678 Jacob Parsons Schaeffer. 



and not with the infundibulum ethmoidale. If, on the other 

 hand, the frontal sinus should develop from the cell of the third 

 frontal furrow, the nasofrontal duct would practically be con- 

 tinued down to the infundibulum ethmoidale, but not directly 

 continuous with it, unless the bridge of intervening tissue were 

 resorhed as it frequently is. A frontal sinus developing from the 

 cell of the third frontal furrow would in all probability have a tor- 

 tuous nasofrontal duct, this of course depending largely on the 

 disposition of the other anterior ethmoid cells. 



In the specimen shown in fig. 38 the infundibulum ethmoidale 

 and the first frontal furrow are practically continuous with each 

 other. Should the frontal sinus develop from the first frontal 

 furrow in such a condition, the nasofrontal duct would of course 

 be directly continuous with the infundibulum ethmoidale in the 

 adult. We can not say, however, that in such a condition, the 

 sinus frontalis develops from the infundibulum ethmoidale. From 

 adult relations it would* appear as if the latter interpretation 

 were correct; embryology, however, shows the error of this con- 

 tention. If in the specimen shown in fig. 41 the frontal sinus 

 formation should take place from tlie cell of the second frontal 

 furrow, the nasofrontal duct would be continued down to the 

 infundibulum ethmoidale at an angle, but not be directly continu- 

 ous with it. In the specimen shown in fig. 43 (from a child aged 

 14 months) we find the whole frontal recess extending and devel- 

 oping into the frontal sinus. In the latter case the adult sinus 

 would in all probability have no true nasofrontal duct, but the 

 sinus would open directly into the ventral and superior portion 

 of the meatus nasi medius. 



Note the possibilities of adult relations in the fetal specimens 

 shown in figs. 39 and 40. In the specimen shown in fig. 41 the 

 infundibulum ethmoidale might continue its development or 

 pouching lateral to the frontal recess and frontal furrows and thus 

 form the frontal sinus. The aforementioned conditions are met 

 with in the adult nose, and all may be accounted for by studying 

 the varying fetal conditions. In a general way we may say, that 

 when the frontal sinus develops from an anterior ethmoid cell, 

 the adult sinus will have a nasofrontal duct — the tortuosity of 



