Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 5 The Structure of the Head: Why It Is Shaped As It Is, and How Many Configurations It Has

The head was formed for the sake of the eyes

That the human head is formed for the sake of the eyes, is clearly demonstrated, according to Galen, 8 by the eyes of crabs, beetles, and certain other animals that do not have a head. In these animals, the eyes are placed on very long processes and are not hidden deep in their chest as are their mouth, nose, and ears. That eyes require a high location is attested by lookouts for attacks of enemies and bandits, who climb walls, mountains, and high towers for the same purpose as sailors climb the masts of ships, to see land more quickly than those in the ship below. Because the animals just mentioned are covered by a hard, testaceous skin, it was a simple thing for the eyes to be located safely on long processes, because they would be harder and could be covered on the outside by a tunic which, being derived from the skin of those animals, would likewise be very hard and testaceous. But for man, who on account of the substance of the body and the soft, thin membrane [tunica conjunctiva] by which the eyes are covered would necessarily have eyes that are soft throughout, they could not be placed on very long processes without danger. And so, while it was not suited to the function of the eyes that they be located deep in the human body, it was also in no way appropriate to attach them to bare necks; and since Nature was willing neither to prevent the use of eyes nor to diminish their safety, she built a lofty part [cavitas orbitale] that also nicely protected the eyes from danger.



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 5 The Structure of the Head: Why It Is Shaped As It Is, and How Many Configurations It Has