40 JOHNE'S DISEASE 



it is not sufficiently reliable to be used with reasonable 

 safety, as the large dose which has to be given (8 to 

 10 c.c. in adult bovines) is likely to give a reaction 

 with other conditions (see discussion under Vaccines, 

 Chapter VII.). 



The present writers have obtained marked rises in 

 the temperatures of naturally affected animals and of 

 inoculated calves, goats, and sheep, by using a diag- 

 nostic vaccine prepared from pure cultures of Johne's 

 bacillus. The cultures w^ere grown on special media 

 and also on ordinary broth after acclimatization of the 

 bacillus. Holth also has obtained a typical reaction, 

 with an autogenous vaccine, in a calf which had been 

 inoculated three months previously with a pure culture 

 of Johne's bacillus, although in this instance an extract 

 ot the tubercle bacillus was also present in the fluid. 

 In the opinion of the writers, a vaccine prepared from 

 cultures of the specific bacillus is the only reliable 

 diagnostic reagent for Johne's disease, and in all 

 doubtful cases tests with such a vaccine should be 

 carried out. For full details the reader must refer to 

 Chapter VII. It only remains to be noted here that 

 very advanced cases — which, however, can be diag- 

 nosed quite easily from the clinical symptoms, etc. — 

 may fail to react, a result which is also frequently 

 obtained when advanced cases of tuberculosis are 

 tested with tuberculin. Our experiments indicate 

 that the autogenous vaccine for Johne's disease is 

 quite as reliable as tuberculin is for tuberculosis. 



