544 
Entamoeba giiigivalis 
food vacuoles. They go on to state that the food bodies in the amoebae 
exhibit the staining reactions of nuclear substance with haematoxylin 
and iron-haematoxylin. 
We may usefully point out here what has been mentioned already, 
that in none of our observations either on the living organisms or on 
stained material have we found any evidence whatever in support of 
Prowazek’s statement that the amoeba ingests leucocytes, if by this 
word is meant polymorphonuclear leucocytes. 
Smith and Barrett (1915 a, p. 166) say that in the endosarc there 
are many digestion vacuoles in which globular detritus of leucocytic 
nuclei and red blood cells are commonly found along with bacteria. 
Craig (1916, p. 230) says that not all the ingesta are of leucocytic 
origin, and puts forward the suggestion that those round bodies which 
stain deeply with iron-haematoxylin and are surrounded by a clear 
zone, represent some form of yeast or protozoan organism, and are not 
of leucocytic origin. He also mentions that it has not been his experi¬ 
ence to observe ingested red corpuscles in the endoplasm, even where 
the surrounding medium contains red blood cells. 
Colyer (1916, p. 52) gives points for and against the amoeba being 
the cause of the disease. Among the points in its favour he speaks of 
“its power to phagocyte red cells, a power not possessed to any degree 
by free-living amoebae.” 
From this short account of previous work on the subject it will be 
seen that there is no agi-eement as to the real nature of the ingesta, 
except that most of the authors mention leucocytes or leucocytic 
remains, whilst two consider that red cells may be among the ingesta. 
The word leucocyte has a wide connotation, and it was therefore neces¬ 
sary for us to carry the matter still further, and obtain as far as possible 
accurate information on this point. We have made a careful attempt 
to determine the real nature of these bodies, because we realised that 
upon the elucidation of this point depended, to a large extent, the answer 
to the question whether or no gingivalis is a true parasite of patho¬ 
genic importance. 
The ingesta within the amoeba are seen to consist principally of 
two constituents, bacteria and larger bodies of various shapes and sizes, 
but most frequently round or oval in outline. These bodies are by far 
the commonest constituent of the ingesta, though one may occasionally 
encounter amoebae without any food bodies at all. Again, other amoebae 
are found showing only bacteria within them (PI. XX, fig. 3), either 
lying singly or in groups within vacuoles, and one not uncommonly 
