334 Jacob Parsons Schaeffer. 
cation between the fangs of the teeth and the mucous membrane 
of the sinus, due to extreme hollowing out of the processus 
alveolaris of the maxilla, occurs most frequently in the aged 
(fig. 15). This latter condition does, however, occasionally pre- 
vail in the young adult (fig. 16). That very intimate relations 
frequently exist between the teeth and the sinus maxillaris is a 
fact that we should be cognizant of, but I find that these intimate 
relations have been somewhat exaggerated by some writers. 
Fic. 10 (X .8). Photograph of a frontal section of a child’s face aged from 
16 to 18 months. Note the infraorbital canal and nerve, and the relation of the 
sinus maxillaris to the developing teeth. It will be noticed that the sinus max- 
illaris has developed sufficiently to reach beneath the orbit but that it is medial 
to the infraorbital canal. 
C. Info., = canalis infraorbitalis; S. Max., = sinus maxillaris. 
The number of teeth that bear a direct relation to the sinus 
is necessarily inconstant, as stated before. In exceptional 
cases, when the cavity is very large—especially in the line of the 
ventrosuperior diagonal, all of the teeth of the trwe maxilla may 
be in relation with the sinus (fig. 15). It is, however, only an 
occasional occurrence to have the canine in direct relation with 
the sinus. In a certain number of cases the first premolar tooth 
