478 
koch’s tuberculosis conclusions. 
that the supposed fact by which those precautions are warranted 
is no fact at all, for that is what Koch’s contention will gener¬ 
ally be interpreted as amounting to. 
Professor Koch seems to have convinced himself that cattle 
are nearly, if not quite, insusceptible to infection with the 
micro-organism that occasions tuberculous disease in human 
beings. His experiments, not many in number, but extending 
over a considerable period of time and persistently and sys¬ 
tematically carried on, it must be admitted, have failed to con¬ 
vey the human disease to cattle, whether they consisted in 
feeding them with tuberculous sputum, in implanting it in a 
serous cavity, or in injecting it beneath the skin, whereas the 
same forms of inoculation with tuberculous material of bovine 
origin promptly resulted in infecting the animals with tuber¬ 
culous disease. Great weight should undoubtedly be accorded 
to these experiments and to any opinion expressed by so acute 
an observer as Professor Koch, but in our opinion they cannot 
be held to be decisive by themselves alone. Opposed as .they 
are to almost universal conviction, they cannot be accepted off¬ 
hand as final. Further experiments, varied perhaps in some 
ways that have not occurred to Professor Koch and that possi¬ 
bly will not at once suggest themselves to the minds of others, 
will have to be made before the question of the transmissibility 
of human tuberculous disease to cattle can be regarded as quite 
settled. Perhaps there are few qualified observers who would 
at the present time declare without reserve that “ tuberculosis 
of man and cattle is identical,” as the United States Veterinary 
Medical Association did by resolution in 1896, but at least they 
are so nearly identical that each is capable of yielding a product 
known as tuberculin, and surely that is a dangerous approach 
to identity. 
Furthermore—and this is a far more momentous matter for 
the human race—Koch argues against the transmissibility of 
bovine tuberculous disease to man. Deliberate experiments to 
decide this point are of course out of the question, but Koch 
thinks that the world is unconsciously performing experiments 
that suffice to sustain his view ; that is to say, that beef, milk, 
and butter contaminated with living tubercle bacilli are con¬ 
stantly being ingested by many human beings, and yet primary 
tuberculous disease of the digestive tract is rare. To argue 
from such observations that the disease is not transmissible 
from cattle to man seems to us rather inconclusive. Theo¬ 
retically, it may be granted, a tuberculous process at the initial 
