408 DISEASES OE CATTLE. 



causes sinking of the eyes in their sockets. They appear swimming in water, and 

 their expression is weak. The cough is more frequent, but never or very rarely 

 accompanied with discharge. The body continues to emaciate even with plenty 

 of food and a good appetite, so that the quantity of milk is small. At times in 

 the early stages of the disease, still more in the later stages, the diseased animals 

 manifest considerable tenderness when pressure is applied to the front or tho 

 sides of the chest, by coughing, moaning, etc. Often symptoms are wanting in 

 spite of the existence of the disease. 



Lydtin also quotes at length a description of the abnormal sexual 

 desire occasionally observed among cows when affected with this 

 disease. 



Diagnosis. — A disease so varied in its attack upon the different 

 organs of the body and in the extent of the disease process must nee- . 

 essarily lead to mistakes when diagnosis is attempted by ordinary 

 means of examination. It has been confounded -with the later stages 

 of pleuro-pneumonia, with parasitic diseases of the brain, the lungs, 

 the intestines, and with actinomycosis. A careful examination of the 

 lungs by ausculation and percussion enables the expert to locate large 

 tubercular masses, owing to dullness, loss of respiratory murmur, and 

 abnormal sounds, such as blowing, whistling, and creaking. How- 

 ever, the majority of cases of tuberculosis in cattle, including many 

 in which the lungs are quite seriously involved, can not be detected 

 in this manner. 



THE TUBERCULIN TEST. 



The tuberculin test, which is marvelously accurate in its indica- 

 tions, has been almost universally adopted for the detection of 

 tuberculosis. Tuberculin is a drug prepared by sterilizing, filtering, 

 and concentrating the liquids in which the tubercle bacillus has been 

 allowed to vegetate. It contains the cooked products of the growth 

 of these bacilli, but not the bacilli themselves. Consequently, when 

 this substance is injected under the skin of an animal it is absolutely 

 unable to produce the disease, cause abortion, or otherwise injure the 

 animal. In case the injected animal is normal there is no more effect 

 upon the system than would be expected from the injection of sterile 

 water. However, if the animal is tuberculous, a decided rise of tem- 

 perature will follow the use of tuberculin. This substance, discov- 

 ered by Koch, has the effect, when injected into the tissues of a 

 tuberculous animal, of causing a decided rise of temperature, while it 

 has no such effect upon animals free from the disease. The value of 

 tuberculin for this purpose was tested during the years 1890 and 1891 

 by Guttman, Roeckl and Schiitz, Bang and Salomonsen, Lydtin, 

 JOhne and Siedamgrotzky, Nocard, and many others. It was at once 

 recognized as a most remarkable and accurate method of detecting 

 tuberculosis even in the early stages and when the disease had yet 

 made but little progress. 



