20 INTRODUCTION. 



it occurs in the vegetable kingdom aids very much in elucidating 

 the process of reproduction in the human species. 



Animal Physiology. The same organs in different animals per- 

 form their functions in different ways. Thus the stomach of the 

 cow and that of the dog act very dissimilarly, and a knowledge 

 of the one would aid very little in acquiring a knowledge of the 

 other. What is true of the stomach is true of other organs to a 

 greater or lesser degree. Each class of animals has its own peculi- 

 arities as to function that is, has its own physiology. One who 

 intends to devote his life to the treatment of the diseases of the 

 lower animals must study the functions of those animals, while 

 one who is preparing himself for the cure of human diseases must 

 understand the functions of the organs of the human body, or 

 Human Physiology. 



Many hints, it is true, may be obtained by the student of 

 human physiology from a study of the processes which take place 

 in the lower animals, and many of the most valuable contributions 

 made to physiologic science have been based upon such a study ; 

 but it must ever be borne in mind that specific differences exist, 

 and that we cannot infer too much from such observations. Thus 

 one who studies the process of stomach digestion in a ruminant, 

 such as the cow, will make a most serious blunder should he sup- 

 pose that the process is the same in man. Errors of a similar 

 character, though perhaps less glaring, have been made, notably 

 in the process of reproduction. This process is so obscure that 

 many opportunities which have presented tnemselves for investi- 

 gation, both in the lower and in the higher animals, have been 

 seized upon ; but theories which have been accepted as proved, 

 and which have largely depended on such observations, are now, 

 in the light of more recent study, being questioned. Notwith- 

 . standing this disadvantage, had it not been for such studies many 

 of the most important facts of medical science would have re- 

 mained undiscovered. Inasmuch as functions cease with life, 

 these observations can only be made upon living animals. Vivi- 

 section, therefore, has been of the greatest benefit to the human 

 race, and those who decry it are daily reaping the results which 

 it has attained, and which could never have been attained with- 

 out it. Wanton and unnecessary experiments are to be condemned, 

 but no terms of praise are too exalted to bestow upon those patient 

 investigators who, through many long years, have laboriously and 

 zealously pursued their studies and experiments, with no other 

 end in view than to add to the sum of human knowledge and to 

 contribute to the relief of human suffering. 



Human Physiology Defined. Human physiology is the 

 science which treats of the human functions. This science, together 

 with anatomy, which treats of structure, and with chemistry, which 

 treats of composition, lies at the foundation of rational medicine. 



