TESTING 329 



whole milk. This is known as a whole-milk bottle. It 

 is graduated from to 8 per cent. All of the glass- 

 ware should comply with the laws. 



309. Sampling the milk. One of the most important 

 parts of testing is to obtain a fair sample of the milk. 

 The milk to be tested may be in a vat or in a farmer's 

 can or a composite sample jar. If the milk is bought 

 on the fat basis, that of each patron is not tested daily, 

 but a small quantity, about half an ounce, is taken 

 each day and placed in a jar; this is known as a com- 

 posite sample. It is the usual practice to number the 

 patrons and have a sample bottle for each patron with 

 his number on it. Some substance must be added to 

 preserve the milk and to keep it from souring or coagu- 

 lating. It is difficult to secure a fair sample of sour milk. 

 A wide-mouthed jar is preferred for keeping milk samples. 

 This must be kept closed to prevent evaporation. Each 

 day when milk is added to the composite sample, the 

 bottles should be shaken to prevent the cream drying. 

 Composite samples are tested at least twice a month. 

 The milk may be mixed to obtain a fair sample, by stir- 

 ring in the vat or by pouring from one bottle to another. 

 Vigorous shaking should be avoided as this is likely to cause 

 churning. One should see that all the cream is removed 

 from the sides of the sample bottle and that it is evenly 

 distributed through the milk. The sample of milk is 

 now measured out with the pipette. This is graduated 

 to deliver 18 grams of milk, and holds 17.6 c.c. Hold the 

 pipette between the thumb and second finger of the right 

 hand with the tip below the surface of the milk, draw the 

 milk by suction with the lips until it is filled well above 

 the graduation. Quickly place the forefinger over the 

 opening and at right angles to the pipette. By gently 



