VIII, B, 4 Walker and Sellards: Entamoebic Dysentery 293 



become parasitized with Entamoeba histolytica. In order to determine 

 whether this man possessed a relative or an absolute immunity, he ingested 

 cysts of Entamoeba histolytica a second time on the seventy-sixth day 

 after the first. The infectious material was from the same "carrier" as 

 the first ingestion, now convalescent one hundred thirty-six days, but still 

 showing encysted Entamoeba histolytica in his stools, and was mixed with 

 magnesium oxide. Following this ingestion experiment, cultures of his 

 stools were negative. Microscopic examination showed many small Enta- 

 moeba histolytica in his stools on the seventy-ninth day, or three days after 

 this second feeding, but subsequent examinations were negative. The 

 entamoebze evidently had failed again to establish themselves permanently 

 as parasites in the intestine of this man. On the one hundred second day 

 he ingested for the third time entamoebse from the same "carrier," now 

 convalescent one hundred sixty-two days. Following this ingestion experi- 

 ment, cultures of the stools of this man were negative for amoebae. Mi- 

 croscopic examination showed encysted Entamoeba histolytica on the one 

 hundred seventh day, or the fifth day after this last ingestion, and the enta- 

 moebse have persisted in his stools ever since. This man has been under 

 observation nine months since the last ingestion experiment, and he has 

 not shown any dysenteric symptoms. 



Experiment XLIII. — Man 30, aged 25 years, had been under observa- 

 tion in the prison seven years and five months. He had a negative dys- 

 enteric history, and had not been used for previous experiments. Physical 

 examination of his abdomen and cultural and microscopic examinations of 

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

 Entamoeba histolytica, strain A, mixed with magnesium oxide. Following 

 the ingestion, cultures of the stools of man 30 were negative for amoebae. 

 Microscopic examination of his stools showed encysted Entamoeba histo- 

 lytica on the day following the ingestion, and the entamcebae have per- 

 sisted in his stools ever since. On the ninety-fifth day a stool from this 

 man was semifluid and greenish, contained mucus, a little blood, and many 

 motile and resting Entamoeba histolytica, some of which contained red 

 blood corpuscles. No examination of his stools had been made for six days 

 previously, and another stool was not obtained until the second day after 

 this examination. At the former examination the stool was soft and no 

 entamoebas were found; at the latter examination the stool was formed 

 and contained a few encysted entamoebce. Entamoeba histolytica had been 

 found in his stools eight days previous to this slight attack of dysentery. 

 Physical examination of this man was negative. He has been under 

 observation one year since the beginning of the experiment. No relapse 

 of the dysentery has occurred, but the entamcebae have persisted in his 

 stools. 



ENTAMCEBA HISTOLYTICA, STRAIN A, SECOND PASSAGE, SERIES 1 



In this series of experiments strain A of Entamceba histolytica 

 had been passed from the original case, convalescent sixty days 

 from an attack of spontaneous entamoebic dysentery, through 

 man 2. Man 2 had been infected one hundred forty-four days 

 previously with strain A, had developed an attack of entamoebic 

 dysentery one hundred twenty-five days, with a relapse seventy- 

 four days, previously (experiment XLI), and was now a "con- 



