266 The Philippine Journal of Science wis 



mixed growth of bacteria with which they had been isolated. 

 The presence of bacteria growing with the amoebae in mixed 

 cultures would be objectionable only if the experiments were 

 followed by the development of dysentery, and since all of the 

 cultures of amoebje were confirmed to be neither pathogenic nor 

 parasitic this objection has no foundation. 



The 20 experiments were made on 10 different men, some of 

 them being used for several successive experiments. When the 

 ingested organism failed to parasitize the man, he was used, 

 after the lapse of a sufficient interval and after repeated nega- 

 tive cultural and microscopic examinations of his stools, to 

 repeat the experiment with the same or a different amoeboid or- 

 ganism. Since the species of amoeba ingested could in every 

 case be identified microscopically, the use of the man subse- 

 quently for feeding another species of amoeboid organism in no 

 way interfered with the continued observation of him with ref- 

 erence to the former experiment. Such men were in certain 

 respects more desirable for subsequent experiments than new 

 men, for they had been under more immediate observation and 

 the possibility of previous amoebic infection had been more cer- 

 tainly excluded by the large number of cultural and microscopic 

 examinations that had been made of their stools. 



Some of the men used in these experiments gave a history of 

 one or more attacks of dysentery at some earlier periods of their 

 lives. Their present condition with reference to dysentery or 

 amoebic infection was determined by physical examination and 

 by cultural and microscopic examination of their stools. The 

 microscopic examinations were made both before and after the 

 administration of a saline purgative. With one exception, men 

 showing any evidence of amoebic infection by either method were 

 excluded from the experiments. One man was already infected 

 with Entamoeba coli when employed for a feeding experiment 

 with a culture of amoebse. Use was made of him to control our 

 differentiation of the amoebas from the entamcebje by cultural 

 and microscopic examinations. 



The amoebse were fed for the most part in the encysted condi- 

 tion, since this is the resistant stage and seemed most likely to 

 be capable of infecting the men. In a few cases they were fed 

 in the amoeboid stage. Some precautions were necessary in 

 the latter case to eliminate the presence of the encysted amoebse. 

 This was accomplished by making several successive transplants 

 of the cultures to fresh medium at from fifteen to eighteen hours' 

 interval; for it is only in old cultures that the amoebse become 

 encysted. In feeding experiments with encysted amoeba, a trans- 



