COPROZOIC PROTOZOA IN THE FAECES 71 



guished, since the worm eggs are much larger than the 

 coccidian oocyst. Eggs of the nematodes, Hetewphyes 

 heterophyes and Clonorchis sinensis measure about 30m 

 long, thus approximating the size of the oocyst of Isospora 

 hominis. But these eggs are flask-shaped, the shell is thick 

 and yellowish, and the truncate end is operculated. 



Algae. Some of the algae which abound in fresh, brack- 

 ish, and marine water, are occasionally found in the faeces. 

 They are covered by a conspicuous siliceous shell which 

 is variously sculptured and the body is usually flattened. 



Cellular elements of the intestine. In the faeces there 

 occur an enormous number of various cells derived from 

 the intestinal wall of the host. As seen in fresh smear, there 

 may occur squamous epithelial cells in various stages of 

 degeneration, sometimes with an irregular "amoeboid" 

 outline and a vesicular nucleus located near the center 

 (Fig. 16, 7). But these cells are flat as seen edgewise and 

 the nucleus is relatively small. It should be borne in mind 

 that no matter how closely the object may resemble an 

 amoeba, if there is no movement, it is most probably not 

 an amoeba. Polymorphonuclear leucocytes may contain 

 erythrocytes and simulate Entamoeba histolytica (Fig. 

 16, 8). Do not become confused with them. 



Free-living protozoa. If salt solution or distilled water 

 used for making fresh or permanent preparations of semi- 

 fluid or formed faeces are contaminated with free-living 

 protozoa, the preparation will naturally show them and 

 confusion may result. Therefore, the solution or water must 

 be renewed frequently with boiled ones. 



