698 



Jacob Parsons Schaeffer 



falling under the type as is represented by fig. 48 will include ap- 

 proximately 40 per cent of my adult specimens. The latter were 

 in a previous paper included among the specimens as representing 

 negative fronto-maxillary relations. Specimens will, of course, 

 now and then differ somewhat from these types, but they will all 

 in a general way fall under one or the other group. 



Bulla ethmoidalis 



Infundibuhim ethmoi- 

 dale 



Sinus frontales 



Recesstis frontalis 



Processus 

 uncinaius 



Fig. 50 A semidiagrammatic drawing of an adult lateral nasal wall. The 

 concha media is partly cut away so as to expose for study the underlying parts. 

 It gives evidence of three primitive frontal furrows, viz., two frontal sinuses 

 which doubtless developed from anterior ethmoid cells, and a third cell which 

 extends towards the agger nasi. The region of the frontal recess is well shown 

 in the drawing. 



In this manner we can account for two frontal sinuses on one 

 side. We can also account for the so-called absence of a frontal 

 sinus. Should the frontal recess or an anterior ethmoidal cell 

 of a frontal furrow, stop short of the vertical portion of the frontal 

 bone we would of course have a diminutive frontal sinus — in 

 fact no frontal sinus as far as position is concerned. We must, 

 ■^however, remember that the first evidences of the frontal sinus 



