1072 PATHOGENIC PROTOZOA 



DIENTAMCEBA FRAGILIS (Jepps and Dobell, 1918) 



This is the only species of the genus and was discovered and 

 described by Dobell and Jepps in 1918, although it is probable that 

 Wenyon saw but did not describe it in 1909. 



Only eight cases of proved infection are known, although it is 

 probable that it is commoner than this would lead one to suppose 

 since the organism dies quickly and the degenerated forms are 

 soon unrecognizable. It is quite small the average size being 8 or 9 

 microns with extremes of 3.5 to 12. The eeto- and endoplasm is 

 sharply differentiated and the pseudopods, consist almost entirely of 

 ectoplasm. The cytoplasm contains food vacuoles filled with bacteria 

 but no red cells are ever seen; the organism is probably, therefore, 

 a pure saprophyte and without pathological importance. 



The nucleus is characteristic and is typically double, although a 

 few examples with only one nucleus have been seen. The nucleus 

 varies in size with the size of the cell; its nuclear membrane is 

 delicate and free from chromatin particles. All the chromatin of 

 the nucleus is accumulated in, the central karyosome where it consists 

 of a number of granules of varying distinctness all imbedded in a 

 linin network. The discoverers believe that the cell grown to full 

 size and then divides into two uninucleate daughter cells, which 

 increase in size and the single nucleus divides into two. Up to the 

 present time no cysts have been found, and in this it possibly 

 resembles E. gingivalis, in which the presence of cysts is still doubtful. 



