294 IOWA DEPARTMENT OF AGRICULTUER 
Quite recently a case came under our observation. A dairy cow sup- 
pling milk to her owner's family. The cow was a grade Ayrshire, a pro- 
lific milker, slightly thin in order, but not noticeably so for a deep milker, 
otherwise in apparent health. We were asked to test two cows on the 
place, this being one of them, as the owner was contemplating making 
additions to his herd. There was nothing unusual about her temperatures 
before the injection of tuberculin, but the next forenoon after the injection 
her fever rose typically, showing a decided reaction. The owner was ad- 
vised to have her removed from the place and slaughtered at once, to 
which he consented and brought her to the packing house. The post- 
mortem revealed a case of extraordinarily extensive tuberculosis, con- 
fined almost entirely to the right lung and the right thoracic cavity. The 
lung and the walls of the chest on that side were almost completely cov- 
ered over by tuberculous growths, and that lung itself was nearly a solid 
mass of hard tubercles. The other lung and the balance of the organs, 
tissues and glands were very little, if any, diseased, accounting for her 
healthful appearance. 
I cite this case to show you how deceitful these animals may be. Here 
was a cow harboring this disease in one corner of her body, pouring 
out poison from every pore, scattering and disseminating the tuberculous 
germs with every step, with almost every breath, and her every exhala- 
tion and excretion of every kind and character, a positive menace to her 
companions, both human and bovine — going along day after day entirely 
unsuspected. 
But on the other hand many cattle and hogs as they grow older if 
they are already victims of this loathsome disease begin to show symptoms, 
as one after another the organs that are of vital necessity to the life of 
the animal become involved. The animal coughs, becomes emaciated, 
the hair loses its lustre, the appetite may fail, the eye becomes dull, 
exercise fatigues and causes accelerated respiration, etc. There are no 
tissues or organs in the animal economy exempt from the inroads of 
this disease, and hence every case is peculiar to itself, you might say. 
Gentlemen, it is astonishing how many of our hogs and cattle, too, 
are showing bone lesions now, such as a caseous condition of the ver- 
tebrae or back bone. Many of our cripples, among both hogs and cattle, 
are thus affected. Many hogs that drag their posterior extremities and 
are supposed to be suffering from rickets are the victims of tuberculosis 
of the vertebrae. 
But we have dwelt long enough on this phase of the disease. We have 
endeavored to show you that physical signs are absent, that clinical symp- 
toms are rare, that it is next to impossible to make a positive diagnosis 
of the disease by a physical examination. 
And this brings us to speak of our present manner of diagnosis in the 
living subject, aside from bacterial or laboratory examination. I refer, 
of course, to the tuberculin test — tuberculin, an agent that is much talked 
of in these latter days and often much maligned and slandered — even 
among intelligent dairymen and in reputable agricultural papers and live 
stock journals, notwithstanding these discouraging facts, tuberculin, after 
being in use now for many years, is as truthful and reliable as ever. 
