72 PRACTICAL DAIRY BACTERIOLOGY 



by different observers do not agree very closely because of 

 slight differences in technique. Figure 35 shows the amount 

 of dirt collected under the udder of a cow during milking, both 

 with, b, and without, a, previous washing of the udder. The 

 amount is certainly sufficient to emphasize the importance of 

 this source of bacterial contamination. 



The determination of the amount of dirt in milk certainly 

 gives a gauge as to the care exercised in its. production. But 

 whether such dirt determination can be of any value in the 



FIG. 35 RELATIVE AMOUNT OF DIRT FALLING FROM THE UDDER DURING 



MILKING, UNDER DIFFERENT CONDITIONS 

 A. Udder muddy. B. Udder slightly soiled. One-half natural size. (Fraser) 



municipal testing of milk is somewhat questionable. It is not 

 yet possible to give any standard as to the amount of dirt that 

 may be allowed in passable milk, and there seems to be no 

 reason for believing that the dirt determination will be adopted 

 as one of the methods of municipal examination of market milk. 

 If milk is allowed to stand for several hours in a glass jar until 

 the dirt settles at the bottom, an examination with the naked 

 eye will give the relative amount of dirt, and the results will 

 probably be as valuable as the longer laboratory methods of 

 determining the quantity, especially when it is remembered that 

 the amount of dirt thus obtained varies quite widely with dif- 

 ferent experimenters and different methods. Special dirt filters 



