128 MILK AND THE PUBLIC HEALTH chap. 



years or more, with possibly rare exceptions, are active agents for 

 the dissemination of tubercle bacilli. 



The English Eoyal Commission on Tuberculosis ^ reports 

 similar results. Their experiments were made with the milk 

 of 6 cows which had contracted tuberculosis in the natural 

 way. Three of the animals showed clinical signs of tuberculosis, 

 but in none of the 6 could tuberculosis of the udder be 

 detected during life. 



The faeces of all 6 cows, obtained under conditions pre- 

 cluding contamination from the genito-urinary passages, were 

 used to inoculate guinea-pigs and to feed guinea-pigs and young 

 pigs. The faeces of 5 of these animals were found to contain 

 living and virulent tubercle bacilli. The three which were 

 suffering from severe tuberculosis were eliminating large 

 numbers of tubercle bacilli. This was shown by the occur- 

 rence of tuberculosis after the inoculation of very small doses 

 of faecal matter in all but one of the guinea-pigs which sur- 

 vived a sufficient length of time, and by the fact that all the 

 swine fed became tuberculous. 



The milk of 5 of the cows was used to inoculate guinea- 

 pigs, some rabbits, and some young pigs. The milk of 2 of these 

 animals (both severely diseased) caused, though not invariably, 

 tuberculosis in guinea-pigs inoculated with relatively small 

 doses. Post-mortem, the udders revealed no signs of tuber- 

 culosis. The milk of a third cow caused severe tuberculosis 

 in every guinea-pig inoculated, but the animal was very ill at 

 the time the milk was collected, while post-mortem, four small 

 nodules were present in one quarter of the udder. The milk- 

 of the remaining 2 cows did not give rise to tuberculosis in 

 any of the animals inoculated. Both were suffering from 

 tuberculosis of lungs and mediastinal glands. 



The Commissioners sum up the matter in regard to 

 tuberculous cows with no udder disease by saying : 



Cows suffering from extensive tuberculosis of the lungs must 

 discharge considerable numbers of bacilli from the air passages in 

 the act of coughing, and some of the bacilli thus expelled may find 

 their way into the milk. But our experiments indicate that the 

 excrement of cows obviously suffering from tuberculosis of the 

 lungs or alimentary canal must be regarded as much more dangerous 



' Third Interim Iteport, 1909. 



