130 THE ACUTE SELF-LIMITED INFECTIONS 



disease, its chief lesion being a violent inflammation 

 of the lining of the large intestines. The disease is 

 caused by the Bacillus dysenteries or dysentery bacillus. 

 It is, however, better to say that a group of organisms 

 under this name gives rise to it because there are many 

 varieties with different chemical and serum reactions, 

 producing attacks of varying severity. Their general 

 pathogenic and etiological effects may be discussed 

 together, however. 



In cholera the chief lesions are in the lower small 

 intestine, but otherwise the two diseases have many 

 things in common. 



The bacilli enter probably only by the mouth in 

 infected food and drink, and pass through the ali- 

 mentary tract to their organ of predilection, the 

 colon. Here they penetrate the mucous lining to its 

 deeper layers, causing violent irritation. They may 

 get deeper into the wall or even to the glands draining 

 the colon, but not into the blood. The inflammation 

 gives rise to diarrhea which passes 'from feculent to 

 mucous, to bloody mucous, and may be almost wholly 

 blood. These effects are due to the effort of the 

 colonic wall to rid itself of the poisons, and the body 

 seems to choose this method to free itself of the 

 intruder. This fact is further shown when we inject 

 susceptible small animals with the poisons, for a con- 

 gestion of the colon with diarrhea results, although no 

 living organisms are present. The poisons of the dysen- 

 tery bacilli are probably both extracellular and endo- 

 toxins, the latter being more abundant. The toxic 

 effect, therefore is exerted by the existence of the 

 germs in the mucous membrane giving off poisonous 



