142 



Testing Milk and Its Products. 



the specific gravity of the samples can also be correctly 

 taken (113). 



^. - 167. Size of the testing sample. Four ounces is a suffi- 

 c.ent quantity for a sample of milk if it is desired to 

 determine its per cent, of fat only; if the milk is to be 

 tested with a lactometer, when adulteration is suspected, 

 as much as a pint is needed for a sample. If this sample 

 of milk is put into a bottle and carried or sent away from 

 the farm to be tested, the bottle should be filled with 

 milk clear up to the cork to prevent a partial churning 

 of butter in the sample during transportation (30). 



168. Variations in herd milk. While considerable vari- 

 ations in the quality of milk of single cows are often met 

 with, a mixture of the milk of several cows, or of a whole 

 herd is comparatively uniform from day to day; the indi- 

 vidual differences tend to balance each other so that vari- 

 ations, when they do occur, are less marked than in case 

 of milk of single cows. There are, however, at times 

 marked variations also in the test of herd milk on suc- 

 cessive days; the following figures from the dairy tests 

 conducted at the World's Columbian Exposition in Chi- 

 cago in 1893 illustrate the correctness of this statement. 

 The test included twenty -five Jersey and Guernsey cows 

 each and twenty -four Shorthorn cows. 



Tests of herd milk on successive days. 



