494 BOARD OF AGRICULTURE. [Pub. Doc. 



be properly disinfected. We also know, from Bang's experi- 

 ments, that when a breeder exercises intelligent care it is pos- 

 sible to raise a healthy herd from a diseased one, and in the 

 mean time much can be done in an educational way to im- 

 prove the existing conditions. 



Ordinarily, for the transmission and development of 

 tuberculosis among dairy cattle long and intimate associa- 

 tion is required. This close and intimate association of the 

 diseased with the healthy is a condition that commonly 

 exists on the average New England farm, the frequency and 

 seriousness of the infection depending on the amount of 

 infectious material present and on the susceptibility of the 

 different individuals in the barn. 



When an animal inhales the dust containing the tubercle 

 bacilli, the bacilli are absorbed through the mucous mem- 

 brane lining the air passages, and usually find lodgement in 

 the bronchial or mediastinal glands. The presence of the 

 bacilli in these glands, or the constant reinfection from the 

 introduction of new bacilli, stimulates the cells immediately 

 surrounding the bacilli, and the result is that a nodule, or 

 tubercle, is formed. The disease may not go any further 

 until from some cause the resisting power of the animal is 

 weakened ; the disease may then develop, and the animal 

 finally falls a victim to tuberculosis. That this is ordinarily 

 the course of the disease is borne out by the fact that in by 

 far the larger number of cases the thoracic glands are found 

 to be the initial seat of the disease, and frequently on post- 

 mortem examination the animal is found to be only very 

 slightly infected. Under such conditions it follows that 

 every precaution should be taken to prevent the develop- 

 ment of these slight localized cases, and anything that tends 

 to undermine and weaken the health of the animals should 

 be avoided. 



In attempting to prevent the spread of the disease, one of 

 the most important matters to be attended to is to endeavor 

 to reduce the amount of infectious material present in the 

 barn, for of course the greater the amount there is present the 

 greater the likelihood that the cows in that barn will become 

 infected ; and, in endeavoring to reduce the quantity of this 

 infectious material, it should be recollected that disinfection 



