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

Cartilage separating the carpus from the ulna

Lest the ulna touch the wrist with the rest of its epiphysis without the intervention of another body, Nature extended cartilage [discus articularis] (T in figs. 1-4, 7-8) from the lower surface of the depression (x, y, z in fig. 8) carved in the epiphysis of the radius for the sake of the carpus. This cartilage ascends the epiphysis of the ulna, separating it from the carpus, and so prepares the joint that the ulna indeed supports the carpus without coming into close contact, and the whole depression (as was quite necessary) faces the radius.


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I should very much like to inquire into these matters more deeply, the more they conflict with the opinions of Galen. It is not my wish, in a task that is already lengthy enough, to introduce everywhere passages of Galen with which upon reflection I disagree, and to add my reason for disagreeing when an attentive reader would readily notice them without having them called to his attention. But lest I seem excessively to have passed over the opinions of Galen, chief of the anatomists, 53 and especially those views which I normally require students at public dissections to consider, I shall take up a point in Galen’s account of the radius and the ulna which he repeatedly drives home at great length — to wit, the sharp process of the ulna which we compare to a stylus. So I will pass over the fact that he ascribes to the ulna a great portion, actually (as I gather from his writings) half of the depression in which the carpus is articulated; but he also gives this sharp process its own connection to the wrist when in his book De ossibus he gives his account of the ulna and the radius. 54 A little later, when he enumerates the bones of the carpus, he talks about a kind of joint when he states that the third bone [os triquetrium] (3 in figs. 1, 2, 4, 5, ch. 25) of the upper row of wrist bones, the one facing the little finger, has a depression and that the sharp process of the ulna enters it. 55 He propounds as it were two joints of the carpus with the ulna and radius, one of which involves both radius and ulna 56 and the other the sharp process [proc. styloideus] of the ulna, and he claims that this joint has to do with oblique motions of the wrist, while the other joint has to do with vertical movement by which we extend and flex the hand. 57 But I believe that by oblique motion Galen meant that by which the hand is moved to either side: the same motion, that is, by which we spread and draw together the fingers, for that is what Galen means almost everywhere else by oblique or lateral motion. 58 If this is the case, what could be more absurd than to say that this motion is performed by the acute process? So far is this process from being able to aid that motion in any way, it impedes such motion just as if you tied a stick or a rod onto both wrist and forearm — as we see zealous mothers attach a rod to the left thumb and forearm of their children when they see them using the left hand too much and worry that with the passage of time they will use their left hand instead of the right. 59 If you are willing to scrutinize the passage of Galen in the second book of De usu partium, you will notice that he counts a double type of articulation there, and says that the joint made by the sharp process was created so that the hand would be supinated and pronated by means of that joint, and then also moved laterally. After pondering the latter view rigorously, you will agree that it is as repugnant to the truth as the former: the more so when you learn that almost all of the wrist joint has to do with the radius, chiefly so that the hand will follow the motion of the radius, which is to the prone and supine positions. You will also learn that those motions would have to be impeded if the acute process were articulated to the wrist as Galen says it is. Sheep and cattle (not to linger too long on something that is very clear) show this clearly. Their joint more or less corresponding to Galen’s descriptions of the wrist joint cannot readily be moved laterally nor to prone and supine positions. For in those animals the acute process of the epiphysis of the ulna is elongated and has its own depression in the carpal bones; no special cartilage [discus articularis] comes between the ulna and the carpus except the one that covers the bones like a coating. But the kind of cartilage seen in man is one in which the styloid process does not exceed the height of the cartilage as much as the upper part [proc. styloideus] (a in figs. 1, 3, 4, 5) 60 of the depression [facies articularis carpalis] carved in the epiphysis of the radius extends and is brought forward. That part of the radius protrudes for the same reason as the acute process, to shape a depression suitable for the wrist, and so that stronger ligaments enclosing the joint will be put forth from here [proc. styloideus radialis et proc. styloideus ulnaris] (k and i in the 12th table of muscles). Now it is not a single wrist bone that is articulated to this depression of the radius; of the three wrist bones which we shall explain are articulated to the radius and ulna, two [os lunatum, os scaphoideum] (1, 2 in figs. 1, 2, 4, 5 in ch. 25) have to do only with the depression of the radius, and the third [os triquetrium] (3 in the same figs.) faces the cartilage [discus articularis] that grows only out of the radius and the sharp process [p. styloideus] of the epiphysis of the ulna. Because of this, the depression of the radius appears to be double (x, y in fig. 8) because it protrudes slightly in the place (z in fig. 8) where the second wrist bone is attached to the first, as we shall state in the chapter which follows.



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