608 INFLUENCE OF EXERCISE AND WARMTH. 



The same reasoning applies to dairy cows of different breeds. If I 

 give two stones of hay to a smad Shetland cow, she may not convert 

 more than one of them into dung, the other she may consume for the 

 production of milk. But if I give the same quantity to a cow of double 

 the size, nearly the whole two stones may be converted into dung — may 

 be employed in sustaining the animal — and if she yield any milk at all, 

 it will be poor and thin. 



This reasoning accounts for the fact which has been long observed, 

 that small breeds of cattle give the richest milk, and that such as the 

 small Orkney breed yield the largest produce of butter and cheese from 

 the same quantity of food. They waste less of their food in sustaining 

 their own bodies. Lean, spare cows also require less to sustain them ; 

 and hence the skin-and-bone appearance of the best milkers among the 

 Ayrshire and Alderney breeds. 



2°. The quantity of exercise which an animal takes, or of fatigue it 

 is made to undergo, requires a proportionate adjustment in the quantity 

 of food. The more it is exercised the more frequently it breathes, the 

 more carbon it throws off' from its lungs, the more starch or sugar con- 

 sequently its food must contain. If more is not given to it, the fat or 

 other parts of the body will be drawn upon, and the animal will become 

 leaner. 



Again, the natural waste of the muscles and bones is said to be caused 

 by, or at least to be in proportion to, the degree of motion to which the 

 several parts of the body are subjected. Take more exercise, therefore, 

 move one or more limbs oftener than usual, and a larger part of the sub- 

 stance of these limbs will be decomposed, removed, and rejected in the 

 excretions. Hence the reason why hard work recjuires good food, and 

 why the strength of all animals is diminished, if they be subjected to 

 great fatigue and are not in an equal degree supplied with nourishing 

 food, by which the wasting parts of the body may be again built up. 



3°. The degree of warmth in whicli the animal is kept, or the tem- 

 perature of the atmosphere in which it lives, affects also the quantity of 

 food which the animal requires to eat. The heat of the animal is inse- 

 parably connected with its respiration. The more frequently it breathes, 

 the warmer it becomes, and the more carbon it throws off" from its lungs. 

 It is believed, indeed, by many, that the main purpose of respiration is to 

 keep up the heat of the body, and that this heat is produced very much 

 in the same way as in a common fire, by a slow combustion of that car- 

 bon which escapes in the form of carbonic acid from the lungs. Place a 

 man in a cold situation, and he will either starve or he will adopt some 

 means of warming himself. He will probably take exercise, and by this 

 means cause himself to breathe quicker. But to do this for a length of 

 time, he must be supplied with more fopd. For not only does he give 

 off" more carbon from his lungs, but the exercise he takes causes a greater 

 natural waste also of the substance of his body. 



So it is with all animals. The greater the difference between the tem- 

 perature of the body and that of the atmosphere in which they live, the 

 more food they require to " feed the lamp of life" — to keep them warm, 

 that is, and to supply the natural waste. Hence tlie importance of plan- 

 tations as a shelter from cold winds to grazing stock — of open sheds to 

 protect fattening stock from tlie nightly dews and colds — and even of 



