44 



Age of Cases. No. examined. Percentage of £. histolytica. 

 1— 5 275 1-1 



5—12 223 3.1 



circa 18 1098 5-6 



I am not sure whether these authors accept this interpretation 

 of their figures, for they appear to believe that some intestinal 

 infections may be commoner in children than in adults. This 

 supposition is linked with their hypothesis that protozoal infec- 

 tions of the intestine do not persist indefinitely, but tend to die 

 out in the course of time. They have not been able, however, to 

 obtain any direct or conclusive evidence of this, and there are 

 many observations which are not consistent with such a belief. 

 It must be noted here, further, that the above figures are selected, 

 and it is possible to select others which might lead to a different 

 conclusion. The numbers constituting most of their series are 

 comparatively small, however, and the error inherent in a system 

 of only one examination per case is large. And consequently 

 when results such as those recorded by Miss Nutt (p. 36) are 

 considered — she found 2-7 per cent, of 185 children and only 1-5 

 per cent, of 321 adults infected with K histolytica — it is by no 

 means easy to draw certain conclusions from them. It is at least 

 debatable whether these findings indicate — as they might seem 

 to at first sight — that the children were more heavily infected 

 than the adults : and on other grounds such a generalization 

 appears to me unwarranted. 



Sex. — In several series the cases have been sorted into sexes, 

 and the findings presented for the two classes separately. The 

 results have been consistent throughout, and show clearly that 

 JE. histolytica occurs in males and females with equal frequency. 

 It will be unnecessary to recapitulate all the findings here : an 

 example will suffice. Miss l^Jutt, in the Leeds series, found 1-2 

 per cent, of adult males infected, and the same percentage of 

 adult females. Other series gave comparable results, and 

 Matthews and Smith have already concluded that the distribu- 

 tion of U. histolytica — and other intestinal protozoa — is ' irre- 

 spective of sex '. 



Occupation. — Matthews and Smith (1919) note that ' some of 

 the results we have obtained seem to indicate that there may be 

 occupational differences in the incidence of infection' with E. 

 histolytica. They give the occupations of a number of the cases 

 which they studied, and these have been recorded also for most 

 of the individuals in the newer reports printed in the previous 

 chapter. From all the records — including those of Baylis(1919), 

 and others already printed elsewhere— I have been able to collect 

 information concerning the occupation of one hundred persons 

 found to be infected with E. histolytica in Britain. Not one of 

 these had ever been abroad prior to the time of examination. I 

 have purposely excluded from this series all children under 

 12, and patients in lunatic asylums. On analysing and classify- 

 ing these cases I obtained the following list : 



