A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction, for students of human and comparative (veterinary) medicine and of general biology

Front matter

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A TEXT-BOOK OF

Preface

The comparative method, the introduction of the teachings of embryology and of the welding principles of evolution as part of the essential structure of zoology, may be said to have completely revolutionized that science ; and there is scarcely a text-book treating of the subject, however elementary, which has not been molded in accordance with these guiding lines of thought. So far as I am aware, this can not be said of a single book on the subject of physiology. Feeling, therefore, that the time had come for the appearance of a work which should attempt to do, in some degree at least, for physiology what has been so well done for morphology, the present task was undertaken. But there were other changes which it seemed desirable to make. I tliink any one who will examine the methods and reasoning of the physiology of the day will not fail, on close scrutiny, to recognize a tendency to speak of certain conclusions, for various organs (and functions), as though they applied to these organs in whatever group of animals found, or, at all events, for man, no matter what the species of the animal that liad been experimented upon. For some years I have, in publications of my own original researches, strongly protested against such methods as illogical. I am wholly at a loss to understand how a work, built upon the most fragmentary and heterogeneous evidence, derived from experiments on a few grf)ups of animals, or a certain amount of human (clinical or pathological evidence, can be fittingly termed a treatise on " human j>hy..siology." It will scarcely bo denied that conclusions such

VI

ANIMAL PHYSIOLOGY.

as this method implies would not be tolerated in the sub'^ect of morphology.

While in the present work what is strictly applicable to other animals and to man has not always been kept apart, an effort has been made throughout to be cautious in all the conclusions drawn — a state of mind warranted by the past history and the present tendencies of physiology. Until our laboratory methods become more perfected, the comparative method more extensively applied, and conclusions drawn from "experiments" modified by comparison with the results of clinical, pathological, and all other available sources of information, I feel convinced that we are called upon to teach cautiously and modestly.

Treating, as we do in our books, each subject in a separate chapter, there is, as I know by observation, the greatest danger that the student may get the idea that each function of the body is discharged very much independently ; accordingly, there has been throughout a most persistent effort made to impress the necessity for ever remembering the absolute dependence of all parts. Unless this be thoroughly infused into a student, it is impossible that he can ever understand the wide world of natural objects, or the narrower one of unnatural (in a sense) organisms, as seen in the hospital ward.

Recognizing how important it is to teach the young student to become an observer and an investigator in spirit and in some degree in fact, only such treatment of elaborate methods has been introduced as will enable him to form a general acquaintance with the modes in which laboratory work is carried on, while simple ways of verifying the essential truths of physiology have been constantly brought before, him. As to how far these are actually carried out will depend not a little on the teacher. The student who learns thus to observe and to verify will not fail to apply the method in his future career, whatever that may be — whether medical or other — nor is he so likely to throw his physiology overboard as a useless cargo as soon as his primary examination has been passed.

PREFACE. vii

By frequently calling attention, as has been done tlirongliout, to actually discovered or possible differences in function for different groups of animals, it is believed that the student will become possessed of a spirit of caution in drawing conclusions that will fit him the better for the hospital ward in another respect, viz., that he will be prepared for those individual differences actually existing, and which seem to have been largely ignored in so many works on physiology, with the natural consequence that the student, not finding his physiology squaring with the facts of the clinique, and not being prepared for the situation, the result is disappointment and disgust, instead of the actual continuation of the study, especially as human physiology.

With a view of widening the student's field of vision, sections, under the heading " Special Considerations," have been introduced, which it is hoped will not fail to interest and stimulate.

Most teachers of experience will welcome the summary with which each chapter concludes. In connection with no subject perhaps can the art of generalizing be better taught than with physiology, and to this end these brief synoptical sections will, it is thought, prove helpful.

Systematic instruction in either macroscopic or microscopic anatomy has not been undertaken — in fact, can not be attempted, it is believed, except at the expense of physiology proper — in a work of moderate compass. At the same time attention has been called to those points which have a special bearing on each function, and a number of illustrations have been inserted with this object in view.

The introduction of the subject of development at so early a stage is a departure that calls for a word of explanation. An attempt has been made to use embryological facts to throw light upon the different functions of the body, and especially their relations and interdependence. It therefore became necessary to treat the subject early. It is expected, however, that the student will return to it after reading the remaining chapters of the woik.

yiii ANIMAL PHYSIOLOGY.

As so large a proportion of those who enter upon the study of medicine begin their career without any adequate preparation in general biology, the subject, as presented in this work, will, let me hope, meet an actual need, and prove helpful in attaining a broad and sound view of the special doctrines of biology.

It is scarcely necessary to remark that clinical and pathological facts have not been introduced with the view of teaching either clinical medicine or pathology, but to indicate to the student how his physiology bears on his profession, and how the above-mentioned subjects throw light upon physiology proper and lend interest to that subject.

My aim has been to make the book, from first to last, educative ; and, retaining a vivid recollection of the severe strain put upon the memory of the medical student by our present method of crowding so much into at most four years of study, an attempt has been made to avoid overloading the book with mere facts or technical details, as well as to present the whole subject in as succinct a form as is compatible with clearness. Recognizing, too, the very shifting character of physiological theories, the latter have generally been pretty well kept apart from the actual facts.

It is hoped that the abundance of the illustrations will prove more acceptable than would lengthy treatment of subjects in the text, for, if the matter of a book is to be digested and assimilated, either by the student of general biology or by the hard-worked medical student, it must not be bulky.

The illustrations have been chosen from the best available sources, and the authorship of each one duly acknowledged in the body of the work. Several original diagrams, such as I find exceedingly useful in my own lectures, have been introduced.

This book is really an embodiment of my own course of lectures, as given during the past two years more especially, and with the highest satisfaction, I think it may be said, to both students an.d teacher.

I have unbounded confidence in the plan of the work, and

PREFACE. , ix

I ti'ust that its newness may excuse, to some degree, any shortcomings in the execution. Such a book has become a necessity to myself, and it is hoped will be welcomed by others. I trust the work may prove suitable, not only for the student of luiman medicine, but for the increasing number of students of comparative or veterinary medicine, who may desire a broad basis for the study of disease in the various animals they are called upon to treat. I have endeavored to make the work specially acceptable to the student of general biology.

It only remains for me to crave the indulgence of all readers, and to thank my publishers, Messrs. D. Appleton & Co., for their uniform courtesy and the great pains they have taken to present the work in worthy form.

Wesley Mills.

Physiological Laboratory, McGill University', Montreal, September, 18S9.