ENDAMCEBA HISTOLYTICA 



Cyst. A thin peripheral wall is secreted by the pre- 

 cystic organism thus forming a spherical body, the cyst 

 (Fig. lb), which ranges from 5/1 to 20ix in diameter. 

 Different size races are indicated by differences in the 

 size of the cysts. The mature cyst contains 4 nuclei, each 

 of which appears like that of the trophozoite, but cysts 

 with I, 2, and 3 nuclei are frequently passed. Often 

 glycogen vacuoles and chromatoid bodies are present in 

 young cysts, but these are usually absorbed later. 



Life-cycle. The life-cycle oi E. histolytica appears to 

 be very simple. Trophozoites occur in the large intestine 

 in about 10 per cent of the general population; often in 

 the liver, where they may bring about the formation of 

 liver abscesses; and rarely in the small intestine, brain, 

 lungs, spleen and other parts of the body. A culture 

 method of diagnosis of intestinal amoebae similar to that 

 originated for intestinal flagellates by Hegner and 

 Becker (1922) is advocated by Craig and St . John 

 (1927). These investigators have found the Locke- 

 Serum medium the best for this purpose. One microscopic 

 preparation from each culture inoculated with fecal ma- 

 terial from 71 individuals resulted in 39 positives or an 

 incidence of 54.92 per cent. The various amoebae were 

 found in the following percentages: Endamccba hi^- 

 tolytica, 15.49 per cent; E. coli, 2g.^y per cent; Endoli- 

 max nana, 12.67 P^i" cent; and lodamceba williamsi, 5.63 

 per cent. It remains to be proved that this method can 

 be employed successfully under field conditions as Hill 

 (1926) has done for the diagnosis of intestinal flagel- 

 lates. 



Reproduction of the trophozoite is by binary fission. 

 59 



