Lateral Wall of the Cavum Nasi in Man. 695 



which developed from the frontal furrows; from the recess and a 

 cell ; or rarely by direct extension of the superior and ventral extrem- 

 ity of the infundibulum ethmoidale. In figs. 46 to 49 we have 

 semidiagrammatic representations of prevailing adult types of 

 nasofrontal relations. 



In fig. 46 the frontal sinus is continued down to the frontal 

 recess, that is, to the ventral and superior portion of the meatus 

 medius. In such a case there is no true nasofrontal duct and 

 presumably the frontal sinus developed by a direct extension of 

 the frontal recess. Note that the infundibulum ethmoidale ends 

 in an air cell and that it is not continuous with the frontal sinus. 

 Occasionally in these instances the infundibulum ethmoidale is 

 carried much nearer to the frontal sinus, and secretion from the 

 latter may drain almost directly into the ventral and superior 

 portion of the infundibulum. 



In fig. 47 there is a nasofrontal duct. This represents a very 

 common condition. Note that while the infundibulum ethmoidale 

 is not continuous with the nasofrontal duct it nevertheless meets 

 the latter duct at an angle. Secretions from the frontal sinus 

 would drain partly into the infundibulum ethmoidale and partly 

 into the middle meatus directly. Doubtless the frontal sinus in 

 such instances developed by the extension of an anterior eth- 

 moidal cell that had its origin in one of the frontal furrows. 



In fig. 48 we again have the representation of a prevailing con- 

 dition or type. There is again a nasofrontal duct, but it is not in 

 line with the infundibulum ethmoidale. Practically all secretion 

 from the frontal sinus would drain into the meatus nasi medius. 

 We must here conclude that the frontal sinus developed by an 

 extension of an anterior ethmoidal cell, presumably the cell from 

 the first frontal furrow. 



In fig. 49 the infundibulum ethmoidale is continuous with 

 the nasofrontal duct. There are two possibilities of development 

 for the frontal sinus in these cases. In the first place the infundibu- 

 lum ethmoidale may have continued its development superiorly 

 and ventrally, lateral to the frontal furrows, and then enlarged 

 into the. frontal sinus. Another explanation may be found in the 

 fact that the infundibulum ethmoidale may have been continu- 



