VIII, B, 4 Walker and Sellards: Entamoebic Dysentery 261 



dysentery; cysts of "Entamoeba tetragena" from "convalescent" 

 and "contract" carriers;'" and motile Entamoeba histolytica from 

 acute cases of entamoebic dysentery and from an entamoebic liver 

 abscess. 



Each culture of amoeba consisted of a single species of amoeba, 

 but associated with it was the mixed bacterial growth from the 

 source from which it was cultivated. No attempt was made 

 to isolate the amoebae in "pure mixed cultures" with one species 

 of bacterium ; first, on account of the difficulty of obtaining really 

 "pure mixed cultures" ; secondly, since it was impossible to 

 obtain the entamoebse in "pure mixed cultures," it was considered 

 advisable for the sake of uniformity to feed all of the amoeboid 

 organisms with mixed bacterial cultures; and, thirdly, because 

 it was found to be unnecessary. 



In the feeding experiments, the growth of amoebae scraped from 

 the surface of the culture medium and the material containing the 

 entamoebse, either alone or mixed with powdered starch or mag- 

 nesium oxide, was inclosed in gelatine capsules and ingested by 

 the men. The powdered starch served to absorb the excess of 

 moisture that would tend to dissolve the gelatine capsule and 

 to facilitate the ingestion of the material. The magnesium oxide 

 served the same purposes as the starch and, in addition, to 

 neutralize the acidity of the contents of the stomach of the ex- 

 perimental man. In every case the capsules of infective material 

 were personally administered. 



Following the ingestion of the infectious material, the stools 

 of the men were saved daily until parasitization, or the failure 

 to parasitize, with the specific amoeboid organisms was definitely 

 determined, and thereafter at frequent intervals. These stools 

 were examined culturally and microscopically for amoeboid or- 

 ganisms, and the species of such organisms, when found, was 

 carefully determined. It has not been considered sufficient to 

 determine the species of amoeboid organism fed to, and re- 

 covered from, the experimental man, but necessary to follow each 

 case carefully to guard against the possibility of double infection, 

 resulting from a previous latent infection of the man, from 

 impure material used in the feeding experiments or from a sub- 



" By "convalescent" carrier is meant a person who has suffered from 

 an attack of entamoebic dysentery and has recovered but who is still carry- 

 ing the specific entamoeba; in contrast, the "contact" carrier is a person 

 who, without having had entamoebic dysentery, is carrying the pathogenic 

 entamoeba. 



