132 MILK AND ITS HYGIENIC RELATIONS 



in milk was formulated by Trommsdorff. In this method the 

 cells were not counted, but the depth of the layer obtained after 

 centrifuging was noted. It was believed that an increase in the 

 depth of the layer over what was believed to show a normal cell 

 content denoted disease of the udder. 



Later investigations as to the value of this method as the sole 

 means of diagnosis tend rather to show that no one method of in- 

 vestigation can satisfactorily establish the presence of disease of 

 the udder as shown in the milk. A high cell content alone may not 

 denote any pathological condition, but when associated either with 

 many streptococci or with an increased ferment or immune-substance 

 content of the milk, there is increased probability, amounting 

 perhaps when well marked to a certainty, of the presence of udder 

 trouble. The application of these methods will evidently provide 

 useful information, only when applied to the milk obtained either 

 from one cow or from a comparatively small number of cows. In 

 mixed milk or in market milk, the milk from one unhealthy udder, 

 even though when examined alone it should show a very high 

 cell [content or a high content of the factors above considered, 

 will pass undetected when mixed with a larger quantity of milk, 

 since there will be much dilution of the excess substance or sub- 

 stances. Even where suspicion has been shown to attach to three 

 or four cows only, it has been necessary to obtain milk separately 

 from the individual cows, and frequently also from the individual 

 quarters of the udder, in order to locate the site of the disease. 



The work of Bauer, Sassenhagen, and others 1 shows that 

 changes may occur in the milk before any evidence of inflamma- 

 tory condition can be detected clinically in the udder. The udder 

 trouble was sometimes only detected several days after changes 

 had been found in the milk. Admitting for the moment that dis- 

 covery of such changes in milk obtained from an apparently healthy 

 udder denoted the onset of early mastitis, it is doubtful whether 

 such a discovery affords a method of practical value in dealing with 

 an ordinary milk supply. It is evidently impossible to estimate 

 separately either the bacterial content or the ferment content or 

 the cell content of the milk of each cow at sufficiently frequent inter- 

 vals to be able to eliminate a cow suffering from early mastitis. 



The real value of such tests would appear to lie in the aid afforded 

 in the detection of disease in a cow whose milk had probably been 

 the source of disease in human beings, such disease having been 

 traced to the milk from a special farm, and, by a process of 

 elimination, to a particular cow. In such cases, however, it is 

 probable that some evidence of a pathological condition would 

 be obtained as a result of careful veterinary examination. The 

 tests mentioned become extremely valuable as confirmatory 

 evidence of early disease of the udder, and may lead to a more 



1 See pp. 99, 100, 112. 



