16 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



are found in mammals, one (see figure 13,4), exemplified in the 

 carnivora, in which only a hinge action is permitted, and hence the 

 jaws act like scissor blades; the second (see figure 13C),in which 



fi^-petro-mastoid 



post-meat 

 proc: 



post-glen, sp, 



artio. emin, 



styloid 



vaginal proc 

 petro-mastoid 



Fig. 14. -Showing the Chief Changes after birth in the form of the Temporo- 

 Maxillary Articulation. 



A. At Birth. B. At Two Years. C. In the Adult. 



a gliding movement is allowed, the teeth being thus able to act 

 as grinders. The second type occurs in all vegetable feeders. The 

 human articulation combines the characters of both types (Fi». 

 12>B), the gliding action taking place between the interarticular 

 cartilage and the skull, the hinge action between the cartilage and 



