82 AGRICULTURE. [en. 



producing matter in the blood, the lungs work away 

 at it, and purify the blood just to that degree which is 

 necessary for keeping up the warmth of the body. 

 Shelter from the cold is therefore desirable upon 

 economical grounds, for thereby less of the heat-pro- 

 ducing matter in the blood is thus used, and that 

 which remains can be stored up in the animal as 

 fat. 



169. The formation of fat is also encouraged by 

 the motion of the body being limited, for as 

 motion stimulates the lungs to greater activity, so a 

 larger proportion of the heat-producing matter is 

 burnt off, and less remains to be converted into fat. 



170. The size of the lung influences the forma- 

 tion of fat, for the quantity of oxygen drawn into the 

 lungs, and dissolved in the blood is regulated thereby. 

 A largely developed lung will more fully oxidize 

 the heat-producing matter of the blood than a 

 small lung, and hence it has been found that the 

 animals which fatten most readily have the smallest 

 lungs. 



171. It has also been observed that a small or 

 inactive liver promotes fattening, but there are 

 limits which cannot be passed without fatal conse- 

 quences. Sheep which have the rot in the liver, fatten 

 with greater rapidity during the first eight or ten 

 weeks after they have taken it, than previously, but 

 after this length of time the liver becomes so rotten, 

 that the general health suffers, and the animal pines 

 away and dies. 



172. The management carried out for establishing 

 our improved breeds, encourages the formation of 

 small lungs and small livers. By preventing the 

 animals taking much exercise, these organs also 

 become slow in their action and naturally sluggish. 

 A larger proportion of the heat-producing matter is 

 left, and becomes stored up in the animal as fat. We 

 therefore consider such animals good fattening animals, 



