192 ELEMENTARY AGRICULTURAL CHEMISTRY 



milk," too, contains very small globules of fat, while the 

 ** strippings " or *' af terings " contain large globules. 



5. Influence of Breed. — It is well known that the milk of 

 certain breeds of cows — e.^., Guernseys and Jerseys — is very 

 rich in fat, while that of others — e.^., Holderness and Holstein 

 Friesians — is notoriously poor in fat. 



The following table gives the composition of the milk of 

 certain breeds, according to various observers : 



Another important difference in the milks of various breeds 

 is in the average size of fat globules. In any one sample of 

 milk there are great variations in the size of these. The 

 average diameters of the fat globules from milk of various 

 breeds of cows during the whole period of lactation are, 

 according to American experiments, as follows : 



Inch. Millimetre. 



Guernsey inrVr 0-00270 



Jersey TrirVr 0-00265 



Devon Tuinr 0*00245 



American Holderness . . ttItt 0-00225 



• Holstein Friesian . . . ^-^^^ 0-00210 



Ayrshire ttit? 0-00205 



This has an important practical effect upon the speed at 

 which the cream rises. The milk of the Channel Island breeds 

 throws up its cream very rapidly ajid such cream is well 



