640 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
the apex of the lungs and exerts no injurious effect upon the organism 
as a whole. We may, therefore, fairly conclude that the human 
organism possesses a strong inherent tendency to overcome infection 
with the tubercle bacillus. So much can be safely predicated. But 
whether the suppression of a local infection, such as I have described, 
gives an increased capacity for overcoming subsequently invading 
tubercle bacilli remains for the present an open question. It is cer- 
tainly not disproved by the facts cited; and some authorities hold fast 
by the belief that a degree of immunity to tuberculosis 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 Behring’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 virulent bovine 
culture of tubercle bacilli is given, no permanently bad results fol- 
low, 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 
