43^ SCIENCE AND PRACTICE OF CHEESE-MAKING 



possible, by applying the test to single cows, to ascer- 

 tain which individual or individuals may be the source 

 of trouble. 



Precautions. — Two points must be carefully ob- 

 served in carrying out this test: (i) The tempera- 

 ture must be kept as near 98° F. as possible, in 

 order that the bacteria may develop as desired. 

 This can be done by keeping the temperature of the 

 water surrounding the jars at 100° to 102° F. The 

 temperature must be watched. (2) The thermometer 

 and the knife used should be made. not only clean but 

 sterile each time after using in one sample before 

 placing them in another. 



TEST FOR SPECIFIC GRAVITY AND 

 SOLIDS OF MILK 



^'Milk Testing, etc., pp. 127-132) 



Process of using Quevenne lactometer. — The 



sample of milk to be tested for specific gravity is 

 brought to a temperature between 50° and 70° F. For 

 convenience the milk is placed in a cylinder, which 

 is nearly filled. The lactometer is carefully lowered 

 into the milk until it floats and is allowed to re- 

 main half a minute or more. Then one reads and 

 records (i) the point at which the lactometer scale 

 comes in contact with the upper surface of the milk; 

 and (2) the temperature. The lactometer reading is 

 then corrected, if the temperature is above or below 

 60° F. For example, the lactometer settles in milk, 

 which is at a temperature of 65° F., to the point 

 marked 29. Adding to the reading for correction o.i 

 for each degree above 60° F., which in this case is 0.51 



