Hooker's new physiology

Front matter

-PROF.JASEWAIL

HHJNH

Sheldon <& Company s Text-Books.

Preface

I, HAVE aimed so to write this book, that it shall be fitted both for general reading, and for instruction. It is designed for the family < 11 as for the school. It seemed desirable that these two objects should be accomplished at the same time, and I have not found them to be at all incompatible. The instruction needed by the family on this subject does not differ from that which is required in the schoolroom, either in regard to the facts to be commuuicated, or the manner in which it should be done. No one will question the truth of this, so far as the facts are concerned. But it is true even as to the mode of communicating them. In both cases there need to be clearness in statement, and fullness of illustration. Actual instruction is to be given in both cases, and to minds that are very nearly in the same attitude. I could not, therefore, see the necessity of writing a book on this subject for the people which should differ from one written for the school. Besides, it has seemed to me desirable that there should be a greater community of interest between the school and the family than as yet exists ; and this object, books equally interesting to both will tend to promote.

I have avoided technical terms so far as possible. Whenever they are used they are sufficiently explained at the time, so that no glossary is needed. Some points commonly considered hard to be understood are treated of, but I have endeavored to simplify them, by full illustration, and by a presentation of the truth uncomplicated with speculations and hypotheses. And these points are so introduced, that the mind is prepared by the previous investigation to understand them. I have aimed so to arrange the topics, as to have a preparation constantly going on in the mind of the student, fitting him for the proper understanding of what is to follow. By this natural gradation in the development of the whole subject some of the deep things in Physiology can be made clear, which it would otherwise be impossible for the student to understand.

Although Physiology is becoming a prominent study in the schools and colleges in some parts of oar country, its importance is no where should be. It should be made a regular branch in our Educational System. This 1ms been already done in Prance. 'A competent knowledge," reenter, "of Animal Physiology

and Zoology is there required from every candidate for University

Till PREFACE.

honors ; and men of the highest scientific reputation do Dot think it beneath them to write elementary books, for the instruction of the beginner."

The importance of Physiology as a study, will appear from various considerations.

Many of the subjects comprised in Physiology have, in the case of most students, been already studied in a different phase, or mode, in other branches. Thus, if the student has attended to the Mechanical Powers in his Natural Philosophy, he finds in the human body the principles of the pulley and the lever illustrated in great variety and perfection. The principles in relation to strength in the form and arrangement of structure he sees exemplified in the framework of the body in the most admirable manner. If he has studied Hydraulics, he sees in the body the most perfect, and at the same time the most complicated hydraulic machinery, working incessantly throughout life in the circulation of the blood. The principles of Pneumatics he finds applied in the respiration — those of Optics in the eye — those of Acoustics in the ear — and those of Musical Sounds in the apparatus of the voice. And then, his chemical knowledge meets with new applications in his observation of the changes and the processes going on in the body.

The relations, then, of Physiology to some of the common branches taught in the higher classes in schools, are of the most intimate character. Physiology, in part, merely extends these branches into a new and interesting field ; and the student who has once entered this field recurs to these same branches with a renewed interest. Hydraulics, Pneumatics, Optics, &c, have now a new attraction for him, from this, to him novel, application of their principles. The interest thus awakened in his mind is worth much in itself, aside from the mere addition made to his knowledge. And the interest is enhanced by the consideration, that in the human body he sees the applications of these principles to mechanism that exhibits the skill of perfect wisdom and almighty power.

But there are relations of Physiology to still other studies which should be noticed.

The analogies that exist between the human body and all other living things, in relation to structure and growth, are numerous and striking. Though life is so diverse in its processes and in the forms which we see it evolve in the whole range of animated nature, it in some important respects displays a great similarity, which it is interesting to trace throughout its diversified manifestations. Growth, or nutrition, as you will see in the following pages, is essentially the same in the Plant as it is in the Animal. Botany, therefore, taught as it should be, has quite an intimate relation to Animal Physiology. The Science of Life is, in many respects, one Science ; and if, in studying any of its subdivisions, we fail to take this broad view of it, and to trace

PREFA< IX

out the analogies referred to, we lose a large part of the interest of the study. Human Physiology, the subject of study in this book, is but a part of a science which otters to the student wide fields of observation exceedingly diversified and full of interest. This being so, I could not avoid in the following pages making occasional references to the analogies existing between the phenomena of life as exhibited in the human

m. and those which we see in the living world around us ; and as the student proceeds with the study, he will tind himself interested in in whatever form they are presented.

This leads me to say that this study of nature, in its broad common relations and its beautiful and extensive analogies, should be made very prominent in our systems of education. It is the application of the principles of abstract science to the forms, and especially the licit) g forms of nature all about us, that gives interest to these principles, and makes us to understand and appreciate them. It is here that we find a very serious defect in the prevalent mode of education, even at the

Dt time, notwithstanding all our improvements. We live in the midst of a material world, animate and inanimate, and have daily conto speak, with material forms of every variety, presenting phenomena of the highest interest and of endless diversity. And yet, through almost all the period of childhood, and perhaps we may say youth also, this book of nature is in the school-room very nearly a sealed book. The very process of education shuts in the pupil from this broad contemplation of the world in which he lives. He is drilled through spelling, reading, grammar, &c., but he is left in total ignorance of the beautiful flowers, and the majestic trees outside of the

il-room. How very few even of thoroughly educated adults, know the processes by which a plant or a tree grows! And the same can be said of other phenomena of nature.

The defect which I have pointed out runs through the whole of education. We can see it even in the prevalent mode of teaching the natural sciences themselves. One would suppose that here the facts, the phenomena, would command the chief attention of the teacher and student. Bur it is very commonly not so. The mere technicalities and the classification are made much too prominent. Botany, really one of the most interesting of all branches of natural science, is thus ordinarily made one of the driest of studies. To track this aright, tfie getation, s > varied and so beautiful, should constitute tlie . and the mere classification should be coni /■//. as wholly a secondary tlnnrj.

The great faets of the world, both of mind and matter, should

furnish really the material for education and those branches that are

ordinarily pnrsoed with such assiduity Bhould be considered as merely

idiaryto the teaching of these facts. The whole order of education

must be reversed. In.-tead of beginning the child's education with

X PREFACE.

learning to spell and read, the object should be to make him an observer of nature, and the spelling and reading should be done in connection with this, and as subsidiary to it. Things and not words, or mere signs, should from the first, constitute the substantial part of instruction. The child should be made, at home, in the school, and everywhere, a naturalist in the largest sense of that word. We should aim to impart to him a spirit in consonance with the following precept of Hugh Miller, the famous self-taught geologist : " Learn to make a right use of your eyes ; the commonest things are worth looking at — even stones and weeds, and the most familiar animals."

As it is now, no one becomes a naturalist early in life, except in spite of the tendencies of his education. The study of nature is not only not encouraged, but is absolutely discouraged in our educational system. If any one, like Hugh Miller, by the force of a taste that can not be repressed by the training of the school-room, undertakes to make a " right use of his eyes," and curiously examines " stones and weeds," he is regarded by the world of spellers and readers and grammarians and cipherers, as a strange genius. But he is pursuing, from an irresistible internal force, the very course that I would have every student, even from his childhood, encouraged to pursue, in a measure at least, by the external circumstances of his education. The tendencies of his training should be decidedly in this direction.

If the general mode of education were changed in the manner indicated, education would have much less of the character of mere drudgery than it now has. Not that there would be any the less labor ; but the labor would be made lighter by the interest imparted to it — the interest which always results from the study of facts and phenomena, and never from the learning of mere words and technicalities and classification. I would gladly dwell on this subject, and show by varied illustrations how the mode of instruction referred to, should be pursued, and especially with younger scholars ; but the limits of a preface will not allow me to enter so large a field.

The change which I have pointed out can not be effected at once. It will require time. Confirmed traditional customs are to be done away, the habits of teachers are to be altered, and the projfer books are to a great extent to be yet written, especially such as are fitted for the first years of education.

If the study of nature should be thus made prominent in education, human physiology would be considered altogether its most interesting and important branch, and for several reasons. First: there is nowhere to be found so curious a collection of mechanisms, or so interesting and wonderful a series of processes, as in the human body. In nothing else in the wide world are the principles of so many departments of science so extensively and perfectly exemplified. Life works here its most complicated set of machinery. Secondly : the singular

PREFACE. XI

and mysterious connection of the immaterial and immortal soul with the material and perishable body, gives intense interest to this study. In Physiology we do not study matter alone, or spirit alone, but both matter and spirit united, and often acting together. This circumstance distinguishes this from all other studies. Thirdly : it is our own frames, moved by the spirit within us, that we study. The subject has a personal interest for us that is not presented by most studies, and by none In so large a degree as in this. And, fourthly : the study is of great importance, because a judicious and efficient Hygiene must be based upon a knowledge of the laws of physiology. We can not know how to keep our functions in the condition of health, without understanding the laws that regulate them. I have said but little in this book in regard to hygiene, and that only incidentally, because that subject would require of itself a whole volume to elucidate it properly.

I have not thought it proper to indulge to any great extent in those reflections which the contemplation of so perfect and diversified a l lies of mechanisms as are presented in man would naturally suggest, in regard to the skill of the great Builder of the universe. Such reflections would extend the book to too great length. Besides, they are so readily suggested to the mind of both teacher and scholar, that it is entirely unnecessary for the author to dwell on them.

I have treated of some subjects on which, from the difficulty of understanding them, there has been a disposition in many minds to go beyond what we know, and indulge in unwarranted speculation. On these points I have taken pains to draw the line very distinctly between what is known, and what is supposed. I deem it important to prevent the minds of the young from being led away from the simple truths of science by ingenious speculations and plausible reasonings. Let me not be understood to decry all hypothesis. I object only to the mingling of facts and suppositions together in one indiscriminate mass, a- is often done. The disposition to do this, which is more common than is generally supposed, exerts so injurious an influence upon the habits of the mind, and so confuses its views of truth, that we ought to look upon it as one of the most serious evils to be guarded against in education. It is really one of the most prominent obstacles to the pmirress of truth on all Bubjects, both in individual minds, and in the minds of tie- community at large. This disposition, so apt to I I in the enthusiastic mind of youth, by ingenious but d*

should be corrected at the outset, and the mind should, in its forming Stage, be habituated to the discrimination between the

proved, the true, and that which rests on presumptive, perhaps merely plausible This discrimination should therefore be exempli-

fied in books designed for instruction, and this I have attempted in the volume,

SUGGESTIONS TO TEACHERS.

In order to be able to teach from this book properly, the teacher should himself study all of it thoroughly before he begins his instruction. If he merely keep a little in advance of his class, he will fail in his conceptions of the general scope and plan of the book. If the interest of the subject awaken in him and in his pupils a spirit of inquiry, there will be a continual looking forward to points which are explained and illustrated further on in the book.

Now if the teacher has made himself master of all the subjects treated of, instead of turning off the inquiry of a scholar without an answer, or even the promise of an answer in the future, or endeavoring to clear up the points about which inquiry is made, which of course he can do, under the circumstances, in an imperfect manner at the best, he can satisfy the scholar by informing him that these points will be found explained in their proper place at a future stage of the investigation.

I have aimed to have every topic treated of in its right place in the development of the general subject, and the teacher should be thoroughly master of the whole book at the outset, in order that he may fully carry out my plan in the mode of developing the topics to the minds of his pupils.

It must be obvious to any teacher that he can teach the minutiae of the subject with more of interest, to say nothing of thoroughness, if, while doing it, he takes in the general views presented, and has in mind the relations of the particular topics in hand to other branches of the subject. Indeed it will be profitable occasionally for the teacher to afford the scholar some glimpses of the interesting fields to be explored further on, taking care, however, not to anticipate so much as to mar the natural method and order of developing the whole subject, which I have taken such especial care to observe in the preparation of the work.

The teacher should read the book through in course. If, instead of doing this, he opens to some chapter in the middle or latter part of the book, he may get the impression that too high matters are treated of, and that the minds of his pupils are not competent to understand them. They cannot be understood unless there be a preparation of mind for them ; and just this preparation is aimed at in the first part of the book. And besides, it is quite important that the subjects treated of should be developed to the mind of the teacher in the same order in which they are to be developed to the minds of his pupils.

SUGGESTIONS TO TEACHERS. Xl.l

In the engravings, clearness has been aimed at rather than beauty. Yet I should not do the engraver justice if I did not say, that in beauty they are generally quite equal to those which we find in our standard professional works on physiology. It is to be borne in mind that woodcuts cannot represent correctly the beauty and delicacy of living structures. These can be realized only by seeing the structures them. selves. Another thing to be kept in mind is, that parts which are represented in engravings with definite lines for the sake of distinctness, are ordinarily not thus distinct in the structures. To make them so, the dissecting knife must separate them, and take off the cellular substance, which, as the general packing material of the body, everywhere connects adjacent pans together.

The teacher can be aided very much in giving his scholars a correct idea of different organs, by presenting to them organs taken from the bodies of animals. Thus, in giving them an idea of the lungs, the lungs of a calf or a sheep can be used. A pipe may be fastened into the windpipe ; and by blowing into this, you can show how the iungs are inflated. An idea of the appearance of the human brain can be given by means of the brain of a calf, or any other animal of sufficient size. An ox's heart may be used in showing the structure and arrangement of the valves and other parts of that organ, for they are essentially the same as in man. A very good idea of the arrangement of the cartilages that make up the larynx, can be obtained from the larynx of an ox or a cow. The general shape and arrangement are me as in man.

It is some trouble to clear the parts of muscular substance, but the teacher can get some physician or medical student to do it for him. When the preparation is once made, it can be dried for permanent use. I have one which I made twenty-five years ago. In drying, it will be necessary to keep the wings of the thyroid cartilage apart by a wedge, and the supple epiglottis must be placed in such a position as not to interfere with a view of the interior of the larynx. The large eye of the ox can be made use of to show the various parts of that organ, and also to show the formation of the images of objects on the retina.

One great advantage of thus using parts from different animals is, that a taste is given for the examination of the phenomena of life, with its wonderful mechanisms, wherever they may be seen. All living nature thus becomes full of suggestive interest to the young stud

There are some things of which platos can give no correct idea. Such, for example, is the ct'llular membrane. The attempt to r sent it is made in most books on physiology, but it is an entire failure. I have a plate representing its cells as seen in a dried preparation under the microscope; but to give the Bcholaran idea of i pear> taked eve in its natural condition, 1 refer him t<>

seen in any common piece of meat between the muscles and between

XIV SUGGESTIONS TO TEACHERS.

the fibres of each muscle. The teacher can use a piece of meat for this purpose. The difference between muscles, tendons, and ligaments can be shown in the same way.

Those figures which are mere diagrams it will be well for the scholar to draw on the blackboard, and his skill in description and remark may be exercised for his own benefit and for that of the class. He should be trained in this exercise in such a way that he will acquire the power of giving well-proportioned and well -arranged descriptions, without the aid of prompting by minute questions from the teacher.

It will be proper to say something of the use which should be made of the questions that I have prepared. I have two . reasons for not placing them at the foot of the page. One reason is, that the book is designed for general reading as well as for instruction. But the chief reason is, that I wish to prevent a too free use of questions on the part of both teacher and scholar. The marking with the pencil of parts which contain the answers to the questions, so often done in our schools, should never be permitted by the teacher, for reasons that I need not stop to notice.

The scholar should read the text at first without reference to the questions ; and then the questions can be made use of, perhaps with profit, to fix definitely in the mind the principal points that are brought out. It will be a useful exercise for the scholar, after reading a page or two, to think over the main points, and then see by the aid of the questions whether any important point has escaped his recollection, or failed to make the proper impression on his mind.

The questions that I have constructed will, I think, be found to be fitted to the great majority of scholars. But of course the teacher will vary them to suit the different capacities and mental attitudes which he finds in his class.

It is best not to have an uniform mode of asking questions, even with the same scholar. Variety should be given to the mode of hearing the recitation. Sometimes the questions should be minute, and at other times the mind of the scholar should be left to go on with as little leading as possible.

The scholar should be encouraged occasionally to give the substance of a whole paragraph, or even of more than this. In doing so, any failure in arrangement or proportion can be noticed by the teacher, for the benefit not only of the scholar that is reciting, but also of the whole class. The general scope of an argument may also be given in the same way, and the manner of doing it be made the subject of criticism.

The numbers attached to the questions refer to the pages, this being more convenient to the scholar than a numbering by paragraphs would be, though of course it cannot be quite so definite in all cases.

Physiology and Hygiene.

Chapter I. Organized And Unorganized Substances

1. Tlie Crystal and the Plant are both wonderful groicths. The crystal was once a minute nucleus, and the plant was once a little germ.

In one respect they are alike in their growth — both have increased from particles taken from things around them. But the processes by which this is done are different in the two cases. The crystal has increased or grown by layer after layer of particles. Any part of it, when once formed, is not altered. It can receive additions upon the outside alone. The plant enlarges by particles which are introduced into passages and interstices. It grows by absorption or by intussusception.

2. Organs, — This absorption is effected by certain vessels or organs, constructed in the root of the plant for this purpose. These absorb or take up fluid matter from the earth. Other organs circulate this fluid through all the plant ; and still others use it for the purpose of growth or formation* There are no such organs in the crystal, for it has no inner growth. The plant is therefore said to be an organized substance or being, and the crystal an unorganized substance.

3* Mechanical Principles. — These organs, which thue absorb, and circulate, and construct, do not act simply on m al principles. They are active agents, and they perform their duty with a force, and after a manner, for which no mechanical principles can account. No mechanical powers could alone supply the leaves of the mighty tree of the forest with sap from its deep roots ; much less could they form those leaves.

4. Chemical Principles. — Neither do these organs act simply on chemical principles. While man, through the agency of chemistry, can form some of the crystals which are found in nature, he can not by any arrangement of constituents make a plant, a flower, or a leaf. And the plant, left alone to the action of chemical principles, wilts ; and at length ceases to be a plant, and becomes common unorganized matter.

5. Vital Principles. — Mechanical and chemical principles, it is true, are both exhibited to .some extent in the growth of plants ; but they are under the control of other principles, which we term vital. So the plant is not only an organized substance, but a living being.

6. Animals. — What has been said of plants, in distinction from minerals, may also be said of animals. They are also organized living beings, and they have, generally, a more complex organization than plants.

The whole material world, then, that we see around us, we divide into two parts — the unorganized and lifeless, and the organized and living. The distinctions thus pointed out between organized and unorganized matter are essential and fundamental. But let us look at some other distinctions, which either arise from these or accompany them.

7. Other Distinctions between the Organic and Inorganic. — All the parts of the mineral are independent of each other, while it is otherwise with the plant or the animal. Accordingly, we do not examine the properties of plants and animals as we examine those of minerals. The chemist can ascertain all the properties of a crystal or a rock if you give him but a small piece of it.

But the botanist can not ascertain all the properties of a plant by looking at some one part of it. If he examine the flower, this gives him no knowledge of the root. In order

ORGANIZED AXD UNORGANIZED SUBSTANCB& 3

to know all about the plant, he must examine every part by itself, and then look at it in its relations to the other parts. The same may be said of the physiologist, in his investigation of the properties of animals.

S. Assimilation in Organized Substances. — As the crystal is forming by layer after layer of particles, no change is effected in these particles as they are becoming arranged in the layers. But in the case of the living organized being, a change is produced in the particles which are taken up by the absorbents. And the change, ordinarily, is both a gradual and a complex one. In the plant, a change is produced in the particles in the very act of absorption ; but this change is only the beginning of a process which is afterwards perfected. The sap is not thoroughly fitted for nutrition when it first begins tp circulate. It is carried up through the vessels of the trunk or stalk to the leaves. There the last step of the process is taken, and the sap is now ready to be used in the growth of the plant or tree.

So, also, in the animal, the nutritious part of the food, taken up by the absorbents in the digestive organs, is first acted upon by certain little glands, through which it passes, is then poured into the circulation, to be mingled with the blood, and is carried with the blood to the lungs, to be exposed to the air ; and thus it is fitted for the nutrition or growth of the body

This process, which is thus carried on in the plant and in the animal, is very properly called assimilation. For the particles that are taken up by the absorbents in the root of the plant are, by this process, made like to the plant ; and the particles taken up by the absorbents in the stomach*

* The word stomach requires some little explanation, as it is used in

physioloiry in two senses — in a limited sense, and also in an extended

It is U3ed in its limited sense, as referring to the cavity at the

j of the alimentary eanal, as it is termed; this latter term