248 



Anatomy of Skeleton 



FIG. 



Section through an Adult Skull. 



Cribriform ^ p/afc 



-for effimoid 



tia&tf 

 berre 



opens : the groove is then termed the meatus suprema, and its upper boundary may even 

 form a small " supreme " turbinal. The specimens figured in the first two drawings 



in Fig. 194 show such grooves. 



The middle ethmoidal cells as can be 

 seen in the horizontal section in Fig. 197 

 are the smallest, and may only be repre- 

 sented by one cavity overlapped above and 

 internally by the large posterior group. The 

 anterior group seems to be the most variable 

 in its development : the cells may, as in the 

 specimen shown in Fig. 188, extend down 

 into the uncinate process and be completed 

 there by the maxilla and inferior turbinate, 

 or they may tend to extend upwards between 

 the infundibulum and the lachrymal and 

 have their outer walls formed by the last- 

 named bone. Further extensions of these 

 cells are very common, involving the sur- 

 rounding bones, so that cells of this group 

 may have maxilla, lachrymal, inferior tur- 

 binate, or frontal forming part of their walls. 

 It is usual to see some incomplete cells 

 on the upper aspect of the lateral mass, to 

 be completed by the frontal, and such open 

 recesses belong, as a rule, to the posterior 

 group (Fig. 188), with the exception of the most anterior one, just behind the infundi- 

 bulum, which is one of the middle series. 



Open cells on the lower aspect of the lateral mass belong to the middle group and are 

 closed by the maxilla and palate ; thus the ethmoidal surface of the orbital process of the 



FIG. 199. Scheme of the roof of the front part 

 of the nasal cavity. The inferior surface of 

 the cribriform plate forms the roof as far for- 

 ward as the front of the ethmoidal notch ; in 

 front of this is the roof area of the frontal : 

 mucous membrane extends from this on to the 

 posterior surface of the nasal bone (roof) and 

 nasal process of maxilla (side wall). The nasal 

 nerve passes between the ethmoid and frontal, 

 to lie between the mucous membrane and the 

 roof area of the frontal, and so on to the nasal 

 bone. 



