140 Testing Milk and Its Products. 



ing, 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 milk 

 of single cows. 



165. 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 quantity of milk obtained at 

 each milking is mixed and sampled separately. On ac- 

 count of the variations 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 preferable; the method of compos- 

 ite sampling and testing is explained in detail under the 

 second subdivision of Chapter X (176); suffice it here to 

 say that the method followed in case of single cows' or 

 heid milk is to take about an ounce of the thoroughly 

 mixed milk of each milking; this is placed in a pint or 

 quart fruit jar containing a small quantity of some pre- 

 servative, preferably about one-half a gram (8 grains) of 

 powdered potassium bi-chromate. If a number of com- 

 posite samples of the milk of single cows are taken, each 

 jar should be labeled with the number or name of the 

 particular cow. Composite tests are generally taken for 

 four days or for a week. If continued for a week, the 

 jars will contain at the end of this time a mixture of the 

 milk of fourteen milkings. The composite sample is 

 then carefully mixed by pouring it gently a few times 

 from one jar to another, and is tested in the ordinary 



i Woll, Handbook for Farmers and Dairymen, p 194; Agricultural 

 Science, 6, pp. 540-42. 



