THE PROTECTION OF THE HERD 207 
consuming the milk, but does nothing toward eradicating the dis- 
ease from the herd. 
2. All animals that have the disease as shown by clinical or 
tuberculin test may be slaughtered. The attempt to enforce by 
law such a treatment of the disease has failed wherever tried. It 
involves too great a loss and dooms to slaughter many animals in 
the incipient stages of the disease that might recover and are still 
useful animals. It is sometimes done voluntarily by private 
owners in their determination to keep a herd free from the dis- 
ease. It protects the herd and the public at the same time. 
3. The great losses that are frequently involved in the slaugh- 
ter of all reacting animals have led to the adoption of other plans 
for freeing the herd of the disease without such sacrifices. A plan 
was devised some twenty-five years ago by Bang, consisting of 
separating the reacting animals from the others. The first step is 
to detect by tuberculin all tuberculous animals. The advanced 
cases are slaughtered. The other reacting animals are separated 
from the others and placed by themselves, removed from every 
possible contact with the rest of the animals in the herd. This is 
not because all reacting animals are necessarily sources of danger, 
but simply because there is no means of determining when any 
one of them may become a source of danger to the animals about 
it. The healthy (non-reacting) animals are then placed by them- 
selves, either in a new barn or the old one after it is thoroughly 
disinfected. By this means a practical isolation is accomplished. 
If the farmer wishes to preserve the healthy herd from future 
attack, he must take precautions to have the isolation thorough. 
It may be effected by simply building a partition in his cattle shed; 
but in this case there should be no door in the partition, for that 
would surely result in a carrying of bacilli from one compartment 
to the other. The farmer should remember the facts already 
pointed out as to the methods of distributing bacilli. If possible, 
he should have separate attendants for the two herds, and at all 
events, the boots worn in attendance on the infected herd should 
