538 
Entamoeba gingivalis 
From the first we were not convinced that the mere association of 
an organism with a particular set of circumstances in a certain per¬ 
centage of cases is proof that we are dealing with cause and effect. 
Nor, when yielding to the inhibitory effects of some specific reagent 
the organism disappears, and pari passu, the abnormal circumstances 
also show a tendency to disappear, can we yet agree that the association 
of one with another as cause and effect has been definitely established. 
So far, all attempts to reproduce the disease by inoculation of 
healthy tissues with discharge containing amoebae have failed. In 
regard to treatment, if we grant that certain cases do well with emetine 
after having proved refractory to all other methods, it remains still to 
be proved that the improvement is due to the amoebicidal action of the 
drug and not to some other possible effect, such (as has been suggested) 
as its bactericidal action or its possible beneficial effect upon the phago¬ 
cytic function of the leucocytes. 
It is unnecessary for us in this paper to discuss the nomenclature 
of Eniamoeha gingivalis nor need we discuss the historical aspect of the 
question; all this has been done quite recently and very thoroughly in 
one or two papers dealing with this problem, e.g. Smith and Barrett 
(1915 b) and Craig (1916). 
We have contented ourselves with two principal lines of attack on 
the problem. First, a careful investigation into the structure of the 
amoeba by exact cytological methods, particular attention being 
directed to the nature of the inclusions, and, second, an examination 
of a number of mouths, some healthy, others showing a variety of 
pathological conditions. 
We have not attempted to investigate the conditions influencing 
the trophic existence of the amoeba, as for example, the effect of the 
saliva as regards the amount secreted and its chemical composition, or 
the influence of the fermentative changes proceeding in the buccal cavity. 
Methods. 
(a) Observation on the living organism. 
For making observations on the living amoebae we have employed 
the warm stage with success. 
We have found it convenient to make our preparations for examina¬ 
tion under these conditions as hanging-drops on cover-slips placed over 
cavity slides and sealed with wax. By employing this method it is 
possible to lift the cover-slip after making observations and fix off the 
preparation at any desired moment. 
