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Hastings, E. G.
Tuberculin and its uses,   pp. 97-106 PDF (2.1 MB)

Page 98

Fortieth Annual Report of the
healthy animals was killed and on examination found to be tubercular.
This again has caused a certain distrust of the tuberculin test. Again,
cattle have been removed from herds on account of having reacted to
the tuberculin test, and on slaughter the lesions of the disease have not
been found in their bodies. These things indicate that the tuberculin
test has certain limitations which should be recognized by everyone
who is using the test. If these limitations are recognized, I feel very
certain that all will be better satisfied than when the test is considered
to have no limitations.
Tuberculin is an extract of a specific pathogenic organism, the tuber-
cle bacillus. In tuberculin are contained certain specific products
which when injected into the body of a tubercular animal produce
certain disturbances. One of these disturbances is a thermal one,
the tuberculin causing more or less of a temporary fever, and, since
the temperature of an animal is a thing that can be easily measured,
this thermal reaction is what is used to detect whether the tuberculin
has had a disturbing effect upon the body of the animal or not.
A very curious phenomenon has been noted within the last few
years. It has been found that if an animal, such as a guinea pig, is
injected with a very small amount (one-fifth of a drop) of blood serum
from a different kind of animal, for example, a horse, and about ten
days later the same guinea pig is given a larger dose (about 5cc.)
serious disturbances follow within a few moments. The quantity of
blood serum first injected produced absolutely no harmful effect. It
has, however, sensitized the guinea pig, as it is called, and when the
larger amount of blood serum is injected, which in the case of a
guinea pig that had not received the small sensitizing dose would be
without effect, it produces serious illness, often terminating in death
-within a few moments. It is believed that the reaction of tuberculin
+ is allied to this phenomenon. The animal is sensitized to the products
of the tuberculin bacillus by the growth of the organism within the
body. When these specific products are introduced, they produce
more or less of an effect.  If a series of guinea pigs is injected with
blood serum and after a definite time the animals are again injected
with a larger dose, certain differences will be noted. One animal may
die within a short time, another may show signs of serious illness but
may recover, while another will show that the second dose has had
a much smaller effect upon it. The same thing is true in the case
of the injection of tuberculin into tubercular animals. The extent
of the thermal reaction in tubercular animals may vary from 0° to 6-
or 7° F.
The normal temperature of cattle varies widely, not only between
different animals, but in the same animal, from day to day and hour to

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