Chat. IY. EFFECTS OF USE AND DISUSE. 135 



decreased ; and thirdly, that the capacity of the skull hi these 

 same large lop-eared rabbits is very inferior to that of the 

 hare, an animal of nearly the same size, — I conclude, not- 

 withstanding the remarkable differences in capacity in the 

 skulls of the small Porto Santo rabbits, and likewise in the 

 large lop-eared kinds, that in all long-domesticated rabbits the 

 brain has either by no means increased in due proportion 

 with the increased length of the head and increased size of the 

 body, or that it has actually decreased in size, relatively to what 

 would have occurred had these animals lived in a state of 

 nature. When we remember that rabbits, from having been 

 domesticated and closely confined during many generations, 

 cannot have exerted their intellect, instincts, senses, and 

 voluntary movements, either in escaping from various 

 dangers or in searching for food, we may conclude that their 

 brains will have been feebly exercised, and consequently 

 have suffered in development. We thus see that the most 

 important and complicated organ in the whole organisation 

 is subject to the law of decrease in size from disuse. 



Finally, let us sum up the more important modifications 

 which domestic rabbits have undergone, together with their 

 causes as far as we can obscurely see them. By the supply of 

 abundant and nutritious food, together with little exercise, and 

 by the continued selection of the heaviest individuals, the 

 weight of the larger breeds has been more than doubled. 

 The bones of the limbs taken together have increased in 

 weight, in due proportion with the increased weight of body, 

 but the hind legs have increased less than the front legs ; 

 but in length they have not increased in due proportion, and 

 this may have been caused by the want of proper exercise. 

 With the increased size of the body the third cervical has as- 

 sumed characters proper to the fourth cervical vertebra; and the 

 eighth and ninth dorsal vertebra have similarly assumed cha- 

 racters proper to the tenth and posterior vertebrae. The skull 

 in the larger breeds has increased in length, but not in due pro- 

 portion with the increased length of body ; the brain has not 

 duly increased in dimensions, or has even actually decreased, 

 and consequently the bony case for the brain has remained 

 narrow, and by correlation has affected the bones of the face 



