442 PATHOGENIC MICROORGANISMS 



dysentery due to a protozoan, the Amreba coli, though presenting much 

 clinical resemblance to the bacillary dysenteries is, nevertheless, an 

 entirely distinct disease. 



Infection takes place, probably, entirely by ingestion of the bacteria 

 with infected water or food contaminated from the feces of dysentery 

 patients. A small epidemic occurring in a hospital in New York City 

 and caused by the bacillus "Y" of Hiss and Russell was indirectly 

 traced to milk by Zinsser. 1 



Endemic in a large part of the world, especially in the warmer 

 climates, the disease most frequently occurs in epidemics of more or 

 less definite localization, usually under conditions which accompany 

 the massing of a large number of human beings in one place, such as 

 those which occur in the crowded quarters of unsanitary towns, in insti- 

 tutions such as insane asylums, or in military camps. The mortality of 

 such epidemics may be very large. According to Shiga, 2 the disease in 

 Japan frequently shows a mortality of over twenty per cent. 



The disease in human beings usually begins as an acute gastro- 

 enteritis which is accompanied by abdominal pain and diarrhea. As 

 it becomes more severe, the colicky pains and diarrhea increase, the 

 stools lose their fecal character, becoming small in quantity and filled 

 with mucus and flakes of blood. There is often severe tenesmus at 

 this stage, and the bacilli are present in large numbers in the dejecta. 

 Owing to the absorption of toxic products, symptoms referable to the 

 nervous system, such as muscular twitching, may supervene, and if the 

 disease is at all prolonged, there are marked inanition and prostration. 



At autopsy in early stages there may be found only a severe catar- 

 rhal inflammation of the mucous membrane of the large intestine. In 

 the later stages there are extensive ulcerations, and the bacteria are 

 histologically found lodged within the depths of the mucosa and sub- 

 mucosa. Occasionally they may penetrate to the mesenteric glands, but 

 as far as we know there is no penetration into the general circulation. 



Poisonous Products of the Dysentery Bacilli. The separate types of 

 dysentery bacilli vary exceedingly in their powers to pro luce toxic 

 substances. Of all the various types which have been described, the 

 strongest poisons have been produced with bacilli of the Shiga-Kruse 

 variety, less regularly active ones with bacilli of the Flexner and of the 

 " Y " type. In fact, investigations carried out with the Shiga bacillus 

 have tended to show that the disease itself is probably a true toxemia, 



1 Zinsser, Proc. N. Y. Path. Soc., 1907. 2 Shiga, Cent. f. Bakt., xxiii, 1898. 



