Hooker's New Physiology: Designed as a Text-book for Institutions of Learning

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Preface

I HAVE aimed bo to write tliia book, tliat it eball be fitted both for general reading, and for instruction. It ia designed for tlie family ns well aa for tho school. It eeeined desirable that these two objects elionld be accomplished at the same time, and I have not foacd them to be at all incompatible. The instruction needed bj the familj on this snbject doea not differ from that which is required in the school-room, either in regard to the facts to be communicated, or the manner in which it afiouJd be done. No one will question the truth of this, so far as the facts are concerned. But It is true even as 1« the mode of communicating them. In both casea there need t<i i<e clearness in statement, and fuUneaa of illustration. Actual inatruciion is to be given in both cases, and to miuda that are very neatly in the same attitude. 1 could not, therefore, see the necessity of writing a book on this subject for the people wiiieh should diffar from one written for the school. Besides, it has seemed to me desirable that there should be a, greater community of intereat between the school and the &milj 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 armnge the topira, 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 tho development of the whole subject soma 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 collegea in some parts of our country, its importance is no where as yet appreciated as it should be. It should be made aregular branch in our Educational System. This has been already done in Franco. "A competent knowledge," says Carpenter, "of Animal Physiology and Zoology ia there required ftonj every candidate for University honors ; and men of the highest scientific reputation do not think it beneath tliem to write elementary books, for the instruction of the

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

Many of the euhjects comprised in Phyaology have, in the cRse of most Btudenta, Ijeen already studied in a, diflerent phase, or mode, in other branches. Thus, if the student has attended to the Mechanical Powers in his Natural Philosophy, he finds in tlio human body the principles of the pulley aud the I'ivet illustrated in great variety end 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 admirahle manner. If he has studied Hydraulics, he Bees 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 — tlioso 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 andtheprocessesgoingoninthebody.

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 recnrs to these same branches with a renewed interest. Hydraulics, Pneumatics. Optics, &e., 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 conw.deration, 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 Phyaology to still other studies which should he noticed.

The analogies that exist between the human body and all other Irving 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 sea 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 pag'es, is essentially the same in the Plant as it is in the Animal. Botany, therefore, taught as it should bo, 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 out the analogies referred to, we lose a large XMirt of the IntereBt of the study. Human Physiology, the subject of study in tliis book, ia but a part nf. a Bcience which offers to the student wide fields of observation exceedingly diversified and full of interest. This being bo, I could not avoid in the following pages making oocaaonal references to the analogies existing between the phenomena of life as eshibited in tlio human syslem, and those which we see in the living world around us ; and as the student proceeds with the study, he will find himself inlerested in these in whatever form they are presented.

Tiis 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 edncation. It is the application of the principles of abstract science to the forms, and especially the iitiiig forms of nature all about us, that gives interest t« these prindples, and makes us to understand and appreciate them. It is here that we And a very serious defect in the prevalent mode of education, even at the present time, notwithstanding all our improvements. We live in the midst of a material world, animate and inanimate, and have daily converse, so to speak, with material forms of every vniicty, 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 sehool-room very neariy a sealed book. The very process of education shuts in the pupi! 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 tho school-room. How very few even of thoroughly educated adults, know the processes by which a plant or a tree grows I 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 the student. But it is very commonly not so. The mere technicalities and the classification are made much too prominent. Botany, really one of the moat interesting of all branches of natural sdence, is thus ordinarily made one of the driest of studies- To teaeh thU aright, the pheiumena of vegetation, go varied and so beautiful. shmM constitute (As chief material of inatractiort, and tlie mere datdfication should he considered, alt?u>ugh necessary, m wholly a secondary thing.

The great focta of the world, both of mind and matter, should furnish really the material for education, dBd those branches that ate ordinarily pursued with such assiduity should ha considered as merely subsidiary to the teaching of these facts. The whole order of education must be reversed. Instead of beginning the child's education with learning to spell ami read, the oliject shonld lie to make lilm an 6bserver of nature, and the spelling and reading should be done in connection with thia, and aa subaidiary to it. Things and not words, or mere signs, should from the first, conatitate the substantial part of in- Btruction. 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 impfljt t« him a spirit in consonance with the following precept of Hi^h Miller, the famous self-taught geologist : "Loam to make a Tight use of your eyes ; the commonest things aje worth looking at — even stones and weeds, and the moat familiar animals."

Aa it is now, no one becomes e. naturalist early in life, escept in apite of the tendencies of his education. The study of nature is not only not encouraged, hut 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 txaining 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 everv student, even from his cliildhood, encouraged to pursue, in a measure at least, by the eiterna! circumstances of his educaUon. The tendencies of hia training ahould 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^uere drudgery than it now has. Not that there woiild be any the less labor; but the labor n-ould bo made lighter by the interest imparted to it— the interest which always results from the study of facts and phenomena, and never from tho 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.

Tho change which I have pointed out can not he efifected at once. It will require time. Confirmed traditional customs are to be done away, the habits of teachers are to 1>e altered, and the proper books are lo a great extent to be yet written, especially such as are fitted for tlie first years of education.

If the study of nature should be thuB made prominent in education, human physiology would bo considered altogether its moat 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 'oS processes, as in the human body, in nothing else in the wide world are the principles of so many departments of science so Hst«nsively and perfectly exemplified. Life works here its most complicated set of machinery. Secondly : the singular and mjateriona connection of the immaterial and immortal soul with the material and perishable body, ^ves intense Interest to thia study, lu PhjBJology we do not study matter alone, or spirit alone, but both matter and spirit united, and often acting together. This circumstance distinguishes thia from all other studies. Thirdly : it is our tw^n frames, moved by the spirit within ub, 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 j udiciouH and efQdent Hygiene must be baaed upon a knowledge of the laws of physiology. We can not know how to teep 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 congeries of mechanisms as are presented in man would naturally suggest, iu regard to the skill of the great Builder of the universe. Such reflections would estend 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 nnderBtanding them, there has been a disposition in many minds to go beyond what we know, and indulge in unwarranted Bpeonlation. On these points I have taken pains to draw the line very distinctly between what is known, and what is supposed. 1 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 minglingof fiicts and supposilions together in one indiscriminate mass, as 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 olistaclee to the progress of truth on all subjects, both in individual minds, and in tliu minds of the community at large. This disposition, so apt to be fostered in the enthusiastic mind of youth, by ingenious but dreamy speculations, should be corrected at the outset, and the mind should, in its forming stage, bo habituated to the discrimination between the proved, the true, and that which rests on presumptive, perhaps merely plausible evidence. This discrimination should therefore be exemplified in books designed for inslruction, and this 1 have attempted in the

SneGESTIONS TO TEACHERS.

Is order to be able to teach from this book properly, tlie teacher should himself study all of it thoroughly before he begins his inetructioQ. If he merely keep a little m advance of hia class, he wOl fail ia bia conceptions of the general scope and plan of the hook. 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 poicts about which inquiry is made, wliich of course he cau do. under the circumstances, in an imperfect manner at the beat, he can satisfy the scholar by informing him that these points will be found explained in thar 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 m tho mode of developing the topics to the ml ads of his pnpils.

It must be obvious to any teacher that he can teach the minutia? of the subject with more ot interest to say aothing of thoroughness, if, while doing it, he takes Jn 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 he profitable occasionally for tho 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 tho preparation of the work.

The teacher should read the book through in course. If, instead of doiuK 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 j ust this preparation is aimed at in the first part of the book. And beddes, it is quite important that the subjects treated of should be developed to the mind of the teacher in the Bftme order in which they are to be developed to the minds of his pupils.

In the engrayings, clearness has been aimed at rntlier than beauty. Yet I should not do the engraver jnstioe if I did not eaj', that in beanty they are generally quite equal to those which we find in our atandard professional works on phyaology. It is to be home in mind that wood-ciita cannot represent correctly the heaaty and delicacy of living structures. These can be rea] ized only by seeing the Btractures them- Belves. Another thing to be kept in mind is, that parts which are represented in engravings with deSnite 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 parts together.

The teacher can be aided very much in (Sving 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 lungs 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 os'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 oaitilages that make up the larynx, can be olitwned from the laryns of an ox or a cow. The general shape and arrangement are

It is some trouble to clear the parts of muscular substance, bnt 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 laryns. 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 Jife, with its wonderful mechanisms, wherever they may be seen. All living nature thns becomes full of suggestive interest to the young

There are some things of which plates can give no correct idea. Such, for example, is the cellular membrane. The attempt to repro- Bent it is made in most books on phyMology, 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 scholar an idea of it as it appears to the naked eye in its natural condition, I refer him to it aa n the muscles and between xiv SUGGESTIONS TO TEACHERS.

the fibres of each muscle. The teacher can use a piece of moat for thia purpose. The difference between muscles, tfindons, and ligaments

Those figures which are mere diagrams it will be well for the scholar to draw on the blackboard, and his still in description and remark may be esercised for his own benefit and fbr that of the claaa. He should bo trained in this erercise in such a way that he will acquire the power of (flvinjf 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 pendl of parts which contwn the answers to the questions, so often done in oar schools, should never be permitted by the teacher, for reasons that I need not stop to notice.

The scholar should read the test 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 esercise 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 £iny important point has escaped his recol. lection, or tailed to make the proper impression on liis mind.

The questions tliat 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 diflferent capacities and mental attitudes which he Ends in his class.

It is best not to have an uniform mode of asking questions, even with the same scholar. Variety should be g^ven to the mode of hearing the redtation. 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 sub-

The numbers attached to the questions refer fo 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, The Crystal antJ the Plant are both wonderful growths. 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 aie different in the two eases. 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 intror duced into passages and interstices. It grows by absorption or by intussusception.

2, (h'ifans. — 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 Frinciples, — These organs, which thaa absorb, and circulate, and construct, do not act simply on mechanical 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 powcKi could alone supply the leaves of the mighty tree of the forest with s«p 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 fonnd 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 nnorganized matter,

3. 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.

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

The whole material world, then, that we see aronnd us, we divide into two parts — the unorganized and lifeless, and the organized and living. The distinctions thus pointed out between organiaed 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 ae we examine those of minerals. The chemist can aBcert^» aU 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 AND UNORGANIZED SUBSTANCES. 3

to know all abont 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,

8. Assimilation in Organised 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 prodnced 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 to circulate. It is carried up through the vessels of the trunk or stalk to the leaves. There the last step of the process is taten, and the eap 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 iioured 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 Btomach reqaires gome little explanation, as it is uaed in phy^ology in two senaea — in a limited aense, and also in an extended one. It is uaed in its limited aense, ae referring to the cavity at the beginning of the alimentary canal, aa it is tenned ; this latter term being applied to the aeries ol cavities, the stomach and the small and large inteatinea, which are found in the digestive appatatue in tie higher orders of animala. In comparisona, however, between theae animals and those which have a more wmple digestive apparatua, the word stomach is uaed in a more extended aenae, as being sTnonymous