470 IOWA DEPARTMENT OF AGRICULTURE 
of the slight effect of an ordinary-sized dose of tuberculin on an advanced 
case of the disease with so much natural tuberculin already in the sys- 
tem, or on account of a recent previous test with tuberculin which pro- 
duces a tolerance to this material lasting for about six weeks. The 
second class includes those that are not tuberculous, but which show an 
elevation of temperature as a result of (a) advanced pregnancy, (b) the 
excitement of oestrum, (c) concurrent diseases, as inflammation of the 
lungs, intestines, uterus, udder, or other parts, abortion, retention of 
afterbirth, indigestion, etc., (d) inclosure in a hot stuffy stable, espe- 
cially in summer, or exposure to cold drafts or rains, (e) any change in 
the method of feeding, watering or stabling of the animal during the 
test. Notwithstanding all these possibilities of error, the results of 
thousands of tests show that in less than 3 per cent of the cases tested 
do these failures actually occur. In the first class the chances of error 
are decidedly reduced by the skilled veterinarian by making careful phy- 
sical examination and diagnosing clinically these advanced cases, and by 
the injection of double or triple doses into all recently tested cattle, with 
the taking of the after temperatures, beginning two hours following the 
injection and continuing hourly for twenty hours. 
It is therefore apparent that tuberculin should only be applied by or 
under the direction of a competent veterinarian, capable not only of in- 
jecting the tuberculin but also of interpreting the results, and particularly 
of picking out all clinical cases by physical examination. The latter ob- 
servation is extremely important and should always be made on every 
animal tested. 
In the second class errors are avoided by eliminating those cases from 
tne test that are nearing parturition or are in heat or show evidence 
of the previously mentioned diseases or exhibit temperatures sufficiently 
.high to make them unreliable for use as normal. Then, in reading after 
temperatures it is advisable not to recognize as a reaction an elevation 
of temperature less than 2° F. and which at the same time must go 
above 103.8° F., and the temperature reaction must likewise have the 
characteristic rainbow curve. (Those cases which approximate but do 
not reach this standard should be considered as suspicious and held for 
a retest six weeks later). In addition, a satisfactory tuberculin must 
be used, also an accurate thermometer and a reliable syringe, in order 
that a sufficient dose of tuberculin may be given. Finally, the number 
of apparent errors of the tuberculin test will be greatly diminished if a 
careful post-mortem examination is made, giving especial attention to 
the lymph glands. This low percentage of failures being the oase. cattle 
owners should welcome the tuberculin test, not only for their own interest 
but for the welfare of the of the public as well. There this method 
of diagnosing the disease has been adopted tuberculosis is gradually 
being eradicated, while it is spreading rapidly and becoming widely dis- 
seminated in those districts where the tuberculin test has not been em- 
ployed. Without its use the disease can not be controlled and the cattle" 
owner is confronted with serious and continuous losses; with its use the 
disease can be eradicated from the herd, a clean herd established in a 
few years without very "serious loss or hardship, and the danger of its 
