Skull and Hyoid 



243 



the uncinate process of the ethmoid. The ethmoidal and maxillary processes form a 

 plate which fits into the lower part of the antral opening, so that the edge of the maxil- 

 lary part articulates with the lower border of the foramen while the upper projection 

 stands up in the opening to join the end of the uncinate process. The upper edge, 

 behind this " plate," is attached across the vertical plate of the palate. These various 

 articulations can be seen in Figs. 191 and 194, 3. 



(e) A deeply-concave outer surface, widest in front, where it is also smoother ; 

 this part, just below the lachrymal process, forms the outer boundary of the lower 

 portion and opening of the nasal duct. 



(/) A convex and rough inner surface. A ridge in the posterior half, about midway 

 up the bone, marks the position of a canal that carries a nerve and vessels from the 

 posterior palatine set along the bone toward its front end. 



Development. 



In the early fetus the lower edge of the nasal capsule, turned in, makes the pro- 

 jection of the lower turbinal : a centre appears on the surface of this cartilage in the 

 fifth or sixth month or later and extends quickly. The bone frequently joins the 

 ethmoid before middle life. 



NASAL BONE. 



A small bone, meeting its fellow in the middle line and forming the upper and front 

 part of the roof of the nose, immediately below the frontal. 



Each nasal bone has a thick rough base or upper end that articulates with the 



uith fnmtil 



i mtm1ri.n?. 

 FIG. 192. Right nasal bone, from the front, from behind, and from the inner side. 



frontal, a thick rough inner surface that meets its fellow, a thinner outer margin that is 

 supported by the nasal process of the maxilla, and a thin irregular lower edge that slopes 

 upwards and inwards, and to which the cartilaginous structures of the side of the nose 

 are fastened. The front surface, slightly convex from side to side, and concave in its 

 upper part from above down, presents a vascular foramen and is covered by Pyramid- 

 alis nasi and skin : the deep or nasal surface, concave from side to side, is smooth and 

 covered by mucous membrane, under which the nasal nerve runs down on the bone. 

 The inner margin of this surface, where it meets its fellow, rests on the nasal spine 

 of the frontal and on the perpendicular plate of the ethmoid in front of this (Fig. 193). 

 If, as frequently occurs, this plate falls short of the lower margin of the bones, the 

 septal cartilage articulates with the lower part of the median crest. 



1 6 2 



