CH. xi] THE ENZYME THEORY OF DISEASE 163 



be sufficiently acute to cause death and other symptoms and 

 lesions follow which result in the death of the animal in a few 

 days. He discovered that the particular constituent of the 

 toxin responsible for this bronchial spasm could be removed 

 altogether from a suspension of the organism by the addition 

 of blood charcoal, so that the subsequent injection of the 

 filtered fluid failed to cause the bronchial spasm, although it 

 still produced the other symptoms and lesions and led to a 

 fatal termination in a few days. He, likewise, discovered that 

 the same constituent of the toxin could like the sugar- 

 splitting ferment of the yeast cell and the urea-splitting 

 ferment of M. ureae be extracted with ether and, further, 

 that if a normal saline solution, to which this ethereal extract 

 had been added, were injected into an animal, the typical 

 bronchial spasm was developed in the complete absence of 

 the organism itself. 



The force of this analogy is somewhat weakened by the 

 knowledge that this acute bronchial spasm is by no means 

 pathognomic of the pneumococcus, many poisons producing 

 the same result on injection into an animal. The analogy is, 

 however, suggestive. 



13. The dissociation brought about artificially in the 

 laboratory by this investigator may be observed to take 

 place naturally in response to certain kinds of environment. 

 Thus, a strain of pathogenic bacteria may lose its power to 

 produce a certain lesion or to cause a certain symptom in the 

 body. Further, the conditions which appear to deprive it of 

 such functions are comparable to those which, we have seen, 

 influence ferment activity. A few examples will suffice. 



(a) The quality of light to which a culture of bacteria is 

 exposed may modify their power to produce pigment. Ex- 

 posure to the ultra-violet rays is found to alter profoundly 

 the lesions and symptoms caused by B. anthracis (Henri, 

 1914). 



(b) The presence or absence of oxygen influences pigment 

 production and the fermentation of sugars by bacteria. Foa 

 ^1890) isolated strains of pneumococci from the lung and from 

 the spinal fluid of a rabbit which had died after inoculation 



112 



