AGE.
In both man and beast, age appears to have a predisposing effect, but apart from debility or trauma, this may be fully explained on the ground of often repeated infection, an indoor life, and, in dairy cows, the excessive drain upon the system. In thoroughbred herds of cattle, in which the cows are preserved as long as they will breed, and in dairies where they are kept as long as the milk yield is satisfactory, the oldest show by far the largest percentage tuberculous. In secluded individual dairies we have found 100 per cent. affected, Ostertag gives the average for Berlin at 75 per cent., and Bang for Denmark at 69 per cent.