HI ON THE PHYSICAL BASIS OF LIFE 133 



time, upon the conception of a single physical 

 basis of life underlying all the diversities of vital 

 existence ; but I propose to demonstrate to you 

 that, notwithstanding these apparent difficulties, 

 a threefold unity namely, a unity of power or 

 faculty, a unity of form, and a unity of substantial 

 composition does pervade the whole living world. 



No very abstruse argumentation is needed, in 

 the first place to prove that the powers, or 

 faculties, of all kinds of living matter, diverse as 

 they may be in degree, are substantially similar in 

 kind. 



Goethe has condensed a survey of all powers of 

 mankind into the well-known epigram : 



' ' Warum treibt sich das Volk so und sehreit ? Es will sich 

 ernahren 



Kinder zeugen, und die nahreii so gut es vermag. 



* * 



Weiter bringt es kein Mensch, stell' er sich wie er auch 

 will." 



In physiological language this means, that all 

 the multifarious and complicated activities of man 

 are comprehensible under three categories. Either 

 they are immediately directed towards the main- 

 tenance and development of the body, or they 

 effect transitory changes in the relative positions 

 of parts of the body, or they tend towards the 

 continuance of the species. Even those mani- 

 festations of intellect, of feeling, and of will, which 



