The elements of physiology and hygiene; a text-book for educational institutions

Front matter

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A

Chapter I. Page

Relations of Physiology to other Branches of Science, . 11

Sect. 1. — Nature of Scientific Knowledge, . . . .11

2. — The Preparatory Sciences, .... 13

8. — The Biological Sciences, 14

Chapter II

A General View of the Structure and Functions of the Human Body, . 19

Sect. 1. — Work and Waste, 20

2. — Outlines of the Bodily Structures, ... 23

3.— The Bodily Tissues, 26

4. — The Combination of Actions, .... 29 5. — Nutrition, Circulation, Excretion, . . . .82

CHAPTER III. The Vascular System and the Circulation, . . . . 35

Sect. 1. — The Vascular System, 35

2. — Connections and Structure of the Heart, . . 44

8. — Working of the Heart and Vessels, . . .52 4. — The General Circulation, 59

CHAPTER IV. Of the Blood and Lymph, 65

Sect. 1. — Its Microscopical Elements, .... 65

2. — Its Physical and Chemical Properties, . . .72

VIU

CHAPTER V. Of Kespiration

Sect. 1. — Arterial and Yenous Blood, . 2.— The Lungs and their Office, 3.— The Respiratory Mechanism, 4. — Inspiration and Expiration, 5. — Effects of Respiration,

CHAPTER YL

The Sources of Loss and of Gain to the Blood, Sect. 1. — Sources of Loss to the Blood, 2. — Losses and Gains by the Liver, 3. — Sources of Gain to the Blood,

CHAPTER Vn.

The Function of Alimentation, ....

Sect. 1.-— Properties of Food-Stufis, . 2. — Preliminaries of Digestion, 3. — Stomach-Digestion, 4. — Intestinal-Digestion,

CHAPTER Yin.

Motion and Locomotion,

Sect. 1. — Instruments of Motion,

2. — Mechanism of Bodily Movements, 3. — Movements of Locomotion, 4. — Yocal Movements, . .

CHAPTER IX.

Of Sensations and Sensory Organs, ....

Sect. 1. — Reflex Action — Groups of Sensations, 2.— Touch, Taste, and Smell, . 3. — The Mechanism of Hearing, . 4. — Working of the Auditory Mechanism,

CHAPTER X.

The Organ of Sight,

Sect. 1. — Structure and Action of the Retina, 2. — The Luminous Agent, . 3. — The Intermediate Apparatus, . 4 — Focal Adjustment, 5. — Appendages of the Eyeball,

PAGE

81 81 84 90 95 100

106 106 120 124

133 133 340 145

153 153 156 no

111 111

180 188 196

201 201

207 209 211 216

CONTENTS. IX

CHAPTER XL

PAGE

Sensations and Judgment, 219

Sect. 1. — Compound Sensations, 219

3. — Visual Sensations and Mental States, . . . 229

CHAPTER XII.

The Nervous System and Innervation, 236

Sect. 1.— The Spinal Cord— Reflex Action, . . . .236

2.— The Brain, 245

3. — The Cerebral Nerves, 249

4. — Unconscious Cerebration, 252

CHAPTER XIII.

Histology ; or, the Minute Structure of the Tissues, . .255

Sect. 1.— Dermal Tissues, 255

2. — Interior Tissues, 260

3.— Osseous Tissues, ...... 263

4. — Muscular and Nervous Tissues, .... 270

Part II. Chapter Xiy

Scope and Aims op Hygiene, .... . . 2'75

CHAPTER X7.

Air and Health, 282

Sect. 1. — Impurities of the Air, 282

2.— Morbid Effects of Impure Air, . . . .287

3.— Purification of the Air, 291

CHAPTER XYI.

Water and Health, 296

Sect. 1.— Physiological Office of Water, . . . . 296

2.— Different Kinds of Water, 297

3. — Morbid Eflfects of Impure Water, . . . 302

4. — Purification of Water, 806

X CONTENTS.

CHAPTER XYII.

PAGE

Food and Health, 308

Sect. 1. — The Alimentary Principles of Food, . . . 308

2.— Animal Foods, 312

3.— Vegetable Food, 315

4. — ^Auxiliary Foods, 318

6. — Culinary Preparation of Foods, . . . 324

6.— Injurious Effects of Bad Diet, .... 326

CHAPTER XVIII.

Clothing and Health, . 334

Sect. 1. — Properties of Clothing Material, . . . 334

2. — Manner of Dressing the Body, .... 337

CHAPTER XIX.

Exercise and Health, 344

Sect. 1. — Labor and Exercise, 344

2. — Effects of Regulated Exercise, . . . . 345

3. — Excessive and Insufficient Exercise, . . . 349

CHAPTER XX.

Mental Hygiene, 353

Sect. 1.— Relations of Mind and Body, .... 353

2. — Forms of Mental Impairment, .... 357 3. — Causes of Mental Impairment, . . . .375

PAET I.

ELEMENTARY PHYSIOLOGY.

Chapter I Eelations Of Physiology To Other Branches Of Science

INTRODUCTORY.

Section I. — Nature of Scientific Knowledge

1. How it Originates. — ^Physiology is one of the branches of Science, and we cannot better commence its study than by forming clear ideas of the general nature of science itself, and of the relations which this branch of it bears to its other parts. By mapping out the family of Sciences to which Physiology belongs, and upon which it depends, we may get a definite conception of its position and relations in the group : to this the present chapter will be devoted.

Man has been called the Interpreter of Nature, and Science defined as its right interpretation. But the true interpretation of Nature is a slow and difficult work. There is a curiosity in the human mind to seek explanations and understand the reasons and causes of things ; but at first its questions are put at random and answered vaguely, and knowledge is then rude and imperfect. With increasing experience questions are put more sharply and go deeper, and then come clearer explanations and a better understanding of things. In this way knowledge upou

Tnany subjects grows to be more and more perfect ; and when it becomes so accurate and sure that it is capable of being proved to persons of suitable intelligence, it is called science. The science of any subject is the highest and most exact knowledge upon that subject.

2. The Order of Nature. — That which makes science possible is the regularity of Nature's order, and it is only possible so far as that order can be traced. All the appearances and effects of Nature with which we can become acquainted are known as Phenomena ; those which exist together constitute the order of Coexistences ; those which follow each other in a regular succession form the order of Sequences. Thus all the various parts of the human body, as bones, blood-vessels, nerves, and fluids, and its simultaneous operations, as of breathing, digestion, circulation, constitute its coexistences ; while the succession of its numerous actions and effects, as for example the agreeable feeling and renewed strength which follow the taking of food, constitutes its sequences. A scientific inquiry into the order of Nature, therefore, resolves itself into an investigation of the relations of coexistence and sequence among all objects, while each science is a statement of the coexistences and sequences of some particular part of Nature. If there are any subjects which have no coexistences and no sequences ascertainable by the human mind, those subjects are incapable of becoming sciences.

3. Connection of the Sciences. — Science is thus the most perfect knowledge of Nature in all her aspects. But the parts of Nature are intimately connected in one great whole ; therefore the sciences which give an account of Nature must also be intimately connected together. They overlap and interlace in the closest manner, so as to be in a very great degree mutually dependent on each other. To understand any one of them, it is therefore important to have some knowledge of the others most nearly related to it, and upon which it essentially depends.

THE PREPAKATORY SCIENCES. 13

Section II. — The Preparatory Sciences

4. Mathematics. — The least dependent of all the sciences, and at the same time the simplest and the easiest, is that which considers the number and the forms, or shapes of objects, and this is Mathematics, or the science of quantity. We cannot think of things except as having form or outline, and the science which deals with forms and their relations is termed Geometry; nor can we think of them except as one or many — that is, as being numbered, and a knowledge of the combinations and relations of numbers constitutes the science of Arithmetic, So simple, clear, and definite are these ideas that they may actually be considered apart from the things to which they apply, so that arithmetic can deal, as it were, with pure numbers rather than with things numbered, and geometry with space rather than the objects contained in space. The ideas may be thus abstracted from the realities, hence mathematics is known as the most abstract of the sciences ; and as the ideas with which it deals are few, it has been carried to the highest perfection of any science.

As in all other sciences we have constantly to use mathematical ideas, a certain amount of elementary arithmetic and geometry is useful and important as a preparation for this kind of study.

5. Physics. — The science which comes next is that which passes to the actual study of things ; which goes from ideas of number to those of the objects numbered ; from the notion of space to that which occupies space, or which adds to mathematical conceptions those of matter and force. It considers the universal and essential properties of matter, the forces which act on it to produce motion, and the resulting laws of motion. This branch of science is called Physics or Natural Philosophy, and treats of the resistance, weights, pressures, mutual attractions, and general properties of material bodies. It is not so simple as mathematics, yet the conceptions with which it deals are so few that it has been worked out to a considerable degree of perfection.

6. Chemistry. — If there were only one kind of matter in the universe, as iron or sulphur, there could still be a science of physics. But there is a large number of elementary bodies in Nature which combine intimately together in various proportions and give rise to that infinite diversity of material substances which we see around us. These all have the general physical properties, but they have also certain special and peculiar properties which are different in different kinds of matter. The knowledge of these gives rise to the science of chemistry, which treats of substances as simple or compound, how they are constituted, and how they act upon and change each other. But a knowledge of the universal and constant properties of bodies should precede the study of the more special and variable properties ; hence physics prepares for chemistry. The ideas which pertain to chemistry are far more numerous and complex than those of physics, and accordingly chemistry is much more backward than physics in its development.

Section III. — The Biological Sciences

7. Biology. — ^All the objects of Nature may be divided into two great classes — the living or the organic, and the not-living or the inorganic. Biology is the name of that comprehensive science which treats of living matter and living things in all their grades, forms, and varieties. But in entering the field of biology we do not begin anew ; we carry with us a stock of mathematical, physical, and chemical conceptions. We have still to deal with numbers and forms, with the motion and rest of masses, and with the composition and internal changes of substances. These are indispensable keys to biological phenomena, and not an intelligent step can be taken without them ; but there is also a new order of ideas which is peculiar to this great field of thought, as those of organic structure, vital function, growth, development, waste and repair, alimentation,

THE BIOLOGICAL SCIENCES. 15

reproduction, &c. Biological subjects are therefore far more difficult to investigate, and are incapable of the exactness which belongs to the inorganic sciences ; still they comprise a great body of certain and most valuable knowledge.

8. Divisions of Biology. — The first division of Biology is that which everybody recognizes — the division into plants and animals, which gives rise to the two sciences of Botany and Zoology, But while this division is most obvious and natural, it does not answer the full purpose of scientific classification, which aims to group together all phenomena of the same kind, thus avoiding repetition in their treatment. Every living being, whether plant or animal, presents the same series of questions for consideration ; vegetable-biology would therefore be simply going over again the inquiries of animal-biology. These inquiries may be arranged into four groups, giving rise to four fundamental divisions of biological science.

9. Morphology. — This word, in its derivation, signifies the doctrine of forms. Applied to the organic world it is that division of Biology which treats of the forms or structures of living beings. It has several branches. For example, no living being is throughout of homogeneous substance ; the most of them are highly complex, from the union of many dissimilar parts. The statement of this structure constitutes Anatomy^ and if it is carried down to the minutest microscopical elements of the organism, it is known as Histology,

Again, no living being retains the same form and size throughout the course of its existence, but all grow, or pass through a series of changes, sometimes simple, sometimes very complicated, and the statement of these changes of form constitutes the branch of Morphology termed Development.

Furthermore, when the structure and development of any number of plants or animals have been ascertained, the question then arises of their resemblances and difterences. Thus the panther and the cat are more like each other than either is like the dog ; but they and the dog are more like each other than either is like the sheep ; while sheep, dog, and cat resemble each other more than either does a fowl. In this way plants and animals which resemble each other in internal and external .characters are arranged into groups to which a common name is applied, and this is Classification, The rude divisions of the vegetable world into trees, shrubs, and plants, and of the animal world into beasts, birds, and creeping-things, science carries out in a precise and accurate manner for all the races of living beings. Classification depends upon anatomy and development, and is grounded upon the facts which they have established, and the fulness v/ith w^hich this is done indicates the completeness of the science of Morphology.

10. Distribution. — This is the second great division of Biology. Very few plants or animals are found all over the world ; most of them are restricted to limited areas of the earth's surface. Of terrestrial animals and plants, some are found only at particular elevations ; while of aquatic creatures, some are found only at certain depths. Again, great numbers of animals and plants have existed in former periods of the earth's history Avhich do not now exist, and we get a knowledge of them through their fossil relics. The definition of the range of any plant or animal under any of these conditions — its location in space or in time — which leads to the knowledge of its environing circumstances, is its Distribution,

11. Physiology. — If we suppose an animal dead and petrified, its study might still give rise to all the branches of science hitherto enumerated. Not only Avould it exemplify the laws of quantity, physical properties, and a chemical constitution, but also all the branches of Morphology. Its structure or anatomy could be determined, its relations to other living beings, or its place in classification, and its position in space and in time, that is, its relations to surrounding nature, or its distribution. But when we conceive of it as alive, in motion, and undergoing changes, a new order of phenomena and a new set of inquiries are presented, w^hich give rise to the science of Physiology, the third great branch of Biology.

Every living being does certain things, performs certain

THE BIOLOGICAL SCIENCES. 17

actions which are called functions^ and is so far to be regarded as a machine working toward a given end. Physiology, therefore, considers the living being as a machine in action^ and inquires into the uses, operations, and mutual influence of its parts and the conditions under which its activity is maintained. Dealing with force or power, it considers living organisms under their dynamical aspects as Morphology regards them in their statical aspects.

Physiology is divided into animal and vegetable physiology, and animal physiology is again divided into Comparative Physiology^ which treats of the inferior races, and Human Physiology^ which considers the physiological phenomena of man. Because many of the inferior creatures have a simpler constitution, and are more accessible for purposes of investigation, the study of comparative physiology has been a great help to the advance of human physiology, and some knowledge of the former is of much value in prosecuting the latter.

12. Etiology. — Physiology treats of power, of which we know nothing except in its results. It involves the idea of causes producing effects, and is therefore a causal science. Morphology says that in such-and-such circumstances the living being is structured so-and-so. These are effects, and how produced it is the business of physiological research, as far as possible, to explain. The physiology of individual life thus expands into a broad inquiry concerning the causes of vital phenomena in general, and the limits within which living beings can be affected by external conditions. This more comprehensive physiology is termed Etiology, which literally signifies the doctrine of causes, and forms a fourth branch of biological science. The laws of the variations of living beings, of the modifications of individual organisms and successions of organisms, and of the influence of physical agencies on their position in space or their persistence in time, or the " dynamics of distribution," as it has been called, belong to this division of the general subject. It is the most complicated and least perfect of all the branches of Biology.

13. Claims of Physiological Study. — There are two classes of reasons why Physiology should be well studied by all who aspire to be in any tolerable degree educated. The first is, that it is a part^ and a most important part, of the great order of Nature which the human mind is adapted to miderstand. The first duty of a rational being is to cultivate in the best manner possible the higher powers of his nature, and in no w^ay can this be done so w^ell as by studying the plan of Nature, which is full of harmony, beauty, and the highest instruction. Thousands of the greatest minds that have appeared in the world have been occupied for ages in discovering the truths of Nature, and a large amount of the most valuable and interesting knowledge has thus been reached, of which past generations knew little, and the acquisition of which is the noble privilege of the present time. Is it right that all this vast research which has employed the genius of ages should go for nothing in education — that all this wealth of knowledge should be passed by as if it had no existence, and the young people of this country grow up as ignorant of it as if they had lived a dozen centuries ago ?

14. Applied Physiology— Hygiene. — Another and an imperative reason for studying Physiology is, that it opens to us a true understanding of our own natures. It teaches us how to take care of ourselves, to preserve health, to economize strength, and to improve and invigorate all our faculties. A large amount of the suff'ering of life comes from self-exposure and self-abuse, which take numberless forms. These may be avoided through proper knowledge conscientiously applied. Tlie truths of Physiology should therefore be inculcated and enforced early and earnestly, and with the emphasis of high religious duty.

Physiology treats of the laws of the human constitution in a state of health ; but so important is the application of physiological principles to the art of preserving heahh and preventing disease, that a second part has been added to the present work, treating definitely and separately of this application, the principles and rules of which constitute the art of Hygiene.

THE BIOLOGICAL SCIENCES. 19

Chapter II

A GENERAL VIEW OF THE STRUCTUPwE AND FUNCTIONS OF THE HUMAN BODY.

15. How bodily Actions are Studied.— The body of a living man performs a great diversity of actions, some of wbicli are quite obvious; others require more or less careful observation ; and yet others can only be detected by the employment of the most delicate appliances of science.

Thus, some part of the body of a living man is plainly always in motion. Even in sleep, when the limbs, head, and eyelids may be still, the incessant rise and fall of the chest continue to remind us that we are viewing slumber and not death.

But a little more careful observation is needed to detect the motion of the heart ; or the pulsation of the arteries ; or the changes in the size of the pupil of the eye with varying light; or to ascertain that the air which is breathed out of the body is hotter and damper than the air which is taken in by breathing.

And lastly, when we try to ascertain what happens in the eye when that organ is adjusted to different distances ; or what in a nerve when it is excited ; or of what materials flesh and blood are made ; or in virtue of what mechanism it is that a sudden pain makes one start — we have to call into operation all the methods of inductive and deductive logic ; all the resources of physics and chemistry ; and all the delicacies of the art of experiment.

16. Scope of Human Physiology. — The sum of the facts and generalizations at which we arrive by these various modes of inquiry, be they simple or be they refined, concerning the actions of the body and the manner in which those actions are brought about, constitutes the science of Human rhysiology. An elementary outline of this science, and of so much anatomy as is incidentally necessary, is the subject of the following chapters, of which I shall devote the present to an account of so much of the structure and such of the actions (or, as they are technically called, " functions ") of the body, as can be ascertained by easy observation, or might be so ascertained if the bodies of men were as easily procured, examined, and subjected to experiment as those of animals.

Section I. — TFork and Waste

17. Bodily Loss or Expenditure. — Suppose a chamber with walls of ice, through which a current of pure ice-cold air passes, the walls of the chamber will of course remain unmelted.

Now, having weighed a healthy living man with great care, let hmi walk up and down the chamber for an hour. In doing this he w411 obviously exercise a great amount of mechanical force, as much, in fact, as would be required to lift and push his weio;ht throuo-h the distance which he has raised himself at every step, and transported himself by all his steps. But, in addition, a certain quantity of the ice will be melted or converted into water, showing that the man has given off heat in abundance. Furthermore, if the air which enters the chamber be made to pass through lime-water, it wdll cause no cloudy white precipitate of carbonate of lime, because the quantity of carbonic acid in ordinary air is so small as to be inappreciable in this way. But if the air which passes out is made to take the same course, the lime-water will soon become milky, from the precipitation of carbonate of lime, showing the presence of carbonic acid, which, like the heat, is given off by the man.

Furthermore, even if the air be quite dry as it enters the chamber, that which is breathed out of the man, and that w^hich is given off from his skin, will exhibit clouds of vapor, wdiich vapor, therefore, is derived from the body.

After this experiment has continued for a longer or a shorter time, let the man be released and weighed once more. He will be found to have lost weight.

WORK AISTD WASTE. 21

Thus a living, active man constantly exerts mechanical force^ gives off heat^ evolves carbonic acid and water^ and undergoes a loss of substance,

18. A Physiological Income indispensable. — Plainly, this state of things could not continue for an unlimited period, or the man would dwindle to nothing. But long before the effects of this gradual diminution of substance become apparent, they are felt by the subject of the experiment in the form of the two imperious sensations called hunger and thirst. To still these cravings, to restore the weight of the body to its former amount, to enable it to continue giving out heat and water and carbonic acid at the same rate for an indefinite period, it is absolutely necessary that the body should be supplied with each of three things and with three only. These are, firstly, fresh air; secondly, drink, consisting of water in some shape or other, however much it may be adulterated ; thirdly, food, in which that compound known to chemists as protein^ and containing carbon, hydrogen, oxygen, and nitrogen, must be contained if it is to sustain life indefinitely ; and in which fatty and starchy or saccharine matters ought to be contained, if it is to sustain life conveniently.

19. Forms of Excretions. — Of this food a certain small proportion of useless and indigestible material leaves the body in the condition in which it entered it, and without ever being incorporated with its substance, as excrementitious matter. But, under healthy conditions, and with only so much food as is necessary, no important proportion of either protein matter, or fat, or amylaceous, or saccharine food leaves the body by this or any other channel. Almost every thing that leaves the body, in fact, does so either in the form of loater, or of carbonic acid, or of a third substance called zura, and of certain comparatively unimportant saline compounds.

20. Absorption of Oxygen. — Chemists liave dctennined that these products which leave the body and are called cvcrctions, contain, if taken altogether, far more oxygen than the food and water taken into the body. Now, the only possible source whence the body can obtain oxygen, except from food and water, is the air which surrounds it. And careful investigation of the air Avhich leaves the chamber in the imaginary experiment described above, would show, not only that it has gained carbonic acid from the man, but that it has lost oxygen in equal or rather greater amount to him.

21. Variation of the Physiological Balance.— Thus, if a man is neither gaining nor losing weight, the sum of the weights of all the substances above enumerated which leave the body, ought to be exactly equal to the weight of the food and water which enter it, together with that of the oxygen which it absorbs from the air. And this is proved to be the case.

Hence it follows that a man, in health, and ** neither gaining nor losing flesh," is incessantly oxidating and wasting away and periodically making good the loss. So that if he could be confined in the scale-pan of a delicate spring balance, like that used for weighing letters, in his average condition, the scale-pan would descend at every meal and ascend in the intervals, oscillating to equal distances on each side of the average position, which would never be retained for longer than a few minutes. There is, therefore, no such thing as a stationary condition, and what we call such is simply a condition of variation within narrow limits — a condition in which the gains and losses of the numerous daily transactions of the economy balance one another.

22. Conditions of this Balance. — Suppose this condition of daily physiological balance to be reached, it can be maintained only under the condition that the quantity of the mechanical work done, or of heat or other force evolved, remains absolutely stationary.

Let such a physiologically balanced man lift a heavy body from the ground, and his previous loss of weight will be immediately increased by a definite amount, which cannot be made good unless a proportionate amount of extra food be supplied to him. Let the temperature of the air fall, and the same result will occur, if his body remains as warm as before.

WOKK AND WASTE. 23

On the other hand, diminish his exertion and lower his production of heat, and either he will gain weight or some of his food will remain unused.

23. Equation of Food and Force. — Thus, in a properly nourished man, a stream of food is constantly entering the body in the shape of complex compounds containing comparatively little oxygen ; as constantly, the elements of the food are leaving the body, combined with more oxygen. And the incessant breaking down and oxidation of the complex compounds which enter the body is definitely proportioned to the amount of force the body exerts, whether in the shape of heat or otherwise : just in the same way as the amount of work to be got out of a steam-engine, and the amount of heat it and its furnace give oil*, bear a strict proportion to its consumption of fuel.

Section II. — Outlines of the Bodily Structure

24. Structure of the Vital Mechanism. — From these general considerations regarding the nature of life, considered as physiological work, we may turn for the purpose of taking a like broad survey of the apparatus which does the work. We have seen the general performance of the engine, we may now look at its build.

The human body is obviously separable into head, trunk, and limbs. In the head, the brain-case, or skull, is distinguishable from the face. The trunk is naturally divided into the chest or thorax, and the abdomen or belly. Of the limbs there are two pairs — the upper, or arms, and the lower, or legs; and legs and arms again are subdivided by their joints into parts which obviously exhibit a rough correspondence — thigh and arm, leg and forearm, ankle and w^rist, fingers and toes, plainly answering to one another. And the last two, in fact, are so similar that they receive the same name of ^' digits ; '' while the several joints of the fingers and toes have the common denomination of " phalanges."