86 The Bird 
mankind and most birds, have less varied movements of 
the fore limbs, the clavicles have fallen into disuse, as 
in the lion and the horse. But in climbing, burrowing, 
and flying animals, such as the squirrel, mole, and bat, 
these bones have been of active use and are well devel- 
oped. But to keep its wish-bone a bird must continue 
to fly: for Nature is opposed to useless parts. So, in 
the flightless cassowary and ostrich, the wish-bone is 
very small or altogether absent. Parrots are almost 
alone in appearing to suffer no inconvenience in flight 
by the lack of clavicles,—these being greatly reduced in 
some species. 
In that anomalous bird the Hoatzin, the clavicles 
are fused not only at their base, but the tips are ossified 
firmly to a projecting spine of bone from the upper part 
of the breast-bone. 
In glancing back over the lower back-boned animals 
we realize that a shoulder-girdle of bones is of no use 
without a limb. Therefore we find the first hint of the 
shoulder-girdle in sharks, in which we also find the first 
limbs, or fins. In these fishes it is nothing but a single 
bar of soft cartilage. In the girdle supporting the pec- 
toral fin of such a fish as the trout or other bony fish, 
we find the adumbration of some of our bird’s bones. 
When we remember how very wing-like is the movement 
of a fin in the water, we will not be surprised to learn 
that the girdle is almost all epiclavicle; these bones 
being the forerunners of clavicles, and giving place, in 
the higher forms, to the real wish-bones which steadily 
increase in size and importance. We would hardly 
