[17] Ibid., i. p. 38.
[18] Life and Letters, ii. p. 14.
[19] Origin of Species, pp. 117, 118.
[20] Ibid., p. 180.
[21] Contemporary Review, December, 1875, pp. 89, 93.
[22] Variation of Animals and Plants under Domestication, i. 292.
[23] Variation of Animals and Plants under Domestication, i. 299-301.
[24] To keep pace with this lateral increase in weight, the leg-bones should have lengthened considerably so that their total deficiency in proportional length is 17 per cent.,—a changed proportion which being linear is more excessive than the increase of weight by 28 per cent. So marked is the effect of the combined thickening and shortening that in the Aylesbury breed—which is the most typically representative one—the leg-bones have become 70 per cent. heavier than they should be if their thickness had continued to be proportional to their length.
[25] This excessive thickening under disuse appears to be due partly to a positive lateral enlargement or increase of proportional weight of about 7½ per cent., and partly to a shortening of about 15 per cent. Carefully calculated, the reduction of the weight of the wing-bones in this breed is only 8·3 per cent. relatively to the whole skeleton, or only 5 per cent. relatively to the skeleton minus legs and wings. The latter method is the more correct, since the excessive weight of the leg-bones increases the weight of the skeleton more than the diminished weight of the wing-bones reduces it.
[26] Variation of Animals and Plants under Domestication, i. 284.