272 The Philippine Journal of Science isis 



was still formed, but was surrounded by considerable mucus streaked with 

 blood. Microscopic examination and cultures were negative for amoeboid 

 organisms. On the thirty-sixth day his stool was partly formed and partly 

 fluid, the fluid portion consisting of mucus and blood. Three cultures of 

 the material were negative. Microscopic examination showed not ATticeba 

 G, which had been ingested by the man, but a distinct genus and species of 

 amoeboid organism, Entamoeba histolytica (part IV). The dysenteric 

 condition persisted for only two days, and he recovered without treatment. 

 Entamoeba histolytica has persisted in this man's stools up to the present 

 time, two hundred forty-one days after the beginning of the experiment. 

 During the period of observation no relapse of the dysenteric symptoms has 

 occurred. At no time has Amoeba G been found microscopically in this man's 

 stools, nor was it ever recovered in cultures after the first two days sub- 

 sequent to feeding. This man either had a previous latent infection with 

 Entamoeba histolytica, or became infected with the pathogenic entamoeba 

 subsequent to ingesting Amoeba G. 



Experiment XIV shows several things besides that which it 

 was planned to demonstrate. First, it shows the possibility of 

 latent or secondary infections with other amoeboid organisms in 

 such experiments; secondly, it emphasizes the care necessary to 

 exclude such secondary infections in experimental work ; thirdly, 

 it illustrates the chief source of error in the conclusions of pre- 

 vious experimenters; and, fourthly, it has demonstrated our 

 ability to exclude such sources of error from our experiments. 



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

 in the prison for six years and one month. He gave a history of dysentery 

 of one month's duration sixteen years ago. He had been used for 2 feeding 

 experiments with cultures of amoebae, thirty-six and twenty-four days 

 previously, respectively, with negative results (experiments I and III). 

 Physical examination of his abdomen and microscopic and cultural exami- 

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

 the growth on 4 Petri-plate cultures of Amoeba lOG, isolated from a 

 diarrhoeal stool in Kansas, mixed with magnesium oxide. The cultures 

 ingested by this man contained only encysted amoebae. Transplant cul- 

 tures made to test the viability of the cysts showed an abundant growth of 

 Am,oeba G. Following the feeding, cultures of this man's stools showed 

 a growth of Amoeba G on the second day after feeding, but never subse- 

 quently. Microscopic examinations of his stools for amoeboid organisms 

 have been constantly negative. This man has been under observation two 

 years and five and one-half months since the experiment began. During 

 this time Amoeba G has never been found microscopically in his stools, and 

 he has never shown any symptoms of dysentery. 



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

 in the prison for four years and six months. He gave a history of 4 

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

 been used for 2 previous feeding experiments (experiments XI and 

 XIII), the latter of which was thirty- four days previously, and both of 

 which were followed by negative results. Physical examination of his 

 abdomen and microscopic and cultural examinations of his stools for 



