450 BA CTERIOLOG Y. 



tailed studies all strengthen the assumption that the 

 Shiga type of the organism is not the only one concerned 

 in causing epidemic dysentery. In a number of cases 

 of dysentery two, and at times three, types of bacillus 

 dyseuteriae have been encountered. Thus far it has been 

 impossible to differentiate clinically between the infec- 

 tions produced by the one or the other type, both severe 

 and mild cases being caused by each. 



THE SHIGA TYPE OF ORGANISM. The evidence 

 presented by Shiga, who discovered this organism in 

 1898, in Japan, and the subsequent observations of 

 Flexner upon dysentery in the Philippine Islands, 

 leaves little room for doubt that, in so far as acute 

 epidemic dysentery is concerned, the organism under 

 consideration may reasonably be regarded as the causa- 

 tive factor. By both Shiga and Flexner the organism 

 was almost uniformly encountered in the intestinal con- 

 tents, the intestinal walls, and the mesenteric glands 

 during the acute stages of the disease. Later it was 

 frequently missed, and this became more common as the 

 malady progressed to chronicity or recovery. 



It is a bacillus of medium size, with rounded ends. 

 In general its morphology may properly be likened to 

 that of either the typhoid or colon bacillus. 



It is motile and does not form spores. 



It can be stained with any of the ordinary aniline 

 dyes. It is decolorized by the method of Gram. It 

 may be cultivated on all the ordinary media. It grows 

 at room -temperature, but better at the temperature of 

 the body. It does not liquefy gelatin. 



The colonies upon agar-agar present nothing charac- 

 teristic ; those on gelatin are at first /. e., just after iso- 



