70 



PROCEEDINGS OF THE ANATOMICAL AND ANTHROPOLOGICAL 



blasts. The condyle is now well formed and is made of hyaline 

 cartilage, the cells of which become flatter and smaller as they 

 approach the perichondrium. The histological details are represented 

 and described by Sehaffer (I.e., p. 371). As he points out, the forma- 

 tive cells no longer form bone, but a transition tissue to cartilage, and 

 finally hyaline cartilage. This condylar cartilage extends forwards 

 and downwards in the ramus so that sagitally it is wedge-shaped with 

 its base at the condyle, and its apex passing forward under the 

 coronoid process. 



D.4. 



M.C. ^ 



M? in. j. 



x IV J 



Fig. 9. Horizontal sections of the left half of the lower jaw of a human foetus, 43 mm. in length 

 (x 9). The sections are made from above down, I. being at the level of the tooth germs ; 



II. at a somewhat lower plane shows lower jaw as a continuous sheet of membrane bone ; 



III. through the plane of the mental foramen : IV. near the lower border of the jaw, at X 

 ossification is extending into Meckel's cartilage. D. l.-D. 4. indicate dental germs; J., mem- 

 brane bone of jaw ; Mn., mental nerve; M.C., Meckel's cartilage. 



In a foetus 72 mm. in length rapid growth has taken place, the 

 condylar cartilage has increased in length, and the coronoid process 

 become more thickened. Horizontal sections of this stage show well 

 the relations at the symphysis (Fig. 10). The membrane bone forms 

 an irregular outer alveolar margin for all the tooth germs. The 

 anterior extremities of Meckel's cartilage pass close under the germs 

 of the central incisor teeth and meet in the middle line. At this 

 plane immediately behind the anterior extremities of Meckel's car- 

 tilage are two small round nodules of hyaline cartilage. At a lower 

 level Meckel's cartilage is seen below the germ of the lateral incisor 



