AND PHYSIOLOGY. 



51 



Fig. 60. 



the only movable bone of the head or face. It contains the 

 sixteen lower teeth, is of an arched form, and at each ex- 

 tremity has a square-shaped process for articulation with the 

 temporal bones, and the attachment of muscles. 



118. Vomer.— The 

 name of the Vomer is 

 derived from the Latin 

 meaning a "plow- 

 share," on account of 

 its approximate resem- 

 blance to that object. 

 It completely separates 

 the nostrils from each 

 other, and like the tur- 

 binated bones gives at- 

 tachment to no mus- 

 cles. 



The Vomer. 1, 2, Posterior and Superior Surface 

 hollowed to receive the Azygos Process of the 

 Sphenoid Bone. 3, Anterior Surface for the Car. 

 tilaginous Septum of the Nose. 



119. Number of Teeth.— The Teeth of the Human Adult 

 when all present in the jaws, number thirty- two. And al- 

 though properly bones, still they differ in three respects : 



1st, Organic Composition. 



2nd, Time of Development and Replacement. 



3d, Decay when fractured. 



120. Organic Composition, Cementum, Dentine, Enamel, 

 Microscopic Structure of Enamel, Development of Teeth, 

 Nasmyth's Membrane.— The Teeth are composed of three 

 substances : a Cementum which forms a thin coating on the 

 fangs of the teeth, and which thickens in advanced life ; the 

 Dentine which resembles bone in its external characteristics 

 and makes the largest part of the teeth, containing the prin- 

 cipal vessels and nerves of the teeth ; and the Enamel, the 

 hardest substance in the human body, which is a covering to 



118. From what does the Vomer derive its name? What two cavities does it sep- 

 arate? 119. How many teeth in an adult? In what respects do they differ from the other 

 hones of the body ? 120. Of what substances are the teeth composed ? 



