88 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



of flagellates being 5 to 6 microns long. The width varies con- 

 siderably; the narrow forms 3 to 4 microns in width mostly 

 resemble a bird in outline; wider forms occur in which this 

 resemblance is lost, and finally forms which are practically spherical 

 are found. In addition to these forms there occur others which 

 are possessed of two cytostomes and two pairs of flagella. These 

 might be either dividing or conjugating forms, but the examination 

 of stained specimens shows the former view to be correct. 



Encysted forms of the flagellate are common in the stool 

 (Plate IV, figs. 7 and 8).* These are pear-shaped bodies 4'5 to 

 6 microns in length. They have a pearly-white appearance and 

 are quite structureless. They remind one of small tetramitus cysts, 

 but have not the few refractile granules which these cysts generally 

 possess. That these bodies are actually cysts of the flagellates is 

 proved by their constant association with it in the two cases 

 mentioned and their complete absence from all other cases 

 observed by us. 



In the two cases of Waskia intestinalis infection the flagellates 

 were present in the stool in enormous numbers during the height 

 of their development ; many flagellates were present in each field 

 of the T ^ objective. In the first case, from the stool of which 

 they disappeared after about six weeks' observation, the flagellates 

 became reduced in number towards the end and appeared as if 

 they were being crowded out by the larger and more vigorous 

 tetramitus. Knowing, however, that flagellate infections are 

 peculiarly irregular in their course, we recognize that it is 

 possible that the infection had only been reduced temporarily. 



Description of Stained Flagellates. The flagellates were studied 

 in films fixed in Schaudinn's fluid and stained by the iron haema- 

 toxylin method, and also in dry films stained by Eomanowsky 

 stain. In the stained film the flagellate is seen to have the same 

 shape as that of the living organism. The nucleus at the anterior 

 nd can be more clearly seen, and is found to consist of a spherical 

 nuclear membrane with usually a central karyosome. On the 

 surface of the nuclear membrane towards the cytostome are two 

 granules from which arise the two flagella. The dividing forms 

 are seen to have a simple dividing nucleus in which a centro- 

 desmose can be detected and at a later stage two distinct nuclei 

 {Plate IV, figs. 9 to 14).* 



The encysted forms show more details when stained than in 

 the living condition. Certain nuclear structures can be made out 



* See inset between pages 148 and 149. 



