164 THE ENZYME THEORY OF DISEASE [CH. xi 



with this organism. The strain from the lung possessed the 

 property of causing, when inoculated into another rabbit, an 

 inflammatory oedema of the skin ; the strain from the spinal 

 fluid failed to do so. The strain from the lung, however, when 

 grown anaerobically was deprived of its power to cause this 

 inflammatory oedema of the skin. 



(c) Growth in a certain vehicle may alter the fermenting 

 powers of one organism and the pathogenic powers of another. 

 The fermentation properties of a strain of B. coli isolated from 

 cowdung become altered after growth in milk. A milk-borne 

 epidemic of scarlet fever is not infrequently characterised by 

 the partial or complete absence of the usual rash. 



(d) An analogy may also be traced between the action of 

 chemical substances added to culture media and the effects 

 of drugs administered in disease. For example, the presence 

 of sodium benzoate inhibits the power of B. coli to produce 

 gas from dextrose one of the most stable and fundamental 

 differences separating B. coli from the typhoid-dysentery 

 group without in any way affecting its other fermenting 

 reactions. The administration of sodium salicylate in rheu- 

 matic fever eliminates the symptoms of pain and fever 

 the two most characteristic symptoms of this disease with- 

 out apparently affecting any other of its symptoms and 

 lesions in a great many cases. 



14. If the foregoing considerations suggest that the 

 symptoms of disease are due to zymotic action they likewise 

 imply that each separate symptom is attributable to the 

 activity of a distinct enzyme. Such a conclusion postulates 

 the existence of innumerable pathogenic enzymes each one 

 concerned in the causation of some particular symptom of 

 disease, and requires us to conceive of different groups or 

 combinations of enzymes associated with different pathogenic 

 organisms and responsible in the case of each organism for the 

 train of symptoms that follow its invasion of the living 

 tissues. 



Analogy with the sugar-fermenting properties of bacteria 

 renders such a complex picture of the causation of disease 

 less fanciful than, at first sight, it appears. As we have shown 



