4 
SKELETON OF THE BIRD. 
giraffe and tlie short one of the elephant being obtained by the prolongation of the seven ver- 
tebrae in the former and their compression in the latter. In the birds, however, there are never 
less than nine vertebrae in the neck, and in some cases the number is considerably greater ; the 
swan, for example, possessing no less than twenty-three of these bones. The neck is also 
much longer in the birds, being in many instances longer than the remainder of the body. 
The vertebrae of the neck are extremely flexible, as is needful for the peculiar habits of birds ; 
but those of the back are immovably connected with each other, and in many cases are even 
fused together. The seven or eight short vertebrae which form the tail are movable, and are 
generally terminated by a single bone of greater length than any of the others. 
We now proceed to the breast and body. The ribs are chiefly remarkable for a flat 
appendage which starts from the lower portion of the bone, and is directed backwards, so that 
it overlaps each succeeding rib. The breast bone is placed lower than might be supposed 
from the external aspect of a bird, and is of very great size. Its substance is much flattened, 
and it possesses a strong ridge or keel of bone, which varies in its depth according to the powers 
of flight possessed by the particular species to which it belongs. As the eagle is a strong- 
winged bird, the keel is very prominent, but in such non-flying birds as the ostrich and the 
apteryx, there is no keel at all. Between the breast bone and the neck lie four clavicles, or 
collar bones, differing much in size and shape in the various species of birds. One set of them, 
technically called the os furculare, from its forked shape, is sometimes absent, its place being 
supplied by a ligament ; but the others, termed the clamculce coracoidce , are invariably 
present. These two sets of bones are familiar to all who have carved a fowl, under the terms 
of “merry-thought” and “ neck bones.” 
The limbs now come before our notice, and we cannot but be struck with the curious fact, 
that in the birds the bipedal mode of walking again makes its appearance, having disappeared 
through all the mammalia with the exception of man. There is, however, this analogy between 
the lower mammals and the birds, namely, that in both instances the anterior limbs are intended 
for progression, although in the one case these formations belong to earth, and in the other to 
the air. The bones of the wing present a considerable resemblance to those of a man’ s arm, as 
may be seen by comparing the skeleton of the eagle with that of the man in Volume I. The 
upper arm bone is of various lengths in the different birds, being of wonderful proportions in 
such long-winged birds as the albatross, but very short in the penguins, the cassowary, and 
many other birds. The two bones of the fore-arm, technically called the ulna and radius , 
are also long in the long- winged birds, and serve to carry a large expanse of feathers. Of 
these two, the ulna is the larger and more cylindrical. To the end of the ulna and radius are 
jointed the two little bones of the wrist, which bear a quasi hand, composed of a thumb and 
two fingers. The thumb is very small, consisting of either one or two bones ; and the fingers, 
which are only needed for the purpose of bearing feathers, are also small. One of them is 
composed of either two or three joints, but the other is a very little one, being but one single 
pointed bone. 
The bones of the legs are very similar in their arrangement to those of the mammalian 
quadrupeds, although they are subject to certain modifications, especially at their extremities. 
The thigh-bone is tolerably strong and cylindrical, but of no very great length, in proportion 
to the size of the bird or the length of its limbs. Even in the curious stilt-plover, where the 
legs are of such extraordinary length, the thigh-bone is comparatively short, and not visible 
outside the feathers. The leg-bone, or “tibia,” is always the longest bone of the limb, and 
is accompanied by a very small and undeveloped “fibula,” which is only attached to its upper 
extremity, and tapers gradually to a point. The “instep,” as we should term it in a human 
foot, is merely a single bone, jointed at its upper extremity to the tibia, and its lower to the 
bones of the toes. In general, birds are furnished with four toes on each foot, but there are 
several exceptions to this rule, among which the ostrich is the most conspicuous. 
Not only do the bones of a bird differ in external form from those of a mammal, but they 
are also considerably modified in their structure. In the mammals the bones are heavy, solid, 
and their centre is filled with marrow ; but in the birds the bones are of a much lighter make, 
and many, such as the upper wing bone, the breast bone, and part of the sku]l, are, moreover, 
