118 PARASITIC AMOEBAE OF MAN. 



The size of this species is of some value in differen- 

 tiating it from other amoebae, especially Entamoeba 

 coli, but it cannot be depended upon alone. Large 

 and small amoeba? occur in almost every specimen of 

 feces examined, so that a classification based upon 

 size alone must be erroneous. Some investigators 

 have endeavored to make the distinction into patho- 

 genic and non-pathogenic amoebse rest simply upon 

 the size of the organism, the larger organisms being 

 classed as pathogenic, and the smaller as non-patho- 

 genic. From my experience I cannot agree with 

 these conclusions. Careful examination of the feces 

 of cases of amoebic dysentery often show that amoebae 

 of large size are not always present, while in other 

 cases both large and small amoebae belonging to this 

 species are found. I am free to confess that as a rule 

 the majority of the organisms are approximately of 

 the same size in most specimens of feces, but this does 

 not prove anything more than that they are nearly all 

 in the same stage of development. I have repeatedly 

 observed cases of dysentery in which the vast ma- 

 jority of the amoebae present in the feces were much 

 smaller than the average given for Entamoeba histo- 

 lytica, but in which the clinical symptoms were the 

 same as in the cases where the larger amoebse were 

 found, while the morphology of the organisms was 

 identical with that of Entamoeba histolytica. 



