ll shown when Dorkings are crossed with
common four-toed breeds.[30] With animals which have properly less than
five digits, the number is sometimes increased to five, especially in
the front legs, though rarely carried beyond that number; but this is
due to the development of a digit already existing in a more or less
rudimentary state. Thus the dog has properly four toes behind, but in
the larger breeds a fifth toe is commonly, though not perfectly,
developed. Horses, which properly have one toe alone fully developed
with rudiments of the others, have been described with each foot
bearing two or three small separate hoofs: analogous facts have been
noticed with sheep, goats, and pigs.[31]

The most interesting point with respect to supernumerary digits is
their occasional regrowth after amputation. Mr. White[32] describes a
child, three years old, with a thumb double from the first joint. He
removed the lesser thumb, which was furnished with a nail; but to his
astonishment it grew again, and reproduced a nail. The child was then
taken to an eminent London surgeon, and the newly-grown thumb was
wholly removed by its socket-joint, but again it grew and reproduced a
nail. Dr. Struthers mentions a case of partial regrowth of an
additional thumb, amputated when the child was three months old; and
the late Dr. Falconer communicated to me an analogous case which had
fallen under his own observation. A gentleman, who first called my
attention to this subject, has given me the following facts which
occurred in his own family. He himself, two brothers, and a sister were
born with an extra digit to each extremity. His parents were not
affected, and there was no tradition in the family, or in the village
in which the family had long resided, of any member having been thus
affected. Whilst a child, both additional toes, which were attached by
bones, were rudely cut off; but the stump of one grew again, and a
second operation was performed in his thirty-third year.

{15}

He has had fourteen children, of whom three have inherited additional
digits; and one of them, when about six weeks old, was operated on by
an eminent surgeon. The additional finger, which was attached by bone
to the outer side of the hand, was removed at the joint; the wound
healed, but immediately the digit began growing; a