336 SPECIFIC MICRO-ORGANISMS 



in the U. S. army have been remarkably good, rivaling those 

 obtained with the use of vaccinia in the prevention of small-pox. 



Bacillus (Bacterium) Dysenteriae. Shiga in 1898 isolated 

 this organism from the feces of patients suffering from dysentery, 

 showed that it is agglutinated by the blood of dysenteric patients 

 in high dilutions and not by normal human blood. 



B. dysenteries is about o.6/x in width by 2 to 4/4 in length, usually 

 single and non-motile. It stains readily and is Gram-negative. 

 Involution forms are common in older cultures. The organism 

 grows readily on ordinary media and its cultures resemble those 

 of B. typhosus very closely. Gelatin is not liquefied; no indol is 

 produced in pep ton solution; no gas is formed from any of the 

 sugars; milk is rendered slightly acid and then alkaline without 

 coagulation. It differs from the typhoid bacillus in failing to 

 ferment mannite and maltose. 



When cultures are injected intravenously into rabbits severe 

 diarrhea is produced, which may be bloody. The animal usually 

 dies in a few days, and if it recovers often exhibits paralysis of 

 the hind legs. Similar results are obtained by the injection of 

 dead bacilli, indicating that the effect is toxic rather than infec- 

 tious. Kittens and puppies have been infected by introducing 

 dysentery bacilli into the stomach, resulting in diarrhea with the 

 intestinal lesions of dysentery. The toxins seem to be intimately 

 bound up in the cells in young cultures, but readily set free into 

 solution after the bacilli are killed. Culture filtrates, of which 

 0.02 c.c. suffices to kill a rabbit in 24 hours, have been obtained. 



Acute epidemic dysentery is the disease in which this organism 

 is found. The infectious agent is found on the membrane of the 

 large intestine, which is diffusely inflamed, often covered with a 

 fibrinous exudate, or by a pseudo-membrane. Later numerous 

 ulcers may be found. The bacilli are only very rarely found in 

 the blood or internal organs. The blood of the patient aggluti- 

 nates the bacillus of Shiga in dilutions of i to 50 or i to 100. The 

 mortality is about 25 per cent, but variable in different epidemics. 



Horses have been immunized with cultures of B. dysenteric and 



