Lateral Wall of the Cavum Nasi in Man. 659 



thus established. The suprabullar recess is a constant point 

 from which anterior ethmoidal cells develop (figs. 31, 34, and 43). 



The bullar furrow. The bullar furrow is placed between the 

 two bullar folds or accessory conchae (fig. 31). It is variable in its 

 differentiation and not at all constant. It is generally obliterated 

 by the superior and the inferior bullar folds becoming continu- 

 ous structures in the formation of the adult bulla ethmoidalis. 

 This coalescence is, however, not always absolute, in that an eth- 

 moidal cell may develop from the furrow, leaving the ostium of 

 the adult cell at the point of the primitive furrow (figs. 31 and 39). 

 Even in many adult specimens we find evidences of this primi- 

 tive furrow in the form of a shallow groove on the medial surface 

 of the bulla ethmoidalis. An ethmoidal-cell ostium on the medial 

 surface of the bulla ethmoidalis is almost invariably the remains 

 of the early bullar furrow. 



The injrabullar furrow. The infrabullar furrow is placed 

 between the inferior bullar and the infundibular folds (fig. 31). 

 It is very inconstant and when present is frequently obliterated 

 by the inferior surface of the bulla ethmoidalis becoming con- 

 tinuous with the infundibular fold. In some cases it is fairly 

 well marked (fig. 34) but, as a rule, it is of minor importance. 

 Rarely an ethmoid cell develops from the furrow — the adult cell 

 draining into the infundibulum ethmoidale. 



The infundibulum ethmoidale. The infundibulum ethmoidale 

 (Recessus inferior der absteigenden Schenkel der ersten Haupt- 

 furche of Killian) is invariably present in some form. It is formed 

 early, and obviously aids in establishing the primitive processus 

 uncinatus. It is directed somewhat ventrosuperiorly and at its 

 ventral and superior termination it may end blindly or develop 

 into an anterior ethmoid cell. At other times it is variously con- 

 tinued into one of the frontal furrows. Rarely it continues its 

 development ventrally and superiorly, remaining lateral to the 

 frontal furrows, and in this way may establish the frontal sinus 

 (figs. 36, 37, 39, and 40). 



Dorsally and inferiorly it either gradually loses its depth and 

 thus becomes continuous with the middle meatus, or it ends 

 rather abruptly in a pocket, due to the superior and lateral curv- 



