VIII, B, 4 Walker and Sellards: Entamoebic Dysentery 285 



day after ingestion and more or less constantly thereafter. No symptoms 

 of dysentery have developed. 



Experiment XL. — Man 28, aged 30 years, had been under observation 

 in the prison six years and eleven months. He had not been used previously 

 for experiments. He had a negative dysenteric history. No physical 

 examination was made of his abdomen. Cultural and microscopic examina- 

 tions of his stools for amoeboid organisms were negative. He ingested cysts 

 of Entamoeba coli, strain E, mixed with powdered starch. This man has 

 been under observation eight months since this experiment began. Cul- 

 tures of his stools for amoebae have been constantly negative. Microscopic 

 examinations showed Entamoeba coli in his stools on the second day after 

 ingestion and more or less constantly thereafter. No symptoms of dys- 

 entery have developed. 



The protocols of these experiments with Entamoeba coli are 

 summarized in Table II. 



The results of the experiments with Entamoeba coli present 

 a striking contrast to those obtained after feeding cultures of 

 amoebae (part II). The Amoebse were, with the exception of 2 

 species, always recovered in cultures on Musgrave and Clegg's 

 medium from the stools of the men the first few days after 

 feeding; while similar cultures of the stools of men who had 

 ingested Entamoeba coli have been invariably negative. Further- 

 more, the Amoebse could never be found microscopically in the 

 stools of the men who had ingested them; on the other hand, 

 Entamoeba coli has been found microscopically, after a short 

 incubation period, in the stools of every man who became para- 

 sitized (88 per cent of the men), and the entamoebse have 

 persisted in the stools for an indefinite time. 



Of the 20 men who ingested Entamoeba coli, 17 became para- 

 sitized after the first feeding and 3, who did not become para- 

 sitized, were reserved as controls. Of the 12 men who ingested 

 the entamoebse mixed with powdered starch and of the 8 men 

 who ingested the entamoeba mixed with magnesium oxide, 11 

 and 6, I'espectively, became parasitized. 



The incubation period of Entamoeba coli, that is, the time 

 elapsing from the day of ingestion to the appearance of the 

 entamoebse in the stools of the men, as determined by the 20 

 experiments, varies from one to eleven days, with an average 

 of 4.7 days. 



None of the 17 men experimentally parasitized with Entamoeba 

 coli nor the 3 nonparasitized controls have developed any symp- 

 toms of dysentery, although some of these have been under 

 observation for two years and five months. 



From the uniform results obtained in these experiments with 



119781 3 



