ON THE OCCURRENCE OF AN ACCESSORY NASO- 

 FRONTAL DUCT OF THE FRONTAL SINUS. 1 



By Elbekt Claek.- 



The great variability in the size and extent of the frontal sinus, its 

 position within the frontal bone and its relation to the ethmoidal cells 

 have been well shown by Killian,( 2 ) Onodi,( 6 ) and Zuckerkandl. ( 12 > 

 This structure is indeed so variable that one is inclined to ask if there is 

 any one type of frontal sinus which may be considered normal or dis- 

 tinctly typical. Therefore, it is not surprising that a difference in nomen- 

 clature as well as often some confusion have arisen. It has recently been 

 shown by Wilson* 10 ) that the nasofrontal duct and the ostium frontale 

 are subject also to almost as great variations as the frontal sinus ; and 

 further, that in approximately only 55 per cent of the cases that cavity 

 in the frontal bone, usually termed the frontal sinus, is drained by the 

 duct which is the upward continuation of the infundibulum ethmoidale. 

 In the other 45 per cent it opens into the middle meatus. 



In the anterior ethmoidal region in the immediate vicinity of the sinus 

 frontalis the number of ethmoidal cells (including the sinus frontalis) 

 may vary from one to four (rarely five) ; these are variously known as 

 bulla 3 frontales, anterior ethmoidal cells, etc. They are termed frontal 

 cells by Killian. ( 2 ) They usually open into a co mm on vestibule, more 

 or less well developed, and are often fused and communicating in their 

 upper portions. In the foetus and infant they are seen as membranous 

 evaginations from a slight ethmoidal bulla at the upper extremity of the 

 infundibulum ethmoidale. These Killian (5) designates as the first, 

 second, third, and fourth frontal cells. Either one of these cells may be 

 represented in the adult by the frontal sinus. The frontal sinus may 

 develop from the Anlage of either, the relations in the adult varying 

 accordingly. This cell is usually the largest of the four and in a majority 

 of these cases is a direct continuation of the infundibulum. That frontal 

 cell which is located within the frontal bone is termed by Killian < 2 ) 

 the sinus frontalis, although it may not open into the infundibulxtm 

 ethmoidale. The frontal sinus in this instance is not to be considered as 

 one of the frontal cells. In many skulls four of these anterior ethmoidal 

 cells are seen. 



The present dissection was made on a specimen from a negro subject 

 which was preserved in Kaiserling's fluid, allowed to dry for two weeks 



1 Published from the Anatomical Laboratory, Philippine Medical School, Ma- 

 nila, P. I. 



- From the Hull Laboratory of Anatomy, University of Chicago. 



475 



