82 THE NASAL ACCESSORY SINUSES IN MAN 



However, in this series there was found no definite rela- 

 tionship between the sex of the individual and the level of 

 the floor of the sinus maxillaris. 



In early childhood the general outline of the sinus is 

 rather ovoid (Figs. 20, 21, 24, and 25), but in later childhood 

 it is gradually changed into a pyramidal form (Figs. 28, 

 30, 33, 37, and 52), which persists as the usual adult type. 

 The base is directed toward the nasal fossa, and corresponds 

 to the medial wall, while the apex extends into the processus 

 zygomaticus. 



The form of the sinus maxillaris is usually described as a 

 three-sided pyramid with irregularly rounded corners. In 

 such descriptions the portion overlying the alveolar process 

 is separately classed as the floor, without giving it a part 

 in the formation of the triangular pyramid. We believe it 

 more consistent to consider the form as quadrilateral at its 

 base, but becoming triangular as the apex is approached. 

 The anterior and the posterior walls, being more closely 

 approximated inferiorly than superiorly, as the apex of the 

 pyramid is approached, the rounded inferior angles are 

 brought so close together that the resulting single rounded 

 angle becomes the inferior boundary in the apical portion. 

 Examples of the usual quadrilateral type of the base are 

 seen in Figs. 30, 33, 45, and 49. A much less frequent type 

 is shown in Figs. 50 and 55, in which variety there is a some- 

 what triangular basal outline. This type is found only in 

 association with a very deep fossa canina. 



In its lateral development the average sinus maxillaris, 

 at the end of the first year, has come into close relation with 

 the nervus infraorbitalis. During the second year the most 

 lateral portion of the sinus passes beneath the nerve, leaving 



