WHAT PROFESSOR BANO’S WORK TEACHES. 
171 
cattle, but the actual extent of the disease as revealed by the use 
of tuberculin was something of a surprise. In testing more than 
53,000 cattle it was found that 38.5 per cent, of them were 
tuberculous to a greater or less degree. Moreover, it has been 
shown that the germs of tuberculosis are not omnipresent, be¬ 
cause many herds are entirely free of all traces of this disease 
and in some of these healthy herds the cows were large pro¬ 
ducers of the class. 
Degree of Contagious 7 tess of Ttibercitlosis. —It has been 
clearly shown that the longer the disease exists in a herd the 
greater is its prevalence, leading to the belief, which is substan¬ 
tiated by other observations and experiments, that long contin¬ 
ued contact is necessary for the extensive prevalence of tubercu¬ 
losis in the herd and the longer such contact has existed the 
more extensive will be the spread of the malady. That some 
herds remain healthy notwithstanding the fact that they have 
been exhibited at cattle shows and in public places where they 
must inevitably have been exposed to the germs of tuberculosis 
for a short time, indicate that such exposure is not always 
dangerous. The infection in many herds has been traced to the 
introduction of a single diseased animal. 
The Infectiousness of Milk. —The milk from tuberculous 
cattle has been knov/n to produce tuberculosis in calves and 
swine in very many cases and also, strange to say, in such a 
comparatively immune animal as the horse. Attention is called 
to the dangers that accompany the nse of skimmed milk from 
creameries, because if part of this milk is supplied by tubercu¬ 
lous cows and the mixed product is returned to the farm the 
disease may in that way be communicated to healthy herds, and 
common observation has proved that this is not rare. It is ad¬ 
vised to heat all such skimmed milk to 185° F. before it is used. 
This destroys the tubercle bacilli. 
Heredity. —Tuberculosis is rarely inherited and in all but the 
most exceptional' instances the calves of tuberculous cows are 
sound when they are born and if removed from contact with 
tuberculous' animals and fed on milk from sound cows or milk 
