136 Bulletin 65. 



Bang inoculated from 63 tuberculous cows selected for their 

 sound udders, and found the milk of 9 of them infecting. A care- 

 ful microscopic examination revealed tuberculosis in the udders of 

 three of the cows, leaving six giving infecting milk in which even 

 after death, and with all scientific appliances no tubercle could be 

 found in the udder. This is 9.5 per cent, as tested by the micro- 

 scope after death; it was 14.28 percent, as tested by the able 

 veterinary professor during the life of the cows. 



Ernst found 10 cows in 35 with infecting milk though the 

 ndders were sound. In 103 animals in<^ulated ,17 contracted 

 tuberculosis, and of 12 calves sucking the cows 5 became tuber- 

 culous. 



Drs. Smith and Kilborne (Bureau of Animal Industry, Bul- 

 letin No. 3.) found the milk infecting in three cows out of six 

 with apparently sound udders. One infecting cow, and one non- 

 infecting one had each tubercle in the lymphatic gland behind the 

 udder. Forty-four per cent, of the inoculated guinea-pigs con- 

 tracted tuberculosis : i in 5 from one cow, 8 in 10 from another 

 and 6 in 6 from the third 



In my own experience three calves, from healthy parents, suck- 

 ing the apparently sound udders of three cows with general tuber- 

 culosis all contracted the disease. 



It must be allowed that calves sucking the cows run extra risk 

 of infection through their nurses licking them and through feeding 

 from a common trough, but there is the same danger for the ordi- 

 nary milk consumer, since the cow in licking her udder is liable to 

 leave bacilli to fall into the pail at the next milking. 



Again the concentration of the bacillus in the indiluted milk 

 of an infecting cow, renders this much more dangerous than the 

 milk of the same cow diluted, with that of 20, 50 or 100 others. 

 Bollinger and Gebhardt found that milk which infected all ani- 

 mals that took it pure, was apparently harmless when diluted with 

 50 or 100 times its volume of the milk of sound cows. As the 

 bacillus can live in milk this apparent loss of virulence must be 

 largely due to the reduction of the number of bacilli in a given 

 measure of milk, and to their tendency to removal by adhering to 

 the sides of the vessel during the mixing. 



Tuberculous expectoration which is incomparably richer in bacilli 



