314 The Philippine Journal of Science ms 



1. IN DYSENTERIC STOOLS 



Both Entamoeba histolytica and Entamoeba coli occur only in 

 the motile stage in dysenteric stools; and, when double para- 

 sitization exists, Entamoeba histolytica is usually the more 

 numerous in such stools. 



Size. — The size of both histolytica and coli are subject to wide 

 variations, and little dependence can be placed on this character 

 for diagnostic purposes. In dysenteric stools histolytica often 

 appears larger than coli (Plate I, figs. 3 and 5). That this 

 larger size of histolytica is only apparent, and not real, is 

 probable from the fact that in the encysted stage (the only stage 

 in which reliable measurements can be made) histolytica is 

 almost invariably smaller than coli (Plate I, figs. 4 and 8) . This 

 apparently larger size of motile histolytica is probably connected 

 with the more active movements of this species; while coli is 

 sluggishly motile and tends to retain a more or less spherical 

 shape, histolytica is actively motile and is extended flat over the 

 surface of the substratum. 



Shape. — Entamoeba histolytica, being more actively motile 

 than Entamoeba coli, presents a more varied form to the observer. 

 While coli is usually round, oval, or slightly irregular, histolytica 

 is more often long oval, ligulate, or irregular in fresh dysenteric 

 stools. 



Appearance. — Entamoeba histolytica is hyaline and feebly re- 

 fractive while Entamoeba coli is more porcelaneous and refrac- 

 tive in appearance. 



Motility. — The amoeboid movements of Entamoeba histolytica 

 are very active in fresh dysenteric stools, and the motility of 

 this species often persists for some hours after the stool has 

 become cold. On the other hand, the movements of Entamoeba 

 coli are always sluggish, and all motility is usually soon lost in 

 cold stools. 



Cytoplasm. — The cytoplasm of Entamoeba histolytica is homo- 

 geneous, and in the stained entamoeba is seen to have a coarsely 

 reticulated structure (Plate I, fig. 5). In cold stools it fre- 

 quently appears much vacuolated. Contrary to the description 

 given by some authors, there is no true distinction to be seen 

 between ectoplasm and entoplasm in the resting entamoeba. In- 

 dividual entamosbae, which contain granular material from partly 

 digested food, sometimes present the appearance of a granular 

 entoplasm. In motile histolytica the extended pseudopods may 

 present a more dense, hyaline appearance than the reticulated 

 body of the cytoplasm. The cytoplasm of histolytica may contain 



