lODAMOEBA BUTSCHLII I13 



It may be added that Brumpt (1913), James (1914), and Pestana 

 (1917), have considered Prowazek's "Entamoeba" bntschlii to be E. colt. 

 James, indeed, says that its " cysts can in no way be differentiated " from 

 those of the latter. This I conceive to be a quite unjustifiable interpreta- 

 tion. Kuenen and Swellengrebel (1913) suggested that "£." biitschlii is 

 a degenerate " minida " {i.e., precystic) form of £. histolytica, and Flu 

 (1918) seems to consider it also as a degenerate form of this species. 

 This also I regard as very wide of the mark. I believe that none of these 

 authors had sufficient material at their disposal to enable them to form 

 a correct opinion regarding this organism. Wenyon and O'Connor 

 (1917) have called attention to the resemblance of Prowazek's "£." 

 biitschlii to E. nana, but note that " this author's description is too 

 meagre to allow of any comparison being made " ; and they add that 

 " he does not describe any encysted forms" — which is not quite correct, 

 though it might perhaps be asked how far Prowazek's rough account 

 can properly be termed a "description." 



Description. 



lodamoeba biitschlii is, as a general rule, a small amoeba intermediate 

 in size between E. coli and E, nana. I believe I have, in the past, 

 sometimes mistaken the living organisms for small individuals of the 

 former species or large ones of the latter. The diameter of the living 

 amoebae, when rounded, is usually about 9 — 13 fi ; but larger individuals 

 up to 17 — 20 /A, and very tiny ones down to 5 jx, are also found. I have 

 never seen any as large as 24 /i — the maximum size mentioned by 

 Prowazek (1912 a). Since he studied a case infected with £. coli also, it 

 is possible that he mistook some individuals of this species for /. biitschlii. 

 According to Kuenen and Swellengrebel (1917) the amoebae measure 

 10 — 13 ;a in diameter : according to Brug (1919) 12 — 20 jx. 



In general form and habit this organism is closely similar, when 

 alive, to a small specimen of £. coli. Ectoplasm and endopiasm, pseudo- 

 podia, and the sluggish movements when outside the body, are closely 

 alike in the two species. The cytoplasm of /. biitschlii is also frequently 

 tilled with food-vacuoles containing numerous bacteria and other foreign 

 particles ; and a contractile vacuole is, of course, likewise absent. Apart 

 from its usually smaller size, the only obvious character which distin- 

 guishes /. biitschlii in the living state is its nucleus, which is almost 

 invisible — in fact, often quite invisible, in organisms containing much 

 food. In this respect it differs greatly from £. coli, whose nucleus — 

 appearing like a beaded ring — is so conspicuous in the living amoeba. 

 As a rule, /. biitschlii becomes rounded and begins to degenerate very 

 soon after leaving the human intestine. 



In good stained preparations this organism is easily distinguished by 

 its nucleus from any of the other amoebae living in man. (See PI. I, 

 fig. 10, and PI. II, figs. 32 — 34.) The resting nucleus is similar to that 

 of many of the small free-living amoebae. It is vesicular, with a 

 moderate-sized central karyosome, and measures from about 20 /x in 

 small to about 3'5/a in large individuals. Its diameter is usually between 

 one fourth and one fifth of that of the whole organism — when fixed and 

 stained ; and the diameter of the karyosome varies from about one half 

 to one third of that of the entire nucleus. The karyosome stains intensely 

 with chromatin stains. With iron-haematoxylin it may appear homo- 

 geneous (fig. 34), or may show a paler centre (fig. 32). Occasionally a 



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