300 JUDGING FARM ANIMALS 



fat, and these cells break off, leaving behind them the parent 

 cell, containing a nucleus from which another cell grows. 

 Thus the formation of fat in milk is really a process of 

 cell secretion. The proteins, sugar and salts in milk, are 

 secreted in the ordinary way from the blood, or rather the 

 lymph, circulating in the gland, the cells lining the alve- 

 oli being active in the matter. That these substances are 

 really produced by the cell is supported by the fact that 

 neither caseinogen nor milk sugar exist in any other tissue 

 of the body. The secretion of the alveoli finds its way 

 through outlets into the lobules, and from these into the 

 lobes, and thence into the smaller orifices seen in the udder 

 when cut open, from which it is conveyed into the milk 

 cistern. It has been supposed that the secretion of milk 

 is influenced by the nervous system, but there is no ex- 

 perimental evidence which places this beyond doubt. How- 

 ever, the action of the blood vessels is affected by the ac- 

 tivity of the nerves. The greater the capacity of the 

 arteries and veins of the udder, the larger the milk secre- 

 tion will be. According to R. Meade Smith: 13 "as far as 

 we know, the mammary secretion is dependent upon the 

 amount of blood passing through the glands. Changes in the 

 general blood pressure, by modifying the blood supply of the 

 mammary gland, also influence the amount of milk secreted. ' ' 

 The form of the udder requires consideration in de- 

 tail. In the arrangements of some scales of points, 

 the front and rear parts of the udder are separately de- 

 scribed and assigned separate values. The udder should 

 be large, according to the age and condition of the cow. 

 In the mature animal, in full flow of milk, size is naturally, 

 though not necessarily, associated with heavy milk yield. 

 If the mammary development as a whole is good, then large 

 size is a distinctly desirable feature. The udder should 

 be long, extending high up behind between the thighs, and 

 carried well forward along the belly, with the under side 

 or "floor" as it is often termed, flat or level. Present day 



18 Physiology of Domestic Animals, 1890, p. 631. 



