318 DR. LEGEAR'S STOCK BOOK. 



In the West and Southwest of our country, where cattle are 

 reared mostly in the open air, the disease is apparently quite rniv. 

 as most of the animals are able in a measure to resist the con- 

 tagion, and only occasional animals in a herd show any physical 

 signs of the disease. 



Symptoms. In the first stages of the disease it is very diffi- 

 cult to detect. It is a disease slow in its course, and at first un- 

 noticed; many cases never show any symptoms, and are found 

 only to be tuberculosis when killed. In those animals showing 

 symptoms there is generally a dry, hoarse cough, at first slight., 

 occurring after feeding or drinking; it may be easily excited by 

 running the animal. As the disease progresses, the animal grows 

 thin and has an unthrifty appearance of the coat, etc.; this per- 

 sists in spite of good feed. The cough now becomes more fre- 

 quent and the breathing more rapid, especially on slight exer- 

 tion; the breath becomes offensive, and usually there is a dis- 

 charge from the nose. Weakness continually increases, followed 

 by disorder of digestion bloatinp 1 and diarrhoea and the ani- 

 mal finally dies from exhaustion. Often all symptoms are want- 

 ing in spite of the existence of the disease, and in such cases the 

 tuberculin test must be used. 



Tuberculin Test. Tuberculin is a glycerine extract of the 

 culture of the bacillus tuberculosis (germ of the disease), and 

 when injected under the skin it has the property of causing a 

 rise in temperature in all animals suffering from this disease. 

 It is also known as Koch's lymph. In animals free from the 

 disease no reaction takes place after the use of the tuberculin. It 

 is therefore a valuable agent for detecting all tuberculous cattle 

 in an infected herd, and is the only means by which this can be 

 accomplished. 



In 1890 Koch, under pressure, made public his work on tu- 

 berculin. This resulted in a tremendous and intense excite- 



