VIII. B, 4 Walker and Sellards: Entamoebic Dysentery 267 



plant to fresh culture medium was made in every case to test 

 the viability of the cysts. 



The growth scraped from several agar-slant cultures or Petri- 

 plate cultures, sometimes alone, but more often mixed with 

 magnesium oxide to absorb the excess of moisture that would 

 dissolve the gelatine capsule and to neutralize the acidity of 

 the contents of the stomach that might prevent infection, was 

 inclosed in a gelatine capsule and ingested by a man. The mo- 

 tile amoebae were ingested as an emulsion in water with mag- 

 nesium oxide. It might be argued that the action of the gastric 

 juices was necessary to dissolve the cysts of the amoebae, and, 

 consequently, the use of magnesium oxide to neutralize the gas- 

 tric acidity in feeding the encysted amoebae would tend to prevent 

 infection. This argument would not be applicable, however, to 

 the cultivable amoebae. The cysts of these amoebae are dissolved 

 or ruptured from within whenever they are placed on fresh cul- 

 ture medium or in any medium suitable for growth, and, more- 

 over, acids are extremely antagonistic to the growth of these 

 amoebae. For these reasons there is no objection to the neutrali- 

 zation of the acidity of the stomach contents of the men used in 

 these experiments. 



Following the ingestion of cultures of amoebae, the stools of 

 the men were examined daily, both culturally and microscop- 

 ically, for amoeboid organisms until the parasitization or non- 

 parasitization with the specific amoeba was determined, and 

 thereafter at frequent intervals. 



A complete protocol is given of each man in order to put on 

 record the details of these experiments. 



Experiment I. — Man 3, aged 31 years, had been under observation in 

 the prison for six years. He gave a history of one attack of dysentery 

 of one month's duration sixteen years ago. He had not been used for 

 previous feeding experiments. Physical examination of his abdomen and 

 microscopic and cultural examinations of his stools for amoeboid organisms 

 were negative. He ingested the growth on 2 Petri-plate cultures of 

 Amosba I A, mixed with magnesium oxide. This amoeba was one of the 

 2 species isolated in culture from the Manila water supply. The culture 

 fed was an old one containing only encysted amoeba. Transplant cultures 

 made on fresh culture media to test the viability of the cysts gave a lux- 

 uriant growth of Amcefca A. This man has been under observation two 

 years and seven months since the experiment began. Cultures of his 

 stools on Musgrave and Clegg's medium and microscopic examinations of 

 his stools for amoeboid organisms have been constantly negative. No dys- 

 enteric symptoms have developed. 



Experiment II. — Man 4, aged 34 years, had been under observation in 

 the prison one year and six months. He had a negative dysenteric history, 



