ENTAMOEBA HISTOLYTICA 25 



"ordinary" amoeba {i.e., E. coli, as described by Schaudinn). Huber 

 told Schaudinn* of his observations — which were perfectly correct — but 

 neither the latter nor anybody else who knew of them seems to have 

 attached any importance to them at the time. After Schaudinn's death 

 the cysts were once more " discovered " by Viereck (1907) and by 

 Hartmann (1907), f who regarded them as belonging to new species 

 of Entmnoeha — named by them respectively E.tetragena and E.africana. 

 Elmassian (1909) again " discovered " them two years later, and regarded 

 them — together with the precystic amoebae which form them — as another 

 new species, which he named E. ininuta. These various " discoveries," 

 and others made during this period, only served to add to the existing 

 confusion. Quincke and Roos's observations were forgotten, Huber's 

 were ignored, everybody looked for — and some found — the non-existent 

 development of E. histolytica described by Schaudinn. No real advance 

 in our knowledge of the dysentery amoeba took place until the work of 

 Walker (191 1) made its appearance, followed soon after by his later 

 memoir, in collaboration with Sellards (191 3), which solved most of the 

 problems connected with E. histolytica. 



Walker (1911) first showed that E. histolytica and E. coli are quite 

 distinct and easily separable species, though possessing a similar 

 development. The first forms cysts containing, when mature, 4 nuclei ; 

 the second cysts containing 8 nuclei. In the cysts of both, development 

 occurs in a straight-forward manner by the repeated division of an 

 originally single nucleus — without any " autogamy " or other mysterious 

 processes such as were described by Schaudinn. Then he showed that 

 E. Iiistolytica, E. tetragcna, and E. ininuta are all different names for one and 

 the same species. Finally, with Sellards (1913), he proved conclusively 

 by experiments on human beings that man becomes infected by ingesting 

 the cysts of these amoebae ; and that infection with E. histolytica may give 

 rise to dysentery, while E. coli is harmless to its host. To Walker (191 1, 

 1913) we also owe the conception no less than the discovery of the 

 "carrier" condition in E. histolytica infections — a conception which 

 cleared up all the difficulties which previously prevented the life-history 

 and activities of this organism from being properly understood. Certain 

 details of Walker's work will be considered later. Here the historic 

 importance of the work as a whole is all that immediately concerns us. 



All the correct observations made since the appearance of the results 

 of Walker and Sellards merely confirm or elucidate the facts which they 

 established. It will therefore be unnecessary to consider, at this point, all 

 the minor details contributed by numerous subsequent workers ; but I 

 would especially mention here the names of Darling (1912, ct seq.), 

 Wenyon (1912 et seq.), and James (1914), who have all made valuable 

 later contributions to our knowledge of E. histolytica. 



Nomenclature. 



The nomenclature of the dysentery amoeba has been for some time a 

 very vexed question. It has already been discussed ad nauseam by 

 numerous writers : and my only excuse for reopening the question is my 

 desire to reach finality in the matter. I have already discussed the 



* Vide Huber (1906, 1909). 



+ F/rf^ Hartmann and Prowazek (1907). 



