28 VETERINARY DENTAL SURGERY. 



It also surrounds the body of the tooth to the neck 

 or cervix. 



During the growth of the periodental membrane 

 it becomes closely allied to the surface of both the 

 cementum and the bone. The fibrous elements fix 

 and retain the tooth in its position. These fibers 

 forms the bulk of the tissue of the membrane and 

 have their ends fixed in the cementum of the tooth 

 on one side and in the bone which forms the walls of 

 the alveolar process on the other, being stretched 

 across the intervening space in various directions. 



The periodental membrane is highly supplied with 

 nerves which enter through the walls of the alveolus 

 and by way of the gums below the alveolus. 

 DEVELOPMENT OF THE TEETH. 



The development of the teeth begins from the 

 sixth to the seventh week of foetal life* Prior to 

 this time there is a thick projecting ridge of epithe- 

 lium cells, known as the dental ridge, which extends 

 along the whole length of the jaw. At this time a de- 

 pression is formed ; the dental groove in the mucous 

 membrane of the gum. This is also filled with layers 

 of epithelium which form follicles or sacs. They 

 correspond in number to the temporary dentition, 

 there being one for each temporary tooth. The den- 

 tal groove gradually deepens throughout its whole 

 length, and later is filled with epithelium cells, which 

 form the enamel organ. Each follicle or sac cor- 



