SOCIETY OF THE UNIVERSITY Otf ABERDEEN. 



63 



" the order of events may be arranged in stages for the sake of clear- 

 ness thus : 



1. Meckel's cartilage appears. 



2. Dentary is seen below. 



3. Centres for condyle, corouoid, angle and mento-Meckelian. 



4. Network of osseous tissue connects them together. 



5. Splenial appears as a ledge of bone supporting the teeth. 



6. Disappearance of Meckel's cartilage from jaw, and fusion of 



splenial." 



All that part of lower jaw in front of the mental foramen is an 

 ossification of Meckel's cartilage. He describes the inferior dental 

 nerve and splenial as lying below Meckel's cartilage, and says that 

 after the fourth month Meckel's 

 cartilage atrophies and the splen- 

 ial passes down to enclose the 

 nerve. 



Schaffer (17) in 1888 made 

 a careful histological examination 

 of the developing lower jaw in 

 the sheep. He describes the 

 lower jaw as being formed as a 

 membrane bone with independent cartilages for the condyle and 

 for the angle. 



Henneberg (6), in 1894 in an inaugural dissertation for the doc- 

 tor's degree presented to the University of Berlin, deals with the 

 development of the lower jaw in man. He carefully describes the 

 appearances presented by the developing lower jaw in a series of 

 human foetuses. I became acquainted with his paper only after I 

 had completed my own research on human lower jaw development, 

 and I find that his descriptions correspond exactly to the appearances 

 presented by my own material. He treats of the appearances pre- 

 sented by the developing lower jaw in human foetuses of from 

 40 mm. to 240 mm. crown-rump measurement. Henneberg's is 



Fig. 3. Represents the lower jaw of a human 

 fictus at about the tenth week of intra-uterine 

 life (after Mr. J. Bland-Sutton). 



B. Coronoid. E. Mento-MecUelian. 



C. Condyle. F. Dentary. 

 A. Splenial. D. Angular. 



