Book 8
1
Now the largest passages leading into the head are those of the eyes, next the nostrils, then those of the ears. Those of the eyes lead direct and without branching into the brain. The two nasal passages are separated by an intermediate bone. These begin at the eyebrows and eye-corners, and their structure is for almost a third part bony, then changes into cartilage, and the nearer they get to the mouth the more soft and fleshy their structure becomes. Now these passages are single between the highest and lowest part of the nostrils, but there they each break up into two branches, one set from the nostrils to the throat for expiration and inspiration, the other leading to the brain and split up in its last part into numerous small channels through which we get our sense of smell. In the ear the passage is also at first straight and single, but as it goes further becomes tortuous. And close to the brain this too is divided into numerous fine passages which give the faculty of hearing. Adjacent to the passages there are two little pits, as it were, above which ends the bones which stretches across from the cheek, supported by deeper-seated bones: it may be called the yoke, from the same resemblance which led the Greeks to call it zygodes. But the lower jaw is a soft bone and a single one, of which the chin forms the middle and lowest portion, whence it is continued on the two sides to the temples; and it alone is movable, for the cheek-bones with all that bone which produces the upper teeth are immobile. Now the ends of the lower jaw itself form, as it were, two horns. One process broader below tapers to its tip, and as it passes higher, goes under the zygoma, and is fastened to the temporal muscles above it. The other is shorter and more rounded off, and in that pit which is adjacent to the auditory passages, it is set in a sort of hinge, and as it bends there forwards backwards supplies the power of movement to the lower jaw.
