148 PARASITIC AMCEB^ OF MAN, 



floor of the ulcer may be rough or smooth, the older 

 ulcers having a smooth floor while in the more recent 

 ones the floor is covered with necrotic material, pus, 

 and blood. In the majority of the ulcers the floor 

 is formed by the submucous coat of the intestine, but 

 in all advanced cases ulcers will be observed in which 

 the floor is formed by the muscular coat of the intes- 

 tine. The smaller ulcers are generally round or oval 

 in shape, but the larger ones are more irregular in 

 shape. The ulcers vary in size from 0.5 cm. to from 

 8 to 10 cm. in diameter. Frequently the entire 

 mucous membrane of a considerable portion of the 

 intestine has been destroyed by the coalescence of two 

 or more large ulcers, and I have repeatedly observed 

 ulcers encircling the bowel and measuring as much 

 as 6 to 8 cm. in the short diameter. 



The mucous membrane between the ulcerations in 

 mild infections may appear normal, but in the more 

 severe types it is always inflamed, thickened, and 

 covered with mucus and pus. The muscular coat of 

 the intestine appears to offer a barrier to the exten- 

 sion of the disease, but this coat may be destroyed and 

 perforation of the intestine may occur. In chronic 

 cases the muscular and submucous coats of the in- 

 testine become greatly thickened and sometimes 

 almost cartilaginous in consistence. 



The exact manner in which the amoebae produce 



