878 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



poorer in chromatin and commonly peripherally situated in 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 harm- 

 less species. The cysts are passed in the faeces; and it is through the ingestion of 

 food or drink, contaminated by encysted amoebae, that infection is accomplished. 

 If unencysted amcebae are swallowed, they are digested by the acid juices of the 

 stomach, whereas encysted amcebae 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 been found to be most favorable for the 

 experimental production of the disease. Monkeys are also susceptible to a certain 

 extent. 



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

 symptoms resulting. It may, however, enter one of the glands of Lieberkuhn and 

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

 amcebae and they, with the bacteria, 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 amcebae lie at the edge of the ulcer and cause it to enlarge 

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

 that Entamcsba coli as well as the dysentery amcebae may be found in it. The latter 

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

 of the intestine becomes greatly thickened. 



Ulcers caused by amcebae are almost always situated in the large 

 intestine; consequently, the symptoms of amoebic dysentery are those 

 of inflammation of that part of the body. There is usually abdominal 

 pain, accompanied by the passage of frequent, blood-stained stools with 

 mucus. The infection may, however, be accompanied by no marked 

 symptoms and there may be no diarrhoea. There are usually developed 

 more general symptoms, such as fever and loss of flesh. The onset is 

 frequently very gradual and insidious and the disease runs a chronic 

 course. If amoebic dysentery causes death, it usually does so by per- 

 foration of the bowel with resulting peritonitis, by haemorrhage from 

 the erosion of a blood vessel, or by producing an abscess of the liver. 

 Liver abscesses occur not infrequently in amoebic dysentery. 



Amoebic dysentery is cured with difficulty although emetine, a 

 product isolated from ipecac, has recently been found of great value. 

 Since the encysted amcebae are killed by heat, dysentery can be avoided 

 by eating and drinking only foods and liquids that have been cooked. 



