ECOLOGY, COMMENSALISM AND PARASITISM 391 



Nor is the title clear for the generic name End(Ent)ameba 

 unless the arneba of the cockroach {E. blattae) and the dysentery 

 amebae of the human intestine are continued to be regarded as 

 cogeneric. If, and it may be true, these amebae are generically 

 different, then some other name must be used for the human para- 

 sites, for Endameba goes with E. blattae, Leidy. Dobell and Wen- 

 yon and Reichenow (1928) recognize this difficulty but are not sure 

 that these amebae belong to different genera. In case they do, 

 they agree in proposing Endameba for E. blattae and the form 

 Entameba for E. coll and the pathogenic species of man. This, 

 however, is a mere subterfuge, for they are only different spellings 

 of the same term. Dobell shows that in case Endamoeba coli is 

 shown to be generically different from E. blattae, then Chatton and 

 Lalung-Bonnaire's (1912) name Loschia would have priority. 



Returning from this controversial digression to the host-parasite 

 relations of the intestinal amebae of man, we find that throughout 

 the decade 1890-1900 there was little recognition of two types of 

 amebae— one harmless, the other pathogenic. Quincke and Roos 

 (1893) and Roos (1894) indeed spoke of "harmless" and "patho- 

 genic" forms, the former being non-pathogenic to cats upon infec- 

 tion with amebae per os or per anum. Casagrandi and Barbagallo 

 (1895-1897), who introduced the generic name Entamoeba coli in 

 ignorance of Leidy's Endamoeba, returned to Grassi's contention 

 that there is only one form of ameba which they termed E. coli 

 (1895) but later changed to E. hominis. 



Schaudinn (1903), also ignorant of Councilman and Lafleur's 

 work, was convinced by work of earlier observers and more so by 

 his own observations and experiments that there are two distinct 

 species of intestinal amebae, one harmless, the other pathogenic. 

 He had an excellent opportunity to rectify the mistake which was 

 then in its infancy of regarding Losch's E. coli as a harmless ameba, 

 but he failed. He accepted Casagrandi and Barbagallo 's generic 

 name Entameba but regarded their E. hominis as the same thing 

 as Losch's A. coli, and such was his great influence at that time that 

 this name E. coli was attached, firmly but erroneously, to the com- 

 mon non-pathogenic ameba of man. For the pathogenic species 

 he proposed the name Entamoeba histolytica. 



With the establishment of two species of Ameba— one of which 

 is pathogenic, some of the old difficulties which were engendered by 

 Grassi's and similar work on the one hand, and by that of Kartulis 

 on the other, were cleared up. Throughout this period, however, 

 there were skeptics who could not be convinced that any ameba 

 is an etiological agent in human dysentery, for cases of dysentery 

 in which no evidence of amebae could be found were turning up 

 repeatedly. This difficulty was finally removed by the discovery 

 by Shiga (1898), confirmed by Flexner, of the Shiga-Flexner bacillus 



