152 



COMMON DISEASES. 



are in a debilitated condition. The great majority of these cases 

 show no symptoms but on the contrary appear to be in the finest 

 physical condition. There are a great many mild or latent cases, 

 having but a small amount of tissue diseased, and the animals may 

 live for many years. They may possibly die at old age, but on 

 the other hand they may succumb to a sudden development of 

 the disease following any condition which produces debility. 



FIG. 58. BOVINE TUBERCULOSIS. (M. H. R.) 



A famous show steer, in prime "condition." Liable to be as badly dis- 

 eased as the pi ecediner. 



When the lungs are involved, there may be a persistent cough, 

 shortness of breath, pallor of visible mucous membranes, loss of 

 flesh and unusual sounds in the lungs. 



When intestines and mesenteric glands are affected, there 

 may be chronic diarrhoea with slow and persistent loss of condi- 

 tion. All these diagnostic symptoms may vary greatly and are 

 often unreliable; e. g., a cow may be in good flesh, hair and eyes 

 bright, and yet ready to die in a short time. 



Diagnosis. — The only reliable test is tuberculin, or Koch's 

 lymph, which seems to be very accurate. An average of tests 

 and post-mortems of reported cases shows an accuracy of over go 

 per cent. Tuberculin is used by injecting a definite quantity un- 



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