jelly which may be seen pulsating through the waters of 

 a calm sea, but which drain away to mere films in the 

 hand which raises them out of their element ? Such ob- 

 jections as these must, I think, arise in the mind of every 

 one who ponders, for the first time, upon the conception 

 of a single physical basis of life underlying all the diver- 

 sities 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, di- 

 verse as they may be in degree, are substantially similar 

 in kind. Goethe has condensed a survey of all the pow- 

 ers of mankind into the well-known epigram : 



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



Kinder zeugen, und sie nahren so gut es vermag. 

 * ** ** **** 



Weiter bringt es kein Mensch, stelF er sich, wie er auch will." 



In physiological language this means, that all the multi- 

 farious and complicated activities of man are compre- 

 hensible under three categories. Either they are imme- 

 diately directed towards the maintenance and devel- 

 opment 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 ex- 

 cluded from this classification, inasmuch as to every one 

 but the subject of them, they are known only as transit- 



