536 
and perfect harmony exists between their healthy appearance and 
their healthy conduct. It is only when the tuberculin test is applied 
to them that their tuberculous condition is revealed, and it is only 
wdien the substances that are eliminated from their bodies, feces, 
saliva, milk, etc., are subjected to microscopic an$l other tests that 
the proof is obtained of their dangerous character for public health 
and for the health of other animals. 
Cattle like those shown in the illustrations supply the best proof we 
can obtain of the possibly dangerous character of dairy cows that are 
not specially proven to be free from tuberculosis by a careful applica- 
tion of the tuberculin test. These cattle are in excellent condition. 
Most of them are in better bodily condition than can be expected of 
ideal dairy cows that give large quantities of milk. They show no 
symptoms of disease and act precisely like normal, healthy animals. 
A cow like the subject of illustration No. 23 shows that cows with 
tuberculous udders may remain undetected until the tuberculin test is 
applied to them, and a cow like the subject of illustration No. 25 
proves conclusively that apparently healthy tuberculous cows may, at 
any time, without previous warning, suffer an acute extension of the 
disease with which they are affected to their udders, through which 
their milk becomes so badly infected with tubercle bacilli that its use 
in a raw state would be suicidal. 
We may conclude that the general appearance of tuberculous cat- 
tle, until the disease is near its last stages, or has become generalized, 
or has dangerously encroached on vitally important organs, is like 
that of healthy cattle, and that the visibly good or bad condition of 
cattle is more a question of sufficient feed than of tuberculosis in its 
earlier stages. 
There was a time when veterinarians believed themselves competent 
to diagnose pulmonary tuberculosis of cattle in its earlier stages by 
physical examination, but most veterinarians, more particularly those 
who have had large experience in the examination of bovine lungs by 
means of ausculation and percussion, are now convinced that this is 
rarely possible. The broad, flat ribs, the thick hairy hide over the 
thorax, the transmission of sounds from the intestinal tract, which is 
enormously large because of the coarse materials ruminants eat, and 
the common location of tuberculous disease in the dorsal portion of 
the lung and in the mediastinal space, where it can not be detected at 
all from without, are a few of the conditions in cattle that interfere 
with the satisfactory application of the means of diagnosis that are 
of high value when they are applied to the more tractable and much 
smaller bodies of persons. 
In looking over the pictures given in this article it is desirable that 
the reader should bear in mind that no -special effort was made to ob- 
tain photographs from many different sources so as to present ex- 
