s of another disease
(actinomycosis, hydatid disease, verminous bronchitis, distomatosis), it
may be affirmed that there exists, in addition to these conspicuous
changes, a tuberculous center which alone has provoked the reaction.

_The failure to react does not necessarily imply absence of
tuberculosis._ Such failures of tuberculin are very exceptional. They are
seen most frequently with animals affected with tuberculosis in a very
advanced stage and made evident by plain external signs. Sometimes, also,
there are found at the post-mortem examination of animals which have not
reacted small fibrous or calcified lesions in such a condition that one
is tempted to believe them cured. Whether sterile or not, these lesions
have no tendency to increase, and they are not very dangerous from the
point of view of contagion.

These opinions of two eminent authorities, living in different countries,
after long experience of their own and after studying the results of the
many tests made in different parts of the world, should have great weight.
They are essentially the same throughout.

In 1897 Voges compiled statistics of tuberculin tests, the accuracy of
which had been determined by post-mortem examination. Of 7,327 animals
tested, it appeared that errors had been made with 204, or 2.78 per cent.
In the work of the Pennsylvania Live Stock Sanitary Board post-mortem
examinations were made on about 4,400 reacting cattle and the disease was
found in all but 8 of those which had given characteristic reactions.

The results of a much larger number of tests might be compiled at this
time, but they would not materially change the average of those already
mentioned. It is plain that tuberculin is a remarkably accurate test of
tuberculosis, that the animals which react may be safely considered as
tuberculous, and that when a careful clinical examination is practiced in
addition to the test there are few animals in a dangerous condition which
escape detection.

The first questions asked by those who oppose the adoption of the
tuberculin tests are: Is this test infallible? and, if it is not
infallible, why should it be forced upon the cattle owners of the country?

In answer to these questions it may be said that tuberculin is not
absolutely infallible, and yet it is by far the best method of diagnosing
tuberculosis that has been discovered. It is much better than any test
known for pleuropneumonia when that di