COMPARATIVE STUDY OF AMOEBA. 275 



Entamoeba histolytica from Entamaha coli must frequently be made 

 without the help of the characteristic encysted stages. While the diag- 

 nosis in the trophozoite stage is not easy, it can be made with certainty 

 by a protozoologist having sufficient experience and using proper care. 

 The examinations for this purpose should be made of perfectly fresh 

 stools, repeated if necessary on different days, and should be made, if any 

 uncertainty exists, of stained as well as of fresh preparations. Prepara- 

 tions fixed wet in Zenker's fluid and stained with aqueous alum hema- 

 toxylin should be employed for this purpose. Greater difficulty may be 

 experienced in diagnosing chronic cases between the periods of exacerba- 

 tion of the acute symptoms, in which Entamaeha histolytica, in prepara- 

 tion for encystment more closely resembles in some respects Entamoeba 

 coli; but under these conditions a careful search will usually disclose the 

 presence of 4-nuclear cysts. The presence of such cysts in the stool is 

 absolutely diagnostic of Entamoeba histolytica; but a diagnosis from the 

 presence of 8-niiclear cysts in the stool must be made with caution, since 

 there might exist a double infection with Entamoeba coli and Entamoeba 

 histolytica. 



An experimental study of the parasitism and pathogenicity of the 

 species of the genera Amoeba and Entamoeba, established by this mor- 

 phologic study, has been undertaken and the results of it will be presented 

 in another paper. 



SUMMARY AND CONCLUSIONS. 



1. The amoeboid organisms found in the Manila water supply belong 

 to the genus Amoeba Ehrenberg. 



2. The amoeboid organisms cultivable from the intestinal tract of m^n, 

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

 belong to the genus Amoeba Ehrenberg. 



3. The cultivable species of the genus Amwba are not parasitic in the 

 intestinal tract of man; when obtained in cultures from the intestine 

 they probably are derived from cysts of amoebae that have been ingested 

 with water or food and have passed unchanged through the intestinal 

 tract. 



•i. The amoeboid organisms parasitic in the intestinal tract of man 

 belong to a distinct genus. Entamoeba Casagrandi and Barbagallo. 



5. The entamcebae are strict or obligatory parasites and are incapable 

 of multiplication outside of the body of their host. They can not be 

 cultivated on Musgrave and Clegg's medium. 



6. One non-pathogenic species of the genus Entamceba, Entamoeba coli 

 Schaudinn, parasitic in the intestinal tract of man, which includes En- 

 tamceba nipponicd Koidzumi, and which develops cysts containing 8 

 nuclei, is recognized. 



7. One presumably pathogenic species of the genus Entamoeba, En- 



104912 2 



