PROTOZOA IN THE DIGESTIVE TRACT 15 



2. Entamoeba coli (Grassi 1879) 



Synonym: Endamoeha coli (Grassi) 



This is an amoeba which Hves in the kmien of the colon 

 and is looked upon as a commensal. It is a very common 

 amoeba in the human intestine and easily mistaken for E. 

 histolytica because of the morphological similarity. Tro- 

 phozoites and some cysts occur in fluid or semifluid faeces, 

 but formed faeces contains only cysts. 



Trophozoites 



1. Living specimens. This amoeba (Fig. 2, 1) resembles 

 E. histolytica in size, but the ayerage indiyidual appears 

 to be slightly larger than the latter. It measures 15-40m in 

 the largest diameter, but the majority are about 20-35|j. 

 Eyen in freshly obtained material, it is less actiye than E. 

 histolytica. The cytoplasm is not well differentiated. The 

 ectoplasm is thin and ill-defined and merges into the yo- 

 luminous endoplasm. The endoplasm is usually yacuolated 

 or alyeolated, and contains numerous bacteria, yeasts, 

 other microorganisms of large size in addition to yarious 

 debris that occur in the lumen of the colon. The erythro- 

 cytes are normally not taken in by this amoeba, although 

 instances of ingestion of erythrocytes by it especially in 

 yitro haye been reported. For diagnostic purpose, there- 

 fore, one can place a great emphasis on the presence or 

 absence of the erythrocytes in the endoplasm as suggesti\ e 

 of E. histolytica or E. coli. The nucleus is more easily seen 

 than that of E. histolytica, especially in the specimens in 

 which a comparatiyely small number of food particles are 

 present. It appears as a ring of coarse refractile granules 

 with a large granule located near, but not in, its center. 



