CHAPTER V. 

 DEVELOPING TOOTH. 



Tooth. Adult, in the jaw of a cat. (p. 8, c. G., s. 19, m. F.) (L) 

 The tooth consists mainly of dentine. That part which projects 

 beyond the gum is the crown, and is covered with enamel (here 

 removed). From the neck downwards the fang is implanted 

 in the alveolar cavity, and is covered by the crusta petrosa, a 

 thin layer of bone. The alveolar walls are formed by the bone 

 of the jaw. Between the jaw and the fang is the dense fibrous 

 peridental tissue. In the middle of the dentine is the pulp 

 cavity which communicates with the exterior through an 

 aperture at the apex of the fang and through which blood 

 vessels and nerves enter. (H] The dentine is traversed by 

 numbers of minute canals, the dentinal tubules. Commencing 

 on the surface of the pulp cavity they radiate outwards, 

 dividing occasionally. Minute secondary offshoots leave them, 

 most numerously near to and constituting their peripheal 

 terminations. A zone of inter-globular spaces, better seen in 

 dry preparations is found in the outer part of the dentine, 

 especially in the region of the neck. They derive their name 

 from the characters of their outlines. The crusta petrosa 

 increases in thickness towards the apex of the fang ; in it are 

 found lacunae, the matrix being the same as that of bone. 

 The fibres of the peridental membrane are embedded in it, 

 and form a tendinous attachment to the alveolar wall. The 

 pulp, an open connective tissue texture, contains blood vessels, 

 lymphatics, and nerves ; the odontoblast cover its surface and 

 lie in contact with the dentine, from them delicate processes 



