CHAPTER III 



THE ACTIVITIES OF THE ORGANISM 



THE rather lengthy discussion of the last chapter was 

 necessary in order to show just how far the principles 

 of energetics established by the physicists applied to 

 the organism. We have seen that the first law of 

 thermodynamics does so apply with all its exclusive- 

 ness. The more carefully a physiological experiment 

 is made ; the more closely do its results correspond 

 with those which theory demands. It is true that 

 relatively few experimental investigations can be 

 controlled in this way, but in those that can be checked 

 by calculation (as, for instance, in the well-known 

 calorimetric experiments) everything tends to show 

 that precisely the same quantities of matter and 

 energy enter the body of an organism in the form of 

 food-stuff, that leave it as radiated and conducted 

 heat, as work done, and as the potential chemical 

 energy of the excretions. Even when we are unable 

 (as in most investigations) to apply the test of corre- 

 spondence with theory, we have the conviction that the 

 law of conservation holds with all its strictness. 



Then, whenever it was possible to apply the 

 methods of chemistry and physics to the study of the 

 organism, it was seen that the processes at work were 

 chemical and physical. The substance of the living 

 body was seen to consist of a large (though limited) 

 number of chemical compounds, differing mainly 



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