178 BACTERIA 



death. Mortality is from 2 percent to 15 percent. The post- 

 mortem findings are not specific. There may be evidence of an 

 enteritis with swollen lymph follicles, and an enlarged spleen. 



Agglutination. The blood of infected individuals may agglu- 

 tinate bacilli. A dilution of such blood with 8, ooo parts of water 

 has produced the reaction. 



No anti-serum or bacterin treatment is as yet possible. 



DYSENTERY BACILLUS 



Bacterium Dysenteriae. 



Dysentery Bacillus. 



The cause of one form of tropical dysentery. The group to 

 which this belongs comprises many closely related varieties some 

 of which are thought to be the cause of infant diarrhoea in this 

 country. There are numerous varieties of this organism, the 

 differentiation of which depend upon their chemical activities, 

 fermentation of various carbohydrates being the most important, 

 and agglutinative properties with different sera. The tropi- 

 cal form of dysentery is due to the type orginally described by 

 Shiga; this type is uncommon in temperate zones, the Flexner 

 variety being much more common. The Shiga variety is much 

 the more virulent. 



Morphology and Stains. The organism is, in many respects, 

 similiar to the typhoid bacillus, but is plumper. It is non-motile, 

 has no spores, and exhibits pleomorphism. It stains well with 

 the common aniline dyes, but not by Gram's method. 



Vital Properties. It is killed by i percent carbolic solution 

 in thirty minutes. Lives for twelve to seventeen days when 

 dried. Direct sunlight kills it in thirty minutes. Its thermal 

 death -point is 58C. in thirty minutes. It is a facultative aerobe; 

 grows at ordinary temperature, but better at 37C. 



Cultures. Grows on all the common culture media, but more 

 slowly than the colon bacilli. Gelatine cultures resemble typhoid. 

 The growth in this media (which it does not liquefy) produces no 



