Dr. Lyon Playfair on the Milk of the Cow. 287 



ments, it is necessary that we should examine the composition 

 of the various kinds of food given to the cow. The cow re- 

 ceived, during the course of the experiments, grass, oatmeal, 

 hay, beans, and potatoes. The following analysis exhibits the 

 composition of these various substances. 



Hay. Oats. 



Boussingault. Boussingault. Playfair. 



41-57 



5-25 



30-10 



1-80 



3-28 



18-00 



In a specimen of beans analysed by Boussingault, only 4 

 per cent, of nitrogen was found. But in the bean-flour, 

 which I used in the experiments, there was as much as 5 

 per cent. It is obvious that if we multiply the quantity of 

 nitrogen by 6^, the product will be the amount of casein or 

 albumen in the various kinds of food ; and further, by deduct- 

 ing this, together with the water and ashes, the remainder 

 must indicate the quantity of unazotised matter. 



Albumen or casein. Unazotised matter. 



Hay . . 7-81 68'63 



Oats . .11-16 67-56 



Beans . . 31-00 51-18 



Potatoes . 1-98 24-42 



Finally, according to Liebig, good hay contains 1-56 percent. 



of a fatty or waxy substance. Braconnot found 0*70 per 



cent, of a similar substance in beans. Vogel found 2 per 



cent, in oats, and Liebig 0-3 per cent, in potatoes. 



Dumas, in an announcement to the French Academy, has 

 lately advanced the theory, that the fat of animals is wholly 

 derived from the fatty matter contained in their food. This 

 opinion has been very ably combated by Liebig, who refers 

 to an analysis of milk executed by Boussingault, and shows 

 that much more butter was contained in it than could be 

 accounted for by the fat in the food taken. As the theory of 

 the formation of fat is of the first importance in the practice 

 of dairy farming, we will shortly examine Dumas's theory 

 with reference to the preceding experiments. 



1 . On the 2nd day the cow received 28 lbs. of hay, which 

 contains 0*436 lb. of fat and 2| lbs. of oatmeal, containing 

 0"050lb. of the same constituent. The cow produced (cal- 

 culating according to its specific gravity) about 19 lbs. of 

 milk, in which was 0*969 lb. of butter. But the food altogether 



