THE SINUS FRONTALIS 



143 



S.1ront (media.!) 

 S.fron.t.(latera.n 



Cel. front* 



"Proc.unc, 

 N.I Mr 5. orb. 



FIG. 52. SPECIMEN TWENTY YEARS AND FIVE MONTHS OLD. (Series D, 



No. 90.) 



Posterior view of a coronal section 18 mm. posterior to the nasion. The 

 posterior walls of the sinus have been removed to show the relations of the 

 sinuses and their ostia. Note that on the right side there are two distinct 

 sinus frontales present. The more medial of these two sinuses developed from 

 a cellula frontalis, medial to the processus uncinatus, while the lateral one de- 

 veloped from the infundibulum. 1, Probe through the ostium of the medial 

 sinus frontalis, the ostium being anterior to the cellula frontalis shown in 

 illustration; S.front., sinus frontalis; Cel.front., cellula frontalis; Infund.eth., 

 infundibulum ethmoidale; C.med., concha media; Ost.max., ostium maxillare; 

 C.inf., concha inferior; S.max., sinus maxillaris; N.infraorb., nervus infra- 

 orbitalis; Proc.unc., processus uncinatus; B.eth., bulla ethmoidalis (extreme 

 anterior portion) ; Cr.gal., crista galli. 



