FORMS OF ENTAMCEB^E 643 



locomotion may be fairly rapid; and red corpuscles, bacteria, 

 cells, etc., may often be seen in the interior, though the ingestion 

 of red corpuscles is by no means a constant feature. The organ- 

 ism usually dies and undergoes disintegration in a comparatively 

 short time after being removed from the body ; the stools ought 

 therefore to be examined in as fresh a state as possible. Multi- 

 plication takes place by division into two and also by budding. 

 Schaudinn considered that the former was a direct division, but 

 Werner and Craig have found that it is of mitotic nature. The 

 cyst formation of this organism, as described by Schaudinn, is 

 specially seen when the disease is in process of cure and the stools 

 are beginning to have a less fluid character. 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 seen, and 

 then a hyaline cyst wall is formed, which is highly refractile in 

 character. The cyst then becomes separated from the rest of the 

 cell. Several cysts or encysted spores, which measure 2 to 7 yu, 

 in diameter, may be formed from the same amoeba, and the rem- 

 nant of the cell undergoes disintegration. These cysts, as will 

 be shown below, represent a resting-stage with high powers of 

 resistance to external agencies, and are concerned in producing 

 infection of another subject. This description has been con- 

 firmed in the essential points by Craig and by Hartmann. The 

 organism has been shown by experimental methods to have 

 pathogenic properties (vide infra). 



Entamoeba tetragena. This organism is said to measure 

 15-45 n in diameter. The nucleus is relatively large and is 

 clearly visible when the organism is at rest; it has a well- 

 marked nuclear membrane and is rich in chromatin. In these 

 respects it differs from E. histolytica. The ectoplasm can 

 be distinguished with difficulty unless active movement is going 

 on, when it forms blunt highly refractive processes like those of 

 the E. histolytica ; red corpuscles, etc., are often seen in its 

 interior. It multiplies by a form of primitive mitosis (Craig), 

 and also by division within a cyst. When the latter is about to 

 be formed the nucleus divides into two, the protoplasm becomes 

 surrounded by a thin cyst wall, and then four small cells are 

 formed within the cyst hence the name. The fully formed 

 cyst measures about 7-12 p in diameter. Originally discovered 

 by Viereck in Hamburg in a case of dysentery from Africa, it 

 was found by Hartmann in cases in Africa, and by Craig in 



