44 
THE BONES. 
in those birds which do not fly, as the Ostrich and 
Emu, the joints of the spine or hack-hone are more 
or less moveable throughout. In the joints connected 
with the tail, (called the caudal vertebrae ), certain 
other peculiarities in number and form present 
themselves, adapted to the habits of the bird. In 
the Martin and Swallow, where great freedom in the 
pliability of the tail is necessary, they are most 
numerous ; whereas in the Cassowary, which has no 
tail, the last joint only is found. This last varies 
also in form in different birds ; for instance, in the 
Peacock, whose beautiful, fan-like spread of tail- 
feathers is so well known, this last hone is oval, and 
placed horizontally. 
Another striking feature in the skeleton of a bird, 
is the breast-hone, or sternum, as it is called, which 
may be compared to the bottom part of a boat, rest- 
ing on a deep projecting keel. From the upper 
sides of the fore parts of this hone, two others pro- 
ject, called clavicles, from the extremities of which, 
a bone, in the form of the letter V, is projected, 
called the furcula, though better known by the name 
of the merry- thought. Our attention is more par- 
ticularly directed to these three hones, on account of 
their great importance in facilitating the powers of 
flight ; since it is by the clavicles that the wings are 
connected with the breast-hone, and it is by the 
forked-like furcula, or merry-thought, that the wings 
are kept at a proper distance in flight. Accordingly 
we shall find, that in proportion to the bird's neces- 
sities will these hones be strong or weak. Thus in 
the Penguin, for instance, where the wings are little 
more than fins assisting in diving, or the Ostrich 
