THE EFFECT OF FOOD ON MILK. 557 



Phosphate of lime, . . . 0.310 0.344 



Phosphate of magnesia, . . 0.042 0.064 



Phosphate of iron, . . . 0.007 0.007 



Chloride of potassium, . . 0.144 0.183 



Chloride of sodium, . . 0.024 0.034 



Soda, .... 0.042 0.045 



0.569 0.677* 



The following experiments, made by Playfair at the same 

 time, illustrate the general effect of food on the milk, and dis- 

 prove the idea of Dumas, that the fat of animals is wholly 

 derived from the fatty matter contained in their food : 



" 1 . On the second day the cow received 28 Ib. of hay, 

 which contained 0.43 Ib. of fat, and 2J Ib. of oatmeal, contain- 

 ing 0.050 Ib. of the same constituent. The cow produced 

 (calculating according to its specific gravity) about 19 Ib. of 

 milk, in which were 0.969 Ib. of butter. But the food alto- 

 gether contained only 0.486 Ib. of fat, so that 0.483 Ib. of 

 butter must have been produced from other sources. 



" 2. The food received by the cow on the third day con- 

 sisted of 28 Ib. of hay, 2J Ib. of oatmeal, and 8 Ib. of bean- 

 flour. 



28 Ib. of hay contain . . . 0.436 Ib. of fat. 



2^ oatmeal . . . 0.050 



8 beans, . . . 0.056 



In the food, . . 0.542 



The milk of that evening amounted to 10.341b., and contained 

 0.4 Ib. of butter; that of the morning to 11.61 Ib., and con- 

 tained 0.5 Ib. of butter, the whole amounting to 0.9 Ib., of 

 which only 0.542 Ib. could possibly have been furnished by 

 the food, assuming that the fat in the food could only be con- 

 verted into butter. 



* ' English Journal of Agriculture,' vol. xiii. p. 24. 



