TUBERCULOSIS 171 
ceased to react to the subcutaneous injection, because of too many 
tests. 
The tuberculin to be used for the eye test should not contain sub- 
stances that will irritate the conjunctiva. Foth recommends a 5% 
solution of dry tuberculin. A 50% solution of the concentrated 
tuberculin of Koch has been used, also the tuberculin of the Bureau 
of Animal Industry. 
Intradermal test. Moussu and Mantoux reported the intradermal 
use of tuberculin as a means of diagnosing tuberculosis in cattle. The 
method consists in injecting the tuberculin into the deeper layers of 
the skin. The most suitable place to make this injection is in one 
of the folds of the skin on the under side of the base of the tail. The 
skin on the eyelid has been used. The skin at the base of the tail is 
soft and pliable and also free from hair. A hypodermic syringe with 
a short needle point should be used. Haring recommends a syringe 
with a 25 or 26 gauge needle with a point from 3 to 5 mm. in length. 
Dentists employ such needles for injecting local anesthetics. The 
method of injecting tuberculin is described by Haring as follows: 
“The subcaudal fold is grasped between the thumb and the first two 
fingers of the left hand and the needle inserted horizontally into the 
thickness of the skin grasped between the thumband finger. The 0.1 
to 0.2 cc. dose, if properly placed, can be felt in the layers of the skin 
as it is expelled from the syringe, where it remains as a small lump in 
the skin after the needle has been removed. In our first test we 
made the mistake of trying to inject as near the surface of the 
skin as possible. It is difficult to inject into the layers of the epidermis 
and an injection into this part of the skin is of little diagnostic value. 
In case the needle is of the proper length, namely, one-quarter of an 
inch, there is little danger of going completely through the skin. 
When the proper point in the subcaudal fold is selected, it makes little 
difference whether the point of the needle is in the derma or in the 
subdermal connective tissue. With the proper syringe an expert 
operator can inject in the dark as accurately as in a good light. We 
have found that characteristic reactions occur with the injections 
from a long needle, placed completely through and beneath the skin 
layers of the subcaudal fold. It is well to inject at a point on the 
fold about two and one-half or three inches down the tail from the 
anus, since elsewhere reactions are not so easily perceived and at this 
point the bone and solid tissue of the tail form a background which 
renders the local reactions more prominent than those of the skin of 
the neck.” 
