vm, B. 4 Walker and Sellards: Entamcebic Dysentery 325 



b. Motile Entamoeba histolytica exclusively in the dysenteric stools of 



men who had ingested "tetragena" cysts only. 



c. An alternation of "tetragena" cysts and motile Entamoeba histolytica 



several times repeated in the stools of a man who had ingested 

 "tetragena" cysts only and having attacks of dysentery alternating 

 with normal stools. 



6. Of the 18 men experimentally parasitized with Entamoeba histolytica, 



4, or 22.2 per cent, have up to the present time developed entamcebic 

 dysentery. 



7. The incubation period of the dysentery in these experimental infec- 



tions has been twenty, ninety-five, eighty-seven, and fifty-seven 

 days, respectively, with an average of 64.8 days. 



8. No cases of dysentery have developed in men who ingested Entamoeba 



histolytica from an acute case of entamcebic dysentery, from a liver 

 abscess, nor in the 2 men who ingested Entamoeba histolytica but 

 who did not become parasitized with the entamcebje. 



9. All of the experimental dysenteries have been obtained after ingest- 



ing Entamoeba histolytica from normal stools of "carriers." In 2 of 

 the cases the infection was from "contact carriers" who had not, 

 and have not subsequently, developed dysentery, and in one of the 

 latter cases three hundred seventy-one days and the passage 

 through 2 "contact carriers" intervened between the case of natural 

 and the case of experimental entamcebic dysentery. 



10. No cases of spontaneous entamcebic dysentery have occurred in this 



ward during the period of these experiments. 



11. In consequence of the results obtained in these experimental infec- 



tions of men with Entamoeba histolytica, the following conclusions 

 appear warranted: 



a. Entamoeba histolytica, like Entamoeba coli and in contrast to the 



Amoebie, is a strict or obligatory parasite and cannot be cul- 

 tivated on Musgrave and Clegg's medium. 



b. "Entamceba tetragena" Viereck is identical with Entamoeba histo- 



lytica Schaudinn, and "tetragena" cysts are developed in the life 

 cycle of Entamoeba histolytica. 



c. The large percentage of latent infections obtained in these experi- 



ments is wholly consistent with our clinical and pathological ex- 

 perience with entamcebic dysentery. 



d. Entamoeba histolytica is the essential etiologic factor in endemic 



tropical dysentery. 

 D. Information believed to be of the greatest value for the diagnosis, treat- 

 ment, and prophylaxis of entamcebic dysentery has been obtained in 

 this experimental investigation. 



1. Since it has been determined that Entamoeba histolytica is the specific 



etiologic agent, it will be possible to make an accurate laboratory 

 diagnosis of entamcebic dysentery. 



2. The distinction between the pathogenic Entamoeba histolytica and the 



harmless Entamceba coli having been established, there will no 

 longer exist an excuse for the indiscriminate treatment of all 

 persons who show entamoebae in their stools. 



3. The relatively long incubation period of this disease and the ability 



to diagnose latent infections make it possible to anticipate with 

 treatment an attack of entamcebic dysentery. 



