INFLUENCE OF DISEASE UPON MILK 87 



culous cows is diluted more or less with the milk of non- 

 infected cows. The extent of the dilution will depend 

 upon the method of handling the milk. Ordinary mar- 

 ket milk, however, is frequently the mixed milk of sev- 

 eral herds, but at any rate it is the mixed milk of a number 

 of cows in the same herd. It has been demonstrated that 

 the milk of cows affected with advanced or extensive 

 tuberculosis of the udder may render the entire supply 

 infectious when mixed with milk from other cows which 

 are not tuberculous ; but this is not true of milk from cows 

 which do not show clinical symptoms of the disease. 

 Miiller and Hessler examined by inoculation samples 

 of mixed milk from 2949 herds, each sample representing 

 the milk from 30 to 200 cows. Tubercle bacilli were 

 present in the samples from 156 herds. All of these 

 herds except five were found to contain cows affected 

 with udder tuberculosis or other forms of open tuber- 

 culosis. In the five herds in which tuberculosis was not 

 established clinically, Hessler is of the opinion that the 

 tubercle bacilli were eliminated in the fasces by cows with 

 incipient cases of open lung tuberculosis which had not 

 yet become perceptible. The other 2793 herds, in the 

 milk samples from which tubercle bacilli were not demon- 

 strated, certainly contained a considerable number of 

 cows which would have reacted to the tuberculin test, 

 judging from the extent to which tuberculosis was known 

 to exist in the district in which they were located. 



Delepine examined the milk from 1385 farms and 

 found tubercle bacilli in the samples from 294 farms. 

 The cattle on 276 of these farms were examined and on 

 190 farms one or more cows were found affected with 

 tuberculosis of the udder, a bacteriological examination 

 of the individual milk being necessary in some cases to 



