92 HUMAN INTESTINAL PROTOZOA IN THE NEAR EAST 



latter are possibly encysting forms which will give rise to the cysts 

 which appear almost structureless when seen in the fresh condition. 

 As a rule the amoebae move sluggishly, throwing out one or more 

 blunt ectoplasmic pseudopodia. They do not glide along in the true 

 " limax " manner. The nucleus with its large chromatin block can 

 sometimes, though rarely, be detected in the living amosbae. The 

 stained amcebse (Plate I, figs. 12 to 17)* show the same clear or 

 vacuolated cytoplasm seen in life. The structure of the nucleus 

 can however be more clearly seen. Generally this appears to be of 

 the " karyosome " type with a clear nuclear membrane and large 

 centrally arranged chromatin block or karyosome which is often 

 irregularly shaped. The position of the chromatin block at the 

 centre of the nucleus is often only apparent, for in certain positions 

 of the nucleus it is seen to be lying laterally against the nuclear 

 membrane. In those cases in which 'it seems to be centrally 

 situated the appearance may be due to the nucleus lying with the 

 chromatin mass on the upper or lower surface of the nuclear mem- 

 brane as the amoebae lies on the slide. Sometimes the laterally 

 placed chromatin mass is connected with a filament which passes 

 across the nucleus to a granule lying on the nuclear membrane 

 opposite to it (Plate I, fig. 15).* The occurrence of this type of 

 nucleus in the amoabae is of importance, for it is a very common type 

 of nucleus of the encysted forms and greatly strengthens the belief 

 that the cysts and the amoebae are one. 



Encysted Amoebic. The cysts of E. nana are oval, spherical or 

 more irregularly shaped structures having a diameter of 7 to 8 microns 

 when spherical and a length of 8 to 10 microns when elongated 

 (Plate I, figs. 18 to 23).* The later type is most easily recognized as 

 a pale whitish and structureless body in which no detail can be 

 detected. Even when mounted in iodine it is only occasionally 

 that the internal nuclei can be seen. The cysts of the amoebae 

 have hitherto been regarded as of a vegetable nature. Fixed in 

 Schaudinn's fluid and stained with iron haematoxylin the nuclear 

 details can be as clearly seen as the small size of the cysts permit. 

 There are either one, two or four nuclei, and these are generally 

 grouped together towards one end of the cyst. Most important 

 is the structure of the nucleus. It will be seen by reference to the 

 figures in Plate I* that the chromatin is generally arranged as a 

 mass at one side of the nuclear membrane, while very frequently 

 a fine filament connects the mass with a granule on the opposite 



* See inset between pages 148 and 149. 



