364 Jacob Parsons Schaeffer. 
sac and the resorption of surrounding tissue. These two pro- 
cesses taking place pari passu with the growth of the face. 
6. In a fetus at term the ventrodorsal measurement of the 
sinus is about 7 mm., and in a child aged 20 months it is about 
20 mm. The cavity reaches its full, size from the fourteenth to 
the eighteenth year. 
7. The following may be given as average measurements of 
the adult sinus maxillaris, based on the measurements of 90 
adult specimens: 
MM 
i ~ Dorsosuperiordingonal.:. \ ese.) cee See oe eine 38 
2; Ventrosuperior-diagonal. 17 Ae Gee ee 38.5 
@ - PUPSTOIMLEDION . 5 1.55 ore eee eal eens kN ae eae 33 
4: N emibrodorsale 5 5 50 5 50h it ee ee ES ee, eee 34 
5° Mediolatenalr sc 2.35). cee San ee are ee ee ae ee 23 
8. The range in capacity of the sinuses studied to ascertain 
this fact was from 9.5 ce. to 20 ee.; with an average of 14.75 ee. 
9. In the majority of cases the sinus floor is-at an inferior 
level to the nasal floor. This distance varies from one-half to 
10mm. Sex has little influence on this relation. 
10. The number of teeth that bear a direct relation to the 
sinus is inconstant, due to the great difference in the size of the 
cavity in different individuals. The three most constant teeth 
in direct relation are the three molars. 
11. The tooth fangs may cause the formation of elevations 
on the sinus floor. Occasionally the fangs of some teeth are in 
direct communication with the mucous membrane of the cavity. 
12, Frequently the walls of the sinus are uneven, due to 
ridges, or crescentic projections. These prominences form pockets 
and recesses within the cavity. Occasionally the cavity is divided 
by a septum into two distinctly separate compartments, each 
having an independent opening into the nasal fossa, but not 
communicating with each other. 
13. The adult sinus varies much in size in different individuals, 
and the asymmetry on the two sides of the same individual is 
often marked. 
14. Age, sex, and side influence the size of the adult sinus 
but little. 
