38 STORRS AGRICULTURAL EXPERIMENT STATION. 
that have been going on for several years now have indicated 
that butter in quite a large percentage of the specimens, thirty 
to forty per cent., contains active bacilli fatal to guinea pigs, 
and that market milk in considerable proportion also contains 
them, we must admit that the conclusions thus drawn have 
little or no relation to the problem of human health, and that 
they do not indicate of necessity a danger from the milk at all 
proportional to the seeming results. The general consensus 
of opinion at the present time appears to be that the danger 
from the use of milk, as indicated by inoculation experiments, 
has been certainly very much overdrawn. 
To these facts must be added the evidence given elsewhere 
pointing to the existence of varieties of the tubercle bacillus. 
Ifthe human bacillus is only slightly pathogenic for cattle, it is 
at least likely that the bovine variety may not be very danger- 
ous to man, although this remains to be proved. 
The same facts arise when we come to study the conditions 
of tuberculosis in mankind from a statistical standpoint. It 
must be remembered that the use of dairy products has been 
quite rapidly increasing in the last fifty years. ‘This is particu- 
larly true of England and the United States, and it is true also 
to a certain extent of other countries. We have seen above, 
also, that there are very good reasons for believing that the 
amount of tuberculosis among our cattle is increasing, and in- 
creasing somewhat rapidly. If, now, it were a fact that man- 
kind obtained this disease to any appreciable extent from milk, 
we should expect to find the amount of tuberculosis in mankind 
increasing, and especially in those countries where there is the 
largest increase in the use of dairy products. Furthermore, it 
is a fact that in most European countries milk is not drunk 
raw to any very appreciable extent. Nearly all of continental 
Europe has, in the last few years, acquired the habit of steril- 
izing the milk before using it. In some countries this is almost 
universal. In Switzerland the children are taught the danger 
of drinking milk without sterilizing, and at the present time the 
amount of milk drunk without some kind of preliminary heat- 
ing is comparatively. small in continental countries. On the 
other hand, in England.and in the United States the habit of 
sterilizing milk has not obtained much foothold. While milk 
is sterilized frequently for use among infants and invalids, 
there is no such general custom as in Europe in this direction, 
and in these countries we may say that the great bulk of the 
milk is drunk without sterilization. Now if milk were a con- 
