THE DEVELOPMENT OF THE JAW. 189 



On the outer surface of the jaw we can frequently discern 

 a slight ridge, extending a short distance from the head of 

 the bone ; but if the prominence were preserved on the 

 inner surface, the inferior dental artery and nerve would be 

 turned out of their course. We have thus a speedy removal 

 of the newly-formed bone, so that a concavity lies imme- 

 diately on the inner side of the condyle ; and microscopic 

 examination of the bone at this point shows that the lacunae 

 of Howship, those characteristic evidences of absorption, 

 abundantly cover its surface, showing that here at least 

 absorption is most actively going on. 



In the same way the coronoid process, beneath the base 

 of which the first, second, and third molars have successively 

 been formed, has moved backwards by absorption acting on 

 its anterior, and deposition on its posterior surfaces. 



The periosteum covering the back of the jaw is also active 

 in forming the angle and the parts thereabouts. 



It is worth while to add that the direction of growth in 

 young jaws is marked by a series of minute ridges ; in like 

 manner the characteristic marks of absorption are to be 

 found about the neck of the condyle, and the front of the 

 coronoid process, and those of active addition about the pos- 

 terior border, so that the above statements rest upon a basis 

 of observation, and are not merely theoretical. Two cases of 

 arrested development of the jaw ("Dental Surgery," p. 108) 

 lend a species of experimental proof to the theory of the 

 formation and growth of the jaw above given. 



There are authors, however, who maintain that the growth 

 of 'the jaws is not merely a backward elongation of the 

 cornua, together with additions to the external surface, but 

 that an " interstitial growth" takes place. 



AVedl inclines to this latter view, and the question cannot, 

 I think, be held to be absolutely settled. Although it is 

 difficult to form any definite conception of interstitial growth 

 in a tissue so dense and unyielding as bone, so that the doc- 



