MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 877 



Intestinal amoeba; Entamoeba coll Losch (Fig. 183) and Entamceba histolytica 

 are both parasites in the human intestine. They measure from 15^ to 30/11 in 

 diameter and, when examined in freshly passed faeces, may be seen in active 

 motion. Their cytoplasm contains a nucleus, vacuoles, and food particles. Both 

 may multiply by binary and by multiple division; the appearance of certain of the 

 encysted forms in both species indicates a process of autogamy. Both of the 

 parasitic amoebae of the human intestine produce a characteristic number 



B 



FIG. 183. Entamceba coli Losch 1875. ^-> various forms of motile amoebae, 

 D, the 8-nuclear stage; E-G, cysts with nuclear fragments; H t bursting cyst; /; 

 young motile amoebae. (After Casagrandi and Barbagalh, from Doflein.} 



of daughter amoebae in the course of their multiplication. E. coli com- 

 monly divides into eight small amoebae so that these organisms may present 

 any number of nuclei below this number and occasionally they contain several 

 more. The encysted forms of this species also divide into approximately eight 

 small amoebae. In E. histolytica the number produced as the result of division 

 is more regular; it is almost invariably four in the division both of the motile tropho- 

 zoites and of the encysted forms. The character of the division thus furnishes the 

 most certain criterion in differentiating the two species. Multiplying forms are 

 not always readily found, however, and it is necessary to take other characteristics 

 into consideration. The non-pathogenic species (E. coli) is more sluggish in its 

 movements, is generally larger, dull grayish in appearance, and has no sharp differ- 

 entiation into ectoplasm and endoplasm. E. histolytica is active, of a greenish hue 

 and the ectoplasm is well denned and very clear in portions extruded as pseudopods. 

 The nucleus in the harmless species, commonly centrally situated, is larger and shows 

 a larger amount of chromatin. The nucleus of the dysentery amcebse is smaller, 



