NASOFRONTAL REGION IN MAN 137 



frontalis of the meatus nasi inedius. The first (most ventral) and 

 fourth (most dorsal) frontal pits developed into two small cells. 

 The second frontal pit developed sufficiently far to be topograph- 

 ically a sinus frontalis (indicated in drawing as an anterior eth- 

 moidal cell). The sinus frontalis proper took its origin from the 

 cellula ethmoidalis anterior which had its genetic point in the 

 third frontal pit. The result of the encroachment of the cell 

 from the second frontal pit is a narrow channel (ductus naso- 

 frontalis) communicating between the sinus frontalis and the 

 recessus frontalis. As in figures 6 and 9, in figure 7 the infun- 

 dibulum ethmoidale ends blindly lateral to the recessus frontalis. 



As stated in previous paragraphs, fewer frontal pits and folds 

 are at times differentiated in the fetus. This changes the pic- 

 ture of the adult anatomy of the recessus frontalis. In figure 12 

 there is evidence of but two embryologic frontal pits. The first or 

 most ventral of the latter developed into the sinus frontalis. It 

 should be noted that the duct of the sinus frontalis is in the same 

 axis as the hiatus semilunaris and the infundibulum ethmoidale. 

 The latter terminates lateral to the recessus frontalis as a cellula 

 ethmoidalis anterior (infundibular cell). The second or dorsal 

 pit (fig. 12) developed into a small cellula ethmoidalis anterior 

 in line with the suprabullar furrow (now cellula ethmoidalis ante- 

 rior, honeycombing the bulla ethmoidalis). This same dissec- 

 tion shows a well developed dorsal limb of the processus uncina- 

 tus (x). This causes the infundibulum ethmoidale to end in a 

 deep, Wind pocket just over the ostium maxillare. 



In an earlier paragraph mention was made of occasional adult 

 specimens in which the ductus nasofrontalis is in direct con- 

 tinuity with the infundibulum ethmoidale. In figure 8 is repre- 

 sented a dissection of an adult nasofrontal region in which the 

 ventral extremity of the infundibulum ethmoidale is directly 

 continuous with the ductus nasofrontalis and secondarily with 

 the sinus frontalis. In this dissection one notes a plate of tissue 

 intervening between the free border of the processus uncinatus 

 and the bulla ethmoidalis, thus bridging over the ventral ex- 

 tremity of the infundibulum ethmoidale and, in a sense, re- 

 placing the hiatus semilunaris in this position. One encounters 



