OUE LIFE. 45 



in the world of which we have direct and certain 

 cognisance — (" Cogito, ergo sum !; ). Yet this dualism 

 did not prevent him from doing much to advance our 

 knowledge of the mechanical life-processes in detail. 

 Borelli followed (1660) with a reduction of the move- 

 ments of the animal body to purely physical laws, and 

 Sylvius endeavoured, about the same time, to give a 

 purely chemical explanation of the phenomena of 

 digestion and respiration ; the former founded the 

 iatromechanical, the latter the iatrochemical, school of 

 medicine. However, these rational tendencies towards 

 a natural, mechanical explanation of the phenomena 

 of life did not attain to a universal acceptance and 

 application ; in the course of the eighteenth century 

 they fell entirely away before the advance of teleological 

 vitalism. The final disproof of the latter and a 

 return to mechanicism only became possible with the 

 happy growth of the new science of comparative 

 physiology in the 'forties of the present century. 



Our knowledge of the vital functions, like our know- 

 ledge of the structure, of the human body was originally 

 obtained, for the most part, not by direct observation 

 of the human organism itself, but by a study of the 

 more closely-related animals among the vertebrates, 

 especially the mammals. In this sense the very 

 earliest beginning of human anatomy and physiology 

 was " comparative." But the distinct science of 

 " comparative physiology," which embraces the whole 

 sphere of life-phenomena, from the lowest animal up 

 to man, is a triumph of the nineteenth century. Its 

 famous creator was Johannes Muller, of Berlin (born, 

 the son of a shoemaker, at Coblentz, in 1801). For 

 fully twenty-five years — from 1833 to 1858 — this most 

 versatile and most comprehensive biologist of our age 



