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 27 On the Digits of the Hand

Attachment of the first thumb bone to the carpus

The first bone of the thumb [os metacarpale I] is joined to the fifth bone of the wrist [os trapezium] by a rare and peculiar type of joint (G, a, b, c, d in fig. 6, Ch. 25) [art. carpometacarpalis pollicis] that can be flexed and extended as well as moved to the sides; it is prepared in such a way that it provides separately more for motion that is performed to the sides than for flexion and extension. 36 The fifth carpal bone forms a broad depression that projects transversely in a rather wide extension and is carved out more visibly on the inner and outer surface than on the sides. The first bone of the thumb is carved out transversely, or between its inner and outer side, at its upper end [basis metacarpalis], and as it protrudes inside and out it elegantly fits the depression [facies articularis metacarpalis] of the fifth carpal bone, and articulates with it as if by mutual entry. But this is not so pronounced that it has but a single motion, like the mutual entry of other joints. Rather, since the inner surface [facies ulnaris] of the first bone of the thumb juts out more than the outer [facies radialis], and enters more deeply into the depression of the fifth carpal bone which is more deeply grooved at that point, the first thumb bone can be flexed more than extended.



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 27 On the Digits of the Hand