No. 498] 



PHYSIOLOGY 



399 



were physical phenomena, to the other, chemical phe- 

 nomena. Their gaze was in the right direction, and each 

 believed that he saw a great light. But like the whole 

 world of science of their time, they knew too little of the 

 true physics and chemistry, and their interpretations of 

 organic processes, while containing a considerable modi- 

 cum of truth, teemed with unwarranted hypothesis. It 

 was not strange, therefore, that the iatro-movement was 

 short-lived. Its influence, however, was not without 

 value, for as the knowledge of physiological fact increased 

 through experiment, and the world became accustomed to 

 mechanical notions, the authority of the spirits became 

 weakened, and gradually, very gradually, they ceased to 

 be a factor in physiological reasoning. In popular 

 speech, however, they persist even to our own day; for, 

 as our moods change, we are in good spirits or bad 

 spirits, full of spirit or lacking in spirit, high-spirited or 

 low-spirited— phrases which stand as witnesses of a once 

 powerful, but now discarded, physiological doctrine. 



As the spirits became deposed, scientific thinkers, dis- 

 satisfied with the mechanism of the time, still groped for 

 something to take their place. There were spontaneous 

 uprisings of such agencies as Van Helmont's archeus, 

 StahPs anima, Boerhaave's principium nervosum and 

 Hoffmann's ether. None of these long survived, and 

 soon after the middle of the eighteenth century they were 

 definitely replaced and the wide-spread desire for a unify- 

 ing principle was for the time set at rest by the 

 hypothesis of vital force. All physiologists had now 

 come to realize that many of the chemical and physical 

 phenomena of inorganic nature were to be observed also 

 in living bodies. But they knew that the chemical com- 

 position of the latter differed from that of the former, 

 and for the manufacture of the vital substance and for 

 many of its actions they could find no parallel outside 

 of living bodies. Most of them succumbed to the com- 

 pelling power of their ignorance and acquiesced in the 

 assumption that a peculiar principle resides in living 



