88-(o"8) PHYSIOLOGICAL SIGNIFICANCE OF VITAL FORCE. 



made. In thus classifying and uniting the manifesta- 

 tions of matter and of life, whether morphological or 

 physiological, under one general cosmic law, their ex- 

 planation is made complete within the limits of the 

 known. 



Phenomena are explained, but the Absolute remains 

 un revealed. The questions still are asked — What is 

 gravity % What are chemical, electrical and vital forces \ 

 What is the essential nature of matter, energy and life % 

 There is no oracle to answer. 



The study of vital phenomena is difficult because of 

 their complex character, and, in the absence of exact 

 analysis, speculative philosophy has for many ages ven- 

 tured different theories in explanation of their nature. 



In seeking to give the present status of physiological 

 science on this important question, it is of interest to take 

 a general historical retrospect, in order that the steps of 

 progress may be observed. 



The atomic philosophy, as taught by Denioeritus and 

 Epicurus, recognized but one kind of matter whose ele- 

 ments, by virtue of their various forms, had the property 

 of diversified and endless combinations. 



This play of atoms, independent of an overruling in- 

 telligence, produced the worlds of inorganic and of or- 

 ganized matter, which move on in endless cycles and are 

 obedient only to physical forces. 



Plato regarded the intelligent soul as of dual charac- 

 ter, one part being mortal, located in the body, and pre- 

 siding over the appetites and passions ; the other part, 

 located in the head, being immortal and the source of 

 reason. 



The nature of the function of the brain and of the ner- 

 vous system was unknown to Aristotle, who thought the 

 soul contained the body, having its mortal part located in 

 the heart. He, as well as Plato, thought the "pneuma" or 

 breath was to cool the blood and in some way act as an 

 instrument of mind over bodily actions. The vital princi- 

 ple of all life forms resides in a germ; "this principle, 

 while it resembles heat, is not fire, but a spirit similar 

 in nature to the sun and stars." 



Hippocrates accepted the Pythagorean doctrine of the 

 four elements, and from it developed his theory of four 

 principal " humors" of the body. He taught the exist- 



