290 LAWS OF VARIATION. Chap. XXIV. 



and tlie reduction of these organs affects the general shape 

 of the body. The cause of the reduced lungs in highly -bred 

 animals which take little exercise is obvious; and perhaps 

 the liver may be aifected b}^ the nutritious and artificial food 

 on which they largely subsist. Again, Dr. Wilckens asserts ^* 

 that vaiious parts of the body certainly diifer in AljDine ar.d 

 h^wland breeds of several domesticated animals, owing to 

 their different habits of life ; for instance, the neck and fore- 

 legs in length, and the hoofs in shape. 



It is well known that, when an artery is tied, the anastomosing 

 branches, from being forced to transmit more blood, increase in 

 diameter ; and this increase cannot be accounted for by mere exten- 

 sion, as their coats gain in strength. With respect to glands. Sir 

 J. Paget observes that " when one kidney is destroyed the other 

 " often becomes much larger, and does double work." ^° If we 

 compare the size of the udders and their power of secretion in cows 

 which have been long domesticated, and in certain breeds of the goat 

 in which the udders nearly touch the ground, with these organs in 

 wild or half-domesticated animals, the difference is great. A good 

 cow with us daily yields more than five gallons, or forty pints of 

 milk, whilst a first-rate animal, kept, for instance, by the Damaras 

 of South Africa,'''^ "rarely gives more than two or three pints of milk 

 " daily, and, should her calf be taken from her, she absolutely 

 " refuses to give any." We may attribute the excellence of our 

 cows and of certain goats, partly to the continued selection of the 

 best milking animals, and partly to the inherited efi'ects of the 

 increased action, through man's art, of the secreting glands. 



It is notorious that short-sight is inherited ; and we have seen in 

 the twelfth chapter from the statistical researches of M. Giraud- 

 Teulon, that the habit of viewing near objects gives a tendency to 

 short-sight. Veterinarians are unanimous that horses are affected 

 with spavins, splints, ringbones, &c., from being shod and from 

 travelling on hard roads, and they are almost equally unanimous 

 that a tendency to these malformations is transmitted. Formerly 

 horses were not shod in North Carolina, and it has been asserted that 

 they did not then suffer from these diseases of the legs and feet.^^ 



Our domesticated quadrupeds are all descended, as far as is 

 known, from species having erect ears ; yet few kinds can be 

 named, of which at least one race has not drooping ears. 



2* " Landwirth. Wochenblatt,' No. in South America, see Aug. St.-Hilaire, 



10. ' Voyage dans la Province de Goyaz,' 



25 ' Lectures on Surgical Pathology,' torn. i. p. 71. 

 1853, vol. i. p. 27. " Brickell's 'Nat. Hist, of North 



2® Andersson, ' Travels in South Carolina,' 1739, p. 53. 

 Africa,* p. 318. For analogous cases 



