150 



Bulletin 225. 



the same species. The Royal Commission on tuberculosis, appointed 

 by the King of England in 1901, has recently made a partial report 

 in which they state that they have been unable to find any difference 

 in the disease-producing power of the bacilli from human and from 

 bovine sources. 



This bacillus seems to be able to live for some time in dark and 

 damp places. It is readily killed with a five per cent solution of 

 carbolic acid, or a 1 to 1,000 solution of corrosive sublimate. Sunlight 

 and dr}^ air are not favorable for its existence outside of the body. 



The tubercle bacilli escape from the diseased animal in the saliva 

 and mucus from the mouth when the lungs or certain glands are dis- 

 charging into the respiratory 

 tract. They escape in the pus 

 from tubercular abscesses that 

 open through the skin, and in 

 the milk. Dr. Salmon has 

 recently stated that all of the 

 examinations that have been 

 reported of milk from tuber- 

 culous cows show that about 

 15 per cent of them give off 

 tubercle bacilli with their 

 milk at some time during the 

 course of the disease. The 

 udders show tuberculosis in 

 about two per cent of the 

 cases. 



2. The Method OF Infection. 



Animals become infected 

 with tubercle bacilli largely 

 through the digestive tract. 

 The infection by means of 

 inhaling particles of dirt 

 or dust carrying tubercle 

 bacilli, or by getting them into wounds of the skin, is possible 

 but certainly not very common. Healthy cattle "nosing" with 

 infected ones or feeding and drinking after them is supposed to 

 be the most usual method of infection. The infection of calves 

 b}' feeding them milk from tuberculous cows is not an infre- 

 quent means of propagatiiig the disease. The slow development 

 of the disease makes it possible for calves to be infected and frequently 



Fig. 32. — A drawing of a heart of a steer 

 that ivas killed for beef. The heart 

 muscle is entirely surrounded by a dense 

 mass of tubercidar deposit. There were 

 no other lesions found in the animal. 



