_a_, Radius; _b_, ulna; _c_, radial carpal; _d_, intermediate carpal;
_e_, ulnar carpal; _f_, accessory carpal; _g_, first carpal; _h_,
second carpal; _i_, third carpal; _k_, fourth carpal; _l-o_, second
to fifth metacarpal bones; _p-s_, second to fifth digits; _1_,
olecranon; _2_, beak of ulna (proc. anconeus); _3_, semilunar notch;
_4_, styloid process of ulna; _5_, styloid process of radius; _6_,
distal epiphyseal lines; _7_, first phalanx; _8_, second phalanx;
_9_, third phalanx. (Ellenberger-Baum, Anat. d. Haustiere.)
]
Four =metacarpal bones= are present. The first is absent, the third and
fourth are large and carry the chief digits, while the second and fifth
are much smaller and bear the accessory digits. Their proximal ends
articulate with each other and with the carpus as indicated above. The
bones are consolidated at about two years of age.
The third and fourth metacarpals are flattened from before backward,
three-sided, and placed close together. The distal end of each bears a
trochlea for articulation with the first phalanx and the sesamoids.
The third is the wider of the two, and articulates with all of the
lower row of the carpus except the first. The fourth articulates with
the fourth carpal chiefly, but has a small facet for the third. The
second and fifth metacarpals are placed further back than the chief
bones. The fifth is considerably the thicker of the two. The proximal
ends are small and articulate with the corresponding carpal and
metacarpal bones. The distal end is relatively large; its articular
surface is condyloid in front, trochlear behind.
Each chief digit comprises three =phalanges= and three =sesamoids=. The
bones of the chief digits resemble those of the ox in form, but there is
no foramen on the interdigital side of the extensor process and the
proximal sesamoids are narrow and ridged behind. The phalanges of the
accessory digits (which do not reach the ground ordinarily) are similar
in form but much smaller.