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. The process of reduction is probably often
aided through the two principles of compensation and economy of
growth; but the later stages of reduction, after disuse has done all
that can fairly be attributed to it, and when the saving to be
effected by the economy of growth would be very small,* are
difficult to understand. The final and complete suppression of a part,
already useless and much reduced in size, in which case neither
compensation or economy can come into play, is perhaps intelligible by
the aid of the hypothesis of pangenesis. But as the whole subject of
rudimentary organs has been discussed and illustrated in my former
works,*(2) I need here say no more on this head.
* Some good criticisms on this subject have been given by Messrs.
Murie and Mivart, in Transactions, Zoological Society, 1869, vol.
vii., p. 92.
*(2) Variation of Animals and Plants under Domestication, vol. ii
pp. 317 and 397. See also Origin of Species.(OOS)
Rudiments of various muscles have been observed in many parts of the
human body;* and not a few muscles, which are regularly present in
some of the lower animals can occasionally be detected in man in a
greatly reduced condition. Every one must have noticed the power which
many animals, especially horses, possess of moving or twitching
their skin; and this is effected by the panniculus carnosus.
Remnants of this muscle in an efficient state are found in various
parts of our bodies; for instance, the muscle on the forehead, by
which the eyebrows are raised
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