AMCEBJE OF THE INTESTINAL TRACT. 99 



Motility. Entamoeba coli may be described as a 

 sluggishly motile amoeba in which this property is 

 often absent, and when present, is of slight duration 

 and very limited in extent. Motility is made possible 

 by the extrusion of pseudopodia composed of ecto- 

 plasm, the character of which has already been de- 

 scribed, but it may be recalled that they are small and 

 rounded in contour and less refractile to light than 

 is the endoplasm, while in many instances it is im- 

 possible to distinguish the boundary between the pseu- 

 dopodium and the endoplasm, even when the organism 

 is moving. Motility is always most marked in freshly 

 voided f eces and is seldom observed in f eces which has 

 stood at room temperature for more than one hour. 



Two forms of motility are frequently observed; 

 the first consisting in the extrusion of pseudopodia 

 into which flows the endoplasm, thus producing a very 

 sluggish progressive motion; the second, consisting 

 in the extrusion of pseudopodia from different por- 

 tions of the periphery at the same time, thus causing 

 a change in the shape of the organism, but no pro- 

 gressive motion. 



The sluggish motility of this species of amoeba 

 when compared with the active motility of such species 

 as Entamoeba lustolytica and Entamoeba tetragena 

 is of considerable value in differentiation, for one 

 never observes in Entamoeba coli a progressive motion 



