iv COMPAKATIVE PHYSIOLOGY. 



before the student enough of comparative physiology in its 

 widest sense to impress him with the importance of recog- 

 nizing that all medicine like all science is, when at its best, 

 comparative ; and to show that the doctrines of evolution must 

 apply to physiology and medicine as well as to morphology. 



Comparative medicine is essentially broad. It will not do 

 to measure all the animals the veterinarian is called upon to 

 treat by the equine standard. This has been too much the 

 case in the past for the good even of the horse himself ; while 

 others, that fall to the practitioner's care, like the dog, have 

 been much neglected and misunderstood. 



There is no more reason, theoretically, why the veterina- 

 rian should overlook man than that the practitioner of human 

 medicine should disregard the lessons to be learned from our 

 domestic animals ; hence the attempt has been made to exclude 

 references to the human subject from the volume. The stu- 

 dent of comparative medicine may learn, by careful observa- 

 tion on himself, to understand much that would otherwise 

 never become realized knowledge ; and this conviction has ■ 

 been at the root of a large part of the advice given the stu- 

 dent as to how to study throughout the work. 



All that relates to reproduction and breeding is, in these 

 days of vast stock interests, of so much practical importance, 

 that on this account alone the fullest treatment of the subject 

 seems justifiable. But, apart from this, it has become clear to 

 me that function as well as form can be much better and 

 more easily grasped when embryology is early considered. 

 This I have tested, with the happiest results, with my own 

 classes. Usually those taking up physiology for the first 

 time are, of course, not expected to master all the details of 

 embryology, but the main outlines prove as helpful as inter- 

 esting ; hevertheless, it is my experience that a considerable 

 number of first-year men are not content to be confined to 

 the inerest rudiments of this or any other department of 

 physiology. 



That a work written on so new a plan as my Text-Book 

 of Animal Physiology should have met with a reception al- 

 most universally favorable, both in Britain and America, in 



