PREVENTION, SYMPTOMS AND TREATMENT 255 



may lead to dyspnea, dysphagia, or roaring. Enlargement of the 

 mediastinal lymph nodes causes pressure on the anterior vena cava 

 and venous pulse in the jugulars, on the trachea with dyspnea, and 

 on the gullet, leading to dysphagia and to loss of rumination and 

 tympanites after eating because eructation is prevented. 



In intestinal tuberculosis, chronic tympanites and constipation 

 alternating with diarrhea occur, the latter becoming chronic with 

 emaciation. Tuberculosis of the brain gives symptoms of menin- 

 gitis, and signs in lungs, enlarged lymph nodes and emaciation are 

 often also present. In the udder, tuberculous involvement is gen- 

 erally in one quarter in the form of a very hard, diffuse, painless 

 swelling, and, after a month or so, the milk becomes thin and con- 

 tains flakes and perhaps bacilli. Tuberculosis not rarely affects the 

 vertebral column, bones of head and joints. As aids to diagnosis we 

 have examination of the nasal discharge, milk, pus and tissue from 

 suspected animals for bacilli, and the tuberculin test. Also inocu- 

 lation of milk or minute quantities of suspected infected material 

 into, the abdominal cavities of guinea-pigs, when miliary tubercles 

 may be produced in two weeks or more. 



The necessity of the tuberculin test in order to make a positive 

 diagnosis of tuberculosis in cattle is shown by the experiments of 

 Schroeder (Circular 118, Bureau of Animal Industry), who found 

 that among cows which seemed absolutely healthy, as far as appear- 

 ance and physical examination were concerned, forty per cent, were 

 tuberculous, as shown by the tuberculin test. 



The Tuberculin Test. — It is best to take the temperature of 

 cattle from 6 A. M. every two hours until tuberculin is injected on 

 the evening of the same day between 8 and 10 P. M. The test is 

 unreliable in animals whose temperature reaches 103.2 F. (except 

 young bovines, in which a temperature of 103.2 F. is not abnormal) 

 during this period prior to the injection. Animals should be kept 

 at rest for twelve hours before tuberculin testing. The test is mis- 

 leading within a few days of calving — either before or after. The 



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