706 



INFECTIOUS DISEASES. 



of determining the presence of the organism which causes the dis- 

 turbance. In all cases, in fact, the tubercle bacillus should be sought 

 for in order to confirm the diagnosis. 



If this method cannot be employed, as for example in tubercu- 

 losis of the liver, brain, etc., and the diagnosis is uncertain, the use 



of tuberculin constitutes 

 the surest and easiest 

 method of coming to a 

 conclusion. Nocard's re- 

 searches have shown the 

 precautions to be ob- 

 served. A minimum feb- 

 rile re-action of 2^ Fahr. 

 (1*5° C.) is, however, 

 necessary before the 

 existence of the disease 

 can be affirmed. 



Lastly, there remains 

 a less rapid method, 

 which aims at trans- 

 mitting the disease to 

 specially susceptible 

 animals by inoculating 

 with suspected materials, 

 such as the nasal dis- 

 charge, pus, milk or 

 pulp of internal organs. 

 This method is most 

 valuable when bacterio- 

 logical examination has 

 failed and tuberculin has 

 produced only doubtful 

 results. The guinea-pig 

 is the subject usually 

 chosen, but some weeks, 

 or even months, may elapse before definite results are obtained. 



In those forms where ordinary methods of investigation prove 

 sufficient it is well to bear in mind the symptoms which differentiate 

 this disease from others closely resembling it. 



Pulmonary tuberculosis, for example, should always be suspected 

 whenever there exists frequent coughing, nasal discharge and poor 

 bodily condition ; if in addition to this respiration is found on auscul- 

 tation to be rough, inspiration interrupted or rasping, expiration 



Fig. 283. — Tuberculosis of the posterior mediastinal 

 lymphatic glands in a sheep which had been 

 kept for two years in company with some tuber- 

 culous cows. PG, Left lung; PD, right lung; 

 T, trachea ; La, anterior lobes ; L, middle cardiac 

 lobes ; L^, posterior lobes ; Gm, tuberculous and 

 enlarged posterior mediastinal lymphatic glands. 



