CHAPTER III 



CHEMICAL AND PHYSICAL METHODS— 



LIMITATIONS— RESULTS ACQUIRED— THEIR 



ROLE IN IMMUNITY AND BACTERIOLOGY 



The difficulties which we have enumerated are important only 

 when we seek to understand the intimate mechanisms of 

 fundamental biological phenomena, the 'irreducible principle' 

 of Claude Bernard. The objection based on the evolution of 

 the notion of determinism is purely theoretical, and in no way 

 changes the results of our experiments. Whenever we try to 

 superimpose an example borrowed from an inert body on to a 

 series of chemical phenomena taking place in an organism, we 

 observe that there is no absolute accord, even though the point 

 of departure and the point of arrival are identical. Usually 

 we are not aware of this discrepancy, as we cannot know the 

 real intermediary stages, but only those which we have our- 

 selves realized. This brings us back to Plato's picture of the 

 cave, in which our senses perceive only the shadows projected 

 on the background. If our problem consists in the exact 

 analysis of the means employed by nature to obtain a certain 

 result, the chances are that our rough methods will fail, until 

 the far-off day when some kind of electronic chemistry wiU 

 be perfected. Even then we will succeed only if there is no 

 other point of divergence, which is not very likely. 



But our ordinary chemistry can render great services if we 

 concern ourselves chiefly with the points of departure and 

 arrival. If, for instance, we manage artificially to obtain sub- 

 stances identical with — or sufficiently similar to — those which 

 determine pathological disturbances, by an excess or deficiency 

 in the organism, we will have truly progressed. We will thus 

 be able to neutralize them if they are too abundant, and to 

 replace them by purified and concentrated or even synthetic 

 products if they are deficient. 



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