ON THE PHYSICAL BASIS OF LIFE 97 



lying all the diversities of vital existence ; but I propose 

 to demonstrate to you that, notwithstanding these ap- 

 parent difficulties, a threefold unity namely, a unitv 

 of power or faculty, a unity of form, and a unity of 

 substantial composition does pervade the whole liv- 

 ing 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 man- 

 kind into the well-known epigram : 



"Warum treibt sich das Volk so und schreit? Es will sich ernahren 

 Kinder zeugen, und die nahren 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 maintenance 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 manifestations of intellect, of feeling, and 

 of will, which we rightly name the higher faculties, are 

 not excluded from this classification, inasmuch as to 

 every one but the subject of them, they are known only 

 as transitory changes in the relative positions of parts 

 of the body. Speech, gesture, and every other form of 

 human action are, in the long run, resolvable into mus- 

 cular contraction, and muscular contraction is but a 

 transitory change in the relative positions of the parts 

 of a muscle. But the scheme which is large enough to 



