Dr. Lyon Playfair on the Milk of the Cow. 289 



experiments of Boussingault. In the milk of the first day 

 there is a small amount of butter. The cow had been ex- 

 posed in the field during the day, and hence required a 

 greater quantity of unazotised food to support the heat of 

 its body than would have been necessary had it been pro- 

 tected from the cold. But in the evening it was removed 

 into a warm and well-littered stall, where the warmth thus 

 communicated was equivalent to a certain amount of food ; 

 and hence we find, that the milk of the morning was consi- 

 derably richer in butter. It is uniformly found to be the 

 case, that a stall-fed cow yields more butter in its milk than 

 one fed in the field. Besides the warmth of the shed, less 

 butter is consumed by the oxygen of the air. In the stall 

 the respirations of an animal are much less frequent than in 

 the field, and consequently less oxygen enters into its system. 

 The great care of all dairy farmers is to prevent an excess of 

 this gas from entering the body. Hence the practice of 

 milking in the field those cows which are distant from home, 

 and of driving home to be milked only such cows as are close 

 to the shed. The exercise required in walking home causes 

 an increased play of the respiratory system, and therefore in- 

 creases the amount of oxygen inspired. This oxygen unites 

 with part of the butter and consumes it. The greatest care 

 is taken by all good dairymen to allow the cows to walk home 

 at their own pace, and never to accelerate it. By this means 

 only a small amount of oxygen enters the system. When a cow 

 is harassed and runs to escape from the annoyance, its milk 

 becomes very much heated, diminishes in volume and in rich- 

 ness, and speedily becomes sour. This is a fact well known 

 to all dairymen. During running the cow respires a large 

 quantity of oxygen. This unites with the butter, and the 

 heat evolved by its combustion elevates the temperature of 

 the milk and evaporates part of its water. The acetous fer- 

 mentation is also induced, and cannot be restrained. For 

 this reason cows are not turned into the fields in very hot 

 weather, when the flies are apt to annoy them and produce 

 restiveness. During such weather, it is not an uncommon 

 practice to feed the cows in the stall during the day and turn 

 them out to grass at night. By this means they are kept 

 tranquil, and prevented from respiring a large amount of 

 oxygen. There cannot be any doubt that the practice of 

 stall-feeding cows during winter or in cold weather must 

 conduce very much to the formation of butter ; but in sum- 

 mer, when the pastures are rich and near the dairy, the 

 slight exercise which they receive increases their health, and 

 with it their appetite. They are thus induced to eat more 

 Phil. Mag. S. 3. Vol. 23. No. 152. Oct. 1843. U 



