FOEMS OF ENTAMCEB^E 645 



form to the cystic stage the following changes occur. The 

 entamoeba becomes smaller ,ancl the nucleus more distinct and 

 richer in chromatin, though still maintaining its characteristic 

 features. Further diminution in size occurs, the chromatin 

 becoming still more condensed, and the nucleus divides into two 

 or even into four before encystment. These transition forms 

 are to be met with in stools which are losing the typically 

 dysenteric character. Finally the small cell loses its amoeboid 

 property and the hyaline cyst-wall forms around it. It is 

 important to note that while the administration of emetine 

 kills off the active entamoeba? with rapidity, it has practically no 

 effect on the encysted forms. 



The following is the process of cyst formation as described by Schaudinn. 

 In the earliest stage of the change the nuclear membrane becomes broader 

 and fades into the protoplasm, whilst the chromatin becomes dispersed 

 through the endoplasm in the form of small chromidia. Buds then form 

 on the surface, and into these some of the chromatin passes. Around 

 these buds concentric striation can be seeii, and then a hyaline cyst wall 

 is formed, which is highly retractile in character. The cyst then becomes 

 separated from the rest of the cell. Several cysts or encysted spores, 

 which measure 2 to 7 fi in diameter, may be formed from the same amieba, 

 and the remnant of the cell undergoes disintegration. This description 

 was confirmed in the essential points by Craig and by Hartuiann. The 

 account given first is, however, that now generally accepted. 



The entamoeba coli is an organism of about the same size 

 as the previous, but on the whole is a little larger. When 

 at rest it shows no differentiation into ectoplasm and 

 endoplasm, and the nucleus, usually situated in the centre, is 

 readily seen, and shows a highly refractile membrane with 

 chromatin masses scattered in the interior. The protoplasm is 

 somewhat granular, and in it there are often small vacuoles con- 

 taining glycogen. During amoeboid movement, which is usually 

 sluggish, some delicate processes of ectoplasm come into view. 

 Red corpuscles are rarely found in the interior and only in 

 small numbers. The cellular changes in the encysting of the 

 entamoeba coli were worked out by Schaudinn. They are of a 

 somewhat complicated character, involving the formation of 

 reduction bodies and copulation of nuclei, but the ultimate result 

 is the formation of a fairly large cyst, which contains from two to 

 eight small cells. As seen in the fresh state in faeces, the cysts 

 measure 15-20 fi in diameter, the cyst wall is distinct and 

 refractile, and in the interior 2-8 nuclei are clearly visible. 

 They are thus distinguishable from those of E. histolytica. 



Cultivation. — Various attempts have been made to cultivate 

 the amoeba of dysentery, and Kartulis considered that he obtained 



