VIII. B, 4 Walker and Sellards: Entamoebic Dysentery 255 



experiments of several investigators * have led them to believe 

 that amoebae from water and other nonparasitic sources are 

 capable, when taken into the intestine of man and other animals, 

 of becoming facultative parasites, and in certain cases at least 

 of causing dysenteric symptoms and ulcerative lesions in their 

 host. 



In a recent paper (Walker, 1911) I have attempted to estab- 

 lish the morphological distinction between the nonparasitic and 

 the parasitic amoeboid organisms and to differentiate the non- 

 pathogenic from the pathogenic species. The conclusions 

 reached in this morphological study include the following which 

 bear directly upon this experimental investigation. 



1. The amoeboid organisms found in the Manila water supply 

 and other nonparasitic sources belong to the genus Amoeba 

 Ehrenberg. 



2. The amoeboid organisms cultivable from the intestinal tract, 

 both of healthy persons and of cases of amoebic dysentery, also 

 belong to the genus Amoeba. 



3. The species of the genus Amoeba are not parasitic in the 

 intestinal tract of man. When obtained in cultures of stools, 

 they are probably derived from cysts of amoebae that have been 

 ingested with water or food and have passed unchanged through 

 the intestine. 



4. The amoeboid organisms parasitic in the intestinal tract of 

 man belong to a distinct genus, Entamoeba Casagrandi and Bar- 

 bagallo. 



5. The entamoebse are strict or obligatory parasites, and are 

 incapable of multiplying outside of the body of their host. They 

 cannot be cultivated on Musgrave and Clegg's medium. 



6. One nonpathogenic species. Entamoeba coli Schaudinn, para- 

 sitic in the intestinal tract of man, which includes Entamoeba 

 nipponica Koidzumi,^ and which develops cysts containing 8 (or 

 more) nuclei, is recognized. 



7. One presumably pathogenic species. Entamoeba histolytica 

 Schaudinn, which includes "Entamoeba tetragena" Viereck and 

 "Entamoeba minuta" Elmassian and which develops cysts con- 

 taining 4 nuclei, is recognized. 



'Kartulis (1891), Celli and Fiocca (1894), Musgrave and Clegg (1904), 

 Noc (1909), Williams and Gurley (1909), Greig and Wells (1911), Gaudu- 

 cheau (1912), and Chatton and Lalung-Bonnaire (1912). 



° Hartmann in a recent paper (1912) has concluded that the "nipponica" 

 type of entamoeba represents degenerative changes in either Entamoeba coli 

 or Entamoeba histolytica {"E. tetragena"). A more extended observation 

 leads me to believe that this conclusion is correct. 



