Bovine Tuberculosis. 115 



infected with tuberculosis but which appear to be sound. There may be 

 others in which the disease is far advanced and the animals show that they 

 are affected. There are two ways by which the disease can be detected, 

 namely, by a physical examination and with tuberculin. 



The physical examination is of value in advanced cases only, or when 

 the diseased part is in evidence, as for example in the lymphatic glands of 

 the head. Experience has shown that by this method one is unable to 

 find more than a very small percentage of the animals that are tuberculous 

 and a menace to the healthy cattle. This method, therefore, is a very 

 crude one and cannot be trusted except in the very advanced cases and in 

 those in which the early stages of the disease are in evidence externally. 



The tuberculin test is far more reliable. There have been many 

 unjust things said about tuberculin and many cattle owners have come to 

 fear that it is a dangerous agent to use. Much of this fear came from 

 statements made regarding its possible ability to stimulate latent nodules. 

 The work of the last ten years has not confirmed the earlier opinions but 

 to the contrary it has shown that tuberculin in proper doses is as harm- 

 less as need be to the health of the cattle. The dangers that are supposed 

 to come from it are the results of poor tuberculin, unclean instruments, 

 carelessness, or other avoidable causes. 



Tuberculin. Tuberculin is the liquid, usually glycerinated bouillon, 

 on which the tubercle bacilli have multiplied or grown. It is concentrated 

 after heating and removing the bacteria and a little carbolic acid or thy- 

 mol is added to preserve it. The active principle of tuberculin is a sub- 

 stance resulting from the multiplication and maceration of the tubercle 

 bacilli in the liquid. In its preparation it is necessary that the tubercle 

 bacilli " grow " sufficiently, which usually requires several weeks before 

 the liquid is used. The flasks containing " cultures " as they are called, are, 

 when ready, heated for some time at the boiling point. The liquid is then 

 filtered to remove the bacilli, the fluid is then concentrated over a water 

 bath. It is again filtered through a porcelain filter and stored. It will be 

 noticed, that tuberculin is heated at two different times during its prepara- 

 tion sufficiently to kill the tubercle bacilli and it is also filtered through a 

 substance that would remove the tubercle bacilli, if any escaped the first 

 filtration. When ready for use tuberculin is a clear, amber colored liquid. 

 The intensity of its color varies according to the amount of blood pigment 

 in the meat from which the bouillon was made. 



Tuberculin cannot possibly produce tuberculosis, because it does not 

 contain any tubercle bacteria. There is no evidence that in cattle it excites 

 a latent tubercle into activity, or that it tends to make the disease icorse. It 

 is used the u'orld over and as yet no authentic report of injury caused by 

 its use has been recorded. It has been used in the treatment of tuber- 

 culosis in man and there are several physicians who have reported favor- 



