VIII, B, 4 Walker and Sellards: Entamcehic Dysentery 303 



mouths and throats of from 53 to 100 per cent of healthy persons, 

 and that from 69 to 83 per cent of these organisms proved to be 

 virulent on inoculating them into animals. 



Therefore, it appears that the relatively small number of 

 cases of dysentery obtained up to the present time in the men 

 experimentally parasitized with Entamoeba histolytica is thor- 

 oughly consistent with our knowledge of the prevalence of latent 

 infections in this disease. It should also be borne in mind that 

 not Entamoeba histolytica alone, but all of the microorganisms 

 contained in the dysenteric stool, were fed in each case and, 

 consequently, the small percentage of dysenteries resulting from 

 these feedings has no bearing upon the etiology, but is evidence 

 only of the frequent latency, of this disease. 



To what extent this latency, which is characteristic of enta- 

 moebic dysentery, is due to the chronicity of the ulcerative 

 process, and whether or not the inability of Entamoeba histo- 

 lytica to penetrate the healthy intestinal epithelium plays a part 

 in it, cannot at present be definitely answered. In the latter 

 case the entamoeba might be conceived to live as commensals 

 in the intestine of their host, and only when there occurred some 

 depression of the natural resistance of the host or of its tissues 

 or some inflammation or actual lesions in the intestine, were 

 the entamoebse able to penetrate the intestinal epithelium, become 

 tissue parasites, and produce the characteristic lesions of enta- 

 moebic dysentery. 



It was hoped that information on this aspect of the subject 

 might be obtained by post-mortem examination of men who had 

 been parasitized for a considerable time with Entamoeba his- 

 tolytica, but who had never shown any dysenteric symptoms. 

 However, only one necropsy has been obtained. This man, 

 who had been parasitized with Entamoeba histolytica for one 

 hundred sixty-five days without showing any dysenteric symp- 

 toms, died of pulmonary and intestinal tuberculosis. Necropsy 

 showed an extensive ulceration of the small intestine and caecum 

 which was clearly tubercular. In the lower large intestine there 

 were a few small ulcers of doubtful anatomical character. Sec- 

 tions of these ulcers, however, showed no entamoebse, but only 

 large numbers of tubercle bacilli. The tubercular lesions in this 

 case would seem to have afforded openings in the intestinal 

 epithelium for the entrance of the entamcebse, but the products 

 of the tubercular ulcerations may have been inimical to the 

 entamoebse, and it is consequently unsafe to draw any conclu- 

 sions from this case. 



