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Show 146 THE DESCENT OF MAN. PART I. brate series. Dr. J. Barnard Davis has proved 70 by many careful measurements, that. the mea~ i?ternal capacity of the skull in Europeans IS 92·3 .cubic mc~es; in Americans 87·5; in Asiatics 87·1; and m Australians only 81·9 inches. Professor Broca 71 found that skulls. from graves in Paris of the nineteenth century, were larger than those from vaults of the twolf~h cent~ry, in the proportion of 1484 to 1426 ; and Pnchard IS persuaded that the present inhabitants of Britain have "much more capacious brain-cases" than the ancient inhabitants. Nevertheless it must be admitted that some skulls of very high antiquity, such as the famous. one of Neanderthal, are well developed and capacious. With respect to the lower animals, l\L E. Lartet,72 by comparing the crania of tertiary and recent mammals, belonging to the same groups, has come to the remarkable conclusion that the brain is generally larger and the convolutions more complex in the more recent form. On the other hand I have shewn 73 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 but little their intellect, instincts, senses, and voluntary movements. 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 70 'Philosophical Transactions,' 1869, p. 513.' 11 Quoted in C. Vogt's 'Lectures on Man,' Eng. translat. 1864, p .. 88, 90. Prichard, 'Phys. Hist. of Mankind,' vol. i. 1838, p. 305. 72 'Comptes Rendus des Seances,' &c. June 1, 1868. 78 'The Variation of Animals and Plants under Domestication,' vol.. i. p. ] 24-129. CHAP. IV. MANNER OF DEVELOPMENT. 147 being brought about, the internal pressure of the brain, will, also, have influenced the form of the skuH; for many facts shew how easily the skull is thus• affe~ted. 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 from disease have become fixed either sideways or backwards, one of the eyes has changed its position, and the bones of the skull have been modified; and this apparently results fiTom the brain pressing in a new direction.74 I have shewn that with long-eared rabbits, even so trifling a cause as the lopping forward of one ear drags forward on that side almost every bone of the skull ; so that the bones on tllle- opposite sides no longer strictly correspond. Lastly, if any animal were to increase or diminish much in gaernl 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. 0£ tke body; the shape of the skull would almost cerlainly bealtered. I infer this from my observations on domestic rabbits, some kinds of which have become· very much larger than the wild animal, whilst others ha:v.~ ll(!}truiined nearly the same size, but in both cases the. bralin; has been much reduced relatively to the size of the bgdy,. Now I was at first much surprised by finding that :im. aJ]) these rabbits the skull had become elongated Ol?' doliehg- 74 Schaaffhausen gives from Blumenbach and Busch, the casas of' the spasms and cicatrix, in 'Anthropolog. Review,' Oct. 1868, ~ •. 420. D.r •. Jarrold (' Anthropologia,' 1808, p. 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 believ.es tiiat. certain trades, such as that of a shoemaker, by causing> too liead to be' habitually held forwa.rd, makes the forehead mor.e rounded and prominent. L 2 |