Inbred families are proverbially subject to tuberculosis. By pairing
individuals that show in a marked degree the desired qualities of early
maturity, heavy milking, or fattening, the greatest stimulus is given to
the enhancement of such qualities, and with this there is the
correspondingly ready receptiveness to the tubercle bacillus. To this is
added a degree of constitutional delicacy which comes from too close
breeding, and which otherwise shows itself in an encreasing infertility,
when bred with an animal that is nearly related. In addition, the high
bred animal is kept much indoors, where the bacillus, once introduced,
is easily preserved and propagated, and is denied the free outdoor life
and exercise which might develop muscle and vigor. This is no valid
argument for introducing inferior blood to the deterioration of the
economic value of a race, but rather for the complete exclusion of the
bacillus which may find in our treasured herd an especially inviting
field for its ravages.