276 The Philippine Journal of Science im 



other men in whom this entamoeba maintained its characters of 

 noncultivability and persistence microscopically in the stools and 

 in some of whom dysentery has developed. 



This case well illustrates the erroneous conclusions that have 

 been drawn from experiments by investigators who have neg- 

 lected to determine the species of amoeboid organism fed to, 

 and recovered from, the experimental animal. This man ap- 

 parently either had a latent infection with Entamoeba histolytica 

 or had become infected with this entamoeba after ingesting the 

 culture of Amoeba G. If the species of the amoeboid organisms 

 fed to this man, and that recovered in his stools during the attack 

 of dysentery, had not been determined, and if the case had not 

 been carefully followed with daily microscopic and cultural ex- 

 aminations, the conclusions would have been inevitable that 

 Amoeba G, cultivated from a diarrhoeal stool in Kansas, was 

 capable of producing entamcebic dysentery in man. As it is, 

 we are in position to make the unqualified statement that Amoeba 

 G had nothing to do with the development of dysentery in this 

 man ; and, moreover, that Amoeba G is not only not pathogenic, 

 but that it is incapable of living as a parasite in the intestine 

 of man. 



In view of the fact that it has not been found possible to pro- 

 duce dysentery in man by 20 ingestion experiments made with 

 13 strains of 8 species of amoebae cultivated from a variety of 

 nonparasitic sources and from normal and dysenteric stools 

 and that it has been demonstrated experimentally that none of 

 these amoebse are capable of living parasitically in the intestinal 

 tract of man, the conclusion appears warranted that the Amoebse 

 play no part in the etiology of endemic tropical dysentery. The 

 sound basis of this conclusion will be more evident when we 

 consider the behavior of the Entamoebse in the human intestine. 



PART III. FEEDING EXPERIMENTS WITH ENTAMCEBA COLI 



By Ernest Linwood Walker and Andrew Watson Sellakds 



It has been shown in a previous paper by one of us (Walker, 

 1911) that the amoeboid organisms, living parasitically in the 

 intestinal tract of man and other animals, differ morphologically 

 and biologically from those found in water and soil, and occasion- 

 ally cultivable from fseces, sufficiently to justify the establish- 

 ment of the genus Entamoeba by Cassagrandi and Barbagallo 

 (1897) for the former species. Morphologically the parasitic 

 Entamoebse are differentiated from the nonparasitic Amoebx by 

 the absence of a contractile vacuole, by the eccentric instead of 



