ox THE VITAL18TIC VIEW OF NATUKK. 



419 



ill the examination of dead embryos in various stages 

 of development, and the idea of the division of labour 

 is one ilowing from the premises of the Darwinian 

 theory — the facts of variability and overcrowding. The 

 second conception, that of " metabolism," touches im- 

 mediately upon the processes of life, and demands; 

 special treatment in the present chapter which deals 

 with biological Thought. 



The conception of a continuous exchange or circulation 

 of matter and of energy in every living organism, and 

 the study of this elementary i\pi(;d form of the living 

 process in the morphological unit of all living or- 

 ganisms, in the cell, seems to have originated with 

 Theodor Schwann,^ and is laid down in his ' ]\Iicro- 3i. 



Scinvaun 



scopical liesearches,' published in 18."! 9. On it is based 

 the whole simplitication and unification of biological 

 thought which distinguishes the second from the first 

 half of our century. The study of the cell — its 



' On the change whieli came 

 over general ]>hysiulogy about 1S40, 

 and the pai-t he himself played, 

 Theodor Schwann has expressed 

 himself in a letter addressed to 

 Du Bois-lleymond, which is given 

 in the notes to the latter's Eloge 

 of Miiller, reprinted in the second 

 volume of his 'Reden,' pp. 143-334. 

 It forms one of the most im- 

 portant historical documents. The 

 Eloge itself should be read together 

 with Claude Bernard's 'liapport,' 

 &c., mentioned above (p. 3S4 n.), 

 which gives the historj- of the great 

 change from a more exclusively 

 Frencli point of view. In the 

 letter mentioned above, from wliicli 

 also the ([uotations given in the 

 text arc taken, Schwann claims 



that the first instance in whicli 

 an "evidently vital phenomenon 

 was submitted to mathematical, 

 numerical" rule, was his measure- 

 ment of the carrying power of 

 a muscle in relation to its con- 

 traction in 1836. The purelj' 

 physical view of vital phenomena 

 exhibited in this example was not 

 adopted by Miiller. nor yet the 

 (juickly following general principle 

 of the cellular theory. Schwann 

 refers to the tliird section of his 

 ' Microscopical Researches,' in 

 which he discards " vitalism," but 

 ailinits in man ("on account of 

 his freedom") an immaterial prin- 

 ciple, and claims that this assump- 

 tion divides him distinctly from the 

 materialists. 



