ON THE VITALISTIC VIEW OF NATURE. 419 



in the examination of dead embryos in various stages 

 of development, and the idea of the division of labour 

 is one flowing 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 typical form of the living 

 process in the morphological unit of all living or- 

 ganisms, in the cell, seems to have originated with 

 Theodor Schwann, 1 and is laid down in his ' Micro- 

 scopical Researches,' published in 1839. On it is based 

 the whole simplification and unification of biological 

 thought which distinguishes the second from the first 

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



31. 

 Schwann 



1 On the change which came 

 over general physiology about 1840, 

 and the part he himself played, 

 Theodor Schwann has expressed 

 himself in a letter addressed to 

 Du Bois-Reymond, 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 portant historical documents.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 'Rapport,' 

 &c., mentioned above (p. 384 n.), 

 which gives the history of the great 

 change from a more exclusively i 

 French point of view. In the 

 letter mentioned above, from which ' 

 also the quotations given in the > 

 text are taken, Schwann claims i 



that the first instance in which 

 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 purely 

 physical view of vital phenomena 

 exhibited in this example was not 

 adopted by Miiller, nor yet the 

 quickly following general principle 

 of the cellular theory. Schwann 

 refers to the third section of his 

 ' Microscopical Researches,' in 

 which he discards "vitalism," but 

 admits in man ("on account of 

 his freedom") an immaterial prin- 

 ciple, and claims that this assump- 

 tion divides him distinctly from the 

 materialists. 



