320 
D. F. LUCKEY. 
under the surface of the skin, only deep enough so that when the 
tuberculin is injected it will not ooze out through the surface. 
Three or four drops of tuberculin is sufficient to give a reaction. 
It is impossible to gauge this small amount on the plunger of 
any ordinary syringe. For all practical purposes, it is sufficient 
to watch the point of injection and press upon the spring-handle 
until a little elevation, something like the size of a navy bean 
or a little larger is produced. By counting up the amount of 
tuberculin used, we find that about three drops will produce a 
little elevation of this size. A re-examination of a herd oi 
cattle that are free from tuberculosis on the third day after in¬ 
jection shows absolutely nothing. It is extremely difficult, and 
in many cases impossible to find where the injection was made. 
In a tuberculous animal a swelling appears, which varies quite a 
good deal in size but is sufficiently large, as a rule, that it may 
be seen for quite a distance. The swelling is hard, painful and 
sometimes extends around to the upper surface of the tail, and 
remains from five to ten davs. 
In all forms of tuberculin tests an animal now and then will 
fail to show a clear-cut reaction, either negative or positive. I 
have not been able to figure up the number of “suspicious ” re¬ 
actions from the use of the intradermal test, but as far as we 
have gone, the indications are that the suspicious reactions will 
be much smaller than with the use of the temperature test. 
I might say in conclusion that while the tuberculin test seems 
to be a very simple matter and that farmers and students are 
inclined to undertake it, it really requires extreme skill, judg¬ 
ment and care, if accurate results are to be expected. Neither 
veterinarian nor layman can jump in and make tuberculin tests 
and do the most accurate work at the beginning. We credit 
our record for accuracy to the fact that our men are well quali¬ 
fied veterinarians, are at this work continually, and receive post 
mortem notes on all cattle slaughtered, while the animals are 
still fresh in their minds. Only after working at this testing for 
six months or a year is a veterinarian able to get the most ac¬ 
curate results. Where a veterinarian is testing all the cattle in 
