DEVELOPMENT OF THE FACE. 



11 



the mandible, could have become subservient to hearing, and he 

 has produced good evidence to show that the quadrate does not 

 correspond to the incus but to the tympanic plate, with which 

 the mammalian jaw is still in contact. The incus he believes to 



incus 

 stapes 



malleus 



upper part hyoid arch 

 tympanic-quadrate 

 Jnt. pteryg. 



-palate 



hyoid arch 



Meckels cartil. 



articulare 



Fig. 10 D. — Illustrating Gadow's view of the origin of the Auditory Ossicles and 

 Tympanic Plate. 



be derived from the upper segment of the hyoid arch (see Fig. 

 10 D). 



Nerves and Arteries of the Maxillary Process. — A know- 

 ledge of the manner in which the maxillary process is developed 

 explains the distribution and course of its arteries and nerves. 

 The second division of the 5th, represented by the infra-orbital, 

 descending palatine, pterygo-palatine, and Vidian nerves, forms its 

 nerve supply. Its main artery is the internal maxillary. The 

 muscles of the palate are developed in the horizontal palatal 

 processes. 



Formation of Foramina and Canals in Bone. — The develop- 

 ment of canals and foramina in the bones of the maxillary process 

 illustrates the manner in which these are formed in the skull 

 generally. Many foramina and canals occur originally between 

 separate elements (see page 1*70). The Vidian nerve lies between 

 the internal pterygoid plate (a separate bone) and the external 

 pterygoid, a plate which grows into the maxillary process as a 

 cartilaginous prolongation of the great wing of the sphenoid. The 

 pterygo-palatine canal is situated between the pterygoid and 

 palate part of the pterygo-palatine bar. The descending palatine 



