VIII, B, 4 Walker and Sellards: Entamcebic Dysentery 821 



similar statement as a result of his experience. The purpose of 

 my experiments as performed was to obtain parasitization and 

 to secure the most favorable conditions possible for infection 

 with any other organisms that, associated with the entamoeba, 

 might be an etiologic factor in producing dysentery. In con- 

 sequence of the extremely feeble resistance of the motile Enta- 

 mceba histolytica to external influences, it is not considered that 

 cases of acute entamcebic dysentery are an important source of 

 infection. 



On the other hand, it is believed that chronic and latent cases 

 of this disease are the chief, if not the exclusive, source of infec- 

 tion in endemic regions, first, because of their relative prev- 

 alence; secondly, because this condition persists indefinitely; 

 thirdly, because their infection is unsuspected; and, fourthly, 

 because these "carriers" are constantly passing in their stools, 

 often in enormous numbers, the resistant, encysted stage of 

 Entamceba histolytica. 



From the results of my experimental infections it appears that 

 78 per cent of persons parasitized with Entamoeba histolytica 

 become "contact carriers" of the parasite. For every case of 

 dysentery obtained in these experiments, there were 5 cases of 

 latent infection; and of the 4 cases of dysentery, 2 cases were 

 chronic, and the 2 acute cases became "convalescent carriers" of 

 Entamoeba histolytica. In the examination of 101 healthy men 

 in Bilibid Prison, who had not been used for experiments, 9, or 

 8.9 per cent, were found to be "carriers" of Entamceba histolytica. 

 These men had all been in the prison for years, and it is con- 

 sequently probable that the percentage of "carriers" was lower 

 than would be found outside. 



While acute entamcebic dysentery lasts only days or weeks, 

 the chronic and latent infections persist indefinitely. None of 

 the 20 experimentally infected nor the 9 naturally infected men 

 has ceased to be a "carrier" of Entamoeba histolytica, although 

 some of them have been under observation for over two years. 

 The longest time of which I have an accurate record of a man 

 carrying Entamoeba histolytica is two years and four months, 

 and it still appears in his stools in undiminished numbers. More- 

 over, as we have seen, the ordinary routine treatment of such 

 "carriers" may not permanently remove the parasites from the 

 intestine. 



These "carriers" are constantly passing in their stools the 

 resistant, encysted stage of the pathogenic entamoeba. As has 

 been stated previously in another connection, in 930 stool exam- 

 inations of men known to be parasitized with Entamoeba histo- 



