SKELETON 859 
said (pages 439, 440); (2) the forearm, consisting of the Raprus, 
before mentioned (page 762) and ULNA; and (3) the Carpus 
(page 77, 78), Meracarpus (page 547) and Digits, which last 
three form the hand. According to Prof. Gegenbaur, the original 
arrangement of the wrist-bones consisted of (a) three proximal ele- 
ments—the carpale ulnare, c. intermedium and c¢. radiale; (b) one 
median element ; and (c) five distal carpals, each of which carried a 
metacarpal with a digit. In Birds these elements are much reduced 
by fusion and suppression, so that there are now only two free 
carpals—one, generally termed the “radial,” but resulting from the 
fusion of the ¢. radiale with the 
c. intermedium, and articulating with 
the distal end of both radius and 
ulna; and the other, the so-called 
“ulnar,” which is really the centrale 
and ulnare combined, and articu- 
lates with a small portion of the 
ulna only. The distal carpals are 
now reduced to three, the fourth 
and fifth being lost. They fuse in 
the embryo with the proximal end 
of the three first metacarpals, and 
all trace of their originally separate 
existence disappears when the hand 
is completely ossified. 
Common Fowt, Embryo and Adult. 
The greatest reduction of the  ¢4¢, distal carpals 1-3; H. Humerus; M. 
carpal bones prevails in the Ratifx. Metacarpals 1-4; R. Radius ; r. radial carpal ; 
Setting aside the Dinornithes, of V: Uta ™ winar carpal. 
which only remnants of a humerus are known, Caswarius galeatus has 
only one separate carpal, which is probably the ¢. wlnare, while in 
Apteryx owen and in Dromexus even this is suppressed. 
The Metacarpus is composed of three bones, the first, second 
and third metacarpals, while trace of a fourth has been observed 
in embryos. The first of these is the shortest, and bears the 
POLLEX (page 737). In most Birds it fuses throughout its length 
with the inner margin of the second, which, as well as the third, 
is much longer. The ends of these fuse, the proximal first and 
the distal later, leaving as a rule a space between the shafts. The 
second is by far the strongest, generally straight, and bears the 
INDEX (page 459), while the third is outwardly bowed and much 
more slender, being in a degenerate condition. In embryos it 
sometimes still shews two phalanges, but these are soon reduced 
to one, which, resting closely against the proximal phalanx of the 
second digit, occasionally fuses with it. Curiously enough this 
1 Of all Birds Archzxopteryx alone is known to have had 3 free metacarpals, 
and 8 free digits, with 2, 3 and 4 phalanges respectively. 
