THE PROTECTION OF THE HERD. 275 
This does away with most of the danger to the public consuming the 
milk, but does nothing toward eradicating the disease 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 disease. It 
protects the herd and the public at the same time. 
3. The great losses that are frequently involved in the slaughter 
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 fifteen years ago by Bang, consisting of separating 
the reacting animals from the others v The first step is to detect by 
tuberculin all tuberculous animals. The advanced cases are slaugh- 
tered. 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 themselves, 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 
not be worn in the shed occupied by the healthy animals. He 
must remove all calves from the infected herd a few days after birth 
