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ARE ENTAMOEBA HISTOLYTICA AND ENT- 
• AMOEBA RAN ARUM THE SAME SPECIES? 
AN EXPERIMENTAL INQUIRY 1 . 
By CLIFFORD DOBELL. 
Imperial College of Science. 
(Report to the Medical Research Committee.) 
CONTENTS. 
PAGE 
Introduction .......... 294 
The Experiments ......... 296 
Discussion of Results ........ 305 
Note on the specific name of the Entamoeba of Human Amoebic 
Dysentery .......... 307 
References .......... 310 
Introduction. 
Nobody who studies the parasitic amoeba of the frog ( Entamoeba 
ranarum ) and the dysentery amoeba of man (E. histolytica) can fail to 
be struck by the remarkable resemblance between these organisms. The 
development of the former I described for the first time in 1908 and 1909, 
since when I have had exceptional opportunities of studying the latter; 
and I can state, with some confidence, that there is no constant structural 
character which will permit of a distinction being drawn between these 
two species. The active amoebae can usually be readily distinguished 
from one another by the inclusions (food bodies) in their protoplasm, 
but not by their own nuclear and cytoplasmic structure; but the pre- 
cystic amoebae, devoid of all food bodies, and the cysts, at every stage 
in their development, are so closely alike that preparations of the one 
could be used as demonstration specimens of the other. 
1 The experiments here recorded were carried out, in the spring and early summer of 
1916, at the Imperial College of Science with the aid of a grant from the Medical Research 
Committee. Publication has been delayed through pressure of other work. 
