552 Entamoeba gingivalis 
21. Male, 38. So-called dental ulcer on the lingual aspect of the 
left mandibular gum, caused by the chafing of a denture. Film made 
from its surface gave negative results so far as amoebae are concerned. 
22. Male, 30. A case of marginal gingivitis commencing in the 
interdental papillae, producing rapid sloughing of the latter and ex¬ 
tending along the gum margins. Amoebae very numerous. 
23. Male, aged 28. Right mandibular second molar which had 
been capped with gold became very painful and loose, with a good deal 
of inflammation in the gum aroimd it. After extraction the debris 
collected on the surface of the gold and on the roots was examined but 
no amoebae were found. 
24. Male, aged 44. A “bridge” attached by gold caps to the left 
maxillary first premolar and the third molar on the same side, was 
extracted together with the abutment teeth, on account of the Ibosen- 
ing of the latter by the gradual destruction of the bone and resorption 
of gum. No discharge was present. Debris from '-he roots, from the 
surface of the gold caps and from under the surface of the gold “ bridge ” 
was examined and in no case were amoebae found. 
Summarising the results, we have found Entamoeba gingivalis pre¬ 
sent in the majority of cases of pyorrhoea, but not in all. It is also 
present in most cases of gingivitis not associated with alveolar absorp¬ 
tion, although here also in some of our cases the organism is absent. 
In some mouths with local evidences of recession of the gum associ¬ 
ated with alveolar absorption, the amoeba was found in the diseased 
positions, and also in the healthy positions in the same mouths. We 
have found it in a case of marked hypertrophy of the gum as well as in 
cases of rapid sloughing of the margins of the gums and the inter¬ 
dental papillae. 
The organism was present in the healthy mouth of a child of two 
years old, and also in that of a man of 43.- It was not present in an 
unhealthy mouth of a boy, aged 13, with very irregular teeth, most of 
which.were rapidly succumbing to dental caries; and whose gums were 
also inflamed and bled easily (No. 3). Neither was it present in an orange- 
stained deposit on the labial surface of a lower canine in a child of 10 
(No. 4). In three other pathological conditions in the mouth (Nos. 18, 
19, 21) we have not found the organism, although cases of aphthous 
and ulcerative stomatitis and glossitis examined by Lynch (1915) gave 
positive results. 
We conclude from our examinations of the above cases that Ent¬ 
amoeba gingivalis is not the cause of pyorrhoea alveolaris, since, 
