4 BUTTER-MAKING AND COMPOSITION OF MILK 



ammonium hydrate and kept at a temperature of 60 C. for 

 about twenty minutes, it assumes an intense red color. Cow's 

 milk turns faintly yellow if treated in the same way. This test 

 was reported by Unikoff, of St. Petersburg (now Petrograd), at 

 the meeting of the Medical Section, Royal Academy of Med- 

 icine, in Ireland. The various kinds of milk also differ from 

 each other in their behavior towards rennet. Richmond has 

 divided milk into two classes: Class I includes milk from the 

 ewe, buffalo, goat, and cow. When rennet is added to the 

 milk from these animals, the casein coagulates into a firm curd. 

 Class II includes human milk, milk of the ass, and mare. 

 When rennet is added to the milk of these animals, a soft curd 

 or none at all is formed. The latter class seems to include the 

 animals without horns, while the first includes those with horns. 



As the cow's milk is used as a food to a greater extent than 

 that of any other animal, it has been subjected to more extended 

 and more careful investigation, and, as a consequence, more 

 definite knowledge has been obtained concerning its composition, 

 properties, and uses. The succeeding discussions have reference 

 to cow's milk, if not otherwise stated. 



Composition of Milk. It is impossible to get accurate figures 

 on the composition of milk, as each of the milk constituents is 

 subject to fluctuation from various conditions, such as individ- 

 uality of cow, breed, season of the year, stage of lactation, milking 

 and environment. 



The average composition, as determined by 280,000 analyses 

 reported by Richmond is as follows: 



Water ......................... 87.35 



Fat ............................ 3-75 



Milk-sugar ..................... 4 . 70 



Casein ' .oo 



Proteids 



1 Albumen, etc .......... 45 



Ash ............................ 75 



The composition of various kinds of milk is given by Konig as 

 follows: 



