242 POPULAR SCIENCE MONTHLY 



question. It is certainly not disproved by the facts cited; and some 

 authorities hold fast by the belief that a degree of immunity to tuber- 

 culosis may be acquired by man. 



In the year 1901, on December 12, on the occasion of his accept- 

 ance of one of the Nobel prizes, Behring announced that he was 

 engaged upon the study of artificial immunization of cattle to tuber- 

 culosis. In this address the claim was made that a method had been 

 perfected whereby it was possible to vaccinate cattle successfully against 

 tuberculosis. These experiments consisted in the endeavor to immunize 

 cattle by means of tuberculin, other toxins, so-called, from the tubercle 

 bacillus, dead tubercle bacilli, bacilli weakened with chemicals and 

 living, active cultures of the tubercle bacillus. In the four years 

 which have elapsed since this announcement was made a series of 

 monographic papers bearing on this subject has appeared from Bear- 

 ing's laboratory in Marburg. The plan of immunization has, in this 

 time, undergone a number of modifications until now it consists in the 

 inoculation intravenously of young cattle — calves twelve weeks old 

 preferably — with a standard human culture, which is now furnished 

 commercially. A second inoculation of an increased quantity of this 

 culture is injected three months later. Cattle treated in this way are 

 regarded as highly immune and are denominated by Behring as 

 ' Jennerized.' If to them a dose of a virulent bovine culture of tubercle 

 bacilli is given, no permanently bad results follow, although an equal 

 dose of the virulent culture will cause, in an unvaccinated animal, the 

 development of generalized tuberculosis leading, in a few weeks, to 

 death. 



In his endeavor to find a culture of the tubercle bacillus which 

 would fulfill the requirement of producing a transient illness and 

 leave protection behind, Behring discovered that not all tubercle bacilli 

 of human origin were without danger to cattle inoculated with them. 

 We were, indeed, not unprepared for this announcement, since, in the 

 first place, we had learned that in some instances tubercle bacilli of the 

 bovine type have been cultivated from examples of human tuberculosis, 

 and, on the other, that not all the bacilli, of any type, exhibit equal 

 degrees of virulence. The culture employed by Behring, although it 

 has now been employed to inoculate several thousand cattle, is said never 

 to have produced severe disturbances of health; even when animals 

 already tuberculous are inoculated the results are not serious: fever 

 lasting several days sets in, the animals may cough, and they may eat 

 less and lose somewhat in weight, but even they return to what is for 

 them the normal. 



It would appear that McFadyean is entitled to the credit of the 

 discovery equally with Behring of the immunization of cattle from 

 tuberculosis; and, indeed, there is reason to believe that his results 



