ILLUSTEATIONS (*). VITA.L FORCES. 389 



strives, from time to time, with varying success, to break 

 through those ancient forms and symbols invented to 

 subject rebellious matter to rules of mechanical construc- 

 tion." 



Further in the same work,* I have said, " It must, how- 

 ever, be remembered, that the inorganic crust of the earth 

 contains within it the same elements that enter into the 

 structure of animal and vegetable organs. A physical cosmo- 

 graphy would therefore be incomplete, if it were to omit a 

 consideration of these forces, and of the substances which 

 enter into solid and fluid combinations in organic tissues, under 

 conditions which, from our ignorance of their actual nature, 

 we designate by the vague term of vital forces, and group 

 into various systems, in accordance with more or less per- 

 fectly conceived analogies."! 



* Vol. i. p. 349. (Bohn's Edition.) 



+ Compare also the critique on the acceptation of special vital forces 

 in Schleidcn's Botanik als inductive Wissenschafi, part i. pp. 60, and 

 the lately published and admirable treatise of Emil du Bois-Reymoud, 

 Untorsucliungen vher thierische Elektricitat, vol. i. pp. xxxiv L 



