168 DARWINISM STATED BY DARWIN HIMSELF. 



especially while 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 show 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 back- 

 ward, 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. 

 I have shown 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 siee, 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, while others have retained 

 nearly the same size, but in both cases the brain has been 

 much reduced relatively to the size of the body. Now, I 

 was at first much surprised on finding that in all these 

 rabbits the skull had become elongated or dolichocepha- 

 lic ; for instance, of two skulls of nearly equal breadth, 

 the one from a wild rabbit and the other from a large 

 domestic kind, the former was 3*15 and the latter 4*3 

 inches in length. One of the most marked distinctions 

 in different races of men is that the skull in some is elon- 

 gated, and in others rounded ; and here the explanation* 



