14 GENERAL PHYSIOLOGY 



development of physiology. Bacon's monistic philosophy, which, 

 because of its vigorous accentuation of the inductive method oi 

 investigation, has become the basis of all modern natural science, 

 inaugurated the great series of new and exact physiological ob- 

 servations, founded upon experiment, which has continued from 

 that time to enrich our knowledge of vital phenomena. The 

 philosophy of Descartes, although purely dualistic, was full of 

 importance for the physiology of the senses and the theory of 

 knowledge, because of the theory of sense-perception which formed 

 its starting-point. Descartes was the first to maintain the pro- 

 position that the only thing in the universe of which we have 

 certain knowledge is subjective psychical sensation. Mind, sensa- 

 tion, thought, is the only fixed point from which the universe can 

 be surveyed and discovery proceed. " Cogito, ergo sum!' Sense- 

 perception, therefore, gives us no information concerning things, 

 for it is deceptive ; and things, i.e., bodies, are in reality wholly 

 different from what they appear through our sense-organs to be. 

 These jaropositions are capable of the widest application. Further, 

 they are so well grounded and so precisely and clearly expressed, 

 and give so admirable a basis for a philosophical system, that one 

 must wonder how it is possible for Descartes, who was usually a 

 •clear and consistent thinker, to be so inconsistent as to arrive 

 finally at the complete dualism of body and mind. It is a tempta- 

 tion to believe that he maintained ultimate consistency secretly : 

 but that, for practical reasons, he allowed the pressure of the 

 ecclesiastical conditions of his time to give this unexpected turn 

 to his philosophy, while content with the feeling that the un- 

 predjudiced thinker would note and correct the evident incongruity. 

 Of the greatest physiological importance, however, is his clear dis- 

 cernment in his dualism that the bodies of animals and men 

 act wholly like machines and move in accordance with purely 

 mechanical laws. But here again dualism comes in as a disturbing 

 ■element, for Descartes ascribes the impulse to all movement to the 

 soul, which, from its seat in the only unpaired organ of the brain, 

 the pituitary gland, controls the individual parts of the body. 

 Nevertheless, the general physiological ideas of Descartes have 

 been of great value to physiology, and the gifted thinker also 

 made many very important special phj'siological observations, 

 which markedly advanced o\ir knowledge of physiological optics 

 and acoustics. 



Descartes' notion that, as regards its vital activities, the human 

 body is to be regarded as a complicated machine, was especially 

 fruitful for physiology in the ingenious application which Borelli 

 {1608-1679) made of it in the science of animal movement. 

 Borelli undertook for the first time to reduce the movements of 

 the organic motor apparatus to purely physical principles, and 

 thus laid the foundation of our present mechanics of animal motion. 



