Xiv. 
bones are fixed in this position, but in a few, as in Man, a free 
movement of crossing and uncrossing—technically known as pro- 
nation and supination—is allowed. In most Quadrupeds the 
ulna is much reduced in size, and the radius, especially at its 
upper end, correspondingly increased, so that the articular surface 
of the latter extends across the entire anterior surface of the 
humerus, and thus the bones become anterior and _ posterior, 
instead of external and internal. 
Manus.—The skeleton of the terminal section of the anterior 
limb consists of three divisions :—(1) the carpus, a group of 
small, more or less rounded or angular bones, with flattened 
surfaces contiguous to one another, which, though articulating by 
synovial joints, that is joints enclosing a capsule which secretes a 
lubricating fluid, have, nevertheless, scarcely any motion between 
them; (2) the metacarpus, a series of bones, placed side by side, 
and with their proximal ends articulating by almost immovable 
joints with the carpus; and (3) the phalanges, or bones of the 
digits proper, which are usually three in number to each digit, 
and articulate to one another, and the first to the distal end of 
the corresponding metacarpal bone, by freely movable hinge- 
joints. 
Carpus.—The mammalian carpus consists of two transverse 
series of bones, of which the upper or proximal, series contains 
three bones, that on the radial side, from which side all these 
bones are counted, being known as the scaphoid, that in the 
middle the /unar, and that on the left the cuneiform bone; the 
lower or distal series contains five bones, of which the two outer 
are always united into a single bone, and receive a common name; 
these have been respectively termed the trapezium, trapezoid, 
magnum, and unciform; between these two series a single bone, 
the central, may or may not be present. ‘Two additional bones are 
generally developed in the tendons of the flexor muscles, one on 
each side of the carpus, which may be called the radial and ulna 
sesamoid bones ; the latter of these, which is the more constant, 
and generally the larger, has received the distinctive title of the 
pisiform bone. 
Metacarpus and Phalanges.—The metacarpal bones are never 
more than five in number, nor are the digits which they assist in 
supporting ; they are described numerically as first, second, ete. 
The digits have each a distinguishing name, the poles (thumb), 
index, medius, annulus, and minimus. One or more of these 
may be in a rudimentary condition, or altogether suppressed, 
and where only one is absent it is generally the pollex. No 
Mammals, except the Ceracna, have more than three phalanges 
to each digit, while in the pollex one of the three is constantl 
absent. The terminal phalanges are usually specially modified 
to support the nail, claw, or hoof, and are termed wngual 
phalanges. Distinguishing terms are applied to the mode of 
