SOCIETY OF THE UNIVERSITY OP ABERDEEN. 59 



THE DEVELOPMENT OF THE LOWEE JAW IN MAN. 1 



By ALEXANDEB Low, M.A., M.B., Senior Assistant to the Professor of 

 Anatomy and Lecturer on Embryology, University of Aberdeen. 



(Presented 24th June, 1905.) 



The developing mammalian lower jaw has frequently been a 

 subject of research, both by histologists and anatomists. Histologists 

 have found in the developing lower jaw various types of ossification 

 Ultra-membranous, endochondral and the so-called metaplastic type of 

 Strelzoff. Anatomists have mostly regarded the mammalian lower 

 jaw as a compound bone, and have attempted to find homologies for 

 its component parts in the jaw of lower vertebrates. 



But although much research has been done on the subject of 

 lower jaw development, there are still points regarding the ossification 

 of the human lower jaw about which there is doubt. This is seen on 

 examining the various descriptions of the ossification of the lower jaw 

 given in text-books of human anatomy. Thus two standard text- 

 books namely, Quain's and Testut's give different accounts of lower 

 jaw development. 



In Quain's Anatomy (15) it is said that " the process of ossifica- 

 tion commences very early, being preceded only by the clavicle, and 

 proceeds rapidly ; it takes place from several centres, which are united 

 by the fourth month. The largest part of each half is formed from a 

 deposit (dentary) in the membrane on the outer side of Meckel's car- 

 tilage, and to this there is added a second smaller plate (splenial), 



1 1 have to thank the Carnegie Trustees for a grant towards the cost of the illus- 

 tration of this paper. 



