ENTAMCEBA GINGIVALIS 223 



of those of E. histolytica. They are clear, and appear to consist of ecto- 

 plasm alone when this layer is sharply defined. Jepps, as well as Kofoid 

 and Swezy (1924a), note that during progression the amoeba may become 

 elongated, while the hindermost portion becomes drawn out into a tail- 

 like process to which adhere collections of bacteria, leucocytes, and debris. 

 The amoebae vary in diameter from 10 microns upwards, but they are 

 rarely seen with a diameter above 20 microns (Fig. 103). Forms up to 

 40 microns in diameter have, however, been described. There is dis- 

 tinguishable a clear, narrow ectoplasmic layer and a highly vacuolated 

 granulated endoplasm. The many food vacuoles contain a variety of 

 structures, some of which stain black with iron hsematoxylin, and are 



.\:: 



# 



Fig. 103. — Entamceha gingiralis from ScrapinCxS from a Carious Tooth ( x 2,000). 



(OrICxINAL.) 

 In three of the amoebfle are seen the large ingested bodies of doubtful nature. 



probably the nuclei of degenerate pus or tissue cells. Smith and Barrett 

 (1&15) and others state that red cells are sometimes ingested, but the 

 majority of observers, including the writer, have obtained no evidence 

 of this. The food vacuoles also contain bacteria of various kinds. The 

 nucleus is distinctly smaller than that of E. coli, which it resembles, 

 however, in general features. The nuclear membrane is generally lined 

 with closely packed granules of chromatin, which in stained specimens 

 appear as a uniform black ring. There is a karyosome which may be 

 surrounded by a clear area, as in the nuclei of E. coli and E. histolytica. 

 According to Dobell (1919), the karyosome is either central or excentric 

 in position, and there is no chromatin upon the linin network. As in the 

 case of the nuclei of E. coli and E. histolytica, some observers have main- 

 tained that there is a centriole within the karyosome. 



