724 



PATHOGENIC PROTOZOA 



fingerlike or spinous pseudopodia, and characterized by a nucleus with 

 a large karyosome and a single nucleated resistance cyst in which no 

 multiplication occurs. They have repeatedly been cultivated from hu- 

 man dysenteric stools, from the air, and apparently from liver abscess 

 pus. It has been shown, beyond doubt, that they are harmless to man, 

 and tha't they pass through the intestinal tract with food and water 

 in the cyst form. While they will develop in cultures at body tempera- 

 ture, a better growth is obtained at the temperature of the room. Since 



FIG. 156. ENDAMEBA HISTOLYTICA. Vegetative form showing histolytica type of 

 nucleus. (Army Medical School Collection, Washington, D. C.) 



the true parasitic amebae have never been cultivated on artificial media, 

 the Vahlkampfia may be dismissed with the statement that they are 

 not pathogenic. 



Leidy's genus Endameba includes all parasitic forms, and is char- 

 acterized, among other things, by the absence of a contractile vacuole, 

 which is always present in Ameba and Vahlkampfia. It was proposed 

 for the large ameba parasitic in the cockroach, Endameba blattce, and 

 the genus is a natural one and well established. The species of impor- 

 tance to physicians are Endameba histolytica, Endameba coli and 

 Endameba gingivalis. 



