MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 



823 



dysentery amoebiB is smaller, poorer in ch.romatin and commonly peripherally sit- 

 uated ip the cytoplasm. This species also devours red corpuscles in large numbers but 

 the absence of these in intestinal amoebae is not sufficient basis for considering them 

 to belong to the harmless species. The cysts are passed in the faeces; and it is 

 through the ingestion of food or drink, contaminated by encysted amoebae, that in- 

 fection is accoi^plished. If unencysted amoebae are swallowed, they are digested 

 by the acid juices of the stomach, whereas encysted amoebae pass through the stomach 

 unaltered and become active in the alkaline contents of the intestine. The dysentery 

 amoeba is pathogenic to certain lower animals, and kittens have beenlound to l?e most 

 favorable for the experimental production of the disease. Monkeys are also sus- 

 ceptible to a certain extent. 



p-jg jy2. — Entamoeba coli Losch 1875. A-C, various forms of motile amoebae; 

 D the 8-nuclear stage; E-G, cysts with nuclear fragments; B, bursting cyst; 7, 

 young motile amoebae. (After Casagrandi and Barbagalh, from Doflein.) 



Entamteba histolytica may be present in an intestine for months without marked 

 symptoms resulting. It may, however, enter the glands of Lieberkuhn an:d pass 

 through it into the submucosal layer of the intestine. Bacteria accompany these 

 amoebae and they, with the latter, cause an ulcer which spreads through a local 

 destruction of the submucosa and undermines the mucosal layer of the intestine. 

 In severe cases, when the ulcers have spread widely, large areas of the mucosa 

 may be sloughed off. The amoebae lie at the edge of the ulcer and cause it to enlarge 

 bv working their way into sound tissue; once an ulcer is started, it is not impossible 

 that Entamceba coli as well as the dysentery amoebiE may be found in it. The latter 

 live upon the red cells or fragments of intestinal cells. In' chronic cases, the W51II 

 of the intestine becomes greatly, thickened. 



