48 GENERAL ANATOMICAL CHARACTERS 
its anterior surface, and the two bones, instead of being external 
and internal, are anterior and posterior. In many hoofed or Ungu- 
late mammals, and in Bats, the ulna is reduced to little more than 
its upper articular extremity, and firmly ankylosed to the radius 
—-stability of these parts being more essential than mobility. 
Alanus.—The terminal segment of the anterior limb is the hand 
or manus. Its skeleton consists of three divisions: (1) the 
“carpus,” a group of small, more or less rounded or angular bones 
with flattened surfaces applied to one another, and, though arti- 
culating by synovial joints, having scarcely any motion between 
them ; (2) the “metacarpus,” a series of elongated bones placed side 
by side, with their proximal ends articulating by almost immovable 
joints with the carpus; (3) the “phalanges” or bones of the digits, 
usually three in number to each, articulating to one another by freely 
movable hinge-joints, the first being connected in like manner to 
the distal end of the metacarpal bone to which it corresponds. 
Carpus.—To understand thoroughly the arrangement of the 
bones of the carpus in mammals, it is necessary to study their 
condition in some of the lower vertebrates. Fig. 17 represents 
the manus in one of its fullest and at the same time most 
generalised forms, as seen in one of the 
Water Tortoises (Chelydra serpentina). The 
carpus consists of two principal rows of 
bones. The upper or proximal row con- 
tains three bones, to which Gegenbaur 
has applied the terms radiale (r), inter- 
medium (i), and ulnare (uw), the first being 
on the radial or preaxial side of the limb. 
The lower or distal row contains five 
bones, called carpale 1, 2, 3, 4, and 5 
respectively, commencing on the radial 
side. Between these two rows, in the 
middle of the carpus, is a single bone, 
the centrale (c). In this very symmetrical 
carpus it will be observed that the rudiale 
supports on its distal side two bones, 
Set eR ee ee carpale land 2; the zntermedium is in a 
right manus of a Water Tortoise line with the centrale and carpale 3 which 
e se th ee tne ~ together form a median axis of the hand, 
ulnare ; i, intermedium ; 7, radiale ; while the oe has also two bones articu- 
entrale : 1-5 Ave bi s of ¢ o rit, s ste as aaa 
Me one Ge ee 
m5, the five metacarpals. carpals o the distal 
row supports a metacarpal. 
fing ae caaee Sees ap 
The opinion has recently been expressed by Baur that the bone termed 
radiale in Fig. 17 is really a second centrale, and that the radiale is represented 
by a minute bone generally known as the radial sesamoid. The mammalian 
