134 AMEB^ 



only the parasites in the encysted stage, with an enclosing capsule 

 to protect them from being digested, can reach the intestine and 

 cause disease. 



The Disease. — In the experiments made by Walker and 

 Sellards in feeding ameba-inf ected material to animals and human 

 volunteers, dysentery symptoms appeared in from 20 to 94 days, 

 averaging about two months. The most marked symptom is 

 an acute diarrhea in which the stools consist largely of blood and 

 mucus. In a typical case from Alabama a patient passed as 

 many as fifteen or twenty stools in an hour. This condition 

 had been going on for years, recurring about three or four times 

 a year, lasting a month at a time. In the intervals between 

 these attacks the symptoms were mild and the patient passed 

 only two or three stools a day. Sometimes the attacks are more 

 regularly chronic, or may recur at long intervals. Often the 

 dysentery is accompanied by evening fever and anemia from 

 loss of blood in the bowels. 



Instead of producing ulcers on the mucous surface of the large 

 intestine such as occur in bacillary dysentery, the amebse work 

 deeper into the muscular linings of the intestines. Xiocal swellings 

 first appear, followed by an ulceration of the mucous membrane. 

 This produces a portal for the entrance of the amebse to the 

 tissue underlying the mucous membrane, and here they make 

 extensive excavations. The lesions are most common in the 

 upper half of the large intestine but can be found from the lower 

 part of the small intestine to the rectum. The exposed ulcera- 

 tions vary from the size of a pinhead to that of a silver dollar, 

 their ragged edges tending to roll into the crater-hke areas. 

 Often the tunnel-like excavations under the mucous membrane 

 connect with one other. 



Liver abscess is a common result of infection with Endamceba 

 histolytica. Often these abscesses are of large size, filled with 

 a slimy and somewhat bloody chocolate-colored pus. Over a 

 quart of such pus has been removed from an amebic liver abscess. 

 The parasites are found at the edges of the abscess, eroding more 

 tissue and enlarging the pus cavity. How they reach the liver 

 to do their damage is not certainly known, but it seems probable 

 that they bore into bloodvessels in the walls of the diseased large 

 intestine and are carried by the portal vein to the Uver, where 

 they find a fertile feeding ground. 



