SOCIETY OP THE UNIVERSITY OF ABERDEEN. 75 



laginous nodules behind the symphysis one pair at least representing 

 the anterior ends of Meckel's cartilages. Meckel's cartilage is still 

 in existence from a point inside the canine milk tooth, so that no 

 further destruction of it has taken place. There are cartilaginous 

 nuclei along the margins of both alveolar walls in the region of 

 the incisor milk teeth. Further, there is an additional cartilaginous 

 nucleus along the front of the lower border of the jaw in this region. 

 The condylar cartilage is rapidly becoming ossified towards its anterior 

 part, trabeculre of bone passing through it and breaking it up, only 

 islands of cartilage cells remaining ; on the trabeculse are numerous 

 osteoblasts. Schaffer carefully describes the mode of ossification in 

 the condyle, and characterises it as a modified endochondral type. 

 Thus the manner of ossification of the condylar cartilaginous pyramid 

 (lifters as has been pointed out by Henneberg from that of the rest 

 of the lower jaw, which grows by the deposit of lamella of bone. Its 

 different structure is readily seen in the macerated jaw even at birth. 

 Toldt drew attention to the porous structure of the bone here. The 

 coronoid cartilage is still represented, but is rapidly becoming ossified. 



In n f n't us 210 mm. in length, the different cartilaginous nuclei 

 seen in the last specimen are present, but are relatively much 

 smaller. There is one pair of cartilaginous nodules behind the sym- 

 physis, and here are also cartilage cells along the alveolar margins and 

 along the lower margin of the bone in front. Both coronoid and 

 condylar cartilages have undergone further ossification. 



In a foetus 230 mm. in length, there are only traces of cartilage 

 along the edges of the alveolar walls in front, and also in the lower 

 border of the bone (Fig. 15). These small cartilaginous nuclei are 

 now surrounded by bone. The cartilage in the coronoid process has 

 now practically disappeared. There are still remains of the condylar 

 cartilage, its position being indicated by small islands of cartilage, 

 and large marrow spaces. Meckel's cartilage extends as far forward 

 as the canine tooth, and in the sections can be seen closely applied to 

 the inner aspect of the bone to which it is bound by the periosteum ; 

 the cartilage is now relatively very much smal'^v (Fig. 15, III.). In 



