to the Rearivg and Feeding of Cattle. 
249 
sour : hence it is requisite that wet-nurses shouhl be kept in a state 
of perfect tranquillity both in mind and in body.* 
For a similar reason it is necessary in dairy-farming to use 
every means to insure the tranquillity of our milch-cows. Harsh 
treatment exerts a very injurious action on the nature of the milk, 
both from mental and j)hysical causes. Dairymen are well aware 
of the evil results which follow, if cows be harassed either by 
dogs or by harsh keepers. 
The great cause which renders milk pooi-, that is, deprives it 
of its proper quantity of butter, is the respiration of too great an 
amount of oxygen. This gas combines so easily with butter, that 
it is of great importance to prevent an excess from entering the 
body. Now the number of respirations is increased, either by 
exercise, or by external cooling — hence more oxygen in these 
cases enters the system, and consumes a proportional quantity of 
the butter of the milk. You all know when a cow runs, on its 
way home to be milked, that the milk becomes hot, and is prone 
to sourness. The running increases the number of its respira- 
tions, and, consequently, the amount of oxygen which enters its 
system. This oxygen unites with the butter, or, in common lan- 
guage, burns it ; and the heat produced in the milk is the result 
of the combustion of the butter. The milk in such a case is also 
reduced in volume : this is partly owing to the evaporation of its 
water by means of the heat thus produced ; hence it is that such 
milk is much poorer than usual, and apt to enter into acidity ; hence 
also your practice of driving home to be milked only those cows 
which feed near home, while those at a distance from it are 
milked in the fields. The amount of oxygen inhaled being too 
considerable, when the animals are driven from a distance, the 
butter is partly consumed. To obviate an excessive respiration of 
oxygen, we find that all good dairymen permit their cows to walk 
home as leisurely as they themselves will do, and never allow their 
driver to accelerate their pace. 
A singular system is frequently pursued, which may be ex- 
plained on this principle. In hot weather in summer, the cows 
are fed in the stall during the day, and turned out to grass during 
the night. Cattle are apt to be annoyed by the flies and by the 
heat during the day. The former cause them to move about 
to avoid their attacks, and thus they respire a greater amount 
of oxygen. This oxygen consumes that part of the food which 
otherwise would have been transformed into butter ; but when 
let out at night, they are not thus disturbed, and the darkness 
* The sympathetic irritation, which occasions a change in the nature of 
the secreted fluids, is conveyed through the sympathetic system of nerves, 
whose branches accompany the blood-vessels to every part of the body, 
and are furnished to the heart and viscera. 
