524.), who has carefully attended to the variation of the muscles in
man, puts in italics the conclusion that the greatest number of
abnormalities in each subject is found in the males. He had previously
remarked that altogether in 102 subjects, the varieties of redundancy
were found to be half as many again as in females, contrasting widely
with the greater frequency of deficiency in females before described.
Professor Macalister likewise remarks (25. Proc. Royal Irish Academy,
vol. x. 1868, p. 123.) that variations in the muscles are probably
more common in males than females. Certain muscles which are not
normally present in mankind are also more frequently developed in the
male than in the female sex, although exceptions to this rule are said
to occur. Dr. Burt Wilder (26. Massachusetts Medical Society, vol.
ii. No. 3, 1868, p. 9.) has tabulated the cases of 152 individuals with
supernumerary digits, of which 86 were males, and 39, or less than
half, females, the remaining 27 being of unknown sex. It should not,
however, be overlooked that women would more frequently endeavour to
conceal a deformity of this kind than men. Again, Dr. L. Meyer asserts
that the ears of man are more variable in form than those of a woman.
(27. Archiv fur Path. Anat. und Phys. 1871, p. 488.) Lastly the
temperature is more variable in man than in woman. (28. The conclusions
recently arrived at by Dr. J. Stockton Hough, on the temperature of
man, are given in the Pop. Sci. Review, Jan. 1st, 1874, p. 97.)
The cause of the greater general variability in the male sex, than in
the female is unknown, except in so far as secondary sexual characters
are extraordinarily variable, and are usually confined to the males;
and, as we shall presently see, this fact is, to a certain extent,
intelligible. Through the action of sexual and natural selection male
animals have been rendered in very many instances widely different from
their females; but independently of selection the two sexes, from
differing constitutionally, tend to vary in a somewhat different
manner. The female has to expend much organic matter in the formation
of her ova, whereas the male expends much force in fierce contests with
his rivals, in wandering about in search of the female, in exerting his
voice, pouring out odoriferous secretions, etc.: and this expenditure
is generally concentrated within a short period. The great vigour of
the male during the season of love seems often to intensify his
colours, independently of any marked difference from the female. (29.
Prof. Mantegazza is inclined to believe ( Lettera a Carlo Darwin,
Archivio per l Anthropologia, 1871, p. 306) that the bright colours,
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