Testing Mttk on the Farm. 149 



teat, or by filling the bottle with a little milk from each 

 teat, or by taking some of the first, middle and last milk 

 drawn from the udder. Such samples cannot possibly 

 represent the average quality of the milk of one entire 

 milking, since there is as much difference between the 

 first and the last portions of a milking, as between milk 

 and cream. 1 Lack of care in taking a fair sample is 

 the cause of many surprising results obtained in testing 

 the milk of single cows. 



169. Composite samples. When a cow is to be tested, 

 she should be milked dry the last milking previous to 

 the day when the test is to be made. The entire quan- 

 tity of milk obtained at each milking is mixed and 

 sampled separately. On account of the variation in the 

 composition of the milk, a number of tests of successive 

 milkings must be made. As this involves considerable 

 labor, the plan of taking composite samples is prefer- 

 able; the method of composite sampling and testing is 

 explained in detail under the second subdivision of 

 Chapter X (180) ; suffice it here to say that the method 

 followed in the case of single cow's or herd milk is to 

 take about an ounce of the thoroughly mixed milk of 

 each milking; this is placed in a pint or quart glass jar 

 containing a small quantity of some preservative, prefer- 

 ably about one-half a gram (8 grains) of powdered 

 potassium bi-chromate. If a number of composite sam- 

 ples of the milk of single cows are taken, each jar should 

 be labeled with the number or name of the particular 



1 Woll, Handbook for Farmers and Dairymen, p. 249; Agricultural 

 Science, 6, pp. 540-42. 



