208 CHYMISTRY APPLIED TO AGRICULTURE. 



degrees of richness and different tastes : the milk of a cow 

 which is fed upon the leaves and stalks of maize, or upon 

 the refuse of beets, is very sweet, and that of a cow nour- 

 ished with cabbages has not so sweet a taste, and exhales a 

 disagreeable odor; the milk of cows which browse damp 

 meadows is watery and insipid : from these facts we may 

 establish as a principle, that the quality of milk may be so 

 varied by the choice of food, as to adapt it to the wants of 

 the individual to be nourished by it, whether he be a healthy 

 man or an invalid. 



The numerous experiments that have been made by Messrs. 

 Deyena and Parmentier to ascertain the effect of food upon 

 the milk of a cow, furnish the following results : 



1st. That it is improper to change suddenly the kind of 

 food, as it for a time diminishes the quantity of milk, even 

 though the food be more succulent and of a better kind. 



2nd. That all plants do not give to milk their characteris- 

 tic qualities, and that there are some that do not exercise 

 any particular action upon either of the constituent princi- 

 ples of milk. 



By distilling milk in a water-bath there is obtained an ex- 

 tract of limpid liquor of about ^ the weight of the milk em- 

 ployed, having the odor peculiar to milk, and containing a 

 putrefiable animal substance which gradually renders the 

 color of the extract cloudy, and its consistence viscid ; this 

 substance becomes putrescent in a longer or shorter time, 

 according to the nature of the food upon which the animal 

 affording the milk is nourished. 



This first distillation does not change the nature of the 

 constituent principles of milk;, they remain in an oily mass 

 of a sweetish taste, and a yellowish white color. 



Butter and cheese are the two principal elements of which 

 milk is composed ; the cream which is separated from the 

 milk, and from which a most profitable product is obtained, 

 contains only one of them, butter, which is the most impor- 

 tant part of the cream, and is obtained from it by a very sim- 

 ple process : the whey which remains after the butter and 

 cheese have been separated from the cream, contains in so- 

 lution some salts, and serves as a vehicle or dissolvent for 

 all the constituent principles of milk. 



The principles contained in milk are not united by a pow- 

 erful affinity ; when milk is allowed to remain at rest, the 

 butter becomes disengaged and rises to the top, where it 

 forms a layer in which it is found mixed with some milkj 



