OCCURRENCE OF AN ACCESSORY NASO-FRONTAL DUCT. 477 



4, by the rudimentary nasofrontal duct just mentioned. The accessory 

 naso-frontal duct arises from about the middle of the inferior surface of 

 the sinus, 12 millimeters lateral from the median line. It takes a perpen- 

 dicular course downward for 12 millimeters where, in a bulbous enlarge- 

 ment of 5 millimeters, it comes in close opposition with the saccus 

 lacrimalis and the upper extremity of the ductus nasolacrimalis, and after 

 curving through an angle of 90° extends medianward for 8 millimeters on 

 the sutura frontolacrimalis just posterior to and above the ligamentum 

 palpebrale mediale. Here it leaves the sutura nasofrontal and runs 

 downward, medianward and anteriorly in the os frontale and then beneath 

 the os nasale to open into the anterior portion of the fossa nasale, 12 

 millimeters below the sutura nasofrontal. The duct in its first course 

 downward and medianward, after leaving the frontal sinus, curves around 

 the first frontal cell above referred to and lies in close opposition to it, 

 a very thin lamina of bone separating them. 



The arrangement of the four frontal cells, of which the frontal sinus 

 represents the second, will conform to the method of development of the 

 frontal sinus from the infundibulum advocated by Killian, which is as 

 follows: In the human foetus five small ridges and six small furrows 

 are to be seen on the lateral wall of the nasal cavity. In front of these 

 is the small nasoturbinal elevation, and below all of these structures a 

 long, narrow, horizontal ridge, the maxillo-turbinal. The maxillo- 

 turbinal gives rise to the inferior concha, the nasoturbinal to the aggar 

 nasi and the processus uncinatus and the five small ridges to the middle 

 and superior concha? and to a fourth concha when present. The bulla 

 ethmoidale develops posterior to the processus uncinatus and the adjoin- 

 ing first furrow and below the first ridge (the Anlage of the middle 

 concha). The anterior furrow, on becoming deeper, thus forms the 

 hiatus semilunaris and the infundibulum ethmoidale. By outward bud- 

 ding of the membrane there arise upon the anterior and superior aspects 

 of the infundibulum the four primitive frontal cells. These are sepa- 

 rated by narrow, incomplete septa, the infundibulum thus becoming a 

 cavity with four branching evaginations. Further development is slow 

 until about the age of puberty. The evagination which extends into the 

 os frontale is termed the sinus frontalis. It may be either one of the 

 four. The relations of the frontal cells in the adult vary accordingly. 

 Killian terms this the indirect mode of development. When the in- 

 fundibulum does not acquire the four evaginating appendages, but forms 

 only one direct evagination anteriorly into the os frontale, there follows 

 the direct mode of frontal sinus formation. In this latter case no frontal 

 cells are present other than the sinus frontalis. 



According to Mouret, that membranous evagination which develops 

 first in the anterior ethmoidal region from the superior lateral wall of the 

 nasal cavity forms the frontal sinus. The relation to the other ethmoidal 

 cells and the variability of the nasofrontal duct are thus dependent upon 



