668 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



Amoeba dysenteries is able to penetrate the mucosal layer of the intestine and to 

 produce dysenteric ulcers, while Amoeba coli is unable to do so. Both amoebae may 

 encyst. The cysts are excreted with the faeces; and it is through the ingestion of food 

 or drink, contaminated by encysted amoebae, that infection with amoebae is acquired. 

 If unencysted amoebae are swallowed, they are digested by the acid juices of the 

 stomach; encysted amoebae pass through the stomach unaltered and become active in 

 the alkaline contents of the intestine. 



Amazba coli and Amoeba dysenteries may be present in an intestine for months with- 

 out harming it. Eventually, an Amosba dysenteries enters one of the glands of Lieber- 

 kiihn and passes through it into the submucosal layer of the intestine. Bacteria accom- 



; \ 



FIG. 117. Amoeba coli. A -C, various forms of free amoebae; D, the 8-nuclear stage; 

 E-G, cysts with nuclear fragments; H, bursting cyst; 7, a young free amoeba. (After 

 Casagrandi and Barbagallo, from Doflein.) 



pany it and they, with the amoebae, cause an ulcer which spreads in the submucosa and 

 undermines the mucosal layer of the intestine. In severe cases, when the ulcers have 

 spread widely, large pieces of the mucosa may be sloughed off; they may be so large as to 

 form complete casts of the intestine. The amoebae lie at the edge of the ulcer and help 

 to spread it by working their way into sound tissue; once an ulcer is started, Amosba 

 coli as well as Amosba dysenteries, may be found in it. The amoebae live upon the red 

 cells or fragments of intestinal cells. In chronic cases, the wall of the intestine becomes 

 greatly thickened. 



Ulcers caused by amoebae are almost always situated in the large 

 intestine; consequently, the symptoms of amoebic dysentery are those 

 of inflammation of that part of the body. There is always abdominal 

 pain, accompanied by the passage of frequent, blood-stained, mucoid 

 stools. There are also, usually, more general symptoms, such as fever 



