MILK SUPPLY 



53 



route wagons or by rail, cards similar to Figure 11 may be 

 mailed to the patrons. The evidence is so conclusive that even 

 the most obstinate patron cannot help admitting his guilt and 

 can usually be induced to "clean up." 



Pifif. 11 



Fermentation Tests. These tests are of great value in the 

 rapid determination of the kind of bacteria with which the milk 

 from individual patrons is contaminated. Glass tubes are rilled 

 one-half full of milk from each patron. These tubes are set in 

 a constant water bath at 100 degrees F. and the changes which 

 milk undergoes are noted after six, twelve and twenty-four hours. 



A solid curd with a clear whey indicates that lactic acid 

 bacteria are the chief organisms and that the milk has been 

 produced under cleanly conditions. These organisms are killed 

 when the milk is heated in the hot wells. Such milk therefore 

 is safe, unless it contains excessive acid, as shown by acid test. 



A curd with gas holes, or that which is torn to pieces in the 

 tubes, shows the presence of gas-producing germs. These come 

 largely from manure and other filth. Among these are Bacillus 

 coli communis, the natural inhabitant of the colon of the animal, 

 and butyric acid organisms which are spore bearers. The latter 

 especially may give rise to serious milk defects, causing "swell 



