PHYSIOLOGICAL SIGNIFICANCE OF VITAL FORCE. 761 



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 nervous 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 prin- 

 ciple of all life-forms resides in a germ ; " this principle, while it resem- 

 bles heat, is not fire, but a spirit similar in nature to the sun and stars." 



Hippocrates accepted the Pythagorean doctrine of the four ele- 

 ments, and from it developed his theory of four principal " humors " 

 of the body. He taught the existence of an " intermediate nature," 

 which, though distinct from the mortal soul or pneuma, was the source 

 of vital activity. 



The pneuma was deemed such an important factor in the expla- 

 nation of vital phenomena, that a school called " Pneumatists " was 

 founded in the first century of our era. It was not then known that 

 the arteries contained blood, but they were regarded as the channels 

 through which the pneuma passed throughout the body ; and this 

 pneuma was to Galen, a. d. 130, identical with the soul. For fourteen 

 hundred years " pneumatism," under varied forms, was the accepted 

 philosophic belief of the civilized world, and only in the latter part of 

 the sixteenth century did anatomical study enable Sylvius, Fallopius, 

 Fabricius, and Harvey, to modify the prevailing belief of bodily func- 

 tions. Then it was that Paracelsus sought to explain vital phenomena 

 through the agency of an " archaeus " or demon, which, he affirmed, 

 was located in the stomach, and presided over the processes of nutri- 

 tion, separating the useful from the j)oisonous part of the food. 



Van Helmont adopted the idea of an archseus, but thought it an 

 immaterial though personal force or entity, which " presided over all 

 bodily functions " and gave to each member of the body its own spe- 

 cial " vital spirit." The consensus of all these vital spirits produced 

 health, and their disagreement disease. 



Van Helmont " discovered gaseous substances and identified the 

 archreus itself with gas." He proclaimed the existence of a general 

 bond of sympathy throughout the universe, because of the " vital spir- 

 its " which resided in all forms of matter. 



Descartes regarded the body simply as a complex machine, acting 

 under conditions of physical forces, and all the phenomena of life were 

 but the products of their working. The soul, however, was a hihger 

 and independent principle which, located in the pineal gland, made 

 itself known by thought, and took its temporary abode in the body, 

 simply as a spectator of vital functions. 



Leibnitz, while admitting a harmony established by Divine power, 

 denied to soul and body any reciprocal influence, saying : " The body 

 goes on in its development mechanically, and the laws of mechanics 



