AMOEBIC DYSENTEEY 583 



plasm which contains glycogen and stains brown with 

 iodine. The cyst is uni-nucleate when first formed, this 

 nucleus then divides into two so that the cyst becomes 

 bi-nucleate, and finally each daughter nucleus divides, the 

 cyst becomes quadri-nucleate, and the glycogen vacuole 

 disappears (Plate XXIII, /). The cysts are typically 

 nearly spherical or slightly ovoid, but are not as a rule 

 perfectly symmetrical. The cysts will survive for several 

 weeks outside the body if they be kept moist and cool. 

 Desiccation kills them immediately. Cysts are passed in 

 the faeces in all the nuclear stages. The cysts constitute 

 the " tetragena " phase of Kuenen and Swellengrebel. 

 E. histolytica cannot be artificially cultivated. Many 

 individuals without any signs of dysentery are carriers of 

 E. histolytica. As the parasite lives at the expense of the 

 tissues, Dobell considers that even in these carriers 

 without symptoms a certain amount of ulceration of the 

 colon must be present. Carriers are of two classes, 

 " contact carriers," who have never suffered from amoebic 

 dysentery, and " convalescent carriers," who have 

 recovered from the disease. Cats may be infected by the 

 mouth with the cysts of E. histolytica and a typical 

 dysentery produced. Amoebic dysentery has also been 

 produced in man by feeding with the cysts. Ipecacuanha 

 and its alkaloid emetine have a specific amoebicide action 

 upon the amoebae and their cysts, though the latter are 

 far more resistant than the former. 



As mentioned above, abscess of the liver is not an 

 infrequent sequel of amoebic dysentery. 



The presence of the amoeba in the pus, and especially 

 in the walls, of tropical abscesses is diagnostic. The 

 amoebae are not usually observed in the abscess pus at the 

 time of operation, but make their appearance in the dis- 

 charge about the third day, i.e. when the wall of the 

 abscess-cavity is contracting. In the true tropical abscess 



