OSTEOLOGY AND SYNDESMOLOGY. 19 



surface is concave and forms part of the zygomatic fossa. Of the processes 

 of this bone, the upper one is the superior orbitar. T'he orbitar margin 

 terminates inferiorly in the inferior orbitar or angular process. The zygo- 

 matic process joins the bone with the zygoma of the temporal bone ; the 

 maxillary bone forms a fourth angle. 



This bone articulates with the maxillary, the frontal, the sphenoidal, and 

 the temporal. 



Lower jaw, wax d7Za inferior {pi. 12S ^ ßgs. 15, 16). This bone articu- 

 lates freely with the skull by means of the condyloid processes which play: 

 in the glenoid cavity of the temporal bone. It is distinguished into the- 

 body and the branches. The body consists usually of two halves, which 

 are separate in the very young individual, and unite at the anterior sym- 

 physis. In the adult there are sixteen alveoli or sockets for teeth in the 

 superior margin, and the portion thus occupied possesses somewhat the 

 form of a horse shoe. The symphysis corresponds to the chin, mentum 

 {pi. 121, ßg. 1", ßg. -i"), on each side of which is the foramen mentale 

 {pi. 12S, fig. 15'', pi 121, ßg. 4''); through this pass blood-vessels and a 

 nerve to the face. On the inner surface, about the middle, is a small spine,- 

 spina mentalis interna^ for the attachment of muscles of the tongue and 

 larynx. The extremities of the lower jaw, rami^ are quadrilateral, and rise 

 up much above the level of the body. The superior margin of each ramus 

 exhibits a crescentic notch dividing it into two portions. The anterior 

 portion is triangular and slightly curved backwards ; to it is attached the; 

 temporal muscle, and it is known as the eoronoid process {pi. 12S. ßg. 15^). 

 The posterior border of the notch or concavity is constituted by the 

 condyloid process {ßg. 15'), the application of which has already been 

 mentioned. On the inside of each ramus is seen the posterior mental 

 foramen {ßg. 16°), through which pass the inferior maxillary vessels and 

 nerve. > 



The lower jaw is articulated with the temporal bone in such a manner 

 as to admit of considerable freedom of motion in an antero-posterior and 

 lateral, and still more in a vertical direction {pi. 124, ßgs. 1, 2, 3). An inter- 

 articular cartilage is placed in the joint for greater freedom of movement 

 {ßg. 3 *). On each side of this cartilage is a synovial membrane separating 

 it from the two faces of the joint. The external lateral ligament {ßg. 1 ') 

 arises from the inferior margin of the root of the zygomatic process of the 

 temporal bone, and is inserted into the neck of the condyloid process. The 

 internal lateral ligament {ßg. 2 ') arises from the spinous process of the 

 sphenoid bone, and is inserted into the spine bordering the posterior mental 

 foramen. The stylo-maxillary ligament {ßgs. 1, 2, 3^*) passes from the ex- 

 ternal side of the styloid process, and is inserted into the posterior margin 

 of the jaw, near its angle. 



0. General Considerations respecting the Head. 



The individual bones hitherto considered constitute the head by their 

 apposition, and, as already remarked, are grouped into bones of the cranium,, 

 or brain case proper, and bones of the face. The cranium is an ovoidaL 



"725 



