124 MODERN METHODS OF TESTING MILK 



in the test-cup, setting it in a level position and allow- 

 ing the milk to run out at the bottom. Taking the bot- 

 tle of diluted rennet in one hand and the spatula in 

 the other, watch the level of the milk in the cup. The 

 moment the upper surface of the milk drops to the 

 zero mark, pour the diluted rennet into the milk and 

 stir well. Then leave it alone. When the milk coagu- 

 lates, it stops running through the glass tube. From 

 the graduated scale, read the number of spaces un- 

 covered on the inside of the cup, showing how many 

 divisions of milk have run out. The more slowly the 

 milk coagulates, the larger the amount that runs out; 

 the more quickly the milk coagulates, the smaller the 

 amount that runs out and the fewer spaces there are 

 uncovered. When about 2^ spaces are uncovered, 

 the milk is ready for addition of rennet. The tempera- 

 ture must be watched, being tested at the start and 

 finish, especially in a cold room. 



Some objectionable features of the Marschall test 

 should be noticed. A difference in the size of the bore 

 of the glass tube in the bottom of the cup obviously 

 makes a difference in the results. It is found that the 

 size of the bore of the glass tubing varies in different 

 cups. Therefore, the results given by one cup can not 

 be compared with those of another, unless they arc 

 tested on the same milk and found to agree. Special 

 pains must be taken to keep the tube open, since a lit- 

 tle dirt quickly stops it. The Marschall test is con- 

 venient for ordinary work, but is not capable of as 

 great delicacy as is the Monrad test. Results obtained 

 by different workers can be compared by the Monrad 

 test, but not by the Marschall test. 



