CHAPTER III 



The Behavior of the Bacteriophage in Disease 

 1. variations in the virulence of the bacteriophage 



There is, then, in the intestinal tract of each man, indeed, in that of 

 every animal, vertebrate or invertebrate, a race of the bacteriophage. 

 Unquestionably we can consider this point as established. Experi- 

 ments in vitro have shown us that this bacteriophage has the power to 

 adapt itself to the parasitism of different species of bacteria. Under 

 certain circumstances it can probably adapt itself to any and all species. 

 These two facts being true, the logical question is : What happens when 

 a pathogenic bacterium gains access to the digestive tract of a being 

 which already has within its intestine a bacteriophage protobe to parasi- 

 tize this bacterium? 



We know from common experience that a normal man is sometimes 

 attacked by slight transitory intestinal disturbances; upsets which 

 quickly pass off, without the person becoming really sick. Let us first 

 see what happens within the intestinal tract in cases of this type. 



The following observations were made on the same normal man who 

 was examined periodically throughout a year, providing the data re- 

 ported in the preceding chapter on the uniform presence of a race of 

 the bacteriophage in the intestinal tract. 



During the course of this same year, this individual showed at two 

 different times, July 3, and September 26, slight intestinal disturbances 

 lasting some hours. The first time there was no obvious cause; the 

 second attack followed a suspected meal taken in a village tavern. On 

 each occasion specimens of the stools were examined on the following 

 days. The results are recorded in table 59. 



The results are here so clear-cut that no comment is necessary. 



Additional information is provided by the results of the stool exami- 

 nations of three adult persons, a mother and two daughters, who lived 

 together. Within a period of 15 days, during which time daily exami- 

 nations were being made, one of them, I, without being otherwise dis- 

 turbed, had a few stools of somewhat less than a normal consistency. 

 These occurred on the 17th and 18th of July.* 



* A few cases of dysentery had occurred during the preceding days in the vil- 

 lage where the persons lived. This was, as a matter of fact, the reason for 

 undertaking the systematic examinations. 



437 



