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



tute of nitrogen. The " equivalent," as farmers term it, is 

 higher; that is, the cattle are compelled to eat a greater quan- 

 tity of poor than of rich grass, in order to sustain animal heat. 

 They have also to traverse more ground to procure their food; 

 this causes an increased respiration of oxygen and waste of 

 the tissues. Hence the appetite of the animal is increased, 

 and a larger quantity of food is consumed. If the view already 

 given be correct, the waste of the tissues aids in the supply of 

 casein to the milk. One great object in cheese-farms is to 

 induce the cows to eat a large quantity of food, and for this 

 purpose, in large farms, they are tempted with new pastures 

 every day. The Cheddar, Cheshire and Stilton cheeses con- 

 tain a considerable quantity of butter. In a celebrated cheese- 

 farm, a few miles from Bridgewater, where Cheddar cheese 

 is made in great perfection, I found it to be the practice (a 

 prevalent one, I believe) to drive the cows in the morning to 

 the pastures on dry sandy soil, and in the evening to those 

 situated on soft peaty soil. The grass of the sandy soil being 

 poor, the cows traversed considerable ground in procuring it. 

 They therefore eat a quantity more than they would have 

 done on rich land, where there is little exertion required in 

 taking the food. By this means a large quantity of cheese 

 was procured in the milk. But during the night they were 

 allowed to feed on rich pastures, fitted for the formation of 

 butter, and as the darkness prevented them from wandering, 

 little oxygen was respired to consume the butter formed, or 

 to prevent its formation. The milk of the evening and morn- 

 ing being always mixed together in the preparation of the 

 cheese, a proper proportion of both constituents was thus 

 procured. In districts where inferior cheeses are manufac- 

 tured, that is, in which the farmer depends upon his butter as 

 much as upon his cheese, he is ignorant of the value of poor 

 land. Thus it is that there is occasionally a contradiction 

 amongst dairymen with respect to this point, though there is 

 none with those who depend wholly on their cheese, and care 

 little for the butter, except as a means of enriching the former. 

 Chevallier's analysis of woman's milk (the only one of which 

 I am aware) indicates a very small quantity of butter. As 

 attention to diet and exercise must be very important to nurses, 

 when we consider the trivial causes which produce a variation 

 in the composition of milk, I was desirous of ascertaining 

 whether the quantity of butter could be made greater than in 

 the analysis given by Chevallier. Accordingly I selected a 

 farmer's wife, a strong healthy female of twenty-eight years of 

 age, who had been delivered of her third child. On the 19th 

 day after her confinement she remained in bed, and thus di- 



