130 J. PARSONS SCHAEFFER 



furrows on the medial surface of the bulla ethmoidalis. The 

 infundibulum ethmoidale dorsally and caudally gives rise to the 

 sinus maxillaris and ventrally it usually ends blindly by forming 

 a cellula ethmoidalis anterior of variable size, lateral to the 

 recessus frontalis. Various aberrant cellulae ethmoidales anterior 

 (agger, conchal, infundibular, etc.) also frequently develop 

 from the aforementioned points. The posterior or dorsal group 

 of the cellulae ethmoidales do not concern us here. 



f""^ '^^^^^^~T' - - J^fofif if I furrows or pits 

 Jicct'ssus froitfa/rs __ — \- ~ '^^^\ ^"Z '- -^ ' 



Sinv^ spTfcmoidcdis 



---------.Bulla etk. 



Fig. 4 From a term fetus. Recessus frontalis exposed by partial removal of 

 concha nasalis media. Note intimate relationship between ventral extremity of 

 the infundibulum ethmoidale and the second or most dorsal frontal furrow or 

 pit. Should the sinus frontalis develop from the second frontal furrow, the 

 adult relationship between the former and the infundibulum ethmoidale would 

 be very intimate. Indeed, there might be direct continuity, allowing for further 

 changes in development. The conclusion would be wrongly drawn, however, to 

 say that the sinus frontalis is a derivative of the infundibulum ethmoidale. 



The processus uncinatus and the folds composing the bulla 

 ethmoidalis are often in direct continuity with one or more of 

 the frontal folds or conchae (fig. 1). Again, the bulla ethmoi- 

 dalis and the processus uncinatus are fused across the ventral 

 extremity of the infundibulum ethmoidale (figs. 1 and 5). Like- 

 wise in many instances the dorsal extremity of the processus 

 uncinatus divides, in a sense, into two roots, one of which turns 

 cephalad and fuses with the bulla ethmoidalis, thus causing the 

 infundibulum ethmoidale to end in a blind pouch dorsally (fig. 8). 



The infundibulum ethmoidale and one or other of the frontal 

 furrows or pits are in the same axis in the fetus and are at times 

 contiguous (fig. 1). It must, however, here be pointed out that 



