AMEBiE OF THE MOUTH 



141 



endoplasm pouring out into it later. The reproduction of these 

 Httle animals is by a simple division of the body into two when 

 they have grown large enough to feel cumbersome as single 

 individuals. Although cysts are formed for protection against 



Fig. 41. Common shapes of Endamaeba gingivalis, from human mouth. 



(After Bass and Johns.) 



X650. 



an unfavorable environment, no multiplication within the cysts 

 has been observed such as occurs in Endamceba coli or E. 

 histolytica. The cysts, which are rarely found, usually measure 

 from eight to ten ^u (^^Vf to ^^Vo of an inch) in diameter, and are 

 perfectly spherical with a thin wall. 



Some investigators have suggested the possible identity of 

 E. gingivalis and E. histolytica, but, as pointed out by Craig, 

 the sluggish movements, small nucleus, absence of certain changes 

 in form of the nucleus observed in the dysentery ameba, formation 

 of cysts with a single nucleus, inability to produce dysentery 

 when swallowed and other characteristics all indicate that 

 without doubt the mouth ameba is quite distinct from the in- 

 testinal amebae. 



Other species besides E. gingivalis have been found in the 

 human mouth, but little is known about them. E. kartulisi is 

 large with very distinct ectoplasm; it is said to occur only 

 rarely. Recently Craig has described another ameba of small 

 size, which he has provisionally named E. confusa on account of 

 the likelihood of confusing it with small specimens of E. gingivalis. 



