viii, B. 4 Walker and Sellards: Entamcebic Dysentery 299 



Experiment LIX. — Man 40, aged 25 years, had been under observation 

 in the prison eight years and eight months. He had a negative dysenteric 

 history. No physical examination of his abdomen was made. He had not 

 been used for previous experiments. Microscopic and cultural examina- 

 tions of his stools Vfere negative for amoeboid organisms. He ingested 

 cysts of Entamceba histolytica, strain D, mixed with powdered starch. 

 Cultures of the stools of man 40 after the ingestion were negative. Mi- 

 croscopic examination of his stools showed Entamoeba histolytica on the 

 eleventh day after the experiment began and more or less constantly there- 

 after. Since then he has been under observation one year, but has had no 

 symptoms of dysentery. 



Experiment LX. — Man 39, aged 32 years, had been under observation 

 in the prison six years and two months. He had a negative dysenteric 

 history. No physical examination of his abdomen was made. He had 

 not been used previously for experiments. Microscopic and cultural ex- 

 aminations of his stools were negative for amceboid organisms. He in- 

 gested cysts of Entamceba histolytica, strain D, mixed with powdered 

 starch. Cultures of the stools of man 39 following the ingestion were 

 negative. Microscopic examination of his stools showed Entamoeba his- 

 tolytica on the eleventh day after feeding and more or less constantly ever 

 since. On the eighty-seventh day this man had a slight dysentery with 

 abdominal pain and motile Entamoeba histolytica in his bloody mucous 

 stools, which lasted only one day and from which he recovered without 

 treatment. He has been under observation one year since the beginning of 

 the experiment, but has had no relapse of the dysentery. 



These protocols are summarized in Table III. 



As the protocols and Table III show, amoeboid organisms could 

 not be recovered in cultures on Musgrave and Clegg's medium 

 from the stools of any of the men who had ingested Entamoeba 

 histolytica. On the other hand, Entamoeba histolytica has been 

 found microscopically in the stools of every man whq became 

 parasitized, and the entamoebse have persisted in the stools of 

 these men for an indefinite time. Therefore, it is demonstrated 

 experimentally that Entamoeba histolytica, like Entamoeba coli, 

 and in contrast to the Amoebse, is an obligatory parasite which 

 cannot be cultivated on Musgrave and Clegg's medium. 



Of the 20 men who ingested Entamoeba histolytica, 17 became 

 parasitized at the first feeding, 1 required 3 successive feedings 

 before becoming permanently parasitized, and 2, who did not 

 become parasitized at the first feeding, were reserved as 

 controls. Of the 16 men who ingested encysted Entamoeba 

 histolytica, 14, or 85.5 per cent, and of the 4 men who 

 ingested motile Entamoeba histolytica, 3, or 75 per cent, became 

 parasitized. However, all of the men who ingested motile enta- 

 moebse had the acidity of the contents of their stomachs neutral- 

 ized with magnesium oxide. It is doubtful whether so large a 

 percentage of them would become parasitized under natural con- 



