188 A MANUAL OF DENTAL ANATOMY. 



which I shall again return in speaking of the eruption of 

 the teeth. 



It remains to speak in some further detail of the 

 precise means by which the enlargement of the jaw is 

 effected. 



To a slight extent there is formation of bone going on at 

 the symphysis, prior to the complete anchylosis taking 

 place : the share taken by this in increasing the size of the 

 jaw would, however, appear to be but small, after the ter- 

 mination of the intra-uterine period. Additions to the 

 surface, at the edges of the alveoli and at the base of the 

 jaw are continually going on, and bring about that addition 

 to the exterior already noticed. 



But the main increase in the size of the jaw has been in 

 the direction of backward elongation; in this, as Kolliker 

 first pointed out, the thick articular cartilage plays an im- 

 portant part. The manner in which the jaw is formed 

 might almost be described as wasteful ; a very large amount 

 of bone is formed which is subsequently, at no distant date, 

 removed again by absorption; or we might compare it to a 

 modelling process, in which thick, comparatively shapeless 

 masses, are dabbed on to be trimmed and pared down into 

 form. 



To bring it more clearly home to the student's mind, if 

 all the bone ever formed were to remain, the coronoid pro- 

 cess would extend from the condyle to the region of the first 

 bicuspid, and all the teeth behind that would be buried in 

 its base: there would-be no "neck " beneath the condyle, 

 but the internal oblique line would be a thick bar, corre- 

 sponding in width with the condyle. It is necessary to 

 fully realise that the articular surface with its cartilage 

 has successively occupied every spot along this line ; and as 

 it progresses backwards by the deposition of fresh bone in 

 its cartilage, it has been followed up by the process of 

 absorption removing all that was redundant. 



