26 



While floating in tlie air they are drawn into the lungs with the 

 air, and if conditions exist there favorable for their growth and 

 multiplication, they remain, increasing in numbers, attacking the 

 tissues, producing inflammation and in time the peculiar nodular- 

 like growths which are characteristic of tuberculosis. 



The nodules gradually increase in size, finally break down, the 

 " debris " escapes into the bronchial tubes, when by its irritation it 

 produces a cough, by which it is removed. This "debris" from 

 an affected organ containing the germs escaping from the body is 

 the principal means by which the disease is spread from the sick 

 to the healthy. Its destruction by burning or by the use of car- 

 bolic acid or corrosive sublimate solutions affords an easy way of 

 checking the spread of this dire disease. 



Among favorable conditions for the spread and propagation of 

 this disease may be mentioned heredity. AVhile it is extremely 

 rare that tuberculosis is transmitted directly from parent to off- 

 spring, the fact that an animal born of such parents is more liable 

 to contract the disease proves that wliile they do not inherit it, 

 they do inherit a susceptibility of the tissues to favor its contrac- 

 tion and development. In other words the tissues of the body 

 furnish favorable soil for the growth of the germs while the tissues 

 of an animal born of parents not tuberculous do not afford the 

 soil .congenial to the organism. 



When the bacillus gets into the body of the unsusceptible animal 

 or person, instead of flourishing as it would in the body of the 

 susceptible, rendered so by hereditary predisposition, it dies and 

 produces no harm whatever. 



The disease makes the greatest progress among animals kept 

 under bad sanitary surroundings. Badly drained and ventilated 

 stables favor its rapid spread from the fact that the micro-organ- 

 isms are not carried out or diluted by currents of fresh air. The 

 common practice of closing all doors, windows, cracks and other 

 openings through which fresh air may enter a stable, as well as 

 boarding up or otherwise closing the openings in front of the 

 animals, thereby keeping the stable close and preventing an inter- 

 change of air is the surest way of insuring the spread of the 

 disease in a herd when once it has made its appearance. 



Such methods of treating cattle may result in the saving of a 

 small amount of food supplied and a slight increase in milk 

 yield, but it does so at the expense of a weakened constitution and 

 a more susceptible condition of the body for the quick infection 

 and development of disease. 



Too frequent breeding, inand in breeding, forcing, a pro- 

 longed lactation, want of exercise, unwholesome food, impure 



