316 The Philippine Journal of Science wis 



nucleoplasm (Plate I, fig. 3). Therefore, the nucleus of Enta- 

 mceba histolytica differs from that of Entamoeba coli in being 

 less distinct, often invisible, in the living entamoeba, and in 

 being poorer in chromatin. The "tetragena" type of Entamoeba 

 histolytica found in stools of chronic cases of dysentery has a 

 nucleus more closely resembling that of Entamoeba coli; but the 

 peripheral layer of chromatin is less dense, often shows radial 

 projections, and the karyosome is loose instead of dense in 

 structure. 



2. IN DIARRHCEAL STOOLS 



In diarrhceal stools and stools after a purgative. Entamoeba 

 histolytica is usually small, sluggishly motile or immobile, and 

 possesses a nucleus that is distinctly visible in the living enta- 

 moeba as a more or less heavy peripheral ring of chromatin 

 (Plate I, fig. 7). Therefore, it more or less closely resembles 

 Entamoeba coli. These forms appear to represent changes in 

 Entamoeba histolytica preparatory to encystment. They are 

 spoken of by Darling (1913) as the "small generation" of Enta- 

 moeba histolytica, and were mistaken by Elmassian (1909) for 

 a distinct species of Entannoeba. Although the small size in part 

 may be due to less volume, it is probable that it results in part 

 from the contraction and rounding up of the much extended 

 motile entamoeba. The increase of chromatin content of the 

 nucleus may be considered as a preparation for the multiple 

 nuclear division that is to take place in the cyst. While all stages 

 from the typical histolytica through the "tetragena" to this pre- 

 encysted stage of Entamoeba histolytica may be found in diar- 

 rhceal stools or stools after a purgative, the predominance of the 

 preencysted stage and the more or less resemblance of it to Enta- 

 moeba coli make the differentiation of the two species difficult 

 and sometimes impossible in such stools. 



3. IN FORMED STOOLS 



In formed stools both Entamoeba histolytica and Entamoeba 

 coli are present in the encysted stage, and it is this stage of the 

 entamoeba that presents the most distinctive character for mak- 

 ing a differential diagnosis. Furthermore, the identification of 

 Entamoeba histolytica in the encysted stage in formed stools is 

 extremely important for the diagnosis of chronic and latent in- 

 fections and for the control of treatment of entamoebic dysentery, 

 and constitutes one of the most efficient factors in the prophy- 

 laxis of this disease. 



