22 VETERINARY DENTAL SURGERT. 



following the line of the dental arch. As it wears it 

 narrows laterally, but its short axis widens until in 

 old age it is nearly round, what was the fang being 

 in wear. 



The free surface of an incisor tooth, excepting 

 the table, is covered by a layer of enamel, (Fig. 6 4 

 A,) the fang which is a single process, being covered 

 by crusta-petrosa. Towards the center of the table 

 in a young tooth a second ring of enamel is visible 

 (Fig. 4 4, B,) which is the mouth of a funnel-shaped 

 cavity called the infundibulum. This cavity in the 

 young animal is ovoid, its long axis following that of 

 the table; it is lined by crusta-petrosa, which becom- 

 ing stained by the food constitutes the so-called 

 "mark." The space between the two tubes of enamel 

 is filled up with dentine; hence the table is a com- 

 pound one i. e. all three of the dental tissues are in 

 wear on it. The infundibulum or mark being coni- 

 cal in shape, wears with the tooth, becomes smaller 

 and ultimately vanishes. 



In the center the table in front of the mark is 

 broader than behind it, and as the tooth wears it still 

 broadens. In this space sometimes a spot is apparent 

 which differs from the rest of the dentine ; it is the 

 osteo-dentine covering the pulp cavity. This object 

 ( Fig. 6-4, c,) has been termed the dental star. The 

 corner teeth may have no posterior tables constituting 

 shell teeth; rarely, they are absent in every tooth 

 when we have a shell mouth. 



