1 22 LAY SERMONS, ADDRESSES, AND REVIEWS. [vn. 



girl wears in her hair and the blood which courses 

 through her youthful veins ; or, what is there in common 

 between the dense and resisting mass of the oak, or the 

 strong fabric of the tortoise, and those broad disks of 

 glassy 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 objections 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 under- 

 lying 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 the powers of 

 mankind into the well-known epigram : — 



" YVarum treibt sicli das Yolk so imd schreit % Es will sicli ernahren 

 Kinder zeugen, imd die naliren so gut es verniag. 

 * * # * * 



"Weiter bringt es kein. Mensch, stell' er sicli 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 deve- 

 lopment 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 wq 



