BOVINE TUBERCULOSIS. 
645 
ORIGIN OF THE DISEASE IN IOWA. 
It is quite impossible to trace accurately the appearance 
of the disease in our State. We have known of its existence 
among our cattle for twenty-five years, and undoubtedly it 
traces back to a very early period in the history of our cattle 
industry. We first became acquainted with it in herds of 
well-bred cattle; especially those that were represented by 
imported individuals. Comparatively little was known at that 
time of the history and real danger from the disease, and nothing 
of the modern methods of detection. But long before there 
were any laws on our statute books making provisions for 
control of contagious diseases, we assisted many of our breed¬ 
ers in their endeavors to get rid of tuberculosis, by selecting 
out and destroying the affected individuals in their herds. 
The introduction of imported animals was doubtless an im¬ 
portant factor in the introduction of the disease. 
TO WHAT EXTENT DOES THE DISEASE PREVAIL IN IOWA ? 
The work done through this department during the last 
eighteen months, the occasional discovery of a seriously af¬ 
fected herd, and more frequently less severe outbreaks, have 
led to the frequent repetition of this question. 
While a considerable number of tests have been made, and 
these in various parts of the State, we are not yet in possession 
of a sufficient amount of evidence on this point to furnish 
more than an approximation to a definite answer. The evi¬ 
dence of the existence of tuberculosis has been demonstrated 
over and over, but to attempt to deal with percentages 
would be to enter the field of conjecture. It must be kept in 
mind that tests have been made where some form of dissase 
was known to exist, or was believed to be present. The un¬ 
suspected herd has not as a rule been tested. Under these 
circumstances, the number of cases found to be diseased in 
proportion to the whole number tested will greatly exceed 
the general average of cases in the State to the entire number 
of cattle. Again, the proportion of the affected individuals in 
a diseased herd varies greatly. The time during which the 
disease has existed, the conditions under which the animals 
