16,1 Fernandez: Focal Dental Infections 91 
With this technic we succeeded in exploring all the teeth and 
the maxillse, and thus could detect any change from the normal 
appearance of each particular tooth. 
In the interpretation of the X-ray plates, for the detection of 
apical abscess,/ one must bear in mind the relation of the natural 
cavities as, for instance, the antrum of Highmore with the supe- 
rior molars ; the nasal cavity with the superior incisors ; and the 
foramen of the inferior maxilla with the inferior premolars. 
Otherwise, any one of these natural cavities might be wrongly 
taken as a shadow produced by an abscess, and thus we might 
give an erroneous diagnosis, with serious consequences. With 
the foregoing precaution, it is relatively easy to diagnose with 
accuracy any abscess that might develop in the dental apex or 
around it, even though there are no clinical symptoms, if the 
negative shows a dark area circumscribed in the dental apex or 
in the alveolar cavity, and if this dark area is well defined and 
sharply separated from the neighboring tissues by a line of 
demarcation. 
This dark area, a very characteristic radiogram of an abscess, 
is produced by diminution of density, or decalcification and 
sometimes destruction of the dental tissue. If the dark area 
is very pronounced, almost black, we can infer the probable 
presence of pus in the alveolar cavity. It has been proved that 
the pus may become fluorescent under the influence of the X-rays, 
and this fluorescence acts as an intensifier of the radiations 
acting upon the point or site where the abscess is located, and 
as a result we observe the very pronounced dark zone in the 
negative. 
Pyorrhoea alveolaris, or Rigg’s disease, is clinically demon- 
strable ; it is nevertheless wise to remember that the presence of 
pus around the external border of the gums is not always due 
to Rigg’s disease, A careful examination will sometimes dis- 
close the cause as being the presence of calcareous deposit around 
the teeth, which may act as an irritant upon the gums and give 
rise to suppuration. 
Clinical examination, aided by the X-ray, makes diagnosis 
certain in cases of dental infection, and at the same time the 
extent of the lesion may be determined in this way. 
T. L. Gilmer and A. M. Moody are not in accord with Dr. 
C. J. Grieves, of Baltimore, and Dr. W. S. Baer, of Johns Hopkins 
University, that Staphylococcus albus or S. aureus may be the 
causative agent of apical and periapical abscesses. Through 
