6G 
OSTEOLOGICAL GALLERY. 
Passing to the appendicular skeleton, we have to notice first the 
anterior or shoulder-girdle, which in Mammals consists generally 
of only two separate bones — the clavicle or collar-bone, very often 
absent or imperfectly developed ; and the scapula ( 5 c) or shoulder- 
blade, to which latter there is firmly united a small projection of 
bone, the coracoid (cr), representing a third girdle-bone, which is 
separate in Birds, Reptiles, and Fishes, and also in the Mono- 
tremes, the lowest of all the jMammalia. 
The scapula is a more or less flattened triangular bone placed 
outside the ribs, but not attached to them by bone, and with its 
narrow end directed towards the ventral side of the body. At this 
narrow end there is a hollow socket into which the head of the 
upper arm-bone fits. Down the centre of the scapula on its outer 
surface runs a long prominent ridge, which terminates below in a 
prolonged process [acromion), to the tip of which the collar-bone, 
when present, is attached ; its other end being united to the upper 
part of the breast-bone. 
The humerus [h), or upper arm, is the powerful bone placed 
between the shoulder and elbow, and articulating above with the 
scapula by a ball-and-socket joint, and below with the radius [r) 
and ulna [u), the bones of the forearm, by a simple hinge-joint 
allowing motion in one direction only. 
The two bones of the forearm are joined below to the wrist- 
bones, collectively called the carpus (cp), and succeeded first by 
the metacarpals [mp), or palm-bones, and then by the phalanges 
(ph), or finger-bones, usually three to each properly-developed 
digit. 
The posterior girdle or pelvis [pv] is comparatively strong and 
rigid, firmly attached to the sacral part of the vertebral column. 
Originally it consists of three distinct bones on each side — the 
ilium [il), ischium [isch), and pubis [ph), corresponding, the first 
to the scapula, and the two latter together to the coracoid ; but 
soon they are so completely united as to appear to be but a single 
bone. 
The hind limbs themselves consist of a similar set of bones to 
those of the anterior pair, viz. the femur [fm) , or thigh-bone, corre- 
s])onding to the humerus, followed by the tibia [tb) and fibula [fb), 
or shin-bones, representing the radius and ulna ; the tarsus [ts), or 
