706 AMIAMMALIA. 
as a rule present in Mammals which grasp or climb or 
burrow. 
The fore-limb consists of an upper arm or humerus, a 
forearm of two bones—the radius and the ulna, a wrist or 
carpus, five palm-bones or metacarpals, and five digits with 
joints or phalanges. 
The head of the humerus works in the glenoid cavity formed by the 
scapula. 
When the arm of a mammal is directed outwards at right angles to 
the body, with the palm vertical and the thumb uppermost, the thumb 
and the radius are in a preaxial position, the little finger and the ulna 
are in a postaxial position. But in the normal position of the limb in 
most mammals, the radius and the ulna cross one another in the fore- 
arm, so that the preaxial radius is externab at the upper end, internal 
at the lower end. The hand is borne by the expanded end of the 
radius. 
The typical mammalian wrist or carpus consists of two rows of bones 
with a central bone between the two rows. In the rabbit all the bones 
—nine in number—are present, viz. :— 
First Ulnare or Intermedium or Radiale or 
Row Cuneiform. Lunar. Scaphoid. 
Centrale, 
Carpale 5 and 4 Carpale 3 Carpale 2 Carpale 1 
— P or or or or 
OM Unciform. Os magnum. Trapezoid. Trapezium 
In Mammals the fourth and fifth carpals are never represented by 
two distinct bones; the centrale is often absent. In the tendons of 
the flexor muscles there are often two sesamoid bones, of which the 
ulnar is called the pisiform. : 
In the rabbit there are five metacarpal bones and five digits, each 
with three phalanges, except the thumb or pollex, which-has but-two. - 
The pelvic girdle is articulated to the backbone, and 
bears externally a cup-like socket or acetabulum in which 
the head of the thigh-bone works. Each half of the girdle 
—forming what is called the innominate bone—really con- 
sists of three bones, which meet in the acetabulum. The 
dorsal bone or ilium, which corresponds to the scapula, 
articulates with the sacral vertebree ; the pubis—the anterior 
of the two lower bones— unites with its fellow on the 
opposite side in the pubic symphysis; the two ischia, 
which correspond to the coracoids, extend backwards, 
separated from the pubes by the large obturater foramen, 
