WORCESTER SOCIETY. 151 



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 respirations, and consequently, the amount of oxygen 

 which enters its system. This oxygen unites with the butter, 

 or, in common language, 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 field. The amount 

 of oxygen inhaled, being too considera'ule when the animals are 

 driven from a distance, the butter is partly consumed. To ob- 

 viate 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 dur- 

 ing 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 require 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 prevents their wandering about ; thus they obtain ex- 

 ercise sufficient to furnish them with a good appetite, and the 

 butter in the milk is not consumed. On the other hand, if the 

 night proved cold, more injury than good would be experienced 

 by this system, for a greater amount of butter would be des- 

 troyed. Stall fed cows furnish the greater proportion of butter, 

 a fact to which we shall again advert. Any deficiency of heat 

 must occasion a combustion of butter to supply the requisite 



