126 PARASITIC AMCEBJS OF MAN. 



In some amoebse the vacuoles comprise nearly all 

 of the substance of the organism, the ectoplasm being 

 invisible, while the endoplasm consists merely of a 

 network enclosing the numerous vacuoles. Such 

 amoeba? are undoubtedly undergoing degeneration, 

 for though they may retain their motility for some 

 time, it will be observed they eventually undergo 

 fragmentation. The significance of the vacuoles in 

 Entamceba histolytica is still uncertain. The pres- 

 ence of various substances within them suggests that 

 they have something to do with digestion, but the 

 absence of contractility places them apart from the 

 class of contractile vacuoles which are present in 

 many free-living amoebae. However, it is probable 

 that they have a distinct function, although when 

 they are present in large numbers I believe that they 

 are due to degeneration of the cytoplasm. 



One of the most characteristic biological features 

 of Entamceba Mstolytica is its power of phagocyting 

 the red blood corpuscles of its host. This property 

 can be easily demonstrated by adding fresh blood to 

 specimens of feces containing motile amoebae, and 

 there can be no doubt but that the red corpuscles are 

 digested within the parasites. These cells are very 

 commonly observed within this species, not only when 

 the feces contain blood, but often in cases where there 

 is no macroscopic evidence of its presence. The 



