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Show 1906.] ARTICULATION OF THE VERTEBRATE JAW. 117 is greater between the teeth which are furthest back, near the points A and B, than between the front ones, near the points D and E. But though the pressure at light angles to the level edges of the jaws is not equal in all parts, the oblique forward pressure of the lower jaw on the upper as it slides up underneath it is more nearly equal in proportion as the angle E A C approaches a right angle. The molar teeth of the Hare may be seen to have their flat biting-surfaces set obliquely : those of the upper jaw look downwards and backwards; those of the lower jaw look forwards and upwards. The plane in which they meet simultaneously is at right angles to the line of force (text-fig. 39). Text-fig. 39. \ A / E Diagram of jaws. Type 2. Showing the crowns of the teeth set in a plane at right angles to the greatest pressure. Text-fig. 40. Diagram of jaws. Type 2. Showing the emenentia articularis. Further, economy of movement is obtained in this type by the condyle of the jaw not only rotating, but also gliding forward on to the eminentia articularis. By this means the point A, at the same time that it is separated from B, is depressed, and thus so wide a gape is not necessitated, and also the parallelism of the teeth, and possibly also the position of the inferior dental foramen, is not so much disturbed (text-fig. 40). The molars are also required to make to-and-fro movements over one another. They |