No. 6. 



DEPARTMENT OF AGRICULTURE. 



S55 



(f.j Age. There are not available many data giving reliable in- 

 formation in respect to the influence of the age of a cow upon the 

 amount of water in milk. There is more or less variation m differ- 

 ent individuals. From the limited amount of data accessible, there 

 appears to be a general tendency for cows to produce milk with least 

 water during the second period of lactation, after which the amount 

 of watei' in (he milk increases with the age of the animal. 



3. Milk-Fat (or Butter-Fatj. 



1. Milk-Fat a Mixture. — Milk-fat is not a single, invariable com- 

 pound, but is a somewhat variable mixture of several different com- 

 pouods, each of which contains the elements carbon, hydrogen and 

 oxygen, combined in different proportions. Each of these separate 

 compounds, contained in milk-fat, is formd by the chemical union 

 of glycerin with some acid of a particular kind. These glycerin-acid 

 compounds contain about ten different, acids, but some of them 

 are present iii very small quantities; in fact, 90 per cent, of milk-fat 

 is made up of only four of these compounds. We can, in a general 

 way, represent the composition of these four most important gly- 

 cerin-acid compounds of milk-fat in the following manner: 



Glycerin and palmitic acid form palmitin. 

 Glycerin and oleic acid form olci«. 

 Glycerin and myristic acid form myristin. 

 Glycerin and butyric acid form butyrin. 

 These four compounds are present in milk-fat (or butter-fat) in 

 something like the following amounts: 



Palmitin, 40.5 per cent. 

 Olein, 34.0 per cent. 

 Myristin, 10.5 per cent. 

 Rntyriu. 6.2 per cent. 



