78 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



be identified by the presence of its cyst in the formed stools from 

 which the flagellates are usually absent. 



The cysts of T. mesnili were first described by one of us 

 (C. M. W.) in the original description of the organism. The cyst 

 was there depicted as a small oval structure very much like a 

 small lamblia cyst, within which could be detected the nucleus and 

 cystostome of the flagellate. Though this type of cyst occurs not 

 infrequently, the commonest cyst is distinctly pear or bottle shaped 

 with one end narrower than the other as shown in the figures. This 

 type of cyst was figured by Prowazek and Werner in a paper 

 describing some tetramitus infections met with in Hamburg (Arch. 

 filrSchiffs. und Tropen-Hyg., Bd. 18, 1914, Beiheft 5, Festschrift). 



As seen in fresh preparations the pear or bottle shaped cysts 

 are pale bodies which show no internal structure except two or 

 three, rarely more, small refractile, greenish granules (Plate II, 

 figs. 10 to 12).* 



They vary in length from 7 to 10 microns and sometimes 

 occur in such large numbers in the constipated stool that several 

 can be seen in every field of the one-twelfth objective. The recog- 

 nition of the cysts in the fresh condition is sometimes rendered 

 difficult on account of the presence of a yeast of similar shape. 

 The yeast, however, shows clearly its internal structure of granular 

 cytoplasm with large vacuole, the whole being much greener than 

 the pale structureless tetramitus cyst. The yeast varies in shape 

 more than the tetramitus cyst and the characteristic budding forms 

 are to be found if one looks for them (Plate II, figs. 16 to 18).* 



The tetramitus cysts stain readily by the iron hsematoxylin 

 method after fixation in Schaudinn's fluid, and when suitably 

 differentiated they show the characteristic nucleus and the cyto- 

 stome rim (Plate II, figs. 13 to 15).* One or more granules are 

 present near the narrow end of the cyst and the deeply staining 

 line which borders the cytostome takes origin in one of these. In 

 addition one can sometimes make out the flagellum, which normally 

 lies within the cytostome also arising from this granule. Further 

 than this little structure can be detected and we have not seen any 

 indication of nuclear multiplication. The four-nuclear cyst figured 

 by one of us (C. M. W., Lancet, November 27, 1915, fig. 17, and 

 Journal of the Royal Army Medical Corps, December, 1915, 

 fig. 17, p. 614), as a possible later stage in the development of the 

 tetramitus cyst, has turned out to be the cyst of E. nana described 

 on page 90 and not a cyst of the flagellate. 



* See inset between pages 148 and 149. 



