94 PRACTICAL DAIRY BACTERIOLOGY 



gradually been emerging a few salient conclusions, which are 

 now practically demonstrated: 



I. The bacterium which produces this disease in cattle and 

 in man is essentially the same. After much experimenting it 

 has been agreed that there are slight differences between bovine 

 and human tuberculosis bacillus. 1 These differences are in 

 minor characteristics, which can be recognized by the bacte- 

 riologists. One of the primary differences is that in experi- 

 menting with animals the bovine bacillus proves to be, as a 

 rule, of a more violent type than the human bacillus. 2 In spite 

 of the slight differences, however, it has been proved that the 

 two types of organisms are so closely related that the germs 

 from either man or cattle may produce the disease in the other. 

 Many instances have been shown where the human bacillus is 

 capable of producing tuberculosis among cattle, although, as 

 a rule, of rather a mild type. The experiments of a reverse 

 nature, by which the bovine bacillus is inoculated into man, are 

 more difficult. A sufficient number of observations along the 

 line of accidental inoculation have shown that in some cases 

 tuberculosis has been produced in man by the bacillus that 

 comes from cattle. 3 The general conclusion, therefore, to-day, 

 is that while there are differences in germs from the two 

 sources, either may be a source of danger to mankind. 



2,. A second question over which a difference of opinion has 

 arisen is whether pulmonary tuberculosis in man is likely to be 

 due to the germs in milk, which are taken into the stomach. 

 The stomach would not naturally be looked on as an entrance 

 to the lungs. But it has been shown that the mode of entrance 

 for pulmonary tuberculosis is not necessarily, as has been fre- 

 quently assumed, through the respiratory organs, but . that at 

 least in many cases, germs entering the body through the 



1 Behring, Romer and Ruppel. Beit. z. Exper. Thierapis, Marburg, 1902. 

 De Schweinitz. 17th Ann. Rep. Bu. An. Ind., 1900. 



2 Miiller-Erfurt. Zeit. f. Fleisch u. Milch Hyg., xii., p. 12, 1902. 

 3 De Schweinitz and Schroeder. Bui. 52, Part II., Bu. An. Ind., 1905. 



