AMOEBINA 363 



Nothing is known about its life-cycle in the human intestine. 

 Cultivation of cysts in vitro indicates, according to Dobell (1938), 

 the following changes : The cyst content usually emerges as a single 

 multinucleate amoeba through a large opening in the cyst wall. 

 Prior to or during the emergence, the amoeba may divide. Normal 

 mature cysts ''frequently lose" 1-4 of their original 8 nuclei before 

 germination, thus becoming "infranucleate" (with 4-7 nuclei). Un- 

 like in E. histolytica, there is no nuclear division in the metacystic 

 stages. By a series of binary divisions with random nuclear distribu- 



m.' 



:^ 





.o^ 







Fig. 170. Entamoeba gingivalis, X1150 (Kudo). 1, 2, living amoebae; 

 3-7 stained amoebae. 



tion, uninucleate amoebulae are finally produced. These are young 

 amoebae which develop into large trophozoites. Here also, there is 

 no sexual phenomenon in the life-cycle. 



E. gingivalis (Gros) (E. buccalis Prowazek) (Fig. 170). This 

 amoeba lives in carious teeth, in tartar and debris accumulated 

 around the roots of teeth, and in abscesses of gums, tonsils, etc. The 

 trophozoite is as active as that of E. histolytica; 8-30^ (average 

 10-20/x) in diameter; cytoplasm well differentiated; monopodial 

 progressive movement in some individuals; endoplasm hyaline, but 

 vacuolated, and contains ordinarily a large number of pale greenish 

 bodies (which are probably nuclei of leucocytes, pus cells or other 

 degenerating host cells) and bacteria in food vacuoles; nucleus, 2-4/x 

 in diameter, appears as a ring ; when stained it shows a small central 

 endosome and small peripheral chromatin granules closely attached 

 to the membrane. Stabler (1940) observed 5 chromosomes during 



