192 A MANUAL OF DENTAL ANATOMY. 



deposition, and the bone rapidly developes so as to loosely 

 embrace the neck of the tooth. 



Additions to the margin of the alveoli keep pace with 



FIG. 83 



the gradual elongation of the roots of the teeth ; as this is 

 a moderately rapid process, the alveolar portion of the jaw 

 increases in depth almost abruptly. 



But it does not do so uniformly all over the mouth ; if it 

 did, the teeth could only be closed at the back of the mouth, 

 unless the rami elongated by an equally sudden accession of 

 new bone. 



The front teeth are erupted first, and the jaw deepens 

 first in front : later on the back teeth come up and the jaw 

 is deepened posteriorly ; meanwhile the elongation of the 



( j ) Jaws of a male nine months old, in which the eruption of the teeth 

 is just commencing. 



