290 BACTERIOLOGICAL ANALYSIS OF MILK. 



The results obtained by these methods give the amount 

 of dried dirt, but does not of course represent the original 

 quantity of filth, which ,was at the outset in a moist condition. 

 To obtain the moist weight of the filth it is necessary to 

 multiply the figures obtained at the end by a certain factor 

 which will reduce it to the weight of ordinary moist material. 

 This, of course, will be a variable one according to the 

 material of which the dirt is composed, but a rough approxi- 

 mation may be obtained by multiplying the dry weight by 

 the factor 7, which will produce a result not very far out of 

 the way. 



The amount of filth that is found in milk tested by these 

 methods is subject to the widest variation, as would be ex- 

 pected in accordance with the conditions of cleanliness in the 

 dairy. In some samples tested the amount has been found 

 to be as small as 2 mgs. per liter ; on the other hand, in some 

 samples of fresh milk obtained in a moderately clean dairy, 

 but without any precautions and without straining the milk, 

 the amount is sometimes as high as .3 of a gram or more. 

 This number is very high and indicates an excessive amount 

 of dirt. 



