of the sternum. In the Silk-fowl, which
cannot fly, the crest is 34 per cent. less deep than what it ought to
have been. This reduction of the crest in all the breeds probably
accounts for the great variability, before referred to, in the
curvature of the furcula, and in the shape of its sternal extremity.
Medical men believe that the abnormal form of the spine so commonly
observed in women of the higher ranks results from the attached muscles
not being fully exercised. So it is with our domestic fowls, for they
use their pectoral muscles but little, and, out of twenty-five sternums
examined by me, three alone were perfectly symmetrical, ten were
moderately crooked, and twelve were deformed to an extreme degree.

Finally, we may conclude with respect to the various breeds of the fowl,
that the main bones of the wing have probably been shortened in a very
slight degree; that they have {274} certainly become lighter relatively to
the leg-bones in all the breeds in which these latter bones are not
unnaturally short or delicate; and that the crest of the sternum, to which
the pectoral muscles are attached, has invariably become less prominent,
the whole sternum being also extremely liable to deformity. These results
we may attribute to the lessened use of the wings.

_Correlation of Growth_.--I will here sum up the few facts which I have
collected on this obscure, but important, subject. In Cochins and
Game-fowls there is some relation between the colour of the plumage and the
darkness of the egg-shell and even of the yolk. In Sultans the additional
sickle-feathers in the tail are apparently related to the general
redundancy of the plumage, as shown by the feathered legs, large crest, and
beard. In two tailless fowls which I examined the oil-gland was aborted. A
large crest of feathers, as Mr. Tegetmeier has remarked, seems always
accompanied by a great diminution or almost entire absence of the comb. A
large beard is similarly accompanied by diminished or absent wattles. These
latter cases apparently come under the law of compensation or balancement
of growth. A large beard beneath the lower jaw and a large top-knot on the
skull often go together. The comb when of any peculiar shape, as with
Horned, Spanish, and Hamburgh fowls, affects in a corresponding manner the
underlying skull; and we have seen how wonderfully this is the case with
Crested fowls when the crest is largely develope