AMOEBINA 453 



harmed. Tejera (1926) reports successful experimental infection in 

 two kittens that were fed on the droppings of cockroaches (sp.?) 

 caught in a kitchen, which contained cysts resembling those of 

 E. histolytica. Frye and Meleney (1936) observed that the cysts 

 passed through the intestine of Periplaneta americana in as early as 

 10-12 hours and remained in the intestine for as long as 72 hours, 

 after feeding on experimental material. Cysts which stayed in the 

 cockroach intestine for 48 hours gave good cultures of trophozoites 

 in egg-horse-serum-Ringer medium. 



'0 







S 6 8 9 



Fig. 192. Entamoeba coli, X1150 (Kudo). 1, a living amoeba; 2-5, 

 stained trophozoites; 3, an amoeba infected by Sphaerita; 6, a precystic 

 amoeba; 7, a fresh cyst; 8, a stained young cyst with a large glycogen 

 vacuole; 9, a stained mature cyst. 



In addition to E. histolytica, there are now known four other 

 intestinal amoebae living in man. They are E. coli, Endolimax nana, 

 Iodamoeba biitschlii and Dientamoeba fragilis. In Table 10 are given 

 the characteristics necessary for distinguishing E. histolytica from 

 the other four intestinal amoebae. 



E. coli (Grassi) (Fig. 192). The trophozoite measures 15^0/* in 

 diameter; average individuals 20-35/x; cytoplasm not well differenti- 

 ated; movement sluggish; endoplasm granulated, contains micro- 

 organisms and faecal debris of various sizes in food vacuoles; erythro- 

 cytes are not ingested, though in a few cases (Tyzzer and Geiman) 



