Adulteration. 213 



should never be given, except after a most intimate knowledge of 

 the special conditions. 



Milk mixed from many cows has to be judged differently from 

 milk of one or a small number of cows, because in the latter case 

 the fluctuation through internal or external influences may be very 

 marked, whereas the presence of abnormal secretions from one or 

 several cows is either modified or concealed through mixing their 

 milk with that from many healthy cows. 



An adulteration should never be established or the degree of 

 adulteration calculated, without making comparative tests of satis- 

 factory samples from the same source. A definite diagnosis of the 

 degree of adulteration based merely on the values of accepted 

 averages, normal or experimental, would be erroneous, of which 

 no scientific milk inspector should be guilty. 



Before the beginning of the examination, each sample should 

 be sufficiently mixed by shaking, without having any considerable 

 amount of air shaken into the milk. 



The testing of milk is divided into the preliminary examina- 

 tion and the special scientific examination. 



Through tests by means of the senses milk is first examined 

 as to the color. Adulterated market milk is often bluish, and 

 secretions from animals with udder diseases often make the milk 

 reddish. 



The odor is determined either immediately after emptying 

 the cans or in the laboratory by heating the milk in glass beakers 

 up to the formation of steam. The odor of good and palatable 

 market milk may even vary considerably. If, however, special 

 odors are very conspicuous, the presence of certain milk defects 

 must be considered, possibly as the result of bacterial action. 



The consistence of the milk should not be too thin or watery, 

 (suspicion of adulteration), and neither should it be sticky, slimy, 

 greasy or curdling, which changes indicate diseases, particularly 

 udder affections, or the presence of certain bacteria of milk which 

 have propagated since the milk was secreted. 



A fine vesicular foam appearing after shaking should rapidly 

 become large bubbles and disappear. The remaining fine vesicular 

 foam is the result of shaking soapy milk. 



The taste is to be judged in the same manner as the odor. The 

 milk should be delivered and sold in a cold condition, and therefore 

 in the collection of all samples of milk the temperature should be 

 ascertained. 



With market milk the positive result of the boiling test, that 

 is when the milk curdles, is a sign of advanced decomposition (10 

 to 12 degrees of acidity according to Henkel-Soxhlet). 



With the fresh milk of individual cows, curdling after boiling 

 indicates inflammation of the udder, the curdling being mostly 

 limited to the milk of individual quarters or to the colostral milk 

 at the beginning or at the end of lactation. 



