30 VETERINARY DENTAL SURGERY. 



the pulp, which gradually decreases in size as the 

 dentine increases. At the same time the enamel is 

 formed from the enamel organ, it being deposited in 

 crystals, the cement is produced from calcification of 

 that portion of the periodental membrane lying next 

 the tooth. As calcification advances, the tooth 

 presses its way through the gums, which become 

 absorbed. At the same time the divisions between 

 the teeth become ossified, so that each tooth is wholly 

 surrounded by bony structures, except the crown 

 which is gradually pushed up by the lengthening of 

 the roots. As the tooth grows the dental sac elon- 

 gates gradually diminishing in size owing to the form- 

 ation of dentine on its outer surface, until only a small 

 cavity is left in the center of the root in which rests 

 the dental pulp. 



