_--A disease so varied in its attack upon the different organs
of the body and in the extent of the disease process must necessarily lead
to mistakes when diagnosis is attempted by ordinary means of examination.
It has been confounded with the later stages of pleuropneumonia, with
parasitic diseases of the brain, the lungs, the intestines, and with
actinomycosis. A careful examination of the lungs by auscultation and
percussion enables the expert to locate large tuberculous masses, owing to
dullness, loss of respiratory murmur, and abnormal sounds, such as blowing,
whistling, and creaking. The majority of cases of tuberculosis in cattle,
however, including many in which the lungs are quite seriously involved,
can not be detected in this manner.

THE TUBERCULIN TEST.

The tuberculin test, which is marvelously accurate in its indications, has
been almost universally adopted for the detection of tuberculosis.
Tuberculin is a drug prepared by sterilizing, filtering, and concentrating
the liquids in which the tubercle bacillus has been allowed to vegetate. It
contains the cooked products of the growth of these bacilli, but no living
bacilli; consequently, when this substance is injected under the skin of an
animal it is absolutely unable to produce the disease, cause abortion, or
otherwise injure the animal. In case the injected animal is normal there is
no more effect upon the system than would be expected from the injection of
sterile water; however, if the animal is tuberculous, a decided rise of
temperature will follow the use of tuberculin by the subcutaneous method.
This substance, discovered by Koch, has the effect, when injected into the
tissues of a tuberculous animal, of causing a decided rise of temperature
or other manifestations while it has no such effect upon animals free from
the disease. The value of tuberculin for this purpose was tested during the
years 1890 and 1891 by Guttman, Roeckl and Schuetz, Bang and Salomonsen,
Lydtin, Joehne and Siedamgrotzky, Nocard, and many others. It was at once
recognized as a most remarkable and accurate method of detecting
tuberculosis even in the early stages and when the disease had yet made but
little progress. It is now quite generally employed.

The tuberculin test came into existence through the most careful and
thorough scientific experimentation.

As a result of its use an accurate diagnosis may be established in more
than 90 per cent of the cases tested. The re