700 Dysentery 



sell described a bacillus " Y " from a case of fatal diarrhea in 

 a child. 



Bacillus dysenteriae was also found by Vedder and Duval* 

 in the epidemic and sporadic dysentery of the United States. 

 Duval and Bassettf and Martha WollsteinJ found Bacillus 

 dysenteriae in cases of the summer diarrheas of infants, especi- 

 ally when such diarrheas were epidemic. 



About this time Lentz published an interesting and im- 

 portant paper in which such dysentery and pseudodysentery 

 bacilli as he could secure were found to present differences 

 in their behavior toward sugars. Other observers were care- 

 fully comparing the behavior of the various bacilli by means 

 of the agglutination by artificially prepared immune serum. 

 The outcome of these investigations is the discovery that 

 Bacillus dysenteriae is a species in which there are a number 

 of different varieties well characterized, but by differences 

 too slight to permit them to be regarded as separate species. 

 This thought that we are dealing with a group of varieties 

 and not a single well-defined organism is essential to an 

 intelligent understanding of the bacteriology of dysentery. 



Before taking up the variations, the characters common to 

 all and constituting those of the type species must be 

 described. 



Morphology. The organism is a short rod with rounded 

 ends, generally similar to the typhoid bacilli. It usually 

 occurs singly, but may occur in pairs. It is frequently sub- 

 ject to involutional changes. It is doubtfully motile and is 

 probably without flagella. 



Staining. When stained with methylene-blue the ends 

 color more deeply than the middle; and organisms from 

 old cultures show numerous involution forms and irregu- 

 larities. It stains with ordinary solutions, but not by 

 Gram's method. It has no spores. 



Cultivation. The organism grows well in slightly al- 

 kaline media under aerobic conditions. 



Colonies. The colonies upon gelatin plates are small and 

 dewdrop-like in appearance. Upon microscopic examination 

 they are seen to be regular and of spheric form. By trans- 



* "Journal of Experimental Medicine," vol. vi, No. 2, 1902; "Amer- 

 ican Medicine," 1902. 



t "American Medicine," Sept. 13, 1902, vol. iv, No. n, p. 417. 

 J "Jour. Med. Research," x, p. u, 1904. 

 "Zeitschrift f. Hygiene," etc., 1902, xu. 



