254 FAMILY: AMCEBID^ 



be no more than 5 microns in diameter, or 20 microns or more. In varying 

 number it can be found in practically every stool examined. It reproduces 

 as a rule by binary fission, and multiplies rapidly in certain media, 

 such as that used for the cultivation of E. histolytica. Occasionally, 

 as pointed out by Alexeieff (1911rf), forms with numerous nuclei are 

 seen, and it appears that the cytoplasm concentrates round these 

 nuclei, producing eventually a number of daughter forms within the 

 original cyst membrane. Such a form was seen in human fseces by 

 the writer and O'Connor (1917) in Egypt. Blastocystis is a vegetable 

 organism, but not infrequently it may be simulated by cells, flagellates, 

 or amoebae, which in a degenerating condition develop a large central 

 vacuole. Cysts of amoebae may be confused with fat globules (castor oil), 

 or globules of semi-digested muscle fibres. The latter may be perfectly 

 spherical and homogeneous. They are usually of a yellow-brown tint. 

 In iodine solution they stain a pale brown colour, or, as sometimes happens, 

 they become definitely pink. They are highly refractile, and show no 

 internal structure either in saline or iodine solutions. When once an 

 observer has become familiar with the actual appearance of the cysts 

 of the intestinal Protozoa, it is hardly possible to confuse them with 

 other objects, and this familiarity can only be obtained by practical 

 experience with the microscope. Intestinal epithelial cells swollen as a 

 result of degeneration, and the large macrophages which are sometimes 

 seen with included red blood-corpuscles, have been frequently mistaken 

 for amoebae. These cells, however, never exhibit active movements, 

 while their nuclei have an appearance which is quite different from that 

 of the nuclei of amoebae. As dead and immobile amoebae may easily be 

 confused with large cells, and vice versa, it is safest to regard no cell 

 as an amoeba unless definite amoeboid movements are seen. Polynuclear 

 leucocytes, in which the nucleus has separated into four parts, may be 

 mistaken for four-nucleated cysts. Occasionally, cysts of free-living 

 Protozoa which have been swallowed in food or water may be met with 

 in perfectly fresh stools. It cannot be too strongly emphasized that 

 specimens examined should be as fresh as possible. 



ACTION OF DRUGS ON INTESTINAL AMCEBiE. 



There is only one drug which can claim to luive any marked specific 

 action on the intestinal amoebae of man, and this is emetine. Curiously 

 enough, it affects only two of these — namely, E. histolytica and /. 

 butschlii. The former is known to be a tissue parasite, while there is no 

 evidence that I. butschlii is anything more than a harmless commensal 

 which lives in the intestinal contents. On E. coli and the other forms 

 there is no evidence that emetine has any action whatever. 



