34 



DISEASES DUE TO PROTOZOA 



cells, a small slough is cast off and an ulcer formed, which then deepens 

 considerably. Bacteria aid the work of ulceration. 



The ulcers are rounded or oval, lying transversely with undermined 

 edges, and may penetrate the muscular and even the peritoneal coat, 

 perforating the same and setting up peritonitis or abscess. In some 

 instances black scars are formed and the ulcer repaired. The blackness 

 is due to the union of hydrogen sulphide from the bowel with iron from 

 the blood. 



Constriction, stenosis and progressive emaciation may ensue. The 

 bowel may become gangrenous. 



A--' 



..Bv 



-A 



Section through wall of large intestine (ul a i.jaaj close under an ulcer caused by Entainceba 

 histolytica. A, amoebce that have penetrated partly in blood-vessels Bv, partly in tissue of 

 submucosa to the muscularis. Magnified. (After Harris.) 



Amoebae may be carried to the spleen and salivary glands, causing 

 abscess. 



Macroscopic. — Cardinal features. 



Body emaciated, abdomen sunken, rigor mortis early, decom- 

 position quickly sets in, the tissues are dry, the large intestine is 

 contracted, thickened, and sometimes gangrenous. 



Perforation and purulent peritonitis. INIesocolon congested and often 

 adherent. The neighbouring glands are enlarged and hyper^emic. 



The colon is adherent externally to the surrounding structures. 



The mucosa is reddened, ulcerated, infiltrated chiefly in cascum, 



