454 INFECTION AND IMMUNITY. 



summer isms have been found as the cause of institutional 

 Diarrheas. dy sen tery by Yedder and Duval, of summer diar- 

 rheas of infants by Duval and Bassett, and by Wol- 

 stein. It is the belief of Yedder and Duval that 

 acute dysentery, the world over, "whether sporadic, 

 institutional or epidemic, is caused by the dysen- 

 tery bacillus." We must note, however, that the 

 organism is not found in all cases of clinical dys- 

 entery, even by skilled bacteriologists. "Clinically, 

 24 of our 97 cases in which the dysentery bacilli 

 were found did not differ from the cases of ileocoli- 

 tis in which the dysentery bacilli were not found." 

 (Weaver and others.) It seems certain, neverthe- 

 less, that Bacillus dysenteries is the most impor- 

 tant cause of acute dysentery. It rarely occurs in 

 the stools of healthy individuals. 



The organisms of Shiga and Flexner differ in 

 their actions on the sugars mannite and maltose 

 (i. e., in their acid-forming powers) and in their 

 agglutinability : the "Flexner" type is the stronger 

 acid-former. An artificially produced immune se- 

 rum which is specific for one organism has rather 

 higher agglutinating and bactericidal powers for 

 the corresponding type, but low for the other. In 

 this country the "Flexner" bacillus is much more 

 common than that of "Shiga," but here and abroad 

 both types are met, and sometimes in the same 

 individual. Several other organisms have been 

 cultivated from dysenteric patients, but the varia- 

 tions from these two types are slight. All are 

 certainly very closely related. 



character- The organism is somewhat thicker than the 

 typhoid bacillus, but probably is non-motile, al- 

 though Yedder and Duval, in opposition to others 

 (Lentz), claim to have demonstrated flagella. It 



