72 



ANIMAL DENTISTRY. 



to the incisor teeth, especially the inferiors, which furnish 

 the best evidence of the age after the fifth year. First, by 

 changes in the infundibulum and then by change in the 

 shape of the table surface. The infundibulum of the tooth is 

 produced by the infolding of the enamel into the body of 

 the tooth to a depth of one and a half to two and a half 

 centimeters. The bottom of the cavity thus formed is filled 

 with crusta petrosa, but the outer end is empty and consti- 

 tutes the cup, which becomes blackened by the chemical 

 action of foods and saliva. The infundibula of the incisors 

 are shaped like a flattened cone with the apex inward and 

 the elliptical opening outward. When the tooth is but a . 

 virgin, the cup, made more apparent by its dark color, pre- 

 sents an elliptical opening at the table surface, but as the 

 crown wears away it becomes shorter and more rounded 

 and disappears entirely when the crown has worn as far 

 as the crusta petrosa that fills the bottom of the infundibula. 

 Thereafter the infundibula are not dark but are recognized 

 by their surrounding enamel, at first still elliptical, but final- 

 ly becoming small circular rings located well toward the 

 posterior border of the tables. In the study of dental wear 

 the cup must not be mistaken for the infundibulum, as "cup" 

 refers only to the unfilled portion of the infundibulum. The 

 cups of the incisor teeth disappear three years after erup- 

 tion, and the infundibulum about ten years to fifteen years 

 after. 



The molar teeth have two infundibula extending deeply 

 into the fang. They are entirely filled with crusta petrosa 

 and would entirely escape notice but for the presence of 

 a small dark spot in the center. 



In shape the tables change even more than in their 

 infundibula. In the young tooth the table is flattened from 

 before backward, but as the crowns wear away the other 

 parts of the tooth come to the surface. The table becomes 



