maladies with precision. Numerous workers were specially 

 trained for this investigation, on the protozoological side, and in 

 due course trustworthy figures were obtained for determining 

 the incidence of infections with various intestinal protozoa among 

 the particular class of case studied. The results have already 

 been published in an earlier Report,^ and elsewhere, and need 

 not be further considered here. It will suffice to note that 

 these returned soldiers were infected, to a considerable degree, 

 not only with the common and well-known non-pathogenic 

 intestinal protozoa, but also, and in a somewhat surprisingly high 

 proportion, with Entamoeba histolytica — the 'dysentery amoeba'. 



It was known before the War — chiefly through E. L. "Walker's 

 observations and experiments in the Philippines — that carriers 

 of H. histolytica are not uncommon. Such persons, though 

 harbouring active and facultatively pathogenic amoebae in the 

 walls of their intestines, may present no clinical symptoms of 

 infection : and they are, in consequence, indistinguishable from 

 uninfected individuals unless their stools are subjected to careful 

 microscopic examination. In 1914 it was still uncertain what 

 percentage of persons who become infected with E. histolytica 

 naight be expected to develop into carriers of this type, and what 

 proportion might be expected to suffer from dysentery or liver 

 abscess, or to display other clinical signs of amoebiasis. Con- 

 sequently, it was impossible to state, with any certainty, the 

 precise significance of the high rate of infection with -E. histolytica 

 discovered in the convalescent dysenteric patients returning to 

 Britain from the various theatres of war. 



It soon became clear, therefore, that further facts, obtained 

 from a different class of persons, were necessary for the proper 

 comprehension of those already accumulated. The mere fact that 

 some 25 per cent, of dysenteric convalescents, returned from 

 Gallipoli or elsewhere, were infected with E. histolytica told us 

 very little : for we were not told how many non-dysenteric cases 

 from the same area were infected, nor what percentage — if any — 

 of the whole body of troops was parasitized before setting out 

 from England originally. In other • words, we were presented 

 with the end result of an experiment in which the earlier steps 

 were unknown, and alongside of which no control experiments 

 had been performed. 



The first steps towards acquiring the necessary knowledge 

 were taken early in 1916, when an attempt was made to examine 

 the stools of soldiers invalided to England for disabilities other 

 than dysentery. In those days it was difficult to examine non- 

 dysenteric patients, as there were large numbers of dysenteric 

 convalescents — whose diagnosis and treatment were urgent, on 

 military grounds — awaiting examination in the hospitals and 

 d^p6ts in this country. I succeeded,* however, in investigating 

 some cases of the former class at No. 2 New Zealand General 

 Hospital, Walton-on-Thames. The number was not great, but 

 the results were somewhat surprising. I examined altogether 



' See Dubell (1917). » See Dobell (1916\ 



(4131) A 3 



