324 The Philippine Journal of Science wis 



2. Microscopic examination of the stools of men after ingesting cultures 



of amcebse have been invariably and constantly negative. 



3. None of the men who ingested cultures of amoebae have developed dys- 



entery. 



4. Therefore, the following conclusions appear to be warranted: 



a. The cultivable amoebce are incapable of living parasitically in the 



intestinal tract of man. 



b. The amcebae, when obtained in cultures from stools, intestinal con- 



tents, or liver-abscess pus, are derived either from cultural con- 

 taminations or from encysted amcebae which have been ingested 

 with water or food and have passed unchanged through the intes- 

 tinal tract. 



c. The cultivable amoebas are nonpathogenic, and consequently play no 



role in the etiology of endemic tropical dysentery. 



B. Twenty feedings with 5 strains of Entamceba coli have been given to 20 



different men with the following results: 



1. Cultures on Musgrave and Clegg's medium of the stools of men who 



have ingested Entamoeba coli have been invariably negative. 



2. On the other hand, Entam<Bba coli has been found microscopically, 



after a short incubation period, in the stools of every man who be- 

 came parasitized, and the entamoebse have persisted in the stools of 

 these men for an indefinite time. 



3. Of the 20 men who ingested Entamceba coli, 17 became parasitized at 



the first feeding and 3 who did not become parasitized were reserved 

 as controls. 



4. The incubation period of Entamoeba coli, as determined by these 



experimental parasitizations, varies from one to eleven days, with 

 an average of 4.7 days. 



5. None of the 17 men experimentally parasitized, nor the 3 nonparasitized 



controls, have developed dysentery. 



6. From these results, the following conclusions appear warranted: 



a. Entamoeba coli, unlike the Amoebm, is a strict or obligatory parasite 



and cannot be cultivated on Musgrave and Clegg's medium. 



b. Entamoeba coli is nonpathogenic, and consequently plays no role in 



the etiology of endemic tropical dysentery. 



C. Twenty feeding experiments with Entamceba histolytica have been made 



on 20 volunteers, with the following results: 



1. Cultures on Musgrave and Clegg's medium of the stools of men who 



have ingested Entamoeba histolytica have been invariably negative. 



2. Microscopic examinations, on the other hand, have shown Entamoeba 



histolytica, after a short incubation period, in the stools of every 

 man who became parasitized, and the entamoebas have persisted 

 in the stools of these men for an indefinite time. 



3. Of the 20 men who ingested Entamoeba histolytica, 17 became parasit- 



ized after the first feeding, 1 required 3 feedings before becoming 

 permanently parasitized, and 2 who did not become parasitized at the 

 first feeding were reserved as controls. 



4. The incubation period of Entamceba histolytica in these experimentally 



parasitized men has been from one to forty-four days with an aver- 

 age of nine days. 



5. In these experiments it has been possible to obtain: 



a. Encysted "Entamoeba tetragena" exclusively in the stools of men 

 who had ingested motile Entamoeba histolytica only. 



