The Sinus Maxillaris in Man. 365 
15. The adult ostium maxillare varies much in size. It is 
located in the superior and ventral part of the base of the cavity, 
and serves as a means of communication between the sinus 
maxilaris and the infundibulum ethmoidale. Occasionally it 
replaces the greater portion of the lateral wall of the infundibu- 
lum ethmoidale, and represents a slit-like aperture. The ostium 
may be duplicated. 
16. The ostium maxillare accessorium is of very frequent 
occurrence. It serves as a means of direct communication 
between the sinus maxillaris and the meatus nasi medius. In my 
series of specimens it was present in 48 per cent of cases. The 
aperture was not found in the fetus and infant, 
17. Most of the accessory ostia do not look pathological, and 
the writer believes that we must, in many cases, look elsewhere 
than to a pathological process for the determining factor in this 
condition. 
18. Of the specimens studied to ascertain the fronto-maxillary 
relations, 56 per cent showed that the infundibulum ethmoidale 
was intimately related with the nasofrontal duct or with the sinus 
frontalis directly,—in case the nasofrontal duct was wanting; 40 
per cent showed that the nasofrontal duct communicated directly 
with the meatus nasi medius—the infundibulum ethmoidale 
ending blindly or in an air cell; 2.5 per cent showed two naso- 
frontal ducts, one continuous with the infundibulum ethmoidale, 
and the other communicating with the meatus nasi medius; 
1.25 per cent showed a direct communication between the 
sinus frontalis and maxillaris. 
19. Since the infundibulum ethmoidale receives the ostium 
maxillare at its dorsal and inferior end in all cases, and the naso- 
frontal duct, or the sinus frontalis directly, at its ventral and 
superior end in over one-half the cases, it very frequently 
serves as a gutter-like channel, of varying depth and efficiency, 
communicating between the frontal region and the sinus max- 
laris. 
20. The sinus maxillaris, therefore, acts as a reservoir for 
fluids coming to the dorsal end of the infundibulum ethmoidale 
(the ostium maxillare being patent). 
