THE SINUS FRONTALIS 159 



A "ductus nasofrontalis " is mentioned by many writers, 

 but we have seldom found one distinctly demonstrable. In 

 the vast majority of cases the ostium frontale communicates 

 directly with a frontal cell, with the recessus conchalis, 

 with the infundibulum ethmoidale, or with an infundibular 

 cell without the interposition of a duct (Figs. 35, 36, 38, 

 51, 53, 55, 56). In some very few instances, however, 

 where the sinus has developed either from an infundibular 

 cell or from a frontal cell which is pressed upon and narrowed 

 by the partially surrounding cells of that group, the resulting 

 constriction may resemble a duct, as in Fig. 39, and in the 

 right medial sinus in Fig. 52. In the latter figure the probe 

 shows the position of the narrowed cell, or so-called ductus 

 nasofrontalis. 



The freedom of communication between the sinus frontalis 

 and the meatus medius is often interfered with by an en- 

 larged concha media, which narrows the opening into the 

 recessus conchalis, or which comes into close contact with 

 the hiatus semilunaris. In other cases a malposed small or 

 narrowed concha may produce a similar result. In Fig. 42 

 the influence of pressure from a septal ridge, as exerted upon 

 the concha media, and the narrowing of the hiatus semilunaris 

 and the infundibulum ethmoidale, which results from the 

 change in the degree of medial inclination of the processus 

 uncinatus, is clearly shown. Slight swelling in such a case 

 would completely occlude the communication between the 

 sinus frontalis and the meatus medius. 



