﻿IX, B, 1 Willets: Intestinal Parasitism 87 



other hand, may be associated with either active or encysted 

 stages — sometimes with both of them. In dysenteric stools, 

 whether they be entamoebic or of other variety, active forms 

 are encountered almost invariably in this climate if the specimen 

 be not over one hour old. In soft or in artificially produced 

 diarrhoeal stools, such as those obtained after a saline cathartic, 

 active, quiescent, and some encysted forms are found, quiescent 

 forms being the most frequent numerically. In hard, formed 

 stools only encysted stages appear ordinarily. Old, liquid, or 

 soft stools are not suitable for examination for the reason that 

 active and quiescent entamcebae degenerate and disappear within 

 a few hours. It has been my repeated experience to find such 

 specimens which I had saved in the morning for purposes of 

 demonstration to be absolutely negative in the afternoon. Hard, 

 formed stools may be examined for encysted entamoebae any 

 time within two or three days after being obtained. 



The ability to recognize active, quiescent, and encysted enta- 

 mcebje, after they have once been demonstrated to him, is readily 

 acquired by one who is familiar with stool examinations. The 

 active forms are identified by their characteristic movements. 

 Walker " has given the following description of the quiescent 

 and encysted form: 



The resting entamoeba is distinguished from other bodies found in the 

 stool by its size, distinctness, regularity of contour, degree of refractiveness, 

 and especially by its nuclear structure. The entamoebae vary in size within 

 considerable limits, but are usually from 20 to 30 microns in diameter. 

 They are, therefore, larger than pus cells, or other protozoa, with the 

 exception of Balantidiiim coli, that are found in the stools of man. They 

 are also more refractive than pus, epithelial, or other cells found in the 

 stools. The nuclear structure of the entamoebae is particularly character- 

 istic. The unencysted entamoeba possesses, unless in the process of 

 division, only a single nucleus. This nucleus is round, or occasionally 

 slightly oval or irregular, small with reference to the size of the cell, and 

 appears not solid but as a refractive ring. This relatively small, ring- 

 shaped nucleus appears to be absolutely diagnostic of an entamoeba. Only 

 one other kind of cell observed in stools possesses a nucleus in any way 

 resembling that of an entamoeba. This is an epitheloid cell, sometimes 

 found in mucous stools, which has a ring-form nucleus relatively much 

 larger than that of an entamoeba, occupying one-fourth to one-half of 

 the cell. While an entamoeba may occasionally be observed with an ab- 

 normally large nucleus, probably preparatory to division, the nucleus never 

 approaches the size of the nucleus of this epitheloid cell. The latter cells 

 are also less refractive and granular than entamoebas. 



The encysted entamoeba is round or slightly oval, more refractive than 

 the resting or motile stage, and is surrounded by a more or less distinct 



" This Journal, Sec. B (1913), 8, 310. 



