horacic
limbs.

M. Isidore Geoffroy St. Hilaire remarks,[186] "L'anomalie se repete d'un
membre thoracique au membre abdominal du meme cote." And he afterwards
quotes from Weitbrecht,[187] who had "observe dans un cas l'absence
simultanee aux deux mains et aux deux pieds, de quelques doigts, de {180}
quelques metacarpiens et metatarsiens, enfin de quelques os du carpe et du
tarse."

[Illustration: LONG FLEXOR MUSCLES AND TENDONS OF THE HAND.

_P.t._ Pronator teres. _F.s._ Flexor sublimis digitorum. _F.p._ Flexor
profundus digitorum. _F.l.p._ Flexor longus pollicis.]

Professor Burt G. Wilder, in his paper on extra digits,[188] has {181}
recorded no less than twenty-four cases where such excess coexisted in both
little fingers; also one case in which the right little finger and little
toe were so affected; six in which it was both the little fingers and both
the little toes; and twenty-two other cases more or less the same, but in
which the details were not accurately to be obtained.

Mr. Darwin cites[189] a remarkable instance of what he is inclined to
regard as the development in the foot of birds of a sort of representation
of the wing-feathers of the hand. He says: "In several distinct breeds of
the pigeon and fowl the legs and the two outer toes are heavily feathered,
so that, in the trumpeter pigeon, they appear like little wings. In the
feather-legged bantam, the 'boots,' or feathers, which grow from the
outside of the leg, and generally from the two outer toes, have, according
to the excellent authority of Mr. Hewitt, been seen to exceed the
wing-feathers in length, and in one case were actually nine and a half
inches in length! As Mr. Blyth has remarked to me, these leg-feathers
resemble the primary wing-feathers, and are totally unlike the fine down
which naturally grows on the legs of some birds, such as grouse and owls.
Hence it may be suspected that excess of food has first given redundancy to
the plumage, and then that the law of homologous variation has led to the
development of feathers on the legs, in a position corresponding with those
on the wing, namely, on the outside of the tarsi and toes. I am
strengthened in this belief by the following curious case of correlation,
which for a long time seemed to me utterly inexplicable,--namely, that in
pigeons of any breed, if the legs are feathered, the two outer toes are
partially connected by skin. These two outer toes correspond with our third
an