M. W. Jepps and C. Dobell 
859 
persons in England in order to obtain some conception of the incidence 
of protozoal infections in such cases. The infection of Case D. 1 was 
discovered in the course of this investigation. We. have so far discovered 
so few infections with Dientamoeba among the large number of dysenteric 
patients examined, that the single case among the non-dysenteric persons 
actually gives a higher percentage incidence in the latter class. Moreover, 
the mode of nutrition of Dientamoeha resembles that of Entamoeba coli 
and nana. It does not appear to be a tissue parasite like E. histo¬ 
lytica, and from this it may be inferred that it is, like the former, a 
harmless commensal. In contrast, however, with this supposition we 
must point out that three of our seven cases infected mth Dientamoeba 
have histories of intestinal troubles of long standing, as a cause of which 
no concomitant protozoal or bacterial organism has yet been incriminated. 
(See cases D. 5, D. 6, and D. 7 below.) 
We may add that we can give no information concerning the action 
of emetine or other drugs on Dientamoeba infections, since none of our 
infected cases has undergone specific treatment. 
It is only during the present year that we have recognized Dientamoeba 
as an independent organism. For this reason, and also on accoixnt of 
the rapidity with which the amoebae degenerate and disappear from 
the stools, we are at present unable to give any accurate figures for the 
frequency of its occurrence. Our impression is that it is very uncommon, 
but by no means so uncommon as our record of only seven infections in 
several thousand cases examined might appear to indicate. 
We have been unable to find any reference to the organism which 
we call Dientamoeba fragilis in previous publications dealing with the 
intestinal amoebae of man or other animals; but we believe that it was 
previously observed, but not described, by Wenyon in 1909. Whilst in 
England recently (June, 1917) Colonel C. M. Wenyon showed us some 
preparations which he made eight years ago, and which contained, we 
believe, the amoeba here described. Colonel Wenyon was not aware, 
when he showed us his preparations, that we had independently recog¬ 
nized this organism at the beginning of 1917; but on seeing some 
of our preparations he agreed with us that his forms were probably 
the same as ours, and the priority of their discovery belongs, therefore, 
to him. We may add that we ourselves both discovered the organism 
independently of one another—one of us (M. W. J.) having found it 
about a month before the other (C. D.), who did not know of the discovery, 
at a time when we were not working in collaboration. 
Parasitology x 
24 
