606 AMCEBIC DYSENTERY 



temperature of about 25 C. Although cultures without bacterial 

 growth have not been obtained, means have been devised to 

 ensure that only one species of amoeba is present. For this 

 purpose Musgrave and Clegg select, by means of a low-power 

 objective, an amoeba well separated on the agar plate, place it in 

 the middle of the field, then swing into position a high-power 

 objective, and, having ascertained by means of it that the amoeba 

 is still there, lower the point of the lens on to the agar. By 

 this means the amoeba may have been picked up, and it may 

 then be transferred to a fresh plate. These observers consider 

 suitable bacterial symbiosis to be of great importance in in- 

 creasing the virulence of the amoebae, and probably to play an 

 important part in the pathology of the disease. 



Distribution of the Amoebae. As already stated, they are 

 usually found in large numbers in the contents of the large 

 intestine in tropical amoebic dysentery. They also, however, 

 penetrate into the tissues, where they appear to exert a well- 

 marked action. In this disease the lesions are chiefly in the large 

 intestine, especially in the rectum and at the flexures, though 

 they may also be present in the lower part of the ileum. At 

 first there are seen local swellings on the mucous surface, chiefly 

 due to a sort of inflammatory gelatinous oedema with little 

 leucocytic infiltration ; soon, however, the mucous membrane 

 becomes partially ulcerated, more or less extensive necrosis of 

 the subjacent tissues occurs, and gangrenous sloughs result. The 

 ulcers thus come to have irregular and overhanging margins, and 

 the excavation below is often of wider extent than the aperture 

 in the mucous membrane. The amoebae are found in the mucous 

 membrane when ulcers are being formed, but their most 

 characteristic site is beyond the ulcerated area, where they may 

 be seen penetrating deeply into the submucous and even into 

 the muscular coats. In these positions they may be unattended 

 by any other organisms, and the tissues around them show 

 cedematous swelling and more or less necrotic change without 

 much accompanying cellular reaction beyond a certain amount 

 of swelling and proliferation of the connective tissue cells. This 

 action of the amoeba on the tissues explains the character of 

 the ulcers as just described. These lesions are considered to be 

 characteristic of amoebic dysentery. 



As a complication of this form of dysentery, liver abscesses 

 are of comparatively common occurrence. They are usually 

 single and of large size ; sometimes there are more than one, and 

 occasionally numerous small ones may be present. The contents 

 are usually a thick pinkish fluid of somewhat slimy consistence, 



