G52 ORGANS OF DIGESTION. 



constitute the alveoli ; these firmly embrace the necks of the teeth, and afford them 

 a solid basis of support. 



The eruption of the temporary teeth commences at the seventh month, and is 

 complete about the end of the second year, those of the lower jaw preceding the 

 upper. 



The periods for the eruption of the temporary set are : 



7th month, central incisors. 14th to 20th month, canine. 



7th to 10th month, lateral incisors. 18th to 36th month, posterior molars. 



12th to 14th month, anterior molars. 



Calcification of the permanent teeth commences a little before birth, and pro- 

 ceeds in the following order in the upper jaw, in the lower jaw appearing a little 

 earlier : First molar, five or six months ; the central incisor a little later ; lateral 

 incisors and canine, about the eighth or ninth month ; the bicuspids at the second 

 year ; second molar,- five or six years ; wisdom-tooth, about twelve years. 



Previous to the permanent teeth penetrating the gum, the bony partitions 

 separating their sacs from the deciduous teeth are absorbed, the fangs of the 

 temporary teeth disappear, and the permanent teeth become placed under the 

 loose crowns of the deciduous teeth ; the latter finally become detached, when the 

 permanent teeth take their place in the mouth. 



The eruption of the permanent teeth takes place at the following periods, the 

 teeth of the lower jaw preceding those of the upper by a short interval : 



6J years, first molars. 10th year, second bicuspid. 



7th year, two middle incisors. llth to 12th year, canine. 



8th year, two lateral incisors. 12th to 13th year, second molars. 



9th year, first bicuspid. 17th to 21st year, wisdom-teeth. 



THE PALATE. 



The PALATE forms the roof of the mouth ; it consists of two portions, the hard 

 palate in front, the soft palate behind. 



The hard palate is bounded in front and at the sides by the alveolar arches 

 and gums ; behind, it is continuous with the soft palate. It is covered by a dense 

 structure, formed by the periosteum and mucous membrane of the mouth, which 

 are intimately adherent. Along the middle line is a linear ridge or raphe, which 

 terminates anteriorly in a small papilla, corresponding with the inferior opening 

 of the anterior palatine fossa. This papilla receives filaments from the naso- 

 palatine and anterior palatine nerves. On either side and in front of the raphe, 

 the nuicous membrane is thick, pale in color, and corrugated ; behind, it is thin, 

 smooth, and of a deeper color ; it is covered with squamous epithelium, and fur- 

 nished with numerous glands (palatal glands), which lie between the mucous 

 membrane and the surface of the bone. 



The soft palate or Velum pendulum palati is a movable fold, suspended from the 

 posterior border of the hard palate, forming an incomplete septum between the 

 mouth and pharynx. It consists of a fold of mucous membrane, inclosing mus- 

 cular fibres, an aponeurosis, vessels, nerves, and mucous glands. When occupy- 

 ing its usual position (a relaxed pendent state), its anterior surface is concave, 

 continuous with the roof of the mouth, and marked by a median ridge or raphe, 

 which indicates its original separation into two lateral halves. Its posterior 

 surface is convex, and continuous with the mucous membrane covering the floor 

 of the posterior nares. Its upper border is attached to the posterior margin of 

 the hard palate, and its sides are blended with the pharynx. Its lower border is 

 free. 



Hanging from the middle of its lower border is a small conical-shaped pendu- 

 lous process, the uvula; and arching outwards and downwards from the base of 



