2 DRAGONS OF THE PRIME. Jan., 1892 
-1 
zontally, the bird (Fig. 2) has the body almost upright and 
walks on the hind legs only, using the front limbs for flight. 
Owing to its horizontal position, the weight of the 
crocodile’s body is equally distributed over the four limbs, the 
centre of gravity falls within the space between the four feet, 
and the body is in a position of stable equilibrium. Its weight 
tends to bring it down to the ground, but the body is 
kept suspended by muscles which fasten the trunk to the 
front and hind limbs. These muscles are not attached 
directly to the vertebral column, but to two bony girdles, those 
from the fore-limbs being attached to the shoulder-girdle, and 
those from the hind-limbs to the pelvis. The two girdles are 
themselves attached to the vertebral column, but owing to the 
general equilibrium of the body there is no great strain upon 
them and the limbs as points of support, and, consequently, 
no need for a very firm attachment of them to the vertebral 
column. 
If we examine the pelvic girdle (Fig. 5 Cr.), with which we 
are chiefly concerned, we find that in the crocodile, as in all 
vertebrates, it is made up of two parts, one on each side, and 
each composed of three separate bones, which are joined toge¬ 
ther at one point, and there form a socket for the head of the 
thigh bone of the leg. One of the bones of the pelvis—the 
ilium —projects backwards and upwards, and is attached to the 
vertebral column, thus forming the connection between that 
structure and the pelvis. The other two project downwards ; 
one, the pubis, also projecting forwards, and the other, the 
ischium, projecting backwards. The muscles which suspend 
the hinder part of the trunk to the limb pass from the ilium 
to the femur. 
Now, in the bird (Fig. 2), the body is semi-erect, and is 
supported on the two hinder legs instead of on all four, by being 
balanced about a horizontal axis which passes through the 
upper ends of the thigh bones and the sockets of the pelvis. 
The weight of the body, however, is greater in front than 
behind, so that the body tends to swing about its axis down¬ 
wards and forwards ; in fact, if left to itself, the body would 
fall forwards, so that the head and neck would come to 
rest on the ground. This, however, is prevented by the 
arrangement of the bones and muscles of the pelvis, 
which is quite different from that in the crocodiles. 
The centre of gravity, then, being in front of the axis of 
rotation, the front part of the body tends to fall down, the 
hinder part to rise up, just as in the case of a pair of scales 
if one pan is heavier than the other. The muscles are 
attached, on the one hand, to the hind legs, and, on the other, 
