DISTRIBUTION OF THE ENTAMCEB^E 



647 



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 ulcefated, 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 amcebse are found in the mucous 

 membrane when ulcers are being formed, but their most 

 characteristic site is be- 

 yond the ulcerated area, 

 where they may be seen 

 penetrating deeply into 

 the submucous and even 

 into the muscular coats. 

 In these positions they J 

 may be unattended by M 

 any other organisms, and ■ 

 the tissues around them 

 show oedematous swelling 

 and more or less necrotic 

 change, without much ac- 

 companying cellular re- 

 action beyond a certain 

 amount of swelling and 

 proliferation of the con- 

 nective-tissue cells. This 

 action of the amcebse 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, 

 which is largely composed of necrosed and liquefied tissue with 

 admixture of blood in varying amount. In such abscesses 

 associated with dysentery the amcebse are usually to be found, 

 and not infrequently are the only organisms present, no cultures 

 of bacteria being obtainable by the ordinary methods (Fig. 195) 

 They are most numerous at the spreading margin 



Fig. 195. — Section of wall of liver abscess, 

 showing an amoeba of spherical form with 

 vacuolated protoplasm. From a case 

 published by Major 1). G. Marshall, 

 x 1000. 



and this 



