70 DAIRY BACTERIOLOGY 



bovine tuberculosis in general (in Denmark 30 to 50 per cent, of 

 the cows are affected in one form or another), it is no wonder that 

 tuberculosis of the udder is often met with. Generally speaking, 

 large herds seem to be affected the most. As udder tuberculosis 

 makes rapid progress, the cows from which nursery milk is 

 obtained should be examined by a veterinary surgeon at least once 

 a fortnight. Owing to the dangerous nature of this disease, the 

 Danish law orders the slaughtering of cows with tuberculous 

 udders. Tuberculosis of the udder is, however, not the only form 

 of the disease which may involve the infection of the milk with 

 tubercle bacteria. This may also very well happen in cases of 

 tuberculosis of the uterus and kidney or the intestine, and even 

 tuberculosis of the lungs may be dangerous in this respect as the 

 animals swallow most of the slime which they bring up, with the 

 result that the bacteria pass into the manure. Every form of 

 open tuberculosis must therefore be regarded as a source of danger 

 as far as the milk is concerned. As tubercle bacteria do not grow 

 at temperatures much below blood heat, they will not multiply, in 

 milk or milk products under normal conditions, but as they are 

 not killed by small amounts of lactic acid they can live in butter- 

 milk. In the separating of milk the majority of the tubercle 

 bacteria are removed with the separator slime, though appreciable 

 numbers pass into the cream while only very few remain in the 

 separated milk. Raw milk is on this account less dangerous than 

 raw cream or butter. Tubercle bacteria can live in butter for a 

 much longer period than it is usually kept nowadays. In cheese 

 making the great majority of the bacteria as well as fat globules 

 are precipitated with the curd, for which reason milk and especially 

 fresh cheese may be far more dangerous than whey. According 

 to Harrison 1 , the hard cheeses may contain virulent tubercle 

 bacteria even after keeping for two months. The latest researches 

 have established that the organisms of human and bovine tuber- 

 culosis are different varieties, the latter being less dangerous to 

 adults than was formerly supposed though dangerous to children. 

 Tuberculosis is usually contracted by adults through inhaling the 

 dried saliva of consumptive persons. On the other hand, bovine 

 tuberculosis is very dangerous to calves and pigs, for which 

 reason a law was passed in Denmark at the suggestion of Professor 

 B. Bang, ordering all dairies to heat separated milk and buttermilk 

 to 80 C. before returning it to the farmers, who use it chiefly for 

 feeding pigs. It is regarded as a matter of the greatest importance 

 that pathogenic germs are excluded from Danish butter in a 

 similar manner. 



1 " Landwirtschaftliches Jahrbuch der Schweiz," 1900, p. 317, 



