1 68 BOVINE TUBERCULOSIS 



public halls and waiting rooms, in public conveyances, and on 

 the street. When this expectoration dries it may readily 

 become reduced to powder capable of floating in the air as 

 dust, a grave source of danger to those who inhale it. There 

 is little doubt that this is the chief method of the spread of the 

 disease. The obvious moral to be drawn from this is, — that 

 the greatest care should be exercised by the patient and those 

 who care for him, that the sputum be not allowed to become 

 a source of infection to others. 



If the disease is transmitted from man to cattle it is doubt- 

 less by the same means as from man to man. 



DIAGNOSIS 



In dealing with tuberculosis from a practical standpoint, the 

 detection of its presence is, of course, of the highest import- 

 ance. In advanced cases there is no difficulty in deciding that 

 there \s some^/ii?^^' wrong with the animal. It loses flesh, it 

 loses its sleekness of coat, and has the general appearance of 

 being out of condition. If it is the lungs which are affected, 

 there is likely to be a cough, which is especially noticeable 

 after getting up or after active exercise, there are likely to be 

 diseased glands in the throat, which show their presence by 

 swelling or which can be detected by the touch. One who is 

 accustomed to the practice can by placing an ear against the 

 walls of the chest, decide by the peculiarity of the sounds 

 which he hears, whether the lungs are solidified or broken 

 down, or contain abnormal secretions, or have their surfaces 

 which come in contact with the walls of the chest roughened ; 

 all of these are conditions which may be present in tubercu- 

 losis. The presence of all the foregoing so-called " physical " 

 signs, can, in the majority of cases, establish only the proba- 

 bility of tuberculosis. However, there has been discovered, 

 tried, and approved a means of detecting the disease, even in 

 its earliest stages, when its detection by physical examination 

 would be impossible. This means is what is known as the 

 tuberculin test. 



TUBERCULIN TEST 



The general fact on which it is based is this : Bacteria 

 under certain conditions produce new substances which are 



