MILK AND CREAM. 257 



time for the butter particles to rise to the surface, and 

 they remain mixed up with the curd. 



935. When exposed to a warm atmosphere, milk readily 

 becomes sour, its sugar of milk becoming what is called 

 lactic acid. It is this sugar and the chemical changes to 

 which it gives rise, that make milk susceptible of under 

 going all degrees of fermentation, and of being made into 

 a fermented and palatable but intoxicating liquor, which 

 on distillation produces pure alcohol. 



936. Milk will generally yield from ten to fifteen per 

 cent, of its own volume of cream, the average being 

 about twelve and a half per cent. Eight quarts of milk 

 of average richness, will therefore give about one quart 

 of cream. But the milk of some cows fed on rich food, 

 will far exceed this, sometimes furnishing twenty per cent, 

 of cream, and in very rare instances, twenty-live and 

 twenty-six per cent. The quantity of cream to be obtained 

 from milk is much more uniform than the quantity of 

 butter from cream. Rich milk is lighter in weight than 

 poor. 



937. The temperature of milk as it comes from the 

 cow is about blood heat, or ninety-eight degrees of Fahren 

 heit, and it should be cooled as little as possible before 

 coming to rest in the pan. The depth of milk in the pan 

 should be shallow, not greater than two or three inches. 

 A moderate warmth and shallow depth facilitate the rising 

 of the cream. The temperature of the dairy room should 

 not vary much from fifty-eight degrees. 



938. Milk is extremely sensitive to external influences, 

 and hence the utmost cleanliness is necessary to preserve 

 it for any length of time. The pails, strainers and pans, 

 the milk room, and in short all the surroundings, must 



