126 Testing Milk and Its Products. 



vided; they are plainly numbered or tagged, one jar 

 being provided for each lot of milk to be tested. The 

 jars are filled about two-thirds full with the milk from 

 the various sources; it is not necessary to take any exact 

 quantity; they are then placed in a water tank, the water 

 of which is heated until the milk in the jars has a tem- 



FIG. 44. Students operating the Wisconsin curd test 



perature of 98 F. The thermometer used must not be 

 transferred from one sample to another, unless special 

 precautions are taken, for fear of contaminating the pure 

 lots of milk by impure ones. 



When the milk has reached a temperature of 98, add 

 to each sample ten drops of rennet extract, and mix by 

 giving the jar a rotary motion. The milk is thus cur- 



