THE BACTERIOPHAGE IN DISEASE 201 



the same species rendered banal as a result of cultivation. How- 

 ever, this individuality is effaced by cultivation, both in the case 

 of the bacteriophage, which, after a few passages at the expense 

 of the bacillus to which it is sensitive may develop activity toward 

 any strain of B. typhosus, and of the typhoid bacillus which is then 

 able to be attacked by any strain of antityphoid bacteriophage. 



Typhoid fever is not a purely intestinal infection as is dysentery. 

 In the latter it can be understood how, when all of the pathogenic 

 bacteria of the intestine or of the mucosa, that is, those in 

 proximity to the ultramicrobes, have been destroyed the disease 

 ends ipso facto. In typhoid fever there is in addition a septicemia 

 and even though the destruction of the bacilli contained in the 

 intestinal contents is sufficient to delay the appearance of the 

 disease or to restrain it from the beginning, it may not be adequate 

 to overcome the infection once the pathogenic bacilli have invaded 

 the organism. 



We will see later that the protective action of the bacteriophage 

 is not limited to the intestine. The intervention of the bac- 

 teriophage, even in the same organism, may manifest itself in 

 different ways. 



In the chapter dealing with the properties of the bacteriophage 

 we have seen that the products which it secretes are possessed 

 of an extremely high opsonizing power. A culture of an antity- 

 phoid bacteriophage is precipitated by the addition of four vol- 

 umes of 96 per cent alcohol. The precipitate is allowed to remain 

 in contact with the alcohol for forty-eight hours, a time adequate 

 to ensure the complete destruction of all of the bacteriophagous 

 germs. One centigram of this moist precipitate is dissolved in ten 

 cubic centimeters of saline. In determining the opsonic index, it will 

 be seen that under the action of the lysin the leucocytes become so 

 loaded with typhoid bacilli that it is impossible to count the num- 

 ber of organisms ingested. The opsonic index is certainly higher 

 than fifty. It is possible that the lysin secreted in the intestine 

 as soon as the bacteriophage has acquired a virulence to dissolve 

 the typhoid bacilli may be resorbed and pass into the circulation, 

 and thus assure the destruction of the bacilli by phagocytosis. 



On the other hand, the bacteriophagous ultramicrobe itself 

 does not remain strictly localized in the intestine; at times it 



