ENTAMOEBA COLI 8 1 



liquid contents of the upper part of the colon ; and in the more solid 

 and formed faeces in its lower parts, encystation occurs — the fully- 

 developed cysts being normally discharged in the stools. This was first 

 pointed out by Grassi (1882, 1883), and all subsequent work has shown 

 that his conclusions were correct. At present there is no evidence that 

 £. coli can live in any other part of tiie human body, or in any other 

 manner — that it can invade the tissues, or give rise to secondary infec- 

 tions of the organs. 



Multiplication. — There can be little doubt that E. coli, like other 

 Entaiiioebae, reproduces by fission into two. This has been stated to 

 occur by Grassi (1888) and many later workers; but nobody has yet 

 described the process, and I doubt whether anybody has ever seen it. 

 Schaudinn (1903) alleged that E. coli reproduces " by simple division," 

 with an " amitotic " division of its nucleus : but he never described the 

 process properly, and the rest of his observations on this organism are 

 so full of errors that it is impossible to place much confidence in his 

 mere statement. The earlier observations on "dividing" organisms, 

 made by Casagrandi and Barbagallo (1897), are also very questionable. 

 I think they merely saw binucleate amoebae — as many others, including 

 myself, have done since — but not real division stages. Craig's (191 1) 

 figures of " multiplication by simple division in £. coli " (his fig. vi) I 

 take to be diagrams drawn from imagination. Hartmann and Whitmore 

 (j.912) saw binucleate amoebae, and described "beginning stages" in 

 nuclear division, with "heteropolar ' and "tripolar karyosome-spindles." 

 Hartmann (19 12) has even asserted that 20-30 per cent, of all individuals 

 of £. coli are found to be in early stages of division : but this is certainly 

 incorrect, and a very fantastic interpretation of the appearances which 

 he saw. In the "apparent division" stages of E. coli figured by James 

 (1914), degeneration is, to me, far more apparent than division. Many 

 other workers — for example Mathis and Mercier — refer to the division 

 of E. coli as though it were well known to occur. Doubtless it does 

 occur, but I can find no satisfactory evidence that anybody has yet 

 observed it. 



In stools containing large numbers of E. coli one can generally find 

 individuals containing two nuclei, and sometimes nuclei which resemble 

 the degenerate division stages occasionally seen in E. histolytica in human 

 stools. Save for these questionable forms, I have never been able to 

 find division stages of E. coli, in spite of much search : and consequently 

 — although I have no doubt that it must occur, and often — I cannot 

 give any description of the process of multiplication in this species. 



Several workers have described a process of multiple fission or 

 schizogony in E.coli. It was first suggested, I believe, by Casagrandi and 

 Barbagallo (1897), ^^'^^ figured what they believed to be an 8-nucleate 

 amoeba (their PL II, fig. 13) : but they were unable to prove that multi- 

 plication occurs in this way. Schaudinn (1903) later alleged that E. coli 

 undergoes multiple fission into 8 small amoebae — the process being 

 preceded by a multiple division of the nucleus. No competent observer 

 has ever confirmed this observation, although it has become a favourite 

 •th writers of text-books. It has been accepted by Craig (191 1) and 

 though the nearest approach to confirmation appears to be that 

 .hi (1913) : but judging from his figures, the " schizonts " are 

 y cysts of E. coli — showing various appearances commonly met 

 preparations — and the brood of young amoebae formed by their 



