270 TUBERCULOSIS. 
to keep animals warm, they have been too closely shut up in badly 
ventilated rooms, and they breathe the warm air over and over again. 
Such a condition, wholly independent of the tubercle bacilli which 
might be present, has a debilitating effect upon cattle, just as it 
does on men. Too frequently, even on the better farms, the cattle 
are shut up in the stalls early in the fall, are not allowed to go out 
during the long months of the winter, and never get a breath of 
fresh air. Sometimes the case is even worse than this, for many cows 
are thus shut up as soon as they begin to produce milk, and, winter 
and summer alike, remain in close, poorly ventilated rooms. To 
protect his cattle from cold the farmer makes his cow barn too warm 
and allows it too little air. To save trouble he keeps the cows housed 
all the time, with no out-of-door air; and to save expense he crowds 
them together in the smallest amount of space. These facts 
show why so many animals yield to tuberculosis in the colder coun- 
tries. Warm rooms and a close crowding of the animals may 
result in a saving of food, but it invites the spread of tuberculosis 
if it once gains access to a single animal. In the human race it is 
well known that the best protection against the disease, and the 
best remedy for it after it has once started, is out-of-door life. 
Doubtless the same is true of cattle, but this fact has been almost 
forgotten in the attempt to produce the most milk possible at the 
smallest expense. The farmer may perhaps insist that such crowded 
conditions are necessary and unavoidable in the modern farm, but 
he must also remember that, whether necessary or not, they are 
certainly inviting tuberculosis and bringing his animals into a 
condition where they are sure to yield to the infection the first time 
that chance brings the bacillus in their vicinity. More outdoor 
life and more air are the prerequisites for a healthy herd. 
Anything which will induce a vigorous life will decrease the 
.tendency to the disease. Proper food is an important factor in 
determining health. It may be difficult under the conditions of 
modern farming to allow the cattle to have proper exercise in the 
winter, but the lack of it is certainly one of .the factors tending to 
increase the liability to tuberculosis. Too great attention paid 
to the increase in the yield of milk lessens the resisting power of 
