50 



and it may be noted that the inmates of another asylum, similarly 

 examined by Smith (1919) subsequently, gave a percentage of 

 only 3. Nothing else noteworthy regarding the incidence or 

 distribution of this amoeba appears in the records. 



Although the figures so far obtained indicate that only some 

 9 to 13 per cent, of Britons harbour this organism, there is reason 

 to believe that this figure is too low. The organism is very small, 

 and infections are in consequence easily overlooked ; and it was 

 not until comparatively late in the War that most protozoologists 

 in this country became familiar with it. Careful examination of 

 large numbers of soldiers returning from abroad has shown that 

 M nana is very common in them — being the next commonest 

 amoeba after K coli. My own records show that it probably 

 occurs in not less than 50 per cent, of such oases. 



(4) lodamoeba butschlii. — So far as records are available, this 

 amoeba appears to be rare in Britain. It undoubtedly occurs, 

 however, though the findings indicate that it is present in less 

 than 1 per cent, of the population. The first indigenous infections 

 described appear to be those found by Matthews and Smith 

 (1919).^ Only one case of infection has as yet been recorded in 

 a child under twelve (Matthews and Smith), and at present the 

 records are too meagre for it to be possible to draw any con- 

 clusions regarding the incidence of the organism in relation to 

 •sex, age, or occupation. I will merely note that this amoeba 

 appears to be less common in British residents than in troops re- 

 turning from overseas. The highest rate of infection hitherto 

 recorded in British cases is 1 per cent. — found by Smith (1919) in 

 a series of 504 inmates of a lunatic asylum. 



The published records give figures for England and Wales 

 only. I may add, however, that Case 393 of Baylis (1919) — as 

 appears from his card entries, though not stated in his published 

 paper — was infected with I. butschlii, and this shows that the 

 organism probably also occurs in Ireland. This is all that can be 

 said at present regarding its distribution in these islands. 



(5) Dientamoeba fragilis. — Not a single instance of infection 

 with this small and apparently rare amoeba has been recorded in 

 any of the series here considered. That it occurs in persons who 

 have never left Britain is, however, certain : for I have recorded, 

 with Miss M. W. Jepps, one case of infection in a person belong- 

 ing to this category (see Jepps and Dobell, 1918). At present 

 this is the only British case known to me. 



The organism may be commoner' than these findings appear 

 to indicate, for it is small and extremely delicate, and perishes 

 soon after leaving the body. Its cysts are still unknown, and 

 the organism itself can only be found in soft stools examined in 

 a very fresh condition. Consequently, even when present it is 



1 Recorded by these workers throughout under the name of ' Iodine cysts '. See 

 my hook (1919) for the history of this organism. 



