THE TUBERCULIN TEST FOR TUBERCULOSIS IN MILCH COWS. 387 
organs in the animal body, have only been irseful in a small per¬ 
centage of instances. Especially in onr animals is physical 
diagnosis difficult in chronic hidden diseases. Although in more 
piononnced cases anscultation (the stethoscope) and percussion 
(the hammer), the irregularity in blood temperature (thermome¬ 
try) and more rarely the pulse, may tell us that there is lurking 
within a lung a nest of contagion, in by far a greater number, 
no one, if his five senses be ever so acutely developed, can dis¬ 
cover its presence. The disease tuberculosis, the diagnosis of 
which I shall treat briefly of to-day, usually presents itself in a 
latent form. It is a slow, wasting disease, “ a pestilence that 
walketh in darkness,” and as a venerable and esteemed colleague 
rightly says, “ often under an outward guise of health the sub¬ 
ject of the disease carries around germs of death to his unsus¬ 
pecting and more susceptible fellow.” The very propagation of 
tuberculosis seems to depend upon its latency. Acute diseases in 
our cattle, like anthrax or Texas fever, present a bold front, man¬ 
ifest well marked symptoms, their victims soon succumb, hence 
well directed veterinary police measures can readily and com¬ 
paratively easily cope with them and crush them out. To effec¬ 
tually stamp out forever any infectious disease we must seek its 
source. To destroy the source must be to destroy the disease. 
In consumption of our cattle the source of the disease (the 
germ) is always harbored in an infected animal. One may pos¬ 
sess a perfectly healthy herd of cattle, he may introduce into this 
herd an apparently sound cow, which may carry in its lungs a 
few tubercular nodules, the presence of which no expert can un¬ 
earth. This infected animal can, however, transmit the germs 
to those standing next to her in the stable, and from them to 
their neighbors, etc., if they only be kept living together for a 
long enough period of time, until perhaps twenty-five, fifty, one 
hundred per cent., depending upon the sanitary conditions of 
the stable, the food and care the animals receive, become vic¬ 
tims of the disease. 
When consumption was thought to be due to bad sanitary 
arrangements alone, dirt, dust improper food, etc., efforts were 
