THE SINUS SPHENOID ALIS 165 



recess from the most posterior of the ethmoidal cells.) The 

 extent of pneumatization of the sphenoid bears in no way 

 a constant relationship to the size of the other accessory 

 nasal sinuses, nor was there found to be any definite propor- 

 tion between the size of the sphenoidal sinus and the size 

 of the nasopharynx. In average cases the rate of resorption 

 of the body of the sphenoid is such that by the eighth to 

 the tenth year the posterosuperior portion of the sinus lies 

 beneath the anterior portion of the sella turcica (Fig. 38), 

 and by the fifteenth year is usually separated from the 

 hypophysis by a very thin lamina of compact bone (Fig. 46). 

 Anterosuperiorly, the sinus sphenoidalis is in close relation 

 to the most posterior of the ethmoidal cells (Figs. 28, 43, 

 49, 54, and 57), but in no case was there a communication 

 between the sinus and such cells. Deficiencies in the lateral 

 osseous wall of the sinus have been described by Zuckerkandl 

 and by Craig, but in this series we have found no such condi- 

 tions present. 



Irregularities in the resorption of the bone may leave 

 ridges similar in character to those found in the frontal and 

 in the maxillary sinuses. Varying types of such ridges are 

 seen in Figs. 31, 46, 48, 54, 56, and 57. In addition to these 

 ridges, when there is a recess extending well into the ptery- 

 goid process, there is on the floor of the sinus a distinct 

 ridge (Figs. 45 and 47) which overlies the nervus canalis 

 pterygoidei (Vidii). 



