RHIZOPODA 405 



fragments and red blood cells. The nucleus is very distinctly 

 visible in the living ameba. It is spherical and surrounded by-a- 

 thick doubly contoured nuclear membrane. The chromatin is 

 usually distributed just beneath the nuclear membrane in largest 

 amount and in the center there is a karyosome with definite centri- 

 ole. The vegetative multiplication takes place by division into 

 two daughter cells. Multiple division seems not to occur. 



Cyst formation is rarely observed. The cysts are most likely 

 to be found when the stool becomes formed in 

 convalescence from an attack of dysentery and 

 they may then be very numerous. The mature 

 cyst contains four nuclei, and frequently contains 

 also one or more large masses of chromidial sub- 

 stance which stain black with iron hematoxylin. 



The forms of the organism commonly observed FlG - * ib 



. . , . , , . mceba tetragena. Ma- 



in the feces of dysentery are either the active ture cyst containing 

 vegetative cells 1 or degenerating forms, and the ^ STto^id 

 latter may lead to confusion unless their true na- substance. (After 



j Hartmann.) 



ture is recognized. 



E. tetragena is regarded as the causal agent of amebic or tropical 

 dysentery and there can be little question that it is the parasite 2 

 present in most cases presenting the typical clinical picture and 

 pathology of the disease. It is doubtless transmitted in food and 

 drinking water in the encysted stage. 



Entamceba Histolytica. Schaudinn in 1903 distinguished 

 this species from E. coll and regarded it as the causal organism 

 in amebic dysentery. The subsequent study of Schaudinn's 

 preparations by Hartmann 3 has shown that most of the specimens 

 recognized as E. histolytica by Schaudinn are in reality vegetative 

 and degenerating forms of E. tetragena. Our whole knowledge 

 of the species, which was founded upon Schaudinn's studies, 

 therefore becomes very uncertain and even the existence of E. 

 histolytica as a disticnt species may be seriously questioned. 



1 Hartmann: Arch. f. Protistenkunde, 1912, Bd. XXIV, S. 163-181. 



2 Whitmore: Arch. f. Protistenkunde, 1911, Bd. XXIII, S. 71-80. 



3 Hartmann, in Prowazek, Handbuch der Path. Protozoen, 1912, Bd. I, S. 58-61. 



