134 



THE NOSE. 



bone. These differences are well exemplified by comparing fig. 153, which 

 represents the lateral wall of the left nasal fossa in the macerated condition with 

 fig. 154, which shows the right nasal fossa as it appears when still covered by 

 mucous membrane. In (coronal) section each nasal fossa is irregularly triangular 

 in shape, -the apex of the triangle being formed by the roof of the fossa, and the 

 base by the floor. Towards the apex the triangle is quite narrow, but about 

 halfway towards its base, i.e., immediately below the free edge of the middle 

 turbinal (see below), each fossa expands, so that this lower part is nearly quadri- 

 lateral in coronal section (fig. 156) ; this is the respiratory part : the upper narrow 

 part is the olfactory part of the fossa or olfactory cleft. The mesial wall and floor 

 of each fossa is smooth, but the lateral wall is complicated by a series of lamellar 



os frontale 



concha sup. ^ ] 



sin. sphenoid. - 



setta turcica - 



os valati 



sulcus sup. 



agger nasi 



sulcus med. 



concha inf. 



proc. pal. 



foramen 



incisivus 



Fig. 153. VIEW OF THE LATERAL WALL OF THE LEFT NASAL FOSSA AS IT APPEARS IN THE MACERATED 



SKELETON. (Modified from Arnold.) 



prominences running in a sagittal direction and projecting into the cavity ; these 

 prominences, which are formed by the turbinate processes of the ethmoid bone 

 and by the inferior turbinate bone covered by mucous membrane, may be termed 

 the turbinate fiodws, or simply turMnals (concha}. 



The following are the average dimensions of the nasal fossaa (Thane) : 



Greatest vertical measurement (at fore part of cribriform plate) . . 44 mm. 

 Greatest sagittal measurement (along floor, from posterior margin of 



hard palate to anterior extremity of roof) . . . . . . 73 mm. 



Sagittal measurement of osseous part of floor 44 mm. 



Least sagittal measurement (close below cribriform plate) . . . 35 mm. 

 Greatest coronal measurement (near floor) . . . . . .16 mm. 



Least coronal measurement (near roof) . . . . . . . 2'5 mm. 



