ON THE VITALISTIC VIEW OF NATURE. 397 



apply strict experimental research, combined with actual 

 measurements, to pliysical, organic, and psychical pheno- 

 mena, which had so far escaped all exact treatment ; 

 and from Berlin, where in the person, and still more in 

 the school, of Johannes iMiiller, the great and complex i9. 



_ Johannes 



phenomenon of life in the higher organisms was analysed muirt. 

 into various mechanical and physical processes, each 

 connected with some well-defined organ which was more 

 and more recognised as possessing tlie properties of a 

 physical apparatus. A great deal of the work of the 

 numerous members of this school consisted in unravel- 

 ling with the microscope the structure of sucli organic 

 apparatus, and studying its action by physical measure- 

 ments and experiments. As examples and models of 

 this kind of work we have Du Bois-Reymond's 'Re- 

 searches in Animal Electricity' (1848), and Helmholtz's 

 'Physiological Optics ' (1867, second edition, much en- 

 larged, 1896), and 'Physiological Acoustics' (1862). 

 In the course of these labours it was found that the 

 older ideas of " Stoti'wechsel," and the conception of 

 the circulation of matter as it was taught in the school 

 of Liebig, required to be corrected and extended. I have 

 referred in an earlier chapter ^ to the interesting circum- 

 stances under which our modern notions of the conserva- 

 tion of energy first dawned independently upon Mayer 

 and Helmlioltz whilst studying the phenomena of heat 

 in the animal organism. In the school of Liebig we 

 meet with an occasional attempt to extend the idea 

 of " Stofiwechsel," the exchange of material or of 

 elementary matter in the living body of animals and 



' See supra, ch.ip. vii. 



