DEVELOPMENT OF THE FACE. 



IS 



as it grows backwards, presses downward the posterior border 

 of the maxilla and thus brings the permanent molar teeth into- 



post border of max. at birth 

 antrum at birth 

 antrum of adult 



opening of antrum 

 milk teeth at birth 



posterior border 

 of max. in adult 



Fig. 11.— Showing the manner in which the development of the Maxillary Antrum 

 affects the size of the palate and position of the molar teeth. 



position (Fig. 11). If the process of growth is arrested, the last 

 molar (wisdom) tooth is left on the posterior border of the maxilla, 

 where it may ultimately be the cause of an abscess. 



MANDIBULAR PROCESSES AND ARCH. 



The two mandibular processes unite in the middle line and 

 form the mandibular or first visceral arch. The arch forms the 

 lower or hinder boundary of the stomodaeum (Fig 1). 



Parts formed from the Mandibular Arch. — Besides the lower 

 jaw, there are formed from this arch the soft parts over and 

 under the jaw, the lower lip, the muscles of mastication, the 

 internal lateral ligament and the malleus. The anterior two- 

 thirds of the tongue, the sublingual and submaxillary glands are 

 formed from the floor of the primitive pharynx between the man- 

 dibular and the second or hyoid arch. These parts are supplied 

 from the nerve of the mandibular arch, and are therefore probably 

 derived, in part at least, from the substance of the arch. 



The Mandibular Arch bounds the stomodaeum behind, and is the 

 foremost of the five visceral arches which encircle and form the 

 walls of the primitive pharynx. Meckel's cartilage forms its 

 skeletal basis (Figs. IOC and 12). The 3rd division of the 

 5 th is its nerve, and its artery is the first aortic arch from which 

 the inferior dental, facial and lingual arteries afterwards arise. 



