274 WALKER. 



refrangent appearance, distinct nucleus and sluggish motility, in the 

 living entamoeba ; by the deeply staining, granular cytoplasm, and by the 

 relatively large amount of chromatin, which is an-anged either as a 

 heavy continuous or broken ring (coli variety) or as several discrete 

 masses (nipponica variety) on the inner surface of the nuclear membrane, 

 with transitions between these two varieties, in the stained entamoebas ; 

 and especially by the development of cysts containing 8 nuclei. This 

 species should, according to the law of priority, bear the name of 

 Entamoeba coli Schaudinn. It is found in the stools of healthy persons 

 and of persons suffering from diseases other than dysentery and is, there- 

 fore, presumably non-pathogenic. The other species include the his- 

 tolytica variety of Schaudinn, the tetragina variety of Viereck and 

 Hartmann and probably the minuta variety of Elmassian. It is charac- 

 terized by its hyaline and feebly refrangent appearance, indistinct nu- 

 cleus, and active motility in the living entamoeba: by the feebly-staining 

 reticulated cytoplasm, and by the relative paucity of chromatin which is 

 ai'ianged either as a barely perceptible layer about the inner surface of 

 the nuclear membrane with or without a few fragments scattered in the 

 nuclear network (histolytica variety), or as a more extensive but loose, 

 granular peripheral layer and a loose central karyosome (tetragina varie- 

 ty V with transitions between these two varieties in the stained enta- 

 moeba; and especially by the development of cysts containing 4 nuclei. 

 This species is found only in the stools, pus, or tissues of cases of 

 amoebic dysentery, amoebic liver-abscesses, or of eases having a history of 

 amoebic dysentery and is probably a pathogenic species. According to 

 the law of priority this species should bear the name, Entamwba histolytica 

 Schaudinn. The differences in the arrangement of the chromatin in 

 the nuclei of the coli and nipponica varieties and of the histolytica and 

 tetragina varieties probably represent metabolic or repi'oductive changes 

 in the nuclei of the two species. This view is supported by the presence 

 of forms showing a chromatin arrangement intermediate between these 

 varieties of the two species. It is probably that other imperfectly de- 

 scribed species of Entamceba that have been observed in the intestine of 

 man would be found, on a more complete knowledge of their morphol- 

 ogy and life-cycles, to belong to one or the other of these two species. 



The most important practical application of these differences in mor- 

 phology between Entamoeba coli and Entamoeba histolytica is the micro- 

 scopic diagnosis of amoebic dysentery, especially in incipient or chronic 

 cases, as a guide to treatment and prophylaxis.^ The differentiation of 



' It is to be noted in this connection that the raicroseopic diagnosis of amoebic 

 dysentery is not dependent iipon Entamccba hystolytica being the primary 

 etiologic factor in this disease, but only upon the apparently constant association 

 of this entamoeba with amoebic dysentery. 



