same groups, has come to the remarkable conclusion that the brain is
generally larger and the convolutions are more complex in the more
recent forms. On the other hand, I have shewn (83. The Variation of
Animals and Plants under Domestication, vol. i. pp. 124-129.) that the
brains of domestic rabbits are considerably reduced in bulk, in
comparison with those of the wild rabbit or hare; and this may be
attributed to their having been closely confined during many
generations, so that they have exerted their intellect, instincts,
senses and voluntary movements but little.
The gradually increasing weight of the brain and skull in man must have
influenced the development of the supporting spinal column, more
especially whilst he was becoming erect. As this change of position was
being brought about, the internal pressure of the brain will also have
influenced the form of the skull; for many facts shew how easily the
skull is thus affected. Ethnologists believe that it is modified by the
kind of cradle in which infants sleep. Habitual spasms of the muscles,
and a cicatrix from a severe burn, have permanently modified the facial
bones. In young persons whose heads have become fixed either sideways
or backwards, owing to disease, one of the two eyes has changed its
position, and the shape of the skull has been altered apparently by the
pressure of the brain in a new direction. (84. Schaaffhausen gives from
Blumenbach and Busch, the cases of the spasms and cicatrix, in
Anthropological Review, Oct. 1868, p. 420. Dr. Jarrold
( Anthropologia, 1808, pp. 115, 116) adduces from Camper and from his
own observations, cases of the modification of the skull from the head
being fixed in an unnatural position. He believes that in certain
trades, such as that of a shoemaker, where the head is habitually held
forward, the forehead becomes more rounded and prominent.) I have shewn
that with long-eared rabbits even so trifling a cause as the lopping
forward of one ear drags forward almost every bone of the skull on that
side; so that the bones on the opposite side no longer strictly
correspond. Lastly, if any animal were to increase or diminish much in
general size, without any change in its mental powers, or if the mental
powers were to be much increased or diminished, without any great
change in the size of the body, the shape of the skull would almost
certainly be altered. I infer this from my observations on domestic
rabbits, some kinds of which have become very much larger than the wild
animal, whilst others have retained nearly the same size, but in both
cases the brain has been much reduced relatively to the size of the
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