94 VACCINE AND SEEUM THERAPY 



observed at the same time. As these latter measures 

 are in themselves effective, the beneficial results 

 obtained could not solely be attributed to the immuni- 

 sation. 



Double Immunisation with Human Tubercle Bacilli 

 {Behriuf/s Method). — The immunising material con- 

 sists of nearly free virulent human tubercle bacilli, 

 dried in a vacuum, and injected into the blood circula- 

 tion of calves. 



The first tests conducted after these treatments 

 showed that two intravenous injections of bovo- 

 vaccine, or of any fresh culture of the human type 

 of tubercle bacillus, into cattle resulted in a con- 

 siderable and immediate increase in their power of 

 resistance to artificial infection. Further experiments, 

 however, showed that resistance thus artificially in- 

 creased was of short duration, suffering considerable 

 reduction at the end of one year, and disappearing 

 altogether at the end of one and a half years. The 

 results of the practical application, on the other 

 hand, of this method showed that it had no noticeable 

 effect on the improvement of the health of infected 

 herds. A serious objection to this plan, apart from 

 the trouble and expense of yearly vaccination, lies in 

 the fact that the bacilli introduced by the act of 

 vaccination remain alive and active in the bodies of 

 the animals for a long time, thus making the 

 slaughter of such animals for food a procedure of 

 doubtful propriety. 



Koch introduced a method similar to the above. 



