Chap. 5.] Lower Jaw. 10$ 



jfituated at the back part of the palate, noftrils, and 

 orbit ; the olTa fpongiofa are feen in the lower part of 

 the noftrils ; and the vomer helps to feparate thefe two 

 cavities. The bones of the face, befides being con- 

 nected to the bones of the cranium by futures, com- 

 mon to them with the bones of the cranium, are joined 

 to c.-.ch other by fifteen futures, which it would be te- 

 dious to defcribe. Neither does a defcription of the 

 form and connection of each of thefe fmall bones fall 

 in with the general view of the ftructure of the body 

 which I propofe to take, 



The lower jaw in the adult confifts of only one bone. 

 Jn form it refembles a horfe-fhoe, the convex part of 

 which is turned forwards, and forms the chin. At its 

 back part this bone is bent upwards, and terminates in 

 two procefTes. The ancerior of thefe, which riles 

 higheft, is a thin point, into which mufcles are inferted. 

 The pofterior procefs terminates in an oblong fmooth 

 head tipped with cartilage ; it is called the condyloid, 

 and is received into a fo{Ta of the temporal bone, where 

 it is capable of very extenfive motion. There is a ca- 

 vity through the fubftance of this bone, which receives 

 a large twigg of the third branch of the fifth pair of 

 nerves. This begins at the bottom of each coronoid 

 procefs, and terminates externally near the chin. This 

 bone is furnifhed with an.outer and inner bony plate, 

 called the alveolar procefles, for retaining the teeth 

 with firmnefs. In each of the jaws are placed fixteen 

 teeth ; fo that the head, if we include the os hyoides, 

 a fmall bone fituated under the chin, confifts in the 

 adult of fixty-three pieces, 



With refpect to the form of the cranium, whenfeen 

 from above, and when the forehead is placed next the 

 eye, it very much re/embles that of an egg, the os 

 frontis correfponding to the fmaller end of it^ a$d the 



os 



