SKELETON OF RABBIT 795 



are in a postaxial position. But in the normal position of the Hmb in 

 most mammals, the radius and the ulna cross one another in the fore- 

 arm, so that the preaxial radius is external 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 j Cuneiform. Lunar. Scaphoid. 



Centrale. 

 c ^r^xT,^^ Carpale 5 and 4 Carpale 3 Carpale 2 Carpale i 



bECOND I ^j. Qj. Qj. Qj. 



j 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 vertebras ; the pubis — the an- 

 terior 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 obturator foramen, 

 and expand into posterior tuberosities. The ischia of 

 Mammals may touch one another ventrally, but do not 

 fuse in a symphysis ; the pubic symphysis is almost in- 

 variably present. Only in Cetacea and Sirenia is the pelvis 

 markedly rudimentary. 



The hind-leg consists of a thigh or femur, a lower leg 

 with two bones — the tibia and the fibula, an ankle or 

 tarsus, the sole-bones or metatarsals, the toes with several 

 joints or phalanges. 



The head of the femur works in the acetabulum of the pelvis. Near 

 the head are several processes or trochanters, serving for the insertion 

 of muscles : in the rabbit there are three — the great trochanter, the 

 lesser trochanter, and the third trochanter. 



