26 MILK [in 



milk-fat, the better the quality of the butter. It has 

 been thought that the composition of the fatty 

 globules of different sizes in milk varies, the fat in 

 the larger globules being of finer flavour than the fat 

 in the smaller globules (see Butter, Chapter VII., 

 p. 114). In experiments carried out at Gottingen 

 by Goetz, the influence of breed on the size of the 

 fat globules has been investigated. Thus it was 

 found that in the milk of a Jersey cow their size 

 varied between -009 and '0042 millimetres ; in that of 

 an East Friesian cow (German breed) from '0063 to 

 0021 millimetres ; and in that of a Simmenthal 

 cow (German breed) from '004 to '0027 millimetres. 

 With respect to the influence of food in causing a 

 variation in the percentage of the fatty acids, a 

 number of experiments have been carried out, 1 which 

 go to show that this is considerable; while with 

 regard to the influence of lactation, it has been found 

 that the maximum percentage of fatty acids in the milk- 

 fat occurs in from five to seven days after calving. 



It may be added, in conclusion, that the colour of 

 the milk-fat varies from white to yellow. If pure 

 milk-fat be kept from the access of air and light 

 for some time it becomes rancid. This is caused 

 by the decomposition of the bodies out of which it is 

 formed, with the result that small quantities of fatty 

 acids, particularly butyric acid, are set free. When 



1 By Mayer, Kirchner, and Ladd. 



