A layman's handbook of medicine : with special reference to social workers

Front matter

A LAYMAN'S HANDBOO OF MEDICINE

RICHARD C. CABOT

Eoofta by HicfmrS C. Cabot

Preface

To boil medicine down to the essentials needed by the general public and yet to avoid making it tasteless is my attempt in this book. It is too long; but I could not make it shorter without also making it duller.

Xot everything in it is practical," for one of the public's needs as I see them, is to get a glimpse of some amazingly interesting aspects of medicine which have little or no practical value. The pages on comparative anatomy, the tragic facts of anaphyi and some other passages were written out with this

lief.

"A little knowlecrs is a dangerous thir.r Yes tainly is But since every body and soul in the civilized world has now been thoroughly exposed to this dangerous contagion, I know no way to reduce the risk of disaster except by injecting into all who will submit a larger dose of knowledge in the is as: irritating form procurable. Gradually I hope an immunity to its iangefs may thus re produced.

Part of the book was given during 1915 and 1916 in the form of lectures to a group of social works: s ; their needs have guided my selection of subject matter because, as I sec it they ires: represent the gen-

PREFACE

eral public. For the same reason their questions and

the answers given to them have been made part of

the book.

The illustrations are rough and sketchy but, I hope,

worth their space. I here thank Messrs. D. Appleton

& Co. for the use of the cuts used in Figs. I and 2

and W. B. Saunders Co. for a diagram of the ear.

Richard C. Cabot

1 Marlboro St., Boston November, 19 16.

CHAPTER I Introduction I

The Skeleton 2

The Muscles 12

Contents of the Chest and Abdomen 13

The Heart and Lungs 15

Respiration 18

The Digestive Tract 27

The Liver 34

The Urinary Organs 36

The Genital Organs 38

The Nervous System 45

CHAPTER II Diseases of the Tonsils

Tonsillitis ..-."« 48

Quinsy sore throat 50

Hypertrophied tonsils and adenoids in children . . . .51

Diseases of the Nasal Cavities, Catarrh 53

Laryngitis 55

Diseases of the Lungs:

Tuberculosis 57

Bronchitis 57

Bronchiectasis 59

Coughs 59

Asthma 61

'Emphysema 62

Empyema 63

Pleurisy 63

Pneumonia 66

CHAPTER III Diseases of the Heart 67

Rheumatic heart disease (endocarditis) f .68

vii

Syphilitic heart disease 70

Arteriosclerotic heart disease 70

Nephritic heart disease 72

Diseases of the Arteries:

Arteriosclerosis 76

Aneurism 79

Varicose Veins (Varicose Ulcer) 80

CHAPTER IV DISEASES OF THE GASTROINTESTINAL TRACT The Mouth

Diseases of the teeth :

Riggs' Disease 84

Caries 86

Impacted teeth 88

Hutchinsonian teeth 90

Diseases of the tongue (cancer, tuberculosis, syphilis) ... 92

Diseases of the throat 92

Diseases of the esophagus:

Cancer 93

Corrosive stricture 94

Spasmodic stricture 94

Diseases of the stomach:

Cancer 95

Ulcer 97

Gastritis 101

Stomach symptoms caused by

Nervousness 103

Diseases of the brain 105

lungs 107

heart 108

liver 108

intestine 109

kidney 109

Industrial diseases, and 109

Diseases of the blood no

CHAPTER V Diet in

Three classes of foods 112

Indigestible foods 114

Quantity of food 117

Selective action of the stomach 119

Calory value of foods 121

Adulteration of food . 125

viii

Scurvy, beri-beri, and vitamins 126

Exercise after food 128

Diet and constipation 128

Constipation:

Intestinal effects of emotion 132

Habit formation 133

Laxatives and purgatives 134

Effects of constipation 136

CHAPTER VI DISEASES OF THE LIVER AND INTESTINE Gall-stones (jaundice) 137

Cirrhosis 145

Abscess of the Liver 147

Hydatid 147

Catarrhal jaundice 148

Appendicitis 149

Inflammation of the intestine (colitis, enteritis, dysentery,

nervous diarrhea) 153

Tuberculosis 157

Intestinal obstruction 157

Chapter VII Diseases Of The Kidney And Bladder

Bright's disease, acute and chronic (apoplexy) 161

Floating kidney 172

Tuberculosis of the kidney 173

Pyelitis 177

Diseases of the Bladder: I

Cystitis 178

Tumors 179

CHAPTER VIII Female

Tumor of the uterus 180

Cancer of the uterus 183

Inflammation of and through the uterus 184

Endometritis 185

Diseases of the cervix 186

Lacerations of the perineum 187

ix

Diseases of the Fallopian tube 189

Peritonitis IQ2

Cystocele and rectocele . . . 195

Prolapse of the uterus 196

Vaginitis I96

Ovarian disease:

Tumor IQ8

Prolapse 201

Extra-uterine pregnancy 201

The Hygiene of Pregnancy 203

Disturbances of menstruation 204

Abortion 205

Male:

Gonorrhea 208

Prostatic obstruction 212

Varicocele , 214

Birth Control 214

Septic Peritonitis 216

Tuberculous Peritonitis 217

CHAPTER IX Moods 218

Psychoneuroses 219

Neurasthenic 221

Hysteric 222

Psychasthenic 227

Traumatic 228

Visceral 229

Psychoses:

Manic depressive 233

Exhaustive 240

Parturient 241

CHAPTER X DISEASES OF THE NERVOUS SYSTEM (continued)

Insanities { 242

Precocious dementia 243

Syphilitic dementia ^ . 245

Senile and arteriosclerotic dementia 248

Paranoia 249

Alcoholic insanity 251

Mental Deficiencies 253

Diseases of the Brain:

Apoplexy 256

Syphilitic disease of the brain '* . 258

x

Brain tumor 258

Meningitis (tuberculous, aural, epidemic) 259

CHAPTER XI DISEASES OF THE NERVOUS SYSTEM (continued)

Diseases of the Spinal Cord:

Tabes dorsalis 265

Spastic spinal paralysis 272

Poliomyelitis 273

Diseases of the Peripheral Nerves 276

Alcoholic neuritis 277

Epilepsy . 279

Migraine 285

Chapter XII Diabetes, Diseases Of The Blood, Diseases Of The Bones And Joints

Anemia (secondary, pernicious, chlorosis) 295

Leucemia 302

Purpura 302

Hemophilia 303

Diseases of the Lymph Glands 304

Cervical adenitis (from teeth, tuberculosis, syphilis, malignant disease 305

Goitre 306

Myxedema 311

Diseases of the Bones and Joints:

Tuberculosis of the bones 312

Tuberculosis of the spine 314

Syphilis of the bones and joints 317

Rickets , 318

CHAPTER XIII DISEASES OF THE BONES AND ]OINTS^(continued)

Diseases of the Bones and Joints (continued):

Fractures 322

Arthritis ' . 324

Infectious (tuberculous, rheumatic, gonorrheal) .... 325 Hypertrophic (Heberden's nodes) 327

xi

Atrophic 329

Gouty 330

Traumatic 331

Osteomyelitis 333

Sacro-iliac strains, sprains, etc 335

Scoliosis 337

Flat foot 338

Trichiniasis 339

Animal Parasites:

Tapeworm 341

Pinworms 342

Round worm 342

Hookworm 342

Chapter XVII Industrial Diseases — Skin Diseases

Dust 437

Caisson disease 439

Diseases due to heat and cold 443

Muscular strains 443

Occupational skin diseases 444

Occupational neuroses 444

Industrial overstrain 446

Pruritus 447

Erythema 447

Macule, papule, pustule, vesicle 447

Eczema 447

Acne 449

Boils 450

Carbuncles 451

Impetigo 451

Pediculosis 452

Scabies 453

Dermatitis venenata 453

Psoriasis 453

Urticaria 454

Anaphylaxis 454

CHAPTER XVIII The Eye

Anatomy 457

Conjunctivitis 459

Interstitial keratitis 461

Phlyctenular conjunctivitis and keratitis 461

Iritis 462

Cataract 464

Retinitis 465

Neuritis 466

Squints and headaches 468

Astigmatism 468

Myopia 469

xiii

Hypermetropia 469

Glaucoma 470

Trachoma 471

The Ear:

Otitis media 472

Broken ear drum 474

Syphilitic disease of the ear 476

Inherited deafness 476

CHAPTER XIX EMERGENCIES — HOME MEDICINE — PERSONAL HYGIENE Choking 477

Control of bleeding 478

Cuts 483

Bruises 483

Sprains 484

Unconsciousness 485

Fits 485

Convulsions 486

Sunstroke 486

Heat exhaustion 488

Burns 488

Frost bites 489

Poisoning 489

Drowning 490

Bee sting 492

Home Medicine 493

Sleep 493

Food 496

Exercise 497

Bathing 498

Clothing 499

Menstruation 500

Rest, recreation, vacation 503

Chapter XX Miscellaneous Ailments, Trivial Or Severe"

Common colds 505

Vasomotor rhinitis 505

Hang-nail and paronychia 505

In-growing toe nail 506

Bursitis about the shoulder 506

Shingles . 507

xiv

Chorea and habit spasm 507

Hernia 508

Hare-lip, cleft palate, and other congenital deformities . 509

Enuresis 509

Stammering 511

Marasmus 511

Still-birth 511

Starvation 512

Obesity 512

Cancer of Lip 513

Cancer of Rectum 513

Cancer of Breast 513

Grippe ' 514

POSTSCRIPT . 515

INDEX 517

LIST OF FIGURES

i, 2. Leg Bones of Various Animals arranged to show the

Corresponding Parts 4

Reproduced by permission of D. Appleton & Company from Jordan and Kellogg's Evolution and Animal Life. Copyrighted, 1907, by D. Appleton & Company.

3. To show how the Scapula is joined by Muscles to the

Backbone 5

4. Spinal Column 6

5. Diagram to show Relation of Spinal Cord and Nerves

to Vertebral Column 8

6. Breast Bone, Backbone, and Ribs 9

7. Pelvis and Hip Joints 10

8. To show how Biceps is fastened to the Bones at each

End and how by contracting it pulls up the Forearm . 11

9. The Body Cavity divided by the Diaphragm ... 14

10. Diagrammatic Sketch of the Heart and Great Vessels . 15

11. Diagrammatic Cross-Section of an Imaginary Organ

somewhat like the spleen 1 7

12. The Front Wall of the Chest removed to show the

Position of the Heart and Lungs 18

13. Diagrammatic Sketch of the Openings of Windpipe and

Gullet 24

14. Image of the Larynx as seen in Mirror held above it . 25

15. Trachea, Bronchi, and their Branches in the Lungs . . 26

16. Bronchiole and Alveoli . . . 26

17. The Tonsils 27

18. Gullet 28

19. Contracted Empty Stomach 29

20. Distended Stomach 29

xvii

LIST OF FIGURES

21. Pancreas and Duodenum 30

22. The Course of the Large Intestine 31

23. Kidney and Urinary Collecting Tubes 37

24. Ureters 38

25. Female Genitals in Cross-Section 39

26. Female Genitals 40

27. Cross-Section of Male Genitals 43

28. Diseased Teeth and Normal Teeth 90

29. Diagram to show Connection of Gall Bladder and Pan-

creas with the Intestine 139

■30. Cross-Section of the Eye 457

31. Semidiagrammatic Section through the Right Ear . . 472

After Czermak

Chapter I Anatomy And Physiology

Any one who studies the human body soon becomes aware of two opposite and extraordinary things: first, that it is full of beauties and extremely useful contrivances, and second, that it contains a number of blunders. Any one who is bound to think that it is the work in toto of an intelligent Creator here confronts a hopeless difficulty. But any one who goes to the other extreme and thinks that it is the product of chance evolution is in another hopeless difficulty, as I see it. Hence I cannot face the fact of the body's beauty and usefulness, and also the fact of its ugliness and mistakes, without saying something on the relation of the body to God.

The relation of our bodies to God is somewhat like the relation of our souls to God. We do not expect that our souls will be perfect. Our bodies are a part of nature and need not be assumed to be perfect. Presumably bodies and souls have a certain amount of freedom whereby they can go wrong. I see the body, like a great deal of the rest of nature, heroically trying to do right, often with extraordinary success, some-

i times with pitiful failure; and I find this in no way irreconcilable with a belief in God. But I should find it impossible if I did not recognize that element of freedom to go wrong which I think is present in the whole of nature, and which I think makes nature sometimes beautiful, sometimes cruel, sometimes badly contrived, and sometimes marvellously ingenious.

Anatomy begins with the skeleton because it is the easiest part to keep and handle, but the first thing to know about the human skeleton is that it is really formed last. We have the idea of the dry bones becoming clothed with flesh; the opposite is the fact. The soft flesh gradually makes within itself a skeleton. The baby is born practically with no skeleton; some of the smaller animals never have much of any. In man the skeleton is gradually developed as it is needed.

There are two kinds of skeletons in the animal kingdom, those arranged on the outside and those fixed on the inside. We have both. The lobster has a skeleton on the outside and keeps his soft parts inside it. This type of skeleton restricts movement, but has great advantages from the point of view of protection. Our skeleton is worked out to combine the two advantages so far as possible. It is on the outside of the brain, like the lobster or tortoise skeleton, because our brain needs protection more than any other part of our body, yet does not need independent motion or flexibility. We have a skeleton of the inside type in parts of the body where bone is useful for support and the attachment of muscles. Animals that do not need to stand upright, fish for example, need very much less skeleton ; we need a great deal for purposes of support. Freeswimming animals do not need so much stiffening.

I think it is a little easier to begin with the extremities. The human arm is developed out of the fin of a fish. As we come up the animal scale through such tools as wings, paws, or legs, we have one bone of the original fin remaining next to the body; that joints on to two bones, which in turn joint on to a number of other small bones (the wrist and hand). Thus, from a fin you get an arm ; next the body, one bone, then two bones, then a lot of little bones on the end. That explains that poor arrangement of things that we call the wrist. It seems a stupid arrangement, a mere makeshift, but perhaps it is the best that the body could do in making an arm out of a fin.

The same idea is carried out in the lower extremity: one hip bone, two lower-leg bones, a lot of little bones at the ankle, and then toes. It looks as if it would be much better to have one bone instead of all this mass of little bones in the wrist and the ankle. If we have to master the arrangement of those bones, we soon find out how arbitrary and awkward it is ; but as a way of getting for ourselves an arm and hand when we had a fin to start with, it becomes on the whole very intelligent. Note, then, the similarities in the arm and leg, and that we had the same similarities in wing and claw

■mm

Fig. i. Leg bones of various animals arranged to show the corresponding parts. I. Salamander. 2. Frog. 3. Turtle. 4. Aetosaurus. 5. Plesiosaurus. 6. Ichthyosaurus. 7. Mososaurus. 8. Duck. In each leg the letter / stands for femur or thigh bone, / for tibia or shin bone, fi for fibula the other bone of the lower leg. The toes are sometimes numbered.

Fig. 1. More leg bones arranged as in Fig. 1. 9. Ornithorhynchus. 10. Kangaroo. 11. Megatherium. 12. Armadillo. 13. Mole. 14. Sea lion. 15. Gorilla. 16. Man. Note how in the kangaroo and sea lion the thigh bone (/) is abbreviated in comparison with its size in man.

and finally feet: one bone nearest the body, then two, then many ; finally, a fanlike extremity which can either be expanded into claws or fused together into a hoof, or left as fingers and toes.

The four extremities are fastened to the trunk by joints, ligaments, and muscles; the upper extremity extraordinarily loosely, the lower more tightly. The

arm bone fits into a shallow cup in the shoulder blade (the scapula). The scapula itself is attached only by muscles to the collar bone and to the chest. The whole thing is loose and free. See Fig. 3. This arrangement is of great value in giving extraordinarily free motion of the arm. We have n't anything like this motility in the leg; on the whole we do not need it. The leg is joined on much more firmly, with a ball-andsocket joint, giving greater firmness for supporting the body's weight, and much less freedom for other purposes.

The rest of the skeleton is essentially the backbone, skull, thorax, and pelvis. The backbone is made of a number of separate pieces, vertebrcet which come through the whole vertebrate kingdom from the fish up. We often find on the beach the vertebrae of fish which we can recognize at once as vertebrae. They are piled on top of each other like bricks, in a column, with cartilage binding each to each like mortar. The whole column is hollow, and down the centre of it goes a prolongation of the brain, which we call the spinal cord, through which travel all the influences of command which pass out of the brain and all the news messages which come into the brain. The branches of spinal cord get to the outer world through a series of side windows which perforate the vertebrae every inch or so. From these branches come pairs of nerves, right and left, all the way up and down from the level of the skull clear down to the pelvis. Those nerves branch and branch like trees and their tips go to every part of the body: to the face, the head, the arms, the chest, the abdomen, and the legs.

The rather bizarre arrangement of ribs — which

&&l oh. GtuJL irreverent medical students often call the " bird-cage" — is a compromise between a defence and mobility. The heart and lungs are indispensable and precious organs which must be protected as far as possible, but still must have free motility for breathing. The ribs serve these two purposes admirably. In the back the ribs are hinged on the backbone (spinal column) so that when we breathe in they rise and go upwards, and as the air goes out they go down again and the chest becomes smaller.

The scapula,, or shoulder blade, doubtless serves some purpose of protection. Otherwise it is pretty hard to see why we have it. In birds there is very much less of it, and yet the muscles, which fasten on it, are carried just as well.

The pelvic bones are thick and heavy for three purposes: first, to protect the vulnerable and precious genital organs, and the developing baby in the female; secondly, because the back and leg muscles, the largest and strongest muscles in the body, pull upon these bones; and thirdly, because through them the whole body weight is transmitted to the legs. The outlet of the pelvis, through which the baby has to pass when it is born, is between the sacrum (what corresponds to the root of the tail of our arboreal ancestors) and the

pubic bone in front.

The size and shape of that opening, as it is made right or wrong, roomy or narrow, determine the ease or difficulty of childbirth.

One of the duties of the obstetrician is to lb Gfifcin-aai^

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* 3icj^nfl£aK€dL, fygrtiffi* measure those bones before childbirth and know exactly whether there is proper room for a child to pass between.

The Muscles

Bones, aside from stiffening and support, serve the purpose of giving points of attachment to the muscles. When I wish to draw my arm up, I am able to do so because the muscle which is attached at A is also attached at B. When that muscle contracts, it draws the points A and B nearer together — the characteristic work of every muscle being to bring its two ends nearer together. Because a muscle can do that, an arm can move. Because another muscle which is hitched on the back of the upper arm and on the back of the forearm, because that muscle also contracts and pulls up the tip of the elbow, we are able to push the arm out straight. All movements that we make — such as the movements of the tongue and face, the fine movements of the hand, of the trunk and legs — are possible because the two ends of some muscle come nearer together. Because these two ends are fixed to bones at the extremity, the muscle is able to move the limb, the trunk, or the head.

We need to know very little about the muscles so far as I see. Physicians also know very little about them. They occur in two great groups, a fact that one can readily remember: a group that bend up {flexors), and a set that stretch out (extensors). In every part of the body there are these pairs of muscles opposite to each other, all of them, of course, controlled by nerves, which go up through the spinal column to the brain. Every motion starts in the brain, comes out through the spinal column and nerves to the muscles, and so to the bones. The end result of a command coming from our brain is to move a bone.1

There is also a small group of muscles called involuntary, not subject to the will, muscles which contract without our control or intention. The best examples are the muscles of the heart and the muscles of the intestine. Those are a little different microscopically from other muscles. They are not attached to bones, and they get their pull in both cases from the fact that they are circular. The heart muscles run around the heart, the intestine muscles around the intestine, and when they shorten they shorten all around the circle, as a rubber band shortens when it draws in.

Contents of the Chest and Abdomen

The cavity of the human body, when we leave out of account the extremities and the head, is an oval divided into an upper chamber and a lower chamber by the diaphragm, which is the floor of the chest cavity and the ceiling of the abdominal cavity. The diaphragm is an arched, smooth, flat muscle hardly any thicker than cardboard in parts. Like any other

1 Among the voluntary muscles there are but a few unimportant exceptions to this rule. But it does not hold for the group next described.

muscle, it can contract. It is hitched to the ribs on both sides ; to the backbone behind and to the breastbone in front. When it contracts, of course, it must draw its ends nearer together. To do that it must "descend " as we say — that is, flatten out its arch. When it flattens out, its centre goes down, like the piston of a pump, and thus sucks air into the chest through the mouth. That is the great action of breathing, far more important than anything the ribs do. Even when the rib joints are ossified and the rib rigidly fixed to the spine, the person breathes fairly well. But if the diaphragm is paralyzed, the person dies. It is, therefore, the most important muscle that we have. It divides the body, as above said, into two great cavities, the chest above and the abdomen below.

The Heart and Lungs

The lungs fill nearly all the upper body chamber except what is filled by the heart. There are no impor* tant organs in this cavity except the heart and lungs.

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All the rest of the bothersome organs are below the

diaphragm. From the heart, as Figure 10 shows, go

« two great branches, the beginning of the arterial tree, nearest the heart. From the main arterial trunks go the larger branches, and then smaller and smaller twigs, until we get down to the capillaries, of microscopic size. They honeycomb the tissues themselves, and regather on the other side to form another set of tubes, the veins; these gather into large tubes, one leading back to the heart from above and one coming from below.

It is not worth while to go into the details of circulation. In a general way it has this plan: the heart pumps in two directions at once. When it contracts, it pushes the blood out as we squeeze water out of a sponge; the blood goes out in two directions. Through one set of tubes it goes to the lungs. (The lungs are especially favored ; they have one set of tubes to themselves.) All the rest of the body — the heart, brain, liver, kidneys, stomach, intestine, arms, legs, genitals — has another set of tubes branching from one trunk (the aorta). From both of these regions the blood returns and starts again. On its way out we call it arterial blood, and the tubes we call arteries. On its way back to the heart we call it venous blood, and the tubes that carry it we call veins. In the nerves, brain, muscles, and every part and organ of the body there are extraordinarily fine tubes, the capillaries, finer than any hair, in close contact with every part of every organ. They receive from the arteries nourishment for every tissue. Downstream from the capillaries the veins carry back the venous blood containing the body waste.

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The great function of circulation is to warm and nourish the body. It carries the air and food to the organs and it carries back, away from the organs, some of their waste products.

Respiration

The lungs, the position of which we see in Figure 12, fill up all the space in the chest except that which is

Ou.<f. £uj* r taken by the heart. They fill all the chinks around the heart, which is set on the diaphragm a little to the left. To the lungs the blood is sent by the heart after returning from all the rest of the body, bearing the waste products. In the lungs that blood meets with air, the air which we draw into our lungs with each breath.

If we ask just how this meeting occurs, it is hard to answer. It is a very mysterious process, for the oxygen of the air goes into the blood right through the walls of the blood vessels. But parts of the air (what the body does not need) are left behind. It is not at all a process of filtration ; the air is not simply sucked in, but a process of intelligent selection goes on. The air contains some things which the body needs and some things that it does not need ; in the blood vessels of the lungs it meets with the blood which contains some things it does not need. Then an exchange occurs. The blood takes about twenty-three per cent of the oxygen out of the air and gives back in exchange another gas — carbon dioxide, a waste product. That is the essential process of respiration.

One of the things I think that every person should know about respiration and the lungs, is that out of all the oxygen which we draw into our lungs, we take but a small part, about twenty-three per cent ; we reject all the rest. In other words, we do not make use of all the oxygen in the air which we breathe in, because the body does not need it. The practical point is this: people are always talking about getting more oxygen into their blood. If we force more oxygen into our lungs, we do just the same thing as if we forced upon a man, who had already eaten part of a huge dinner, six more dinners. The body has already taken all it can take out of the tremendous superfluity of oxygen which comes into the lungs. It cannot take more.

Many partially educated persons think that if we take deep breaths, force more air into our lungs, we shall get more oxygen into our tissues. But we cannot. There is no sense in deep breathing for the purpose of getting more oxygen into the lungs. It has an effect upon the brain, but it has no effect upon the lungs; it does not force oxygen into the system. The effect upon the brain is very interesting: it puts the soft pedal on our thoughts. It fogs our brains which is sometimes a good thing to do. For that reason, among Oriental religious sects and other people who try to follow their lines of thought, the practice of deep breathing persists, and may be useful because of its calming effect upon the brain. Again, deep breathing has an effect upon the bowels ; I think it is of use in some cases of constipation, because deep breathing, forcing the diaphragm down, stirs up the bowels when they are logy, and helps to push their contents along.

Q. In a room with the air in motion, is there danger from a draught?

A. I imagine that people are individual in that matter. From my own observation I should say that most of us were far better for living in a draught all our lives, but that some people are harmed by it.

Q. If the air does not have to be cold, simply has to be pure and to be in motion, what is the advantage of an outdoor school?

A. Pure air means air that is not too hot and that is in motion. These conditions are easiest found outdoors.

Purity has nothing to do with CO2 or O2. Stale air may be made perfectly fresh, not by changing the oxygen, but simply by cooling and putting the air in motion. Indoors air gets hot and stagnant. Outdoors it is cooler and moves more. I am leaving out here the question of odors, which of course are easier lost outdoors than in.

Q. Why does blood go back to the heart?

A. It is pushed on from behind and sucked from in front. The system of tubes is closed. There is nowhere else it can go. Moreover, in the veins there are valves which open toward the heart and close the other way, so that any blood that gets going is held by them. Second, the veins go in among the muscles. Every time the muscles contract they squeeze the veins. The veins are so thin-walled that they contract, are thus emptied, and because of the valves they must empty toward the heart.

Q. How does it get from the arteries to the veins?

A. Through the capillaries. The capillaries are a closed system of tubes, very small, continuous from the arteries on one side to the veins on the other.

Q. I did n't understand what you said about deep breathing.

A. I said that taking deep breaths, so as to force air into the lungs, did not force any more oxygen into the blood, and did not therefore accomplish what it is supposed to accomplish. In the lungs our blood selects out of the total bulk of oxygen that comes there a small proportion, about twenty- three per cent which we use; the rest we reject. If we face a draught or try to get any more air into the lungs, we do not get any more oxygen. Fresh air, aside from its freedom from smells, means essentially two things: air that is not too hot and air that is in motion. If we get into a room where the air is stale and close, we can make that air fresh by cooling it and setting it in motion. We do not need any more oxygen nor any less carbon dioxide.