SOCIETY MEETINGS. 
485 
VARIATIONS OF THE TUBERCLE BACILLUS. 
The discover}^ by Dubard of tuberculosis in fish has served to broaden 
our views concerning this most interesting and destructive panzootic 
disease. From a study of the bacillus of mammalian tuberculosis we 
learned that this microbe requires for its multiplication a temperature 
between 86 and 104° F., and we concluded from this fact that this germ 
is an obligatory parasite, unable to multiply outside of the animal body 
except under special conditions furnished in the laboratory. Later, it 
was discovered that in the tuberculosis of birds, or avian tuberculosis, 
the bacillus had undergone a remarkable physiological modification and 
that it is able to grow all the way from 77 to 113° F. That is, instead 
of being confined to a temperature range of 18° F., as is the case with 
the mammalian bacillus, it has in the avian variety acquired the power 
to multiply through a temperature range of 36° F. The doubling of 
the temperature range and the ability to multiply at a point nine de¬ 
grees lower on the scale has an important signification ; for, whereas a 
continued temperature of 86° F. is difficult to realize in nature, 77° F. 
for days and nights in succession is not infrequent in many parts of the 
country. Already the question was suggested as to whether it is not 
possible for the bacillus tuberculosis to live and multiply in nature as 
a saprophyte. 
Dubard’s discovery of tuberculous carp, the bacillus from which is 
able to grow from 50 to 96.6° F., is still more astonishing, and opens a 
field of possibilities so extensive that it is safer to wait for the positive re¬ 
sults of investigations than to speculate as to what may or may not be 
true. The facts already established are, however, most important. A 
bacillus which can vegetate at 50° F. can live as a saprophyte without 
difficulty, if it finds a proper food supply. 
The first question that suggests itself is as to the identity of these 
bacilli, which are so frequent in their physiological requirements. Are 
the mammalian bacilli, the avian bacilli and the piscine bacilli but vari¬ 
eties of the same species, convertable from one another, or are the}^ 
specifically distinct ? The researches which have already been made 
appear to warrant the conclusion that the avian and piscine bacilli may 
be given all the characteristics of the mammalian form by growing 
them for a sufficient time under proper conditions. Indeed, Dubard is 
of the opinion that the carp were infected by throwing into the stream in 
which they lived the excreta and sputa of a human patient affected with 
pulmonary and intestinal tuberculosis. 
Wide, therefore, as is the gulf which separates the cold-blooded carp 
from the mammalia, or the latter from the hyperthermic birds ; remark¬ 
able as are the morphological and physiological differences shown by 
the bacilli from these different sources, we are forced to the conclusion 
that these differences are superficial, that they vary with the conditions 
of environment, and that the tuberculosis of the fish, the mammal, and 
the bird is one and the same disease. Accepting this conclusion that the 
mammalian bacillus may under certain conditions infect fish and be so 
modified that it has the vigor to grow at a temperature of 36° F. lower 
than before ; and that, on the other hand, it may infect birds and be so 
modified as to grow at a temperature 9° F. higher than before, should 
we not be conservative in adopting the views recently promulgated to 
the effect that the bovine and human bacilli are different varieties and 
