242 



Anatomy of Skeleton 



Development. 



A centre appears in membrane on each side of the septal part of the cartilaginous 

 nasal capsule during the ninth week, and these join behind the cartilage to make 

 the double bone in the course of a week or so. The bone thus formed is only a shallow 

 trough in which the cartilaginous septum rests, and it separates this structure from the 

 palate folds, and does not extend to the sphenoid or even into the " free edge " of the 

 septum. It increases in size, but even at the beginning of the fourth month it is still 

 in relation with the palate and has not effected any articulation with the sphenoid : 

 this occurs during this month. .The two laminae coalesce to a small extent in an upward 

 and forward direction, the cartilage atrophying to a corresponding degree between 

 them. The greater part of the depth of the bone, however, is the result of ossification 

 in membrane extending downwards and backwards as the maxillary regions increase 

 in height and the nasal fossae enlarge, so that the free edge of the bone, which is at first 



practically horizontal, becomes 

 gradually directed obliquely as 

 the structure increases in depth. 



It has been stated that the 

 anterior end of the vomer is formed 

 from an ossification which involves 

 the vomerine cartilage in part ; 

 possibly this is associated with 

 the small down-growth that pro- 

 jects from its front part into the 

 process. 



uitfi 



xtifldixf. 



. 



orifice 

 tunnel art 

 I'nrtrr tvrjtce . 



upper opening of the anterior 

 palatine foramen. 



******. 



INFERIOR TURBINATE BONE. 



ffei border 



FIG. 191. Right inferior turbinate bone, A. outer side, and 

 B. inner or septal surface. To tell left from right, hold 

 the bone with the pointed end behind, the thick 

 roughened edge down, and the concavity externally. 



A bone projecting into the 

 nasal cavity, attached to the 

 maxilla and the other bones on 

 the outer wall of the nose. It is 

 covered by mucous membrane on 

 both sides, and has its concave 

 aspect looking toward the outer 

 wall of the nose, and its convexity 

 directed towards the septum. 



It has : (a) A lower or free border, thick and roughened by the vascular erectile 

 tissue that covers it. 



(b) A rounded anterior end, thick and covered by mucous membrane, which in the 

 recent state is turned down off its front edge to form (Fig. 194) a fold passing towards 

 the floor of the cavity. 



(c) A pointed posterior end, lying against the vertical plate of the palate. 



(d) An upper edge, by which it is attached. Connected with this border are three 

 processes, ethmoidal, lachrymal, and maxillary ; the two first are directed upwards, 

 but the maxillary process is turned down to fit into the lower part of the opening of 

 the antrum. In front of the lachrymal process the bone articulates with the maxilla 

 below the base of the nasal process ; the lachrymal process lies behind the nasal process 

 and extends up to meet the lachrymal bone here, and, behind this, is in contact with 



