142 



VISCERAL ANATOMY. 



FIG. 65. 



Pulp-cavity, in the interior, opening at the apex of the fang for the entrance 

 of vessels and nerves. 



State the Characteristics of each class of Teeth. 



Incisors, or Cutters. Crown chisel-shaped, beveled posteriorly. Fang single, 



long, thickest antero -posteriorly. 



Canines, or Tearers, Crown thick and conical. Fang longest and thickest 

 of all the teeth, forming a projection on the alveolar arch. The 2 upper 

 canines are the " eye-teeth." 



Bicuspids, Crown has 2 cusps. Fang single but. grooved deeply, showing a 

 marked tendency to bifurcate. 



Molars, or Grinders, Crown large, low and 

 cuboid in shape, has 4 cusps on upper molars, 

 5 on the lower ones. Fangs multiple, usually 

 3 on the first two upper molars, 2. on the first 

 two lower ones; the third molar of either jaw, 

 having but one fang, is called the " wisdom 

 tooth," and is the smallest of the three. 

 The 2d or $d Temporary Molar is larger than the 

 first. 



Describe the Structure of a Tooth. Each 

 consists of 



Dentine or Ivory, " i composed of tubules sur- 

 rounded by the inter-tubular tissue or Matrix, 

 and opening into the pulp cavity. It resembles 

 compact bone in appearance and in composi- 

 tion, consisting of 28 parts Animal matter and 

 72 Earthy matter. The Tubules are delicate 

 wavy canals, diameter about ^ Jg-tf f an i nc ^j 

 which branch outwardly and anastomose with 

 each other, forming concentric shadings or 

 Schreyer's Lines. 



Enamel,* covers the crown; consists of very 

 dense tissue, which contains but 3^ per cent, of 

 animal matter. It is covered by a very delicate 

 epithelial cuticle, Nastnyth's Membrane, which 

 when intact withstands the action of acids. 

 Crusta Petrosa or Cement ? the enamel of the fang; is a layer of true 



bony tissue, containing lacunae, canaliculi, and Haversian canals. 

 Pulp, fills the pulp-cavity and is prolonged into the dental tubules ; is soft, 

 vascular, and sensitive; and consists of connective and fibrous tissue, 



