ON THE TEETH OF MAMMALIA. 



malar bone enters into it, forming its external part, while a small portion 

 of its internal margin trenches upon the base of the spinous process of 

 the sphenoid bone. Indeed, in the human skull, the spinous process of 

 the sphenoid bone, though not entering into the glenoid cavity, would 

 seem to strengthen and elevate its internal boundary. 



In Man the articulating condyle, a (fig. 122), is fitted into the glenoid 

 cavity, 6, and is so bounded behind by a ridge, c (the vaginal process), 

 that the luxation, backward, of the lower jaw is impossible; but the 



123 



Fig. 122. A lateral view of the articulating condyle of the lower jaw in Man, a, and of the glenoid cavity, *. 

 Fig. 123. Another view, shewiug their surfaces. 



anterior boundary (a tubercle at the base of the zygoma,) being less 

 elevated, and being rounded off, also, so as to give more liberty of mo- 

 tion, easily permits dislocation in that direction ; an accident which often 

 occurs, when the mouth is opened very widely, as in gaping. The 

 cavity, however, is of considerable depth, and allows, in a certain de- 

 gree, of lateral and antero-posterior movements, especially of the latter, 

 to which the cartilage, intermediate between the condyle itself and the 

 face of the glenoid cavity, not a little conduces. Monro, in his Ana- 

 tomy of the Human Bones, &c., observes, that an intermediate move- 

 able cartilage, thin in the middle, thick at the edges, and, therefore, 

 concave on both sides, is connected firmly by ligaments to the condyle, 

 so as to follow its motions ; but so loosely to the temporal bone, as 

 readily to change its situation, from the cavity, to the zygomatic tubercle, 

 and return again, while the common ligament of the articulation affords 

 space enough for such a change backward and forward : but this liga- 

 ment, like other ligaments of the joints, by a hinge-like union, is strong 

 and short at the sides, to confine the lateral motions. The motions of 

 the human jaw its muscular strength, and the character of the teeth, 

 accord with the multifarious diet of our race, of which the animal por- 

 tion, at least, has to be more or less prepared before its reception. In 

 the Simise the glenoid cavity is much more shallow than in the human 

 subject, and is destitute of any anterior wall, or tubercle, of the zygoma, 

 rising to form a barrier : in fact, it presents a flat surface, on which 



