THE DEEPENING OF PHYSIOLOGY. 321 



explanations were in terms of things that required 

 themselves to be explained. 



For this reason, epoch after epoch, one " explana- 

 tion " after another has been, so to speak, " found 

 out," and there has been a recoil of caution or of 

 disgust to the postulate of a specific " vital force," 

 or to some other verbalism cloaking intellectual de- 

 feat. 



To express the life of the organism in terms of its 

 organs is no doubt a useful endeavour, so long as 

 it is not forgotten that the functions of the organs 

 and, what is more, their correlated adaptations re- 

 main a problem. To express the activity of the 

 organs in terms of the activities of their component 

 cells is an even more interesting task useful and 

 necessary like the previous step yet surely in no 

 sense an " explanation " as long as the life of the 

 cell remains an unread riddle. 



To some it has seemed for a brief moment that 

 they saw the whole life of the organism clearly as 

 comparable to an automatic, self-stoking, self-repair- 

 ing heat-engine, or thermo-electric engine, or some 

 unique combination of engines, but the vision has 

 soon been obscured by the shadow of the thought that 

 this marvellous engine grew into obvious complexity 

 in a few days or months from a state of apparent 

 simplicity, that it had the power of adjusting itself 

 to more or less new conditions, and that it actually 

 gave rise to other engines like itself, or that even a 

 fragment of it reproduced the wonderful whole, and 

 then has come the recoil to some subtle or crude 

 theory of vitalism. 



When the physiologist tries to express the func- 

 tion of an organ in terms of the activities of its cells 

 he is really seeking a more thorough description, 



