70 THE AMOEBAE LIVING IN MAN 



his observations ; but since then history has repeated itself many times.* 

 The conclusive experiments of Walker and Sellards (19 13) finally placed 

 the matter on a thoroughly scientific basis, and during the last decade 

 claims to have cultivated any parasitic amoeba have become fewer and 

 fewer. There are probably very few workers now who believe that 

 £. histolytica is cultivable by any known method. 



Recently Cutler (1918) has published a description of experiments 

 which lead him to believe that he has discovered methods for the 

 cultivation of this parasite. His work therefore requires notice here. 

 Although his account appears at first sight to prove that his claims are 

 justified, they have not yet been confirmed by other workers. In con- 

 junction with Capt. S. R. Douglas, I. M.S. (ret.), I attempted to cultivate 

 E. histolytica by his method, but all our attempts were complete failures. 

 This work, in conjunction with further information concerning his 

 methods kindly given to me subsequently by Mr. Cutler himself, has 

 shown me that his observations may be capable of a different interpre- 

 tation from that which he has put upon them. His experiments were not 

 quite so simple as they seem from his brief account ; and consequently 

 1 cannot yet regard his claim as fully justified until further evidence and 

 explanations, with independent confirmation by others, are forthcoming. 



Treatment. — It is not my intention to discuss the treatment of 

 E. histolytica infections here : but one aspect of this subject is so remark- 

 able that it is impossible to omit all reference to it even in a purely 

 zoological memoir. I refer, of course, to the specific action of emetine 

 on human infections with E. histolytica. Ipecacuanha has been used for 

 centuries as a cure for dysentery, but it is only comparatively recently 

 that its alkaloids — especially emetine — have been proved to be of the 

 highest therapeutic value in the treatment of infections with E. histolytica. 

 Upon human infections with this amoeba emetine has a remarkably 

 specific action. It was originally thought, as a result of Vedder's (191 2) 

 observations, that emetine is a peculiarly " amoebicidal " substance, 

 and that it acts by killing t-he parasite directly when administered to an 

 infected human being. It is almost certain now, however, that the 

 alkaloid is not particularly poisonous to amoebae, and that its action is 

 primarily upon the host and not upon the parasite (Dale and Dobell, 

 1917). Whatever the mechanism of this action may be, there can be no 

 doubt that emetine has a truly remarkable therapeutic efficacy when 

 administered in a suitable manner ;f and this specific reaction of the 

 parasite to the drug has done much to clear up the problem of the 

 species of amoebae inhabiting the human bowel. 



Geographical Distribution. — It is now certain that the present 

 geographical distribution of E. histolytica is world-wide. It is not 

 restricted to the tropics — as is frequently assumed — but occurs in every 

 country in which it has been sought by competent observers. Indigenous 

 infections are now known to occur, for example, in Russia (Losch, 1875 ; 

 Yakimoff, 1917) ; in France (Gailliard and Brumpt (1912), Paviot and 

 Garin (1913), Landouzy and Debr6 (1914), Ravaut and Krolunitzki 

 (1916), etc.) ; in Germany (Jurgens, 1906) ; in the Northern United 



* Cf. Musgrave and Clegg (1904, 1906), Lesage (1905, 1907), Walker (1908), Noc 

 (1909)) Gauducheau (1912), etc. 



t For further information on this subject see especially Wenyon and O'Connor 

 (1917), Dobell (1916, 1917), Dobell, Gettings, Jepps, and Stephens (1918). 



