VIII, B, 4 Walker and Sellards: Entamcebic Dysentery 309 



inations. Moreover, the negative results were based on the 

 examination of a single coverslip which was often hurriedly 

 made. The examination under similar conditions of 303 stools 

 of men known to be parasitized with Entamoeba coli showed the 

 entamoeba in 171, or 56.44 per cent of the examinations; in 

 other words, in about 1 out of every 2 of such examinations. 



A further objection, that may be raised to the examination of 

 formed stools, is the fact that in such stools usually only encysted 

 entamoebse are to be found. It is an opinion generally held, and 

 which is supported by the statement in all textbooks, that a 

 positive diagnosis of entamcebic infection should never be made 

 unless motile entamoebas are observed. It is of the greatest 

 importance, however, for the diagnosis of chronic and latent 

 infections that one should be able to distinguish resting and 

 encysted entamoebae from other bodies found in faeces and to 

 differentiate the cysts of Entamoeba histolytica from those of 

 Entamoeba coli. This can be done with certainty by the experi- 

 enced protozoologist. The majority of the 1,233 examinations 

 mentioned in the preceding paragraph were made of formed 

 stools containing nonmotile and encysted, chiefly encysted, enta- 

 moebse. Moreover, it is the encysted stage of the entamoeba that 

 furnishes the most unequivocal characters for the differentia- 

 tion of the pathogenic Entamoeba histolytica from the harmless 

 Entamoeba coli. 



In the examination of liver-abscess pus for Entamoeba histo- 

 lytica, the pus first obtained after the operation usually does not 

 contain entamcebse; frequently they appear in the pus from the 

 drainage tube only after several days. The explanation of this 

 is to be found in the fact that the entamoebag are not found in 

 the pus of the abscess, but only in the tissues at the borders of 

 the abscess. Consequently, it is only when the borders of the 

 abscess begin to slough off that the entamoebge appear in the 

 drainage from the abscess. Therefore, a negative diagnosis of 

 entamcebic liver abscess should never be made except after 

 negative examinations obtained for several successive days after 

 operation. 



Dysenteric or diarrhoeal stools should be examined as soon as 

 possible after they are passed, since the motile entamoeba present 

 in such stools quickly die and disintegrate. On the other hand, 

 in the formed stools of chronic and latent infections, the encysted 

 entamoebas persist unchanged for days, and consequently the ex- 

 amination can be made at one's leisure. 



In making the examination, a small platinum loopful of the 

 fluid or semifluid material should be placed on a microscope 



