VIII, B, 4 Walker and Sellards: Entamcebic Dysentery 313 



closely resemble resting or encysted entamoebse. The cells con- 

 tain from one to several small, round or irregular, refractive, 

 nucleus-like bodies that stain like chromatin. It is possible that 

 they are cells showing degenerative changes with fragmentation 

 of the nucleus. These cells are, however, readily distinguished 

 with high magnification from entamoebas by the structure of the 

 nucleus-like bodies, which are not ring-form, but solid chromatin 

 masses. Motile forms of entamoeba also will be frequently 

 found in such stools, which will aid in the diagnosis. 



Certain unicellular vegetable organisms known as Blastocytis 

 hominis Brumpt, which are believed to be allied to the yeasts, 

 are found rather frequently in the stools of man in the Tropics. 

 Smaller forms of these cells have been mistaken for the cysts 

 of Trichomonas intestinalis, and the larger forms simulate the 

 encysted entamoebse very closely in size and general appearance. 

 They are, however, slightly less refractive than the cysts of 

 Entamoeba, and can, therefore, be distinguished by the ex- 

 perienced observer, even with low magnification. Under high 

 magnification they are seen to have a wholly different structure 

 from the cysts of Entamoeba. They are round, oval, or slightly 

 irregular, and possess a distinct wall. The protoplasm is re- 

 stricted to several narrow segments of the cell, and contains 

 from one to several granules staining like chromatin. The main 

 body of the cell is filled with a homogeneous, hyaline, slightly 

 refractive, and often faintly yellow mass, the nature of which is 

 doubtful, but it probably represents reserve food substance. 



An examination of figs. 3 to 8 on Plate I will give a good idea 

 of the general morphology of the entamoebse. Figs. 1 and 2 

 show the motile encysted stages of a typical nonparasitic amoeba 

 for comparison with the entamoebse. 



The differentiation of Entamoeba histolytica from Entamoeba 

 coli depends upon certain morphological characters of the two 

 species which are very distinctive at certain stages, but less 

 distinctive at other stages, of the development of the two species. 

 These stages of the development of the parasites are correlated 

 with the clinical manifestations of the infection and especially 

 with the consistence of the stools of the host. Therefore, the 

 comparative morphology of Entamoeba histolytica and Entamoeba 

 coli are most conveniently discussed in relation to the nature of 

 the stools in which they are found; namely, (1) in dysenteric 

 stools, (2) in diarrhoeal stools and stools after a purgative, and 

 (3) in formed stools. 



