1902, BY 
 BUEL P. COLTON 
 
 In the compilation of this book certain matter from an Elementary 
 Physiology and Hygiene by Buel P. Colton has been used. All such 
 matter is protected by the copyright entries noted above. 
 
 - .,,. .. 
 
 -H 
 
 L'DUGAXiOW DEPT. 
 
PREFACE. 
 
 IN preparing this work for younger students especial 
 pains have been taken to niake it clear and simple. Sen- 
 tences, paragraphs, and chapters have been made short, 
 and a concise summary follows each chapter. So far as 
 possible technical terms have been avoided and English 
 words preferred to Latin, for instance, post-caval vein 
 instead of vena cava inferior, spinal bulb instead of medulla 
 oblongata, etc. The Latin form of the plural puzzles the 
 student who has not had Latin ; hence the English form 
 of the plural is used, as pleuras, ganglions, ciliums, ml- 
 /uses, papillas, etc. 
 
 The illustrations are made clear and distinct, and are 
 labeled directly ; that is, the detail labels are on, or very 
 close to, the part labeled, so that time and effort are 
 not needed to associate the thing and the name. A large 
 number of the illustrations are original. 
 
 A few simple experiments are given ; for although much 
 less can be done than with older students, yet considerable 
 must be done if the subject is to be made clear. 
 
 The subject of hygiene has received careful attention; 
 for it must not be forgotten that the main object of this 
 study is that each pupil may learn how to take better care 
 of his own body. It has been the aim not to give mere 
 arbitrary rules of health, to be blindly and implicitly fol- 
 lowed, but to base all precepts of hygiene on the general 
 principles of physiology, so that the pupil may understand 
 
 f/55976 
 
iv Preface. 
 
 the why and the how so far as possible. His obedience 
 will be more ready and more complete when based on 
 intelligence than when it is simply a submission to a 
 peremptory command. In many cases, too, the general 
 principle will serve as a guide where no rule has been laid 
 down ; no treatise can cover all possible contingencies. 
 
 At the end of the book is a glossary in which all tech- 
 nical terms are pronounced and explained. 
 
CONTENTS. 
 
 CHAPTER PAGE 
 
 I. Introduction I 
 
 II. The Bones 5 
 
 III. Muscles and Motion .16 
 
 IV. The Muscles and the Bones .28 
 
 V. The Nervous System Sensation and Motion ... 36 
 
 VI. Circulation of the Blood -47 
 
 VII. Control of Circulation . 67 
 
 VIII. The Blood and the Lymph 74 
 
 IX. External Respiration 83 
 
 X. Internal Respiration 97 
 
 XI. Ventilation and Heating ....... 106 
 
 XII. Dust and Bacteria 114 
 
 XIII. Excretion 123 
 
 XIV. Foods and Cooking 134 
 
 XV. The Digestive System Digestion in the Mouth . . . 146 
 
 XVI. Digestion in the Stomach 156 
 
 XVII. Digestion in the Intestine 164 
 
 XVIII. Absorption 172 
 
 XIX. Hygiene of Digestion Nutrition 181 
 
 XX. Exercise and Bathing 192 
 
 XXI. The Brain . .198 
 
 XXII. The Senses The Gerieral Senses Touch and Temperature 
 
 Sense 208 
 
 XXIII. The Sense of Sight . . . . . . .215 
 
 XXIV. Defects of Eyesight and Care of the Eyes . . . .223 
 XXV. Taste, Smell, Hearing, and the Voice 233 
 
 XXVI. Accidents What to do till the Doctor comes . . . 240 
 
 XXVII. Vaccination 250 
 
 XXVIII. Stimulants and Narcotics 253 
 
 GLOSSARY 261 
 
 INDEX . 273 
 
 v 
 
TO THE TEACHER. 
 
 IT is not the fault of the teacher that the human body is very com- 
 plex in structure and that many of the functions are obscure. Never- 
 theless the teacher is responsible for making the subject as clear as is 
 possible. To do this it is absolutely essential to perform some experi- 
 ments and to show some of the internal organs of such an animal as 
 the rabbit, or materials obtained from the butcher. This involves 
 work, and sometimes work that is not altogether pleasant. But no 
 earnest teacher will shrink from work simply because it is not agreeable. 
 
 Every school should have a microscope, by means of which to show 
 the corpuscles of the blood, cells from various tissues, the circulation 
 of blood in a frog's web, or in the gills of a tadpole. From various 
 dealers in school supplies there can be purchased mounted slides illus- 
 trating most of the kinds of cells and tissues of the body. These can 
 be successfully used by teachers who have not had the advantages of a 
 thorough training in histology. 
 
 When studying the bones the teacher can usually borrow some 
 human bones from the nearest physician. Also get a femur of a horse 
 or cow and saw it in two lengthwise. It will show the structure as 
 well as a human femur. It is easy to test the composition of bone by 
 burning and by acid. Corned beef shows well the structure of muscle. 
 A sheep shank from the butcher may be used to show the joints, 
 synovia, cartilage, ligaments, etc. Most pupils will be ready to help 
 dissect a heart and will be delighted to see the action of the valves. 
 
 By means of a common bulb syringe and a little glass and rubber 
 tubing the action of the arteries and the nature of the pulse and capil- 
 lary flow may be illustrated. The circulation of blood in the web of a 
 frog's foot is such an interesting and instructive sight that the teacher 
 should show it to the class without fail. Even if the school has no 
 microscope and the teacher without experience, it is often possible to 
 get a near-by physician to show it to the class. The coagulation of the 
 blood is readily shown. The experiments illustrating the action of the 
 
 vii 
 
viii To the Teacher. 
 
 diaphragm are very helpful, and any teacher possessing a modicum of 
 ingenuity and willingness to work can prepare them. In addition to 
 the experiments given in illustration of the chemistry of respiration, it 
 is desirable to show nitrogen and the composition of the air. This can 
 readily be accomplished by following the directions in the larger book 
 or in any chemistry. 
 
 To learn the temperature of the body borrow a clinical thermometer 
 from a physician. Have the children make little paper windmills to 
 show the air currents in rooms, over stoves, registers, radiators, etc. 
 The children should test the currents of air at all gratings and registers 
 in the schoolroom by holding a handkerchief up close to them. The 
 teacher should place a board under a window (as directed in this book) 
 to show how to ventilate a room without unpleasant drafts. Each 
 pupil should prepare a section of tooth as directed in this book. When 
 studying the subject of absorption, the teacher should get from the 
 butcher about a foot of the small intestine of a calf. He will wash it 
 clean for a small consideration. Cut this into pieces an inch long. 
 Turn them inside out and place them in shallow dishes of water. The 
 villuses will readily be seen. A piece of the gullet will show the mus- 
 cular and mucous coats. Have the pupils make a careful study of 
 Fig. 87 and also of Figs. 85 and 86, which are designed to lead up to 
 Fig. 87. If the teacher is willing to practice, he can soon learn to 
 demonstrate muscle'' action by means of frog's muscle and to show 
 reflex action of the spinal cord with a frog. 
 
 Many interesting experiments on the senses can be made with chil- 
 dren, such as the test of touch with compass points, keenness of sight, 
 hearing, accuracy of the muscular sense, etc. The internal structure 
 of the eye never fails to awake enthusiasm, and the teacher should 
 show this, and perhaps some of the pupils can also succeed in doing 
 the same. If the teacher can obtain a book on nursing, or, better still, 
 persuade a physician or trained nurse to come before the class, they 
 can learn how to prepare and apply bandages, to dress wounds, to treat 
 for drowning, etc. 
 
ELEMENTARY PHYSIOLOGY. 
 
 CHAPTER I. ; - *-';:*: 
 INTRODUCTION. 
 
 The Care of a Machine. In order to take good care of 
 a machine one must know about its different parts, what 
 each part is to do, and the relation of the parts to one 
 another. He must keep the machine clean and well oiled, 
 and must not overwork it. Otherwise it will neither do 
 good work nor last long. This is true not only of machines 
 like typewriters and sewing-machines, but of bicycles, and 
 even of such simple tools as knives and scissors. We 
 would not trust the management of any valuable machine 
 to one who did not know enough to take good care of it. 
 
 The Care of the Body. The care of the body is of vastly 
 greater importance. We can get new parts to replace 
 those worn out in a machine. While we can get artificial 
 limbs, we cannot replace such organs as an eye, the heart, 
 or the lungs. If we do not take good care of our bodies, 
 we cannot keep well, live long, or do good work. So we 
 need to know about the different parts of our bodies, the 
 work that each is to do, and the relation of the parts to 
 each other. 
 
 This knowledge is desirable for everybody ; but espe- 
 cially necessary for those who live a quiet, indoor life. In- 
 door people do not get as much exercise or as much fresh 
 
 i 
 
2 Physiology. 
 
 air as those who live outdoors. An indoor life is always 
 more or less artificial, and we need to take especial care 
 that our bodies do not suffer. It is believed that one 
 seventh of the deaths among civilized races are due to lung 
 troubles. Those who live outdoors have little trouble of 
 such kind. We need to learn about the air and breathing, 
 about exercise and bathing, about food and digestion, about 
 blood and its circulation, about the nervous system, etc. 
 
 Hygiene. ; Hygiene is the art of preserving the health. 
 This is the main object of our study of this subject. 
 
 Physiology. Physiology is the science of the action of 
 the body and its various parts. We must know the natural 
 action of the parts of the body to be able to keep them in 
 good working order. 
 
 Organ. An organ is any part of the body that has a 
 special work to do, as the hand, eye, or heart. 
 
 Function. The work or action of an organ is its 
 function. 
 
 Anatomy. Anatomy is the science of structure. We 
 need to know something of the structure of our bodies. 
 For this purpose we may study the internal structure of 
 the sheep, pig, calf, and rabbit which is very similar to 
 our own. We can take the hearts, lungs, brains, eyes, and 
 muscles of such animals to learn something of the struc- 
 ture of these organs in our own bodies ; if we fail to do this, 
 we can never get a clear understanding of the subject. 
 
 Tissues. Every organ is made up of several different 
 kinds of material. For instance, in a slice across a ham 
 we see skin on the outside, then fat meat, lean meat, and 
 bone. These " primary building materials " of the body 
 
Introduction. 3 
 
 are called tissues. A tissue is a collection of similar cells 
 devoted to the same work; or, in other words, a tissue 
 is a set of cells having the same structure and the same 
 function. Thus we have muscular tissue, nervous tissue, 
 bony tissue, etc. 
 
 Cells. The whole body is made up of small parts, called 
 cells, which are to be compared to the bricks in a house. 
 These cells are of various shapes in the different tissues. 
 The living material of the body is called protoplasm. It is 
 a jelly-like substance resembling the 
 white of an egg, though often pre- 
 senting a dotted appearance. A cell, 
 in its simplest form, is merely a dis- 
 tinct particle of protoplasm. Each Nucleus 
 cell usually has, however, a more Fig. i. Epithelial ceils from 
 
 J . . the Inside of the Cheek. 
 
 dense central part, called the nucleus. 
 
 The great majority of cells have a distinct covering or 
 cell-wall. A grape or cherry serves very well to illustrate 
 a cell. The skin represents the cell-wall, the pulp corre- 
 sponds to the protoplasm, and the seed to the nucleus. 
 (See Fig. 39, Cells of the Epidermis.) 
 
 Division of Labor in a Community. We are all aware 
 of the advantages of division of labor in a community. If 
 each person learns to do one thing well, all can work 
 together economically for the common good, time is saved, 
 and cheaper and better goods are produced. 
 
 Division of Labor in the Body. In the body there is a 
 division of labor similar to that in a community. In the 
 first place each organ has its special work, and the various 
 organs act helpfulty together, each working for all the rest 
 and worked for by them. 
 
4 Physiology. 
 
 The general structure of all the cells is about the same, 
 yet they differ enough for us to tell them apart. They 
 differ more in their work than in their appearance. Each 
 has some one kind of work that it can do well, and to 
 which it devotes itself. The nerve cells receive impressions 
 from the outer world, carry nerve currents, and control the 
 various actions of the body. The muscle cells have as 
 their work the production of motion. 
 
 The Life of Cells. Each cell must take food for itself 
 and grow. Each has a birth, life, and death, as each indi- 
 vidual in a community of men ; and as the community 
 continues, while the individual members are constantly 
 changing, so, in the body, while the form remains about 
 the same from year to year (in the adult), the cells are 
 continually changing, some dying, and others taking their 
 places. Thus it is seen that though the cells are packed 
 closely together and though they work in groups, each cell 
 leads, in one sense, an independent life. Like the indi- 
 vidual in the community, each lives for itself, yet all work 
 together for the common good. 
 
CHAPTER II, 
 THE BONES, 
 
 The Two Parts of a Skeleton. The skeleton consists of 
 two portions, (i) the central axis, or spinal column, to 
 which the head belongs; and (2) the limbs and the bones 
 belonging to them. 
 
 The Uses of the Bones. i . The skeleton gives the form 
 to the body. 
 
 2. It supports the softer tissues. 
 
 3. It protects softer parts, as the brain in the skull, the 
 spinal cord in the spinal column, the heart and lungs in 
 the chest, etc. 
 
 4. The bones serve as levers in producing motion and 
 locomotion. 
 
 Study of a Vertebra. Take a vertebra from the middle of the spinal 
 column : 
 
 1. Its most solid part is its body. 
 
 2. On the dorsal side of this is the neural arch, forming with the 
 body the neural ring, through which the spinal cord passes. 
 
 3. From this arch there extend projections, or processes. Hold the 
 vertebra by the tip of its longest process, and place it beside the cor- 
 responding vertebra in the complete skeleton. Note that : 
 
 (a) The body is flattened where it fits against the vertebras above 
 and below it ; 
 
 () The holes in the vertebras form a passage for the spinal cord ; 
 
 (c} The middle projection is the spinous process, and the series of 
 spinous processes form the ridge of the backbone ; 
 
 (d) The two side projections are the transverse processes. 
 
 5 
 
6 Physiology. 
 
 Fit together two vertebras in their proper order and observe that : 
 (e) The openings at the sides, through which the spinal nerves pass, 
 are iormed by notches, or grooves, in the two vertebras. 
 
 Neural Arch 
 
 Body 
 
 Transverse Process 
 
 ..Spinous Process 
 
 Neural Ring 
 Fig. 2. Upper View of Thoracic Vertebra. 
 
 Demi-facet for Head of Rib 
 
 Body 
 
 Anterior Articular 
 Process 
 
 Facet for Tubercle ot 
 Rib 
 
 X Transverse Process 
 
 ...Spinous Process 
 
 Fig. 3. Left Side View of Thoracic Vertebra. 
 
 (/) The two projections extending upward from the ring of one 
 vertebra fit against two projections extending downward from the other 
 vertebra. These are the anterior and posterior articular processes. 
 
 The Spinal Column. The central part of the skeleton 
 is the backbone, or spinal column^ As a whole it is a 
 
The Bones. 7 
 
 column, widening toward the base, composed of a series of 
 separate bones called vertebras. 
 
 Each vertebra has seven projections, four for joining 
 other vertebras (two upper and two lower), two side, and 
 one spinous. 
 
 Hole for Blood Tubes f&^lfiM&K^ Anterior Articular- Facet 
 
 Neural Arch 
 
 Body _ 
 
 Spinous Process 
 
 X \ Neural Ring 
 
 Fig. 4. Upper View of Cervical Vertebra. 
 
 Body 
 
 Spinous Process 
 Fig. 5. Left Side View of Cervical Vertebra. 
 
 How the Vertebras Fit Together. The smooth places 
 where the projections join are called facets. Observe on 
 each side of the body of the vertebra a facet where the 
 head of the rib joined it. There is also a facet on the side 
 process where the side of the rib joined it. 
 
 The Cervical Vertebras. The seven cervical (neck) 
 vertebras have holes through their side projections for the 
 passage of blood tubes. 
 
8 
 
 Physiology. 
 
 FLAT BONES OF THE SKULL. 
 
 r-THE CRANIUM, 
 
 NASAL BONES 
 
 J-MALAR (CHEEK) BONE. 
 -SUPERIOR MAXILLARY BONES 
 -INFERIOR MAXILLARY BONE 
 SPINAL COLUMN. CERVICAL REGION* 
 
 SHOULDER BLADE - 
 
 Fig. 6. Side View of the Human Skeleton. 
 
The Bones. 
 
 TABLE OF THE BONES. 
 
 HEAD (28) 
 
 Skull (8) 
 
 Face (14) 
 
 Ears (6) 
 
 CERVICAL REGION (8) 
 
 THORAX (37, 
 
 UPPER EXTREMITIES (64) 
 
 LUMBAR REGION (5) 
 PELVIS (4) 
 
 Frontal (forehead). 
 
 2 Temporal (temples). 
 
 2 Parietal (side). 
 
 Occipital (posterior base). 
 
 Sphenoid (base). 
 
 Ethmoid (base of nose and between eyes), 
 
 2 Superior Maxillas( upper jaw). 
 
 2 Nasal (bridge of nose). 
 
 2 Malar (cheek). 
 
 2 Lachrymal (inner front corner of orbit). 
 
 2 Turbinated (within nostrils). 
 
 2 Palate (posterior hard palate). 
 
 Vomer (nasal partition). 
 
 Inferior Maxilla (lower jaw). 
 
 (Malleus (hammer). 
 Stapes (stirrup). 
 Incus (anvil). 
 
 {7 Cervical Vertebras (neck). 
 Hyoid Bone (base of tongue). 
 
 {14 True, 6 False, 4 Floating Ribs. 
 12 Thoracic Vertebras (back) . 
 Sternum. 
 
 c , ,, /Clavicle (collar-bone). 
 
 ier " \ Scapula (shoulder-blade). 
 f Humerus (arm). 
 
 Arm - 
 
 Hand. 
 
 8 Carpal (wrist). 
 
 5 Metacarpal (palm). 
 
 14 Phalanges (fingers). 
 
 5 Lumbar Vertebras (loins). 
 
 ( 2 Innominates. 
 < Sacrum. 
 I Coccyx. 
 
 LOWER EXTREMITIES (60) 
 
 Thigh. 
 Leg. 
 
 Foot. 
 
 Femur. 
 
 [ Patella (knee-pan). 
 i Tibia (large bone). 
 v Fibula (outer bone), 
 r 7 Tarsal (instep, heel). 
 \ 5 Metatarsal (arch). 
 I 14 Phalanges (toes). 
 
 2 PHY 
 
io Physiology. 
 
 Atlas and Axis. The first vertebra, the atlas, has no 
 body. The second vertebra is the axis. It has a peg 
 which runs up into the atlas. In shaking the head, the 
 atlas, with the head, turns on this peg of the axis. In 
 nodding the head, the head simply rocks back and forth 
 on the atlas. 
 
 The Thoracic Vertebras. The twelve rib-supporting 
 vertebras are the thoracic vertebras. 
 
 The Lumbar Vertebras. The next five are the lumbar. 
 
 The Sacrum and Coccyx. The sacrum is composed of 
 five vertebras grown together, and the remaining four are 
 combined in the coccyx. 
 
 Review of the Spinal Column. Let the eye slowly re- 
 view the whole spinal column, noting in what points the 
 vertebras are all alike. Note also their differences. 
 
 Flexibility of the Spinal Column. In well-prepared 
 skeletons there are pads of felt which take the place of the 
 layers of cartilage that were between the vertebras. These 
 cartilages are tough and elastic, and firmly attached to the 
 vertebras above and below. They serve both to keep the 
 vertebras apart and to hold them together. When we bend 
 the shoulders to the right, the right edges of these carti- 
 lages are compressed, and the left edges are stretched, as 
 a piece of india rubber would be if it were glued be- 
 tween the ends of two spools, and the whole were slightly 
 bent. The cartilages also, by their elasticity, protect 
 the brain from the shock it would receive in jumping, 
 walking, etc. 
 
 Curves of the Spinal Column. View the spinal column 
 from the side. Draw a line representing all its curves. 
 
The Bones. 
 
 II 
 
 The Cavities of the Skeleton. Examine the cavity of the skull. If 
 the class has not a skull which has been sawed across, look into the 
 skuli cavity through the hole where the spinal cord joined the brain. 
 
 Neural Arch 
 
 Transverse Process 
 
 Body 
 
 Neura! Ring 
 Fig- 7. Upper View of Lumbar Vertebra. 
 
 Body 
 
 Transverse 
 Process 
 
 Spinous 
 Process 
 
 Posterior Articular Process 
 Fig. 8. Side View of Lumbar Vertebra. 
 
 Observe the conical shape of the chest. In the entire body the 
 bones and muscles about the shoulders usually make a reversed cone of 
 the upper part of the trunk. 
 
 Observe that most of the ribs are connected with the breastbone by 
 cartilages. 
 
 The upper limbs are jointed with the body only where the inner 
 ends of the collar bones join the breastbone. 
 
1 2 Physiology. 
 
 The Skeleton of a Cat or Rabbit. Examine the skeleton of a cat or 
 rabbit for the sake of comparison. Note especially the skull and spinal 
 column. This knowledge will aid in understanding the brain and 
 spinal cord. 
 
 The Weight of Bones. The bones make about one sixth 
 of the weight of the living body. When dried they may 
 lose half of their weight. 
 
 Microscopic Structure of Bone, i . Examine with a Hand Lens. 
 
 Hold a mounted cross-section of bone up to the light and examine with 
 a hand lens. The solid part of the bone will be seen to be pierced by 
 many small holes (or if the holes are filled, they will appear as black 
 spots). These are the cross-sections of the canals, through which run 
 the blood tubes, mainly lengthwise, through the bone. 
 
 2. Examine with the Low Power of a Compound Microscope. 
 Examine the section under the microscope, using a half-inch objective. 
 The bony matter will now be seen to be arranged in rings around the 
 canals, somewhat like the rings seen on the end of a log. 
 
 Between the rings are circles of elongated dark dots. These are 
 cavities in which were the live bone-corpuscles which built up the bone. 
 The bone was at first cartilage. Later, mineral matter was deposited, 
 forming true bone. 
 
 3. Examine with a High Power. Now examine the section under a 
 one-fifth-inch objective. From the dark cavities there run out, in every 
 direction, little crevices, appearing as fine black lines. Through the 
 haversian canals, lacunas, and crevices, the nourishing materials of the 
 blood reach all parts of the bone. 
 
 The Chemical Composition of Bone. i. Take a tall, narrow jar, or 
 a lamp chimney corked at one end, and nearly fill with water. Add 
 one sixth as much hydrochloric acid. Put into this a slender, dry bone, 
 such as a fibula or rib. In twenty-four hours take it out, rinse it thor- 
 oughly, and examine it. The acid will probably have dissolved out the 
 mineral matter and left the animal matter so soft that it may be tied 
 into a knot. 
 
 2. Lay a piece of bone on a shovel, or piece of sheet iron, and place 
 in the fire. The animal matter is burned out, leaving the brittle min- 
 eral matter* 
 
The Bones. 
 
 Composition of Bone. Bone is composed of two thirds 
 mineral matter and one third animal matter ; in childhood 
 the animal matter is in larger proportion, while hi old age 
 the mineral matter is in excess. The mineral matter is 
 chiefly phosphate of lime, while the animal matter is 
 largely gelatin. 
 
 Lamellas 
 
 Lacunas 
 
 Canaliculi Haversian Canal 
 
 Fig. 9. Cross-section of Bone. (Highly Magnified.) 
 
 the 
 
 Classification of Joints. i. Immovable, such as 
 joints between the bones of the skull ; 
 
 2. Mixed, such as the joints between the vertebras ; 
 
 3. Movable, which allow free motion between the parts; 
 
 (a) Ball and socket, as in the hip and shoulder ; 
 
 (b) Hinge, as in the knee and elbow; 
 
 (c) Pivot, as in the forearm, and between the atlas and 
 axis; 
 
14 Physiology. 
 
 (d) Gliding, as between the short bones of the wrist 
 and of the ankle. 
 
 Study of Joints. Examine these joints in the prepared skeleton, 
 and so far as possible, in sheep shanks, or in fresh specimens of rabbits. 
 Compare the ball and socket joints of the hip and shoulder. Also com- 
 pare the hinge joints of the knee and elbow. 
 
 Hygiene of the Bones. Sometimes the bones of chil- 
 dren are lacking in mineral matter, and are too soft and 
 flexible. This is true in a disease called rickets. Even if 
 the bones are natural, children should not be encouraged 
 to walk early, as bow-legs may result. Most bow-legged 
 persons seem to be active, and probably their muscles 
 developed faster than the bones. Unnatural positions or 
 over-use of special groups of muscles may result in lateral 
 curvature of the spine. The height of seats and desks 
 should be carefully looked after. 
 
 Sprains and Dislocations. Sprains and dislocations are 
 injuries to the joints, and often bring more serious results 
 than a broken bone. There should, usually, be complete 
 rest until the part can be used without pain. Otherwise a 
 stiffened joint may result. Hot water applied to a sprain 
 or bruise with rubbing will reduce soreness and may pre- 
 vent discoloration. But if there is inflammation, cold water 
 should be applied. Bandages may be needed for support. 
 
 Broken Bones. When a bone is broken, of course a 
 physician should be sent for. Care must be taken that the 
 limb be kept straight. If this is not done, the sharp ends 
 of the bone (see Fig. 22) may cut or tear the surrounding 
 tissues, or even cut blood tubes. So, if the person must 
 be carried, it is well to tie a piece of board under the limb 
 to keep from bending it. A cane, umbrella, or any light 
 rigid bar will serve for this purpose. 
 
The Bones. 15 
 
 Summary. I. The skeleton consists of the central axis and the 
 
 limbs. 
 
 2. Each vertebra consists of a body, ring (around spinal cord), and 
 processes. 
 
 3. Pads of cartilage connect the vertebras. 
 
 4. Throughout the bone there are tubes and crevices through which 
 it receives its nourishment from the blood. 
 
 5. Bone consists of animal matter with limy matter embedded in it. 
 
 6. Sprains should be treated carefully to avoid stiffened joints. 
 
 Questions. i. Why do the bones of old people break so much 
 more easily than those of children ? 
 
 2. What is the use of the central marrow ? 
 
 3. What is the work of the red marrow in the spongy ends of the 
 bones ? 
 
 4. What are " sesamoid " bones ? 
 
CHAPTER III. 
 MUSCLES AND MOTION. 
 
 Motion and Life. Motion is one of the surest signs of 
 life. While we are sitting still, as we say, there are fre- 
 quent slight motions of the head, body, and limbs. Even 
 during sleep the movements of breathing maybe seen; the 
 hand laid upon the chest may feel the beating of the heart, 
 and the finger detect the pulse in a number of places. We 
 must move to get our food, or at least to eat and digest it. 
 We often move to avoid injury. Motion is necessary for 
 speech and in the use of the sense organs. How are all 
 these motions produced? 
 
 Experiments with the Muscles in our own Bodies. i . Clasp the 
 front of the right upper arm ; draw up the forearm strongly and as far 
 as possible. Note the changes that are felt in the biceps muscle. 
 
 Fig. 10. The Shortening and Thickening of the Biceps Muscle in raising the Forearm 
 
 2. Repeat the experiment, and with the thumb and finger feel the 
 cord, or tendon, at the lower end of the muscle, just within the angle of 
 the elbow. 
 
 16 
 
Muscles and Motion. 17 
 
 3. Span the muscle, placing the tips of the fingers in the angle of the 
 elbow, and the tip of the thumb as far as you can up the arm ; again 
 bend the arm. What change in the muscle does this show ? Any 
 muscle that bends a Ijmb, as does the biceps, is called a flexor muscle. 
 
 4. Clasp the back of the upper right arm ; forcibly straighten the 
 arm. The muscle lying along the back of the arm is the triceps muscle. 
 It is called an extensor muscle because it extends, or straightens, the arm. 
 
 5 . Clasp the upper side of the, right forearm near the elbow ; clench 
 the right hand quickly and forcibly ; repeat rapidly. 
 
 6. Notice the mass of muscle at the base of the thumb ; pinch the 
 forefinger and thumb strongly together. What changes can be seen and 
 felt? 
 
 7. Place the hand on the outside of the shoulder ; raise the arm to 
 the horizontal position ; repeat with a weight in the hand. 
 
 8. Stand erect with the heels close to each other, but not quite 
 touching ; let the arms hang freely by the sides ; rise on tiptoes, with- 
 out moving otherwise ; repeat ten times. 
 
 9. Place the tips of the fingers on the angles of the lower jaw ; shut 
 the teeth firmly, and note the bulging of the masse ter muscle. 
 
 10. Press the fingers on the temples ; again shut the jaws firmly, and 
 feel the action of the temporal muscles. 
 
 By these experiments we learn that when a muscle works 
 it becomes shorter, thicker, and harder. 
 
 The Action of Muscle. The action of muscle is always 
 a " pull." The muscle shortens, at the same time thicken- 
 ing and hardening. It must be kept clearly in mind that 
 the work of the muscle is done by its shortening and not 
 by either the hardening or thickening. But the hardening 
 and thickening are often more noticeable than the shorten- 
 ing, and by means of them we may locate the muscle that 
 is producing any motion. 
 
 Action of Frog's Muscle. The action of muscle may be seen much 
 more clearly in a frog's calf muscle, as shown in Fig. 1 1 . When the 
 nerve is stimulated at " A " a nerve impulse runs along the nerve to the 
 muscle and makes it shorten and widen, raising the weight as shown in 
 the right half of the figure. 
 
i8 
 
 Physiology. 
 
 SHORTENED 
 
 ELONGATED 
 
 Fig. 1 1 . Action of the Calf Muscle of the Frog, showing the Relations of the 
 Sciatic Nerve. 
 
 Structure of Muscle. Chipped beef shows well the 
 structure of muscle. The white network is connective 
 
 tissue. Its work is to hold 
 Origin the parts of the muscle to- 
 
 ^Bundle of Muscle Fibers gether and tO Support the 
 
 muscle as a whole. In the 
 meshes of the white network 
 is the red muscle tissue. The 
 partitions which run all 
 Muscle sheath \ through the muscle are con- 
 
 CROSS SECTION . . , , 
 
 tmuous with the muscle 
 sheath, and both are con- 
 tinuous with the tendons at 
 the ends of the muscle. In 
 fresh muscle the sheath and 
 the partitions are transpar- 
 ent, and are not very easily 
 
 noticed. When meat is cooked or salted the connective 
 
 tissue becomes white and opaque. 
 
 f Muscle Fibers 
 eath \ 
 
 Tendon 
 
 Insertion 
 LONGITUDINAL SECTION 
 
 Fig. 12. The Structure of Muscle. 
 
Muscles and Motion. 
 
 Fig. 13. Two Striated Muscle 
 Fibers showing the termina- 
 tions of the Nerves. 
 
 Microscopic Structure of Muscle. If a tiny shred of 
 muscle, such as you may remove from the teeth with a 
 toothpick, be put in a drop of 
 slightly salted water and exam- 
 ined under a good microscope, the 
 fibers may be seen. These are 
 small thread-like bodies, with cross 
 markings, from which they are 
 called striated or striped mttscle 
 fibers. From the fact that they 
 are under the control of the will 
 they are called voluntary muscle 
 fibers. Not all striated muscle 
 fibers are voluntary. The heart 
 muscle fibers are in a special class, being striated but 
 involuntary. The muscles connected with the bones 
 are called skeletal muscles. They are all striated and 
 all voluntary. 
 
 Plain Muscle Fibers. In the walls of the arteries, of 
 the gullet, the stomach, the in- 
 testines, the bladder, and else- 
 where, there are muscle fibers 
 of a different kind from those of 
 the skeleton. These fibers are 
 spindle-shaped cells, as shown in 
 Fig. 14, with a nucleus near the 
 center, and do not have the cross- 
 markings. Hence they are called 
 plain, smooth, or un-striated mus- 
 cle fibers. Owing to the fact 
 that they are not under the con- 
 trol of the will they are called involuntary muscle fibers. 
 
 Nucleus 
 
 Isolated Fibers 
 
 " Fibers Joined 
 
 Fig. 14. Plain (unstriated) Muscle 
 Fibers. 
 
20 
 
 Physiology. 
 
 The involuntary muscle fibers are usually much slower in 
 their action than the voluntary fibers. 
 
 Heart Muscle Fiber. The 
 
 fibers which make up heart 
 muscle are different in appear- 
 ance from either the striated or 
 the smooth muscle fibers. They 
 are more or less branched, as 
 shown in Fig. 15. No sheath 
 has. been found on these fibers. 
 
 A Muscle Fiber is a Cell. - 
 
 It is easily seen that each plain 
 muscle fiber is a single cell, hav- 
 ing its distinct nucleus. The 
 
 Fig. is. Muscle Fibers from the Heart, same is true of the heart muscle 
 
 magnified, showing their cross striae, fib though they are not SO 
 
 divisions, and junctions. J 
 
 The nuclei and cell-junctions are shown simple, being more Or leSS 
 only on the right hand side of the 
 
 figure. branched. 
 
 Effect of Cooking Muscle. In well-cooked corned beef 
 the connective tissue is thoroughly softened, and the mus- 
 cle fibers are easily separated. Thorough cooking, espe- 
 cially stewing, will soften the connective tissue, and may 
 make tender meat that, cooked otherwise, would be very 
 tough on account of the large amount of connective tissue. 
 
 Imitation of Structure of Muscle. Take a number of pieces of red 
 cord to represent the muscle fibers. Wrap each in white tissue paper; 
 this represents a single fiber sheath. Lay a number of these side by 
 side, and wrap them all in a common sheath. Let the tissue paper pro- 
 ject beyond the ends of the threads, and here compress it into a com- 
 pact cylinder ; this last represents the tendon. 
 
 Connective Tissue the Skeleton of Muscle. If all the 
 
 muscle fibers were removed from- a muscle, the sheaths 
 
Muscles and Motion. 21 
 
 and partitions would remain, and show the form of the 
 muscle just as the partitions remain in a squeezed orange 
 or lemon. The connective tissue forms a framework for 
 all the soft tissues of the body, and if their working cells 
 were removed, the connective tissue would remain, and 
 show, more or less completely, the form of the part. Con- 
 nective tissue may be called, therefore, the skeleton of the 
 soft tissues. Muscle consists, then, of soft transparent 
 tubes, filled with a semi-fluid muscle substance. By scrap- 
 ing the surface of a steak the muscle substance may be 
 obtained, leaving the connective tissue. This is a good 
 way to get the nutritious part of beef for an invalid. 
 
 Importance of Muscles. The muscles make up nearly 
 half the weight of the body. This fact of itself should 
 lead us to conclude that the muscles are of great impor- 
 tance. Muscles are used in nearly every action of the 
 body, not only in locomotion, but in respiration, circulation, 
 digestion, speech, etc. It is very necessary that at the 
 beginning we understand their action. 
 
 Duration of Muscle Shortening. A muscle cannot be 
 kept shortened for any great length of time. If one holds 
 the arm out horizontally as long as he can, he soon feels 
 fatigue, later pain, and he is likely to feel a soreness in the 
 muscle for several days afterward. The law of muscle 
 action is to alternate periods of rest with periods of action. 
 In many exercises, as in walking, the limbs act alternately, 
 one resting or recovering while the other works. 
 
 Alternate Action of Flexors and Extensors. When the 
 biceps muscle shortens and bends the arm, the triceps 
 lengthens (see Fig. 16). When the triceps shortens, as in 
 straightening the arm, the biceps lengthens. If the biceps 
 and triceps both shorten at the same time, and with equal 
 
22 
 
 Physiology, 
 
 Deltoid 
 
 Serratus Magnus.... 
 
 Rectus Femoris 
 
 Tibialis Anticus 
 
 Pectoralis Major 
 
 Rectus Abdominalis 
 
 Extensors of the Hand 
 Flexors of the Hand 
 
 Sartorius 
 
 Vastus Externus 
 
 Extensors of the Toes 
 
 Fig. 16. Front View of the Superficial Muscles 
 
Muscles and Motion. 
 
 Extensors of the Hand 
 
 Triceps 
 
 Latissimus Dorsi.... 
 
 Gluteus Maximus 
 
 Vastus Externus.... 
 
 Ftexors of the Foot 
 
 Trapezius 
 
 ..- Deltoid 
 
 ... Flexors of the Hand 
 
 Biceps Cruris 
 
 . Gastrocnemius 
 
 Tendo Achi 
 
 Fig. 17- Back View of the Superficial Muscles. 
 
24 Physiology. 
 
 force, no motion will be produced. Sometimes this is done 
 on purpose, as when, in wrestling "square-hold," one holds 
 the arm rigidly bent at a right angle, to keep his opponent 
 from either pushing or pulling him. In the body are many 
 flexors and extensors " paired off"; they act alternately, 
 like the biceps and triceps in the arm. 
 
 Symmetrical Development of the Muscles. The muscles 
 of the two sides of the body are the same in number and 
 arrangement. At birth they are probably about equal in 
 size, weight, and strength. Most persons early become 
 right-handed, and the greater use of the right hand and 
 shoulder makes the muscles of this side larger and heavier. 
 The muscles pulling on the bones slightly modify them in 
 shape. The whole body may become noticeably one-sided. 
 Most persons step harder on one foot than on the other, as 
 shown by the sound of the footstep, or by the constant 
 wearing of one shoe sole or heel faster than the other. In 
 many persons one shoulder is carried higher than the 
 other. 
 
 To Overcome One-sidedness. Symmetrical development 
 should be carefully sought, and any tendency to a one- 
 sided development should, so far as possible, be avoided. 
 We should use the left hand more. There are many ad- 
 vantages in being able to use either hand. In carving, in 
 shaving, in bandaging, in giving medicine, it may be neces- 
 sary to use the left hand skillfully. The pianist and the 
 harpist use the two hands about equally, while the violinist 
 puts much more skill into his left hand. Trainers of 
 athletes often begin by developing the left side of the 
 body till it equals the right in size and strength. 
 
 Muscles the Source of Strength. Our strength depends 
 on our muscles. It is a fine thing to have strong, well- 
 
Muscles and Motion. 25 
 
 developed muscles, not only because they give beauty of 
 form, but because extra strength and endurance may be 
 needed in case of accident, to save one's own life or that 
 of others. In a case of fire the ability to climb, to go up 
 or down a rope " hand over hand," may be all-important. 
 Any one's life may depend on his ability to run far and 
 swiftly, to swim, to jump, or to lift a heavy weight 
 
 The Number of Muscles. There are over five hundred 
 muscles in the human body. These vary in size from less 
 than an inch in length, in the ear and in the larynx, to a 
 foot and a half long in the thigh. 
 
 The Arrangement of Muscles. The muscles of the two 
 sides of the body are paired, and naturally are about equal 
 in size and strength. The muscles of the limbs are further 
 paired into flexors, which bend, and the extensors, which 
 straighten the limbs. The muscles are also arranged more 
 or less in layers. There is generally an outer layer and a 
 more deep-seated layer. 
 
 Forms of Muscles. Muscles are of various shapes. 
 The prevailing form in the limbs is spindle-shaped, or 
 fusiform. Some muscles are flat, some have their fibers 
 arranged like the barbs of a feather, and are hence called 
 penniform. Some muscles have a tendon in the middle 
 which runs through a loop, as in the case of the muscle 
 which depresses the lower jaw. Muscles which close open- 
 ings are circular, and are -called sphincter muscles. 
 
 Peculiar Muscles. The diaphragm is a sheet of muscle 
 that forms a partition between the chest and the abdomen. 
 It is arched^ and has a clear tendinous center. The ab- 
 dominal muscles form a wall to hold the organs of the 
 abdominal cavity. These muscles also aid in breathing, 
 3 PHY 
 
26 Physiology. 
 
 especially in f.orced expiration, as after violent exercise and 
 in coughing. The abdominal wall consists of several layers 
 of muscle. 
 
 Muscles of Expression. The facial expression is due 
 to the action of the muscles of the face, which in turn are 
 under control of the cranial nerves. The habitual position 
 becomes somewhat " fixed," so it is true that character is 
 often shown by "the looks." Cultivation of happy thoughts 
 therefore tends to make one better looking. 
 
 Muscles and Fat. Fat fills in space between muscles, 
 and, if abundant, forms a layer over the muscles. One 
 notable instance is the hollow triangular space between 
 the muscles of the cheek. If there is very little fat, a 
 depression is seen, forming the " hollow cheeks." But an 
 abundance of fat makes a corresponding elevation. 
 
 Convulsions. These spasmodic actions are due to dis- 
 ordered action of the muscles, and to a disturbed action 
 of the nervous system that controls the muscles. Various 
 disturbances, such as indigestion, may by reflex action 
 bring on convulsions. 
 
 Summary. i. Motion is involved in nearly every action of the body. 
 
 2. The action of muscle is a shortening, accompanied by a thicken- 
 ing and hardening. 
 
 3. Muscle consists of fibers with a connective tissue sheath for each 
 fiber, bundle of fibers, and for the muscle as a whole. 
 
 4. The skeletal muscle fibers are striated. 
 
 5. The muscles make about half the body's weight. 
 
 6. Muscles can remain shortened only a little while. 
 
 7. The muscles should be developed symmetrically. 
 
 8. There are about five hundred muscles in the body. 
 
 9. The muscles of the two sides are alike. 
 
 10. The muscles of the limbs are spindle-shaped. 
 
 Questions. i. What effect is produced by carrying a heavy satchel 
 for a long distance without resting ? 
 
Muscles and Motion. 27 
 
 2. Which is more tiresome, standing still or walking? Why? 
 
 3. When the boy, who thinks he can strike a hard blow, says, 
 " Feel my muscle," does he usually call attention to the muscle used in 
 striking? 
 
 4. Why are the sides of the body often sore after walking on icy 
 pavements ? 
 
CHAPTER IV. 
 THE MUSCLES AND THE BONES. 
 
 Skeletal Muscles. When we look at the skinned car- 
 cass of an animal in the market, we observe that the mus- 
 cles almost completely cover the bones. Those which are 
 attached to the bones are called skeletal muscles. They 
 act upon them as levers, making the motion strong, quick, 
 and accurate. Without bones our motions would be like 
 those of an earthworm or slug, slow and uncertain. The 
 muscles, acting through the bones, can lift a weight that 
 would crush the muscles if laid directly upon them, while 
 a bone, able to support a heavy weight without being 
 crushed, has no power in itself. The muscles have active 
 strength, the bones have passive strength. 
 
 Relation of the Muscles and the Bones. Examine Figs. 
 10, 1 6, and 17. For this work you should have the bones of 
 an arm. Locate the biceps muscle in its relations to these 
 bones as shown in the figures. Feel the biceps of your 
 arm. Note that its thickest part is opposite the most 
 slender part of the bone. But at the enlarged end of the 
 bone the muscle has narrowed to a slender tendon which 
 passes over the joint to be attached to the next bone, thus 
 giving more slenderness, flexibility, and freedom of motion 
 to the joint. Most of the skeletal muscles are attached to 
 bones. There are some exceptions, such as the circular 
 muscle which closes the mouth when the lips are pursed up. 
 
 X-Rays and their Use, By means of X-ray apparatus 
 
 28 
 
The Muscles and the Bones, 
 
 29 
 
 Fig 18. X-Ray Photograph of Hand showing Shot carried for Twenty Years. 
 (From Recreation, by permission of G. O. Shields.) 
 
 the physician can photograph through the body and show 
 the location of the bones. This process is useful in show- 
 ing injuries to the bones. It is also especially useful in 
 
30 Physiology. 
 
 locating a bullet or other solid body in the flesh, which 
 probing of ten, fails to discover. 
 
 Levers. The main facts to be learned about a lever are 
 that it is a rigid bar ; the point about which the lever turns 
 is called the fulcrum ; the place where the power is ap- 
 plied is called the power ; and the part to be moved is 
 called the weight. In the body, the fulcrum is some joint, 
 the power is the place where the muscle is attached, and 
 the weight is the part to be moved. 
 
 Kinds of Levers. There are three kinds of levers. In 
 the first class the fulcrum is between the power and the 
 weight, as in prying over a block with a crowbar. In 
 the second class the weight is between the power and 
 the fulcrum, as in a wheelbarrow. In the third class the 
 
 (I) Tapping on Floor. (2) Rising on Toe. (3) Lifting Weight 
 
 Fig. 19. Three Kinds of Levers as shown by the Foot. 
 P Power. W Weight. F Fulcrum. 
 
 power is between the fulcrum and the weight, as in rais- 
 ing the forearm (see upper part of Fig. 19). We may 
 find many examples of levers in the body if we look for 
 them. 
 
 Kinds of Levers shown by the Foot. The different 
 
Ball 
 
 Articular Extremity 
 
 The Muscles and the Bones. 31 
 
 classes of levers may be illustrated by different motions 
 
 of the foot. In tapping the toes on the floor while 
 
 the heel is lifted, or in pressing down the ball of the 
 
 foot while running the treadle of 
 
 a sewing machine, we have an 
 
 example of a first-class lever. In 
 
 raising the weight of the body on 
 
 tiptoes, or as the foot is used in 
 
 taking each step, the foot is used 
 
 as a lever of the second class. 
 
 When one lifts a weight with the 
 
 toes, the foot is used as a lever 
 
 of the third class. (See Fig. 19.) 
 
 Advantages of Levers in the Body. - Medullar y Cavity 
 
 If the arm consisted merely of the biceps 
 muscle, suspended from the shoulder, it 
 is evident that its only action would be 
 a straight pull. Suppose the biceps, 
 thus hanging alone from the shoulder, 
 had a hook at its lower end, it could, 
 when it shortened, lift a weight just as 
 far as it shortened, and no farther. It 
 could not swing the weight outward, or 
 push it upward. But from the way in 
 which the biceps is attached to the fore-, 
 arm (see Fig. 10), when the muscle 
 shortens an inch it may move the hand Fig. 20. 
 a foot. Of course the hand moves much 
 faster, and we have a great gain in speed by reason of this lever arrange- 
 ment. But we cannot lift so heavy a weight at this faster rate, as we 
 could at the elbow. 
 
 Study of One of the Long Bones. For this, take, preferably, a femur 
 or a humerus. Let us suppose we have a femur. 
 
 i. Observe its shape, cylindrical, somewhat curved, enlarged at 
 the ends. 
 
 Hard Bone 
 
 Spongy Bone 
 Articular Extremity 
 
 Longitudinal Section of 
 Femur. 
 
Physiology. 
 
 2. The ends have smooth places, where they fitted other bones. 
 
 3. Along the sides, especially near the ends, are ridges and projec- 
 tions, where the muscles were attached. 
 
 4. There are small holes in the bone, where blood tubes passed in 
 
 and out. 
 
 5 . Saw a femur in two, lengthwise, and make 
 a drawing showing : 
 
 (a) The central marrow cavity. 
 () The spongy extremities, noting especially 
 the directions of the bony plates and fibers. 
 
 6. Observe the width of the lower end of 
 the femur, where it rests on the tibia. Sup- 
 pose these two bones were as narrow at their 
 ends, where they meet to form the knee joint, 
 as they are at their centers, what kind of a joint 
 would they make ? Illustrate by piling up a 
 number of spools on end ; the column is more 
 lightened than it is weakened by the hollow- 
 ing out of the sides of each spool. And the 
 central hollow of the spool does not greatly 
 weaken it. 
 
 Joints. The ends of the bones, where they 
 fit together in the joints, are covered with a 
 layer of smooth, elastic, whitish or transparent 
 cartilage. The motion in the joints is made 
 still more easy by the synovia, resembling white 
 of egg. The ends of the bones are held to- 
 gether by tough bands and cords of ligament, 
 a form of connective tissue very much like ten- 
 don. Bones are closely covered by a tough 
 coat of connective tissue called the periosteum. 
 
 All these structures can easily be found by 
 dissecting a sheep shank gotten from the 
 butcher, or in the hind leg of a rabbit. 
 
 Fig. 2 1 . Action of the Mus- 
 cles in Standing. 
 
 . Standing. Although we are not ordinarily conscious 
 of the fact, when we are standing still we are using many 
 muscles. The accompanying figure illustrates how some 
 of the muscles act in keeping the body upright. Our 
 
The Muscles and the Bones. 33 
 
 weight, or, we would better say, the force of gravity, is 
 continually trying to pull us down to the ground. The 
 joints are all freely movable, and hence as soon as the 
 muscles cease to act properly, in balancing against each 
 other, we lose our balance, and fall if we do not quickly 
 regain it. 
 
 Walking. In walking, we lean forward, and if we take 
 no further action we fall. But we keep one foot on the 
 ground, pushing the body forward, while the other leg is 
 bent and carried forward to save us from the fall. We 
 catch the body on this foot, and repeat the action. To 
 show how we are really repeatedly falling and catching 
 ourselves, recall how likely one is to fall if some obstacle 
 is placed in the way of the foot as it moves forward to 
 catch the weight of the body. 
 
 Running. In running, the action is more vigorous. 
 The force exerted by the rear leg is now greater. It gives 
 such a push as to make the body clear the ground, whereas 
 in walking, the rear foot is not lifted till the front foot 
 touches the ground. But in running there is a time when 
 both feet are off the ground. 
 
 Locomotion by Reaction. Take two broomsticks and place them 
 crosswise under the ends of a board. Run along the board. This 
 shows that the direct effort in running is to push one's support from 
 under him. Our effort in moving forward is to push the earth out from 
 under us, and it is by reaction that we go forward. It is the same 
 problem with the fish swimming forward by striking backward and 
 sideways against the water, and with the bird beating downward and 
 backward upon the air. 
 
 Bones combine Lightness and Strength. The muscles, 
 then, make use of the bones as levers. We carry these 
 levers with us all the time. Hence the desirability of hav- 
 ing them light as well as strong. A hollow pillar or hoi- 
 
34 Physiology. 
 
 low tube has greater strength than the same amount of 
 material in the form of a solid cylinder. The long bones 
 of the limbs are hollow, and near their ends, where we 
 have found that they need to be enlarged, we find a 
 spongy structure, where lightness and strength are secured 
 by the interlacing fibers and plates of bony material. 
 
 Muscles always Stretched. The muscles are always 
 slightly stretched, as shown by the fact that when a cut 
 
 is made into a muscle the 
 wound gapes open; the ten- 
 sion of the muscle is further 
 shown by the fact that when 
 a bone is broken, as in the 
 upper arm or thigh, the ends 
 of the bones may slip by each 
 other, and the limb has to be 
 strongly stretched to bring the 
 ends back together. Muscles 
 act better when slightly 
 stretched, and probably need a 
 slight resistant action of the 
 opposing muscle. 
 
 What makes the Muscles act 
 
 Fig. 22. Fracture of the Humerus. 
 
 in Harmony ? Have you ever 
 
 seen two persons,' one using the right hand and the other 
 the left, try to sew, one holding the cloth, the other using 
 the needle? Would they get along well? Suppose one 
 were to hold the needle, and the other were to try to thread 
 it, each using one hand. Why is it that the right and left 
 hands of two persons cannot work so well together as the 
 right and left hands of one person ? What connection is 
 there between the two, that one knows just what the other 
 
The Muscles and the Bones. 35 
 
 is doing and when it does it ? Why can two individuals 
 never, with any amount of practice, work so in unity as the 
 parts of the individual ? 
 
 Let us seek the answer to these questions in the follow- 
 ing lessons. J 
 
 Reading. " How to Get Strong and How to Stay So," Blaikie, 
 " Sound Bodies for Our Boys and Girls, 1 ' Blaikie. 
 
 Summary. i . In the limbs the muscles are spindle-shaped and have 
 their greatest diameter opposite the central, or narrower, portions of the 
 bones, concealing the fact that the bones are largest at the ends, as is 
 so evident in the skeleton. 
 
 2. The bones serve as levers by which the muscles exert their force. 
 
 3. The bones of the limbs are hollow cylinders combining lightness 
 and strength. 
 
 4. The joints have a smooth motion due to the cartilage and synovia. 
 
 5. Locomotion is brought about by reaction. 
 
 Questions. i. Find other examples of levers in the body. 
 
 2. Find examples of the three kinds of levers, not in the body, which 
 we use often. 
 
 3. Why is it easier to sit with one leg crossed over the other ? 
 
 4. How may the arms be used to illustrate the three kinds of levers ? 
 
 5. Analyze and explain jumping, hopping, etc. 
 
CHAPTER V. 
 
 THE GENERAL FUNCTIONS OF THE NERVOUS SYSTEM. 
 SENSATION AND MOTION. 
 
 What makes Muscles Shorten? We have seen that the 
 muscles have the power of shortening ; that in shortening 
 they act on the bones as levers to produce our varied mo- 
 tions. What makes the muscles shorten ? 
 
 Voluntary and Involuntary Motions. Some motions we 
 will to make. We will to sit, to stand, to walk, to run, or 
 to stretch out the hand. Such motions, originating in a 
 brain activity, are called voluntary. Other motions are 
 involuntary. The will does not control the heart-beat. 
 Most persons cannot keep from winking when a quick 
 motion is made toward the face, even if they know they 
 will not be hit. But all of these motions, both voluntary 
 and involuntary, depend upon the nervous system. 
 
 The Cerebro-spinal Nervous System. This consists of 
 the brain, the spinal cord, and the spinal nerves. 
 
 The Brain. There are two main parts of the brain, the 
 cerebrum, which fills all the upper part of the cranium, 
 and the cerebellum, very much smaller, in the lower back 
 part of the cranium. The cerebrum is divided into right 
 and left hemispheres by a lengthwise groove. The sur- 
 face of the cerebrum is covered with ridges called convo- 
 lutions. The outside of the brain is of gray matter, 
 consisting of cells, while the inside is white, consisting of 
 nerve fibers. 
 
 36 
 
Nervous System. 
 
 37 
 
 Fig. 23. The Cerebro-spinal Nervous System. 
 
 Two Functions of the Brain. Only two functions of the 
 brain are to be noticed now. One is sensation, the other 
 motion, or rather the control of motion. Nerve currents 
 that come to the brain, produce all our sensations. Sen- 
 
38 Physiology. 
 
 sation is in the gray matter on the outside of the brain. 
 When we wish to move any part of the body, the first 
 thing is to will to do it. This action is also in the gray 
 matter on the outside of the brain, but in different parts 
 from those which have sensation. The act of willing to do 
 anything sends nerve currents, or impulses, along nerve 
 fibers to the part that is to be set to work. The white 
 fibers of the inside of the brain connect the cells of the 
 gray matter with the various parts of the body through the 
 base of the brain, the spinal cord, and the spinal nerves. 
 
 The Spinal Cord. The spinal cord is a cylindrical body 
 extending from the brain along the cavity of the spinal 
 column. Its diameter is not uniform throughout. Between 
 the shoulders is an enlargement called the cervical enlarge- 
 ment, where the large nerves are given off to the arms. 
 In the region of the loins is the lumbar enlargement, where 
 the nerves are given off to supply the legs. The outside 
 of the cord is white, but the central portion consists of 
 gray matter. The white portion is made up of fibers, but 
 the gray matter consists of nerve cells as well. 
 
 The Spinal Nerves. These are given off in pairs from 
 the sides of the spinal cord. They pass out through notches 
 between the successive vertebras, so there is no danger of 
 their being crushed, or even pinched, when the backbone 
 bends. In the regions of the shoulders and loins the 
 spinal nerves are large, as they supply the large muscles 
 of the limbs ; but in the middle of the back, where only 
 the muscles of the body wall are supplied, the nerves are 
 small. We have thirty-one pairs of spinal nerves. 
 
 The Roots of the Spinal Nerves. Each spinal nerve 
 arises by two roots, one nearer the back, called the dorsal 
 
Nervous System. 39 
 
 root, the other nearer the ventral surface, the ventral root 
 These two roots soon unite to form one spinal nerve. 
 
 Structure of Nerves. If we trace a nerve outward, we 
 find that it is continually subdividing. This division con- 
 tinues until the branches are too small to be seen by the 
 naked eye. Microscopic examination shows that a nerve 
 is made up of a great number of fibers bound together in 
 a common sheath of connective tissue, as is the case with 
 muscle. When the nerve divides, there is ordinarily no 
 true branching or forking, but certain of the fibers simply 
 separate from the rest, as in the separation of the fibers in 
 floss silk. 
 
 Nerve Fiber Sheath 
 
 Axis Cylinder 
 
 Medullary Sheath 
 Fig. 24. Structure of a Nerve Fiber. 
 
 Structure of a Nerve Fiber. A single nerve fiber is too 
 small to be seen by the naked eye, being only about one 
 two-thousandth of an inch in diameter. It consists of the 
 following parts : 
 
 1. The axis cylinder, a central strand, or core, of semi- 
 transparent, gray material. 
 
 2. The medullary sheath is a layer of white, oily ma- 
 terial around the axis cylinder. 
 
 3. The nerve fiber sheath is a thin, transparent outer 
 sheath of connective tissue. 
 
 Function of Nerve Fibers. The only function of the 
 nerve fiber is to convey nerve impulses. The nerve im- 
 pulse passes along the axis cylinder as an electric current 
 passes along an insulated wire. 
 
4O Physiology. 
 
 Afferent and Efferent Nerve Fibers. Nerve fibers that 
 carry impulses toward the spinal cord or brain are called 
 afferent nerve fibers. Fibers that convey impulses from 
 the brain or spinal cord are efferent nerve fibers. 
 
 Cross-section of the Spinal Cord. If a thin slice of 
 the spinal cord be made as shown in Fig. 25, it will be 
 seen that the central part is darker in color than the outer 
 part. The central part is known as the gray matter, in 
 distinction from the rest, which is called the white matter. 
 
 Dorsal Septum 
 
 Dorsal or Sensor 
 Root 
 
 Ventral Fissure 
 Ventral or Motor Root 
 
 Fig. 25. Cross-section of Spinal Cord. 
 
 The white matter of the nervous system is made up of 
 nerve fibers, whose structure and use we have just con- 
 sidered. " But the gray matter has a different structure and 
 a different function. Instead of being made up mainly of 
 fibers, it is composed of cells, one of the forms of which is 
 represented in Fig. 26. Some of the branches of these 
 cells are continued, and become the axis cylinders of 
 nerves, and it is believed that every nerve fiber begins as 
 a branch of some nerve cell. 
 
Nervous System. 
 
 Functions of the Spinal Cord. The spinal cord has two 
 main functions : 
 
 i. Its conducting power, by means of the white fibers 
 which make up the outer part of the cord. These fibers 
 
 connect the gray matter of 
 the brain with all parts of the 
 body, and carry messages to 
 and from the brain. 
 
 2. The gray matter is the 
 center of the reflex actions of 
 
 Branched Processes 
 
 Fig. 26. A Large Nerve Cell from the 4-V.p 
 Gray Matter of the Spinal Cord. 
 
 the cord. 
 
 Ganglions. Masses of 
 nerve cells make up nerve 
 centers, or ganglions, such 
 as are on the dorsal roots of 
 spinal nerves. These 
 also would show under the 
 microscope that their chief constituent is a collection of nerve 
 cells which give off one or more branches. The gray matter 
 of the spinal cord is a collection of ganglions. 
 
 Reflex Action in a Sleeping Child. If the sole of the foot of a sleep- 
 ing child is gently tickled, the foot will be drawn up. The child has no 
 sensation. The brain has nothing to do with it. It is purely reflex 
 action. A nerve impulse has gone to the spinal cord, and another 
 impulse has been sent out to make the needed movement. But some- 
 times the child may be half awake and the foot might be drawn up by 
 voluntary action. Let us take another case, with which nearly every 
 one is familiar, to show that the brain has nothing to do with reflex 
 action. 
 
 A Hen with its Head cut off. Nearly everybody knows that after a 
 hen's head is cut off, it "flops" around for some time, and that fre- 
 quently when one takes hold of its feet to pick it up, it begins to struggle. 
 Now this also is reflex action of the spinal cord. And there can be no 
 doubt that the brain has nothing whatever to do with it. 
 4 PHY 
 
42 Physiology. 
 
 The Gray Matter of the Cord the Center of Reflex 
 Action. In reflex action the current runs up the nerve 
 to the spinal cord. The gray matter of the central part of 
 
 Afferent Dorsal Root 
 
 Sensor Fiber 
 
 Motor Fiber 
 
 Efferent v 
 
 Ventral Root 
 
 Fig. 27. Diagram of Reflex Action of the Spinal Cord. 
 (After Landois and Stirling.) 
 
 the cord receives the message, and sends back a nerve 
 impulse to the muscles, to make them shorten and pull the 
 foot away from the source of irritation. 
 
 The Parts Essential to Reflex Action of the Spinal 
 Cord: I. A' sensitive surface (the skin, for instance). 
 2. Afferent nerve fibers. 3. A nerve cell, or cells, in 
 the center of the spinal cord. 4. Efferent nerve fibers. 
 5. Working organ, as muscle or gland. 
 
 Steps in Reflex Action. In the above examples the 
 steps in order are : 
 
 i. Stimulation of the nerve endings in the skin of the 
 foot. 2. Passage of nerve impulses up the afferent fibers 
 to the spinal cord. 3. Reception of the impulse by cells 
 of the gray matter in the cord. 4. Sending back nerve 
 impulses. 5. Along efferent fibers to 6. Muscles which 
 shorten so as to move the foot. 
 
Nervous System. 
 
 43 
 
 Importance of Reflex Action. It is important that we 
 understand the nature of reflex action, for very many of 
 the processes of the body are regulated by it. Not only 
 such motions as winking when anything comes quickly 
 
 Nerve Cells Connected by Interlacing Nerve Network. 
 
 Afferent Nerve Fiber 
 
 Sensory 
 
 Epithelium 
 
 (Skin) 
 
 Efferent Nerve Fiber 
 
 Muscle 
 
 Fig. 28. Parts used in Reflex Action. 
 
 toward the eye, dodging, jumping when suddenly touched 
 by anything hot or when pricked by a pin, but also the 
 regulation of circulation, respiration, and digestion, are 
 brought about through reflex action. 
 
 Destination of Nerve Fibers. The sciatic nerve (the 
 large nerve of the thigh, see Fig. 23) is composed of many 
 fibers. If this nerve is traced outward, it is found to be 
 continually subdividing and sending smaller branches to 
 the muscles, and finally in the muscles one fine nerve fiber 
 goes to each muscle fiber. (See Fig. 13.) Many fibers go 
 on past the muscles to the skin. We can feel in any part 
 of the skin, and we can tell just where we are touched. 
 
44 Physiology. 
 
 These fibers from the skin carry nerve impulses inward, 
 as those going to the muscles carry impulses outward. 
 
 Nerve Roots and their Functions. Observations made 
 on animals, and accidents in the case of man, show that 
 all the fibers of the nerves that carry currents to the mus- 
 cles pass out from the spinal cord into the ventral root, 
 and that all the fibers that carry currents inward enter the 
 spinal cord through the dorsal root. Hence, the dorsal 
 root is often called the afferent root, and the ventral the 
 efferent root. Since ingoing impulses produce sensation, 
 the dorsal root is called the sensory root, while the ventral 
 root, carrying currents outward to produce motion, is called 
 the motor root. 
 
 Effect of Stimulating a Spinal Nerve. Experiments 
 have shown that if, in an uninjured animal, a nerve, or 
 more properly a nerve trunk as the sciatic nerve be 
 stimulated, for instance, by an electric shock, two effects 
 are produced : first, motion in the parts whose muscles are 
 supplied by the nerve ; second, sensation, which is referred 
 to the parts of the skin supplied by the branches of the 
 nerve. This double effect is because both sets of fibers in 
 the nerve have been stimulated, one set carrying currents 
 inward, the other outward. 
 
 Cramp. Cramp is a spasmodic shortening of the mus- 
 cles, attended with pain. 
 
 Tetanus. Tetanus (or locked jaw) is a spasmodic and 
 continuous shortening of the muscles, causing rigidity of 
 the parts they supply. It is due to the disordered and 
 excessive stimulation of the muscles through the nerves. 
 
 Crossing of the Fibers from the Brain to the Spinal 
 Cord. Both the brain and the spinal cord consist of two 
 lateral halves connected by cross fibers. Each half of the 
 
Nervous System. 45 
 
 bfain is connected with the opposite half of the body. 
 This is accomplished by the crossing of the fibers. The 
 fibers that carry nerve impulses outward cross as they 
 leave the brain, at the very beginning of the spinal cord, 
 in the part known as the spinal bulb. The sensations 
 arising from .touching anything with the right hand, there- 
 fore, are in the left half of the brain, and the right half of 
 the brain controls the left hand. 
 
 Nervous System compared to a Telegraph System. 
 It is convenient to compare the nervous system to a tele- 
 graph system. Nerve impulses pass along the nerve fibers 
 as electric currents travel along the wires. The ganglions, 
 which receive and send impulses, are similar to the offices 
 which receive and send out electric currents. But there is 
 one important difference : in telegraphing, the same wire 
 is used, both for sending and receiving messages ; while 
 in the nervous system there are two sets of fibers, one for 
 incoming impulses and another for outgoing impulses. 
 
 Harmony in Muscle Action. In throwing a stone a 
 number of muscles are used. Each muscle shortens under 
 the influence of a nerve impulse started by the brain and 
 brought by a motor nerve. If any muscle shortens too 
 soon, or a little too strongly, the stone goes to one side. 
 In a tune on a piano we know that the right keys must be 
 struck at the right time, and with the proper force. What 
 the player is to the instrument, the brain is to the body. 
 
 Temporary Loss of Muscular Power. It may have hap- 
 pened that after sitting long in one position you attempted to 
 stand, but could not. One leg failed to act at the bidding 
 of your will. When the foot is " asleep " we get little sen- 
 sation from it ; we hardly know whether it is touching the 
 floor. Pressing on it with the other foot causes no pain. 
 
46 Physiology. 
 
 The brain starts the nerve currents, and they run along 
 the nerve as far as the compressed part ; here they stop. 
 On account of external pressure the nerve has temporarily 
 lost its power of conducting nerve currents. They cannot 
 reach the muscles of the leg below. Hence the muscles 
 do not shorten, and we do not rise, no matter how strongly 
 we will to do so. 
 
 Dependence of Nerves and Muscles. But what beside 
 the nerve has been compressed ? What process in the 
 limb has been interfered with by the pressure due to the 
 position in which one has been sitting or lying ? What is 
 the temperature of the benumbed limb ? 
 
 On what are the nerves and muscles so dependent for 
 keeping up their activity ? 
 
 Summary. i . Motions are voluntary or involuntary, but all are 
 under control of the nervous system. 
 
 2. The cerebro-spinal nervous system consists of the brain, the 
 spinal cord, and the spinal nerves. 
 
 3. Each spinal nerve has two roots : the dorsal, which is afferent 
 and sensory ; the ventral, which is efferent and motor. 
 
 4. A ganglion is a nerve center largely composed of nerve cells. 
 
 5. Nerves are made up of nerve fibers. 
 
 6. A nerve fiber consists of the central core (or axis cylinder), 
 which conducts the nerve impulse, the medullary sheath, and, outside, 
 the nerve-fiber sheath. 
 
 7. The spinal cord has in its outer part white nerve fibers ; in its 
 center, gray nerve cells. 
 
 8. These cells are branched, and at least one branch becomes the 
 axis cylinder -of a nerve fiber. 
 
 9. The gray matter of the cord is the center of the reflex action. 
 TO. The nerve fibers from each half of the brain connect with the 
 
 opposite half of the body. 
 
 11. The nervous system is comparable to a telegraph system. 
 Questions. I. Name as many involuntary motions as you know. 
 
 2. What other cases of reflex action do you know ? 
 
 3. Why is a man partially paralyzed when he has broken his back ? 
 
CHAPTER VI. 
 CIRCULATION OF THE BLOOD. 
 
 The Blood and its Work. There is no bleeding when 
 we trim the nails or cut the hair, and the outer skin has 
 no blood in it. But the inner skin, and almost every tissue 
 within it, if pierced even by the finest needle, yields blood. 
 We know that loss of blood causes weakness, and may 
 soon cause death. 
 
 What kind of a substance is blood ? Why is it so 
 essential to life? How does it do its work? 
 
 The Rate of the Heart Beat The heart beats about 
 seventy-two times a minute. In children it beats faster. 
 The rate is increased by exercise, by heat, by food, and by 
 mental excitement. 
 
 The Heart Beat and the Pulse. I. The heart beat may be felt at the 
 left of the breastbone. 
 
 2. The pulse may be felt at the wrist, in the neck beside the wind- 
 pipe, and in various parts of the body. Perhaps the most convenient 
 place to study it is at the -temple. Lay the forefinger lightly along the 
 cheek just in front of the ear. Count the pulsations for a minute. 
 
 3. Let one or two pupils step to the blackboard and put down the 
 number of pulsations of each pupil, and divide by the number thus 
 reporting, to get the average. 
 
 4. Let all count the pulse while sitting. Get the average of the 
 class. 
 
 5. Find the pulse while sitting ; rise quickly, and immediately begin 
 to count the pulse. Compare with the pulse as taken while sitting. 
 
 6. Compare the pulse before and after meals. 
 
 47 
 
48 Physiology. 
 
 The Shape of the Heart. The heart is cone-shaped. 
 But the point or apex is down, and the big end, or base, 
 is up, so when we speak of the base of the heart we mean 
 the upper part, not the lower. 
 
 The Position of the Heart. The base of the heart is 
 in the center of the chest, just back of the breastbone, 
 but the apex points downward and to the left (see Figs. 
 32 and 53). 
 
 To Head and Arms 
 Pre-caval Veinj 
 
 Right Auricle 
 
 Aorta 
 
 Left Ventricle 
 
 Apex 
 Fig. 29. The Heart, from the front. 
 
 The Size of the Heart A person's heart is about the 
 size of his clenched hand. 
 
 The Covering of the Heart. The heart is inclosed in a 
 loose-fitting bag, the pericardium. Within the pericardium 
 and around the heart is a small quantity of liquid, called 
 the pericardia I fluid. 
 
 The External Features of the Heart. The larger part 
 of the heart is made up of ventricles, the auricles being 
 two ear-like flaps at the base, one on each side. There 
 is a deep notch between the auricles and the ventricles. 
 
Circulation of the Blood. 
 
 49 
 
 The line of division between the two ventricles is marked 
 by a groove, which runs obliquely along the front surface. 
 In this groove are blood tubes and usually some fat. (See 
 Figs. 29 and 30.) 
 
 The Internal Structure of the Heart. The two halves 
 of the heart are completely separated from one another by 
 a partition. Each half has valves which, part of the time, 
 separate the cavity of each auricle (at the base) from the 
 cavity of the ventricle (at the apex). 
 
 Aorta 
 Left Pulmonary Artery 
 
 Left Pulmonary Veins 
 Left Auricle 
 
 Pre caval Vein 
 
 Right Pulmonary Artery 
 
 Right Pulmonary Veins 
 
 Post-caval Vein 
 
 Right Auricle 
 
 Fig. 30. The Heart, from behind. 
 
 The Valves of the Heart. Between the auricles and the 
 ventricles are curtain-like valves (see Fig. 33), whose 
 upper edges are attached to the inner surface of the walls 
 at the upper margin of the ventricle. These flaps are 
 somewhat triangular, and have strong, white, tendinous 
 cords extending from their edges and under surfaces to 
 the walls of the ventricle below. In the right half of the 
 heart there are three flaps, and this valve is called the 
 tricuspid valve. In the left side there are two flaps, which, 
 together, make up the mitral valve. In the resting heart 
 
50 Physiology. 
 
 these flaps hang down along the walls of the ventricles so 
 that on opening the heart one would see only a single 
 cavity in each half of the heart. 
 
 The Aur-vent Valves. Since these valves are between 
 the auricles and the ventricles they are often called the 
 auriculo-ventricular valves. Nearly every one knows of the 
 town named Pen Mar on the line dividing Pennsylvania 
 from Maryland. The meaning of the name is clear. And 
 any one can tell wher'e Texarkana must be. So for con- 
 venience we shorten auriculo-ventricular to aur-vent, and 
 when speaking of the aur-vent valves we know, without 
 having to stop and think, that they are between the auricles 
 and ventricles. 
 
 The Semilunar Valves. From the base of the right 
 ventricle arises the pulmonary artery. Within its base, 
 just as it leaves the ventricle, are three pocket-like valves, 
 like " patch-pockets." They are 'in a circle, with their 
 edges touching, and thus surround the opening, with their 
 mouths opening away from the heart. A similar set of 
 valves are within the base of the aorta, which arises from 
 the left ventricle. Both these sets of valves are called 
 semilunar valves. As they are between the ventricles and 
 the arteries they are sometimes called the ventriculo-arterial 
 valves. And this may be shortened to vent-art valves. 
 (See Fig. 33-) 
 
 Dissection of the Heart. No description (or even pictures) can 
 give a clear idea of the heart. A good model will be of some assist- 
 ance. But the heart itself should be examined carefully and then dis- 
 sected. The heart and lungs of a sheep should be obtained (ask the 
 butcher to save the "pluck, 11 i.e. the heart and lungs taken out together). 
 The relations of the heart to the lungs and other organs should first 
 be studied, and then the pericardium opened. Observe the outside of 
 the heart, and then cut the heart open to see the points given in the 
 
Circulation of the Blood. 
 
 5 1 
 
52 Physiology. 
 
 above description. After the heart is severed from the lungs the auri- 
 cles may be cut off; then, by pouring water into the ventricle, the 
 action of the valves between the auricles and the ventricles will be 
 seen. Pressing on the outer surface of the right ventricle will make 
 the water escape through the pulmonary artery. If this be split open, 
 the semilunar valves at its base may be found. 
 
 The Blood Tubes connecting the Heart with Other 
 Organs. The aorta arises from the left ventricle. The 
 pulmonary artery springs from the right ventricle and 
 sends blood to the lungs. The pre-caval and the post-caval 
 veins enter the right auricle. The pulmonary veins, two 
 from each lung, enter the left auricle. (See Figs. 31 and 32.) 
 
 The Aorta. The aorta is the largest artery in the body. 
 .It arises from the base of the left ventricle and runs a 
 short distance toward the head, then it arches over and 
 runs toward the lower part of the body. The bend, above 
 the heart, is called the arch of the aorta. At the arch 
 branches are given off which supply the right and left 
 arms, and the right and left sides of the head. Beyond 
 the arch the aorta passes behind the heart and runs along 
 the backbone and passes through the diaphragm. Just 
 beyond the diaphragm it gives off branches to the liver, 
 stomach, intestine, pancreas, and spleen. It gives a 
 branch to each kidney, and finally divides into two large 
 branches to the lower limbs. Numerous small branches 
 are sent to other organs ; in short, the aorta supplies 
 blood to every organ of the body except the lungs. (See 
 Figs. 29, 30, and 32.) 
 
 The Caval Veins. There are two caval veins, the pre- 
 caval and the post-caval. The pre-caval brings the dark 
 blood from the head and arms. It has four main branches, 
 one from each side of the neck, the jugular veins ; and 
 one from each arm, the subclavian veins. These four 
 
Circulation of the Blood. 
 
 S3 
 
 d External Jugular Vein 
 
 c Internal Jugular Vein 
 
 2 Subclavian Artery 
 ft Subclavian Vein 
 
 Carotid Artery 
 
 i Aorta 
 in Precaval Vein 
 
 iv Postcaval Vein 
 
 r Gastric Artery 
 j Splenic Artery 
 j Hepatic Artery 
 ^ Pancreatic Artery 
 
 ff Renal Veins 
 5 Renal Arteries 
 
 Fig. 32. Distribution of Arteries and Veins. 
 
54 Physiology. 
 
 unite to form the pre-caval vein, which runs downward and 
 enters the right auricle. The post-caval vein begins in the 
 lower part of the abdomen, by the union of the two large 
 veins from the lower limbs. As it runs upward, it receives 
 branches from the kidneys and from the liver; it passes 
 through the diaphragm and enters the right auricle. (See 
 Figs. 29, 30, and 32.) 
 
 The Distribution of the Arteries and Veins. The organs 
 of the body receive a supply of blood in proportion to 
 their size and activity. The artery supplying the blood to 
 any organ and the vein which returns it usually lie side 
 by side (see Fig. 32). The larger arteries are usually 
 deep-seated and in protected places. 
 
 The Action of the Heart The heart consists of muscle 
 fibers so arranged that they form a thick-walled bag, which 
 stands expanded when the muscles relax. But when the 
 fibers shorten, the heart contracts and the blood is forced 
 out. 
 
 The complete action of the heart consists of three parts, 
 the contraction of the auricles, the contraction of the 
 ventricles, and the pause. 
 
 The Pause. During the pause the blood is steadily 
 pouring into the auricles ; into the right auricle from the 
 caval veins, into the left auricle from the pulmonary veins. 
 The aur-vent valves are now open, and their flaps hang loosely 
 beside the walls of the ventricles. The blood, therefore, 
 instead of stopping in the auricles, passes on into the ven- 
 tricles. As the ventricle fills, the aur-vent valves float up, 
 as seen in the experiment of pouring water into the ven- 
 tricle. (See right-hand part of Fig. 33.) 
 
 The Contraction of the Auricle. When the ventricle is 
 full, but not stretched, and the auricle partly full, the auricle 
 
Circulation of the Blood. 
 
 55 
 
 suddenly contracts, thus forcing more blood into the ven- 
 tricle, and distending it. At the same time the aur-vent 
 valves, which were already nearly closed, are tightly closed 
 by the pressure of the blood which is forced up behind 
 them. The flaps of the valves are kept from going up toa 
 far by the tendinous cords and by the muscles to which 
 the cords are attached. 
 
 Auricle 
 
 Fig. 33. Diagram of the Heart, showing the Action of the Valves. 
 
 The Contraction of the Ventricle. Next comes the con- 
 traction of the ventricle, slower, but more powerful than 
 that of the auricle. As the walls of the ventricle are 
 drawn together, they press upon the blood. It cannot go 
 back into the auricles, for the more it presses against the 
 aur-vent valves, the more tightly they are closed. The 
 vent-art (semilunar) valves are closed by back pressure in 
 the aorta and pulmonary artery. But the pressure of the 
 blood in the ventricles is so much greater that the vent-art 
 valves are forced open, and the blood is driven out of the 
 ventricles; from the right ventricle into the pulmonary 
 artery, and from. the left ventricle into the aorta. 
 
 While the ventricles are contracting and forcing their 
 
56 Physiology. 
 
 blood out, the auricles are slowly filling by the steady 
 inflow through the veins. 
 
 Systole and Diastole. The contraction of the heart is 
 called the systole, and its dilation is the diastole. 
 
 Dilation of the Ventricle. As soon as the ventricle has 
 completed its contraction it dilates, and most of the blood 
 that has accumulated in the auricle simply falls into the 
 ventricle. The dilating ventricle makes a slight suction, 
 so the blood is in part drawn into the ventricle. During 
 the remainder of the pause the blood accumulates in the 
 ventricle and auricle till the auricle again contracts and 
 the action is repeated. This is true of both halves of the 
 heart, which work at the same time, the two auricles con- 
 tracting together, and then the two ventricles. The right 
 heart pumps dark blood while the left heart pumps bright 
 blood. The left ventricle is thicker walled and stronger 
 than the right. 
 
 Work and Rest of the Heart. Immediately after the 
 contraction of the auricle comes the contraction of the 
 ventricle. The pause is as long as the contractions of 
 the auricle and ventricle put together. In other words, 
 the heart is resting half the time. It is often said that the 
 heart never rests. Its periods of work and rest are so short 
 and follow each other in such rapid succession that it is 
 hard for us to realize that there is a resting time between 
 each two beats, and that this resting time is as long as the 
 working time. 
 
 Overworking the Heart. During violent exercise the 
 heart is likely to be overworked trying to pump blood 
 enough to supply the overworked muscles. One very 
 important part of training an athlete is to strengthen the 
 
Circulation of the Blood. 57 
 
 heart by regular exercise so it will not tire out in pumping 
 the blood to the muscles during an athletic contest, such as 
 a foot race or boat race. 
 
 The Work of the Auricle. The auricle has three func- 
 tions: (i) to complete the filling of the ventricle; (2) to 
 complete the closing of the aur-vent valves ; (3) to act as a 
 reservoir for the blood entering the auricle while the ven- 
 tricle is contracting, that is, while the aur-vent valves are 
 closed. 
 
 The Work of the Ventricle. The contraction of each 
 ventricle forces the blood around to the ventricle of the 
 other side of the heart. 
 
 The Sounds of the Heart. There are two sounds of the 
 heart : 
 
 1. A short, sharp sound made by the closing of the 
 semilunar valves. 
 
 2. Just preceding this sound a longer, duller sound may 
 be heard during the contraction of the ventricles. This is 
 supposed to be due to the vibrations of the walls of the 
 ventricles and of the aur-vent valves. 
 
 Action of the Large Arteries. The arteries have elastic 
 tissue in their walls. When the blood is forced into them, 
 they are stretched. As soon as the ventricle ceases to con- 
 tract, and sends no more blood into the arteries, they 
 "stretch back." We should not say contract, for it is 
 simply an elastic reaction. As the artery reacts it presses 
 on the blood, and hence the blood tries to escape in every 
 possible way. It cannot go back into the ventricles, for it 
 fills the pockets of the semilunar valves, and closes them 
 with a click. The blood therefore flows along the arteries, 
 through the pulmonary artery to the lungs, and through 
 
 5 PHY 
 
Physiology. 
 
 the aorta and its branches to all the other parts of the 
 body. 
 
 The elastic reaction of the arteries thus helps to make 
 steady the flow of blood, which is jerky as it leaves the 
 heart. 
 
 Variation of the Amount of Blood needed. Each organ 
 requires a supply of blood in proportion to its activity. 
 An actively working organ, like the brain, demands much 
 more blood than does such an inactive organ as a bone. 
 Further, the working tissues, such as the brain and mus- 
 cles, need a great deal more blood while they are at work 
 than when they are resting. An organ needing a large 
 supply of blood all the time might secure this by having a 
 large artery. But how can the supply be regulated so that 
 an organ may receive, now more, now less, according to its 
 needs ? 
 
 Plain Muscle Fibers in the Walls of the Arteries. This 
 is regulated by the medium-sized and small arteries leading 
 
 to the parts. In the walls of these 
 arteries are plain muscle fibers. 
 They are arranged circularly in the 
 walls of the arteries (see Fig. 36). 
 These fibers have, like all muscle 
 fibers, the power of shortening. 
 When they shorten they reduce 
 the size of the artery, and, there- 
 fore, for the time, less blood can 
 flow through it. When the muscle 
 fibers relax, the artery widens, and 
 allows more blood to pass through it. 
 
 Nucleus 
 
 Isolated Fibers 
 
 Fibers Joined 
 
 Fig. 34. Plain Muscle Fibers. 
 
 Illustration of the Action of Muscles in Arterial Walls. To illus- 
 trate the action of the muscles in the walls of an artery, let the water 
 
Circulation of the Blood. 
 
 59 
 
 rim through a hose or large rubber tube. Now. if a row of persons take 
 hold of this tube, the grip of their hands is like that of the muscles. 
 
 Connective Tissue 
 
 Endothelium 
 
 Nucleuses 
 
 Muscle Fiber 
 
 Fig. 35. Plain Muscle Fiber. Separate and in Wall of Artery. 
 
 When the hands tighten their grip, the size of the hole in the tube is 
 made smaller, and less water is allowed to flow through it. When the 
 hands relax, the tube, being elastic, 
 allows more liquid to flow through it. 
 
 Endothelium 
 
 Illustration of a Small Artery. 
 To represent a small artery, take a internd Elastic 
 small, thin-walled rubber tube and 
 wind a red thread around it. Now, if circular Mus- 
 the thread could shorten, it would cl Fibers 
 make the tube smaller. 
 
 The Action of Plain and Striated 
 Muscles Fibers compared. These 
 plain muscle fibers are further like 
 those of the skeletal muscles in that The Outer 
 they are under the control of the Coat 
 nerves, but they are involuntary in . 
 
 their action. We cannot interfere Fig . 36 . coats of a Small Artery, 
 with the action of these muscles, no 
 
 matter how strongly we may will to do so. Without our thinking about 
 it, more blood goes to the muscles of the legs when we walk, more to 
 
6o 
 
 Physiology. 
 
 the brain when we are studying, to the digestive organs after eating, etc. 
 The plain muscle fibers shorten at a much slower rate than the striated 
 
 fibers. They are also slower in relaxing. 
 
 Circulation of Blood in the Web of a 
 Frog's Foot. This is a beautiful sight. 
 Here you may see, under the microscope, 
 the active streams of blood. Small ar- 
 teries divide to form capillaries, and capil- 
 laries unite again to form the small veins. 
 In the narrow capillaries the corpuscles 
 may be seen moving along in single file, 
 with barely width enough to pass through 
 the slender tube. If you see this in the 
 frog's foot, you can understand how the 
 blood flows through all the active tissues 
 of your body. (See Figs. 37 and 39.) 
 
 the Capillaries. The 
 
 Fig. 37. " Capillary Blood Tubes in 
 the Web of a Frog's Foot, under 
 a Low Power of a Microscope." 
 From Hall's " Physiology." 
 
 arteries 
 
 The Blood Flow in 
 
 divide and subdivide, and surface view 
 
 become capillaries, which 
 have connecting branches, 
 forming a close network 
 of tiny thin-walled tubes. 
 These penetrate nearly 
 every tissue of the body. 
 The blood cannot do its full 
 work till it is in the tissues, 
 and to reach the tissues it 
 must soak through the walls 
 of the capillaries. The Fig. 38. 
 work of the heart and ar- 
 teries is to keep a slow and steady flow of blood through 
 the capillaries, that the tissues may be constantly supplied. 
 
 The Veins. The capillaries, after penetrating the tis- 
 sues, unite again to form small veins, which in turn unite 
 to form larger ones, till finally two great veins, the pre- 
 
 Longitudinal Section 
 
 Capillaries, composed of a Single 
 Layer of Cells. 
 
Circulation of the Blood. 
 
 61 
 
 caval from the upper and post-caval from the lower part of 
 the body, return the blood to the heart. The veins, like 
 
 Walls of Capillaries 
 
 Tissues of Web 
 
 Fig. 39. Part of Frog's Web (highly magnified). 
 
 the arteries, are smooth inside and elastic (though less 
 elastic than the arteries). They are thinner-walled than 
 the arteries (see Fig. 40) and collapse when empty, 
 
62 
 
 Physiology. 
 
 Vein 
 
 Artery 
 
 Fig. 40. 
 
 whereas the larger arteries stand open, after they are 
 emptied of blood. There are many cross-branches unit- 
 ing veins, so that if the flow 
 is stopped in one vein, the 
 blood can take a " cross- 
 road" into another large 
 vein. This cross-branching 
 may usually be seen on the 
 Uj^Mp^H back of the hand. 
 
 "\HJfc~ .fliP The Valves in the Veins. 
 
 The only valves in the 
 arteries are those" at the be- 
 
 Cross-section^of Small Artery gi nn j n g o f the aorta and pul- 
 
 monary artery. Ma.ny of the 
 
 veins have similar pocket-like valves though less strong 
 than those of the arteries. They are usually in pairs, but 
 sometimes single or in threes. They all have the mouths 
 of the pockets toward the heart, so that the blood flows 
 freely toward the heart, but is kept from flowing the other 
 way on account of the filling 
 of the valves by the back 
 pressure of the blood. When 
 the blood is flowing through 
 the veins toward the heart, 
 the valves lie against the walls 
 of the veins (see Fig. 41). 
 
 Illustration of Valves in the Veins. 
 
 Make a cloth tube (or take the Open S hut 
 
 lining of a boy's coat sleeve) and Fig . 41 . V aives of the Veins, 
 
 sew three patch-pockets on the in- 
 side, in a circle, z.. with edges touching each other. Make the pockets 
 a little "full." Pour sand, shot, or grain through the sleeve first in 
 one direction and then in the other. This shows how the valves fill 
 and block the passage when there is back pressure of the blood. 
 
Circulation of the Blood. 63 
 
 Evidences of Valves in Our Veins. i. With the forefinger stroke 
 one of the veins on the hand or wrist toward the tips of the fingers. 
 The veins swell out. The blood meets resistance in the valves of the 
 vein. Their location may be determined by their bulging out during 
 the experiment. 
 
 2. Stroke a vein toward the body, and the blood is pushed along 
 without resistance. 
 
 3. Let the left hand hang by the side. Note the large vein along 
 the thumb side of the wrist. Place the tip of the second finger on this 
 vein just above the base of the thumb. Now, while pressing firmly 
 with the tip of the second finger, let the forefinger, with moderate 
 pressure, stroke the vein up the wrist. It may be seen that the blood 
 is pushed on freely, but comes back only part way. It stops where it 
 reaches the valves, filling the vein full to this point, but leaving it col- 
 lapsed beyond, as shown by the groove. Remove the second finger, 
 and the vein immediately fills from the side nearer the tip of the fingers. 
 
 These experiments show that the blood in the veins moves freely 
 toward the body, but cannot flow outward to the extremities. 
 
 Effect of Pressure on the Veins. Since the valves in 
 the veins open toward the heart, any alternating pressure 
 on the veins helps to push the blood on toward the heart. 
 The valves are most numerous in the veins near the sur- 
 face and in the veins of the muscles. The pressure of the 
 muscles during their action (thickening while shortening) 
 produces pressure on the veins ; and as the muscles act 
 for a short time only, and then relax, this alternate com- 
 pression and release aids very much in moving the blood 
 on toward the heart. 
 
 How the Muscles help the Heart. This effect is greater 
 at the time the muscles need the most active circulation ; 
 namely, when they are in action, and are using the most 
 blood. The heart has power enough to pump the blood 
 clear around from each ventricle to the auricle of the other 
 side of the heart ; but this outside aid comes in good play 
 to relieve the heart at a time when it has an unusual 
 
64 Physiology. 
 
 amount of work to do, as when one is using a large num- 
 ber of muscles vigorously. 
 
 " Every active muscle is a throbbing heart, squeezing 
 its blood tubes empty while in motion, and relaxing so 
 as to allow them to fill up anew." 
 
 Rate of Blood Flow in the Arteries and Capillaries. The 
 
 blood flows rapidly in the arteries, slowly in the capillaries. 
 Why is this ? When an artery divides, the two branches 
 taken together are larger than the one artery that divided 
 to form them. Hence as the blood flows on it is continu- 
 ally entering a wider and wider channel ; for if all the cap- 
 illaries fed by the aorta were united they would make a 
 tube several hundred times as large as the aorta. 
 
 The Flow of the Blood compared with the Current of a 
 Stream. If we walk along a stream, we see that the 
 channel keeps changing in width and depth. Where the 
 channel is large, whether from increased width or depth, 
 there the current is slower, but wherever the channel is 
 reduced, the current is more rapid. So the stream in the 
 comparatively narrow artery is swift. In the capillaries, 
 although any single channel is small, these channels all 
 together are wide ; the result is the same whether a river 
 widens out into a single lake, or divides into a great num- 
 ber of channels running past many islands. 
 
 The Flow of Blood in the Veins. When two veins unite, 
 the one vein they form is not quite equal to the sum of the 
 two ; so when the blood gathers in the veins it is really en- 
 tering a narrower channel, and it flows faster. And it 
 keeps gaining in speed till it reaches the heart. 
 
 Flow in Arteries and Veins compared. Although the 
 blood keeps flowing fast as it gets nearer the heart in the 
 
Circulation of the Blood. 
 
 caval veins, it does not go as fast as when it left the heart 
 in the aorta, for there are two caval veins each about as 
 large as the aorta. 
 
 Pulmonary Vein 
 
 Digestive Tube 
 
 Pulmonary Artery 
 
 Lymph Vein 
 
 ~ Right Auricle 
 - Right Ventricle 
 Caval Vein 
 
 Liver 
 
 Fig. 42. Plan of Circulation. (Back View.) 
 
 Rate of Flow in Arteries, Capillaries, and Veins. The 
 blood flows rapidly in the arteries, slower in the veins, and 
 slowest in the capillaries. 
 
 Summary. i. The heart beats about seventy-two times a minute. 
 
 2. The pulse is a wave running along an artery. 
 
 3. The pulse varies with age, health, food, etc. 
 
 4. The heart has two main cavities, one in each half of the heart, and 
 two separate streams are flowing through it. 
 
66 Physiology. 
 
 5. Valves allow the blood to flow through the heart in one direc- 
 tion, but prevent its return. 
 
 6. The heart is a hollow muscle, and by contraction forces the 
 blood out into the arteries. 
 
 7. The heart works about half the time. 
 
 8. The large arteries, by elastic reaction, push the blood on while 
 the heart is resting. 
 
 9. Circular muscle fibers in the walls of the medium-sized arteries 
 regulate the blood supply to the organs. 
 
 10. In the arteries the blood flow is rapid and jerky, in the capillaries 
 slow and steady. 
 
 11. The thin walls of the capillaries allow the liquid part of the 
 blood to soak out and nourish the tissues, and to soak back into the 
 capillaries bearing waste matter. 
 
 12. The veins are thin walled, and collapse when empty, while the 
 arteries are thick walled, and stand open when empty of blood. 
 
 13. Arteries carry blood from the heart, while veins carry it toward 
 the heart. 
 
 14. The veins have valves which allow the blood to pass toward 
 the heart, but not away from it. 
 
 15. Any alternating pressure on the veins aids the blood flow. 
 
 1 6. The blood flow is most rapid in the arteries, slower in the veins, 
 slowest in the capillaries. . 
 
 17. Gravity influences circulation. 
 
 Questions. i . Why do the large arteries lie deep ? 
 
 2. In which direction should the limbs be stroked to aid circulation ? 
 
 3. How does slapping the hands around the body warm the fingers ? 
 
 4. How can a horse or a cow be comfortable with the head down ? 
 
 5. Why are the walls of the left ventricle thicker than those of the 
 right? 
 
 6. Trace a drop of blood from the tip of a finger around the circuit 
 to the same point again. 
 
 7. Does the pulse at the wrist occur at exactly the same time as at 
 the temple ? Or at the same time as the heart-beat ? 
 
CHAPTER VII. 
 CONTROL OF CIRCULATION. 
 
 Circulation controlled by the Nervous System. We 
 know that fear often causes the face to turn pale and that 
 shame makes it red. Certain emotions also 
 quicken or retard the action of the heart. 
 Great grief or joy has caused sudden death 
 by stopping the action of the heart. 
 
 Nervous Control Involuntary. 
 But this control is not volun- 
 tary. The will has nothing di- 
 rectly to do with it. We often wish to keep 
 from getting red in the face when embar- 
 rassed, but cannot prevent it. Neither can 
 we keep from turning pale through fright 
 or pain. We cannot keep the heart from 
 beating faster when we are excited. Instead 
 of being controlled by the brain, circulation 
 is chiefly under the control of a special part 
 of the nervous system, known as the Sym- 
 pathetic Nervous System. 
 
 The Sympathetic Nervous System. The 
 
 sympathetic nervous system consists of two 
 
 rows of ganglions in the body cavity, one p . g 43 Ffont View 
 
 along each side of the spinal column, re- of spinal cord with 
 
 . . i i r i Sympathetic Gancr- 
 
 ceiving branches from the spinal nerves, lions of one side. 
 
 67 
 
Carotid Plexus 
 
 Superior Cervical Ganglion - 
 
 Middle Cervical Ganglion 
 
 Pharyngeal Branches 
 Cardiac Branches 
 
 Deep Cardiac Plexus 
 
 Superficial Catdiac Plexus 
 
 Solar Plexus 
 
 Aortic Plexus 
 
 Lumbar Ganglions 
 
 Fig. 44. Vertical Section of Body, showing Sympathetic Nerves and Ganglions of Right 
 Side and their Connection with the Ce re bro- spinal Nerves. 
 
Control of Circulation. 
 
 Spinal Cord 
 
 Sympathetic 
 Ganglion 
 
 Fig. 45- Ideal Cross-section of the Nervous 
 System. (After Landois and Stirling.) 
 
 and sending branches to the heart and lungs in the chest, 
 and to the liver, stomach, and other organs in the abdomen. 
 In many places these nerves form a thick network called 
 a plexus. One very large plexus on the dorsal surface of 
 the stomach is called the solar plexus. (See Fig. 44.) 
 
 Regulation of the Size of the Arteries. In the last chap- 
 ter we learned that in the walls of the arteries are muscle 
 
 fibers having a ring-like 
 arrangement. When these 
 muscle fibers shorten they 
 make the artery narrower, 
 and less blood can flow 
 through it. When the 
 muscle fibers relax, they 
 lengthen ; the artery be- 
 comes wider, and more 
 blood flows through it. Now these muscle fibers are under 
 the control of the sympathetic nerves. The sympathetic 
 nerves, therefore, regulate the amount of blood that goes 
 to every organ. 
 
 Blushing. The sudden reddening of the face means 
 that more blood is flowing through the skin of the face. 
 The arteries by which blood reaches the face have quickly 
 widened, and this is because the muscle fibers in the walls 
 of the arteries have suddenly relaxed. To go still further 
 back in the explanation, some emotion has started nerve 
 currents which travel along the fibers of the sympathetic 
 nerves and caused the arteries to widen. 
 
 Sudden Pallor. On the other hand, if the muscle fibers 
 in the walls of the arteries suddenly shorten, the face will 
 turn pale, because less blood flows in the skin of the face. 
 Such a change, as before, is due to the nerve currents 
 
7 
 
 Physiology. 
 
 Synnoathetic Nejve Chains 
 
 GRAY \ 
 MATTER *> 
 
 brought by the sympathetic nerves. Of course the face 
 may turn pale as the result of the stopping, or checking, 
 of the action of the heart, as in ordinary fainting. 
 
 Ordinary Changes in Blood Flow. Without going to the 
 extreme of pallor and blushing, the color of the face varies, 
 under the control of the sympathetic nerves. All the or- 
 gans of the body receive now more, now less, blood, accord- 
 ing as they need it. And all this variation in blood supply 
 is regulated by the sympathetic nervous system. 
 
 Effect of Exercise on the Size of the Arteries. When 
 the muscles work, of course they need more blood. To 
 give them more blood the 
 arteries widen. When one 
 is exercising actively, the 
 muscles take so much blood 
 that we should not 
 
 Dorsal Root 
 
 expect the brain or s P mai Nerve 
 the digestive organs Ventral Root 
 to do much work, for there 
 is only a certain amount of 
 blood in the body, Hence if 
 one organ, or set of organs, 
 
 getS more blood, the Other Fig. 46. Relation of Spinal Cord and 
 
 Sympathetic Nervous System. 
 
 organs must, for the time, 
 
 receive less. Therefore we see why we should rest after 
 
 eating, both from muscular as well as from mental work. 
 
 How the Heart is made to Beat Faster. When many 
 large muscles are at work, it is not enough merely to widen 
 the arteries. This would allow more blood to go to them, 
 but would not send them as much as they need. The 
 heart must beat faster, or with more force, or both. And 
 the heart is made to beat faster and stronger by the nerve 
 
 . Ganglion of 
 Dorsal R.oot 
 
 Sympathetic 
 Ganglion 
 
Control of Circulation. 
 
 7 1 
 
 currents that it receives through, the sympathetic nerves. 
 When we exercise actively, the fact that the muscles need 
 more blood is telegraphed both to 
 the heart and to the arteries leading 
 to the muscles of the arteries, and 
 they are regulated accordingly. 
 
 How the Heart is made to Beat 
 Slower. The slowing of the beat of 
 the heart is due to other nerves, not 
 belonging to the sympathetic system. 
 The vagus nerves are a pair 
 of cranial nerves. They arise 
 from the sides of the spinal 
 bulb, at the base of the brain, 
 and, passing downward, give 
 branches to the gullet, stomach, 
 lungs, and heart. The distri- 
 bution of the vagus nerves is 
 shown in Fig. 47. Nerve cur- 
 rents reaching the heart through the 
 vagus nerves make it beat slower, 
 and if the current is strong enough, 
 as in case of a severe blow over the 
 stomach, may, by reflex action, stop 
 the heart. 
 
 Lungs 
 
 Heart 
 
 Liver 
 
 Stomach 
 
 Fig. 47. 
 
 Distribution of Vagus 
 Nerve. 
 
 Influence of Gravity on Circulation. Although the heart 
 pumps the blood around through the body in spite of 
 the force of gravity, yet the circulation is influenced by this 
 force. For instance, a person who has fainted should be 
 laid flat on his back, that the heart may more easily drive 
 blood to the brain. A sore hand feels less pain if held up, 
 as in a sling, than when hanging by the side, and a sprained 
 
72 Physiology. 
 
 ankle does better rested on a chair, as less blood flows to it. 
 Nearly every one has noted the pain following the pressure 
 of blood when a sore hand, or foot, is suddenly lowered. 
 
 Experiments illustrating the Effect of Gravity on Circulation. Let 
 
 the pupils stand. Let one arm hang freely by the side. Hold the other 
 arm straight up as far as the clothing will readily permit. Observe : 
 
 1. The difference in the color of the two hands. 
 
 2. The difference in fullness, both in the feeling of fullness and in 
 the projection of the veins. 
 
 3. The difference in temperature ; place the backs of the hands 
 against the cheeks. 
 
 The position largely regulates the amount of blood in the hand, and 
 the amount of blood regulates the temperature, the size, and the color. 
 
 Clothing and Circulation. No part of the clothing 
 should be tight enough to interfere with the circulation. 
 Such interference is perhaps most frequent in our foot 
 wear. In cold weather tight shoes keep the feet cold 
 and may result in their freezing, while the same thickness 
 of covering, if loose, would be comfortable. Men often 
 wear hats too tight ; this probably leads to baldness. Tight 
 garters sometimes hinder circulation and cause cold feet. 
 
 Congestion. Congestion is an unnatural temporary col- 
 lection of blood in any part or organ. This may be merely 
 for a short time, and no serious harm results from it. But 
 if it is long continued, it may do great harm. 
 
 Inflammation. If the congestion becomes permanent, 
 we call it inflammation. That is, it is a permanent over- 
 supply of blood, which may bring many bad results. 
 There is usually redness, pain, and often swelling. We 
 have all seen such a condition around a boil or a wound. 
 
 Use of Mustard Plaster. Mustard applied to the skin 
 causes irritation. It makes the skin red. This means that 
 more blood is drawn into the skin through the action of 
 
Control of Circulation. 73 
 
 the sympathetic nerves on the muscles in the walls of the 
 arteries. If there is more blood in the skin, there must be 
 less somewhere else at the same time. Now this is what 
 makes a mustard plaster useful. When there is congestion 
 or inflammation in some internal organ, a mustard plaster 
 applied to the outside draws away some of the blood and 
 thus affords relief to the congested part. 
 
 The Hot Foot Bath. When one has a cold, a hot foot 
 bath relaxes the arteries of the feet. This is a good means 
 of drawing the blood away from internal organs, and often 
 saves the person from serious or even fatal results from 
 a bad cold. 
 
 Summary. i. Circulation is controlled by the nervous system. 
 
 2. This control is involuntary. 
 
 3. The sympathetic nervous system consists of two rows of ganglions 
 in the body cavity along each side of the spinal cord. 
 
 4. The sympathetic system regulates the size of the arteries, and by 
 this means regulates the amount of blood going to any organ. 
 
 5. The heart may be made to beat faster through the sympathetic 
 nervous system. This may come through reflex action and be caused 
 by emotions. 
 
 6. The heart may be made to beat slower through the vagus nerves. 
 
 Questions. i. Why do the feet easily get cold while studying? 
 
 2. What makes the hands grow red and puff up after snowballing? 
 
 3. Why does light exercise before retiring make one sleep better? 
 
 4. How does the application of ice, or cold water, relieve headache? 
 
 5. Why should the clothing be changed after getting wet? 
 
 6 PHY 
 
CHAPTER VIII. 
 THE BLOOD AND THE LYMPH. 
 
 The Blood. The blood is composed of a clear liquid, 
 the plasma, and the blood cells, or corpuscles. In a drop 
 of blood under the microscope tne plasma occupies the 
 clear spaces between the corpuscles. The corpuscles 
 make up one third of the bulk of the blood, and the 
 plasma two thirds. 
 
 Microscopic Examination of the Blood. To get a drop of blood 
 from the finger, wind a cord around the finger, beginning at the base, 
 drawing the cord moderately tight, until the last joint is reached. By 
 this time the end of the finger is usually well distended with blood. 
 With a clean needle make a quick, sharp, light puncture near the base 
 of the nail ; this ordinarily brings a drop of blood. Put a very small 
 drop on each of several slides and quickly cover with coverslips. 
 Examine with a high power. 
 
 The Colored Corpuscles. These are often called the 
 red corpuscles. Although in the mass they give the blood 
 a red appearance, when seen singly they are faint yellow- 
 ish red. In shape they are seen to be circular disks, 
 hollowed on each side like a sunken biscuit. These cor- 
 puscles tend to gather side by side, in rolls, like coins. 
 Each colored corpuscle is a cell without a nucleus. 
 
 The Colorless Corpuscles. In the open spaces between 
 the rolls of colored corpuscles may occasionally be found 
 some spherical corpuscles. They are often called the 
 white corpuscles. The colorless corpuscles are very numer- 
 
 74 
 
The Blood and the Lymph. 75 
 
 ous around a wound. They seem to help in repairing 
 tissues. 
 
 White Corpuscles 
 
 HIGHLY MAGNIFIED 
 
 White Corpuscle ... 
 
 Red Corpuscles 
 in Rolls 
 
 MODERATELY MAGNIFIED 
 Fig 48. Red and White Corpuscles of the Blood. 
 
 The Plasma. The plasma consists chiefly of water, 
 having in solution various salts, including common salt; 
 it also contains the nourishing materials for the tissues. 
 These nourishing materials, obtained from the food by 
 digestion, consist chiefly of proteids, fats, and sugar. The 
 plasma also contains waste matters from the working tis- 
 sues on their way out of the body. 
 
 The Color of Blood. The difference in color of a single 
 corpuscle and the blood in the mass may be better under- 
 stood by comparing it with something that we see more 
 frequently. A tumbler of currant jelly has a rich, red 
 
76 Physiology. 
 
 color, but a thin layer of the same jelly, as when one takes 
 a spoonful on a plate, has a pale color, more yellowish. 
 The colorless plasma with the colored bodies in it may be 
 compared to a glass dish filled with cranberries and water. 
 
 Hemoglobin. The coloring matter in the blood, then, 
 is wholly in the colored corpuscles. Examination of these 
 corpuscles shows that their color is due to a substance 
 called hemoglobin. The hemoglobin in the corpuscles is 
 the chief agent in picking up the oxygen from the air in 
 the lungs and carrying it to the tissues in the body. 
 
 The Coagulation of Blood. When the blood escapes 
 from its natural channels it usually changes from a liquid 
 to a jelly-like condition. This is known as coagulation. 
 It is due to the formation of threads of fibrin from the 
 plasma. These threads of fibrin entangle and inclose the 
 corpuscles, and the two constitute the clot. The liquid 
 that afterward separates from the clot is the serum, and 
 differs from the plasma only in the absence of the fibrin, 
 which is exceedingly small in quantity, though of great 
 importance in its action. Coagulation often serves to stop 
 the flow of blood from wounds. 
 
 Fibrin. If freshly drawn blood be stirred rapidly with 
 a little roll of wire screen, there will soon collect on the 
 wires a stringy substance. Thorough washing will soon 
 leave this colorless. It is fibrin. If the stirring has been 
 done thoroughly, the blood will no longer clot, no matter 
 how long it may stand. 
 
 Watching Coagulation. If you have a slight cut on the 
 hand, it will pay to watch the changes in the blood. First 
 it is a red liquid. Then it becomes jelly-like. Then a 
 clear or yellowish liquid comes out ; this is serum. The 
 serum evaporates and the dried clot forms a scab. 
 
The Blood and the Lymph. 77 
 
 Liquid Blood and Coagulated Blood. The following 
 scheme shows the difference between the liquid blood and 
 the coagulated blood : 
 
 Liquid Blood 
 
 Plasma . . f Serum 
 
 Corpuscles 
 
 Clot 
 
 Coagulated Blood. 
 
 " Black-and-blue " Spots. A bruise often breaks some 
 of the capillaries without breaking the skin. Blood escapes 
 into the spaces in the skin or under it. This blood clots, 
 and the dark color shows through the skin. This clotted 
 blood is gradually absorbed and the color disappears. 
 
 Amount of Blood. The blood constitutes about one 
 thirteenth of the weight of the body. In a body weighing 
 one hundred and fifty pounds this would be about six 
 quarts. 
 
 Quantity of Blood in Different Organs. i. One fourth 
 is in the heart and the larger arteries and veins (including 
 those of the lungs). 
 
 2. One fourth in the liver. 
 
 3. One fourth in the skeletal muscles. 
 
 4. One fourth in the other organs. 
 
 The Lymph Spaces. We have seen that the capillaries 
 have very thin walls. Through their walls part of the 
 plasma of the blood soaks out, and is then called lymph. 
 It passes into irregular cavities in the tissue called lymph 
 spaces. Most of these lymph spaces are minute chinks or 
 crevices in the connective tissue of the different parts of 
 the body. 
 
 The Lymph Tubes. Opening out of the lymph spaces 
 are irregular passage-ways called lymph capillaries, and 
 
78 Physiology. 
 
 these lymph capillaries are continuous with larger but 
 still thin-walled lymph tubes, called lymph veins. But, 
 unlike the blood veins, the lymph veins do not gradually 
 increase in size by uniting. They suddenly form a large 
 tube, the receptacle of the chyle, beginning in the upper 
 part of the abdomen. (See Figs. 50 and 81.) 
 
 The Main Lymph Duct. This tube soon narrows and 
 passes through the diaphragm, close to the spinal column, 
 and up along the column near the aorta, and empties into 
 the veins of the neck at the junction of the left jugular 
 and left subclavian veins. This tube is the "thoracic 
 duct," or the main lympJi duct. It has numerous valves, 
 and, like some of the smaller lymph veins, it presents a 
 beaded appearance, due to the filling and bulging out of 
 the valves. In the right side of the neck is a short right 
 lymph duct, which receives lymph from the right side 
 of the head, neck, and thorax, and from the right arm. 
 The lymph tubes, as a whole, are usually called the 
 "lymphatics." (See Figs. 50 and 81.) 
 
 Valves at the Mouth of the Lymph Tubes. There are 
 valves where these lymph ducts empty into the veins which 
 prevent any reflow of liquid into the ducts, but allow the 
 lymph to pass freely into the veins. 
 
 Muscle Fibers in the Walls of the Lymph Tubes. There 
 are plain muscle fibers in the walls of the lymph ducts. 
 
 Lymphatic Glands. In its course the lymph passes 
 through many kernel-like masses, the lymphatic glands. 
 They may be felt in the armpits, in the groins, and some- 
 times in the neck. Lymph contains corpuscles which are 
 considered the same as the colorless blood corpuscles. It 
 
The Blood and the Lymph. 
 
 79 
 
 a 1 
 
 is thought that these corpuscles are formed in the lymphatic 
 glands. In a disease called scrofula the lymphatic glands 
 become swollen. (See Figs. 49 and 81.) 
 
 The Flow of Lymph. The flow of lymph is partly due 
 to the blood pressure in the capillaries, this pressure is 
 caused by the heart. In our bodies the 
 flow of lymph is largely aided by any 
 pressure on the lymph veins; for, on 
 account of the valves, as in the blood 
 veins, any pressure must push the liquid 
 toward the heart. Thus the action of 
 the muscles in the limbs, in the chest, 
 in the abdomen, in the movements of 
 breathing, and in the bending of the 
 body, etc., all help in this flow, which is 
 always very much slower than that in 
 the blood veins. 
 
 Relations of Blood Flow and Lymph 
 Flow. While the blood leaves the left 
 ventricle by one tube, the aorta, it re- 
 turns to the right auricle, not merely 
 by the two caval veins, but a part of 
 the blood (i.e. of the liquid part of it) 
 does not return by blood veins, but hav- 
 ing left the blood system proper through 
 the thin walls of the capillaries, is 
 brought back by the lymph veins, which, 
 however, join the blood veins just before 
 they empty into the heart. There is 
 only one set of distributing tubes, but Fl f u bes of the surface 
 there are two sets of collecting or re- of , th l e Arm - L y m P h 
 
 Glands at a, b, c, and d 
 
 turning tubes. 
 
8o 
 
 Physiology. 
 
 The Lymph. Lymph is a clear liquid. It is more 
 watery than the blood plasma, but contains a share of all 
 
 Left Jugular Vein 
 
 Mouth of 
 
 Lymph Vein . 
 
 Left Subcla- 
 vian Vein 
 
 Right Lymph Vein 
 
 Right Subclavian 
 Vein 
 
 Pre-caval Vein 
 
 Post-caval Vein 
 
 Main Lymph Vein 
 (Thoracic Duct) 
 
 Lymph Capillaries 
 
 - Blood Capillaries 
 
 Fig. 50. Diagram of the Circulation of Blood and Lymph (Back View). 
 
 its nourishing substances. Lymph may be defined as 
 " diluted blood minus red corpuscles" The blood proper 
 never reaches the tissues. 
 
The Blood and the Lymph. 
 
 81 
 
 Lymph 
 
 Capillary 
 
 The Cells of the Body live in Lymph. The cells of the 
 tissues are bathed in the lymph which fills the spaces in 
 the connective tissue (and 
 there is connective tissue in 
 all the organs of the body), 
 as water may fill the spaces 
 left between stones built into 
 a wall. The cells get. all 
 their nourishment from the 
 lymph, and into the lymph 
 they throw all their waste 
 matter. 
 
 Oxygen 
 
 Food 
 
 Muscle 
 Fiber 
 
 Carbon 
 
 Dioxid 
 
 Water 
 
 Other 
 Wastes 
 
 Fig. 51. Relation of Blood and Muscle. 
 (Lymph being Middleman.) 
 
 Importance of Lymph. 
 We can see that the move- 
 ment and renewal of lymph 
 are as necessary as the circu- 
 lation of the blood itself; is, 
 in fact, the most important 
 part of it. 
 
 Lymph Cavities or Serous Cavities. We have noticed 
 the pericardial liquid (page 50). There is also a small 
 quantity of similar liquid around the lungs in the pleural 
 cavities, and in the abdominal cavity, around the digestive 
 organs; also in the cavities of the brain. The liquid in 
 each case is lymph, and these cavities, often called serous 
 cavities, are lymph cavities. They communicate with the 
 lymph tubes. 
 
 Dropsy. In health the amount of the liquid in these 
 cavities is small, but in certain disorders it may accumu- 
 late. In general, such affections are called "dropsy." 
 The lymph may also accumulate in the tissues of the 
 extremities, causing swelling of the limbs called "dropsy/ 5 
 
82 Physiology. 
 
 Hypodermic In jections. When it is desirable that a 
 medicine act on the body very quickly, it is sometimes 
 introduced under the skin. This is done by means of a 
 hypodermic syringe, which is a syringe with a slender, 
 needle-shaped nozzle. By means of this the medicine is 
 injected into the tissues under the skin. Here it is taken 
 up by the lymph and is quickly carried through the system 
 and acts on the cells of the body. If the same medicine 
 were taken into the stomach, it would require some time 
 for it to be absorbed and carried into the tissues. Hence 
 time is gained. We can see how much advantage there is 
 in this way of giving medicine when the physician wishes 
 to stop severe pain. 
 
 The Spleen. The spleen is a flattish red body at the 
 left end of the stomach. There is an active circulation of 
 blood in it, and it is supposed to form the colored blood 
 corpuscles. It is often called a blood gland. 
 
 Summary. i . The blood consists of a liquid, the plasma, in which 
 float the colored and colorless corpuscles. 
 
 2. The color of blood is given by a substance, called hemoglobin, in 
 the colored corpuscles. 
 
 3. When blood is shed it coagulates, tending to check its own 
 escape. 
 
 4. Lymph is like the blood diluted and lacking the colored cor- 
 puscles. 
 
 5. A set of lymph tubes conveys the lymph into the veins to join 
 the flow toward the heart. 
 
 6. In its course the lymph passes through the lymphatic glands. 
 
 Questions. i. What is blood poisoning ? 
 
 2. Which is heavier, blood or water ? 
 
 3. Does it help a sick person to bleed him ? 
 
 4. What is meant by good blood ? Bad blood ? 
 
 5. What is meant by good humored ? Bad humored ? 
 
 6. Does the blood remain the same from day to day ? Or even from 
 hour to hour ? 
 
CHAPTER IX. 
 EXTERNAL RESPIRATION. 
 
 The Close Relation between Circulation and Respiration. 
 Is it not a very striking fact that we breathe once for 
 every four heart beats ? And that whatever quickens the 
 breathing also quickens the heart so that the two always 
 
 keep in almost the 
 same ratio? Let us 
 try to learn why this 
 is so. 
 
 The Organs of Res- 
 piration. i. The 
 
 lungs and air tubes. 
 2. The organs which 
 increase and dimin- 
 ish the size of the 
 chest, chief among 
 which are the dia- 
 phragm and the mus- 
 cles acting on the 
 ribs. 
 
 External Features 
 of the Lungs. The lungs are of a pinkish color; they are 
 very elastic, soft, smooth, and moist. 
 
 The Air Tubes. The windpipe, or trachea, has in its 
 walls rings of gristle or cartilage, which keep the tube 
 always open. These rings of cartilage are not complete 
 
 83 
 
 Fig. 52- The Trachea and Bronchial Tubes, showing 
 Two Clusters of Air Sacs. 
 
Physiology, 
 
 1. Pulmonary Orifice 3. Left Auriculo- Ventricular Orifice 
 
 2. Aortic Orifice- 4. Right Auriculo-Ventricular Orifice 
 
 The heavy black line between the heart and the liver represents the diaphragm. 
 
 Fig. 53. Front View of the Thorax. The Ribs and Breastbone are represented in 
 Relation to the Lungs, Heart, and other Internal Organs. 
 
External Respiration. 85 
 
 rings, but are C-shaped. As the windpipe branches (bron- 
 chi) into the two lungs, the cartilages continue in the 
 smaller branches which extend into every part of the lungs. 
 
 The Internal Structure of the Lungs. The lungs are 
 full of small cavities, like a loaf of light bread. The small 
 cavities are called air sacs or air vesicles, and each air sac 
 communicates with the end of one of the branches of an 
 air tube, through which air comes into and goes out of 
 every air sac. The air sacs are very thin walled, and 
 around the sacs are networks of the fine blood tubes called 
 capillaries. 
 
 Elastic Tissue in the Lungs. The air sacs and air tubes 
 and their surrounding blood tubes are bound together by 
 elastic tissue, which fills up most of the space between them. 
 
 The Mucous Membrane. The lining of the trachea is 
 a mucous membrane. It pours out on its surface a sub- 
 stance somewhat 
 like white of egg, 
 
 M . lj| HKHji 'mm called mucus. This 
 
 N^ZJP keeps the air moist, 
 
 and catches parti- 
 cles of dust that are 
 in the inspired air. 
 Flg ' 54 ' Cillaled There is a constant 
 
 slow current of mucus toward the throat, whence it is, from 
 time to time, hawked up. 
 
 Ciiiums. This current of mucus is caused by the ciii- 
 ums projecting from the lining cells of the trachea. They 
 are little hairlike projections, in countless numbers, like a 
 field of grass, each cilium having the power of bending 
 back and forth, making a quick stroke toward the throat, 
 then a slower recover stroke. Thus the united wavelike 
 
86 
 
 Physiology. 
 
 action of the myriads of lashing ciliums paddles the mucus 
 headward. 
 
 The Pleura. The outside of each lung is covered by a 
 thin membrane, the pleura, which completely surrounds it, 
 except at the root of the lung, where the bronchus and 
 blood tubes enter. Here the pleura turns toward and 
 becomes attached to the inner wall of the chest, forming 
 its lining (still called the pleura), and below passes over 
 
 Trachea 
 
 Pleural Space ,._ 
 (Exaggerated) 
 
 Chest Wall 
 
 Pleura 
 
 Fig. 55. Diagram of the Lungs and Pleuras. 
 
 the upper surface of the diaphragm. The lung is thus 
 free, except at its root, where the air and blood tubes 
 enter. A very small quantity of liquid moistens the sur- 
 faces of the pleuras on the outside of the lung and the 
 inside of the chest wall, so they move easily one upon the 
 other during respiration. As the lungs are always dis- 
 tended enough to fill the chest cavity, these two surfaces 
 are always in contact. 
 
 Pleurisy. Pleurisy is an inflammation of the pleura. 
 In breathing there is pain from friction or adhesion of the. 
 pleuras of the lungs and chest wall. 
 
External Respiration. 
 
 Pneumonia. Pneumonia is inflammation of the lungs. 
 It was formerly called ''lung fever." It is due to bacteria. 
 
 The Diaphragm. The diaphragm is a thin muscle mak- 
 ing a complete partition between the abdominal cavity and 
 the chest cavity. It is convex above and concave below 
 where it fits over the liver and stomach. Its front edge is 
 attached to the inside of the chest wall about opposite the 
 lower end of the breastbone. Its general position is shown 
 in Figs. 53, 55, and 58. 
 
 Triangularis Sterni 
 Internal Mammary Vessels 
 
 Left Phrenic 
 Nerve 
 
 Pleura 
 
 Pulmonalis 
 
 ura Costalis 
 
 Mediastinum j Sympathetic Nerve 
 
 Thoracic Duct 
 
 Vena Azygos Majo' 
 
 Posterior 
 
 <_ Thoracic Duct . Pneumogastric Nerves 
 
 Fig. 56. A Cross-section of the Chest, showing the Heart. Lungs, and Blood Tubes. 
 
 To show the Action of the Diaphragm and Lungs. MATERIAL. 
 Bell jar with stopper, sheet of rubber (such as used by dentists) large 
 
88 Physiology. 
 
 enough to covel the mouth of the jar, toy rubber balloon, cork (rubber 
 preferred), glass tube, cotton string, collar button. 
 
 PREPARATION. Lay the collar button on the center of the sheet of 
 rubber, double the rubber over it, stretching the rubber strongly over 
 the head of the button, and tie the head firmly in its place. Stretch 
 the sheet of rubber over the base of the jar with the base of the 
 button on the outside, and fasten with string. Bore a hole in the cork, 
 and fix the glass tube snugly in it, so that the lower end of the tube 
 will extend about half-way down the jar. Tie the balloon on the lower 
 end of the glass tube. 
 
 CILIA I LBRONCHIAL TUBE. 
 
 \ 
 
 Fig- 57. Minute Structure of the Lungs, showing Air Sacs and Capillaries. 
 
 EXPERIMENT i. Insert the balloon and tube into the jar, inflate 
 the balloon, and while it is inflated tightly cork the jar. If all the parts 
 fit well, the balloon should now remain inflated, and the rubber which 
 represents the diaphragm will be arched upward. 
 
 EXPERIMENT 2. Pull the diaphragm down, using the base of the 
 collar button as a handle. This shows the expansion of the lung by 
 the pressure of the external air when more space is given by the 
 depression of the diaphragm. On releasing the diaphragm, it springs 
 upward, and the balloon becomes smaller, driving out part of the air 
 that was in it. This shows how expiration is accomplished, so far as 
 the diaphragm is concerned. 
 
 If a bell jar is not at hand, a lamp chimney or a quart bottle may be 
 used, after cutting off the bottom, as follows : File a deep notch across 
 
External Respiration. 
 
 8 9 
 
 near the bottom ; heat an iron rod, and apply the end of it to one end 
 of the notch, and slowly draw the rod around to the other end of the 
 notch (the rod may need to be reheated). After cracking off the 
 bottom of the jar, file the edges so they will not cut the rubber. 
 
 Let each pupil make a drawing, showing the position of the parts in 
 inspiration and in expiration. 
 
 The Movements of Respiration. The process of res- 
 piration consists of two acts, inspiration and expiration. 
 
 . . . . Increased Air 
 Space 
 
 Inspiration Expiration 
 
 Fig. 58- Sections of the Body in Inspiration and Expiration. 
 
 Two Active Forces in Inspiration. In inspiration the 
 principal active forces in the body are, first, the dia- 
 phragm ; and, second, the muscles which raise the ribs. 
 
 Work of the Diaphragm in Inspiration. The diaphragm 
 is a muscle, and when its fibers shorten, the diaphragm is 
 pulled down. In moving down it presses on the abdomi- 
 nal organs, and makes the abdomen protrude forward and 
 sideways. This lowering of the diaphragm increases the 
 7 PHY 
 
90 Physiology,, 
 
 space in the chest. Air, from the outside, enters through 
 the trachea, presses on the inside of the elastic lungs, and 
 makes their bases extend, following the diaphragm in its 
 descent. The bases of the lungs remain in contact with 
 the upper surface of the diaphragm all the time. 
 
 Work of the Chest Walls in Inspiration. Certain 
 muscles of the chest wall raise the ribs and breastbone. 
 This widens the chest, and the air, as before, presses in 
 through the open windpipe, and keeps. the sides of the 
 lungs in contact with the inner surfaces of the chest walls. 
 
 Effort required in Depressing the Diaphragm. Inspira- 
 tion requires considerable effort, because the diaphragm 
 in its descent presses upon the elastic organs of the 
 abdomen (stomach, liver, etc.), and these organs, in turn, 
 are pressed against the elastic walls of the abdomen. It is 
 somewhat like pressing a pillow down into a rubber bag; 
 the pillow springs up as soon as the pressure is stopped, 
 because of its own elasticity as well as that of the bag. 
 Therefore, as soon as the diaphragm relaxes, the elastic 
 walls of the abdomen retreat, and the abdominal organs 
 rise to their former place. 
 
 Effort required in Raising the Ribs. When the ribs are 
 elevated, the cartilages which connect the front ends of the 
 bony parts 'of the ribs with the breastbone (see Fig. 6) are 
 slightly bent. When the muscles relax, the elasticity of 
 the rib cartilages makes the ribs spring back to their 
 former position, thus reducing the chest to its former 
 width. 
 
 Expiration Easy. Thus we see why expiration is easy; 
 in fact, "does itself" (in ordinary respiration) by elastic 
 reactions. But inspiration is harder than it would be if it 
 
External Respiration. 9 1 
 
 were not for the fact that the descent of the diaphragm 
 meets resistance, and the ribs, in rising, have to overcome 
 resistance in bending the rib cartilages, and in raising the 
 weight of the chest walls and shoulders. 
 
 Potential Energy stored in a Door Spring. When one 
 opens a door that has a spring to shut it, he has to use 
 more force to open the door than he would if he did not 
 have to bend (twist or compress) the spring at the same 
 time. But no effort is needed to shut the door. The door 
 was opened and shut at the same time ; i.e. when the door 
 was opened, force was stored in the spring (in the form of 
 what is called potential energy), and this stored energy 
 shuts the door while we pass on. We can better afford to 
 expend more energy while opening the door than to take 
 the extra time to shut it. If, then, a door with such spring 
 were fastened open, it might remain open for a long time. 
 When released it flies shut. If one, in this case, asks, 
 " Who shut the door ? " the answer is, " The person who 
 opened it." 
 
 The Storing of Energy during Inspiration. So in the 
 act of inspiration we perform a double work in storing 
 energy by which the expiration is performed without active 
 muscular effort. 
 
 Review of Forces of Respiration : 
 Forces of Inspiration. 
 
 1 . Depression of the diaphragm. 
 
 2. Muscles elevating the ribs. 
 
 3. Pressure of the external air. 
 
 Resistances to . Inspiration . 
 
 l . Compression of the abdominal organs and stretching abdominal 
 walls. 
 
92 Physiology. 
 
 2. Bending the rib cartilages and lifting the chest. 
 
 3. Stretching the lungs. 
 
 Elastic Reactions of Expiration. 
 
 1 . Elastic reaction of the abdominal walls and contents, 
 
 2. Elastic reaction of the rib cartilages. 
 
 3. Elastic reaction of the lungs. 
 
 Forced Respiration. Thus far we have been speaking 
 of ordinary respiration. In forced respiration, as in shout- 
 ing, many muscles are brought into play to expel the air 
 rapidly and forcibly. In such an act as coughing there is 
 vigorous action of the abdominal muscles. 
 
 Abdominal and Thoracic Respiration. The main part of 
 respiration is performed by the diaphragm, and is there- 
 fore called diaphragmatic or abdominal breathing. Breath- 
 ing by means of the chest walls is called thoracic, or costal 
 breathing. 
 
 The Rate of Respiration. Adults breathe about seven- 
 teen or eighteen times a minute, or about one breath to 
 four heart beats. The rate is increased by exercise, tem- 
 perature, digestion, excitement, age, etc. 
 
 Special Forms of Breathing. Coughing is a forcible 
 expiration, usually directed through the mouth, and for the 
 purpose of getting rid of some irritating substance. In 
 sneezing there is first a deep inspiration, and then the air 
 is forced out, chiefly through the nose. Sneezing may be 
 prevented by pressing firmly on the upper lip. Hiccuping 
 is sudden inspiration, produced by a jerky action of the 
 diaphragm, accompanied by a sudden closing of the en- 
 trance to the windpipe. In case of choking it is well to 
 hold the head well forward, and perhaps downward. A 
 smart slap between the shoulders sometimes helps dislodge 
 
External Respiration. 93 
 
 anything stuck in the throat, and it may be necessary to 
 hold a child with the head downward. There are various 
 
 5 
 
 * 
 
 tl 
 
 COMPLEMENTAL AIR. 
 
 120 CUBIC INCHES. 
 AIR THAT CAN BE BUT SELDOM IS TAKEN IN. 
 
 TIDAL AIR. 20 to 30 Cubic Inches Air Taken in 
 and Sent out at Each Breath. 
 
 RESERVE AIR. 
 
 100 CUBIC INCHES. 
 AIR THAT CAN BE BUT IS SELDOM DRIVEN OUT. 
 
 RESIDUAL AIR. 
 
 100 CUBIC INCHES. 
 AIR THAT CANNOT BE DRIVEN OUT. 
 
 Fig. 59. Diagram of Lung Capacity. 
 
 I 
 
 s. 
 o 
 
 other peculiar forms of respiration, such as yawning, sniff- 
 ing, laughing, etc., which you can explain after watching 
 and thinking about them. 
 
94 Physiology. 
 
 Capacity of the Lungs. Have the class stand, and each 
 pupil raise his right hand. 
 
 1 . Tidal Air. Let all breathe together, at the ordinary rate and 
 depth, and let the hand rise about three inches during inspiration, and 
 fall again during expiration. The amount of air taken in at an ordinary 
 breath is from 20 to 30 cubic inches, or about a pint. This is called 
 tidal air. 
 
 2. Complemental Air. As before, let the hand go up and down 
 with the breathing, but at the end of the third inspiration, instead of 
 stopping with the usual amount, keep on breathing in as much as pos- 
 sible, letting the hand rise accordingly. This air that can be taken in 
 above the ordinary breath is called the complemental air, and it is 
 estimated to be, on the average, about 120 cubic inches. 
 
 3. Reserve Air. Begin as before, and at what would be the end 
 of the third expiration continue to drive out as much air as possible, 
 indicating the degree by lowering the hand. This air that can be 
 breathed out beyond the ordinary expiration is called the reserve air, 
 and is reckoned at about 100 cubic inches. 
 
 4. Residual Air. The air cannot all be breathed out. The re- 
 mainder is called the residual air, and is computed to be about 100 
 cubic inches. 
 
 The Vital Capacity. All the air that can be breathed out after a 
 full inspiration, i.e. the sum of the complemental, tidal, and reserve 
 air, would be about 240 to 250 cubic inches, and is called the vital 
 capacity. Of course these figures represent only the average of cer- 
 tain experiments and observations. By practice any one can consid- 
 erably increase his vital capacity. 
 
 A Test of the Capacity of the Lungs. A simple method of measur- 
 ing these stages of respiratidn is to take a gallon bottle and first care- 
 ' fully graduate it to pints by pouring in water and marking on the 
 outside with a file. Then fill the bottle with water, invert it in a trough 
 of water, and exhale into it by means of a rubber tube. 
 
 Hygiene of Breathing. Those persons who take con- 
 stant exercise in the open air are not likely to suffer much 
 from deficient respiration. But persons who lead an indoor 
 
External Respiration. 95 
 
 life, especially those who are sitting much of the time, need 
 to pay especial attention to the matter. 
 
 The Nasal Passages. The nasal passages are fitted for 
 the introduction of the air (i) by being narrow, but of 
 large area; (2) by having their lining membranes richly 
 supplied with blood ; (3) by the abundant secretion of 
 mucus by this membrane. The air, coming through this 
 narrow channel, is warmed, and a large part of any dust 
 it may contain is caught by the sticky mucus that covers 
 all the walls of this passage-way. 
 
 Adenoids. When any person breathes through the 
 mouth, there is something wrong somewhere in the nasal 
 passages. Children who breathe through the mouth and 
 " snore " at night generally have a growth of gland-like 
 tissue called " adenoids " at the back part of the nose and 
 behind the palate. Not only is breathing through the 
 mouth bad because it allows cold air and dust to go down 
 into the windpipe, but the mouth breather cannot get 
 enough air properly to aerate his blood. Mouth-breathing 
 children, therefore, are frequently peevish and not dis- 
 posed to play. They do not sleep or eat well, are apt to 
 be croupy, and are more liable than nose-breathing chil- 
 dren to contract diseases like diphtheria and croup. Such 
 children should be taken to the doctor and the adenoids 
 should be removed. 
 
 Deep Breathing. It is a grateful relief to the whole 
 system to stand, stretch, inhale deeply and slowly several 
 times, and to repeat this every hour or so. Every one 
 engaged in office work or studying should form this habit, 
 especially if he does not give an hour daily to exercise. 
 
 Control of Respiration. Breathing is an involuntary 
 action. It is under the control of the nervous system, and, 
 
96 Physiology. 
 
 without attention on our part, it goes on, varying in rate 
 according to the needs of the body. About every fifth 
 breath is a little deeper than the others, and if we are sit- 
 ting in a cramped position, or are depressed, this occasional 
 deeper breath is still more marked and is called a sigh. 
 If the tissues are not well supplied with oxygen, they make 
 it known to nerve centers through the nerves, and, by 
 reflex action, breathing is quickened. 
 
 Summary. I. In the lungs the air and blood are brought very close 
 together, only the wall of the capillary and that of the air vesicle being 
 between them. 
 
 2. Through these two layers oxygen passes from the air sac into the 
 blood. Carbon dioxid, water vapor, and other wastes pass from the 
 blood into the air sac. 
 
 3. The mucous membrane of the air passages secretes mucus which 
 is driven toward the nostrils by the ciliums. 
 
 4. The chest is lengthened by the lowering of the diaphragm, and 
 widened by the lifting of the ribs, giving greater space, which is filled 
 by external air expanding the lungs. 
 
 5. Inspiration requires extra effort ; but ordinary expiration is with- 
 out effort because of the elastic reactions. 
 
 6. Forced expiration, as coughing, requires active muscular effort. 
 
 7. The vital capacity may be increased by practice and by exercise. 
 
 8. We should breathe through the nose, not through the mouth. 
 
 9. Respiration is under the control of the nervous system. 
 
 Questions. i. Is 5t well to see how long one can hold his breath ? 
 
 2. Should the head be covered by bedclothes ? 
 
 3. How is respiration affected by a stooping posture ? 
 
 4. What are the "lights" of an animal ? 
 
 5. Of what advantage is it that the cartilages of the windpipe are 
 C-shaped, and not complete rings ? 
 
 6. From the statements in this chapter of the amount of air taken in 
 at each breath and of the rate of breathing, find out how much air is 
 breathed in an hour. How much in twenty-four hours ? 
 
CHAPTER X. 
 INTERNAL RESPIRATION. 
 
 Composition of the Air. Air has about 20 per cent oxy- 
 gen and 80 per cent nitrogen, or one fifth oxygen and four 
 fifths nitrogen. There 'is a very small amount of carbon 
 dioxid, .and usually there are traces of other gases. 
 
 Experiments illustrating Internal Respiration. MATERIAL NECES- 
 SARY. A piece of candle an inch or two long, two tumblers, a tube 
 eight inches long (a straw will serve), a nail, and lime water. The lime 
 water should be prepared the day before by putting a piece of fresh 
 quicklime as big as a hen's egg in a quart of water. The next morning 
 carefully pour off the clear water for use in experiment. 
 
 EXPERIMENT i. Light the candle and hold a cold tumbler inverted 
 a little above it. The moisture that dims the inside of the tumbler is 
 water that has been produced by the burning of the candle. The oxy- 
 gen of the air unites with something in the candle and forms water. 
 
 EXPERIMENT 2. Breathe into a cold tumbler. The tumbler is 
 dimmed by the water in the air we breathe out. 
 
 EXPERIMENT 3. Lower a tumbler over the burning candle till the 
 tumbler rests on the table. Observe that the flame is soon put out. 
 Carefully lift the tumbler and slip one hand under it so that the palm 
 tightly covers the mouth of the tumbler. Invert the tumbler. Lift one 
 edge of the hand and pour in about two tablespoonfuls of lime water. 
 Thoroughly shake the tumbler, keeping it tightly closed. The lime 
 water is turned milky by the carbon dioxid produced by the burning 
 candle. There is carbon in the material of the candle, and the union of 
 oxygen with this carbon produces carbon dioxid. 
 
 EXPERIMENT 4. Pour about two tablespoonfuls of lime water into 
 a tumbler and breathe through it by means of a tube. The lime water 
 is turned milky by the carbon dioxid in the breath. There is carbon in 
 
 97 
 
98 Physiology, 
 
 the tissues of the body. Oxygen unites with this carbon, forming car- 
 bon dioxid. We know that there is carbon in beef, for when it is over- 
 baked we see the black carbon where it is charred. There is carbon in 
 our muscles and in all the other tissues. 
 
 EXPERIMENT 5. Place a nail, or any piece of iron, in a tumbler of 
 water. It will soon rust. Rusting is caused by the union of oxygen 
 with the iron. When anything unites with oxygen it is said to oxidize. 
 When the union is rapid, as with the burning candle, it is called com- 
 bustion. 
 
 EXPERIMENT 6. Hold a thermometer at arm's length. It shows 
 the temperature of the air, of the air you are breathing in. Breathe 
 for a few minutes upon the bulb of the thermometer and you have proof 
 that the air we breathe out is warmer than the air we breathe in. 
 
 How the Body is like a Candle. The burning candle 
 and the body both produce heat. To do this each must 
 have oxygen. The oxygen unites with carbon and other 
 elements in each, and produces carbon dioxid, water, and 
 .other substances. And just as a candle flame is soon put 
 out in a closed tumbler, so life would be destroyed by suf- 
 focation if an animal were shut in an air-tight room. 
 
 Exchanges between the Air and the Blood in the Lungs. 
 
 Whatever the air coming from the lungs contains that was 
 not in the air entering them it has taken from the blood, 
 and what the air has lost it has given to the blood. The 
 air in the air vesicle is separated from the blood in the 
 pulmonary capillaries only by the thin wall of the air vesicle 
 and the thin capillary wall. 
 
 What the Air gets from the Blood. Carbon dioxid, water, 
 and other waste matters pass from the blood through this 
 thin partition into the air vesicle, to be sent out by later 
 expiration through the bronchial tubes and windpipe. The 
 air also gets heat from the blood (see Fig. 60). 
 
Internal Respiration. 
 
 99 
 
 What the Blood gets from the Air. Oxygen from the air 
 in the vesicle passes through these layers into the plasma, 
 and most of it is quickly picked up by the colored corpus- 
 cles. The colored corpuscles are the carriers of oxygen. 
 
 BRONCHIAL TUBE 
 
 FROM PULMONARY ARTERY 
 
 TO PULMONARY VEIN 
 
 Fig. 60. Exchanges between the Air and the Blood in the Lungs. 
 
 Hemoglobin and Oxy-hemoglobin. The hemoglobin in 
 the colored corpuscles is eager to unite with oxygen. 
 Hemoglobin is of a dark color, and gives the dark color 
 to the blood which enters the lungs. When oxygen unites 
 with the hemoglobin it forms oxy-hemoglobin, which is of a 
 bright red color. Hence the change in the color of the blood 
 
100 
 
 Physiology. 
 
 in the lungs from a dark bluish red to a bright scarlet 
 This bright blood is usually called " arterial," and the dark 
 "venous"; but it must be remembered that the blood in 
 the pulmonary artery is dark, and in the pulmonary veins 
 bright. 
 
 "V 
 
 v \ 
 
 Fig. 61. Circulation in the Capillaries of the Lungs and in the Capillaries of the Body. 
 
 The Changes in the Blood. What does the blood do 
 with the oxygen that it gets in the lungs, and where did it 
 get the carbon dioxid and other impurities that it brings to 
 the lungs ? Let us follow the blood and see. From the 
 pulmonary veins the blood goes to the left heart, and is 
 pumped to all the tissues except the lungs. Let us follow 
 a branch of the aorta that leads to a muscle. 
 
 The Production of Heat and Motion in the Body. When 
 a muscle works it becomes warmer. The rise in tempera- 
 ture has been repeatedly proved by experiment. We know 
 that the blood is flowing more rapidly through the muscle 
 
Internal Respiration^. 
 
 when it is at work. The more rapid stream brings the 
 muscle more oxygen. This it needs, for it is by the oxida- 
 tion of the muscle (or substance in it) that the muscle 
 produces heat and motion. The oxidation in our tissues is 
 a slow oxidation, more like the rusting of iron than the 
 burning of a candle. Oxidation in our bodies never pro- 
 duces a high degree of heat and never produces light. 
 
 Increased Blood Flow is the Result of Exercise. When 
 we exercise, the muscles need more oxygen. They also 
 need to have removed the waste matters that they are so 
 rapidly producing at this time. How is the oxygen brought 
 and the waste removed ? By the blood, you answer. True ; 
 but what makes the blood come and go faster at this time ? 
 By reflex action, you reply. The muscles send a message 
 to a nerve center, and this nerve center sends back a mes- 
 sage to the blood tubes, making them widen, and the heart 
 also may be made to beat faster. 
 
 Increased Respiration from Exercise. But would it do 
 any good to have the blood flow through the muscles faster, 
 if it could not bring more oxygen, and take away and get 
 rid of more wastes ? You will say no. To give the extra 
 oxygen and take out the carbon dioxid, the lungs cannot, 
 of themselves, take in and send out air. The work of 
 pumping air depends on the muscles of respiration, the 
 diaphragm, and the muscles that elevate the ribs. These 
 muscles will not work faster unless they are ordered to do 
 so. A message must be sent to them telling of the need. 
 Thus, by a series of reflex actions, all these processes are 
 kept in close relation to each other. It must be borne in 
 mind that increased blood flow is the result, and not the 
 cause, of the increased activity of the tissues. 
 
 Temperature of the Body. Insert the bulb of a thermometer into 
 the mouth, and keep it there three or four minutes to find the tempera- 
 
IQ2^ physiology. 
 
 ture of the inside of the body. For this it is better to use a clinical 
 thermometer, if one can be obtained. The average temperature of the 
 tissues within the body is about 98.5 F. 
 
 How the Body is like a Stove. The body may be com- 
 pared to a stove. Into one we put fuel and produce heat. 
 In the other we get heat from food. Both take in oxygen. 
 Both produce carbon dioxid, water, and other waste matter. 
 
 How the Body differs from a Stove. But the body is not 
 like the stove in burning the fuel (food) directly. The 
 food is first made into tissues, or material stored in the 
 tissues. It is as though we were to build a stove entirely 
 of coal, and then start a fire in it. In that case it would 
 produce heat not merely by burning in one place within, 
 but would be burning throughout the whole of its sub- 
 stance. This is the case with the body. 
 
 Oxidation in Tissue the Source of Heat in the Body. 
 
 The muscles make up nearly half of the weight of the 
 body. They are more active than most of the tissues. 
 We would naturally infer, as is the fact, that they are the 
 chief source of the heat produced in our bodies. The 
 tissues of the body are oxidizing all the time. But when 
 in vigorous action they oxidize very much more rapidly. 
 
 Production of Heat in the Liver. Next to the muscles, 
 in importance as a heat producer, is the liver, which is the 
 largest gland in the body, and, as we shall soon see, one of 
 the most active. The blood, as it leaves the liver by the 
 hepatic vein, is hotter than anywhere else in the body. 
 
 How the Body is like a Locomotive. But it will be better 
 to compare the body to a locomotive, as we produce not 
 only heat, but motion: I. Both are warm; 2. Both 
 move; 3. Both use fuel (food or coal); 4. Both take in 
 
Internal Respiration. 103 
 
 air. 5. Both give off gases, consisting mainly of carbon 
 dioxid and water vapor. 
 
 How the Body differs from a Locomotive : i. The body 
 does not get hot enough to burn; i.e. the oxidation is 
 relatively slow, and is not combustion. 2. The oxidation 
 of the body never produces light. 3. The oxidation in the 
 body is always in the presence of moisture. 
 
 The Amount of Carbon Dioxid given off. When the 
 breath is held for some time, the carbon dioxid in the 
 expired air may reach 7 or 8 per cent. During violent 
 exercise the amount of carbon dioxid given off may be 
 more than twice as much as when we are at rest. In 
 ordinary respiration there is one hundred times as much 
 carbon dioxid in the air we breathe out as there was when 
 it was taken in. Oxygen is carried chiefly in the cor- 
 puscles, but the carbon dioxid is carried in both plasma 
 and corpuscles. 
 
 Effect of Re-breathing Air. Every one knows how 
 unpleasant it is to breathe the air of a close room where 
 many people are present. In many persons such air 
 causes headache and drowsiness. This effect is not due 
 to the reduced amount of oxygen, nor is it due to the 
 increase of carbon dioxid. It is believed to be due to 
 the " organic impurities " which are thrown out in the 
 expired breath. It is this matter that gives the offensive 
 odor to a room which is kept close and warm after a crowd 
 has been in it. If in a crowded lecture room you divide 
 the space by the number of people present, you find that 
 each one has really very little room. In such rooms 
 special attention to ventilation is necessary, or great injury 
 will be done. When we learn how many cases of lung 
 
1 04 Physiology. 
 
 diseases are found wherever people are crowded into ill- 
 ventilated rooms, we can realize the force of the statement, 
 " Man's own breath is his worst enemy." 
 
 Summary of Respiration. The tissues need oxygen; 
 air is pumped into the lungs ; this air gives oxygen to the 
 blood ; the blood carries it to the tissues. 
 
 In oxidizing, the tissues produce energy (heat and 
 motion) and give off waste matter (water, carbon dioxid, 
 etc.); these the blood carries to the lungs, the lungs give 
 them to the air, and the air carries them out of the body. 
 
 The pumping of the air in and out and the exchanges 
 between the air and the blood in the lungs may be called 
 "external, or mechanical respiration." The action of the 
 oxygen of the blood in the tissues is the " real, or internal 
 respiration." 
 
 Summary. i. In passing through the lungs air loses oxygen, and 
 gains water, carbon dioxid, and other wastes. 
 
 2. Oxygen is carried chiefly by the colored corpuscles of the blood; 
 it unites with hemoglobin in the corpuscles, forming oxyhemoglobin, 
 and gives the blood its bright scarlet color. 
 
 3. The energy of heat and motion in the body results from the 
 oxidations in the tissues. 
 
 4. Air once breathed is unwholesome. The air of living and sleep- 
 ing rooms needs constant renewal. 
 
 5. When we exercise more, the muscles need more oxygen, so the 
 heart must beat faster and we must breathe faster. 
 
 6. The body is like a locomotive in producing heat and motion by 
 oxidation. 
 
 7. Air, once breathed, has one hundred times as much carbon 
 dioxid as before. 
 
 Questions. i. In what part of the lungs is the best air? Where 
 the worst? 
 
 2. Is it easy to determine by the color of blood flowing from a 
 wound whether it is arterial or venous? Why? 
 
Internal Respiration. 105 
 
 3. How is the air of a room affected by having many lamps or gas 
 jets burning ? 
 
 4. How is air affected by gasolene or kerosene stoves ? 
 
 5. Could a locomotive be run by feeding it with bread and meat ? 
 
 8 PHY 
 
CHAPTER XT. 
 VENTILATION AND HEATING. 
 
 Need of Proper Ventilation. When one is actively 
 exercising he may keep warm outdoors even on a cold 
 winter day. For the heat of the body depends on its 
 internal fires, the oxidation of its tissues. But if we are 
 inactive, these fires burn feebly, and we need outside heat. 
 While air is free, it really costs a good deal of money to 
 have it properly warmed. 
 
 A Lack of Effective Systems of Ventilation. Lung 
 diseases are rare in the regions where the windows and 
 doors may be kept open most of the days of the year. It 
 is from shutting ourselves in so closely that we suffer. 
 This is especially true where many people are housed in a 
 comparatively small space, as in many public buildings. 
 But in our private dwellings, even when the owners are 
 amply able to secure the best appliances, defective appa- 
 ratus is often put in. Any system that does not provide for 
 a constant reneival of the air is defective. 
 
 The General Principles of Ventilation. Of the forces 
 that renew the air of rooms two are natural, (i) diffusion 
 and (2) the wind ; and two are artificial, (3) warm air shafts 
 and (4) fan systems. 
 
 Diffusion. Gases tend to mix. We know that if a 
 bottle containing an odorous substance is opened in a 
 room where there are no air currents the odor tends to 
 
 106 
 
Ventilation and Heating. 107 
 
 spread equally through the room. If a person is in one 
 corner of a large room, where there are no inlets or out- 
 lets, and no currents, as he uses the oxygen immediately 
 around him, the oxygen farther away will diffuse toward 
 him so that he will continue to get oxygen as long as there 
 is any in the room. So, too, the gases that he breathes 
 out will not remain confined to the space directly about 
 him, but will spread nearly evenly throughout the room. 
 The same takes place in the open air, without wind. So, 
 then, if the windows and doors are open, the air of the 
 room will be renewed by diffusion. 
 
 Wind. Motion of the air renews faster than mere dif- 
 fusion. Strong wind forces its way through the cracks 
 around windows, and when windows are open on opposite 
 sides of a room there is usually enough breeze to renew 
 the air. But during part of the year this cannot be done. 
 
 Artificial Renewal of the Air. The renewal of the air 
 in most cases depends on the fact that heated air rises. 
 Heat expands air. It is then lighter, bulk for bulk, than 
 cooler air. The heavier surrounding air presses the lighter 
 air upward. If there are outlets above and below, the 
 heavier, colder air will press in below, and push the lighter, 
 warmer air out above. 
 
 Grates as Heaters. Grates are the simplest and prob- 
 ably the earliest form of heater. The fire throws out heat 
 in straight lines, or as we say, radiates heat into the room. 
 So much of the heat goes directly up the chimney that a 
 grate is very wasteful of fuel. 
 
 Grates as Ventilators. But a grate is an excellent ven- 
 tilator. There is always a decided draft toward a grate 
 fire. This means a constant renewal of air. The air 
 
io8 Physiology. 
 
 pushing toward the grate may be cold, and this has disad- 
 vantages that are hard to overcome in cold weather if there 
 is no other way of supplying heat. But it is a serious 
 question whether, with all our modern improvements in 
 heating, we have better air in our houses, or take cold less 
 often than our grandfathers, even if they did "roast on 
 one side while they froze on the other." 
 
 Stoves as Heaters. A stove is a very much more effec- 
 tive heater than a grate. In the first place the stove gives 
 off heat on all sides. In the second place a good deal of 
 heat is given off by the stovepipe ; while in the grate 
 almost no heat is saved from the flame and smoke. 
 Again, the fire can be better regulated in the stove. 
 
 Air Currents produced by Stoves. There is always a 
 current of heated air rising above a hot stove. Children 
 make whirligigs and other toys to place in these up-currents. 
 When this heated air reaches the ceiling it passes along 
 the ceiling, and comes down along the walls in the colder 
 parts of the room. At the same time colder air is flowing 
 along the floor toward the stove. This, in turn, is heated 
 and rises, making a constant circuit, along the floor to the 
 stove, up from the stove to the ceiling, along the ceiling 
 to the walls, and down the walls to its starting-point, again 
 to repeat the round. 
 
 Stoves as Ventilators. If there is an opening at the 
 top of the room, heated air will escape through it. Often 
 the heat is used to warm upstairs rooms in this way. If 
 a window is open at the top, some heat is lost. To make 
 up for the losses above named, and also for the air that 
 enters the stove and goes up the chimney, more air is 
 drawn in usually around doors and windows. It is espe- 
 cially noticeable where there are openings near the floor. 
 
Ventilation and Heating. 
 
 109 
 
 For the cold air is heavier than the warm air and continu- 
 ally pushes the warm air up and out of the room wherever 
 it can. But the stove does not send as much air up the 
 chimney as the grate does, and so does not draw in as 
 much fresh air. It is therefore not a good ventilator. 
 But the stove gets much more heat from a given amount 
 of fuel. 
 
 A Stove and Jacket. In some cases a jacket is placed 
 around a stove, and a duct from the outer air connects 
 
 Fig- 62. The Unjacketed Stove 
 
 with the lower part of the space inside of the jacket and 
 outside of the stove. Then as the air heated by the stove 
 rises, fresh air is drawn in from outside to be warmed. 
 In this case the direct heat from the stove is shut off from 
 the room. Heat radiates in straight lines. When one 
 holds out his hands beside a stove, the heat he receives 
 is radiant heat. Most of the heat from a grate is radiant 
 heat. But in a jacketed stove the heating by air currents 
 is called heating by convection. 
 
no Physiology. 
 
 The Furnace. A furnace is practically a jacket stove 
 placed in a basement. Hot-air furnaces have this good 
 feature, that they are all the time sending fresh air 
 into a room. The main trouble is, the air is usually too 
 dry. There should be in the furnace a pan of water to 
 furnish moisture to the air. 
 
 Foul-air Shafts and Fans. Although in private dwell- 
 ings heated by furnaces there is no special provision for 
 the escape of foul air, there is ordinarily sufficient renewal 
 of the air. But in public buildings there should be escape 
 flues for foul air. Frequently a large foul-air shaft is built 
 near the center of the building, and a small stove placed 
 in it to create a sufficient up-current. In many public 
 buildings the currents created by heat are not strong 
 enough to renew the air properly. Revolving fans are 
 used, which force the air, properly heated, into the room. 
 
 Direct Heating. In heating by steam or hot water, if 
 the radiators are placed in the room they give direct or 
 radiant heat. This system is called direct heating. It 
 gives direct heat, and produces air currents within the 
 room. In itself it has no provision for renewing the air. 
 
 Indirect Heating. In indirect heating, coils of steam 
 or hot-water pipes are placed in air shafts which lead up 
 to the rooms above, and also have ducts to the outside. 
 As the air is heated by the heat of the pipes it rises into 
 the rooms above, and fresh, cold air presses in through 
 the ducts, to be, in turn, heated and sent up. If there is 
 at the same time a proper escape for the foul air, this 
 makes an excellent system. 
 
 A Combination of Direct and Indirect Heating. It is a 
 good plan to combine direct and indirect heating. Where 
 
Ventilation and Heating. 1 1 1 
 
 there is a grate in a room, it serves very well as a foul-air 
 shaft, especially when there is a fire in the grate. It is 
 well to have the flue from the grate in the same chimney 
 with that from the smoke-pipe from the furnace, as then the 
 heat from the smoke will cause a constant up-draft in the 
 grate flue, whether there is a fire going in the grate or not. 
 
 With a grate, in private houses, there is ordinarily no 
 need of other foul-air shaft for any room. But it is very 
 desirable to have at least some "indirect" heat, so that 
 the fresh air introduced will be sufficiently heated. 
 
 If the introduction of air is thus provided for, it is then 
 safe to put on double windows and make the cracks around 
 the door very tight. Without any special provision for the 
 renewal of the air these cracks are the means of safety. In 
 houses heated by furnaces, steam, or hot water, the floor 
 is likely to be warmer from the escape of heat from the 
 heater itself, and from pipes or air ducts under the floor. 
 
 Double Windows. There is a very common misunder- 
 standing as to the cold felt near a window in cold weather. 
 It seems that air is entering; but a little reflection will 
 show that even if the window were air-tight this effect 
 would be produced, for the air near the window is cooled 
 by losing heat to the outer air through the glass. The air 
 next to the window, thus cooled, is heavier, and falls to the 
 floor ; and if there is any source of heat in the room, this 
 cold air will pass along the floor to that source of heat, up 
 from the heating body to the ceiling, and across the ceil- 
 ing, and so on around again. There may thus be currents 
 without any change in the quality of the air. It is 
 economy to use double windows and prevent the loss of 
 heat through the glass. So both economy and comfort 
 suggest to us that we reduce as much as possible cracks 
 around doors and windows, 'use double windows, make 
 
H2 Physiology. 
 
 vestibules at entrances, and build special ducts by which 
 fresh air may enter, and heat it properly on its way in. 
 
 To Air a Room without Draft To introduce fresh air 
 into a room without having a draft, a good plan is to get a 
 board four inches wide and as long as the width of the 
 window sash. Raise the window, place the board under 
 it and shut the window down upon the board. This will 
 allow air to enter between the upper and lower sash, and 
 it will be directed toward the ceiling. This is of double 
 advantage; in the first place, it does not strike any one 
 directly ; in the second place, it mingles with the warm air 
 of the upper part of the room before it reaches us. 
 
 Wearing Slippers. In rooms heated by stoves or grates 
 there is always more or less cold air moving along the 
 floor. Wearing slippers in such a room causes many per- 
 sons to take cold. The ankles have been warmly dressed 
 through the day and while the person was more active. 
 Especially if one is studying there is a tendency to draw 
 the blood away from the feet and make them cold. It is 
 restful, in the evening, to take off the shoes that have been 
 worn during the day; but, for most persons, it would be 
 better to put on a pair of loose shoes so the ankles will be 
 protected. The floor is usually the coolest place in a room. 
 In sitting in a room heated by a grate, or stove, the head 
 usually gets the most heat, and the feet the most cold, just 
 the reverse of what it should be. If much heat escapes 
 from a furnace, the floor may be warm. Those who use 
 stove heat in loosely built houses, learn to keep the feet up 
 on a stool when sitting in a room in cold weather. 
 
 Ventilation of Cellars. The cellar is the source of con- 
 tamination of the air of many houses. Of course a cellar 
 
Ventilation and Heating. I T 3 
 
 ought to be dry, well lighted, and well ventilated. But 
 since many of them are dark and ill ventilated, especial 
 care should be taken to keep them dry. Fruit and vege- 
 tables should not -be allowed to decay in the cellar. On 
 entering many houses one can at once detect the smell 
 of decaying potatoes and other vegetables. Such material 
 should be promptly removed. The best time to ventilate 
 a cellar is at night, for if the cellar windows are opened 
 in the day time, the entering air will deposit moisture, 
 making the cellar more damp instead of dryer. 
 
 Summary. i. Lung diseases usually accompany close confinement, 
 but are rare with those living in the open air. 
 
 2. Air in rooms needs constant renewal. 
 
 3. Grates are good ventilators, but not economical heaters. 
 
 4. Stoves are economical heaters, but poor ventilators. Both grates 
 and stoves heat very unevenly. 
 
 5. All crowded rooms, as schoolrooms and churches, need special 
 inlets for fresh air and outlets for foul air. 
 
 6. The most common means of withdrawing the air is by foul-air 
 shafts. Heat is the force relied on, but the removal of foul air is usually 
 inadequate, on account of the slowness of the current or the narrowness 
 of the outlet, or both combined. 
 
 7. Fans are much more certain to be effectual. 
 
 8. Steam and hot watsr may heat directly (by radiation) or indirectly 
 (placed in flues). It is best to combine direct and indirect heating. 
 
 Questions. i . How can we renew the air of a room without having 
 unpleasant drafts? 
 
 2. Should bedroom windows be open at night? Is night air bad? 
 
 3. What dangers in the use of hard coal ? 
 
 4. Should there be a damper in the smoke-pipe of a hard coal stove? 
 
 5. What do miners mean by " choke damp " ? 
 
 6. Compare stove and furnace heating. 
 
 7. Compare heating by steam and by hot water. 
 
 8. Read about the " Black Hole of Calcutta." 
 
CHAPTER XII. 
 DUST AND BACTERIA. 
 
 The Air is washed by Rain or Snow. Every one will 
 recall how delightfully refreshing the air is after a rain or 
 a snowstorm. This is not due merely to the fact that the 
 air is cool. It is clean because it has been washed. The 
 rain and snow absorb most of the various impure gases 
 that are in the air. The raindrops and snowflakes also 
 bring down with them many particles of dust that were 
 floating in the air. Take some of the snow that has fallen 
 in a town. It looks pure in its almost dazzling whiteness. 
 But melt some of it, and you will usually find that the 
 water has an inky tinge, showing that as the flakes sifted 
 down through the air they caught myriads of particles of 
 dust. 
 
 The Sources of Dust. Where soft coal is used to any 
 large extent it is one abundant source of this dust. In 
 summer dust has many sources. The dust that blows into 
 your face, and perhaps into your mouth, may be made of 
 dry soil. Take a dry clod and drop it ; it falls quickly to 
 the ground. Crush it in your hand before dropping it, and 
 much of it floats in the air for some time. Any substance 
 that is easily dried and reduced to powder may form part 
 of the common dust. The dust that you wipe from your 
 eye, or is caught by the mucus of the nasal passages, may, 
 instead of being made of clean soil, be from the excreta of 
 horses, decayed leaves, wood, grass, etc. Indoors we are 
 
 114 
 
Dust and Bacteria. 1 1 5 
 
 constantly making dust by wearing out our clothes. Many 
 of the tiny particles that we. see floating in the sunbeams 
 are bits of cotton or woolen fibers. Shake any garment in 
 a beam of light to see how much dust is given off. The 
 worn-off particles of our shoes, books, floors, all contribute 
 to the ever-present dust. 
 
 The Effect of Dust on the Lungs. This dust is irritating 
 to the lungs and respiratory passages. There is provision, 
 as we have seen, for catching and getting rid of a good 
 deal of it. But still much is taken into the lungs. Exam- 
 ination shows that the lungs have many black specks from 
 particles of carbon, etc., that have become lodged, and are 
 of no benefit, to say the least. 
 
 Composition of Live Dust. Bad as this dead dust is, the 
 injury from it is slight compared to that from live dust. 
 We know that certain seeds float in the air, carried along 
 by the wind. But these are comparatively heavy, and soon 
 sink to the ground. 
 
 We all know pollen. At certain seasons it forms, in the 
 vicinity of cornfields, for instance, a considerable part of 
 the dust. This is alive. It will grow if it falls on the 
 stigma of the right plant at the right time. Such dust will 
 not grow in our bodies. We do not furnish a soil in which 
 it can grow. It merely adds to the amount of irritating 
 dust. 
 
 Puffballs and Molds. We have seen puffballs give off 
 a cloud of dust when they are crushed. So, too, from a 
 patch of mold, when brushed, we often see a little cloud of 
 dust. This dust is composed of live spores that will grow 
 in suitable places and conditions. 
 
 Yeast. If we set a tumbler of cider on a table in a 
 warm room, in a few days it ferments. This is due to 
 
1 1 6 Physiology, 
 
 a kind of living germ or spore that has gotten into it from 
 the dust on the fruit before it was crushed, or from dust 
 in the room. Boil the cider to kill the spores already in 
 it, and cork it securely so that air cannot get at it, and it 
 will not ferment. These are a few instances of kinds of 
 living dust that do not affect human beings any more 
 than so much dead matter. 
 
 Disease Germs. But there are floating in the air many 
 kinds of spores that may grow in our bodies. We know 
 that many of our contagious diseases are due to the growth 
 of some of these spores in our bodies. Our bodies are a 
 good soil for certain germs. The germs that cause con- 
 sumption, typhoid fever, Asiatic cholera, erysipelas, diph- 
 theria, lockjaw, the grippe, malaria, yellow fever, and blood 
 poisoning are well known. Microscopists know them when 
 they see them as readily as we know peas from beans. 
 And it is proved beyond all doubt that these germs get 
 into our bodies by being breathed in, or by being eaten in 
 food, or in drinking water, or by introduction into the 
 blood in wounds. We have reason to believe that small- 
 pox, measles, mumps, whooping-cough, and scarlatina are 
 caused by germs, but these diseases have not been studied 
 so successfully. 
 
 How to avoid Germs. How can we avoid or get rid 
 of dusts of these kinds ? To exterminate any plant, we 
 try to keep the seeds from ripening, and to kill all that do 
 ripen. Let us take a case that, while not pleasant to think 
 about, is too terribly true to allow of being called an imag- 
 ined case. 
 
 The Danger from Consumption. A consumptive spits 
 on the pavement. In this sputum are probably hundreds, 
 if not thousands, of germs known as bacilli (Bacillus tuber- 
 
Dust and Bacteria. 
 
 117 
 
 culosis). They are alive. Now, so long as they remain 
 on the pavement they do no harm. The sputum dries. 
 But the bacilli are not killed by drying. With other dry 
 material from the pavement they form part of the common 
 dust. Any one of us may breathe some of this kind of mat- 
 ter any day, for there are persons afflicted with this dreaded 
 
 Bacillus of Diphtheria (x 1000) 
 
 Bacillus of Tuberculosis (x 1000) 
 
 Bacillus of Typhoid Fever (x 1200) 
 showing flagellums 
 
 Bacillus (Spirillum) of Asiatic Cholera Bacillus of Hog Cholera (x 1000) 
 
 Fig. 63. Different Kinds of Bacilli. 
 
 disease in every community. Our bodies furnish the very 
 best soil for the germs. We do not need to go into the 
 street to be exposed. These germs may be brought into 
 the most cleanly houses upon one's clothing, or by the wind. 
 
 How to avoid the Danger. Of course, all such material 
 known to be dangerous should be destroyed. If those 
 suffering from such diseases were careful to burn all such 
 matter, in time we might stamp out the diseases. But so 
 
1 1 8 Physiology. 
 
 long as people spit upon the floors and pavements it will 
 be difficult to prevent the spread of such germ diseases. 
 
 In hospitals such matters are now looked after with the 
 greatest care, and in private houses where there is intelli- 
 gence on these subjects. Many of the railroad and street 
 car companies now forbid spitting on the floors of cars 
 and stations, not merely because it is uncleanly, but be- 
 cause it is a means of spreading infectious diseases. 
 
 Bacteria. These disease germs are the smallest and 
 simplest of living things. They are plants ; and while all 
 of them that are well known have their scientific names, 
 just as the larger plants have, they are all included in one 
 general group called Bacteria. 
 
 How to avoid Dust. We need to learn a good deal 
 more about avoiding and destroying dust, and the things 
 that make it. Towns and cities need more sprinkling to 
 keep the dust down. Much more of the refuse and street 
 sweepings and cleanings ought to be burned. The dust of 
 a house should always be burned, as we know not what 
 germs of disease may be in it. If we burn it, we shall 
 surely not have to sweep up that dust again. If we send 
 it out of doors it may come back, and we may have to 
 handle it again and again. 
 
 Sweeping and Dusting. So far as possible let us avoid 
 things that make dust. When we sweep a carpet, a con- 
 siderable share of the dust comes from the carpet itself, 
 especially if the carpet is old. Curtains and tapestries of 
 nearly all sorts not only hold dust, but contribute a good 
 deal to it. Those who write on such subjects recommend 
 hard wood floors with rugs instead of carpets. The rugs 
 can be taken out of doors and shaken, and the floors wiped 
 with a moist cloth, so that little dust is left floating in the 
 
Dust and Bacteria. 119 
 
 air of the room. Compare this with the condition after the 
 ordinary sweeping of a carpeted room with the common 
 broom. The dust fills the air, only to settle back on the 
 floor and furniture. Then comes the so-called dusting. 
 But do we get rid of the dust ? For those who cannot have 
 hard wood floors a most excellent substitute is oilcloth or 
 linoleum. 
 
 Sweeping the Sick Room. The improved carpet 
 sweepers are not only convenient, but sanitary. Many a 
 well-meaning person will sweep a carpet in a sick room 
 with an ordinary broom when the patient is suffering from 
 lung disease, thoughtless of the fact that a little dust on 
 the floor is of much less significance than dust in the air 
 we breathe. No one likes dust on the floor, but better a 
 thousand times there than in our lungs. 
 
 Lung Diseases. Statistics seem to show that . one 
 seventh of the deaths among the civilized races is due to 
 lung diseases. The best authorities are now agreed that 
 consumption is not hereditary. But it appears that there 
 may be inherited a tendency to this disease, so that, if ex- 
 posed, such persons are more likely to contract the disease 
 than others. Probably anything that lowers the general 
 vitality makes the system more ready to yield to any of 
 these contagious diseases. We have all noticed what a 
 difference there is among individuals in the readiness with 
 which they "catch" contagious diseases. 
 
 How to ward off Contagious Diseases. A good general 
 condition of the body helps greatly to ward off diseases of 
 this nature. A cheerful condition of mind and body should 
 be cultivated. In times of widespread contagious disease, 
 if one is terrified into the belief that he is going to have 
 the disease, he is more likely to take it. Thorough clean- 
 
I2O Physiology. 
 
 liness, plenty of direct sunshine, care in diet, and the 
 keeping of the body in good tone, reduce the chances of 
 "taking" contagious diseases. An open-air life, abundant 
 nutritious food, and freedom from anxiety are probably the 
 best cures for the first stages of consumption. 
 
 Destruction of Germs by Colorless Corpuscles. The 
 
 colorless blood corpuscles may take these germs of disease 
 into their substance, and destroy or change them so that 
 the disease is warded off. In other words, they may be 
 compared to a cat that catches and eats the mice which 
 invade a house. 
 
 Germs killed by Plasma. Sometimes the blood con- 
 tains a substance that kills or prevents the action of dis- 
 ease germs. Such a substance is called anti-toxin, which 
 means a counteracting poison. But the blood of most 
 persons does not naturally contain anti-toxin, and so, if the 
 disease germs gain entrance, the disease follows. 
 
 Danger of getting Germs into Wounds. There is danger 
 of introducing germs of disease in so simple an act as pick- 
 ing out a sliver with a pin. If such germs happen to be 
 on the point of the pin, the mischief is easily done. Great 
 care should be taken in any such operation to use a 
 thoroughly clean needle or lancet Formerly any surgical 
 operation that required opening the body cavity, either the 
 chest or the abdomen, usually resulted in death. Now- 
 adays such operations are commonly successful, because 
 surgeons sterilize their instruments, hands, and everything 
 used about the work. They kill any germs that might 
 be ' introduced. In "a word, they have learned to be 
 clean. 
 
 In caring for a patient ill of any germ disease, one should 
 wash the hands in some disinfectant, such as chlorid of 
 
Dust and Bacteria. 121 
 
 lime, and should not touch the fingers to the lips; igno- 
 rance of these simple rules has caused many deaths. 
 
 Malaria and Yellow Fever. Malaria is due to an animal 
 germ (not a bacterium) that gets into the blood. It is 
 introduced by mosquitoes that have bitten persons whose 
 blood contains these germs. The same is true of yellow 
 fever. 
 
 The Bacteria of Putrefaction. Besides the disease- 
 producing bacteria, there are others that cause decay and 
 putrefaction of various kinds. They cause foods to " spoil," 
 milk to turn sour, butter to become rancid, etc. 
 
 While these, bacteria do not cause disease in the human 
 body, they often make food poisonous. The cases fre- 
 quently reported of poisoning from eating ice cream, 
 cheese, sausage, etc., are in many cases due to bacteria 
 in them. We should, in the first place, be careful to get 
 good, fresh material. In the second place, it should be so 
 kept as to prevent the introduction and development of 
 bacteria in it. Bacteria need heat and moisture for their 
 growth just as higher plants do. 
 
 The Preservation of Foods. So our principal modes of 
 keeping foods from spoiling are to keep them in a cold 
 place, or to dry them. Or we heat them, and shut them 
 away from the air, as in our various modes of canning and 
 preserving foods. Salting and smoking meats, etc., pre- 
 serve them by preventing the growth of bacteria. Cold 
 does not usually kill bacteria. So milk that has been kept 
 in a refrigerator, and that seems sweet, may have in it a 
 stock of bacteria, and after we drink the milk the heat of 
 our bodies favors their development. If milk is heated to 
 160 or 170 F., any germs of tuberculosis present will be 
 9 PHY 
 
122 Physiology. 
 
 killed. Boiled milk is less readily digested, and it is not 
 necessary to boil it to kill most kinds of germs that it may 
 contain. 
 
 Summary. I . Dust as mere dry, dead matter is irritating. 
 
 2. Disease germs may form part of the dust of the air. 
 
 3. Most of our contagious diseases are known to be due to bacteria. 
 
 4. Burning is the surest method of destroying germs. 
 
 5. Carpets, tapestries, and cloth-upholstered furniture add largely 
 to the dust in houses. 
 
 6. Putrefaction is caused by bacteria. 
 
 7. Preservation of food depends on destroying, excluding, or retard- 
 ing the growth of the bacteria of putrefaction. 
 
 Questions. I. Is the air in the mountains or on the seashore better 
 than elsewhere? 
 
 2. What regions are recommended for consumptives ? Why? 
 
 3. How is milk sterilized? 
 
 4. Why do people seldom take cold while " camping out "? 
 
 5. Why are the "steel grinders," in factories, short-lived? 
 
 6. What occupations should be avoided by one who is predisposed 
 to consumption ? 
 
 7. What are some of the occupations suitable to those predisposed 
 to consumption? 
 
CHAPTER XIII. 
 EXCRETION. 
 
 The Formation of Waste Matter in the Body. All the 
 
 force, or energy, of the body is produced by oxidation in 
 the tissues; thought by oxidation in the brain; motion by 
 oxidation in the muscles; and heat, wherever oxidation 
 goes on. This oxidation produces waste matter in our 
 bodies just as we have seen that oxidation in a stove 
 produces waste matter. 
 
 The Need of Removal of Waste. When we waken on a 
 cold winter morning we are likely to find that the fire in 
 our hard coal stove has burned low. Not enough heat is 
 given out. What is the trouble? Is it merely that more 
 coal is needed ? We put another hod of coal in the maga- 
 zine (though usually some remains). Does this bring the 
 desired result? No. We open the draft. Is this suffi- 
 cient? It is not. We must shake down the grate and 
 clean out the clinkers. The removal of waste is as neces- 
 sary as the addition of a fresh supply of fuel. In this case 
 more necessary, for no amount of fuel will do any good so 
 long as the ashes shut off the draft. In our bodies the 
 removal of waste is still more important, because waste 
 matter not only clogs the system, but, if present in any 
 great amount, acts as a poison to the tissues. 
 
 The Skin throws off Waste Matter. The skin is 
 constantly throwing off waste matter called sweat, or 
 perspiration. 
 
 123 
 
124 
 
 Physiology. 
 
 Experiment to show Insensible Perspiration. Thrust the hand into 
 a cold glass jar. Note the moisture that soon gathers on the inside of 
 the jar from the insensible sweat of the hand. A common fruit jar will 
 do for a small hand, but a candy jar is better, having a larger mouth and 
 clear glass. 
 
 The Structure of the Skin. The skin has two layers, 
 the inner, or dermis, and the outer, or epidermis. The 
 
 epidermis is thick 
 over the palms and 
 soles; elsewhere it 
 is thin. The skin is 
 much thicker than 
 we would naturally 
 suppose, and makes 
 one fifteenth of the 
 weight of the body. 
 
 The Epidermis. 
 
 The epidermis con- 
 Cells sists of many layers 
 of cells packed 
 *Buib closely together. 
 The deepest cells 
 may be compared to 
 grapes with their cell 
 walls 'plumply filled out with the liquids of the cell. Sup- 
 pose for the inner layer, grapes set on end, and so closely 
 packed together as to press each other more or less flat on 
 the sides. Above these are cells less closely pressed, more 
 nearly spherical ; then cells with less liquid in them, and 
 somewhat shrunken, like raisins. Then still dryer cells 
 flattened parallel with the surface of the skin. And, last, 
 in the outer part, layers of cell walls, dry and empty, pressed 
 flat like empty grape skins. These flat cell walls come off 
 
 Fat 
 
 Fig. 64. Vertical Section of the Skin. 
 
Excretiorio 
 
 125 
 
 in flakes (those from the scalp are called dandruff) from 
 all the surface of the skin, and new cells are continually 
 formed in the deeper layers. 
 
 Mouth of Sweat Duct 
 
 Horny Epider- 
 mis 
 
 Soft Laye. 
 
 Papilte 
 
 Dermis 
 
 rtery 
 
 Fig. 65. Section of Epidermis, showing Papilla. (Highly magnified.) 
 
 The Color of the Skin. The coloring matter, or pig- 
 ment, of the skin lies in the deeper layer of the epidermis. 
 In albinos the pigment is wanting. In persons with fair 
 skin it is small in amount, in dark skins more abundant. 
 Where the pigment is scattered irregularly it causes 
 freckles, etc. 
 
 A Blister. A blister is caused by separating the outer, 
 harder layer of the epidermis from the inner, softer, darker 
 layer of the epidermis, as at B, in Fig. 64. Serum, or 
 blood, fills the space between the separated layers. 
 
126 Physiology. 
 
 The Dermis. The dermis consists chiefly of tough, 
 interlacing fibers. Hence the strength and durability of 
 leather, which is the dermis preserved and prepared. The 
 epidermis is usually removed in tanning. The dermis is 
 richly supplied with blood capillaries and lymph capillaries, 
 but the epidermis has neither. 
 
 Papillas. The outer surface of the dermis has many 
 conical elevations, each of which is called a papilla. Over 
 most of the skin they do not show on the outer surface, as 
 the epidermis fills in the spaces between them, but is, itself, 
 smooth on the outside. On the palms and soles the papillas 
 are in rows, and these rows are indicated by the ridges. 
 
 Hairs. Hairs are outgrowths of the epidermis, but are 
 deeply embedded in the dermis. They are supplied with 
 blood at the tip of the root, where the growth takes place. 
 The exposed part of the hair does not contain blood and is 
 not sensitive. (See Fig. 64.) 
 
 Hair-muscles. There are small muscles connected with 
 the roots of the hairs, by which the hair may be slightly 
 moved. In the lower animals this power is much more 
 used, as when the hair is made to stand erect on the back 
 or tail of an angry cat or dog. The action of these muscles 
 when frightened is what gives a peculiar feeling in the 
 scalp, and to express strong fright we say, " It made his 
 hair stand on end." 
 
 Oil Glands. The oil glands of the skin are distributed 
 over all the surface except the palms and soles. The oily 
 matter is usually poured out around the hairs as they 
 emerge from the skin ; but some of the ducts open on the 
 skin away from a hair. The oil serves to soften the skin 
 and hair and keep them from becoming too dry. (See 
 Fig. 64.) 
 
Excretion. 1 27 
 
 Nails. The nails, like the hair, are outgrowths of the 
 epidermis. At the base the nail is supplied with blood, and 
 here it grows. It is alive, hence this part is called the 
 quick ; but at the outer surface and the tip it is dead. 
 
 Examination of the Skin with a Lens. Place a linen tester, or other 
 hand magnifier, over the palm, and note the sweat pores or openings of 
 the ducts of the sweat glands. Count the pores within the square shown. 
 Measure this square, and then estimate the number of sweat glands to a 
 square inch of the palm. 
 
 The Sweat Glands. The sweat glands are minute tubes 
 whose inner ends are closed, and whose outer ends open 
 upon the surface of the skin. The tube going inward pur- 
 sues a corkscrew-like course through the epidermis, then 
 becomes straighter, and is coiled up in a ball in the deeper 
 layer of the dermis, or, more often, in the connective tissue 
 just beneath the skin. (See Fig. 64.) The cells forming 
 the walls of the coiled part are different from those of the 
 duct, or straighter part of the tube. As the blood flows 
 through the capillaries of the skin it gives off lymph. In 
 this lymph are waste matters brought from the muscles 
 and other tissues that have been at work. The sweat 
 glands absorb this waste matter, with considerable water, 
 and pass it out to the surface. 
 
 Composition of Sweat. Sweat is mostly water. About 
 one per cent is solid matter, including salt and certain 
 matter which like the organic waste matter from the lungs, 
 easily putrefies. Sweat varies greatly in its wateriness and 
 hence in the relative amount of solid matter contained. 
 Ordinarily the sweat is evaporated as fast as it is poured 
 out. In distinction from this insensible perspiration, there 
 is the sensible perspiration when it accumulates enough 
 to be seen. These are not two kinds of sweat, but it is con- 
 venient to distinguish between the visible and the invisible. 
 
128 Physiology. 
 
 The Amount of Perspiration. There is about one quart 
 in twenty-four hours. It varies with ( i ) The temperature 
 and dryness of the air. (2) The condition of the blood, 
 e.g. if watery from drinking much water. (3) Muscular 
 exercise. 
 
 Gland Action and Blood Supply. The sweat glands, like 
 all glands, are largely dependent on the amount of blood 
 supply. In exercising, the skin is usually redder from the 
 greater supply of blood, and at the same time the glands 
 are more active, for during exercise and for some time 
 afterward there is more waste matter to be thrown out. 
 
 Control of the Sweat Glands. But the activity of the 
 gland is not a mere filtering process ; it is not always in 
 proportion to the amount of liquid present. There may 
 be a cold sweat, i.e. when the skin is pale. This usually 
 is due to excitement or emotion, which shows that the 
 action of glands is under the control of the nervous system. 
 
 Sweat Glands are Excretory. The sweat glands rid the 
 body of certain waste matters, and are therefore called 
 excretory glands. A sweat gland is a simple gland. 
 
 Distribution of Sweat Glands. The sweat glands are 
 thickly distributed over the whole surface of the body, but 
 are especially numerous and large on the palms and soles. 
 In the armpits the glands are also large. 
 
 Regulation of the Temperature of the Body. It is a very 
 striking fact that, except in disease, the temperature of the 
 body varies only a little from 98.5 F. in winter and 
 summer, during exercise and rest. The rate of producing 
 heat varies greatly. The rate of giving off heat must 
 therefore vary accordingly. 
 
Excretion. 1 29 
 
 The Body gives off Heat. In considering the regulation 
 of the temperature of the body, we must bear in mind that 
 the body is surrounded by air that is almost always con- 
 siderably cooler than itself. The body is therefore almost 
 always giving off heat. Our clothes do not warm us ; we 
 warm them, and they keep us from warming the air too 
 fast, i.e. they keep us from losing too much heat. Indoor 
 air in winter should be kept at about 68 F. by artificial 
 heat. This air does not warm us ; we, being about 30 F. 
 warmer, are warming it. 
 
 Ways of giving off Heat. The skin gives off heat by 
 
 1 . Radiation : heat is given off in every direction. 
 
 2. Conduction: whatever we touch that is cooler than 
 our bodies is warmed. We warm chairs, clothing, etc. 
 
 3. Convection: the air in contact with the skin is 
 warmed and rises. Our bodily heat is thus carried off by 
 convection. 
 
 4. Evaporation: the evaporation of sweat is the most 
 important factor in regulating the heat of the body. Any 
 liquid in evaporating absorbs heat. The cooling effect of 
 alcohol, ether, or cologne on the skin is due to the fact 
 that heat is taken from the skin in converting the liquid 
 into a gas. 
 
 Experiment in Evaporation. With a medicine dropper put a drop 
 of cologne on the back of the hand. Note two facts : (i) it produces a 
 cooling effect ; (2) the liquid quickly disappears. 
 
 Practical Applications of this Principle. We sponge a 
 feverish patient to reduce his temperature. The cooling 
 effect is due not so much to the coolness of the water itself 
 as to the absorption of heat from the skin in evaporating 
 the water. We sprinkle the floor in hot weather and thus 
 cool the air of the room. 
 
130 Physiology. 
 
 Heat and Exercise. When we exercise we produce more 
 heat ; we sweat more ; more heat is taken from the body 
 to evaporate this sweat. If we are not exercising and are 
 in cooler air, we sweat less, and less heat is given off. 
 When we exercise there is more blood in the skin, and 
 more heat is given off by radiation, convection, and con- 
 duction. When we exercise less, the skin, especially in 
 cool air, is paler, i.e. has less blood in it, and heat is econo- 
 mized. Thus the temperature of the body is kept uniform. 
 
 Distribution of Heat in the Body. If more heat is pro- 
 duced in one part of the body than in others, the circula- 
 tion of the blood tends to equalize the temperatures of the 
 different parts. So, too, if one part is cooled, i.e. is losing 
 heat faster than others, the blood brings heat from other 
 organs to that part. If the hands and feet are exposed to 
 cold, it may do little good to have the rest of the body well 
 covered. A pair of wristers and a pair of leggings may 
 often add more to one's comfort than a heavy overcoat. 
 
 Regulation of Temperature by Clothing. In cold weather 
 we put on more clothing and select non-conductors of 
 heat, as woolen, leather, and fur. Many authorities recom- 
 mend light woolen for summer wear, since with it we do 
 not cool off so rapidly. 
 
 Regulation of Temperature by Food. In cold weather 
 we eat more. We also eat more fat and other heat- 
 producing foods. 
 
 Effect of Wet Clothing. In getting the clothing wet the 
 cooling effect is not so much from the temperature of the 
 water as from the loss .of heat in evaporating the water 
 from the clothing ; and this goes on for a long time. Of 
 course it is desirable to put on dry clothing as soon as 
 
Excretion. 1 3 1 
 
 possible. It is dangerous to sit down in wet clothing, even 
 on a warm day. Children seldom take cold from wading, 
 even in cold water, if barefooted ; but with wet shoes and 
 stockings they are likely to take cold. 
 
 Mechanical Protection by the Skin. This is the most 
 evident function of the skin. The skin is tough, strong, 
 and elastic, hence well fitted to cover the body and yield 
 with every motion, yet protect the softer and more delicate 
 tissues beneath it from injury. 
 
 Absorption by the Skin. The skin has slight power of 
 absorption ; hence there is some danger in handling cer- 
 tain poisonous substances. The chief danger, however, is 
 when there are cracks or sores on the hands. If one must 
 handle suspicious material, it is well to rub the hands with 
 vaseline. To use rubber gloves is safer still. 
 
 Review of the Functions of the Skin. (The skin as a 
 sense organ will be considered later.) I. Sensory. 2. 
 Heat-regulating. 3. Absorptive. 4. Protective. 5. Ex- 
 cretory. It will be easy to remember these five functions 
 if it is noted that their initials spell the word s-h-a-p-e. 
 
 Skin-grafting. Sometimes after extensive burns, or 
 other injury of the skin, bits of skin are taken from an- 
 other part of the body, or from another person, and trans- 
 planted to the injured part, where they grow. 
 
 External Features of the Kidneys. The kidneys are a 
 pair of bean-shaped bodies attached to the dorsal wall of 
 the abdomen. (See Fig. 32.) The spot corresponding to 
 the stem-scar of the bean is called the kilum. At this point 
 are three tubes, the artery by which blood enters the kid- 
 ney, the vein by which the blood leaves, and the ureter, by 
 which the urine is conveyed to the bladder. 
 
132 Physiology. 
 
 The Blood-supply of the Kidneys. On entering the 
 kidney the renal artery divides and subdivides, forming a 
 very complicated set of capillaries. Through the thin walls 
 of the capillaries certain waste matters pass into the cavity 
 of the kidney, from which they are conveyed by the ureter 
 to the bladder. (See Fig. 32.) 
 
 Urea. Urea is the nitrogen-containing waste of the 
 body. There is nitrogen in muscle, brain, and in all the 
 important organs of the body. When they work, some 
 urea is formed. If the urea accumulates in the blood, it 
 acts as a poison to the tissues. 
 
 Importance of the Work of the Kidneys. The kidneys 
 are the only organs that can remove the urea from the 
 blood ; hence their great importance. Small as they are, 
 their removal would soon cause death. Urea is a solid, and 
 could not very well be carried out of the body unless dis- 
 solved. So the urine consists mainly of water containing 
 urea, salt, and various other substances in small amounts. 
 
 Relation between the Kidneys and the Skin. There is a 
 very close relation between the kidneys and the skin. In 
 warm weather, and when exercising actively, we sweat more 
 and the kidneys excrete less water ; on the other hand, 
 when we exercise less, and especially in a cool place, we 
 sweat less, and the amount excreted by the kidneys is in- 
 creased. For instance, when one has a cold he is 
 more or less feverish ; that is, the action of the skin is inter- 
 fered with, and there is less perspiration. At such time 
 the kidneys have more work to do, and may be so over- 
 worked as to injure them permanently. 
 
 Summary. i. When the body works it produces waste matter. 
 
 2. Waste matter must be removed or it will poison the body. 
 
 3. The skin throws off sweat, mostly water carrying waste matter. 
 
Excretion. 133 
 
 4. Sweat is taken from the lymph by the sweat glands, which are 
 coiled tubes, opening on the surface of the skin. 
 
 5. The skin consists of two layers, the dermis and the epidermis. 
 
 6. The amount of sweat varies with heat, exercise, food, etc. 
 
 7. The body gives off heat by (i) radiation, (2) conduction, (3) con- 
 vection, (4) evaporation. 
 
 8. The temperature of the body in health stays at about 98.5 F. 
 
 9. The temperature is regulated by the evaporation of sweat. 
 10. Heat is distributed through the body by the blood. 
 
 u. In cold weather we eat more fat, and other food, to make heat. 
 
 12. The skin has five functions: touch, heat-regulation, absorption, 
 protection, excretion. 
 
 13. The kidneys remove urea from the blood. Urea is the nitrogen- 
 containing waste of the body. 
 
 14. If much urea is in the blood, the body is poisoned, and the re- 
 moval of the kidneys would soon cause death. 
 
 Questions. i. Do dogs, cats, and cows sweat? 
 
 2. Why is thirst relieved by moistening the skin? 
 
 3. Why is it a good sign when the skin of a feverish person becomes 
 moist ? 
 
 4. Why should clothing worn during the day be removed at night ? 
 
 5. Can food, medicine, or poison be absorbed through the skin? 
 
CHAPTER XIV. 
 FOODS AND COOKING. 
 
 Necessity of Food. Thus far we have been studying 
 processes by which the body's weight is reduced. We 
 have studied the oxidation in the tissues and the removal 
 of the wastes. Unless the tissues receive a supply of new 
 material, the heat and energy of the body cannot long be 
 kept up. 
 
 Food Defined. Foods are substances that build tissues 
 or produce energy without injuring any organ or function 
 of the body. Certain substances that do not become part 
 of any tissues, nor in themselves produce energy, are use- 
 ful in aiding the processes going on in the body. These 
 may be called accessory foods, e.g. condiments, such as 
 pepper. 
 
 Foods and Foodstuffs. Most of our articles of food 
 consist of two or more different kinds of materials. For 
 instance, milk consists (i) chiefly of water; and in it are 
 (2) the substance that makes cheese (casein); (3) cream, 
 from which we get butter (fat); (4) sugar, which gives 
 milk a sweet taste; (5) salts, such as common salt, lime 
 salts, etc. These different materials are foodstuffs. We 
 have many kinds of foods, but few foodstuffs, which we 
 find occurring over and over again, in various forms, in 
 the numerous things we eat. 
 
Foods and Cooking. 135 
 
 Kinds of Foodstuffs. i. Proteids (example, casein). 
 
 2. Fats. 4. Water. 
 
 3. Carbohydrates (starch and sugar). 5. Salts. 
 
 The Proteids. The chief substance in the white of an 
 egg is albumen, a typical proteid. Of the many proteids 
 some of the more commonly known are casein (the curd 
 of milk), gluten (in grains), legumin (in peas and beans), 
 fibrin (in blood), myosin (in muscles). Gelatin (obtained 
 from connective tissue and bones by prolonged boiling) 
 differs considerably from the proteids in composition, but 
 may be counted in with them. It is less valuable as a food 
 than the true proteids, although in certain circumstances 
 more desirable from the fact that it is very easily digested. 
 
 Importance of Proteids. The proteids are of special 
 importance as foods because the most active tissues 
 those of the muscles, nerves, and glands and the most 
 important liquids of the body, e.g. blood and lymph, con- 
 tain proteid. Proteid food, therefore, must be taken to 
 make good the losses of these tissues during their oxida- 
 tions. Proteid is the only foodstuff containing nitrogen. 
 
 Proteid-containing Foods. The principal proteid-contain- 
 ing foods are lean meat, fish, eggs, milk, cheese, and some 
 seeds which abound in the vegetable proteids. 
 
 Meat. Lean meat has about twenty per cent of proteid, 
 the rest being chiefly water. Beef and mutton are more 
 easily digested than veal and pork. Pork sometimes con- 
 tains a parasitic worm called trichina, which causes illness, 
 or even death, if eaten. Pork should be thoroughly cooked 
 so as to kill the trichinas. 
 
 Fish. Fish, when fresh, is a good food. Although, as 
 a rule, salted meats are less easily digested than fresh, 
 
136 Physiology. 
 
 salted codfish is a nourishing and economical food. Fish 
 is not an especially valuable brain food, as commonly 
 believed. 
 
 Eggs. Eggs contain considerable proteid, but their value 
 as food has been overrated. The yolk has a large amount 
 of fat. Although the egg has all the material needed to 
 form a chick, it is not a perfect food for man. 
 
 Milk. Milk, as we have seen, is an ideal food, in that 
 it contains all the kinds of foodstuffs, and in the right pro- 
 portion for the young mammal. But the proportions are 
 not right for the adult. An adult would need four quarts 
 and a half daily, and then he would not get enough carbo- 
 hydrates (represented in milk by the sugar). The oily 
 material in milk is in the form of minute globules, which 
 can easily be seen under the microscope. Each of these 
 oil droplets is surrounded by a thin envelope of albumen, 
 by means of which it is enabled to remain suspended for 
 some time instead of rising quickly to the surface. Such a 
 mixture of oil in a liquid is called an emulsion. When 
 cream is churned the albuminous covering is removed and 
 the butter " gathers." 
 
 Cheese. Cheese is very rich in prcteid, much more so 
 than lean meat. Yet, as it is hard to digest, we do not use 
 it much as food ; we regard it more as a luxury, while in 
 many parts of Europe it is largely used as food, taking the 
 place of meat. It is a cheap food, and might well be used 
 more extensively, especially by laboring men. When taken 
 with milk, it is said to be more readily digested. 
 
 Vegetable Proteids. Peas and beans (dried) contain as 
 much proteid (legumin) as meat, and all the cereals contain 
 some proteid (gluten). 
 
Foods and Cooking. 137 
 
 Fats. Fats are composed of carbon, hydrogen, and 
 oxygen. The oxygen is small in amount, so these foods 
 yield a great amount of energy by the oxidation of their 
 carbon (forming carbon dioxid) and hydrogen (forming 
 water). The fats most used are animal fats, including 
 butter. But some vegetable oils, such as olive and cotton- 
 seed oils, are used. 
 
 The Carbohydrates. Starch and sugar are the chief 
 carbohydrates. They are composed of carbon, hydrogen, 
 and oxygen, but not in the same proportions as in fats. 
 Starch is used in larger quantity than any other foodstuff 
 except water. Sugar is usually regarded as a luxury, yet 
 it is an important food. It is quickly absorbed. 
 
 Carbohydrate-containing Foods. The principal carbo- 
 hydrate-containing foods are the grains, vegetables, and 
 fruits. The most important grains are wheat, corn, rice, 
 oats, rye, and barley. 
 
 Wheat Wheat furnishes the principal breadstuff among 
 the more civilized nations. It is especially adapted to the 
 temperate zones. Taking into consideration its composi- 
 tion, digestibility, and other characteristics, it is the most 
 desirable of all the grains. 
 
 Wheat Flour. In ordinary white flour nearly all the 
 gluten has been removed with the bran or "middlings." 
 While wheat or bread made from the whole grain of the 
 wheat may support life, one would starve if he tried to live 
 on common white bread alone. It is almost entirely starch. 
 In the "entire wheat flour" it isclaimed that all the gluten 
 is retained, only the very thin outer husk of the grain being 
 removed. It does not make so white a flour, but it is better 
 adapted to use as a food. If we use white bread, having 
 thrown away the nitrogenous part of the wheat, we need to 
 
 10 PHY 
 
1 3 8 Physiology. 
 
 take more proteid from other sources than if we used the 
 entire wheat flour. This is not economy. It is claimed 
 that the entire wheat bread is more wholesome as well as 
 more nutritious. The part thrown away has in it phos- 
 phates as well as the nitrogenous material. This flour is 
 ground fine so that it has not the coarse particles which are 
 in Graham flour, and which are, in some persons, a source 
 of irritation to the mucous coat of the digestive tube. 
 
 Corn. Corn is one of the most nutritious of the grains. 
 Although somewhat less readily digested than similar 
 preparations of wheat, and, consequently, less desirable 
 for indoor workers, it is a fact that, for a given amount of 
 money, more nutriment can be obtained in corn meal than 
 in any other food known. 
 
 Rice. Rice forms a larger part of human food than the 
 product of any other plant, being often an almost exclusive 
 diet in India, China, and the Malayan islands. Rice has a 
 larger proportion of starch, and less of fats and proteids, 
 than the other^rains. It is best adapted for the food of 
 warm climates. 
 
 Oats. This grain was first used as food for man by the 
 Scotch, but the use has extended and become prevalent in 
 this country. In point of nutrition it is ranked higher by 
 some than ordinary grades of wheat flour. 
 
 Rye. Rye grows farther north than other grains, and 
 is largely used for bread in Russia and parts of Germany. 
 It is a valuable food, though less nutritious and less digest- 
 ible than the corresponding preparations of wheat. 
 
 Barley. This grain has wide range of cultivation, and, 
 while inferior to wheat, is considerably used where other 
 grains cannot be raised. 
 
Foods and Cooking. 139 
 
 Potatoes. Potatoes contain about twenty per cent starch, 
 two per cent of proteid, and no fat, the remainder being 
 chiefly water, with some useful salts, especially potash salts. 
 In spite of its relatively low food value, the potato is our 
 most useful vegetable on account of its abundance, the ease 
 with which it can be preserved, and the readiness and the 
 variety of ways in which it can be cooked. 
 
 Other Vegetables. The chief nutrient in vegetables is 
 starch, though in many the starch is present in small amounts. 
 The salts and acids present are of value, and care should 
 be observed not to remove too much of these salts in cook- 
 ing. The fibrous matter, cellulose, while indigestible, is of 
 value in adding bulk to the mass of food to be digested. 
 
 Scurvy. Formerly sailors were subject to scurvy ; this 
 is now attributed to a diet of fat and salt meat, to the 
 exclusion of fresh vegetables, etc. The disease is avoided 
 by a greater use of vegetables, lime juice, etc. 
 
 Fruits. Many of the fruits, such as bananas and 
 apples, have considerable starch and sugar. But the 
 fruits are more useful to us on account of their flavor, 
 due to aromatic bodies, and to their salts and the peculiar 
 fruit acids. 
 
 Water. Water constitutes about two thirds of the 
 entire weight of the body. It constitutes the bulk of the 
 liquids we have studied, blood, lymph, sweat, saliva, bile, 
 etc. Water dissolves and carries all the material of the 
 body. Hence we need a large Amount of it ; of course we 
 must remember that we get a good deal of water in most 
 of our solid foods. 
 
 Rain Water. Water, as it comes from the clouds, is 
 pure. After enough rain has fallen to wash the air, rain 
 
140 Physiology. 
 
 water is pure, and if caught on a clean roof (especially a 
 slate roof) and kept in a clean cistern, it is good drinking- 
 water. 
 
 Well Water. Falling upon the earth, the rain water 
 niters down until stopped by some layer, such as clay, 
 through which it cannot soak. This water is the supply 
 of our wells and springs. It always has more or less 
 earthy matter, especially lime, in solution, and is therefore 
 more or less " hard." Unless a large amount of mineral 
 matter or some special material is dissolved in it, it is 
 ordinarily good drinking-water. Such water is not pure, 
 in the strict sense of the word, but is pure for drinking 
 purposes. 
 
 Impurities in Water. The great source of danger is 
 from what are called "organic" impurities. Bacteria do 
 not thrive in pure water. They must have something on 
 which to feed and grow. But in water containing a large 
 amount of decaying animal or vegetable matter they are 
 likely to abound. And the most dangerous sources of 
 contamination are cesspools and sewers. Water may be 
 contaminated by such material and not have bacteria in 
 it, but is very likely to harbor such foes. 
 
 Contamination from Cesspools. The ordinary cesspool 
 is a grave source of danger. Because the well may be on 
 higher ground than the cesspool does not give assurance 
 that the water may not be polluted. Often when the sur- 
 face of the ground slopes in one direction, the strata 
 underneath may slope in the opposite direction, and the 
 well may be the reservoir into which the cesspool is 
 drained. Good authorities say that a cesspool should not 
 be allowed within a hundred feet of a well. 
 
Foods and Cooking. 141 
 
 Abolish the Cesspool. It is better and safer to have 
 no cesspool. Where a sewer system is not to be had, it is 
 better to allow no great accumulation of such material. A 
 deep pit in which a quantity of semiliquid matter gathers 
 is not only a nuisance but a source of danger. Privies 
 should have a very shallow pit, or none, and should be 
 cleaned often. There should be a little dust sprinkled in 
 each day, and occasionally some chlorid of lime or sulphate 
 of iron. 
 
 Typhoid Fever. Typhoid fever is usually caused by 
 drinking-water. The excretions of some one who has had 
 the disease find their way into the source of the drinking- 
 water. In many cases this has been clearly proved. Of 
 course the excretions of all such patients should be either 
 destroyed or thoroughly disinfected. 
 
 Ice Water. Although bacteria will not develop in a 
 cold place, they are not killed when frozen in ice, as 
 was formerly supposed. Further, ice, in forming, does 
 not throw out all the impurities, as was formerly believed. 
 So it is not safe to drink water formed from melted ice 
 unless the water of which that ice was made was good 
 water. The ice taken from ponds is not safe. If ice is 
 made artificially from suitable drinking-water, the melted 
 product will be essentially unchanged so far as the com- 
 position is concerned. Water may be cooled by placing 
 any ice around it, and we may have the desired tempera- 
 ture without danger. 
 
 Boiling Water. When one cannot get good drinking- 
 water, or when away from home where the water is of 
 doubtful purity, it is better to boil the water before using 
 it, either as a drink or in preparations of food that are not 
 to be thoroughly cooked. It seems to be proved that it is 
 
142 Physiology. 
 
 better to heat the water twice nearly to the boiling point 
 than to boil once only. The first heating may start the 
 germs into more active life, causing them to sprout (so to 
 speak), and a second heating several hours later may easily 
 kill them ; whereas it has been proved that one hard 
 boiling will not always kill the germs. 
 
 Cautions as to Drinking-water. If one uses tea and 
 coffee, it is safer to content one's self with these, and not 
 drink much water till that which is safe, as from deep 
 wells, can be obtained. In hot weather, and especially 
 for those who are engaged in hard work, it has been 
 found that a little oatmeal stirred in the water is bene- 
 ficial. When overheated, avoid drinking much cold water. 
 Repeatedly rinse the mouth with cool water, and swallow 
 very little. This is the way trainers manage a horse at a 
 race, and it is sensible to treat a man as carefully. 
 
 Salts. Salts include many substances besides common 
 salt. They aid in the solution of various substances dur- 
 ing digestion and in other processes. We cannot live 
 without them. Lime in the form of calcium phosphate and 
 calcium carbonate is essential, especially in the bones and 
 teeth. 
 
 Necessity of a Mixed Diet. Our experience, together 
 with the results of experiments on animals, teaches that 
 we could not live long if fed on any one class of food- 
 stuffs alone. We must take a representative of each of 
 the groups. We have noticed that most of our foods 
 already contain more than one foodstuff. We so combine 
 them as to get suitable proportions. Thus we eat bread 
 and butter (a small amount of fat with a large quantity of 
 starch and a little gluten), meat and potato, crackers and 
 cheese, pork and beans, egg on toast, bread and milk, rice 
 
Foods and Cooking. 143 
 
 and fowl, macaroni and cheese ; they " go well together " 
 chiefly because each contains what the other lacks. 
 
 Disadvantages of a One-sided Diet. In order to get 
 enough nitrogen from bread alone, one would have to eat 
 about four pounds a day ; meanwhile twice as much car- 
 bon as is needed would be taken, thus throwing an undue 
 amount of work upon the digestive organs. Again, one 
 would need to consume about six pounds of meat to get 
 the requisite amount of carbon, and six times as much 
 nitrogen as is needed would be taken ; to get rid of this 
 extra nitrogen would severely tax the kidneys and liver. 
 
 Effect of Cold on Appetite for Fats. In cold climates 
 a large amount of fat is consumed, while in the tropics 
 starch is the chief food. Our appetites call for more of 
 the fatty foods during the winter season. 
 
 Proper Diet While common experience has led people 
 to adopt a mixed diet, the proportions of the different food- 
 stuffs is not always what it should be. The proportions 
 of the foodstuffs (exclusive of water) may be roughly stated 
 as about I part of proteid, I part of fat, 3 parts of carbo- 
 hydrates. But this will vary somewhat with the amount 
 of work done, and other varying conditions. 
 
 Vegetarians. The so-called " vegetarians " recognize 
 the need of proteid food, and most of them seek proteid in 
 eggs, milk, and cheese. But these are animal products, 
 and the name "vegetarian" is inconsistent. They are 
 merely " anti-meat eaters." That we are adapted for 
 using flesh as part of our food is indicated in at least two 
 anatomical features : (i) we have canine teeth, though not 
 so fully developed as in the carnivora ; (2) the intestine in 
 carnivora is very short, that of the herbivora very long, 
 
144 Physiology. 
 
 but in man intermediate. Nevertheless, it is undoubtedly 
 true that many persons eat too much meat. 
 
 Beef Tea. Beef tea and various beef extracts are help- 
 ful. There is not enough nourishment in them to maintain 
 strength without other food. But many of the soups and 
 drinks made from them are beneficial. They refresh the 
 tired system wonderfully. If the man who feels " fagged 
 out" and takes a drink of liquor to "brace him up," as he 
 says, were to take a cup of hot bouillon, he would find him- 
 self "braced up," for the time, without any bad reaction, 
 or permanent injury to the system. 
 
 Cooking. Cooking is designed to make food more pala- 
 table and more digestible. Some foods, such as eggs, are 
 as digestible before they are cooked as after. But many 
 foods in the raw state are unattractive, whereas cooking 
 usually develops an agreeable odor and taste. Cooking 
 should soften the harder and tougher tissues, such as cellu- 
 lose in vegetables and the connective tissue of animal foods. 
 Cooking starch causes the starch grains to swell and burst, 
 and makes the starch more digestible. 
 
 Making Soup. -If meat be cut into small pieces and put 
 into cold water, and the water gradually warmed, the solu- 
 ble material of the meat may be extracted, and this is the 
 principle followed in making soups. 
 
 Boiling Meat. If we wish to cook the meat itself, the 
 juices should be retained instead of withdrawn. For this 
 purpose boiling water is poured over the meat to coagulate 
 the outer layer and prevent the extraction of the juices. 
 
 Baking, Roasting, and Broiling. The same principle 
 applies to baking, roasting, and broiling. The outside is 
 subjected to high heat at the beginning of the cooking, 
 which forms a sort of crust through which the nutritious 
 
Foods and Cooking. 145 
 
 juices cannot escape. In these modes of cooking it is very 
 desirable to reduce the heat after the first few minutes, so 
 that the interior may be cooked enough without over-cook- 
 ing the outside ; this is especially true in broiling. 
 
 Frying. Frying, as ordinarily done, is not a good mode 
 of cooking ; in fact, is often very bad, as the food is fre- 
 quently soaked with fat and rendered indigestible. But 
 true frying, that is, by immersion in boiling fat, is a good 
 mode of cooking. This coagulates the albuminous sub- 
 stance on the outside, keeps in the nutritious juices, and 
 prevents soaking with the fat. 
 
 Summary. I . Food is to build tissue or produce energy. 
 
 2. Foodstuffs are the simpler materials in foods. 
 
 3. The foodstuffs are proteids, fats, carbohydrates, water, salts. 
 
 4. The proteids are albumen, casein, gluten, legumin, fibrin, myosin, 
 gelatin. 
 
 5. They are found in meat, egg, milk, peas, beans, and a little in grains. 
 
 6. The carbohydrates include starch and sugar. 
 
 7. Starch is obtained from potatoes and the grains. 
 
 8. The most important grains are wheat, oats, corn, rice, and rye. 
 
 9. Wheat is considered the best grain, though more nourishment 
 can be obtained from corn meal, for a given amount of money, than from 
 any other food. 
 
 10. Vegetables contain some starch, but are of value from giving 
 bulk to the food. 
 
 1 1 . Water containing decaying organic matter is dangerous to drink, 
 because it is likely to contain bacteria, which poison us or cause disease. 
 
 12. Boiling water usually kills the bacteria in it. 
 
 13. Drinking ice water is injurious. 
 
 14. We take a mixed diet, as no one food contains all we need. 
 
 15. Cooking is to render food more palatable and digestible. 
 
 Questions. i. Is the appetite always a safe guide in eating? 
 
 2. Which kind of foodstuff is most expensive? Why? 
 
 3. Why is bread the " staff of life " ? 
 
 4. Make a list of the common foods, naming the foodstuffs in them. 
 
 5. How do flour and potatoes compare in cheapness ? 
 
CHAPTER XV. 
 THE DIGESTIVE SYSTEM. 
 
 DIGESTION IN THE MOUTH. 
 
 The Object of Food. The tissues are worn out by their 
 oxidation. They are built up again by the blood, and the 
 blood is renewed by the food. 
 
 The Digestive Tube. All food must be reduced to the 
 liquid condition, if it is not already liquid. The chief organ 
 in this work of liquefying the food is the digestive tube, or 
 " alimentary canal." As the food passes through the 
 digestive tube it is ground and liquids are poured upon it. 
 Thus it is reduced to a liquid that can be absorbed and 
 taken into the blood. 
 
 The Work of the Digestive Tube. To take a special 
 instance, a muscle is in part worn out by the oxidation 
 during its activity ; to replace the loss suppose we take a 
 piece of steak. We cannot substitute this directly in the 
 place of the worn-out tissue. In digesting the steak we 
 must tear it to pieces, and reduce it to a liquid form by the 
 action of the teeth and by the various liquids from the 
 glands along the digestive tube. The beefsteak, as such, 
 must be thoroughly destroyed ; in the liquid produced by 
 the digestion of the beef there is no trace whatever of the 
 structure of the beef. But the blood, taking this material, 
 builds muscle which can hardly be distinguished from the 
 original beef. 
 
 146 
 
The Digestive System. 147 
 
 If the food taken is a liquid and ready to build tissue, as 
 a thin syrup, it will not need to go through these changes. 
 
 The Organs of Digestion. The organs of digestion are 
 the digestive tube, with the masticating organs, and the 
 glands in and along the walls of the tube. 
 
 The parts of the digestive, tube are the mouth, the 
 pharynx, the gullet (or esophagus), the stomach, the small 
 intestine, and the large intestine. 
 
 The Mouth and Gullet. At the back of the mouth may 
 be seen the soft palate with the cylindrical uvula hanging 
 from its center. Beyond this is the cavity of the pharynx, 
 which narrows below into the gullet, a red-walled, muscular 
 tube, extending along the back side of the windpipe, and 
 close to the spinal column. It extends the length of the 
 chest, and then passes through the diaphragm and widens 
 into the stomach, at the upper left end of the latter. 
 
 The Stomach. The stomach is somewhat pear-shaped, 
 with the larger end to the left. At the right end it tapers 
 into the small intestine, the first foot or so of which is 
 called the duodenum. (See Figs. 53, 72, and 74.) 
 
 The Liver and Pancreas. Just below the diaphragm is 
 the dark-colored liver, overlapping a large portion of the 
 stomach. Between two of the three lobes of the liver is the 
 bile sac, whose duct enters the duodenum a short distance 
 from the stomach. The pancreas is a pinkish organ of 
 irregular shape lying along the stomach and duodenum. 
 Its duct enters the duodenum at the same point as the bile 
 duct. 
 
 The Intestine. The first part of the intestine is the 
 small intestine. At the lower right part of the abdomen 
 
148 
 
 Physiology. 
 
 this enters the larger intestine. The intestine is held 
 in place by the mesentery, a thin fold of transparent 
 
 membrane folded closely 
 around it, and supported 
 from the back wall of 
 the abdominal cavity. 
 Between the two layers 
 of the mesentery are the 
 branches of the artery 
 supplying the walls of 
 the intestines, and the 
 veins that convey the ab- 
 sorbed food from the 
 
 intestine to the liver. 
 
 Fig. 66. Cross-section of Abdomen. 
 
 The Mouth. - The 
 pupil should carefully examine his own mouth by means 
 of a mirror. We are apt to think of the mouth as a cavity 
 of considerable size, as indeed it is when fully opened; 
 but we are not so likely to think how completely the cavity 
 disappears when the mouth is closed. If one notes the 
 sensations from the mouth when it is closed, he will per- 
 ceive that the tongue almost entirely fills the space, touch- 
 ing the roof of the mouth, and the teeth in front and at 
 the sides. 
 
 The Tongue. The tongue consists chiefly of muscles, 
 running in different directions, thus giving it a variety of 
 motions. The tongue is the chief organ of taste, and is 
 therefore (with the sense of smell) the gate-keeper of the 
 digestive tube. The tongue has also a keen sense of 
 touch, and so is useful in detecting and removing any 
 food particles that may remain on the teeth after eating, 
 During mastication the tongue, with the lips and cheeks, 
 
The Digestive System. 
 
 149 
 
 keep the food between the teeth. When the morsel of 
 food is sufficiently masticated, the tongue pushes it back 
 into the pharynx to be swallowed. 
 
 The Teeth. The teacher can usually obtain a supply of teeth from 
 the dentist for the asking. These should be cleaned before using them 
 in the class. Use pearline or any washing soda. Let each pupil make 
 a drawing of one of each of the four kinds of teeth ; draw both a front 
 (outer surface) and a side view (surface adjacent to another tooth) of 
 all but a molar. 
 
 Longitudinal Section 
 
 Side View 
 
 Face View 
 
 Enamel 
 
 Pulp Cavity 
 
 Dentine 
 
 Cement 
 
 Crown 
 
 Neck 
 
 Root 
 
 Hole for Blood Tubes and Nerves J 
 
 Fig. 67. Parts of a Tooth. (Incisor.) 
 
 External Features of a Tooth. Examine one of the 
 front teeth. It has the following parts : 
 
 1. The crown, the part that is above the gum. 
 
 2. The root, the part that was buried beneath the gum. 
 
 3. The neck, dividing the crown from the root. 
 
 4. A hole at the tip of the root. 
 
 To make a Section of a Tooth. Let each pupil prepare a longitudi- 
 nal section of a tooth as follows : Embed a tooth in a little sealing wax 
 on the end of a spool, cork, or block of wood. With a grindstone grind 
 away one half, showing the pulp cavity to the tip of the root, as in 
 Fig. 67. Make a drawing of the surface thus exposed, naming the 
 
150 Physiology. 
 
 parts. If human teeth cannot be obtained, almost any kind will serve. 
 Let each pupil keep his preparation. 
 
 Structure of a Tooth. i. The pulp cavity, communi- 
 cating with a hole in the tip of the root, through which 
 the nerve and blood tube entered. 
 
 2. The bulk of the tooth is made of a substance called 
 dentine (ivory). 
 
 3. The crown of the tooth has a covering of enamel, a 
 very hard substance. 
 
 4. The root is covered with a bony substance, called 
 cement. 
 
 The Arrangement of the Teeth. Beginning at the middle 
 of the front of the mouth, there are (in the normal adult) 
 eight teeth in each half jaw : two incisors, one canine, two 
 bicuspids (or premolars), and three molars (see Fig. 68). 
 
 Dental Formula. The kinds and arrangement of teeth 
 are expressed by a dental formula, in which the nume- 
 rators indicate the upper jaw and the denominators the 
 lower, thus : If, C{, PMf , Mf (for one side of the head). 
 
 The Kinds of Teeth. The crown of an incisor is chisel 
 shaped ; but the root is flattened in the opposite direction, 
 i.e. at right angles to the jaw, instead of parallel to it, as 
 in the crown. The canine tooth has a conical crown, and 
 a longer root than the incisor. The bicuspid has two 
 points. The molar has a cube-shaped crown, and usually 
 two or three roots. 
 
 The Milk Teeth. The thirty-two teeth of the perma- 
 nent set were preceded by a temporary set of twenty milk 
 teeth. Because the first set is temporary, it should not 
 therefore be neglected. Cavities in these should be filled 
 and the teeth kept clean. Before the temporary set has 
 
The Digestive System. 
 
 gone the first of the permanent set appear. The first of 
 these, often called the " six-year molars," are just back of 
 the hindermost "milk molars." These should receive 
 especial care, as they will never be replaced. Any begin- 
 ning of decay in them ought to receive prompt attention. 
 
 KINDS OF TEETH 
 Incisors - .... 
 
 Upper 
 
 TIME OF APPEARANCE 
 7th Month 
 9th " 
 
 18th '* 
 
 I2th " 
 24th " 
 
 TEMPORARY SET 
 Upper 
 
 PERMANENT SET 
 Fig. 68. TEETH : Kinds, Arrangement, and Times of Appearance. 
 
 The Care of the Teeth. The teeth need careful atten- 
 tion. They should be thoroughly brushed at least twice a 
 day, on rising and on going to bed. It would be better to 
 clean them after each meal also. If a tooth powder, recom- 
 
152 Physiology. 
 
 mended by a reliable dentist, is not used, a good white 
 castile soap will serve well. It is better to use tepid water. 
 Toothpicks are useful in removing the larger particles. 
 Quill toothpicks are best ; metal should never be used. 
 The teeth should be examined twice a year by a dentist, 
 and any cavities promptly filled. 
 
 Cause of Decay of Teeth. If the teeth are not thoroughly 
 cleaned the particles of food which remain will soon begin 
 to decay. This decay is caused by the growth of germs, 
 usually some kind of bacteria, and the decay thus begun 
 is likely to develop acids which attack the limy material 
 of which the teeth are composed. When it is necessary 
 to take acid medicines, care should be taken not to let 
 them come in contact with the teeth. Sweet substances 
 are very likely to decompose and form acids ; so we must 
 clean the teeth after eating candies. When the teeth are 
 neglected, a limy substance, called tartar, forms on them 
 and encourages decay. 
 
 The Salivary Glands. The salivary glands make the 
 saliva and pour it into the mouth. There are three pairs 
 of salivary glands the parotid, just back of the angle of 
 the jaw, under the ear ; its duct opens on the inside of the 
 cheek opposite the second molar of the upper jaw. The 
 submaxillary gland lies under the angle of the jaw ; its 
 duct opens under the tongue near the front of the mouth. 
 The sublingual gland is in front of the submaxillary and 
 empties under the tongue (see Fig. 74). 
 
 Salivary Ducts in our Mouths. If the inside of one's cheek be 
 examined by the use of a hand mirror, the opening of the duct from the 
 parotid gland may be seen opposite the second molar of the upper jaw. 
 It usually looks like a pink and white spot, resembling a wound of a 
 bee sting. Sometimes saliva may be seen issuing from it. 
 
The Digestive System. 153 
 
 Action of the Salivary Glands. The salivary glands 
 pour into the mouth a liquid which they make from 
 materials taken from the blood. In structure the gland 
 may be compared to a bunch of grapes, the grapes repre- 
 senting the little cavities, with a wall of cells that make 
 the saliva. From each of these cavities the liquid passes 
 into its duct, represented by the stem of a single grape; 
 many of these unite to form the main duct, which corre- 
 sponds to the main stem. A thick network of capillaries 
 
 Mucous Membrane 
 
 Duct of Gland 
 
 Secreting Cells 
 
 Vaso- dilator 
 
 Nerve 
 
 ^^ 
 
 Fig. 69. Diagram of a Salivary Gland. (After Landois and Stirling.) 
 
 surrounds the gland ; the liquid part of the blood (plasma) 
 soaks out through the capillary walls and surrounds the 
 gland ; it is now called lymph ; from the lymph the gland 
 directly obtains its material. 
 
 Nerve Control of Salivary Glands. The glands are 
 doubly dependent on nerve control: 
 
 1. Through the nerve control of the muscles in the 
 walls of the arteries the amount of blood sent to the 
 glands is regulated. 
 
 2. Nerves also go to the cells of the gland to control 
 their activity. When we taste, smell, see, or even when 
 we think of, some delicious food the mouth may " water," 
 
 1 1 PHY 
 
T 54 Physiology. 
 
 as we say, i.e. the salivary glands are, by reflex action, 
 stimulated to activity ; on the other hand, some emotions, 
 such as fear, check the flow of saliva. 
 
 Saliva and its Uses. The saliva is mostly water, and, 
 when we are not eating, serves (i) to keep the mouth moist. 
 The water of the saliva soaks the food during mastica- 
 tion and (2) helps the process of grinding; it (3) enables 
 us to taste by dissolving any food that is soluble ; it 
 further (4) enables us to swallow what would otherwise 
 be a dry powder. The special element of the saliva, 
 ptyalin, has the power (5) of changing starch to sugar. 
 
 Amount of Saliva. The amount of saliva secreted 
 daily is estimated at three pints. Of course the glands 
 should be allowed to rest between meals. The habit of 
 chewing gum, though supposed to aid digestion, undoubt- 
 edly does far more harm than good. During the resting 
 period the glands accumulate material for the active work 
 of secretion, for there is no sac in which to store the 
 saliva, and -it must be made as fast as is needed. 
 
 Mucous Glands and Mucus. Besides the salivary glands, 
 there are great numbers of simple glands in the mucous 
 membrane lining the mouth. These secrete a clear sub- 
 stance called mucus, resembling white-of-egg. It is mucus 
 in saliva that makes it "stringy." 
 
 Mumps. In the mumps the salivary glands are in- 
 flamed and painful. This is most noticeable in the 
 parotid gland, which feels the pressure of the lower jaw 
 in the attempt to chew. 
 
 Summary. i. The chief work of digestion is to make the food into 
 a liquid, ready to be absorbed and become part of the blood. 
 
 2. The digestive system consists of a long tube, through which the 
 food passes, being subjected to mechanical and chemical processes. 
 
The Digestive System. 155 
 
 3. The parts of the digestive tube are the mouth, gullet, stomach, 
 and intestines. 
 
 4. Along this tube are several large glands, such as the salivary 
 glands, pancreas, and liver, which make liquids to pour upon the food. 
 
 5. The tongue is composed of muscles, is very movable, and 
 (i) tastes the food; (2) keeps the food between the teeth during 
 chewing; (3) aids in swallowing. 
 
 6. A tooth has crown, neck, and root. 
 
 7. The tooth consists of dentine, containing a pulp cavity. The 
 crown is covered with enamel, and the root is covered with cement. 
 
 8. There are thirty-two teeth in a full set, eight in each half jaw, 
 beginning at the front, two incisors, one canine, two bicuspids, and 
 three molars. The first set of twenty teeth are called " milk teeth." 
 
 9. The teeth must be kept clean by brush and tooth powder. 
 
 10. There are three pairs of salivary glands, parotid, submaxillary, 
 and sublingual. Their action is controlled by nerves. 
 
 1 1 . The chief use of saliva is to change starch to sugar. 
 
 Questions. i. Why should we not crack nuts with the teeth ? 
 
 2. Why does the physician examine the tongue of his patient? 
 
 3. Is it well to eat much soaked food ? Why not? 
 
 4. How many teeth have you, and of what kinds? 
 
 5. Why is gum-chewing injurious ? 
 
CHAPTER XVI. 
 DIGESTION IN THE STOMACH. 
 
 The Pharynx. The cavity back of the mouth, beyond 
 the soft palate, is the pharynx. The pharynx is a funnel- 
 shaped cavity, connecting above with the passages from 
 the nostrils; in front it opens into the mouth; below it 
 
 
 Eustachian Tube 
 
 Pharynx 
 Epiglottis, Raised 
 
 Gullet, Closed 
 Glottis, Open 
 
 Fig. 70. Positions of the Organs of the Mouth and Throat during Breathing. 
 
 connects with the windpipe, through the glottis, and with 
 the gullet, which lies just back of the windpipe (see Figs. 
 70 and 71). 
 
 Position of Organs during Respiration. In quiet respira- 
 tion the tongue nearly fills the mouth. The base of the 
 tongue is nearly covered by the soft palate, which curves 
 downward from the hard palate, and by the epiglottis pro- 
 jecting upward from below. The glottis is open and the 
 
 156 
 
Digestion in the Stomach. 157 
 
 gullet is closed. Air enters the nostrils, passes along the 
 nasal passages above the hard palate, back of the soft 
 palate and epiglottis, through the open glottis into the 
 windpipe, and on to the lungs. 
 
 The Process of Swallowing. When the morsel of food 
 is ready to be swallowed the tongue pushes it back into 
 the pharynx; the soft palate is raised to shut off the 
 passage into the nasal cavity ; the epiglottis is pulled down 
 
 ustachian Tube 
 Soft Palate, Raised 
 Food 
 
 Epiglottis, Down 
 Gullet, Open 
 
 Glottis, Closed 
 
 Fig 71. Positions of the Organs of the Mouth and Throat during Swallowing. 
 
 over the glottis, or opening of the windpipe; and the base 
 of the tongue extends back over the epiglottis; thus the 
 air passages, above and below, are shut off, and the food 
 passes over the epiglottis into the gullet. The muscles of 
 the pharynx also do their part in pushing the food along. 
 As soon as the food has passed over the epiglottis, the 
 epiglottis rises to its upright position, and the soft palate 
 drops back to its place, leaving the air passages again 
 open. 
 
158 Physiology. 
 
 Breathing and Swallowing. It is to be observed that 
 the food tube and the air tube cross, and that the pharynx 
 is their crossing. As we are swallowing only a small part 
 of the time, the passageway naturally stands open to the 
 air; and when we swallow, the parts are, by muscular 
 effort, temporarily arranged for this work. There is a 
 spring switch (to borrow a term from the railway) which 
 keeps the track open for the air, which is all the time 
 passing ; but when the food comes along, the switch must 
 close the air passage and hold open the food passage until 
 the food has passed. 
 
 Structure and Action of the Gullet The gullet has 
 an outer muscular coat and an inner mucous coat (see 
 Fig. 72). The muscular coat has two layers, an inner 
 with circularly arranged fibers, and an outer layer with 
 fibers running lengthwise. When the food enters the gul- 
 let the muscle fibers, especially the circular fibers, shorten, 
 and by a wave-like action push the mass rapidly along into 
 the stomach. The first part of swallowing is voluntary ; 
 but after the mouthful has entered the gullet the action is 
 involuntary. The mucous lining of the gullet has many 
 mucous glands which make the passageway smooth by the 
 mucus which they secrete. 
 
 Illustration of Passage through the Gullet. The passage of the food 
 through the gullet may be illustrated as follows : Let several persons 
 hold a large rubber tube with their hands in contact. Put an egg-shaped 
 piece of wet soap in the tube. The first hand is shut and pushes the 
 soap along into the part of the tube held by the next hand ; this hand 
 now compresses the tube, while the first hand remains clinched ; and so, 
 in turn, the object is pushed the whole length of the tube. 
 
 The Stomach. Just below the diaphragm the digestive 
 tube widens suddenly, forming the stomach ; the stomach 
 
Digestion in the Stomach. 159 
 
 is an oval sac lying just beneath the diaphragm, with the 
 large end to the left and the small end to the right. The 
 smaller end, by narrowing, becomes the small intestine. 
 When the stomach is empty it collapses, as its walls are 
 soft and flexible. When distended it may hold three pints, 
 or, when greatly distended, even more. 
 
 The Coats of the Stomach. The stomach and intestines have four 
 coats, in the following order, beginning at the outside : the peritoneum, 
 the muscular, the submucous, and the mucous coats. The muscular 
 coat of the stomach consists of three layers, distinguished by the arrange- 
 
 ILLET 
 
 SMALL 
 NTESTINE 
 
 Fig. 72. Longitudinal Section of Stomach, showing Gastric Glands in Position. 
 (Back View. Mucous Coat unduly Thickened.) 
 
 ment of the fibers, a circular layer, a longitudinal layer, and an oblique 
 layer. The mucous lining is somewhat loosely attached to the muscular 
 coat by the submucous coat between them, and when the stomach col- 
 lapses, the mucous coat is thrown into folds, usually running lengthwise. 
 
 The Gastric Glands. In the inner surface of the mucous 
 membrane are many holes. These are the mouths of the 
 ducts of the gastric glands. If a duct is traced inward, it 
 is found to be either a simple tube (see Fig. 73) or to divide 
 into branches, usually two or three. 
 
i6o 
 
 Physiology. 
 
 The Gastric Juice. The liquid secreted by these glands 
 is called the gastric juice. The gastric juice is chiefly 
 water, containing a substance called pepsin, and a small 
 amount of acid. The amount of gastric juice secreted 
 daily has been estimated at four or five quarts. Of course, 
 we must bear in mind that nearly all of this is again 
 absorbed from the digestive tube, and is not a loss to the 
 body. 
 
 Blood Supply of the Stomach. The mucous membrane 
 is well supplied with blood-tubes, but while it is resting the 
 
 blood flow is dimin- 
 
 Mouth of Giand Epithelium ished, and it is pale. 
 
 But as soon as food 
 is introduced into the 
 stomach the blood flow 
 is greatly increased, 
 and the mucous mem- 
 brane becomes red. 
 This blood supply gives 
 the glands the materi- 
 als with which they 
 manufacture the gastric 
 juice. At the same 
 time the cells of the 
 
 glands are stimulated to action, and the secretion is poured 
 out rapidly. The saliva also aids in stimulating the secre- 
 tion of the gastric j-uice. 
 
 The Work of the Gastric Juice. The special work of the 
 gastric juice is accomplished by the pepsin, aided by the 
 acid ; these change proteids into a soluble substance, called 
 peptone, which can be absorbed through the walls of the 
 digestive tube into the blood. 
 
 Connective Tissue 
 Fig. 73. Three Glands of the Stomach. 
 
Digestion in the Stomach. 161 
 
 Rennet and Rennin. Rennet, used in cheese making, is a familial 
 substance obtained from the fourth stomach of the calf. When milk 
 enters the stomach it is curdled ; that is, the casein previously dissolved 
 in the liquid milk is curdled. This curdling, or coagulation, is caused 
 by a substance in the gastric juice called rennin. 
 
 The Action of the Stomach. At the same time all the 
 food is soaked by the gastric juice, the process being 
 greatly assisted by the churning motion of the stomach 
 caused by the action of the muscular coat. This muscular 
 action of the stomach is called the peristaltic action. The 
 food is thus gradually reduced to a pulpy mass called 
 chyme. During the first part of digestion in the stomach 
 the thick ring of circular fibers, called the pylorus (gate- 
 keeper), around the opening from the stomach into the 
 intestine, keeps the passage nearly closed, leaving a small 
 hole for liquids only. But as the food is reduced to the 
 proper condition the muscles relax and allow the chyme to 
 pass into the intestine. And at last any indigestible sub- 
 stances are usually allowed to pass. 
 
 Sphincter Muscles. Such rings of muscular fibers as 
 the pylorus, guarding openings, are called sphincter 
 muscles. 
 
 Time of Stomach Digestion. The time required for the 
 stomach digestion of a meal is from three to four hours, 
 though this may be much longer if very indigestible sub- 
 stances have been eaten, or if the condition of the body 
 or mind is such as to retard the process of digestion. 
 
 Chyme. The rest of the food, now called chyme, is 
 passed on into the small intestine. It is acid, and in a 
 liquid or semiliquid condition. Chyme, as it enters the 
 intestine, is a mixture of digested, partly digested, and 
 undigested materials. Some of the starch has been changed 
 
1 6 2 Physiology. 
 
 to sugar, but only a small part, owing to the short time of 
 mastication. The bulk of the starch is unchanged. Some 
 of the proteid is already changed to peptone. Part is still 
 proteid, while part is in an intermediate stage between 
 proteid and peptone. Fat is melted by the heat of the 
 mouth and stomach, and is more or less divided into small 
 drops by mastication and the movements of the stomach. 
 For instance, in eating bread and butter, the melting butter 
 will be finely mixed with the bread as it is chewed. The 
 water in the chyme was partly taken as such, and partly 
 derived from the saliva and gastric juice. There are also 
 present ptyalin, pepsin, mucus, salts, and some indigestible 
 substances. At intervals the sphincter muscles of the 
 pylorus relax, and the contractions of the stomach send the 
 liquid mixture into the intestines by spurts. 
 
 Heart-burn. Heart-burn is a burning feeling in the 
 stomach and lower part of the chest caused by indigestion. 
 There is a fermentation in the stomach, usually producing 
 an acid or sour stomach. 
 
 Summary. i . The pharynx opens into the mouth, nostrils, wind- 
 pipe, and gullet. 
 
 2. In breathing, air passes through the nostrils and the pharynx, 
 and enters ,the windpipe ; the soft palate is down and the epiglottis 
 is up. 
 
 3. In swallowing, food passes from the mouth, through the pharynx, 
 into the gullet; the soft palate is raised and the epiglottis is pressed 
 down, covering the opening into the windpipe. 
 
 4. Food is pushed along the gullet by the shortening of the ring- 
 like muscles. 
 
 5. The stomach is pear-shaped, with the large end to the left. 
 
 6. The stomach has four coats, serous, muscular, submucous, and 
 mucous. 
 
 7. The gastric glands are tube-like pits in the mucous coat of the 
 stomach. They make gastric juice. 
 
Digestion in the Stomach. 163 
 
 8. The mucous coat of the stomach contains more blood during 
 digestion, and is more red, than when resting. 
 
 9. Pepsin in the gastric juice changes proteids to peptones. 
 
 10. The muscles of the stomach wall give a churning motion. 
 
 1 1 . The food is reduced to a thick liquid called chyme. 
 
 12. The stomach requires three or four hours to digest a meal. 
 
 Questions. i. Why is one more likely to choke if he thinks about 
 the process of swallowing? 
 
 2. What are the peculiarities of a cow's stomach? 
 
 3. What is the " rice ordeal " ? What can we learn from it? 
 
 4. Why do athletes eat sparingly before a game? 
 
 . 5. How does indigestion sometimes make one short-winded? 
 
 6. Why is it uncomfortable to hold the organs in the " swallowing 
 position"? 
 
 7. Why is it hard to swallow a pill ? Why take water with it? 
 
 8. Try swallowing repeatedly. Why is it difficult? 
 
 9. How is the structure of the windpipe favorable to swallowing? 
 10. Why is indigestion more noticeable in the stomach than later? 
 
CHAPTER XVII. 
 DIGESTION IN THE INTESTINE. 
 
 The Parts of the Intestine. The intestine consists of two 
 parts : first, the long and narrow small intestine ; second, 
 the short and wide large intestine. (See Fig. 76.) 
 
 The Small Intestine. The small intestine has essentially 
 the same structure as the parts of the digestive tube already 
 studied; namely, a muscular coat and a mucous lining. The 
 muscular coat has two layers, one of circular and the other 
 of longitudinal fibers. The muscular coat mixes the juices 
 with the food and moves it along. The muscular action 
 of the intestines is a slow writhing motion, called peristaltic 
 action. The mucous coat supplies mucus, which keeps 
 the surface soft and smooth. 
 
 The Liver. The liver is just under the diaphragm. It 
 is convex above, where it fits the hollow under surface of 
 the diaphragm, and hollow below, where it fits over the 
 upper surface of the stomach. The greater part of it is 
 on the right, as the greater part of the stomach is on the 
 left, side of the body. The liver is dark colored and of 
 very delicate structure, chiefly because it has very little 
 connective tissue. It is the largest gland in the body, 
 weighing nearly four pounds. 
 
 Bile. Bile is a bitter, golden red, or sometimes greenish 
 yellow, liquid made by the liver from the blood. About 
 two and a half pints of bile are made daily. 
 
 164 
 
Digestion in the Intestine. 165 
 
 The Bile Sac. This is a sac of about the size and shape 
 of a pear, and is attached to the under surface of the liver. 
 It has a duct, the bile duct, which empties into the small 
 intestine a few inches beyond the stomach. Part of the 
 
 Sublingual 
 I i vary Gland 
 
 Pancreas and 
 Duct 
 
 Receptacle of 
 
 Chyle 
 Lacteals 
 
 Mesentery 
 
 Intestine 
 Fig- 74. The Organs which change Food into Blood. 
 
 bile is at once poured out into the intestine, but part, 
 especially when we are not digesting, is stored in the bile 
 sac, to be poured out during digestion. 
 
 Functions of Bile. T. It aids in emulsifying the fats. 
 2. It aids in the absorption of fat 
 
1 66 Physiology. 
 
 3. The bile, to a certain extent, is waste matter; so the 
 liver is an organ of excretion as well as an organ of secretion. 
 
 4. It is found that if, for any cause, the bile is prevented 
 from entering the intestine, constipation follows, and the 
 contents of the large intestine have a much more fetid 
 odor than usual. The bile retards this putrefaction. 
 
 The Pancreas. Just back of the stomach is another im- 
 portant gland, the pancreas. It is a pink organ, weighing 
 three or four ounces and having the shape of a dog's 
 tongue. It has a duct which empties into the small intes- 
 tine at the same point where the bile enters, but it has no 
 sac in which to store the liquid which it secretes. It takes 
 from the blood certain materials and makes a liquid called 
 pancreatic juice. 
 
 Pancreatic Juice. This is a clear, sticky liquid, very 
 much like saliva in appearance. Although the pancreas is 
 a small organ, its work is very important. It gets a large 
 blood supply and makes a large amount of pancreatic juice. 
 The pancreas of calves is often eaten, being known by the 
 name "sweetbread." 
 
 The Work of the Pancreatic Juice. The pancreatic juice 
 acts on all the principal classes of foodstuffs : 
 
 1. A substance in it called amylopsin acts on starches, 
 changing them to sugar even more actively than the ptyalin 
 of the saliva. 
 
 2. Another substance in pancreatic juice is trypsin ; like 
 the pepsin of gastric juice, it changes proteids to peptones. 
 
 3. The pancreatic juice also emulsifies the fats. The 
 fat is divided into exceedingly fine drops, each covered 
 with a coating of albumen. An emulsion can be made 
 artificially by shaking together water, oil, and white-of-egg, 
 
Digestion in the Intestine* 167 
 
 The shaking breaks the oil into fine drops, which would 
 soon gather again if no other substance were present ; but 
 the albumen forms a thin coating around each droplet, 
 enabling it to remain distinct in the liquid. 
 
 The Intestinal Glands. The mucous membrane of the 
 small intestine has an immense number of tube-like glands. 
 (See Fig. 78.) Their structure is 
 much like that of the gastric glands 
 shown in Fig. 73. Fig. 75 shows 
 them as seen when cut across. 
 These glands make a liquid called 
 intestinal juice, which completes the 
 work of the other digestive liquids. 
 
 Review of Digestive Liquids. - 
 
 Saliva acts only on starch, gastric 
 juice on proteids, bile on fats; but 
 
 pancreatic juice acts on all three. the intestine, showing intestinal 
 
 Glands in Transverse Section. 
 mi. T T ^ T-i. (Highly magnified.) 
 
 The Large Intestine. This con- 
 sists mainly of the colon, the final portion being called the 
 rectum. 
 
 The Colon. The small intestine joins the colon near the 
 lower right side of the abdomen. Where the small intes- 
 tine enters the colon there is a valve which keeps the 
 material from coming back into the small intestine. The 
 colon runs upward on the right side (ascending colon), 
 crosses over to the left side (transverse colon), and descends 
 on the left side (descending colon), and, after curving some- 
 what like a letter S, becomes straight again, this part being 
 called the rectum. It is well to know the course of the 
 lower bowel, as pressure may be so applied as to push the 
 contents along in case the bowels become torpid. (Fig. 76.) 
 
i68 
 
 Physiology. 
 
 Gullet 
 
 Stomach 
 Duodenum 
 
 Review of the Digestive Tube. The whole digestive 
 tube may be briefly and roughly described as a muscular 
 
 tube of varying diameter, 
 lined by mucous mem- 
 brane. The muscular coat 
 pushes the contents along 
 and mixes them with liq- 
 uids; the mucous coat is 
 beset with glands, making 
 liquids, some of which 
 merely soak the food, 
 others act on it chemically, 
 | while mucus serves to 
 | make the surface slippery, 
 o It seems that these myriads 
 of simple glands are not 
 enough, so several large 
 compound glands lie along- 
 side the food tube and 
 empty their secretions into 
 it by ducts; these com- 
 pound glands are the sali- 
 vary glands, the pancreas, 
 
 Fig. 76. The Stomach and Intestines. an< 3 the liver. 
 
 Length of the Intestine. The length of the small in- 
 testine is about twenty-five feet, and of the large intestine 
 five or six feet. The large intestine is not a direct contin- 
 uation of the small ; that is, the small intestine opens at a 
 right angle into the large near the beginning of the latter, 
 so that there is a short blind end called the cecum (see 
 Fig. 76). In some animals this is large and has consider- 
 able length, but in man it is very short. There is a closed 
 
 Vermiform 
 Appendix 
 
 Rectum 
 
Digestion in the Intestine. 169 
 
 prolongation of the cecum, the vermiform appendix. This 
 appendix is frequently the seat of serious or fatal inflam- 
 mation, called appendicitis. This disease is not usually 
 caused by the lodging of seeds in the cecum, as most 
 people suppose ; still it is better not to swallow such things. 
 
 A Simple Gland. A gland is a structure which takes 
 liquid from the blood and pours it out on some surface. 
 In its simplest form a gland is a mere pit, or hole, such as 
 the gastric glands, shown in Fig. 73. The blood capilla- 
 ries give off lymph around the gland, and from this lymph 
 the cells of the gland take their material. A sweat gland 
 needs more length than a gastric gland, and the extra 
 length is coiled up in a ball at the inner end. Many 
 small glands are forked at their inner ends, thus increas- 
 ing their surface. 
 
 Kinds of Glands. Fig. 77 shows different forms of 
 glands, from the simplest to the most complex. In the 
 compound glands the lining of the duct, which is merely 
 a passageway, is different from the rest of the gland. 
 Glands that take waste matter from the blood are called 
 excretory glands, such as sweat glands ; they do not usu- 
 ally make much change in the material. Such glands as 
 the gastric glands change the material that they pour out; 
 the gastric juice is different from anything found in the 
 blood. Such glands are called secretory glands. Sweat is 
 an excretion ; gastric juice is a secretion. Still, all glands 
 are said to secrete, that is, to separate something from the 
 blood. And gland action in general is called secretion. 
 In structure, then, glands may be simple or compound. 
 In function they may be excretory or secretory. 
 
 Control of Glands. All glands are under the control 
 of nerves. But this control is involuntary, and under the 
 
 12 PHY 
 
1 70 Physiology. 
 
 management of the sympathetic nervous system. The 
 mouth may "water" for some attractive food, or become 
 dry through fear or anxiety. Hence we can see why a 
 restful, contented condition of mind and body will be 
 likely to favor the action of the many glands along the 
 digestive tube ; and, on the other hand, why anxiety or 
 fretfulness are likely to hinder their action. 
 
 Epithelium or Epidermis. 
 I 
 
 Compound Glands 
 Fig. 77. Simple and Compound Glands. 
 
 Summary. I . The intestine has two coats, an outer, muscular, and 
 an inner, mucous, coat. 
 
 2. The intestine consists of two parts, the small intestine and the 
 large. 
 
 3. The liver is the largest gland in the body. It secretes bile, which 
 is stored in the bile sac. 
 
 4. Bile aids in emulsifying and absorbing fats, and retards putre- 
 faction. Bile is partly waste matter. 
 
 5. The pancreas is a small tongue-shaped organ back of the 
 stomach. It secretes the pancreatic juice. 
 
Digestion in the Intestine. 171 
 
 6. Pancreatic juice acts on proteids, fats, and starch. 
 
 7. In the walls of the intestine are many small intestinal glands. 
 Their secretion helps complete the process of digestion. 
 
 8. The main part of the large intestine is the colon. It has three 
 parts, ascending, transverse, and descending. The last part of the 
 intestine is the rectum. 
 
 9. The small intestine is twenty-five feet long, the large, five or six. 
 
 10. A gland is a hollow structure that secretes a liquid from the 
 blood. 
 
 1 1 . Glands are simple, like an intestinal gland, or complex, like the 
 pancreas. 
 
 12. Glands are excretory, such as the sweat glands, or secretory, 
 such as the gastric glands. 
 
 Questions.' i. Why is there such a difference in the lengths of 
 intestine in the cat and the cow? 
 
 2. What is biliousness? 
 
 3. Why is the pancreas sometimes called the "abdominal salivary 
 gland 1 '? 
 
 4. Why does digestion proceed more slowly in the intestine than 
 in the stomach? 
 
 5. In what direction should the abdomen be rubbed to assist a 
 movement of the bowels? 
 
CHAPTER XVIII. 
 ABSORPTION. 
 
 Absorption a Living Process. The layer of cells which 
 forms the inner surface of the mucous membrane is called 
 epithelium. These cells are moist, soft, and thin-walled. 
 They take up the digested foods, now in liquid form, and 
 pass them on to the lymph and so into the blood capillaries 
 that are thickly distributed just beneath the surface. 
 
 Absorption from the Mouth. Sugar, and some other 
 substances, may be absorbed by the mouth as soon as it is 
 dissolved. But very little material is thus absorbed. 
 
 Absorption from the Stomach. Some parts of the food 
 that are already digested, or such matters as are soluble, 
 e.g. water containing sugar, peptone, salts, etc., may be 
 absorbed immediately through the walls of the stomach 
 into the blood capillaries. Recent experiments show, how- 
 ever, that the amount of absorption from the stomach is 
 much less than was formerly supposed; water, for instance, 
 " when taken alone, is practically not absorbed at all in the 
 stomach. As soon as water is introduced into the stomach 
 it begins to pass out into the intestine, being forced out in 
 a series of spurts by the contractions of the stomach." 
 
 Absorption from the Small Intestine. Most of the 
 digested food is absorbed in the small intestine. 
 
 Increased Surface for Absorption. The mucous mem- 
 brane of the small intestine is thrown into ridges, but, 
 unlike those of the stomach, they run crosswise. Again, 
 
 172 
 
Absorption. 
 
 173 
 
 Villuses 
 
 while the folds in the lining of the stomach are temporary, 
 these are permanent. They increase the surface of the 
 lining and retard the passage of the food material, and so 
 aid the process of digestion and of absorption. 
 
 Villuses. To increase, still further, the surface for 
 absorption, the mucous membrane of the small intestine is 
 
 thickly covered with 
 little cylindrical pro- 
 jections, like the 
 "pile" on velvet. 
 Each of these pro- 
 jections is a villus. 
 
 Intestinal Glands ^B 
 
 Structure of a Vil- 
 lus. A villus is 
 about a thirtieth of 
 an inch long. It is made up of four parts : ( I ) on the out- 
 side a layer of soft, moist, thin-walled cells; (2) plain 
 muscle fibers, running lengthwise ; (3) a network of blood 
 
 Fig. 78. Mucous Membrane of Small Intestine, showing 
 Intestinal Glands and Villuses, greatly Magnified. 
 
 Lacteal with Valves Capillaries Muscles Epithelium 
 
 Fig. 79. Four Parts of a Vilius, greatly Magnified. 
 
 capillaries ; and (4), near the center, lymph capillaries, 
 called lacteals. Fig. 79 shows these four parts separate, 
 while Fig. 80 shows them combined, as they are in the 
 complete villus. 
 
1 74 Physiology. 
 
 Absorption by the Villuses. The digested food is in 
 liquid form and surrounds the villuses. The three main 
 substances to be absorbed are peptones, sugar, and fat. 
 The outer cells of each villus absorb these and pass them 
 inward. The peptones and sugars are taken into the blood 
 capillaries, while the fats enter the lacteals. 
 
 Muscular Action of the Villuses. In each villus there 
 are plain muscle fibers. When these shorten they squeeze 
 the chyle, that has already been absorbed, into the lymph 
 tubes of the wall of the intestines, and on into the main 
 
 Epithelial Covering 
 
 Lacteal 
 
 Longitudinal Mus- 
 cular Fibers 
 Capillary Network 
 
 Fig. 80. A Complete Villus, very greatly Magnified. 
 
 lymph duct. The chyle cannot return to the lacteal when 
 the muscles relax, on account of the valves, similar to 
 those of the veins, in the lacteal at the base of the villus. 
 Then, when the muscles relax, the lacteal is empty, and 
 ready to absorb more of the emulsified fat that we call 
 chyle. This action also helps the flow in the blood 
 capillaries. 
 
 The Lacteals and Lymphatics. While the main work 
 of the lymphatics, as we have seen, is the carrying of 
 lymph from the tissues of the body to empty into the 
 veins of the neck, the lymphatics of the intestines have 
 another important function. They absorb and carry the 
 fatty portions of the digested food into the general circu- 
 lation. During most of the time the thoracic duct and 
 
Absorption. 
 
 175 
 
 the lymphatics of the intestines would hardly be noticed 
 because they are filled with the clear lymph. But after 
 
 Right Lymph Vein 
 
 Junction of Thoracic 
 Duct with LeftSub- 
 clavian Vein 
 
 Main Lymph Vein 
 (Thoracic Duct) 
 
 Intestine 
 
 Lymphatic Glands 
 
 Fig. 81. Lymph Veins (Lymphatics). 
 
 absorption of fatty matter they are filled with a white 
 liquid, called chyle, and are easily seen. (See Fig. 81.) 
 
 The Portal Circulation. All the veins coming from the 
 stomach and intestines unite to form a large vein that goes 
 to the liver ; this is the portal vein. When the portal vein 
 enters the liver it does what veins do not do elsewhere in 
 the body, it divides into smaller branches. This division 
 
i 7 6 
 
 Physiology. 
 
 and subdivision goes on till the portal vein forms capil- 
 laries branching all through the liver. 
 
 The blood from these capillaries collects again in veins, 
 which unite in one vein, the hepatic vein, which carries 
 the blood into the postcaval vein just under the diaphragm. 
 
 Fig. 82. Diagram of Portal Circulation. 
 
 Going back again to the beginnings of the portal vein, 
 it is clear that it starts from the capillaries of the stomach 
 and intestines. And these capillaries, as we have just seen, 
 absorb the peptones and sugars. The sugars and peptones, 
 therefore, go directly to the liver after being absorbed. 
 
 Double Blood Supply to the Liver. The liver also re- 
 ceives blood from the hepatic artery, a branch of the aorta. 
 
Absorption. 
 
 177 
 
 Thus the liver gets blood from two sources, the portal vein 
 and the hepatic artery, but is drained by one vein, the 
 hepatic vein. 
 
 Work of the Liver. We have seen that the liver makes 
 bile. The liver also makes another substance out of the 
 blood that passes through it. This is glycogen, or "animal 
 starch." It is also called "liver sugar," as it gives to liver 
 
 Portal Vein 
 
 Mesenteric 
 
 Blood Veins 
 
 (Albumen, 
 
 Sugar) 
 
 Capillaries 
 
 Fig. 83. Plan of Absorption. 
 
 a sweetish taste. Glycogen is given back to the blood and 
 carried away by the hepatic vein to the body, where it 
 serves as food to the tissues. 
 
 Routes of Different Foods after Absorption. There are, 
 then, two routes taken by the food after absorption. The 
 peptones and sugars go to the liver through the portal 
 
i 7 8 
 
 Physiology. 
 
 vein, while the fats are carried by the main lymph duct, or 
 thoracic duct. These two streams unite before reaching 
 the heart. The fats pass around the liver, instead of 
 through it as do the peptones and sugars. 
 
 PARTS 
 OF 
 DIGESTIVE 
 TUBE. 
 
 MECHANI- 
 
 GLANDS. 
 
 LIQ- 
 UIDS. 
 
 CHEMICAL 
 CHANGE. 
 
 ABSORPTION. 
 
 CAL PRO- 
 CESSES. 
 
 MATERIAL 
 
 BY 
 
 MOUTH. 
 
 Cutting 
 and 
 Grinding. 
 
 Salivary. 
 
 Saliva. 
 
 Starch 
 to 
 Sugar. 
 
 
 
 PHARYNX. 
 
 Raising Soft 
 Palate. 
 Depressing 
 Epiglottis. 
 
 
 
 
 
 
 GULLET. 
 
 Food carried 
 to Stomach. 
 
 Mucous. 
 
 Mucus. 
 
 
 
 
 STOMACH. 
 
 Churning 
 and 
 Mixing. 
 
 Gastric. 
 
 Gastric 
 Juice. 
 
 Proteid 
 to 
 Peptone. 
 
 Water. ] 
 Salts. 1 
 Sugars. j 
 Peptones. J 
 
 Blood 
 Capillaries. 
 
 SMALL 
 INTESTINE. 
 
 Mixing 
 and 
 Moving 
 Food. 
 
 Liver. 
 Pancreas. 
 
 Intestinal. 
 
 Bile. 
 Pancreatic 
 Juice. 
 Intestinal 
 Juice. 
 
 ( Starch to Sugar. 
 j Proteid to Peptone. 
 j p t Emulsified. 
 L ' Decomposed. 
 
 Water. ] 
 Salts. [ 
 Sugar. 1 
 Peptone. ! 
 Fats. 
 
 Blood 
 
 Capillaries. 
 
 Lacteals. 
 
 LARGE 
 INTESTINE. 
 
 Food 
 Forced on. 
 
 Mucous. 
 
 Mucus. 
 
 
 Water. 
 
 
 Fig. 84. Outline of Digestion and Absorption. 
 
 Amount of Liquid Absorbed. It is estimated that there 
 is poured into the digestive tube daily one quart of saliva, 
 four or five quarts of gastric juice, one quart of bile, and 
 about a quart of pancreatic juice. If the food and drink 
 amounts to two quarts, there must be more than two gal- 
 lons of liquid absorbed from the digestive tube each day. 
 
Absorption. 1 79 
 
 The Work of the Large Intestine. Most of the ab- 
 sorption is accomplished in the small intestine ; but as the 
 food passes on into the large intestine the work of digestion 
 and of absorption is carried somewhat farther. If the 
 residue be not soon expelled, there may be absorption of 
 some of the results of putrefactive changes, and a sort 
 of general poisoning of the whole body. Hence the 
 great importance of regularly and thoroughly emptying 
 the lower bowel. The matter thus expelled is largely 
 made up of indigestible material, with some real waste 
 substances. 
 
 Taking up again our comparison of the body and a 
 stove, we see that the feces are not true waste products, 
 but are rather clinkers, or material that has not been 
 burned or oxidized in the body. The real wastes of the 
 body are the carbon dioxid, urea, water, etc., that are pro- 
 duced by the oxidation of the tissues, and are mostly thrown 
 off by the lungs, kidneys, and skin. 
 
 Summary. i. The cells lining the digestive tube take up the 
 digested food, now in liquid form, and pass it into the lymph. 
 
 2. There is some absorption, from the stomach, of sugar and 
 peptone. Most of the absorption is from the small intestine. 
 
 3. The hair-like villuses greatly increase the absorbing surface. 
 
 4. A villus has four parts, the outer layer of cells, plain muscle 
 fibers running lengthwise, blood capillaries, and lacteals. 
 
 5. The outer cells of the villus take up the liquefied food. 
 
 6. Sugar and proteids enter the blood capillaries; fats enter 
 the lacteal capillaries. 
 
 7. The muscles of the villus pump the liquids along and aid 
 absorption. 
 
 8. The lacteals are part of the lymph system of the body. They 
 absorb and carry fats. 
 
 9. The veins from the stomach and intestine join to form the por- 
 tal vein which enters the liver. Here it breaks up into capillaries. 
 
180 Physiology. 
 
 10. The liver has two supplies of blood, from the portal vein and 
 the hepatic artery. It is drained by one vein, the hepatic vein. 
 
 11. The liver makes bile and glycogen. 
 
 12. Sugars and proteids go through the liver; fats pass around the 
 liver through the main lymph vein, or thoracic vein. 
 
 13. There are over two gallons of liquids absorbed daily. 
 
 Questions. i. Why is it best to begin a hearty meal with soup ? 
 
 2. Why should the liver receive so much blood ? 
 
 3. What is the meaning of " biliousness " ? 
 
 4. What is the advantage of a " fruit diet " ? 
 
 5. Why does active exercise tend to keep the bowels open? 
 
CHAPTER XIX. 
 HYGIENE OF DIGESTION. NUTRITION. 
 
 Digestion and Circulation. During digestion there must 
 be a large supply of blood in the digestive organs. It is 
 needed both to supply the material for the glands to make 
 the digestive liquids and also to absorb and bring away the 
 newly digested food. Therefore, during digestion there 
 must be less blood in other parts of the body. 
 
 Digestion and Muscular Work. If one exercises actively 
 immediately after eating, the process of digestion will be 
 interfered with, because the blood will be drawn away 
 from the digestive organs to the muscles. It is well to 
 rest for a short time after eating a full meal. 
 
 Digestion and Study. For the same reason it is better 
 not to begin hard study immediately after a full meal. The 
 blood needed for the work of digestion will be called to the 
 brain, and digestion will suffer. 
 
 Solid Foods digest Slowly. If a very hungry person 
 begins his dinner with solid food, he is likely to eat too 
 fast. Hunger is a demand of the system for food. It 
 takes some time for solid food to go through all the pro- 
 cesses of digestion, and be absorbed into the system and 
 satisfy hunger. 
 
 Value of Soup. But if the meal begins with soup, which 
 is readily absorbed, the demand of the system will begin to 
 be met, and there will not be the same tendency to rapid 
 
 181 
 
1 8 2 Physiology. 
 
 eating. Further, a warm soup stimulates the blood flow in 
 the mucous membrane, and thus prepares for more thorough 
 digestion. 
 
 Desserts. Dessert and sweetmeats, following a meal, 
 are often helpful by further stimulating the secretion of the 
 glands. Nuts, which are not very digestible, are beneficial 
 if eaten sparingly. The agreeable taste stimulates the 
 salivary glands, and the saliva stimulates the gastric glands 
 to increased activity. The danger in taking dessert is that 
 the pleasing taste tempts us to continue eating after we 
 have had enough. Pie is usually hard to digest. 
 
 The Bad Effects of Imperfect Mastication. If we swallow 
 food before it is thoroughly ground and mixed with the 
 saliva, the stomach and other parts of the digestive organs 
 will require much more time to reduce the food to a liquid 
 form. Further, when eating hastily, we are very apt to 
 eat too much. Thus we may give the stomach a double 
 amount of material to handle, and the material may not be 
 half so well prepared as it should be. Of course the organs 
 suffer and break down if this treatment is continued. 
 
 Effect of Repose on Digestion. Not only mastication, but 
 the whole process of digestion, goes on better when the 
 body and mind are at rest and in a peaceful condition, as 
 all the glands are under the control of the nervous system, 
 and are greatly influenced by the condition of the body. 
 During a meal, and for a short time before and after, all 
 thoughts of one's occupation, and especially all anxiety, 
 should be dismissed from the mind. For those whose 
 digestion is not strong, it is desirable to rest after each 
 meal. 
 
 Conversation at Meals. During a meal there should be 
 conversation on topics of general interest. Talking at the 
 
Hygiene of Digestion. 183 
 
 table also makes us more deliberate in eating. " Chatted 
 food is half digested." 
 
 Time of Eating. The American custom of three meals 
 a day seems well adapted to the needs of our people. The 
 best time for the chief meal is near the middle of the day, 
 as is the custom in the country ; for the bodily powers are 
 higher than later in the day. But for city people, and 
 others who are very busy in the middle of the day, it is 
 undoubtedly better to take the chief meal after the rush of 
 the day's work is over, when there is time for a deliberate 
 meal and when the mind is free from business cares. In 
 many homes this is the only time when the whole family 
 can leisurely meet at the table. 
 
 Eating between Meals. The stomach should have time 
 to rest and prepare for the work of digesting another meal. 
 Many find two meals a day sufficient. There are some 
 persons, however, for whom it would be better to have 
 more meals, with less food at a time. Meals should be 
 regular. 
 
 Amount of Food Needed. This varies greatly with the 
 individual, age, the kind and amount of labor, etc., so that 
 no very helpful rule can be given. Each person must find 
 by experience what is best for himself. It is the opinion 
 of many leading physicians that the majority of mankind 
 eat too much. 
 
 Intemperance in Eating. "I have come to the conclu- 
 sion that more than half of the disease which embittei s the 
 middle and latter part of life is due to avoidable errors of 
 diet ; and that more mischief, in the form of actual disease, 
 of impaired vigor, and of shortened life, accrues to civilized 
 man from erroneous habits of eating than from the habitual 
 
184 Physiology. 
 
 use of alcoholic drink, considerable as I know that evil to 
 be." - - Thompson. 
 
 Self-denial in Eating. It is a good old saying, " We 
 never repent having eaten too little." Nearly every one 
 has regretted having eaten too much. It is better to 
 stop before one has eaten quite as much as he would 
 like, especially when taking highly-seasoned or sweetened 
 food. 
 
 Fat as a Tissue. As a tissue fat serves as a stored-up 
 food. A fat person can endure starvation longer, other 
 things being equal, than a thin person. A layer of fat 
 under the skin serves also as a heat saver. 
 
 Hibernation. Hibernating animals are fat when they enter upon 
 their winter sleep, but are lean when they come out in the spring. 
 Remaining inactive, they have produced very little energy, their only 
 motions being a slow and feeble breathing and heart-beat. They have 
 consumed the fat, using it mainly in maintaining the necessary heat. 
 In short, they have burned their fat to keep them warm. 
 
 Importance of Renewal of Blood and Lymph. The 
 
 lymph surrounds the individual cells which make up the 
 tissues of the body. Every cell lives an independent life, 
 to a certain extent, taking its nourishment directly from 
 the lymph around it. The importance of an abundant 
 supply of good lymph is apparent. The supply and renewal 
 of the lymph depends on the blood. 
 
 Effect of Digestion on Blood and Lymph. If digestion is 
 not good, or if there is not enough good food, good blood 
 cannot be made, and the lymph will not be good. The 
 cells are more or less starved, or poisoned if wastes are not 
 properly removed, and the general tone of the body will 
 soon be lowered; for the health of tLe body as a whole 
 depends on the average condition of the cells composing 
 
Hygiene of Digestion. 
 
 i8 5 
 
 the body, just as the condition of any community depends 
 on the average condition of the individuals of that com- 
 munity. 
 
 Assimilation. The formation of tissue from the mate- 
 rials brought by the blood is assimilation. It is the last 
 step in building up the tissues. 
 
 Capillaries 
 
 Vein 
 
 Arteiy 
 
 Vein 
 
 Capillaries 
 Fig. 85. Diagram of the Heart and Blood Tubes (Back ViewV 
 
 Blood a Mixture of Good and Bad. In the blood streams 
 are combined the good and the bad. The newly digested 
 food is received into a current of impure blood in the post- 
 13 PHY 
 
86 
 
 Physiology. 
 
 caval vein. The blood from the kidneys, probably the 
 purest blood in the body, joins the same impure stream. 
 From the aorta, red blood, usually called pure, the same 
 
 Lung Capillaries 
 
 r 
 
 Pulmonary Vein 
 
 Body Capillaries 
 
 Fig. 86. Plan of Circulation, representing the Right and Left Halves of the Heart sepa- 
 rated, showing that the Blood makes but One Circuit. 
 
 kind that goes to the brain, is sent to the kidneys and to 
 the skin to be purified. Yet, as this mixed blood flows 
 through each organ, that organ, so long as it is in health, 
 takes from it only what it should take. 
 
Hygiene of Digestion. 187 
 
 Action of Diseased Kidneys. The kidney takes, during 
 health, only the waste matters, leaving the valuable nour- 
 ishing material. But, in disease, the kidneys may take out 
 some of the most valuable nourishing material. Suppose 
 that in a mill, a workman, whose business is to shovel out 
 wastes, becomes crazy, and shovels wheat or flour out of 
 the mill into the stream below. The diseased kidney may 
 be said to have become crazy, and in the disease called 
 " diabetes " throws out sugar, and in " albuminuria " ex- 
 cretes albumen. 
 
 Blood Streams like Water Pipes and Sewer Combined. 
 It is as though the water supply of a city house was taken 
 from the sewer ; each organ needing a supply of building 
 material acts like a filter, taking from the blood what it 
 needs, paying no attention to the impurities present, and 
 the organs of excretion select the impurities, allowing the 
 useful substances to pass on to the places where they are 
 needed. Figs. 85, 86, and 87 show what the blood stream 
 gives to each of the organs of the body and what it takes 
 from them to throw out as waste matter. 
 
 How the Body Changes. The body is continually 
 changing, new material from the digested food taking the 
 place of the worn-out tissues. It is a common saying that 
 the body changes once in- seven years. But while the 
 more active tissues, such as muscle, must change many 
 times in a year, we know that the teeth do not grow after 
 they are once formed. 
 
 The Body like an Eddy. The changes in the body have 
 been compared to an eddy in a stream. The form of the 
 eddy remains the same, while particles of water are enter- 
 ing on one side and leaving on the other. In a short time 
 
1 88 Physiology. 
 
 all the particles are changed. But in the body the more 
 permanent parts change slowly. 
 
 Nutrition. Nutrition includes all the changes that take 
 place in the body from the reception of food to the excre- 
 tion of the waste matter. It includes digestion, absorption, 
 circulation, assimilation, respiration (oxidation), and excre- 
 tion. The first four of these processes are stages in build- 
 ing tip the tissues ; the last two are process of tearing doivn. 
 
 We cannot destroy Matter. When a stick of wood is 
 burned it is no longer wood. But the matter is not de- 
 stroyed. It could all be obtained again from the smoke 
 and ashes. So, in the continual wasting away of our 
 bodies, there is no real loss of matter. Our weight is re- 
 duced, but the wastes are still part of the earth or the air, 
 and are of use in the world. We are as unable to destroy 
 matter as we are to create it. 
 
 The Ceaseless Round of Matter. A particle of carbon 
 in the carbon dioxid of the expired breath may be taken in 
 by a blade of grass. A cow eats the grass, and we may 
 before long take the very same particle of carbon in the 
 milk or the flesh of the cow. Or the particle of carbon 
 may become part of a grain of wheat, and be made into 
 flour and be eaten as bread and be a part of the body 
 once more. Thus, there is a- ceaseless round of matter 
 into and out of our bodies. No one has a monopoly of 
 any portion of matter ; it is now ours, now some one else's. 
 
 We cannot create Force. We get our energy from the 
 food we eat, just as an engine gets its energy from fuel. 
 This is saying nothing against the superiority of the 
 human body and is not in the least degrading. We are 
 living, growing, self -directing, and self -maintaining ma* 
 
Hygiene of Digestion. 189 
 
 PULMONARY VEIN 
 
 LEFT AURICLE 
 
 LEFT VENTRICLE 
 
 PULMONARY ARTERY 
 
 RIGHT VENTRICLE 
 
 RIGHT AURICLE 
 
 * 
 
 Fig. 87. The Circulation and the Work of the Blood 
 
i go Physiology. 
 
 chines. Still, starvation soon puts an end to our ability 
 to produce energy of any kind. 
 
 How we depend on Plants. The larger part of our food 
 is vegetable. And the animal foods, such as meat, milk, 
 cheese, butter, eggs, etc., were made by the animals from 
 vegetable matter. We are, therefore, directly or indirectly, 
 dependent on plants for all our food. On the other hand, 
 plants use as their food considerable of the waste matter 
 thrown off by animals. 
 
 Summary. i . During digestion a large supply of blood is required 
 in the digestive organs. 
 
 2. Muscular work, immediately after eating, interferes with digestion 
 by calling the blood away to the muscles. 
 
 3. Hard study, right after a hearty meal, hinders digestion- in the 
 same way. 
 
 4. Soup is a good beginning of a hearty meal, as it is more readily 
 absorbed than solid food. 
 
 5. Desserts, in moderate quantity, are useful in stimulating the 
 glands which supply the digestive liquids. 
 
 6. Hot drink at meals aids weak digestion. 
 
 7. Imperfect mastication leads to eating too much, and throws too 
 much work upon the other organs of digestion. 
 
 8. A calm condition of the nervous system favors digestion. 
 
 9. Conversation on cheerful topics is favorable to digestion. 
 
 10. Three meals a day are best for most persons. 
 
 1 1 . For persons hurried in the middle of the day it is often better 
 to take the chief meal at the close of the day's work. 
 
 12. Meals should be regular, and one should not eat between meals. 
 
 13. There is much intemperance in eating. 
 
 14. Fat, as tissue, is stored food. 
 
 15. The cells depend on the lymph for their nourishment, and the 
 lymph is supplied by the digested food. 
 
 1 6. The blood is a mixture of good and bad material; each organ, 
 in health, selects from the blood what it needs, the tissues taking 
 nourishment, and the organs of excretion removing the waste 
 matters. 
 
Hygiene of Digestion. 191 
 
 17. Diseased kidneys may remove valuable nourishing materials 
 from the blood. 
 
 1 8. The body keeps changing, taking new matter to replace worn- 
 out tissue. 
 
 19. Nutrition includes digestion, absorption, circulation, respiration, 
 assimilation, oxidation, and excretion. 
 
 20. We cannot destroy matter. Our waste products become part 
 of earth or air. 
 
 21. We cannot create force. We get our energy from food as an 
 engine gets its energy from fuel. 
 
 22. We depend on plants for our food. 
 
 Questions. i . Should a person who has studied hard try to do hard 
 muscular work the same day ? 
 
 2. What are the advantages of a "course" dinner? 
 
 3. Which is more wholesome, dry toast or soaked toast? Why? 
 
 4. Why do we give a horse exercise and keep fattening stock quiet? 
 
 5. Are fat people large eaters ? Are thin people light eaters? 
 
 6. Do sweat glands ever excrete valuable material ? 
 
 7. In Fig. 87 find what the blood gives to each organ and what it 
 takes from each. 
 
 8. Classify the organs represented in Fig. 87. 
 
 9. Name the organs that change most rapidly. 
 
 10. Name the organs that change most slowly. 
 
 1 1 . What is the source from which plants get their energy? 
 
 12. Is matter defiled in passing from one body to another? 
 
CHAPTER XX. 
 EXERCISE AND BATHING. 
 
 How Exercise is Beneficial. Exercise stimulates the 
 cells to activity and renews the lymph around the cells 
 both by quickening the blood flow and by pressure on the 
 lymph tubes. The glands of excretion are set to work 
 more actively, and the more rapid blood stream brings 
 away the material to be thrown out. 
 
 Exercise for General Health. Exercise is not merely 
 for the muscles. It quickens the action of the whole body 
 by increasing cell activity. It helps clean out the system 
 and clear the brain as well. It is not so much strength as 
 health that we need. The ability to do our daily work, to 
 do it with comfort and without any feeling of strained 
 effort, is what we need. 
 
 Exercise prolongs Life. Many men would live longer, 
 feel better, and do greater good in the world, if they took 
 regular and systematic exercise. It is a shortsighted 
 policy to say, "I cannot afford the time." Not to take 
 time for exercise is to mortgage one's future. " He who 
 does not take time for exercise will have to take time for 
 illness." The latter half of every person's life ought in 
 many respects to be by far the most productive of good. 
 But many cut off this half, or render it less useful through 
 breaking down in health as a result of violating the laws 
 of health. 
 
 192 
 
Exercise and Bathing. 193 
 
 Nature's Rewards and Punishments. Nature never 
 fails to punish every violation of her laws. Her reward 
 for obedience is health and the delight that accompanies it. 
 
 Useful Exercise. The man, woman, boy, or girl who 
 has regular work that calls for muscular activity is to be 
 congratulated. Duty obliges them to take regular exer- 
 cise. The boy who has " chores " to do is to be envied 
 rather than pitied. 
 
 Choice of Exercise. But many persons are so situated 
 that they have no work to do. They must choose some 
 exercise that is not for a directly useful purpose. In se- 
 lecting exercise one should choose (i) that which is enjoy- 
 able, for exhilarating exercise is much more beneficial than 
 that which is taken as a necessity ; (2) exercise should be 
 in the open air whenever possible. 
 
 Forms of Exercise. There is a great variety of forms 
 of exercise from which each person can select according 
 to his age, strength, etc. For active youths there are run- 
 ning, jumping, wrestling, boxing, fencing, hare and hounds, 
 putting the shot, putting the hammer, vaulting, baseball, 
 and football. In their season come boating and swim- 
 ming, skating and coasting. Suitable for both boys and 
 girls are archery, basket ball, bicycling, croquet, golf, 
 horseback riding, tennis, and last, but not least, walking. 
 The main trouble with walking is that it is likely to be 
 taken from a sense of duty and becomes mechanical. 
 The good feature of most games is that there is active 
 competition, which makes them so enjoyable that one en- 
 tirely forgets his work for the time. He is, therefore, in 
 better condition to return to his work. 
 
 Exercise in One's Room. In one's room he can use 
 dumb-bells or Indian clubs to good advantage. There are 
 
1 94 Physiology. 
 
 also various forms of " home exercisers," such as pulley 
 weights, rubber bands, etc., which are valuable. After 
 exercise should come a sponge bath. 
 
 Games of School Children. Most of the games of school 
 children are excellent kinds of exercise. Cases have been 
 reported of injury from excessive skipping the rope ; but 
 in moderate degree it is a good exercise. Tag, snowballing, 
 racing, the various games of ball, jumping, hopping, and 
 other games may be played on the school grounds. 
 
 Tennis. Tennis is a fine game and suitable for girls as well as boys. 
 It has the great advantage over baseball that it does not require a large 
 ground. Two can make-up a game, 'and a little time can be better used 
 than with the games requiring more players. The exercise, too, is more 
 evenly distributed. There is no long waiting, as in some games, but a 
 constant interchange of play, active but not severe, with almost no danger 
 of injury. 
 
 Baseball and Football. For those who can pursue the more vigor- 
 ous games of baseball and football they are admirable. All these games 
 calling for great activity and strength develop manly qualities in boys, 
 and do much to make them active, fearless men, men who in time of 
 danger have not only strength and endurance, but well-trained muscles, 
 cool heads, and brave hearts ; men who know what to do and how to 
 do it in an accident, as at fires, upsetting of boats, etc. A few strong, 
 cool-headed men, by their presence of mind, often stop a panic and save 
 many lives when there is an alarm of fire, which often proves false. The 
 Duke of Wellington said that it was on the football fields of Eton and 
 Rugby that the battle of Waterloo was won. 
 
 Boxing. Boxing is a splendid exercise. It calls into play nearly 
 every muscle of the body. Boxing makes one quick on his feet, trains 
 to quick movements of the arms, trains the eye, keeps the body in an 
 erect position, and especially develops the muscles of the legs and back. 
 Boxing brings out the chest and shoulders. It develops the "wind," 
 and keeps one in constant action. It teaches control of the temper 
 more than almost any form of exercise. It develops a degree of self- 
 reliance that is worth much. Like tennis, boxing calls for little appa- 
 
Exercise and Bathing. 195 
 
 ratus, little space, and only two persons. In many places where ordinary 
 gymnasium work is out of the question, boxing is available. It is indeed 
 a " manly art," and the doctrine taught in Tom Brown's School Days at 
 Rugby is as wholesome as can be given to boys to make them strong and 
 active, to give them physical and moral health. 
 
 Bicycling. This is an excellent exercise, as it is in the open air and 
 exhilarating. There is danger of over-exertion, and it is bad for one to 
 yield to the temptation to make long runs. There is danger of over- 
 taxing the heart. The handle bar should be adjusted to allow a fairly 
 upright position. The saddle should be such as to sustain the weight 
 properly. 
 
 "Taking Cold. " So long as one is actively exercising, 
 he is not likely to take cold. But if one rests in a cool 
 place, especially when he is warm, he is likely to take cold. 
 The application of cold to the skin causes the arteries 
 (through reflex action) to become smaller. Thus when rest- 
 ing in a cool place the skin becomes pale and cold. Dur- 
 ing a " cold " there is fever. The regulation of the. heat by 
 the skin is interfered with. Waste matter is not given off 
 by the skin as it should be. At the same time it is often 
 noticeable that the urine is more abundant than usual. A 
 cold is often associated with constipation and inactivity of 
 the liver, indicating a clogged condition of the system. As 
 a cold may lead to fatal lung disease, so it may be the 
 beginning of disease of the kidneys that may, in the end, 
 bring fatal results. 
 
 Bathing. One purpose of bathing is to cleanse the 
 skin. For this purpose warm water is best, and it is desir- 
 able to use soap, especially on those parts which are espe- 
 cially exposed to contamination, such as the hands, the 
 feet, the armpits, and groins. The feet should be bathed 
 every night 
 
196 Physiology. 
 
 Cold Baths. Another important function of bathing is 
 to strengthen the system. For this purpose cold bathing 
 is better, but this should not be too long continued, and 
 must be followed by a brisk friction to give the skin a ruddy 
 glow. For this kind of bath a tub is not necessary, and 
 hardly desirable. The water may be quickly applied by 
 means of a sponge, or bath mits made of Turkish toweling, 
 and the body thoroughly rubbed with a coarse towel. The 
 whole process should be completed very quickly, especially 
 if the room is not warm. At the beginning of a bath, cold 
 water should be applied to the head and face. 
 
 Time for Bathing. For those who do not take a great 
 deal of vigorous exercise, which keeps the skin active, 
 bathing is especially valuable. The use of warm water 
 for cleansing seems best adapted to the time of going to 
 bed. But the best time for the cool bath is on getting up 
 in the morning. 
 
 Warm Baths vs. Cold Baths. Prolonged warm baths 
 are weakening, and probably increase a tendency to take 
 cold, whereas cold bathing is one of the very best means 
 of fortifying against cold, and especially against the ten- 
 dency to take cold on slight exposure. For most persons 
 a cool sponge bath, on rising, will act as a most excellent 
 tonic ; but if it seems to produce neuralgia, it should be 
 used with caution. 
 
 Exercise of Arterial Muscles. We have learned that 
 the blood supply to any organ is regulated by the action 
 of the plain muscle fibers in the walls of the small arter- 
 ies. Now, when we are subject to changes in temperature 
 these muscles get exercise, and one writer has well called 
 the cold bath the gymnastics of the plain muscle fibers, 
 
Exercise and Bathing. 197 
 
 and we can understand how the system can be trained to 
 adjust itself to cold, and enabled to avoid "taking cold." 
 
 Habit of Cold Bathing acquired Gradually. There are 
 undoubtedly many persons who do not profit by cold bath- 
 ing, but probably many of these would soon adapt them- 
 selves to it by beginning with tepid water and gradually 
 using cooler. To bath slowly in a cold room is not safe. 
 The great secret of the benefit that may be expected from 
 a cold bath is to be very brisk, the whole process occupying 
 only a few minutes. Many are opposed to cold sponge 
 bathing, and condemn it without giving it a fair trial. 
 
 Summary. i. Exercise stimulates the activity of all the organs, by 
 promoting cell activity and assisting excretion. 
 
 2. Exercise should be in the open air as much as possible. 
 
 3. Exercise is more beneficial when it exhilarates. 
 
 4. Exercise should be taken regularly. 
 
 5. Warm baths are best for cleansing, and should be taken at bed- 
 time. 
 
 6. Cold baths stimulate the circulation of blood in the skin, and 
 serve as a tonic to the whole system. Just after rising is a good time 
 for the cold bath. 
 
 7. The cold bath fortifies against taking cold. 
 
 Questions. i. Should exercise be carried to the point of fatigue ? 
 
 2. How can one avoid taking cold after exercise ? 
 
 3. Do girls need exercise as much as boys ? 
 
 4. What is the condition of the body during a " cold" ? 
 
 5. How may a cold be caused ? 
 
 6. How may a cold be cured ? 
 
 7. How may a cold be prevented ? 
 
 8. Why do some persons take cold more readily than others ? 
 
 9. Why does the same person take cold more readily at one time 
 than at another ? 
 
 TO. How often should a person bathe ? 
 
 1 1 . What hour is best for sea bathing ? Why ? 
 
CHAPTER XXI. 
 THE BRAIN. 
 
 The Coverings of the Brain. There are two coats of 
 
 the brain, the dura mater, a tough membrane, adhering to 
 the inside of the skull; and the pia mater, next to the 
 brain, a much thinner membrane, traversed by blood 
 tubes, and dipping down into the grooves between the 
 convolutions of the cerebrum. 
 
 The Parts of the Brain. The parts of the brain are the 
 cerebrum, the cerebellum, and the spinal bulb. 
 
 The Cerebrum. The cerebrum consists of two lateral 
 hemispheres, separated by a deep groove in the middle 
 line. The surface of the cerebrum is in irregular ridges, 
 the convolutions. The outside of the brain consists of 
 gray matter. The inner part of the brain is white, and 
 the two halves are connected by a broad band which con- 
 sists of many white fibers. 
 
 The Cerebellum. Back of, and below the cerebrum is 
 the cerebellum. It is much smaller than the cerebrum, 
 and has fine transverse ridges and grooves in place of the 
 convolutions of the cerebrum. It is also of a deeper color, 
 a reddish gray. 
 
 The Spinal Bulb. The enlarged beginning of the 
 spinal cord is the spinal bulb. It is white, like the rest of 
 the cord. 
 
 198 
 
The Brain. 
 
 199 
 
 The Cranial Nerves and their Functions. i. The 
 olfactory lobes extend forward under the fore part of the 
 cerebral hemispheres. They are the nerves of smell. 
 
 I, Olfactory 
 (Smell) 
 
 Eye Motor, 
 3,4,6 
 
 Hypoglossal, 
 12 (Tongue 
 Motor) 
 
 II, Spinal 
 Accessory 
 
 Fig. 88. The Base of the Brain, showing the Origin of the Cranial Nerves. 
 
 2. The optic nerves, or nerves of sight, join each other 
 before reaching the brain. 
 
 3. The third pair of cranial nerves controls part of the muscles of 
 the eyeballs. 
 
 4. The fourth pair also controls eye muscles. 
 
 5. Back of these is the larger fifth pair, the trigeminal. 
 This pair supplies part of the face, and sends branches to 
 
200 Physiology. 
 
 the teeth. It is the nerve affected in neuralgia of the face. 
 It is the nerve of sensation for most of the head and face. 
 
 6. The sixth pair controls eye muscles. 
 
 7. The seventh pair are larger, and are farther back 
 and outward. These are the facial nerves, and control the 
 muscles of the face and the facial expression. 
 
 Cerebrum 
 
 Spinal Bulb 
 
 Fig. 89. Vertical Section of Brain. 
 
 8. The eighth, or auditory nerves, are the nerves of 
 hearing. 
 
 9. The ninth pair arise on the sides of the spinal bulb. 
 They supply the back of the tongue and the pharynx, and 
 are called the glosso-pharyngeal nerves. They give the 
 sense of taste from the base of the tongue. 
 
 10. The tenth pair, or vagus nerves, pass down out of 
 the brain cavity, give off branches to the pharynx and 
 
The Brain. 
 
 201 
 
 larynx, and are distributed to the heart, lungs, and 
 stomach. 
 
 11. The eleventh pair arise in part from the spinal cord outside of 
 the cranial cavity, enter the skull, and pass out again to supply certain 
 muscles of the neck and shoulders. 
 
 12. The last pair of cranial nerves, the twelfth, supplies the muscles 
 of the tongue, and are called the hypoglossal nerves. 
 
 Gray and White Matter of the Brain. 
 
 The gray matter of the brain is com- 
 posed of cells similar to those of the 
 spinal cord, while the white matter 
 of the inner part is composed of white 
 fibers like those of the outer part of 
 the spinal cord, or of the nerves. 
 
 Ganglions of the Brain. There are several masses of 
 gray matter in the interior of the brain. These are the 
 
 ganglions Of the _^^^ A ^ Gray Matter 
 
 brain. The white 
 fibers inside the 
 brain connect the 
 gray matter of 
 the convolutions 
 and these gang- 
 lions with all parts 
 of the body 
 through the spinal 
 cord. 
 
 Functions of the Cerebrum. The gray matter of the 
 outside of the brain is the central organ of intelligent sen- 
 sation and motion. The functions of volition, or willing, 
 of consciousness, of intelligence, seem to reside in, or rather 
 to depend upon the activities of, the cells of the gray 
 matter of the convolutions of the cerebrum. 
 
 14 PHY 
 
 Ganglions 
 
 Fig. 91. 
 
 Cerebrum 
 
 Cerebellum 
 
 Diagram of the Brain, showing the Spinal Cord, 
 Ganglions, and Course of the Fibers. 
 
202 
 
 Physiology. 
 
 The Center of Sensations itself Insensible. All sensation 
 seems to be in the gray matter of the convolutions of the 
 cerebrum, and yet it is itself insensible ; it may be cut and 
 cause no sensation. But when the nerve impulses from the 
 various parts of the body reach the gray matter of the cere- 
 
 Face Sensory 
 
 Face Motions 
 
 Taste 
 
 Spinal Cord 
 1st Spinal Nerve 
 2d Spinal Nerve 
 
 Fig. 92. The Cranial Nerves and Sense Organs. 
 
 brum they rouse the cells here to an activity that gives us 
 what we call sensation. It is never a sensation until it 
 reaches this part and is properly interpreted. 
 
 Crossed Control of the Body. While each hemisphere 
 mainly controls the muscles of the opposite half of the 
 body, it also, in part, has control of its own side. Paralysis 
 
The Brain. 
 
 203 
 
 of one side is due to injury of the opposite hemisphere of 
 the cerebrum. 
 
 Location of Brain Functions. Much has been learned in 
 late years as to the location of special functions in the brain. 
 
 CENTRAL FISSURE 
 
 MOTOR AREA / 
 
 FISSURE OF SILVIUS 
 
 Fig. 93. Location of Brain Functions. 
 
 Some of the motor and sensory centers are shown in 
 Fig. 93- 
 
 Connection of Brain Centers. These different brain 
 centers are connected by nerve fibers, and through these 
 connecting fibers we produce various actions as a result of 
 sensations. For instance (see Fig. 94), nerve impulses come 
 through the nerve of hearing to the auditory center, and we 
 have hearing; this center is connected with the speech 
 center ; and, as a result, we send out nerve currents to the 
 
204 
 
 Physiology. 
 
 organs of speech, and thus we speak in response to what 
 we hear. Currents from the eye reaching the visual center 
 may connect with the writing center, and we send out cur- 
 rents by which we write in response to what we have read. 
 
 Writing 
 
 Speech 
 
 Auditory 
 
 Fig. 94. Connection of Brain Centers. (After Landois and Stirling.) 
 
 Left Hemisphere Better Developed. The " speech cen- 
 ter" is in the left hemisphere; the right eye and ear, which 
 connect with the left brain, are better developed than the 
 left, and in general the left hemisphere seems superior (in 
 right-handed persons) to the right. 
 
 The Function of the Cerebellum. The cerebellum is the 
 center for regulating the actions of the skeletal muscles. 
 
The Brain. 205 
 
 When we walk or run, or even stand still, a number of 
 muscles must act, and act in concert. The nerve impulses 
 originate in the cerebrum, but the cerebellum is the center 
 for harmonizing the action of these various muscles. When 
 the cerebellum is injured, an animal staggers instead of 
 walking steadily. 
 
 Functions of the Spinal Bulb. The spinal bulb is the 
 enlarged part of the spinal cord which is within the cra- 
 nium. From it arise all the cranial nerves except the first 
 five pairs. The spinal bulb is also the center for the con- 
 trol of respiration, of circulation, of swallowing, and perhaps 
 for many other processes. 
 
 Brain Work and Brain Rest Sleep is not merely rest 
 for the body ; it should be complete rest for the brain. In 
 so far as there are dreams, it would seem to indicate a par- 
 tial activity ; that is, incomplete rest. The brain, like the 
 muscles, needs exercise, and it also needs regular periods 
 of rest. If a nerve cell is not kept active by the passage 
 of nerve impulses through it, it usually dwindles away, 
 and may entirely lose its power. 
 
 Sleeplessness. Intense brain work, without sufficient 
 sleep, is likely to lead to sleeplessness, as when one has 
 some subject of special study in hand and either will not 
 or cannot throw it off. Perhaps inventors are as subject 
 to this sort of trouble as any one class of men. Keeping 
 the blood continually in the brain is likely to lead to a per- 
 manent congestion, or inflammation, that may cause seri- 
 ous, if not fatal, results. 
 
 Fatigue. It is stated that brain workers need more 
 sleep than those who work chiefly with the muscles. Fa- 
 tigue of the voluntary muscles is much more a matter of 
 
206 Physiology. 
 
 nervous than of muscular origin. When one is completely 
 "tired out," as he would say, if his mind can be aroused, 
 as by some excitement, he will be found able to expend a 
 good deal more muscular energy. So, too, many persons 
 of slight muscular build, but of great " will power," are 
 able to do more work with the muscles than others with 
 larger muscles and less will. During fatigue the cell 
 bodies are found to decrease in size, but there is no per- 
 ceptible change in nerve fibers as a result of fatigue. 
 
 Blood Supply of the Brain. Blood is supplied to the 
 brain through four arteries : the right and left internal 
 carotid arteries, and the right and left vertebral arteries. 
 These arteries are so connected by cross-branches that if 
 any three of them should be compressed, or the blood 
 flow in them otherwise stopped, the fourth would still be 
 able to give the brain blood enough for its work. When 
 the brain is more active it receives a larger supply of 
 blood. During sleep it is paler. 
 
 Cause of Fainting. If the supply of blood to the brain 
 is shut off, unconsciousness quickly follows. In the ordi- 
 nary faint the blood supply to the brain has been reduced. 
 It is due to checking the action of the heart from some 
 emotion, or bad air, as in a close room ; severe pain may 
 be the cause ; a blow over the pit of the stomach may stop 
 the heart by reflex action. 
 
 Apoplexy. Apoplexy is caused by rupture of a blood 
 tube and the formation of a clot that presses on the brain. 
 
 Meningitis. Meningitis is an inflammation of the mem- 
 branes immediately surrounding the brain or spinal cord 
 or both. 
 
The Brain. 207 
 
 Summary. I . The outside of the brain consists of gray matter, the 
 inside of white matter. 
 
 2. The twelve pairs of cranial nerves are distributed to the head, with 
 the exception of the tenth and part of the eleventh. 
 
 3. The cranial nerves include the senses of sight, smell, taste, and 
 hearing. 
 
 4. Each hemisphere of the brain is connected with, and has chief 
 control of, the opposite half of the body. 
 
 5. The gray matter of the cerebrum is the seat of the will, sensation, 
 thought, and emotion. 
 
 6. The cerebellum regulates voluntary motion. 
 
 7. Many of the cerebral functions have been located. 
 
 8. The brain needs rest. In sleep less blood flows through the 
 brain. 
 
 9. Work reduces the size of nerve cells. During rest they increase 
 again. 
 
 Questions. i. Is there any special reason why the "speech center" 
 should be in the left cerebral hemisphere ? 
 
 2. Why does a light lunch sometimes enable one to go to sleep after 
 mental work ? 
 
 3. Why is it uncomfortable to hold the head down ? 
 
 4. How does the nervous system resemble a telegraph system ? In 
 what respects are the two unlike ? 
 
 5. Name some remedies for sleeplessness. 
 
CHAPTER XXII. 
 THE SENSES. 
 
 THE GENERAL SENSES. TOUCH AND TEMPERATURE 
 
 SENSE. 
 
 Afferent and Efferent Nerve Currents. Up to this point 
 we have been studying efferent, or out-going, nerve cur- 
 rents, such as control muscles and glands. Now let us 
 turn to the in-coming, or afferent, currents ; for it is by 
 means of the afferent currents to the brain that we get all 
 our sensations. In other words, it is through these cur- 
 rents that we get all our knowledge. 
 
 Two Classes of Sensations. There are two classes of 
 sensations, the special and the general. The special senses 
 include sight, hearing, taste, smell, touch, and temperature 
 sense. Among the general sensations are hunger, thirst, 
 fatigue, nausea, satiety, faintness, pain, muscular sense, etc. 
 
 Special Sensation due to External Force. Sensations 
 from the organs of special sense are due to the action of 
 an external force. For instance, sound waves entering the 
 ear affect the nerves of hearing, and we have a sensation 
 of hearing. Light acting on the optic nerve gives sight. 
 
 General Sensations due to Conditions within the Body. 
 
 -There are nerves of general sensibility in all parts of 
 
 the body. The endings of these nerves are acted on by the 
 
 blood and lymph. Currents are all the time coming through 
 
 208 
 
The Senses. 209 
 
 these nerves to the brain. But ordinarily we are not con- 
 scious of them. If the body is in need of food, the mes- 
 sages are stronger and we have a sensation of hunger. If 
 the poisonous waste matters are not removed by the organs 
 of excretion, their presence in the lymph is reported to the 
 brain, and we have a feeling, perhaps of fatigue, or of 
 decided discomfort, or even of pain. 
 
 The Muscular Sense. In judging the weight of a body 
 by holding it in the hand, our estimate is the result of sen- 
 sations aroused by nerve impulses from the organs used. 
 There are afferent nerve fibers with endings in ( I ) the skin, 
 (2) the muscles and tendons, and (3) the joints. In hold- 
 ing out the arm and in moving it up and down, all three 
 of these sets of nerve endings are stimulated, and impulses 
 are conveyed to the brain producing the muscular sense. 
 
 Dependence of Sight on Muscular Sense and Touch. It is difficult to 
 realize the importance of the muscular sense. An illustration of the as- 
 sistance which touch and the muscular sense give to the sense of sight 
 is furnished in the case of a boy who had been blind from birth, and re- 
 ceived sight at the age of twelve years by means of a surgical operation. 
 At first he could not distinguish a globe from a circular card of the same 
 color until he had touched them. He knew the peculiar features of the 
 dog and the cat by feeling, but not by sight. Happening one day to 
 pick up the cat, he recognized for the first time the connection between 
 the new sense of sight and the old familiar ones of touch and the mus- 
 cular sense. On putting the cat down he said, " o, puss, I shall know 
 you next time." 
 
 Pain. The nerves of general sensibility give informa- 
 tion of the state of nutrition in the tissues and the condi- 
 tion of the body as a whole. Ordinarily we are not aware 
 of these nerve currents. When they become stronger 
 than usual they give rise to feelings of general discomfort, 
 such as fatigue, depression, restlessness, etc. When the 
 currents become stronger still, we have pain. 
 
2 1 o Physiology. 
 
 Use of Pain. Pain is a warning of over-use or injury. 
 The milder nerve impulses that cause slight discomfort 
 ought to be sufficient to call attention to the condition. But 
 often these first reports are neglected. For instance, over- 
 use or abuse of the eyes may cause irritation, that is allowed 
 to go unheeded. The person may show the effect, by rub- 
 bing the eye, but, being absorbed in study, may fail to 
 stop reading and go on until there is actual pain. When 
 the first warnings are not heeded, pain follows and demands 
 attention. 
 
 Pain in the Skin. While the internal organs are ordina- 
 rily without feeling, the skin is especially sensitive. The 
 skin senses stand guard at the outposts of the body's 
 camp, and give warning of approaching danger. No 
 enemy may enter without being discovered by these keen 
 sentinels, and the alarm is given. In amputating a limb 
 the chief pain is in cutting through the skin. It is a com- 
 fort to know that the more severe wounds do not cause 
 pain in proportion to their extent 
 
 Hunger and Thirst. The cause of these sensations in 
 a healthy body is plainly the need of food and water 
 throughout the system. The sensation of thirst seems to 
 be in the throat, and the longing may be somewhat re- 
 lieved by merely moistening the throat. So hunger may, 
 for the time, be appeased by filling the stomach with indi- 
 gestible material. But the sensation soon returns. The 
 system has a crying need, and it is not to be put off. 
 That these sensations are really demands made by the 
 body as a whole may be shown by the fact that they are 
 permanently relieved by introducing food and water into 
 the body (by the rectum, for instance), in which case the 
 throat and stomach have nothing given them directly. 
 
The Senses. 
 
 211 
 
 Since, however, food and drink naturally enter by the 
 throat and stomach, the mucous membrane of these 
 organs has become the spokesman of the body. 
 
 What we learn by touching Objects. Let one person 
 rest the hand flat on the table, palm upward, and close the 
 eyes. An object placed on the 
 palm, by another person, may give 
 rise to various sensations, so that 
 it may be described as rough or 
 smooth, light or heavy, hot or 
 cold, wet or dry, etc. If now the 
 thumb and fingers are raised and 
 applied to the object, more definite 
 information will be gained as to its 
 shape, size, surface, etc. Now 
 raise the object in the hand, and 
 further appreciation will be gained 
 as to its weight. These experi- 
 ments show that several sensations are involved in the 
 handling of objects, and that the knowledge so gained is 
 complex. 
 
 Cutaneous Sensations. The sensations from objects 
 resting on the skin of the hand may all be referred to im- 
 pressions made on nerve endings in the skin, and are 
 called cutaneous sensations. They include : ( I ) the pres- 
 sure sense, or touch proper, (2) the temperature sense, and 
 (3) pain. 
 
 Nerve Endings in the Skin. The skin consists of two 
 layers, the epidermis and the dermis (see Figs. 64 and 65). 
 In the papillas of the dermis are nerve endings called 
 touch corpuscles (see Fig. 95). 
 
 Nerve 
 
 Fig. 95. Papilla of Skin with 
 Touch Corpuscle. 
 
212 Physiology. 
 
 Pressure on the skin affects these nerve endings, and 
 starts impulses that pass along the sensor fibers, through 
 the spinal cord, to the brain, and give us sensations of 
 touch. If a nerve fiber is touched, not at the end, but 
 somewhere along its course, we get a sensation, not of 
 touch, but of pain. 
 
 The Sense of Touch, Of the special senses the most 
 general is that of touch. Seeing and hearing, taste and 
 smell, belong to very limited parts of the outside of the 
 body, but we have the power of feeling all over the surface 
 of the body. Except in the mouth and nose, we get little, 
 if any, sense of touch from any organ but the skin. The 
 lining of the digestive tube and the internal organs gener- 
 ally lack this sense. 
 
 The Pressure Sense. The sense of touch, proper, is 
 strictly a pressure sense. If we test the skin to find what 
 regions are able to detect the least pressure, it is found 
 that the forehead is most sensitive, and nearly equally so 
 are the temples, back of the hand, and forearm. 
 
 Location of Touch Sensations. Each small spot of skin 
 has its own nerve endings and each nerve fiber connects 
 with a particular part of the gray matter of the brain. The 
 brain can therefore tell where each nerve current came 
 from, and thus we locate a sensation. 
 
 Accuracy in locating Touch Sensations. The accuracy 
 varies, and is ordinarily keenest where the nerves are most 
 numerous. Where the sense of locality seems to be im- 
 proved by cultivation, this appears to be due to keener per- 
 ception in the brain cells, and not to changes in the nerves 
 or nerve endings. This is shown in the fact that if the 
 fingers of one hand become more skilled in touch by prac- 
 
The Senses. 213 
 
 tice, it will be found that the fingers of the other hand, 
 without special training, are also improved. 
 
 Test by Compass Points. The delicacy of localizing 
 touch is usually tested in this way. The blunted points of 
 a light pair of compasses are allowed to rest gently on the 
 skin of various parts of the body. If the two points are 
 very close together, they will befe/t as one pressure. That 
 part which can best distinguish, as two points of touch, 
 these blunt points, is considered the most sensitive. By 
 this test the tip of the tongue is the most sensitive, being 
 able to distinguish, as two separate points of contact, the 
 tips of the compasses when only one twenty-fifth part of 
 an inch apart. Following is the order of degrees of sensi- 
 tiveness : tip of tongue, tips of fingers, lip, tip of nose, eye- 
 lid, cheek, forehead, knee, neck ; while the middle of the 
 back seems least sensitive. 
 
 Reference of Sensation to the Region of Nerve Endings. 
 If the " funny bone," or " crazy bone," be hit, i.e. if the 
 ulnar nerve be bruised against the bone, sharp pain may 
 be felt in the wrist and hand, and soreness of these parts 
 may be felt for days, though they are not in the least 
 injured, but only the nerve at the elbow. The currents 
 along this nerve rouse sensations that we have learned to 
 locate at the endings of the nerve fibers. If, then, owing 
 to injury, the currents start from the elbow, the brain still 
 refers them to the nerve endings in the hand and wrist. 
 So, too, after amputation of a hand or foot, there may 
 for years be sensations referred to the missing member, 
 probably due to irritation of the nerves of the stump. 
 
 The Temperature Sense. Many cases are on record in 
 which, from accident or disease, the sense of touch was 
 lost and the temperature sense retained, or vice versa. 
 
214 Physiology. 
 
 Such facts have led to the belief that the temperature 
 sense is distinct from that of touch, and has its own nerve 
 fibers and nerve endings. 
 
 Summary. i . The special senses result from the action of external 
 forces, such as light, heat, etc. 
 
 2. General sensations are referred to our bodies and their condition. 
 
 3. The muscular sense depends on impulses from muscles, tendons, 
 and joints. 
 
 4. The muscular sense and touch aid the sense of sight in giving us 
 correct perceptions of size and form. 
 
 5. Pain is a general sensation. It is a warning the cry of a senti- 
 nel that an enemy has passed the picket line. 
 
 6. Hunger and thirst indicate the need of food and drink. They 
 are local signals of a general want. 
 
 7. The cutaneous sensations are touch, temperature sense, and pain. 
 
 8. There are touch corpuscles in the papillas of the dermis. 
 
 9. Touch is the most general of the senses. 
 
 10. Touch proper, or pressure sense, is tested by perception of pres- 
 sure. 
 
 11. Touch localization is tested by discrimination as to the distance 
 of two points of contact. 
 
 12. Temperature is discerned by a special set of nerve fibers. 
 
 13. Sensations are referred to the region of the nerve endings. 
 
 Questions. i. What is the explanation of tickling. 
 
 2. Where does the change occur by which we become more skilled 
 in the sense of touch ? 
 
 3. Why does an emotion, such as shame, make one feel hot ? 
 
 4. If we had no sense of pain, what might result ? 
 
 5. If we pass by a meal time without eating why does the sense of 
 hunger usually disappear ? 
 
CHAPTER XXIII. 
 THE SENSE OF SIGHT. 
 
 Protection of the Eye. The eye is set well back in its 
 socket and guarded by three bony projections, the brow, 
 cheek bone, and the bridge of the nose. It is further 
 protected by the eyelids and eyelashes. 
 
 The Lacrymal Secretion. The lacrymal gland, or tear 
 gland, is just above the outer angle of the eye, and pours 
 its secretion over the eyeball. The lids serve as curtains 
 to admit or shut out light, and, by winking, wash the eye. 
 It is as though a man were kept all the time in front of a 
 plate-glass window, with water and rubber scraper, to keep 
 it clean and bright. The lacrymal secretion is ordinarily 
 carried off into the nasal cavity as fast as it is made. If 
 the ducts are stopped, or if the secretion is formed very 
 rapidly, the liquid overflows on the face as tears. 
 
 The External Parts of the Eye. The "white of the 
 eye " is the sclerotic coat. It has blood tubes, but ordina- 
 rily they are not conspicuous. The front part of the eye- 
 ball is covered with the cornea. This is transparent, and 
 the color of the iris shows through the cornea. In the 
 center of the iris is the hole, or pupil, by which light enters 
 the interior of the eye. 
 
 The Conjunctiva. The front of the eyeball is covered 
 by a thin, transparent, mucous membrane, the conjunctiva, 
 which turns back and lines the inside of the eyelids. It is 
 very sensitive. 
 
 215 
 
2l6 
 
 Physiology. 
 
 Movements of the Eye. There are six pairs of muscles which move 
 the eyes to right and left, up and down, and give rotary movements. 
 The two eyes move in the same direction at the same time, though in 
 looking at near objects the two eyes both point inward, so that one 
 appears cross-eyed. 
 
 Dissection of an Eye. The muscles and external parts of the eye 
 may readily be seen by examining the eye of a rabbit in its natural 
 position and then dissecting it out. A beef eye should be obtained 
 from the butcher and the structure of the eye learned by following the 
 description. 
 
 Ciliary Muscle 
 
 Optic Nerve Choroid 
 
 Fig. 96. Horizontal Section of Right Eye. 
 
 The Coats of the Eye. There are three coats, the outer 
 or sclerotic, the middle or choroid, and the inner or retina. 
 
 The Sclerotic Coat. This is of a dull white color, con- 
 stituting the "white of the eye." It is thick and tough, 
 holding all the contained parts firmly and furnishing suffi- 
 cient strength for the attachment of the muscles that move 
 the eyeball. 
 
The Sense of Sight. 217 
 
 The Choroid Coat. The middle coat of the eye is the 
 choroid. It is thinner than the sclerotic and of much more 
 delicate structure. It is full of blood tubes, and has an 
 inner lining of dark color to prevent the reflection of light 
 in the eye, just as most optical instruments are painted 
 black on the inside. 
 
 The Retina. The retina is an expanded part of the 
 optic nerve and forms an inner coat that lines all but the 
 front part of the eye. It is a thin, translucent film, some- 
 what like the film that iorms over the white of an egg when 
 it is first dropped into hot water. It is very delicate and 
 easily torn. The retina is the only part of the eye that is 
 sensitive to light, and on it the images must be formed to 
 produce distinct vision. 
 
 The Cornea. The clear front part of the eye is the 
 cornea. It is a continuation of the sclerotic coat and is 
 more bulging than the rest of the front of the eye, as can 
 be seen by taking a side view of the eye, or by noticing 
 some one who closes the eyelids and rolls the eyes about. 
 
 The Iris. This is the part that gives the color to the 
 eye, or if the pigment that gives the color is lacking, the 
 blood gives the pink color seen in albinos. The iris is a 
 forward continuation of the choroid coat. 
 
 The Pupil. Most of the light that passes through the 
 transparent cornea is stopped by the opaque iris. But in 
 the center of the iris is a round hole through which light 
 enters the interior of the eye. The pupil looks dark be- 
 cause it is the only opening into a dark room. 
 
 Regulation of the Amount of Light admitted into the Eye. 
 Hold a hand glass between the face and a well-lighted window. Note 
 the size of the pupils. Quickly turn toward the darkest part of the 
 15 PHY 
 
2 1 8 Physiology. 
 
 room. The iris has circular muscle fibers that make the pupil smaller 
 when there is too much light for the eye, and when the light is feeble 
 the pupil opens wider. 
 
 The Aqueous Humor. There is a small space between 
 the cornea and the iris. In this space is the clear, watery 
 aqueous humor. 
 
 The Vitreous Humor. All but the front part of the 
 space within the eye is filled with a clear, jelly-like sub- 
 stance, the vitreous humor. 
 
 Fig. 97. The Formation of an Image on the Retina. 
 
 The Crystalline Lens. Just back of the iris is a double- 
 convex lens, clear as crystal, and of about the consistency 
 of a gumdrop. It is less convex on the front surface. 
 
 Experiment with Lens to show Inversion of Image. Take a 
 double-convex lens or any hand magnifier. Hold this up at the rear 
 of the room and catch the inverted image of the window on a piece of 
 paper held back of the lens. This illustrates how the image of an 
 external object is formed by the crystalline lens upon the retina of 
 the eye. 
 
 Experiments to illustrate the Adjustment for Distance. (0 Stick 
 a pin at each end of a book cover. Hold the book at about the usual 
 distance for reading, so that the two pins are in a line with the eye. 
 Look closely at the nearer pin, and the second pin will appear indistinct 
 and double. Now look closely at the head of the farther pin. The 
 nearer one may be seen doubled, but not sharply. (2) Hold the tip of 
 a pencil in a line with any object, say a picture, on a wall opposite. In 
 looking at the tip of the pencil the picture is dim. Now look by the pen- 
 cil at the picture, and the point of the pencil will be blurred and doubled. 
 
 Accommodation. We cannot, at the same time, see 
 distinctly a near and a distant object. When we look at 
 
The Sense of Sight. 
 
 219 
 
 a near object the lens becomes thicker, and when we look 
 at a distant object the lens becomes less thick. This ad- 
 justment is called accommodation. 
 
 CILIARY MUSCLE 
 
 FAR NEAR CILIARY PROCESS 
 
 Fig. 98. Changes of the Lens in Accommodation. 
 
 The Blind Spot. Light falling on the optic nerve itself has no effect 
 in giving a sensation of light. If the light falls on the spot where the 
 optic nerve enters the eyeball, we see nothing. Hence, this spot is 
 called the blind spot. 
 
 Experiment illustrating the Blind Spot. At the left (as looked at 
 by the class) of a long blackboard make a bright circular spot, three 
 inches in diameter, with white or yellow crayon. Beginning at the 
 right of this write the figures i, 2, 3, etc., along the whole length of the 
 board, about eight inches apart. Let each pupil close the right eye and 
 look at the bright spot. Then let each read the figures, passing slowly 
 from one to another, at the same time noticing whether the bright 
 spot can be seen. To succeed in this the eye must not be allowed to 
 waver. Have the pupils tell when the bright spot disappears, then 
 read on, and note when the spot reappears. 
 
 Another Experiment. In this experiment shut the right eye, and 
 be careful not to let the eye waver. 
 
 >|c Read this line slowly. Can you see the star all the time? If the 
 star does not disappear before reaching the end of the line, let the eye 
 travel on to the right of the page, or hold the book nearer the face. 
 In the human eye the optic nerve enters the eye not in the center, but 
 nearer the nose, so that in turning the left eye toward the right at the 
 proper angle, the image of the star falls upon the spot where the optic 
 nerve enters. As this spot is insensitive to light, the star no longer 
 appears. 
 
220 
 
 Physiology. 
 
 The Structure of the Retina. The retina is very complicated in its 
 structure. No less than ten layers have been distinguished, as shown 
 in Fig. 99. The rays of light pass through the retina, and produce 
 their effect on the rods and cones which constitute the outer (back) 
 layer ; and the nerve impulses aroused by the light must return through 
 the thickness of the retina to be conveyed along the nerve fibers of the 
 innermost layer of the retina to the optic nerve. 
 
 Inner or Vitreous Surfac 
 
 Path of 
 Inci- 
 dent 
 Light 
 
 Internal Limiting Layer 
 Layer of Nerve Fibers 
 Layer of Nerve Cells 
 
 Inner Molecular Layer 
 
 Inner Nuclear Layer 
 
 Outer Molecular Layer 
 
 Outer Nuclear Layer 
 
 _. External Limiting Layer 
 
 Layer of Rods and Cones 
 
 Layer of Pigment Cells 
 
 Outer or Choroid Surface 
 
 Fig. 99. Section of the Retina. (Waller.) 
 
 Importance of the Retina. The chief structure in the 
 eye is the retina. Without this all else is useless. If light 
 falls on the retina, nerve impulses pass along the fibers of 
 the optic nerve to the brain, and we have a sensation of 
 light. But in order to see anything distinctly, the light 
 must fall on the retina in such a way as to form a distinct 
 image of that object. If the lens be removed, or becomes 
 opaque, as in " cataract," we see objects very indistinctly, 
 though we may be able to tell light from darkness. Light 
 
The Sense of Sight. 221 
 
 from an object passes through the cornea, aqueous humor, 
 lens, and vitreous humor, and the rays are so refracted as 
 to form an inverted image on the retina. 
 
 The Optic Nerve not Sensitive. The optic nerve, while capable 
 of carrying nerve impulses that cause sensations of light, is not itself 
 sensitive to light. If the optic nerve be cut, it does not give pain, but 
 gives the sensation of a flash of light. 
 
 Sympathy between the Two Eyes. While most of the 
 fibers from each optic nerve cross to the other side of the 
 brain, some fibers go to the same side of the brain. We 
 can therefore better understand the close sympathy be- 
 tween the two eyes. 
 
 Color Blindness. It is found that some persons cannot distinguish 
 certain colors. Blindness to red and green are most common. This 
 is a matter of importance among railroad men and sailors, where it is 
 necessary to distinguish red and green signals. 
 
 Summary. i . The eye is protected by its bony surroundings, lids, 
 lashes, tears, sensitiveness of the conjunctiva, etc. 
 
 2. The eye has three coats sclerotic, choroid, and retina. 
 
 3. The pupil is a hole in the iris, and varies in size to regulate the 
 amount of light admitted. 
 
 4. The cornea, aqueous humor, lens, and vitreous humor form an 
 inverted image on the retina. The eye is a camera, darkened inside. 
 
 5. The lens changes its thickness for seeing at different distances. 
 
 6. Suitable glasses overcome many of the defects in eyesight. 
 
 7. The retina is an expansion of the optic nerve, and is exceedingly 
 complicated in its structure. 
 
 8. The blind spot is the place where the optic nerve enters the eye. 
 
 9. The optic nerve is insensitive to light, but injury to it causes sen- 
 sations of light. 
 
 10. Most of the fibers of the optic nerve cross to the other half of 
 the brain, but some do not cross. 
 
 1 1 . Defects in eyesight are much more common among civilized men 
 than with the uncivilized. 
 
222 Physiology. 
 
 12. The care of the eyes must be made a subject of study and care- 
 ful thought by all reading people. 
 
 Questions. i . What is " cataract " ? 
 
 2. What is the cause of " double vision " ? 
 
 3. Why does the well eye sympathize with the affected one? 
 
 4. Why does looking at a bright light often cause a person to 
 sneeze ? 
 
 5. What is the condition of one who is "cross-eyed" ? 
 
 6. Compare the pupils of a man, a cat, and a cow. 
 
 7. Does the color of the eye have any relation to the strength of 
 eyesight ? 
 
 8. Why is one blinded on entering a bright room from the dark? 
 
 9. Why is one going from a bright room into the dark unable to 
 see at first, but gradually sees more distinctly ? 
 
 10. Why can one not see well when the eye "waters 11 ? 
 
 1 1. Should the lights which illumine a pulpit or platform be so placed 
 that they can shine into the eyes of the congregation? How should 
 they be arranged? 
 
 12. If each eye has a blind spot, why are there not blank spaces in 
 the field of vision ? 
 
 13. What advantage has a stereoscopic view over a single view? 
 How are stereoscopic views made ? 
 
CHAPTER XXIV. 
 DEFECTS OF EYESIGHT AND CARE OF THE EYES. 
 
 DEFECTS OF EYESIGHT. 
 
 The Wearing of Glasses. It will be noticed that many 
 people, even children, nowadays wear spectacles or eye- 
 glasses. The reason for this is probably not entirely 
 because people's eyes are more defective now than they 
 were fifty years ago ; but partly because everybody, chil- 
 dren and all, now have to use their eyes a great deal more 
 than people did fifty years ago. Evidence of certain defects 
 of the eyes for which glasses are worn show themselves 
 more now than they did then ; and therefore glasses have 
 to be worn more. 
 
 Symptoms of Defective Eyes, Many children suffer 
 from headaches, or their eyes are red and watery. Some- 
 times they cannot plainly see the writing or drawing on 
 the blackboards, or they appear to be stupid, or hold their 
 books close to their eyes when reading or studying. Such 
 children probably have some defect of the eyes which 
 glasses will remedy. They should be sent to the oculist 
 to have their eyes examined, and if it be found that they 
 need glasses, they should wear them. It does not always 
 follow that a person does not need glasses because he can 
 see well ; defects in his eyes may require such great effort 
 of the eye muscles that control the focusing of the eyes as 
 to cause headaches, nervousness, and other troubles which 
 a properly fitting pair of glasses will remedy. 
 
 The Focus. If an object is to be seen clearly, the eye, 
 
 223 
 
224 Physiology. 
 
 like a photographic camera, has to be focused for the par- 
 ticular distance at which the object is placed. In the 
 photographic camera the " focusing " is done by moving 
 the lens nearer to or farther from the plate or film, accord- 
 ing as the object to be photographed is farther from or 
 nearer to the camera. To get a clear picture in pho- 
 tography, therefore, the length of the camera must be 
 adjusted to the distance from the camera of the object to 
 be "taken." When the object is a short distance from 
 the camera, the " bellows " is pulled out and the camera is 
 lengthened; when the object is farther away, the " bellows " 
 is pushed in and the camera is shortened. If the camera 
 is not properly "focused," a clear photograph cannot be 
 taken. So also if one's eyes be not properly " focused," he 
 cannot see clearly. 
 
 The Crystalline Lens. The eye is "focused" in a dif- 
 ferent way. It cannot be made longer when we look at 
 nearby things, or shortened when we look at more dis- 
 tant objects. Instead of this, the eye is "focused" by 
 changing the shape of the " crystalline lens," which lies 
 just back of the iris and the pupil, and which performs in 
 the eye the same service that the glass lens does in the 
 photographic camera ; viz., it throws upon the retina, just 
 as the camera lens does upon the photographic plate or 
 film, an image of the object at which we are looking. Now, 
 if we could change the thickness of the glass lens in the 
 camera, making it thicker when photographing near objects 
 and thinner when photographing those farther away, we 
 should be doing in the camera just what is done in the eye 
 when we " focus " it. In the eye, when we look at a nearby 
 object, the crystalline lens becomes thicker ; when we look 
 at a more distant object, the crystalline lens becomes thin- 
 
The Sense of Sight. 225 
 
 ner or flatter. It is made thinner and flatter by being 
 pressed upon by elastic connective tissues between which 
 it lies, just as a soft rubber ball will be made flatter if it be 
 put between two layers of a handkerchief and the sides of 
 the handkerchief pulled upon. 
 
 The Natural Focus. In a state of nature the eye is 
 used mostly for looking at distant objects, and not for 
 looking at books and near objects, as we now have to do 
 many hours at a time. Nature made the eye so that it 
 would be focused for the distance by the elastic pull of the 
 coats of the eyeball. Elastic coats not being made to work 
 by nervous energy, as muscles are, never grow tired, as 
 muscles do when they work. Nature made our eyes so 
 that they would be focused for distant objects without any 
 muscular action. Therefore, our eyes do not tire when 
 we look at the distance ; they are " resting." But in order 
 that we may also clearly see near objects, our eyes are so 
 made that the crystalline lens may be made thicker. Since 
 in a state of nature the eyes are not used very often nor 
 for very long periods in looking at near objects, the focus- 
 ing for near objects is done by muscular action. Hence, 
 the eyes become tired when they are used for long periods 
 in looking at near objects. 
 
 " Accommodation. " Everybody has seen a lady's arm 
 bag which closes by pulling the " puckering string." If 
 the mouth of the bag were elastic, so that it would open 
 itself if the string were not pulled, and if the string were 
 a muscle, it would be something like the arrangement of 
 elastic coats and muscles by means of which the eye is 
 focused. Just behind the iris, where it is attached to the 
 sclerotic coat of the eyeball, there is a very small circular 
 muscle called the " ciliary muscle " or " muscle of accom- 
 
226 Physiology. 
 
 modation." When it contracts, this muscle overcomes the 
 pull of the elastic tissues, which causes the flattening of the 
 crystalline lens, which, being elastic, becomes thicker, and 
 the eye is focused for a near object. 
 
 Effect of Age. As people grow older, the crystalline 
 lens, like the other parts of the body, slowly loses its 
 elasticity. Hence when the pressure is relaxed by the 
 action of the muscle of accommodation, the lens cannot 
 become thick enough to focus the eye for very near 
 objects. For this reason middle-aged people cannot clearly 
 see objects as near to the eyes as young people can. This 
 is called "presbyopia," from two Greek words meaning 
 " old-eye." 
 
 In order to see near things clearly, to read, etc., middle- 
 aged people are compelled either to bold things off at 
 arm's length, which is very inconvenient, or to put on 
 glasses. But through these glasses they cannot see well 
 at the distance, because the focus of the glasses is for a 
 close object and cannot be changed. 
 
 (2) Far-sighted Eye. (I) Normal Eye. (3) Near-sighted Eye. 
 
 Fig. 100. Defects in Eyesight. 
 
 Far Sight. It not infrequently happens that the eye- 
 ball is not long enough from the front to the back to 
 permit of proper focusing for objects at a great distance 
 without bringing into use the muscle of accommodation. 
 In other words, a perfect eye is focused for great distances 
 when the muscle of accommodation is at rest. In the 
 
The Sense of Sight. 227 
 
 short eye, however, clear vision cannot be had at any dis- 
 tance, unless the muscle of accommodation be actively at 
 work. Such eyes are called " far-sighted," or " hyper- 
 metropic," from three Greek words meaning "over-meas- 
 ured-eye." 
 
 On account of the fact that such an eye cannot see 
 clearly at any distance without calling into constant action 
 the muscle of accommodation, that muscle has no periods 
 of rest except during sleep. It is apt to tire out, therefore, 
 and the person who has such eyes may be subject to 
 headaches or other nervous troubles. To overcome this 
 he should wear glasses. Although his glasses are the 
 same kind that " old-sighted " people wear, the " far- 
 sighted " person can see clearly at the distance as well 
 as near by with his glasses, while the " old-sighted " person 
 can see clearly only close objects with his. 
 
 It not infrequently happens that the " far-sighted " per- 
 son can see equally well at the distance with or without 
 his glasses. But this is not a sign that he does not need 
 glasses; on the contrary, it is a sign that he does need 
 them ; for if he did not need them, he could not see clearly 
 with them. 
 
 If the eyes be too long from front to back, they cannot 
 see clearly at a distance, but can see near objects clearly. 
 Such eyes are called "near-sighted," or "myopic," from 
 two Greek words meaning "mouse-eye," because near- 
 sighted eyes, like the eyes of a mouse, are not infrequently 
 quite prominent. 
 
 The eyes of most babies are " far-sighted," but as the 
 rest of their bodies grow, their eyes also generally grow 
 until they become only slightly "far-sighted." Sometimes 
 the growth of the eyes does not keep pace with the rest of 
 the body and the eyes remain quite far-sighted; in other 
 
228 Physiology. 
 
 cases they grow too rapidly in one direction, from the front 
 to the back, and become near-sighted. Children with either 
 far-sighted or near-sighted eyes should wear glasses, the 
 far-sighted to avoid headaches and nervous troubles, the 
 near-sighted to enable them to see plainly at a distance. 
 
 Near Sight. When a child's eyes begin to grow near- 
 sighted, there is danger that the near-sightedness will 
 increase if special care is not taken to prevent it. The 
 tissues of the child's eyes are comparatively soft and yield- 
 ing. Children nowadays use their eyes a great deal for 
 near work. The nearer any object is held to the eyes, the 
 more the little muscles of accommodation pull upon the soft 
 and yielding coats of the eyeball and tend to stretch them. 
 Not only that, but the nearer any object is held to the eyes, 
 the more the eyeballs turn inward ; and the more they turn 
 inward, the more they are pressed upon and squeezed by 
 the six little muscles which move each eyeball. Thus pulled 
 at from within and pressed upon from without, it not infre- 
 quently happens that children's eyes become too long from 
 before backward, that is, " near-sighted." 
 
 Children can clearly see objects which they hold very 
 near to the eyes, and for this reason frequently get into the 
 habit of doing so. This is a very bad habit indeed, for it 
 tends to make the eyes near-sighted, or, since it tires the 
 muscles which turn the eyeballs inward and the muscles of 
 accommodation, not infrequently causes headaches. This 
 habit should be carefully and constantly corrected, and no 
 child should be allowed to hold objects nearer than about 
 fifteen inches from the eyes. If it cannot see plainly the 
 smallest print at that distance, something is wrong with 
 the eyes. 
 
 But the necessity for the wearing of glasses is not the 
 
The Sense of Sight. 229 
 
 worst thing about near-sighted eyes. The tendency of 
 near-sighted eyes is to grow more and more near-sighted 
 unless great care is taken to prevent it. Even that, how- 
 ever, would not be very bad, for it would require only the 
 wearing of stronger and still stronger glasses. But as 
 the eyeball becomes more near-sighted, it becomes longer ; 
 and as it becomes longer, the membranes of which it is 
 composed, especially the retina and the choroid coat, 
 become more and more stretched and pulled upon, until 
 they may even become diseased or pull apart, so that 
 serious eye trouble, even blindness, may result from un- 
 cared-for near-sightedness. 
 
 Near-sightedness may, therefore, become a disease of 
 the eyes. In fact, a near-sighted eye may be looked upon 
 as a diseased eye. As near-sightedness occurs practically 
 only among civilized people, it may be called a disease of 
 civilization, and one would naturally expect to find it most 
 prevalent among those people who use their eyes most for 
 near work. Such is the fact. The Germans, of all people, 
 use their eyes most for near work, and among them near- 
 sightedness is very common. Another defect of the eyes 
 occurs when the clear front parts of the eye (cornea and 
 lens) are unequally curved so that the rays of light do not 
 converge properly in the eye, the image on the retina is 
 blurred, and the person thus afflicted cannot see clearly. 
 This defect in vision, which is called astigmatism, can be 
 corrected by specially prepared glasses. 
 
 Importance of Proper Glasses. It will thus be seen that 
 glasses are very frequently a necessity for children. Nerv- 
 ous, suffering, peevish, backward children, unable to keep 
 up in their studies, are often changed into sturdy, happy, 
 bright pupils who keep pace with their classes, simply by 
 
230 Physiology. 
 
 fitting them with proper glasses. But as the proper fitting 
 of glasses is not a simple thing, the child should be taken 
 to an oculist, and glasses should not be purchased of ped- 
 dlers. Ill-fitting glasses may be worse than none at all. 
 
 THE CARE OF THE EYES. 
 
 1. Objectionable Light. In reading we wish light from 
 the printed page. Hence we should avoid light entering 
 the eye from any other source at this time. While reading, 
 then, do not face a window, another light, a mirror, or white 
 wall. White walls are likely to injure the eyes. Choose 
 a dark cover for a reading table. Sewing with a white 
 apron on has injured the eyes. Direct sunshine very near 
 the book or table is likely to do harm. 
 
 2. Position in Reference to Light. Preferably have the 
 light from behind and above. Sitting under and a little 
 forward of a hanging lamp will allow the light to fall on 
 the book and keep it away from the face. In reading by 
 daylight avoid cross-lights so far as possible. 
 
 3. Electric Light The incandescent electric light has 
 advantages in throwing the light downward and in giving 
 out little heat ; but owing to its irregular illumination (due 
 to the shadow cast by the wire or filament), it is not well 
 suited for study or other near work. For this purpose an 
 Argand gas or kerosene burner is much to be preferred, 
 since it throws a soft, uniform, and agreeable light upon 
 the work. 
 
 4. Reading Outdoors. Reading out of doors is likely to 
 injure the eyes, especially when lying down. To read 
 while lying in a hammock is bad. Too much light directly 
 enters the eye, and too little falls upon the printed page. 
 
The Sense of Sight. 231 
 
 5. Reading Heavy Books. Do not hold the book or 
 work nearer the eyes than is necessary. So far as possible 
 avoid continuous reading in large or heavy books by arti- 
 ficial light. Such books being hard to hold, the elbows 
 gradually settle down against the sides of the body, and 
 thus the book is held too close to the eyes, or at a bad 
 angle, or the body assumes a bad position. 
 
 6. Resting the Eyes. Frequently rest the eyes by 
 looking up and away from the work, especially at some 
 distant object. One may rest the eyes while thinking over 
 each page or paragraph, and thus really gain time instead 
 of losing it. 
 
 7. Strength of Light. Have light that is strong enough. 
 At twice the distance from a lamp the light is only one 
 fourth as strong. Reading just before sunset is not wise. 
 One is often tempted to go on, not noticing the gradual 
 fading of the light. 
 
 8. Evening Reading. Do the most difficult reading by 
 daylight, and save the better print and the books that are 
 easier to hold for work by artificial light. Writing is usu- 
 ally much more trying to the eyes than reading. By care- 
 fully planning his work one may economize eyesight. 
 Weak eyes, by proper care, may outlast and do more work 
 than those naturally stronger, but injured by abuse. Read- 
 ing before breakfast by artificial light is usually bad. 
 
 9. Reading during Convalescence. Many eyes are 
 ruined during convalescence. At this time the whole sys- 
 tem is weak including the eyes. There is a strong 
 temptation to read, perhaps to while away the time, per- 
 haps to make up for lost time in school work. This is a 
 time when a friend may show his friendship. 
 
232 Physiology. 
 
 10. Irritation of the Eyes. If one finds himself rubbing 
 his eyes, it is a sign that they are irritated. Stop read- 
 ing, find the cause, and do not read on unless the irritation 
 ceases. If any foreign object, as a cinder, lodges in the 
 eye, it is better not to rub the eye, but to draw the lid 
 away from the eyeball and wink repeatedly ; the increased 
 flow of tears may dissolve and wash the matter out. If it 
 be a sharp-cornered cinder, rubbing may merely serve to 
 fix it more firmly in the conjunctiva. If it does not soon 
 come out, the lid may be rolled up over a pencil, taking 
 hold of the lashes or the edge of the lid. The point of a 
 blunt lead pencil is a convenient and safe instrument with 
 which to remove the particle. 
 
 11. Keep the Eyes Clean. Be careful to keep the eyes 
 clean. Do not rub the eyes with the fingers. Aside from 
 consideration of rules of etiquette, there is danger of intro- 
 ducing foreign matter that may be very harmful. It is 
 very desirable that each person have his individual face 
 towel. By not observing this rule certain contagious 
 diseases of the eyes often spread rapidly. 
 
CHAPTER XXV. 
 TASTE, SMELL, HEARING, AND THE VOICE. 
 
 Uses of the Sense of Taste. The sense of taste helps 
 us in judging of the fitness of food. By reflex action the 
 taste of agreeable substances aids in digestion by stimulat- 
 ing the glands, especially the salivary glands. 
 
 The Papillas. The surface of the tongue is covered 
 with papillas. Most of them are slender, and like the 
 
 Papillas 
 
 Glosso-pharyngeal 
 Nerve (9th) 
 
 Gustatory Branch of Fifth Nerve 
 Fig. 101. Nerves and Papillas of the Tongue. 
 
 papillas of the skin, are organs of touch. Scattered among 
 these are larger papillas in which are the endings of the 
 nerves of taste. 
 
 The Nerve Supply of the Tongue. The nerves of taste 
 are the glosso-pharyngeal, distributed to the back part of 
 the tongue, and the gustatory in the front part. The tip 
 of the tongue seems to be most sensitive to sweets and 
 salts, the back part to bitters, and the sides to acids. 
 1 6 PHY 2 33 
 
234 
 
 Physiology. 
 
 Solution Necessary for Tasting Substances must be 
 dissolved before they can be tasted. If the tongue be 
 wiped dry, and a few grains of salt or sugar be placed on 
 it, the taste will not be perceived for a little time. Insol- 
 uble substances give no taste. 
 
 Flavors. What we call flavors affect us more through the sense of 
 smell than through taste. If the nose be held shut, a piece of onion 
 placed on the tongue does not produce what we usually call the taste 
 of the onion. By holding the nose we may get rid of the disagreeable 
 part of taking certain medicines. Let the pupil experiment with various 
 substances as above indicated. 
 
 The Sense of Smell. The nerves of smell, the olfactory 
 nerves, are distributed in the walls of the nasal passages. 
 The sense of 
 odor gives us 
 information as 
 to the quality 
 of food and 
 drink, and more 
 especially as to 
 the quality of 
 the air we breathe. Hence 
 we find the organ placed 
 at the opening of the 
 respiratory passages, and 
 close to the organ of 
 taste. 
 
 Olfactory Bulb 
 
 Olfactory Nerves. 
 
 Branches of 
 Fifth Nerve 
 
 Turbinated Bones 
 
 102. 
 
 Nerves of the Outer Wall of the 
 Nasa> Cavity. 
 
 Why we Sniff. In quiet breathing the air passes along the lower 
 air passages just above the hard palate. When we wish to test the 
 quality of the air, we sniff, that is, make a sudden inspiration by jerking 
 the diaphragm down, and air from the outside then rushes into the 
 upper nasal passages, over the walls of which the olfactory nerves are 
 spread in the mucous membrane. In inflammation, as from a cold, 
 the narrow nasal passages, especially the upper, are often closed. 
 
Taste, Smell, Hearing, and the Voice. 235 
 
 The Parts of the Ear. The parts of the ear are the 
 
 external, the middle, and the internal ear. 
 
 The External Ear. The external ear gathers the sound 
 waves, and directs them into the opening of the ear, but 
 the loss of the external ear does not seriously interfere 
 with hearing. The passage leading inward from the ear 
 extends about an inch, and is then completely shut off 
 
 Semicircular Canals "** 
 
 Stirrup 
 
 Fig. 103. Structure of the Ear. 
 
 from the cavities beyond by a thin membranous partition, 
 the tympanic membrane or drum skin. This passageway 
 is guarded by hairs, and is further protected by wax 
 secreted by glands of the lining. 
 
 The Middle Ear. Beyond the membrane of the tym- 
 panum is a cavity called the middle ear. Extending across 
 the cavity of the middle ear is a chain of very small bones, 
 the hammer, anvil, and stirrup, the hammer being attached 
 to the inner surface of the membrane of the tympanum, 
 
236 Physiology. 
 
 and the stirrup being fastened by its base to the wall of 
 the internal ear. 
 
 The Eustachian Tube. The middle ear communicates 
 with the pharynx by means of a narrow tube called the 
 eustachian tube. It admits air to equalize the pressure on 
 the two sides of the tympanic membrane. This tube is 
 closed most of the time, but opens when we swallow. 
 
 The Internal Ear. The internal ear consists of several 
 complicated cavities and tubes which contain a liquid in 
 which rest the nerves. The principal cavity is the cochlea, 
 or snail-shell cavity, in which the nerve endings are con- 
 nected with an exceedingly complicated apparatus. 
 
 The Production of Sound. Sound waves set the drum 
 skin or membrane of the tympanum in vibration; the 
 vibrations are conveyed by the chain of bones across the 
 middle ear to the liquid of the inner ear. Through the 
 complicated apparatus of the snail shell the vibrations of 
 the liquid are made to start nerve impulses in the fibers of 
 the auditory nerve, and when these nerve impulses are 
 rightly received and interpreted by the brain, we have a 
 sensation called sound. 
 
 The Equilibrium Sense. Probably most of the senses contribute 
 to the maintaining of the equilibrium of the body by giving information 
 as to position, motion, etc., especially sight and the muscular sense. 
 
 Only that part of the auditory nerve which is distributed in the " snail 
 shell " of the ear is now supposed to have to do with hearing. There 
 seems to be good evidence that the semicircular canals inform us as 
 to changes of the position of the body, and they are regarded as the 
 seat of an " equilibrium sense." 
 
 The Care of the Ear. In cleaning the ear no hard sub- 
 stance should be used ; even the finger nail is likely to 
 do harm. A moistened cloth should be used. It is not 
 
Taste, Smell, Hearing, and the Voice. 237 
 
 well to stuff the ears with cotton. If there is any trouble 
 with the hearing, of course a physician should be consulted 
 without delay. 
 
 Colds and Deafness. A cold often produces inflamma- 
 tion of the mucous membrane of the pharynx. This in- 
 flammation may extend along the eustachian tube to the 
 middle ear and affect the hearing. See "Adenoids," p. 95. 
 
 Epiglottis 
 Base of Tongue 
 
 Hyoid Bone 
 
 False Vocal Cord 
 Ventricle 
 Vocal Cord 
 
 Cartilage 
 
 Trachea 
 
 FROM RIGHT TO LEFT MEDIAN 
 
 Fig. 104. Longitudinal Sections of the Larynx. 
 
 The Ear and the Voice. The delicate structure of the 
 ear is fully matched by the fine adjustment and range of 
 the voice. The voice is produced in the larynx at the upper 
 end of the windpipe. The projecting angle of the larynx 
 is called " Adam's apple." 
 
 The Vocal Cords. The vocal cords are not cord-like. 
 They are mere ridges projecting inward from the sides of 
 the larynx. They maybe stretched to various degrees and 
 placed in different positions, according to the sound that 
 is to be produced. 
 
238 Physiology. 
 
 The Position of the Vocal Cords. While we are quietly 
 breathing, the vocal cords lie back, like low ridges, against 
 the sides of the larynx, and offer nearly the whole channel 
 of the larynx for the free passage of air for breathing pur- 
 poses. But when we wish to produce vocal sound, the 
 vocal cords are made to stand out farther from the side 
 walls, and interfere with the free passage of the air. The 
 vocal cords are attached close to each other in front, but 
 at the back of the larynx they diverge widely, forming a 
 
 Epiglottis 
 False Vocal Cords 
 
 True Vocal Cords . 
 
 i 
 Glottis Narrowed, High Note Glottis Wider, Quiet Breathing 
 
 Fig. 105. The Vocal Cords, seen from Above 
 
 letter V, with the angle of the V just back of Adam's 
 apple. "When changes in the voice or in breathing are 
 being made, the white glistening vocal cords may be seen 
 to come together or to go apart like the blades of a pair of 
 scissors." In a high note the cords are close together and 
 nearly parallel. As the air is forced past the edges of the 
 vocal cords, they are set in vibration, and produce the 
 sound called the voice. 
 
 Illustration of the Vocal Cords. The principle of the action of the 
 vocal cords can be illustrated by the common toy known as the squeak- 
 ing balloon, or "squawker." Here the air is driven out past a band of 
 rubber stretched across the inner end of the tube. If instead of one 
 band with both edges free, we were to tie on the inner end of the tube 
 two bands of rubber, each covering the outer edge of the tube, leaving 
 the inner edge of the rubber free, and with the two bands touching at 
 one end and considerably separated at the other end, we would have a 
 pretty fair resemblance to the larynx. 
 
Taste, Smell, Hearing, and the Voice. 239 
 
 Loudness of Voice. The loudness of the voice depends on the force 
 with which the air is driven past the cords, and on the size and con- 
 dition of the cords themselves. 
 
 Pitch of Voice. Pitch depends on the rapidity of the vibrations, 
 which is determined by the length of the cords and their tension. 
 Other things being equal, the size of the larynx would determine the pitch. 
 
 Voice and Speech. The larynx by itself produces vocal sound 
 merely. In speech the sounds produced in the larynx are much modi- 
 fied by the lips, tongue, teeth, cheeks, etc. We have voice as soon as 
 born, but we only gradually acquire the power of speech. This dis- 
 tinguishes man from the animals below him. 
 
 Summary. i. Taste enables us to judge of the quality of food, and 
 it indirectly influences digestion. 
 
 2. The tongue has two nerves of taste, the fifth pair of cranial nerves 
 supplying the front, and the ninth pair the base. 
 
 3. So-called flavors affect the sense of smell more than that of taste. 
 
 4. The sense of smell tests food and air. 
 
 5. Agreeable odors promote respiration. 
 
 6. The ear consists of the outer, middle, and inner ear. In the 
 inner ear are the endings of the auditory nerve. 
 
 7. The semicircular canals have to do with the sense of equilibrium 
 and not with hearing. 
 
 8. Colds and catarrh often seriously affect hearing. 
 
 9. The larynx is very complicated. Various muscles moVe the car- 
 tilages and vary the length and tension of the vocal cords, and thus 
 produce the varying degrees of pitch. 
 
 10. The vocal cords are not cords, but are band-like ridges on the 
 sides of the larynx. 
 
 11. The higher animals have voice but not speech. 
 
 12. Whispering is speech without voice. 
 
 13. The larynx is affected by " colds " and catarrh. 
 
 Questions. i . How may the sense of taste be blunted ? 
 
 2. What is the effect of inhaling menthol ? 
 
 3. Does a person who is deaf in one ear hear " half as well " as before ? 
 
 4. Which of the senses goes to sleep first when we go to bed ? 
 
 5. In what order do the other senses go to sleep ? 
 
 6. In what order do the senses waken in the morning ? 
 
 7. Why does one become hoarse from hearing others shouting ? 
 
CHAPTER XXVI. 
 ACCIDENTS. WHAT TO DO TILL THE DOCTOR COMES. 
 
 How to Stop Flow of Blood from Arteries. In case of bleeding 
 from an artery the blood comes in jets. Pressure should be applied 
 between the cut and the heart. To know where to apply the pressure, 
 study the course of the main arteries. By examining Fig. 32 it will be 
 seen that the arteries to the arms pass down the inside of the upper 
 arm. Here they come near the surface. By putting a thick book or 
 roll under the armpit and pressing the arm down firmly, the artery may 
 be compressed. 
 
 Bleeding from the Upper Arm. In case of a deep cut in the lower 
 part of the arm, a handkerchief should have a knot tied in it, and the 
 knot placed over the artery ; that is, on the inside of the arm just below 
 the armpit. Pass the handkerchief around the arm and tie it loosely. 
 Then run a stick through it, and twist till the knot is drawn tightly 
 against the artery. Instead of a knot, a potato, or anything else to 
 make a firm lump, may be used. (See Fig. 32.) 
 
 Bleeding from the Neck. In studying the pulse, we found the 
 carotid artery in the neck. If a deep cut has been made in the upper 
 part of the neck, it may be possible to stop the flow by compressing 
 the artery lower down the neck. 
 
 Wounds in the Thigh. The femoral artery comes near the surface 
 in the groin. Pressure may be applied here in the same way to stop 
 bleeding from a cut farther down the thigh. In the angle back of the 
 knee, pressure may compress the artery supplying the leg. In case of 
 severe wounds, pressure should be applied immediately to the wound. 
 Sometimes it is well to make a plug of cloth and press upon the cut. 
 
 Bleeding from Veins. In case of bleeding from veins, holding the 
 part up may check the flow. If necessary to apply pressure, it should 
 be beyond the cut, instead of between it and the heart, as in the case of 
 the artery. 
 
 240 
 
Accidents. 241 
 
 Hemorrhage of the Lungs or Stomach. Blood from the lungs is 
 bright, frothy, and salty ; from the stomach is usually dark and sour. 
 In case of bleeding from the lungs or stomach, let the person rest 
 quietly on a lounge or easy-chair. Give him some bits of ice to swallow, 
 and call a physician. 
 
 Bleeding from the Nose. Nosebleed may sometimes be stopped by 
 pressing firmly at the base of the nose. Do not lean forward, as this posi- 
 tion aids the flow. Sit up, and hold up the head, and hold a cloth under 
 the nose. Apply cold water or ice to the nose and to the back of the 
 neck. If this does not stop it, inject cold water, with a little salt or 
 soda in it, into the nose. Often the flow may be stopped by pressing 
 firmly on the upper lip at the sides of the nose. If these attempts fail, 
 a long strip of cloth may be used to plug the nostril, pushing the cloth 
 in a little at a time, and leaving the 'ends so it can be pulled out. This 
 should not be removed till a long time after the flow is checked, as it 
 may start the bleeding afresh. After an attack of this kind avoid blow- 
 ing the nose, as this often starts bleeding again. 
 
 Treatment of Burns. Plunge the burned part into cold water. As 
 soon as possible apply a solution of cooking soda (a tablespoonful of 
 bicarbonate of soda to a teacup of water) ; or lay a wet cloth on the 
 burned part and put the soda on the cloth. Afterwards apply vaseline, 
 and renew the vaseline till the wound is healed. A mixture of equal parts 
 of sweet oil and limewater makes a good liniment for dressing burns. 
 
 Danger from Burning Clothing. If the clothing takes fire, there 
 is added to the danger of burning the body, the further risk of inhaling 
 the flame and heated air. It is best to lie down and roll or wrap the 
 body in any cloths at hand, rugs, shawls, etc. Running serves to fan 
 the flames. Hence, if a person whose clothing is on fire has lost 
 presence of mind and starts to run, throw him to the ground, putting a 
 wrap of some kind around the body at the same time if possible. Roll- 
 ing on the ground or floor in itself would very likely put out a small 
 flame. 
 
 Treatment of Fainting. Lay the body flat on the back. Keep the 
 crowd away, and give plenty of fresh air. Loosen the clothing about the 
 neck and waist. Sprinkle cold water on the face, but do not drench 
 the body with a quantity of water. Apply smelling salts (ammonia) to 
 the nostrils ; nib the limbs toward the body. If these remedies do not 
 soon restore consciousness, send for a physician. A faint is not usually 
 
242 Physiology. 
 
 a serious matter. Bad ventilation, disagreeable odors, or even the over- 
 sweet odors of such flowers as the tuberose, may cause fainting. 
 
 Broken Bones. Keep the patient as quiet as possible till the physi- 
 cian arrives. If there is inflammation, cold water may be applied. 
 Cooling applications are desirable in case of severe bruises. If it is 
 necessary to carry the patient, lay him on a board, or at least keep the 
 injured part as quiet as possible ; a cane or umbrella may be tied along- 
 side a leg, and supported by a pillow or a coat. Otherwise the sharp 
 ends of the bones may cut the flesh or even blood-tubes. 
 
 Sunstroke. Lay the patient in the shade and pour cold water over 
 the head. 
 
 Fig. 106. Resuscitation from Drowning. (Lincoln, 3 Figures.) 
 
 (Position I.) 
 
 TREATMENT OF THE DROWNED. 
 
 (As given by the Michigan Board of Health.} 
 
 RULE I . Remove all obstructions to breathing. Instantly loosen or 
 cut apart all neck and waist bands ; turn the patient on his face, with 
 the head down hill ; stand astride the hips with your face toward his 
 head, and, locking your fingers together under his belly, raise the body 
 as high as you can without lifting the forehead off the ground (Fig. 
 106, Position i), and give the body a smart jerk to remove mucus from 
 
Accidents. 
 
 243 
 
 the throat and water from the windpipe ; hold the body suspended long 
 enough to count slowly, one, two, three, four, five, repeating the jerk 
 more gently two or three times. 
 
 RULE 2. Place the patient on the ground face downward, and, main- 
 taining all the while your position astride the body, grasp the points of 
 the shoulders by the clothing, or, if the body is naked, thrust your fingers 
 into the armpits, clasping your thumbs over the points of the shoulders, 
 and raise the chest as high as you can (Fig. 107, Position 2) without 
 lifting the head quite off the ground, and hold it long enough to count 
 
 Fig. 107. Resuscitation from Drowning. 
 (Position 2.) 
 
 slowly one, two, three. Replace him on the ground, with his forehead 
 on his flexed arm, the neck straightened out, and the mouth and nose 
 free. Place your elbows against your knees, and your hands upon the 
 sides of his chest (Fig. 108, Position 3), over the lower ribs, and press 
 downward and inward with increasing force long enough to count 
 slowly one, two. Then suddenly let go, grasp the shoulders as before, 
 and raise the chest (Position 2), then oress upon the ribs, etc. (Position 
 3). These alternate movements should be repeated ten or fifteen times 
 a minute for an hour at least, unless breathing is restored sooner. Use 
 the same regularity as in natural breathing. 
 
244 
 
 Physiology. 
 
 RULE 3. After breathing has commenced, restore the animal heat. 
 Wrap him in warm blankets, apply bottles of hot water, hot bricks, or 
 anything to restore heat. Warm the head nearly as fast as the body 
 lest convulsions come on. Rubbing the body with warm cloths or the 
 hand, and slapping the fleshy parts, may assist to restore warmth, and 
 also the breathing. If the patient can surely swallow, give hot coffee, 
 tea, milk. Alcoholic liquors are liable to produce depression. Place 
 
 Fig. 108. 
 
 Resuscitation from Drowning. 
 (Position 3.) 
 
 the patient in a warm bed, and give him plenty of fresh air ; keep him 
 quiet. 
 
 Avoid Delay ! A moment may turn the scale for life or death. Dry 
 ground, shelter, warmth, stimulants, etc., at this moment are nothing 
 artificial breathing is everything is the one remedy all others are 
 secondary. Do not stop to remove wet clothing. Precious time is 
 wasted, and the patient may be fatally chilled by the exposure. 
 
 First restore Breathing. Give all your attention and effort to re- 
 store breathing by forcing air into, and out of, the lungs. If the breath- 
 ing has just ceased, a smart slap on the face or a vigorous twist of the 
 hair will sometimes start it again, and may be tried incidentally. 
 
Accidents. 245 
 
 Before natural breathing is fully restored, do not let the patient lie on 
 his back unless some person holds his tongue forward. The tongue by 
 falling backward may close the windpipe and cause fatal choking. 
 
 Prevent friends from crowding around the patient and excluding the 
 fresh air ; also from trying to give stimulants before the patient can 
 swallow. The first causes suffocation ; the second, fatal choking. 
 
 Do not give up too soon : you are working for life. Any time within 
 two hours you may be on the very threshold of success without there 
 being any sign of it. 
 
 Learn to Swim. Of course, persons who cannot swim ought not to 
 go out in a boat without taking along some sort of a float that may 
 serve as a life-preserver. Some of the rubber cushions serve well for 
 this. Every father neglects his duty if he does not teach his children, 
 girls as well as boys, to swim and to float. One cool, trained person 
 may save the lives of a whole boat load. 
 
 When a Boat Upsets. In case an ordinary rowboat is overturned, 
 one should not attempt to climb into it or upon it. It takes very little 
 to float a person in water, as the body is only a little heavier than 
 water ; in fact, if a person fills the lungs and lies back in the water his 
 face and nose will keep above water, and a person (at any rate without 
 clothing) can float in this way for some time if he breathes lightly. 
 Few persons have been taught these facts, and most of those who have 
 learned them lose their presence of mind, and waste their breath and 
 strength in wild and fruitless splashing. If a boat be overturned, those 
 who can swim should help those who cannot to get hold of the edge 
 of the boat, but not permit them to climb upon it. A small plank 
 will float a person if he does not try to lift much of his body out of 
 the water. 
 
 Suffocation in Wells. Persons are sometimes suffocated by carbon 
 dioxid in wells and cisterns. Before going down into a well, it is a 
 safe precaution to lower a lighted candle. If this is extinguished, a 
 warning is given. If a second person goes down after one who has 
 become unconscious, great care must be taken that two lives are not 
 lost. A rope should be firmly tied about the body, a hook, attached to 
 another rope, taken to catch into the clothing of the first, and the 
 rescuer should be lowered quickly and brought up immediately. A 
 small rope or large cord might be carried, by pulling which the signal 
 is given to pull up. In resuscitating from carbon dioxid suffocation use 
 
246 Physiology. 
 
 the same method as after drowning, except the first part, which is to 
 remove water from the windpipe, etc. 
 
 Poisons and their Antidotes. Several of the common drugs and 
 remedies kept about the house are more or less poisonous. The proper 
 antidote for each should be known and kept at hand. In the first place, 
 all such materials should be kept locked up so they will not be taken 
 by children, or by mistake, as in the haste of getting medicine in the 
 night. Again, all grown persons in the family should be instructed as 
 to the effects of each poison, and taught its antidote. As soon as any 
 new poisonous drug is bought, it should be made a point to read up 
 about it, and procure an antidote. Every one should know that 
 strychnin causes spasms, that opium brings on stupor, with contracted 
 pupils, etc. 
 
 Objects of Treatment. Treatment aims at three things, (i) to get 
 rid of the poison, (2) to neutralize what remains and prevent further 
 action, (3) to remedy the effects already produced. 
 
 1. Mtfstard a Common Emetic. The most common emetic is mus- 
 tard ; a tablespoonful in a cup of warm water ; give half of it, following 
 with free drinking of warm water, then give the rest of the mustard. 
 Do not wait for it to dissolve, but stir quickly and give at once. Pro- 
 voke vomiting by tickling the throat with a feather or with the finger. 
 If the mouth of the patient cannot readily be opened, insert the thumbs 
 inside the cheeks and back of the teeth. If mustard is not at hand, a 
 strong solution of table salt will serve. In a few cases, such as poison- 
 ing by ammonia, lye, etc., it is considered best not to administer an 
 emetic, but to try to neutralize the effect. 
 
 2. Neutralize the Poison. To neutralize a poison this general rule 
 should be known : an alkali may be neutralized by an acid, and vice versa. 
 For example, lye with vinegar, carbolic acid with alcohol and whiting 
 or magnesia, etc. Some acids and alkalis are always about a house. 
 
 3. Give Something Soothing. After any irritant poison some mild 
 and soothing substance should be given, white-of-egg, milk, mucilage 
 and water, flour and water, gruel, olive- or castor-oil. These materials 
 are partly for neutralizing the poison, and are also soothing in their 
 effect. If a patient is drowsy, some stimulant may be given, as strong 
 coffee (after opium) . Of course a physician should be sent for imme- 
 diately, as the after-treatment is of great importance. 
 
Accidents. 247 
 
 Wounds from Thorns and Rusty Nails. Promote bleeding by rub- 
 bing and pressing the wound and bathing with warm water. Or suck 
 the wound. This tends to remove any injurious matter. Apply 
 poultices. 
 
 Bites of Cats, Dogs, etc. If the animal is rabid (mad), suck the 
 wound and cauterize quickly. A poker or nail heated red hot is best 
 for cauterizing. If one cannot do this promptly, get lunar caustic with 
 which to cauterize ; strong acid or alkali, or a coal of fire, may be ap- 
 plied at once to the wound ; the coal on a cigar may be used. Do not 
 kill the animal if there is doubt. Keep it confined, and if it proves a 
 false alarm much anxiety will be saved. 
 
 Snake Bites. Apply ligatures around the part between it and the 
 heart. Suck the wound (there is no danger in this if there are no sores 
 or cracks in the skin of the mouth ; venom is not a stomach poison). 
 Then apply caustics, or a live coal. Wash the wound with vinegar or 
 strong salt solution. If ammonia water is at hand, add five teaspoon- 
 fuls to a pint of water and drink this. Ammonium carbonate, ten per 
 cent solution, is also highly recommended. A teaspoonful dose should 
 be given immediately, and repeated twice at intervals of ten minutes. 
 To bee stings, apply soda or dilute ammonia. 
 
 Poison Ivy. The itching and discomfort may be relieved by bath- 
 ing the part in a mixture of two teaspoons of carbolic acid (pure), two 
 tablespoons of glycerin, one half pint of water or rose-water. 
 
 The Sick-room. Every boy and girl ought to learn something about 
 the care of the sick, as any one is likely to be called on to do this 
 kind of work. Good nursing is often " half the battle." The patient 
 should have a cheerful room, but the bed should be so placed that he 
 will not face the light. Evidence of illness, such as medicine bottles, 
 etc., should be kept out of sight so far as possible. While it is not 
 best to deceive the patient as to his condition, there should at all times 
 be kept up an air of cheerfulness and hope. If the physician can 
 inspire with confidence, and the nurse give unflagging good cheer, the 
 chances of recovery are greatly improved. Nothing sustains like hope. 
 Keep the air of the room pure. Remove excreta and everything offen- 
 sive just as soon as possible. Do not rely on feeling as to temperature, 
 but keep a thermometer in the room. 
 
 Sympathy with the Patient. One of the necessary characteristics 
 of a good nurse is the power of imagination. " How would I feel, and 
 
248 Physiology. 
 
 what would I like to have done, if I were in his place?" This feeling 
 will lead the nurse frequently to raise the patient's head and turn the 
 pillow the coolness of the other side of the pillow is refreshing; to 
 give sips of cool water ; to see that the patient does not suffer for want 
 of a bath. 
 
 Bathing the Sick. In bathing a weak person only a part of the 
 body should be moistened at a time ; after this part is thoroughly dried, 
 another part may be washed; it is often necessary to do all this work 
 under the bed clothing. 
 
 Changing the Bedding. In changing the bed clothing move the 
 patient to one side of the bed, push the clothing along close to his 
 body, and place the clean bedding on the other side ; then move the 
 patient back, remove the soiled linen, and smooth out the clean. It is 
 often necessary to warm the sheets first; they should be thoroughly 
 dry. 
 
 Follow Physician's Directions Faithfully. Have the physician's 
 directions written out plainly, as they may be forgotten ; and if there is 
 a change of nurses during the night there is less chance of mistake. 
 Never let yourself get drowsy when acting as nurse. Get up and walk 
 about, get a breath of fresh air, and if inclined to be drowsy do not 
 allow yourself to settle back in an easy-chair. If watching all night, 
 take a good lunch in the middle of the night ; coffee may help to keep 
 you awake. 
 
 Sweeping the Sick-room. Do not allow the room to be swept with 
 the ordinary broom. The room should have rugs that can be removed 
 and shaken, and the floor wiped with a moist cloth. If the room is 
 carpeted, it may be swept with moist salt, tea-grounds or coffee-grounds, 
 sawdust, etc. Any dusting should be avoided ; furniture may be wiped 
 with a damp cloth. 
 
 Do not Whisper. Do not whisper, as it disturbs more than talking, 
 and also has an air of secrecy that rouses suspicion in the patient. 
 
 Food for the Sick. Raise the head with the hand, or bolster the 
 patient up, when giving drink ; or if the patient is very weak, use a 
 rubber or glass tube, so that he will not have to lift the head. The 
 nurse should know how to prepare any food that may be needed during 
 the night. An oil stove or gas stove is very desirable for cooking, or 
 heating poultices, as an ordinary wood or coal fire is likely to die down, 
 
Accidents. 249 
 
 making it impossible for the nurse to do this work quickly, as it is often 
 necessary to take advantage of a favorable time, as when the patient 
 wakens. 
 
 Care of Lamps. Most lamps, when turned low, give off a disagree- 
 able gas. It is better to have a very small lamp burning at full height 
 than a large one turned low ; sperm candles are recommended. Do not 
 let the light shine into the patient's face. 
 
 To Prevent Sneezing. It is well known that a sneeze may be pre- 
 vented by firmly pressing on the upper lip. This may enable a nurse 
 to keep from waking a very sick patient when, at a critical point, sleep 
 is almost a question of life or death. And it is a convenient fact for 
 any one to know. To prevent coughing, a sip of cold or hot water will 
 relieve the tickling in the throat. 
 
 Summary. i . To stop flow of blood from an artery apply pressure 
 to the wound, or between the wound and the heart. 
 
 2. To stop flow of blood from a vein apply pressure to the wound or 
 beyond the heart. 
 
 3. Leaning forward promotes, instead of checks, nosebleed. 
 
 4. In case of a burn apply cooking soda. 
 
 5. If the clothing takes fire, lie down and roll, or wrap a rug or shawl 
 about the body. 
 
 6. If a person with clothing on fire loses his presence of mind, seize, 
 throw down, and wrap in any woolen clothing. 
 
 7. In case of fainting lay the body flat on the back, loosen clothing, 
 give fresh air, and sprinkle lightly with cold water ; if this does not 
 revive, rub the limbs toward the body, hold to the nostrils smelling- 
 salts (or ammonia), and send for a physician. 
 
 8. Before going down into a well, test the air by lowering a lighted 
 candle. 
 
 9. Learn the antidotes of every poison in your house as soon as it is 
 bought, and keep the antidote at hand. 
 
 10. Volunteer to help take care of sick friends, and learn to do this 
 work well. 
 
 Questions. I. How does holding up the wounded part check bleed- 
 ing ? 
 
 2. What other methods of resuscitation from drowning are in use ? 
 
 3. What are some of the poisonous substances commonly kept in 
 the house ? 
 
 17 PHY 
 
CHAPTER XXVII. 
 VACCINATION. 
 
 Conditions before the Discovery of Vaccination. Before the dis- 
 covery of the value of vaccination by Dr. Edward Jenner in 1796, small- 
 pox was so prevalent that nearly everybody had it, and many thousands 
 died from it every year, while other thousands were left blind or terribly 
 scarred. Jenner discovered that persons who have had a disease called 
 vaccinia, or cowpox, are much less liable to be attacked by smallpox, 
 and that, if they are so attacked, the disease is not apt to be severe 
 or dangerous. Before Jenner made this discovery any person who 
 had had a mild attack of smallpox was considered fortunate, as those 
 who have had the disease once are not liable to have it again. Since 
 nearly everybody had it before Jenner's time, those who had had a 
 mild attack were looked upon as having escaped a very great calamity. 
 Nearly everybody in those days was scarred more or less with small- 
 pox pits. It was customary when servants were employed to hire none 
 who had not had smallpox, so that the employer might not be put to 
 the trouble and expense of having to take care of a smallpox patient. 
 So universal was smallpox and so terrible were its results that it was 
 proposed, before Jenner discovered the benefits of cowpox, to inoculate 
 everybody with the virus from a mild case of smallpox, thus making 
 sure that everybody should have it, in the hope that if the disease 
 were thus acquired from mild cases it would be less dangerous. But 
 Jenner's discovery that cowpox is a preventive of smallpox, and that 
 cowpox is a comparatively harmless disease, soon changed the whole 
 condition of affairs. Vaccination that is, inoculation with the virus 
 of cowpox, instead of inoculation with the virus of smallpox became 
 common. 
 
 Value of Vaccination. The best medical authority in every civilized 
 country in the world supports the proposition that vaccination, more 
 than all other causes combined, accounts for the fact that nowadays in 
 those places where it is thoroughly carried out smallpox is not a preva- 
 
 250 
 
Vaccination. 251 
 
 lent disease, that very few deaths result from it, and that one seldom 
 sees a person who has been disfigured by it. And there are many 
 illustrations in medical literature, both in olden and in modern times, 
 of the fact that, when vaccination is thoroughly practiced, smallpox 
 almost entirely disappears, to break out again when vaccination has 
 been neglected, and to disappear again when vaccination is resumed. 
 London has furnished such illustrations many times ; and the same has 
 happened in many other cities, such as Boston, Birmingham, Liverpool, 
 and Montreal. In Montreal, for instance, vaccination had been generally 
 practiced for many years, and there had been practically no smallpox in the 
 city during that time. But, about forty years ago, many of the people 
 of Montreal refused to permit their children to be vaccinated. When, 
 in the winter of 1885, a colored Pullman-car porter arrived in Montreal 
 sick with smallpox, the disease found a fertile field in which to spread. 
 Before many months had passed thousands of the people of Montreal 
 had had the disease, three thousand of them had died from it, and other 
 thousands were left maimed and scarred. It was found, however, that, 
 as is always the case, very few of those who had been vaccinated were 
 attacked by smallpox, the disease taking as its victims almost solely 
 those who had not been vaccinated. 
 
 Harmless. Vaccination is practically painless and harmless. The 
 disease it causes, cowpox, or vaccinia, is also, compared with smallpox, 
 a harmless disease. Now and then somebody dies after being vacci- 
 nated. But out of the many millions who are vaccinated every year, only 
 a very few die as a remote result of it. Without vaccination smallpox 
 would be prevalent and kill thousands. 
 
 Those who are opposed to vaccination claim that it does not protect 
 from smallpox ; that it causes other diseases, such as tuberculosis, or 
 consumption, scrofula, and tetanus, or lockjaw ; that it is more dangerous 
 than smallpox, which, they claim, cannot nowadays become epidemic 
 because of the greater cleanliness and better sanitary conditions which 
 surround us. 
 
 Medical Authority. The fact still remains, however, that the best 
 medical authority in all civilized countries maintains that none of the 
 claims of those who oppose vaccination is founded on facts. The 
 best medical authorities say that very few, if any, of the many mil- 
 lions who are vaccinated every year contract consumption or other 
 disease from it. They show, also, that many people die every year 
 
252 Physiology. 
 
 from lockjaw as the result of infection with the lockjaw poison absorbed 
 through scratches no deeper than those inflicted in vaccinating. They 
 point out that any open wound may become infected with the poison of 
 lockjaw. Also that, while it requires only ten days for the poison of 
 lockjaw to develop, in most of the very few cases that have followed 
 vaccination the disease has broken out more than ten days after the 
 vaccination operation was performed. This, they claim, proves that 
 the lockjaw was not the result of vaccination, but, as may happen after 
 any other scratch, resulted from the lockjaw poison finding an open 
 wound through which to enter the body. 
 
 If proper care be taken thoroughly to cleanse the skin before vacci- 
 nation is performed, if pure vaccine virus be used, and if the little wound 
 and the vaccination sore be kept protected from infection with disease 
 germs from the air, the danger from vaccination is very slight. 
 
CHAPTER XXVIII. 
 STIMULANTS AND NARCOTICS. 
 
 Stimulants. A stimulant, in the physiological sense, is anything 
 which causes an increase of vital activity in any of the organs of the 
 body. 
 
 Food is, therefore, a stimulant, because it increases the vital activity 
 of the organs of the body. Heat and cold, in their first effects, are 
 stimulants, for they increase the vital activity of the organs to which 
 they are applied. To illustrate, either heat or cold will cause the skin 
 first to whiten and then to redden, and heat will cause perspiration to 
 flow from the sweat glands. 
 
 Alcohol, tobacco, opium, morphine, tea, coffee and many other 
 things are also stimulants, because their first action after being taken 
 into the body is to increase the vital activity of some of the organs. 
 All the above-mentioned stimulants affect, among other organs, the 
 heart, nervous system, and brain ; and their effects are seen first in these 
 organs. 
 
 Narcotics. A narcotic, in the physiological sense, is anything which 
 quiets the nervous system and brain, relieves pain, and produces sleep. 
 
 All narcotics are, in their first effects, stimulants ; and all stimulants 
 are, in their secondary effects, narcotics. So it may be said that stimu- 
 lants are narcotics in small quantities and that narcotics are stimulants 
 in large quantities. 
 
 To illustrate again with heat and cold : one of the effects of a hot 
 bath is to redden the skin, showing its stimulating effect. In a little 
 while, however, the whole body becomes languorous and sleepy. One 
 of the effects of cold is to redden the skin ; but, as every one knows, if 
 the cold continue long enough, the person becomes drowsy and falls 
 into a deep sleep. Where one * freezes to death " he dies in a profound 
 sleep. 
 
 Effects of Large and Small Quantities. Alcohol, tobacco, opium and 
 morphine are all stimulants and all narcotics ; they are stimulants when 
 
 253 
 
254 Physiology. 
 
 used in small quantities and narcotics when used in large quantities. 
 Thus, a glass of wine or beer sets the heart to beating more rapidly, 
 the stimulating effect ; but many glasses of either will make him who 
 takes them drowsy and finally put him into a drunken sleep, the 
 narcotic effect. 
 
 We look upon morphine and opium as examples of narcotics because 
 they are used in medicines to quiet the nervous system, stop pain and 
 produce sleep. Yet small doses of either have, apparently, only stimu- 
 lating effects, for the reason that the various organs are able to resist 
 the effects of small doses and, therefore, do not become narcotized. 
 
 A weary horse is whipped to make him go faster or pull harder. The 
 faster he goes or the harder he pulls, the more tired he becomes, and, 
 therefore, the more the whipping that is necessary to keep him going. 
 The whip may be called a stimulant to the tired horse, because it pro- 
 duces an increase in his activity. But when the work is done, the 
 horse is very tired indeed and requires a long rest before he can work 
 well again. Indeed, if the horse be compelled, by the stimulating effect 
 of the whip, to run or pull too hard and too long, he may fall down 
 exhausted, and may even die. 
 
 Effect of Continued Use. Alcohol, tobacco, morphine, or opium are, 
 like the whip to the horse, stimulants, in their first effects, to the bodies 
 of those who use them. Like the whip also, they will, if taken in too 
 great quantities, bring even death to those who use them. 
 
 Even the most mettlesome and high-spirited horse would, if the whip 
 were constantly used upon him, get so used to it that he would not 
 work without being whipped. Worse than that, the more accustomed 
 he gets to the whip, the more and the harder it must be used upon him, 
 until, finally, he will not work unless he be whipped unmercifully all the 
 time Such a horse is of no use, and his cruel master has spoiled one 
 of man's best friends. 
 
 Any person who uses stimulants continuously is whipping his own 
 body, as the cruel master does his horse. As in the case of the horse, 
 the more the body is whipped, the more whipping it requires to make it 
 do its work, until it will not work at all unless it be constantly whipped ; 
 that is, constantly under the influence of stimulants. A horse that will 
 not work unless it is constantly whipped is a poor sort of a horse. A 
 man who will not, or cannot, work unless he is under the influence of 
 stimulants is rather a poor sort of a man. We call a person cruel who 
 
Stimulants and Narcotics. 255 
 
 whips his horse ; a man is cruel to himself if he allows himself to get 
 into such a condition that he must whip his body with stimulants to 
 compel it to work. 
 
 Danger in Forming Habits. Many people drink alcoholic liquors 
 and never become drunkards. Yet many people do become drunkards. 
 In fact, any person, particularly one who begins in youth and who con- 
 tinuously uses alcoholic liquors, is very liable indeed to become a slave 
 to drink and die a drunkard. But those who continuously use alcoholic 
 liquors run serious danger in other ways, even though they may never 
 become drunkards. For alcohol goes into the blood when it is taken 
 into the stomach, and, therefore, comes in contact with every organ of 
 the body. The action of even small amounts of alcohol in the blood is 
 very apt, if kept up for a long time, to produce disease of the kidneys, 
 liver, stomach, heart, nerves and brain, and thus cause the death of 
 those who, though never drunk, are still slaves to alcohol. These are 
 well-known medical facts. 
 
 Especially Dangerous to the Young. The danger from stimulants is 
 especially great when used by young and growing persons. They 
 require all the nervous energy that their bodies produce to keep their 
 organs growing besides doing their proper work. If, therefore, these 
 organs be whipped by stimulants, they become accustomed to them and 
 will not, or cannot, properly work without them. The result is that the 
 various organs of the body, especially the heart, brain and nervous 
 system, do not develop properly. Worst of all, there is the greatest 
 danger that such a person will become a slave to the particular stimu- 
 lant he may be using. Thus it happens that so many boys and young 
 men become drunkards. They drink wine, beer and whisky; their 
 growing bodies cannot withstand the effects of the stimulation, and 
 finally, before they realize it, they become habitual drunkards. 
 
 Stimulants both Unnecessary and Injurious. That stimulants are 
 not only unnecessary but even positively injurious is proven by the fact 
 that no person who is training for any feat of strength, skill, or endurance, 
 ever uses any of them, except, perhaps, a little weak tea or coffee. No 
 one ever heard of a person training for a football or a baseball match, 
 for a foot-race, for a rowing match, or for any other feat of strength, skill, 
 or endurance, ever drinking any alcoholic liquors^ or using tobacco, 
 opium, or morphine. If they were good things, they would surely be 
 
256 Physiology. 
 
 used under these circumstances where strength and endurance are re- 
 quired ; if they were not injurious, they would not be prohibited. The 
 cigarette is denied the college boy who is training for the college game ; 
 and -if he breaks the rule, he is debarred from the games because the 
 trainers know that such practice on his part weakens his heart and his 
 wind, and that even one cigarette may result in the loss of a closely 
 contested game requiring endurance on the part of every player. 
 
 Drunkenness. Too much alcohol taken into the body will make the 
 person who drinks it intoxicated or drunk. He staggers, sees double, 
 cannot talk plainly, is foolish and silly in his talk, and cannot think 
 well ; or he becomes excited and violent, wants to fight, imagines that 
 he is being insulted, and, crazed as he is, sometimes even kills his best 
 friend. 
 
 After a while the drunken man, like the whipped horse, becomes 
 exhausted. His muscles, his brain and his whole body are tired out by 
 the extra work the stimulants have made them do, and he falls into a 
 drunken sleep, from which he cannot be easily aroused ; the narcotic 
 effect of the alcohol has shown itself. Indeed, it not infrequently hap- 
 pens that the poor drunkard does not wake up at all ; but his heart and 
 brain, worn out by the over-stimulation of the alcohol he has drunk, 
 stop working, and he dies, like the horse which has been lashed beyond 
 his strength by his cruel driver. 
 
 How often it happens that drunken men commit murder ; many 
 railroad accidents, bringing death or terrible injuries to thousands of 
 people, have been due to the alcohol-beclouded brains of engineers, 
 switchmen and train dispatchers. Our prisons and jails are crowded 
 with convicts, most of them young men, who committed some crime 
 while under the influence of liquor, not necessarily drunk, maybe having 
 taken only a glass or two. Railroad, bank, and steamship companies, 
 which are responsible for lives and property, have found by experience 
 that it is not safe to employ men who use liquor habitually, even though 
 they never become intoxicated. 
 
 Criminals. The great majority of our criminals, a large share of our 
 insane, very many of our deaths, most of our murders, practically all the 
 poverty, want, starvation and sickness in the crowded portions of our 
 cities, are due directly or indirectly to the use of liquor. 
 
 Many people, it is true, drink wine and beer and even whisky and 
 
Stimulants and Narcotics. 257 
 
 never become drunkards. But any boy or young man who does this 
 runs a great risk of becoming a slave to alcohol and ruining his health, 
 even if he does nothing worse. 
 
 Tobacco. Tobacco, like alcohol, is both a stimulant and a narcotic ; 
 it affects the heart and the nervous system. It is not so dangerous to life 
 as alcohol ; it does not fill our jails and insane asylums as alcohol does. 
 But it is particularly injurious to the growing boy. It weakens his heart 
 and disturbs his nervous system and dulls his brain. 
 
 Many boys use tobacco and think that it does them no harm. But 
 let them go to a doctor and have their hearts examined, and it will be 
 found that that organ is weaker than it should be. If tobacco-using 
 boys are attacked by such diseases as typhoid fever or pneumonia, they 
 are much more liable to die from heart failure than if they had not used 
 tobacco. Such boys cannot run so fast nor so far, play marbles, foot- 
 ball, or baseball so well or do any athletic feat so skillfully, as they 
 could if they did not use tobacco. These are well-established medical 
 facts, so well known that no person who is training boys or men for 
 any game or athletic event will permit any of those under his care to 
 use tobacco in any form. 
 
 Gcown-up people can use tobacco, as they can alcohol, with less danger 
 to themselves than growing boys can. But even adults who use tobacco 
 are liable to have weak hearts. In fact, many men are refused life in- 
 surance because their hearts are weakened by tobacco. Such men are 
 liable to die from heart failure if they run for a street car or make 
 any unusual exertion, and pneumonia or any other severe attack of ill- 
 ness is liable to kill them. 
 
 It is true some boys use tobacco and do not appear to be injuri- 
 ously affected by it, and many men use it and die of old age. But it 
 is the fact, nevertheless, and all medical men will bear witness to the 
 truth of it, that many boys ruin their health by using tobacco, and that 
 no boy can be so strong, so quick, so skillful at his games, or so easily 
 get through school, if he smokes cigarettes or uses tobacco in anv form. 
 If these things are true, and they are true, any boy who uses tobacco is 
 foolish. 
 
 To this many boys will reply, '' Isn^t a man who uses tobacco fool- 
 ish?" Yes, he is. But the danger and damage from tobacco to the 
 growing boy are greater than to the grown man, simply because the boy 
 is growing and the man is grown. 
 
258 Physiology. 
 
 Opium. Opium is the dried juice of a certain kind of poppy. It 
 contains a number of different substances, one of which is morphine, to 
 which it principally owes its narcotic and stimulant effects. 
 
 Opium is used by the people of some nations as a stimulant. The 
 Chinese, for instance, are addicted to the vice, and many of our people 
 have learned from them to smoke opium. Most of our confirmed 
 criminals, the poor outcasts who spend most of their lives in prison, are 
 slaves to the alcohol and opium habits. In almost every Chinatown in 
 California may be found rooms where opium is smoked by white people, 
 and most of the poor victims of this terrible habit are youths and young 
 men. This is so because grown people seldom get close enough to the 
 Chinese to acquire the habit, only idle boys and youths having time and 
 inclination to loiter about the Chinese quarters. Those who learn to use 
 opium soon resort to crime to get money with which to buy the deadly 
 stuff, and soon go to jail, or else die. So that the white patrons of the 
 opium dens are mostly young people. 
 
 It is pitiable, as well as disgusting, to see the poor fools who have 
 become opium smokers. They have lost all sense of shame and are 
 content to associate with the Chinese in their dirty, ill-smelling houses. 
 They will borrow from their friends, if they have any, beg upon the 
 streets, lie, steal, do almost anything that is shameful, in order to get a 
 little money with which to buy opium. They are pale, trembling and 
 haggard ; their clothes are dirty and ragged, and they soon go to prison 
 for stealing, or as common vagrants, or they die. 
 
 A certain small proportion of those who use alcohol to excess reform ; 
 but one who becomes a slave to opium seldom if ever reforms. Like 
 the horse that is used to the whip, his organs will not work without 
 being lashed by the stimulating effects of the opium. If he be deprived 
 of it, he cannot eat, and is nervous and ill-tempered. He cannot go to 
 sleep until he is worn out, and when he does doze off he has horrible 
 dreams. He cannot work, read, or enjoy himself in any way. All that 
 he thinks about is opium. He aches in every bone and muscle and nerve, 
 and his sufferings become so intense that he will stoop to any meanness 
 or commit almost any crime to obtain the stuff that has deprived him of 
 his manhood and made him a slave to a more cruel and unrelenting 
 master than he who whips his poor horse to death. 
 
 Morphine. Morphine is also used as a stimulant. The morphine user 
 is, like the opium user, an absolute slave to the habit. Once begun, the 
 
Stimulants and Narcotics. 259 
 
 use of the stuff is very rarely if ever stopped. Its victims cannot work 
 without it and soon become so unreliable that no one will employ them. 
 Yet both opium and morphine are medicines of the greatest value 
 when used by physicians for the cure of disease. But used for any 
 other purpose, or without the direction of a physician, they are deadly 
 poisons, sure to bring those who use them to the lowest depths of 
 degradation, sure to make them criminals and beggars, sure to send 
 them down to shameful deaths and paupers' graves. 
 
 MILDER STIMULANTS. 
 
 Tea, Coffee and Cocoa, or Chocolate, are mild stimulants. But even 
 they, when used to excess, may produce various nervous troubles. They 
 act upon the heart and nervous system, and, like all other stimulants, 
 should bfe carefully avoided by the young and growing. 
 
 PATENT MEDICINES. 
 
 There are many people who, though opposed to the use of alcoholic 
 beverages of any kind, do not hesitate to take, as medicine, so-called 
 " bitters " and other patent medicines, many of which contain alcohol 
 in great or less quantities, and which, therefore, are as intoxicating as 
 wine or beer or even whisky. Such people think that their health is 
 bad ; and they ascribe to " the medicine " the temporary stimulating 
 effect of the alcohol, which, unknown to themselves, they are taking. 
 Unconsciously they take more and more of the stuff, not realizing that 
 they are becoming addicted to the liquor habit just as much as if they 
 were drinking any other alcoholic liquors. 
 
 Such people would be very indignant if they were told that they were 
 doing that which they condemn in others ; viz., drinking intoxicating 
 liquors. Yet such is the fact, and the worst part of it is that the alcohol 
 usually found in such so-called " medicines " is of the cheapest, most 
 poisonous kind, and, therefore, like the cheapest wines, beers, and 
 whiskies, is very destructive to health. 
 
GLOSSARY. 
 
 Albumen (al-bu'-meri). The white of an egg. 
 
 Albumin (al-bu'-min). A proteid substance, the chief constituent of 
 the body. Its molecule is highly complex, and varies widely within 
 certain limits in different organs and in different conditions. 
 
 Albuminuria (al-bu'-mi-nu'-rl-a}. The presence of albumin in the urine, 
 indicating changes in the blood or in the kidneys. 
 
 Amylopsin (am-i-lop'-siri). A ferment said to exist in pancreatin. 
 
 Anabolism (an-ab'-o-lizm'). Synthetic or constructive metabolism. 
 Activity and repair of function ; opposed to katabolism. 
 
 Arbor Vitae (ar'-ftor m'-ie}. A term applied to the branched appear- 
 ance of a section of the cerebellum. 
 
 Argon (ar'-f/on). A newly discovered element similar to nitrogen 
 (found in the air). 
 
 Arytenoid (ar-i-tt'-noid). Resembling the mouth of a pitcher, as the 
 arytenoid cartilages of the larynx. 
 
 Atlas (at'-las). The uppermost of the cervical vertebrae (from the 
 mythical Atlas who supported the Earth). 
 
 Auricle (aw'-ri-kl). The auricles of the heart are the two cavities be- 
 tween the veins and the ventricles. Also, the pinna and external 
 meatus of the ear. 
 
 Axis (ak'-sis). The second cervical vertebra, on which the head, with 
 the atlas, turns. 
 
 Bacterium (bak-te'-ri-um}, pi. bacteria. A genus of microscopic fungi 
 characterized by short, linear, inflexible, rod-like forms without 
 tendency to unite into chains or filaments. 
 
 Biceps (bl'-seps}. Biceps brachii, the flexor of the arm. 
 
 Bicuspid (bi-kus'-pid} . Having two points ; the bicuspid or premolar 
 teeth ; the bicuspid valve, between the left auricle and the left ven- 
 tricle. 
 
 Brachial (bra'-ke-al or brak'-i-al}. Pertaining to the arm. 
 
 261 
 
262 Glossary. 
 
 Bronchus (brong' -kits'), pi. bronchi. The two tubes into which the tra- 
 chea divides opposite the third thoracic vertebra, called respectively 
 the right and left bronchus. 
 
 Caffein (kaf-e-in). An alkaloid that occurs in the leaves and beans of 
 the coffee-tree, in Paraguay tea, etc. 
 
 Canaliculus (kan-a-lik'-u-lus*), pi. canaliculi. The crevices extending 
 from lacunae, through which nutrition is conveyed to all parts of 
 the bone. 
 
 Canine (ka-nin' or ka'-nlri}. The conical teeth between the incisors 
 and the premolars. 
 
 Capillary (kap'-i-la-ri or ka-pil'-a-ri) . A minute blood-tube connecting 
 the smallest ramification of the arteries with those of the veins. 
 
 Capsule (kap'-sul}. A tunic or bag that incloses a part of the body or 
 an organ. 
 
 Carbohydrate (kar-bo-hi'-drat). An organic substance containing six 
 carbon atoms or some multiple of six, and hydrogen and oxygen in 
 the proportion in which they form water; that is, twice as many 
 hydrogen as oxygen atoms. Starches, sugars, and gums are carbo- 
 hydrates. 
 
 Cardiac (kar'-di-ak). Pertaining to the heart. 
 
 Carotid (ka-rot'-id). The principal right and left arteries of the neck. 
 
 Carpus (kar'-pus). Belonging to the wrist; as the carpal bones. 
 
 Cartilage (kar'-ti-laj*). Gristle of various kinds, articular, etc. 
 
 Casein (M'-se-w). A derived albumin, the chief proteid of milk, pre- 
 cipitated by acids and by rennet at 40C. 
 
 Cecum (se'-kum'). The large blind pouch or cul-de-sac, in which the 
 large intestine begins. 
 
 Centrum (sen'-trum). The center or middle part ; the body of a verte- 
 bra, exclusive of the bases of the neural arches. 
 
 Cerebellum (ser-e-bel'-uin). The inferior part of the brain, lying below 
 the cerebrum. 
 
 Cerebrum (ser'-e-brurri}. The chief portion of the brain, occupying the 
 whole upper part of the cranium. 
 
 Cervical (ser'-vi-kal). Pertaining to the neck, as cervical vertebrae. 
 
 Chordae tendineae (kor'-de). The tendinous cords connecting the 
 fleshy columns of the heart with the auriculo-ventricular valves. 
 
 Choroid (ko'-roid}. The second or vascular coat of the eye, continu- 
 ous with the iris in front, and lying between the sclerotic and the 
 retina, 
 
Glossary. 263 
 
 Chyle (HZ). The milk-white fluid absorbed by the lacteals during di- 
 gestion. 
 
 Chyme (Hm). Food that has undergone gastric digestion, and has not 
 yet been acted upon by the biliary, pancreatic, and intestinal 
 secretions. 
 
 Cilium (siZ'-z-wm), pi. cilia. The eyelashes ; also the hair-like appen- 
 dages of certain epithelial cells, whose function is to propel fluid 
 or particles along the passages that they line. 
 
 Ciliary (sH'-i-a-ri). Pertaining to the eyelid or eyelash ; also by ex- 
 tension to the ciliary apparatus or the structure related to the 
 mechanism of accommodation. Pertaining to the cilia, 
 
 Circumvallate (sir-kum-nal'-at}. Surrounded by a wall or prominence, 
 as the circumvallate papillae on the tongue. 
 
 Clavicle (klav'-i-kl). The collar-bone. 
 
 Coccyx (kok'-siks*). The last bone of the spinal column, formed by the 
 union of four rudimentary vertebrae. 
 
 Cochlea (kok'-U-a). A cavity of the internal ear, resembling a snail- 
 shell. 
 
 Conjunctiva (kon-jungk-ti'-va). The mucous membrane covering the 
 anterior portion of the globe of the eye, reflected on, and extending 
 to, the free edge of the lids. 
 
 Corpus Arantii (kor'-pus}. The tubercles, one in the center of each 
 segment of the semilunar valves. 
 
 Corpuscle (kor'-pus-l}. A name loosely applied to almost any small, 
 rounded or oval body, as the blood corpuscles. 
 
 Cortex (kor'-teks}. Bark. The outer layer of gray matter of the brain ; 
 the outer layer, cortical substance, of the kidney. 
 
 Cricoid (krl'-koid}. Ring-shaped, as the cricoid cartilage of the 
 larynx. 
 
 Dentine (den'-tiri). The ivory-like substance constituting the bulk of 
 the tooth, lying under the enamel of the crown and the cement 
 of the root. 
 
 Diabetes (di-a-be'-tez}. The name of two different affections, diabetes 
 mellitus, or persistent glycosuria, and diabetes insipidus, or polyu- 
 ria, both characterized, in ordinary cases, by an abnormally large 
 discharge of urine. The former is distinguished by the presence 
 of an excessive quantity of sugar in the urine. 
 
 Dialysis (dl-al'-i-sis}. The operation of separating crystalline from 
 colloid substances by means of a porous diaphragm, the former 
 
264 Glossary. 
 
 passing through the diaphragm into the pure water upon which the 
 dialyzer rests. 
 
 Digastric (di-gas'-trik}. Having two bellies, as the digastric muscle, 
 enlarged near each end and with a tendon in the middle. 
 
 Duodenum (du-o-de'-num}. The first part of the small intestine, begin- 
 ning with the pylorus. 
 
 Emulsion (Je-mul'-shun). Water or other liquid in which oil, in minute 
 subdivision of its particles, is suspended. 
 
 Enamel (en-am'-el}. The hard covering of the crown of a tooth. 
 
 Endothelium (en-do-the'-li-um}. The internal lining membrane of 
 serous, synovial, and other internal surfaces, the homolog of epi- 
 thelium. 
 
 Enzyme (en'-zim). Any chemic or hydrolytic ferment, as distinguished 
 from organized ferments such as yeast; unorganized ferment. 
 
 Epiglottis (ep-i-glot'-is). A thin nbro-cartilaginous valve that aids in 
 preventing food and drink from passing into the larynx. 
 
 Esophagus (e-sof-a-guti}. The musculo-membranous tube extending 
 from the pharynx to the stomach. 
 
 Eustachian (u-sta'-ki-an). Eustachian tube, the tube leading from the 
 middle ear to the pharynx. 
 
 Facet (fas'-et). A small plane surface. The articulating surface of a 
 bone. 
 
 Femur (/e'-mer). The thigh-bone. 
 
 Ferment (fer'-menf). Any micro-organism, proteid, or other chemic 
 substance capable of producing fermentation, i.e., the oxidation 
 and disorganization of the carbohydrates. 
 
 Fibrin (fl'-brin~). A native albumen or proteid, a substance that, be- 
 coming solid in shed blood, plasma, and lymph, causes coagulation 
 of these fluids. 
 
 Fibula (fib'-u-la^). The smalter or splint bone in the outer part of the 
 leg, articulating above with the tibia, and below with the astraga- 
 lus and tibia. 
 
 Filiform (fil'-i-form}. Thread-like, as the filiform papillae. 
 
 Frontal (fron'-tal}. Belonging to the front, as the frontal bone. 
 
 Fungiform (fun'-ji-form). Having the form of a mushroom, as fungi- 
 form papillae. 
 
 Ganglion (gang'-gli-on\ pi. ganglions or ganglia. A separate and semi- 
 independent nervous center, communicating with other ganglia or 
 nerves, with the central nervous system, and peripheral organs. 
 
Glossary. 265 
 
 Gastric (gasf'trik*). Pertaining to the stomach. 
 
 Gelatin (jel'-a-tin}. An albuminoid substance of jelly-like consistence, 
 obtained by boiling skin, connective tissue, and bones of animals 
 in water. The glue of commerce is an impure variety. 
 
 Glosso-pharyngeal (ylos'-o-fa-rin'-$e-al}. Pertaining to the tongue and 
 larynx. 
 
 Gluten (ylo'-ten). A substance resembling albumin, and with which it 
 is probably identified ; it occurs abundantly in the seeds of cereals. 
 
 Glycogen (fjli'-ko-jen}. A white amorphous powder, tasteless and odor- 
 less, forming an opalescent solution with water, and insoluble in 
 alcohol. It is commonly known as animal starch. It occurs in the 
 blood and in the liver, by which it is elaborated, and is changed by 
 diastasic ferments into glucose. 
 
 Gustatory (gus'-td-to-ri). Pertaining to the special sense of taste and 
 its organs. 
 
 Hashish (hash'-esJi). A preparation from Indian hemp, Cannabis in- 
 dica. It is a powerful narcotic. 
 
 Haversian (ha-ver'-ziany. Haversian canal, in bone, a central opening 
 for blood-tubes, surrounded by a number of concentric rings, or 
 lamellae, of bone. 
 
 Hemoglobin (hem-o-ylo'-bin). A substance existing in the corpuscles of 
 the blood, and to which their red color is due. 
 
 Hepatic (he-pat'-ik). Pertaining or belonging to the liver. 
 
 Hilum (hl'-lum). A small pit, scar, or opening in an organic structure ; 
 the notch on the internal or concave border of the kidney. 
 
 Humerus (hu'-me-rus) . The bone of the upper arm. 
 
 Humor (/m'-mor). Any liquid, or semi-liquid, part of the body. 
 
 Hyoid (hl'-oid}. Having the form of the letter U. The hyoid bone 
 situated between the root of the tongue and the larynx, supporting 
 the tongue and giving attachment to its muscles. 
 
 Hypo-glossal (hi-po-glos'-al}. Under the tongue. 
 
 Iliac (il'-i-ak}. Pertaining to the ilium, or region of the flanks, as iliac 
 artery, vein, etc. 
 
 Incisor (m-sz'-sor). The chisel-shaped front teeth. 
 
 Inhibition (in-hi-bish'-un}. The act of checking, restraining, or sup- 
 pressing ; any influence that controls, retards, or restrains. Inhib- 
 itory nerves and centers are those intermediating a modification, 
 stoppage, or suppression of a motor or secretory act already in 
 progress. 
 
 18 PHY 
 
266 Glossary. 
 
 Innominate (i-nom'-i-nae). Nameless ; a term applied to several parts 
 of the body to which no other definite name has been given, as the 
 innominate bone, artery, vein, etc. 
 
 Invertin (in'-ver-tin'). A ferment found in the intestinal juice, and also 
 produced by several species of plants ; it converts cane-sugar in 
 solution into invert sugar. 
 
 Jugular (jo'-gu-lar}. Pertaining to the throat, as the jugular vein. 
 
 Katabolism (ka-tab'-d-lizm^. Analytic or destructive metabolism ; a 
 physiologic disintegration ; opposed to anabolism. 
 
 Lacrymal (lak'-ri-mal^. Having relation to the organs of the secretion, 
 transfer, or excretion of tears. 
 
 Lacuna (la-ku'-na). A little hollow space ; especially the microscopic 
 cavities in bone occupied by the bone corpuscles, and communicat- 
 ing with one another and with the haversian canals and the sur- 
 faces of the bone through the canaliculi. 
 
 Lamella (/a-mer-a), pi. lamellae. A thin lamina, scale, or plate ; of 
 bone, the concentric rings surrounding the haversian canals. 
 
 Larynx (lar'-ingks}. The upper part of the air passage between the 
 trachea and the base of the tongue ; the voice-box. 
 
 Legumin (le-gu'-miri). A proteid compound in the seeds of many plants 
 belonging to the natural order Leguminosae (peas, beans, lentils, 
 etc.). 
 
 Lumbar (lum'-bar*), pertaining to the loins, especially to the region 
 about the loins. 
 
 Lymphatic (lim-fat'-ik'). Pertaining to lymph. 
 
 Lymphatics (lim-fat'-iks^. The tubes that convey lymph. 
 
 Lymphatic glands. The glands intercalated in the pathway of the 
 lymphatic tubes, through which lymph is filtered. 
 
 Massage (ma-sazh'}. A method of effecting changes in the local and 
 general nutrition, action and other functions of the body, by rub- 
 bing, kneading, and other manipulation of the superficial parts of 
 the body by the hand or an instrument. 
 
 Masseter (mas'-e-ter^). A chewing-muscle felt on the angle of the 
 jaw. 
 
 Medullary (mecT-w-Ja-n). Pertaining to the medulla, or marrow ; re- 
 sembling marrow. Also pertaining to the white substance of the 
 brain contained within the cortical envelop of gray matter. 
 
 Mesenteric (mez-en-ter'-ik). Pertaining to the mesentery, as artery, 
 vein, etc. 
 
Glossary. 267 
 
 Mesentery (mez'-en-fer-t). A fold of the peritoneum that connects cer- 
 tain portions of the intestine with the dorsal abdominal wall. 
 
 Metabolism (me-tab'-d-lizm). A change in the intimate condition of 
 cells ; (1) constructive or synthetic metabolism is called Anabo- 
 lism ; in anabolism, the substance is becoming more complex and 
 is accumulating force ; (2) destructive or analytic metabolism is 
 called Katabolism ; in katabolism there is disintegration, the mate- 
 rial is becoming less complex, and there is loss or expenditure of 
 force. 
 
 Metacarpus (met-a-kar'-pus). The bones of the palm of the hand. 
 
 Metatarsus (met-a-tar'-sus}. The five bones of the arch of the foot, 
 situated between the tarsus and the phalanges. 
 
 Mitral (mi'-tral}. Resembling a miter; mitral valve, with two flaps, 
 between the left auricle and the left ventricle. 
 
 Molar (mo'-Jar). Mill; the grinding-teeth. 
 
 Mucous (mu'-kus). A term applied to those tissues that secrete mucus. 
 
 Mucus (mu'-kus}. A viscid liquid secretion of mucous membranes, 
 composed essentially of mucin, holding in suspension desquamated 
 epithelial cells, etc. 
 
 Myosin (rai'-o-sm). A proteid of the globulin class, the chief proteid 
 of muscle. Its coagulation after death causes rigor mortis. 
 
 Narcosis (nar-fco'-sis). The deadening of pain, or production of incom- 
 plete or complete anesthesia by the use of narcotic agents, such as 
 anesthetics, opium, and other drugs. 
 
 Narcotic (nar-kot'-ic}. A drug that produces narcosis. 
 
 Neural (nu'-ral). Pertaining to the nerves. 
 
 Neuroglia (nu-rog'-li-a). The reticulated framework or skeleton-work 
 of the substance of the brain and spinal cord. The term is some- 
 times abbreviated to glia. 
 
 Nucleus (nu'-kle-us}. The essential part of a typical cell, usually round 
 in outline, and situated in the center. 
 
 Occipital (ok-sip'-i-tal}. Pertaining to the occiput or back part of the 
 head, as the occipital bone. 
 
 Odontoid (o-don'-toid). Resembling a tooth ; the tooth-like process 
 (axis) of the second cervical vertebra, on which the atlas turns. 
 
 Olfactory (ol-fak'-to-ri*). Pertaining to the sense of smell. 
 
 Osmosis (os-mo'-sis). That property by which liquids and crystalline 
 substances in solution pass through porous septa; endosmosis and 
 exosmosis. 
 
268 Glossary 
 
 Oxy-hemoglobin (ok-si-hem-d-glo'-bin\ Hemoglobin united, molecule 
 for molecule, with oxygen. It is the characteristic constituent of 
 the red corpuscles to which the scarlet color of arterial blood is 
 due. 
 
 Pancreas (pan'-kre-as'). A large racemose gland lying transversely 
 across the dorsal wall of the abdomen. It secretes a clear liquid 
 for the digestion of proteids, fats, and carbohydrates. The sweet- 
 bread of animals, vulgarly called the " belly sweet-bread " in con- 
 tra-distinction to the thymus, or true sweet-bread. 
 
 Pancreatin (pan'-kre-a-tin). The active element of the pancreatic juice. 
 
 Papilla (pa-pil'-a\ pi. papillae. Any soft, conical elevation, as papillae 
 of the dermis, tongue, etc. 
 
 Papillary (pap'-i-la-ri}. Pertaining to a papilla; papillary muscles, 
 the conic muscular columns of the heart, to which the chordae 
 tendineae are attached. 
 
 Parietal (pa-ri'-e-tal}. Pertaining to the walls, as the parietal bone. 
 
 Parotid (pa-rot' -id}. Near the ear, as the parotid salivary glands. 
 
 Patella (pa-tel'-a}. The knee-pan. 
 
 Peptone (pep'-ton}. A proteid body produced by the action of peptic 
 and pancreatic digestion. 
 
 Pericardium (per-i-kar'-di-um}. The closed membranous sac or cover- 
 ing that envelops the heart. 
 
 Periosteum (per-i-os'-te-nm}. A fibrous membrane that invests the 
 surfaces of the bones, except at the points of tendinous and liga- 
 mentary attachments, and on the articular surfaces where cartilage 
 is substituted. 
 
 Peristaltic (per-l-stal'-tik}. The peculiar movement of the intestine 
 and other tubular organs, consisting in a vermicular shortening 
 and narrowing of the tube, thus propelling the contents onward. 
 It is due to the successive contractions of the bundles of longitudi- 
 nal and circular muscular fibers. 
 
 Peritoneal (per-i-tu-ne'-al}. Pertaining to the peritoneum. 
 
 Peritoneum (per-i-to-ne'-um}. The serous membrane lining the interior 
 of the abdominal cavity, and surrounding the contained viscera. 
 The peritoneum forms a closed sac, but is rendered complex in its 
 arrangement by numerous foldings produced by its reflection -upon 
 the viscera. 
 
 Phalanges (fa-lan'-jez}, plural of phalanx (fa'-lanyks'). Any one of 
 the bones of the fiujrers or toes. 
 
Glossary. 269 
 
 Phary-n (far'-ingks}. The cavity back of the soft palate. It commu- 
 nicates anteriorly with the posterior nares, laterally with the eusta- 
 chian tubes, ventrally with the mouth, and posteriorly with the 
 gullet and larynx. 
 
 Plasma (plaz'-ma). The original undifferentiated substance of nascent, 
 living matter. The fluid part of the blood and lymph. 
 
 Pleura (jjZci'-ra). The serous membrane which envelops the lungs, and 
 which, being reflected back, lines the inner surface of the thorax. 
 
 Plexus (plek'-sus~). An aggregation of vessels or nerves forming an 
 intricate net-work. 
 
 Pneumogastric (nu-mo-gas'-trik). Pertaining conjointly to the lungs 
 and the stomach, or to the pneumogastric or vagus nerve. 
 
 Portal (por'-tal}. Pertaining to the porta (gate) or hilum of an organ, 
 especially of the liver, as the portal vein. 
 
 Postcaval (post-ka'-val^. Pertaining to the postcava; the postcaval 
 vein, formerly called the inferior vena cava, or vena cava ascendens. 
 
 Precaval (pre-ka'-val). Pertaining to the precava; the anterior caval 
 vein, formerly called the superior vena cava, or vena cava de- 
 scendens. 
 
 Pronation (pro-na'-shun). The turning of the palm downward. 
 
 Protoplasm (pro'-to-plazm). An albuminous substance, ordinarily re- 
 sembling the white of an egg, consisting of carbon, oxygen, nitro- 
 gen, and hydrogen in extremely complex and unstable molecular 
 combination, and capable, under proper conditions, of manifesting 
 certain vital phenomena, such as spontaneous motion, sensation, 
 assimilation, and reproduction, thus constituting the physical basis 
 of life of all plants and animals. 
 
 Ptyalin (ti'-a-lin}. An amylolytic or diastasic ferment found in saliva, 
 having the property of converting starch into dextrin and sugar. 
 
 Pulmonary (pul'-mo-na-ri}. Pertaining to the lungs. 
 
 Pylorus (pl-lo'-rus). The opening of the stomach into the duodenum. 
 
 Radius (ra'-di-us). The outer of the bones of the forearm. 
 
 Renal (re' -rial}. Pertaining to the kidneys. 
 
 Rennin (ren'-in). An enzyme, or ferment, to whose action is due the 
 curdling or clotting of milk produced upon the addition of ren- 
 net. 
 
 Retina (ret'-i-na). The chief and essential peripheral organ of vision; 
 the third or internal coat or membrane of the eye, made up of the 
 end organs or expansion of the optic nerve within the globe. 
 
270 Glossary. 
 
 Sacrum (sd'-fcrwm). A curved triangular bone, composed of five con- 
 solidated vertebrae, wedged between the two iliac (pelvic) bones, 
 
 and forming the dorsal boundary of the pelvis. 
 Scapula (skap'-u-la). The shoulder-blade. 
 Sciatic (si-at'-ik}. Pertaining to the ischium; the sciatic nerve, the 
 
 main nerve of the thigh. 
 Sclerotic (skle-rot'-ik}. Hard, indurated; pertaining to the outer coat 
 
 of the eye. 
 Semilunar (sem-i-lu'-nar}. Kesembling a half-moon in shape; semilu- 
 
 nar valves, pocket-like valves at the beginning of the aorta and 
 
 pulmonary artery. 
 Serous (se'-rws). Pertaining to, characterized by, or having the nature 
 
 of, serum. 
 Serum (se'-rwm). The yellowish fluid separating from the blood after 
 
 the coagulation of the fibrin. 
 
 Solar plexus (so'-lar). Solar, with radiations resembling the sun. 
 Sphincter (sfingk'-ter} . A muscle surrounding and closing an orifice. 
 Splenic (splen'-ik*). Pertaining to the spleen. 
 Steapsin (step'-sin). A diastasic ferment which causes fats to combine 
 
 with an additional molecule of water and then split into glycerine 
 
 and their corresponding acids. 
 Sternum (ster'-num\ The breast-bone. 
 Subclavian (sub-kla'-vi-an'). Situated under the collar-bone ; subcla- 
 
 vian artery and vein. 
 Sublingual (sub-ling'-gwal). Lying beneath the tongue, as sublingual 
 
 gland. 
 Submaxillary (sub-mak'-si-la-ri). Lying beneath the lower maxilla, as 
 
 submaxillary salivary gland. 
 
 Supination (su-pi-na'-shun*). The turning of the palm upward. 
 Synovia (si-no' -vi-a). The lubricating liquid secreted by the synovial 
 
 membranes in the joints. 
 
 Tarsus (ar'-sws). The instep, consisting of seven bones. 
 Temporal (tem'-po-ral). Pertaining to the temples, as temporal artery, 
 
 vein, muscle, etc. 
 Tetanus (tet'-a-nus*). A spasmodic and continuous contraction of the 
 
 muscles, causing rigidity of the parts to which they are attached. 
 Thein (the'-in}. An alkaloid found in tea. 
 
 Theobromin (the-d-bro'-min~). A feeble alkaloid obtained from cacao- 
 butter ; the essential substance found in cocoa and chocolate. 
 
Glossary. 271 
 
 Thyroid (Mi'-roid). Shield-shaped, as the thyroid cartilage of the 
 larynx. 
 
 Tibia (tib'-i-a). The larger (inner) of the two hones of the leg, com- 
 monly called the shinbone. 
 
 Trachea (tra-ke'-a or tra'-ke-a). The windpipe. 
 
 Triceps (tri'-seps*). Triceps of the arm, the extensor of the arm, lying 
 along the back of the humerus. 
 
 Tricuspid (trl-kus'-pid) . Having three cusps or points, as thetricuspid 
 valve. 
 
 Trypsin (trip' -sin}. The proteolytic ferment of pancreatic juice. 
 
 Ulna (MJ'-na). The larger (inner) of the two bones of the forearm. 
 
 Ureter (u-re'-ter^). The tube conveying the urine from the pelvis of the 
 kidney to the bladder. 
 
 Vaso-constrictor (vas'-o-kon-strik'-tor). Causing a constriction of the 
 blood-vessels. 
 
 Vaso-dilator (vcis'-d-di-la'-tor}. Pertaining to the positive dilating mo- 
 tility of the non-striated muscles of the vascular system. 
 
 Vaso-motor (vas-d-mo'-tor). Serving to regulate the tension of the 
 blood-vessels, as vaso-motor nerves ; including vaso-dilator and 
 vaso-constrictor mechanisms. 
 
 Ventricle (ven'-tri-kl}. Applied to certain structures having a bellied 
 appearance. The cavities of the heart from which the blood is 
 forced out through the arteries. 
 
 Vesicle (ves'-i-kl~). A small, membranous, bladder-like formation, as 
 air vesicle. 
 
 Villus (fliT-us), pi. villi. One of the numerous minute vascular projec- 
 tions from the mucous membrane lining the small intestine, for ab- 
 sorbing digested food. 
 
 Vitreous (nT-re-ws). Glass-like, as the clear, jelly-like, vitreous humor 
 of the eye. 
 
INDEX. 
 
 Absorption, 172-180. 
 Accidents, 240-249. 
 Accommodation, 218, 225. 
 
 Muscle of, 225, 226, 227. 
 Adam's apple, 237. 
 Adenoids, 95. 
 Air, composition of, 97. 
 
 Effects of rebreathing, 103. 
 
 Washed by rain, 114. 
 
 Washed by snow, 114. 
 Albinos, 125. 
 Albumen, 145. 
 Albuminuria, 187. 
 Alcohol, action in blood, 255. 
 
 Cause of crime, 256. 
 
 Cause of death, 256. 
 
 Cause of railroad accidents, 256. 
 
 Compared with tobacco, 257. 
 
 Effect of continued use, 254. 
 
 And employers, 256. 
 
 And exhaustion, 256. 
 
 A narcotic, 253, 256. 
 
 A stimulant, 253, 254. 
 
 Temporary effect of, 256. 
 Alcoholic liquors, 254, 255, 256. 
 
 And athletics, 255. 
 
 Continuous use of, 255. 
 
 And criminals, 256. 
 
 Dangerous for the young, 255. 
 Amylopsin, 166. 
 Anatomy, defined, 2. 
 Anti-toxin, 120. 
 Anvil, 235. 
 Aorta, 52, 176. 
 Apoplexy, 206. 
 
 Appendix, vermiform, 168, 169. 
 Aqueous humor, 218. 
 Arteries, action of, 57-59. 
 
 Blood flow in, 64, 65. 
 
 Structure of, 58, 59, 62. 
 Artificial respiration, 243, 244, 
 Asiatic cholera, 116. 
 Assimilation, 185. 
 Astigmatism, 229. 
 Atlas, 10. 
 Auricle, 48-57. 
 Axis, 10. 
 
 Bacilli, kinds of, 117. 
 Bacteria, 118. 
 Baking, 144. 
 Barley, 138. 
 Baseball, 194. 
 Bathing, 195-197. 
 
 The sick, 248. 
 Bee stings, 247. 
 Beef tea, 144. 
 Beer, 254, 255, 259. 
 Bicycling, 195. 
 Bile, 164. 
 Bites of cats and dogs, 247. 
 
 Of snakes, 247. 
 Bitters, 259. 
 
 Black-and-blue spots, 77. 
 Bleeding, from arm, 240. 
 
 From arteries, 240. 
 
 From lungs, 241. 
 
 From neck, 240. 
 
 From nose, 241. 
 
 From stomach, 241. 
 
 273 
 
Index. 
 
 From thigh, 240. 
 
 From veins, 240. 
 Blind spot, 219. 
 Blister, 125. 
 Blood, 74-77- 
 
 Amount of, 77. 
 
 Poisoning, 116. 
 Blushing, 69. 
 Boats upsetting, 245. 
 Body and candle, 97, 98. 
 
 And locomotive, 102, 103. 
 
 And stove, 102. 
 Boiling, 144. 
 Boiling water, 141. 
 Bones, 5-14. 
 
 Broken, 14, 34, 242. 
 
 Composition of, 12, 13. 
 
 In ear, 235. 
 
 Structure of, 12, 31. 
 Boxing, 194. 
 Brain, 36, 37, 198-206. 
 
 Blood supply of, 206. 
 
 Functions located, 203. 
 
 Rest, 205. 
 
 Work, 205. 
 Broiling, 144. 
 Bronchus, 86. 
 Burns, 241. 
 
 Candle, oxidation of, 97, 98. 
 
 Capillaries, blood flow in, 60, 61. 
 
 Carbohydrates, 137. 
 
 Carbon dioxid, 97, 103. 
 
 Carpets, 118. 
 
 Carpet sweepers, patent, 119. 
 
 Cartilage, 10, 32, 90, .91. 
 
 Cecum, 168. 
 
 Cellars, ventilation of, 112. 
 
 Cells, 3. 
 
 Of blood, 74. 
 
 Of brain, 201. 
 
 Of epidermis, 61. 
 
 Of ganglions, 41, 42. 
 
 Of glands, 153. 
 
 Of lymph, 78. 
 
 Of muscle, 19, 20. 
 Cellulose, 144. 
 Cerebellum, 198, 199, 200. 
 
 Function of, 204. 
 Cerebrospinal nervous system, 37. 
 Cerebrum, 198. 
 Cesspools, 140, 141. 
 Cheese, 136. 
 Chocolate, 259. 
 Choking, 92. 
 Choroid coat of eye, 217. 
 Chyle, 174, 175. 
 
 Receptacle of, 78. 
 Chyme, 161. 
 
 Cigarette smoking, 256, 257. 
 Ciliary muscle, 225. 
 Ciliums, 85. 
 Circulation and clothing, 72. 
 
 Control of, 67. 
 
 In frog's web, 60, 61. 
 Clot, 80, 81. 
 
 Coagulation of blood, 76, 77. 
 Coccyx, 10. 
 Cochlea, 235, 236. 
 Cocoa, 259. 
 Coffee, 253, 255, 259. 
 Colds and deafness, 237. 
 
 Taking, 195. 
 Colon, 167, 1 68. 
 Color blindness, 221. 
 Color of eyes, 215, 217. 
 Congestion, 72. 
 Conjunctiva, 215. 
 Connective tissue, 20. 
 Consciousness, 201. 
 Consumption, 116. 
 Contagious diseases, 119. 
 Convolutions of brain, 198. 
 Convulsions, 26. 
 Cooking, 144. 
 Cords, vocal, 237, 238. 
 Corn, 138. 
 Cornea, 215, 217. 
 
Index. 
 
 275 
 
 Corpuscles of blood, 74, 75. 
 
 Lymph, 77-81, 82. 
 Coughing, 92. 
 Cowpox, 250, 251. 
 Cramp, 44. 
 Crazy bone, 213. 
 Crossing of nerve fibers, 202. 
 Crystalline lens, 218, 224, 225, 226. 
 Cutaneous sensations, 211. 
 
 Dandruff, 125. 
 
 Deafness and colds, 237. 
 
 Defects of eyesight, 223-230. 
 
 Dennis, 126. 
 
 Desserts, 182. 
 
 Diabetes, 187. 
 
 Diaphragm, 83, 86, 87, 89, 176. 
 
 Diet, mixed, necessity of, 142. 
 
 Proper, 143. 
 Diffusion of gases, 106. 
 Digestion and circulation, 181. 
 
 In the intestine, 164. 
 
 In the mouth, 146. 
 
 And muscular work, 181. 
 
 And repose, 182. 
 
 In the stomach, 156-161. 
 
 And study, 181. 
 Digestive tube, 146. 
 Diphtheria, 116. 
 Disease germs, 116, 252. 
 Dislocations, 14. 
 Dropsy, 81. 
 
 Drowning, treatment for, 242-245. 
 Drunkards, 255. 
 Drunkenness, 256. 
 Duodenum, 168. 
 Dura mater, 198. 
 Dust, 114-119. 
 
 Ear, 235-237. 
 
 Eating, intemperance in, 183. 
 
 Time of, 183. 
 Eddy, body like, 187. 
 Eggs, 136. 
 
 Emulsion, 136, 1 66. 
 Energy from food, 188. 
 
 Potential, 91. 
 Entire wheat flour, 137. 
 Epidermis, 124, 125. 
 Epiglottis, 156, 157. 
 Equilibrium sense, 236. 
 Erysipelas, 116. 
 Eustachian tube, 235, 236. 
 Excretion, 123-132, 169. 
 Exercise and blood flow, 70, 101. 
 
 Forms of, 193. 
 
 For general health, 192-195. 
 
 And respiration, 101. 
 Extensors and flexors, 21. 
 Eye, 215-221. 
 Eyes, care of, 230-232. 
 Eyesight, defects of, 223-230. 
 
 Fainting, 206, 241. 
 
 Fans, no. 
 
 Far sight, 226-228. 
 
 Fat, as tissue, 184. 
 
 Fatigue, 205. 
 
 Fats, absorption of, 174, 178. 
 
 As food, 137. 
 Fermenting, 115. 
 Fibrin, 76. 
 Fish, 135. 
 Flavors, 234. 
 
 Flexors and extensors, 21. 
 P'ocus, 223. 
 
 Natural, 225. 
 Food, 134-145- 
 
 Amount needed, 183. 
 
 And foodstuffs, 134, 135. 
 
 Need of, 134. 
 
 Object of, 146. 
 
 Preservation of, 121. 
 
 For the sick, 248. 
 Football, 194. 
 Foot-bath, hot, 73. 
 Foul-air shafts, 1 10. 
 Freckles, 125. 
 
276 
 
 Index. 
 
 Fruit, 139. 
 Frying, 145. 
 Function, defined, 2. 
 Furnace, no. 
 
 Ganglions, 67, 68, 201. 
 Glands, 169, 170. 
 
 And blood supply, 128. 
 
 Control of, 128, 169. 
 
 Gastric, 159, 160. 
 
 Intestinal, 167, 173. 
 
 Lacrymal, 215. 
 
 Lymphatic, 78, 79. 
 
 Mucous, 154. 
 
 Oil, 124, 126. 
 
 Plan of, 153. 
 
 Salivary, 152-154, 165. 
 
 Sweat, 124, 127. 
 Glasses, 223, 227, 228, 229. 
 Graham flour, 138. 
 Grates, 107, in. 
 Gravity and circulation, 71, 72. 
 Grippe, 116. 
 Gullet, 147, 156, 157, 158. 
 
 Hair, 124, 126. 
 
 Hammer, 235. 
 
 Heart, 47-49. 
 
 Heart -beat, control of, 70, 71. 
 
 Rate of, 47, 70. 
 Heart-burn, 162. 
 Heat, conduction of, 129. 
 
 Convection of, 129. 
 
 Distribution of, 130. 
 
 And exercise, 130. 
 
 In the liver, 102. 
 
 Production of, 100. 
 
 Radiation of, 129. 
 
 Source of, 102. 
 Heating, direct, no. 
 
 By hot water, no. 
 
 Indirect, 1 10. 
 
 By steam, 1 10. 
 Hemoglobin, 76, 99. 
 Hemorrhage, of lungs, 241. 
 
 Of stomach, 241. 
 Hiccuping, 92. 
 Humor, aqueous, 218. 
 
 Vitreous, 218. 
 Hunger, 210. 
 Hygiene, defined, 2. 
 Hypermetropic eye, 227. 
 Hypodermic injections, 82, 
 
 Image, on retina, 218. 
 
 Inflammation, 72. 
 
 Inoculation, 250. 
 
 Intestine, large, 148, 167, 168, 179. 
 
 Small, 147, 164, 1 68. 
 Iris, 215, 217. 
 
 Jenner, Edward, 250. 
 
 Joints, 13. 
 
 Juice, gastric, 159, 160. 
 
 Intestinal, 167. 
 
 Pancreatic, 166. 
 
 Kidneys, 131, 132, 187. 
 
 Labor, division of, 3. 
 Lacrymal secretion, 215. 
 Lacteals, 173, 174, 177. 
 Larynx, 237, 238. 
 Lens, crystalline, 224. 
 Levers, 30, 31. 
 Liver, 147, 164, 176-178. 
 Lockjaw, 44, 116, 251, 252. 
 Lungs, 83-88. 
 
 Capacity of, 94. 
 
 Diseases of, 1 19. 
 Lymph, 77-81. 
 
 Capillaries, 77. 
 
 Cavities, 81. 
 
 Spaces, 77. 
 
 Tubes, 77. 
 
 Veins, 175. 
 
 Lymphatic glands, 78, 79, 175. 
 Lymphatics, 78, 174, 175. 
 
 Mad dog bite, 247. 
 Malaria, 116, 121. 
 Mastication, 148, 154, 182. 
 
Index. 
 
 277 
 
 Measles, 116. 
 Meat, 135. 
 
 Cooking, 144. 
 Meningitis, 206. 
 Mesentery, 148. 
 Milk, 136. 
 
 Sterilizing, 121. 
 Molds, 115. 
 Morphine (or Morphia), 253, 254, 
 
 258. 
 Motion, 1 6, 36. 
 
 Production of, 100. 
 Mouth, 147, 148. 
 
 Breathing through, 95. 
 Mucous membrane, 85. 
 Mucus, 85, 154. 
 Mumps, ii 6, 154. 
 Muscle fiber, of heart, 19. 
 
 Involuntary, 19. 
 
 Plain, 19, 58, 59. 
 
 Striated, 19. 
 
 Voluntary, 19. 
 Muscles, 16-26. 
 
 Action of, 17. 
 
 And bones, 28. 
 
 Skeletal, 28. 
 
 Sphincter, 161. 
 
 Structure of, 18, 19. 
 Muscular sense, 209. 
 Mustard, an emetic, 246. 
 
 Plaster, 72. 
 Myopic eye, 227. 
 
 Nails, 127. 
 Narcotics, 253-259. 
 Nasal passages, 95, 156, 157. 
 Near sight, 228-229. 
 
 In children, 228. 
 Nerve currents, 208. 
 Nerve endings in skin, 211. 
 Nerves, auditory, 200. 
 
 Cranial, 199-202. 
 
 Facial, 200. 
 
 Fibers, 39. 
 
 Function of, 39. 
 
 Glosso-pharyngeal, 200. 
 
 Hypo-glossal, 201. 
 
 Olfactory, 199. 
 
 Optic, 199. 
 
 Roots of, 38, 40. 
 
 Sciatic, 1 8, 37, 43. 
 
 Spinal, 38. 
 
 Structure of, 39. 
 
 Sympathetic, 67, 68. 
 
 Of taste, 233. 
 
 Of tongue, 233. 
 
 Trigeminal, 199. 
 
 Vagus, 71, 200. 
 Nitrogen, 97, 135, 143. 
 Nucleus, 3, 19, 61. 
 
 Oats, 138. 
 
 Opium, 253, 254, 255, 258. 
 Organ, defined, 2. 
 Oxidation in the body, 102. 
 Oxygen, 97, 98, 99. 
 Oxy-hemoglobin, 99. 
 
 Pain, 209, 210. 
 
 Palate, 156, 157. 
 
 Pallor, 69. 
 
 Pancreas, 147, 165, 166. 
 
 Pancreatic juice, 166. 
 
 Papillas, of skin, 125, 126. 
 
 Of tongue, 233. 
 Paralysis, 202. 
 Patent medicine, 259. 
 Pepsin, 160. 
 
 Peptones, 160, 162, 174, 178. 
 Pericardial fluid, 48. 
 Pericardium, 48. 
 Peristaltic action, 161. 
 Perspiration, 123, 124. 
 Pharynx, 156. 
 Physiology defined, 2. 
 Pia mater, 198. 
 Pigment, in skin, 125. 
 Plants, source of food, 190. 
 
278 
 
 Index. 
 
 Plasma, 74, 75. 
 Pleura, 86. 
 Pleurisy, 86. 
 Pneumonia, 87, 257. 
 Poison ivy, 247. 
 Poisons and antidotes, 246. 
 Pollen, 115. 
 
 Portal circulation, 175, 176. 
 Vein, 165, 175, 176, 177. 
 Potatoes, 139. 
 Potential energy, 91. 
 Presbyopia, 226. 
 Pressure sense, 212. 
 Proteids, 135. 
 Protoplasm, 3. 
 Ptyalin, 154. 
 Puff balls, 115. 
 Pulse, 47. 
 
 Pupil of eye, 215, 217. 
 Putrefaction, 121. 
 Pylorus, 159, 161. 
 
 Rectum, 167, 168. 
 
 Reflex action, 41-43. 
 
 Rennet, 161. 
 
 Rennin, 161. 
 
 Respiration, artificial, 242-245. 
 
 Control of, 95. 
 
 Forced, 92. 
 
 Movements of, 89-91. 
 
 Organs of, 83. 
 
 Rate of, 92. 
 Retina, 216, 217, 218. 
 Rice, 138. 
 Rickets, 14. 
 Roasting, 144. 
 Roots of nerves, 38, 40. 
 Running, 33. 
 Rye, 138. 
 
 Sacrum, 10. 
 Saliva, 152-154. 
 Salt, 142. 
 Scarlatina, 116. 
 
 Sclerotic coat, 215, 216, 225. 
 Scrofula, 79, 251. 
 Scurvy, 139. 
 Secretion, 169. 
 
 Lacrymal, 215. 
 Semicircular canals, 235, 236. 
 Sensations, cutaneous, 211. 
 
 General, 208. 
 
 Special, 208. 
 Sense of equilibrium, 236. 
 
 Muscular, 209. 
 
 Of pressure, 212. 
 
 Of temperature, 213. 
 Serous cavities, 81. 
 Serum, 76, 77. 
 Sick, care of, 247-249. 
 Sight, sense of, 215-221. 
 Skin, absorption by, 131. 
 
 Color of, 125. 
 
 Grafting, 131. 
 
 Nerve endings in, 211. 
 
 Protection by, 131. 
 
 Structure of, 124. 
 Sleeplessness, 205. 
 Slippers, 1 1 2. 
 Smallpox, 1 1 6, 250, 251. 
 Smell, 234. 
 Snake bites, 247. 
 Sneezing, 92, 249. 
 Sniffing, 234. 
 Solar plexus, 68. 
 Sound, 236. 
 Soup making, 144. 
 
 Value of, 181. 
 Spinal bulb, 198, 205. 
 
 Cord, 38, 40, 41. 
 
 Nerves, 38. 
 Spleen, 82. 
 Sprains, 14. 
 Standing, 32. 
 Starch, 137. 
 Sterilizing milk, 121. 
 
 Surgical instruments, I2O. 
 Stimulants, 253-259. 
 
Index. 
 
 279 
 
 Stirrup, 235. 
 
 Stomach, 147, 158-162, 165, 168. 
 
 Stoves, 108, 109. 
 
 Suffocation in wells, 245. 
 
 Sugar, 137, 174. 
 
 Sunstroke, 242. 
 
 Swallowing, 157, 158. 
 
 Sweat, 123. 
 
 Amount of, 128. 
 
 Composition of, 127. 
 
 Evaporation of, 129. 
 Sweeping, 118, 119. 
 Swimming, 245. 
 Sympathetic nervous system, 67, 68. 
 
 Tartar, 152. 
 Taste, 233, 234. 
 Tea, 253, 255, 259. 
 Tear gland, 215. 
 Teeth, 149-152. 
 Temperature of body, 101. 
 
 Regulation of, 128. 
 
 Sense, 213. 
 Tennis, 194. 
 Tetanus, 44, 251. 
 Thirst, 210. 
 
 Thoracic duct, 78, 175. 
 Tissues, denned, 2. 
 Tobacco, 257. 
 Tongue, 148. 
 Touch, 211-213. 
 Trachea, 83. 
 Trypsin, 166. 
 Tuberculosis, 117, 251. 
 Tympanic membrane, 235. 
 Typhoid fever, 116, 148, 257. 
 
 Urea, 132. 
 Urine, 131, 132. 
 
 Vaccination, 250-252. 
 Vaccine virus, 250, 252. 
 Vaccinia, 250, 251. 
 Valves of heart, 49, 50, 55, 57. 
 
 In lymph tubes, 78. 
 
 In veins, 62, 63. 
 
 In villuses, 173, 174. 
 Vegetables, 139. 
 Vegetarians, 143. 
 Veins, 60-65. 
 
 Hepatic, 176, 178. 
 
 Iliac, 53. 
 
 Jugular, 53, 80. 
 
 Portal, 175-177. 
 
 Post-caval, 51, 52, 53, 54, 80. 
 
 Pre-caval, 52, 53, 54, 80. 
 
 Renal, 53. 
 
 Sub-clavian, 52, 53, 80, 175. 
 Ventilation, 106, 108, 112, 113. 
 Ventricle, 54, 55, 56, 57. 
 Vertebra, 5-11. 
 Vesicles of lungs, 85. 
 Villuses, 173, 174. 
 Vitreous humor, 218. 
 Vocal cords, 237, 238. 
 Voice, 237-239. 
 Volition, 201. 
 
 Walking, 33. 
 
 Waste matter, source of, 123. 
 
 Water, 139. 
 
 Drinking, 142. 
 
 Ice, 141. 
 
 Impurities in, 140. 
 
 Rain, 139. 
 
 Well, 140. 
 Wheat, 137. 
 
 Flour, 137. 
 
 Whisky, 255, 256, 259. 
 Whooping-cough, 116. 
 Wind, 107. 
 Windows, in. 
 Wine, 254, 255, 256, 259. 
 Wounds, 240, 247. 
 
 X-rays, 28, 29. 
 
 yeast, 115. 
 
 Yellow fever, 116, 121. 
 
W55976 
 
 C 4? 
 
 J -A 
 
 THE UNIVERSITY OF CALIFORNIA LIBRARY