itch, with a
single leg deficient, and she produced several puppies with the same
deficiency. From Hofacker's account[24] it appears that a one-horned stag
was seen in 1781 in a forest in Germany, in 1788 two, and afterwards, from
year to year, many were observed with only one horn on the right side of
the head. A cow lost a horn by suppuration,[25] and she produced three
calves which had on the same side of the head, instead of a horn, a small
bony lump attached merely to the skin; but we here approach the doubtful
subject of inherited mutilations. A man who is left-handed, and a shell in
which the spire turns in the wrong direction, are departures from the
normal though a symmetrical condition, and they are well known to be
inherited.

_Polydactylism._--Supernumerary fingers and toes are eminently liable,
as various authors have insisted, to transmission, but they are noticed
here chiefly on account of their occasional regrowth after amputation.
Polydactylism graduates[26] by multifarious steps from a mere cutaneous
appendage, not including any bone, to a double hand. But an additional
digit, supported on a metacarpal bone, and furnished with all the
proper muscles, nerves, and vessels, is sometimes so perfect, that it
escapes detection, unless the fingers are actually counted.
Occasionally there are several supernumerary digits; but usually only
one, making the total number six. This one may represent either a thumb
or finger, being attached to the inner or outer margin of the hand.
Generally, through the law of correlation, both hands and feet are
similarly affected. I have tabulated the cases recorded in various
works or privately communicated {13} to me, of forty-six persons with
extra digits on one or both hands and feet; if in each case all four
extremities had been similarly affected, the table would have shown a
total of ninety-two hands and ninety-two feet each with six digits. As
it is, seventy-three hands and seventy-five feet were thus affected.
This proves, in contradiction to the result arrived at by Dr.
Struthers,[27] that the hands are not more frequently affected than the
feet.

The presence of more than five digits is a great anomaly, for this
number is not normally exceeded by any mammal, bird, or existing
reptile.[28] Nevertheless, supernumerary digits are strongly inherited;
they have been transmit