vin, B, i Walker and Sellards: Entamoebic Dysentery 295 



dysenteric history, and had not been used previously for experiments. 

 Physical examination of his abdomen and cultural and microscopic exam- 

 ination of his stools for amoeboid organisms were negative. This man 

 ingested encysted Entamoeba histolytica, strain A, second passage, series 2, 

 mixed with powdered starch. Cultures of the stool of man 36 after the 

 ingestion were negative for amoebae. Microscopic examination of his 

 stools showed Entamoeba histolytica on the fourth day after the ingestion. 

 This man has been under observation one year since the experiment began. 

 Entamoeba histolytica has been found constantly in his stools, but no dys- 

 entery has developed. 



Experiment XLVIII. — Man 7, aged 30 years, had been under observation 

 in the prison five years and two months. This man gave a history of 3 

 attacks of dysentery, each of one week's duration, six years ago. He had 

 been used previously for the following experiments. Two hundred forty- 

 six days previously he had ingested a culture of Amoeba 9F. Result 

 negative (part II, experiment XIII). Two hundred twenty-five days pre- 

 viously he had ingested a culture of Amoeba 8A. Result negative (part II, 

 experiment XI). Two hundred fifteen days previously he had ingested a 

 culture of Amoeba lOG. Result negative (part I, experiment XVI). One 

 hundred fifty-seven days previously he had ingested a culture of Amoeba 

 SB. Result negative (part II, experiment VI). Physical examination of 

 his abdomen and cultural and microscopic examinations of his stools for 

 amoeboid organisms were negative. He ingested cysts of Entamoeba his- 

 tolytica, strain A, second passage, series 2, mixed with powdered starch. 

 Cultures of the stools of man 7 after the ingestion were negative for 

 amcebas. Microscopic examination of his stools showed Entamoeba histo- 

 lytica on the fourth day after the ingestion. This man has been under 

 observation one year since the experiment began. The entamoebse have 

 persisted in his stools, but no dysentery has developed. 



ENTAMCEBA HISTOLYTICA, STRAIN A, THIRD PASSAGE 



The history of strain A of Entamoeba histolytica employed in 

 this series of experiments is as follov/s. Coming originally from 

 a man convalescent sixty days from a slight attack of entamoebic 

 dysentery, it has been passed through men 29 and 36. Man 

 29 had been parasitized with this strain for one hundred 

 sixty-one days, without the development of dysentery, when 

 it was passed through man 36. Man 36 had been parasit- 

 ized one hundred twenty-one days with the strain, without the 

 development of dysentery, when it was used for the present 

 series of experiments. Neither man 29 nor 36 has subsequently 

 developed symptoms of dysentery although both have shown the 

 cysts of Entamoeba histolytica more or less constantly in their 

 stools up to the present time. Therefore, this strain of enta- 

 moebas had been passed from a "convalescent carrier" through 

 2 "contact carriers" before being employed in the present series 

 of experiments. 



