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 24 On the Bones of the Forearm: the Ulna and Radius

The motion of the ulna on the wrist; its lower area

The ulna runs downward from its joint with the humerus more or less straight (from A to B in figs. 1 and 2) to the wrist, becoming gradually more slender and made constantly thinner until it reaches the carpus. It grows somewhat larger there out of its long, thin neck (P in figs. 1, 2, 5, 6, 10), and it has an epiphysis (Q in the same figs.) which is round like a head but irregular. It has a process (R in the same figs.) in its lower part which, because it goes to a point, the Greek anatomists call graphoid, grafoeidh/j, and styloid, stuloeidh/j, for its resemblance to a writer’s stylus. 37 It is formed to augment the depression by which we shall explain the carpus is articulated to the forearm, and to provide an origin for the ligament (i in the 12th table of muscles) [lig. collaterale carpi ulnare] that holds the joint together. We shall address the use of this process in greater detail a little later, if only because Galen assigns too much to it. The lower part of the epiphysis of the ulna facing the carpus has an uneven depression 38 at the inner side of the acute process (S in fig. 10) in which is braced the cartilage (T in figs. 1-4, 7-8) [discus articularis] which you will learn originates in the radius and is lodged mainly between the ulna and the carpus in such a way that it is attached to neither the carpus nor the ulna and is that type of cartilage [cartilago fibrosa] which we have stated (in the margin of chapter 10) is contained specially in the joints of the lower maxilla to the upper [articulatio temporormandibularis] and in the joint of the clavicles with the adjacent bones (R, S in fig. 4, ch. 22) [art. acromioclavicularis, art. sternoclavicularis]. Except for that depression in the epiphysis of the ulna, 39 the entire area facing the wrist 40 is coated with cartilage in the same way as the heads and sockets of all joints are covered and smoothed. In addition to this depression, the epiphysis of the ulna has a depression 41 (V in figs. 2 and 10) carved in its outer surface; this is long and (so to speak) smoothly rounded, having been provided for the tendon of the muscle inserted in the metacarpal 42 bone in front of the little finger [basis metacarpalis digiti quinti]; it is held to be an extensor of the carpus (L in the 9th table of muscles). But in addition to this epiphysis, the form of the ulna along its length and certain impressions and linear bulges still require consideration.



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 24 On the Bones of the Forearm: the Ulna and Radius