568 Tuberculosis. 



during which previously healthy areas become involved by the 

 process. Bacillary emboli give rise to the development of 

 new tuberculous foci in remote organs or an infection with 

 pyogenic organisms complicates the morbid process. The 

 chronic course .of the disease may be accelerated by influences 

 that exert a weakening action on the body like catching cold, 

 railroad transportation, overwork, etc. Intercurrent acute 

 disease and parturition may have the same effect (Froehner 

 observed a chronic case of tuberculosis of the horse become 

 acute after an attack of pleuro-pneumonia and G-uenther the 

 same in a cow after abortion). Exacerbations of this sort are 

 announced by elevation of temperature, symptoms of general 

 indisposition and occasionally more frequent coughing. After 

 a few weeks former conditions again prevail. In the advanced 

 stage of the disease these temporary improvements become 

 less and less frequent. Again, in other cases, especially in 

 young animals and after an intensive injection of virus, the 

 disease may become steadily progressive and lead to complete 

 exhaustion. 



Following the entrance of numerous bacilli into the blood 

 stream the simultaneous development of numerous tubercles 

 or rapid increase of virus in the blood may lead to a fatal ter- 

 mination within a few weeks. Symptoms of acute miliary tuber- 

 culosis, which is an acute febrile disease, attend this condition. 



Tuberculosis of the cerebral meninges also runs an acute 

 course, while solitary tubercles developing in the substance of 

 the brain may remain unobserved for a long time or only cause 

 functional disturbances of the nerves, especially spasms and 

 paralysis, until they finally reach the meninges and there set 

 up acute inflammation. 



In large herds the disease usually spreads very gradually. 

 Since the development of the disease in a single animal may 

 extend over a course of years, large herds may, in spite of 

 infection, be kept up for years or even decades. The prompt 

 removal of affected animals which show physical indications of 

 the disease and their replacement by younger stock may retard 

 a rapid deterioration of the apparently fair general condition 

 of the herd. However, in herds of this sort, especially if they 

 are dairy herds, the disease will continue to spread irresistibly. 

 In the course of time the age limit at which the first clinical 

 symptoms of disease make their appearance is gradually re- 

 duced and accordingly more and younger animals must be 

 ranged out every year. Finally the malady will make its ap- 

 pearance as a clinically observable disease in quite young ani- 

 mals, viz., in the form of tuberculosis of the lymph glands, of 

 the lungs and of the bones. 



Diagnosis. Even if we exclude the early stages of tuber- 

 culosis in which no clinical symptoms whatever are observable 

 it is only rarely possible even in advanced stages of the disease 



