VIII, B, 4 Walker and Sellards: Entamcebic Dysentery 291 



less frequent occurrence in the stools of healthy persons and 

 their constant presence in the stools of cases of endemic tropical 

 dysentery (compare figs. 5 to 8 with figs. 3 and 4, Plate I). 



In the following series of experiments 20 men have ingested 

 material containing Eyitamoeha histolytica. Four of these men 

 had a history of attacks of dysentery from six to sixteen years 

 previously ; the other 16 had negative dysenteric histories. Four 

 of the men had been used previously for ingestion experiments 

 with cultures of amoebse with negative results. All of the men 

 were free from dysenteric symptoms, and their stools were proved 

 to be free from amceboid organisms by cultures on Musgrave and 

 Clegg's medium and by microscopic examinations before being 

 used for these experiments. 



The entamoebse ingested by these men were from 7 different 

 sources and represented 4 distinct strains of Entamceha his- 

 tolytica. The history of these strains will be given in connection 

 with the protocols of the experiments. 



The material containing Entamoeba histolytica, as in the case 

 of the Anioebx and Entamoeba coli, was mixed with powdered 

 starch or magnesium oxide, inclosed in a gelatine capsule, and in- 

 gested by the experimental men. In cases where motile enta- 

 moebse were ingested and it was consequently undesirable to absorb 

 the moisture of the material, the infectious material was inclosed 

 in a small gelatine capsule and this inclosed in a larger gelatine 

 capsule containing magnesium oxide. The use of magnesium 

 oxide to neutralize the acidity of the contents of the stomach in 

 the experiments with Entamoeba histolytica was in order to 

 secure parasitization with the motile entamoebse and to insure 

 infection with any possibly pathogenic microorganisms that 

 might be associated with the entamoebse and be the primary 

 etiologic agent in the production of dysentery, especially in the 

 control cases that did not become parasitized with Entamoeba 

 histolytica. 



Cultures and microscopic examinations were made daily of 

 the stools of the men after ingesting the infectious material 

 until parasitization or nonparasitization with Entamoeba histo- 

 lytica was determined, and thereafter at frequent intervals. In 

 every case the species of amoeboid organism found by either 

 method of examination was carefully determined. Clinical 

 symptoms of dysentery were carefully watched for, and men 

 who developed dysentery received ipecac treatment as soon as 

 the diagnosis of entamoebic dysentery was clinically and micro- 

 scopically established. Treatment of the cases of dysentery was 



