COMPARATIVE STUDY OF AMOEBA. 273 



Cysts of the tetragina type then appeared in the stools. On June 1 the 

 patient suffered a relapse with some mncns, pus, and blood in the stools 

 and typical Entamosha histolytica were present in the stools. This condi- 

 tion has persisted intermittently in spite of treatment with ipecac nntil 

 August 1 when the stools became free from mucus and blood. On August 

 7 they had become formed and the 4-nuclear cysts again appeared in the 

 fgeces. 



The cysts containing 4 nuclei found in the stools of cases of amoebic 

 dysentery, like the cysts containing 8 nuclei in non-dysenteric stools, are 

 developed only in the intestinal tract of the host and not in the defecated 

 stools. They differ from the 8-nuclear cysts in non-dysenteric stools, 

 not alone in the different number of nuclei contained in the mature 

 cysts, but, also, in a number of other particulars. The cysts are smaller ; 

 the nuclei are larger and contain more chromatin; the multiplication of 

 the nuclei appears to take place earlier in the encystment of the entamoeba, 

 often even in the amoeboid stage; the cyst wall, although equally im- 

 perveous to stains, appears not to be so thick or well defined; and the 

 encysting entamoeba more frequently contains elongated refrangent bodies 

 which stain deeply with iron hematoxylin, but which do not stain with 

 the more precise aqueous alum hematoxylin, and which, therefore, are 

 probably protoplasmic or foreign bodies rather than chromatin. (Com- 

 pare fig. 11 with fig. 16.) In the development of these cysts, as in the 

 development of the cysts from non-dysenteric stools, no indication of 

 nuclear reduction and autogamy such as is described by Hartmann in the 

 development of the cysts of Entamceba tetragina, have been observed, but 

 only uncomplicated nuclear division (figs. 14 to 16). If these observa- 

 tions be correct then these cysts, like the cysts of Entamceba coli^ would 

 have to be considered either schizogenic or possibly gametogenic rather 

 than sporogenic. 



Entamcebae of the histolytica and the tetragina varieties have been 

 found only in the stools or tissues of persons suffering from or having a 

 history of amoebic dysentery. The histolytica type I find, contrary to 

 Whitmore (1911), to be the more common variety in the dysenteries 

 of Manila. The tetragina variety when found, invariably has been- asso- 

 ciated with the histolytica and transitional forms between the two 

 varieties are common. Moreover the tetragina cysts, as the protocols of 

 the above cited cases show, have been found associated with pure his- 

 tolytica infections. 



In view of the observations that have been presented in detail in the 

 preceding pages I am of the opinion that, although several of the varieties 

 of entamoeba hitherto described are represented, only two well defined 

 species are found parasitic in the intestinal tract of man. One of these 

 species includes the coli variety of Schaudinn and the nipponica variety 

 of Koidzumi. This species is characterized by its porcelaneous and 



