56 The Science of Life. 



The earlier physiologists concerned themselves almost 

 wholly with the functions of man and mammals; and 

 Physiology even now t ^ ie physiology of the lower ani- 

 becomes mals lags far behind, and that of plants still 



Comparative. furthen It was m the handg Q f Johannes 



Miiller (1801-1858) that comparative physiology fairly 

 began. A genius beyond doubt, and with the widest of 

 interests, he was especially distinguished by the ease 

 with which he turned from one method to another in 

 seeking to solve a problem. Now he would appeal to 

 physics and again to psychology, here he sought the 

 chemist's aid and there the embryologist's; he tried all 

 methods to gain his end. In showing how animals of 

 high and low degree shed light upon one another, he 

 founded comparative physiology, and gave a new dig- 

 nity to zoology. 



One is somewhat ashamed to speak of the advance of 

 comparative physiology, for so little has been securely 

 Advance of achieved. It is only in contrast to the ignor- 

 Comparative ance of the subject in pre-Darwinian days 

 Physiology. that what has been done m the Victorian era 



appears great. 



There are various reasons why comparative physio- 

 logy lags so far behind comparative anatomy. There 

 are the intrinsic difficulties of the subject, for the lower 

 we descend in the animal kingdom the more baffling is 

 the study of function, morphological simplicity implying 

 physiological complexity. As Prof. Foster has said: 

 "Physiology is, in its broad meaning, the unravelling 

 of the potentialities of things in the condition which we 

 call living. In the higher animals the evolution by dif- 

 ferentiation has brought these potentialities, so to speak, 

 near the surface, or even laid them bare as actual pro- 

 perties capable of being grasped. In the lower animals 

 they still lie deep buried in primeval sameness; and we 

 may grope among them in vain unless we have a clue 

 furnished by the study of the higher animal." The 

 history of the science shows a passage from man to 

 animal, from higher animal to lower animal, and, most 

 tardily of all, from animal to plant. 



Another difficulty is consequent on specialization. The 



