It was formerly held that cows with heads narrow between the horns,
small thin necks, narrow chests defective also in depth and length,
loose projecting shoulders and elbows, pendent, pot bellies, with hollow
flanks, and a general laxity of the frame were especially predisposed to
tubercle. In many such cases the suspected animal was already the victim
of the affection, which had brought out these characteristic features of
weakness and emaciation. In other cases the unthrifty appearance was due
to poor feeding and care or to chronic disease, which in robbing the
system of vigor and hardihood laid it open to the attack of the tubercle
bacillus whenever it was introduced. Even when there was no such
depressing influence affecting the individual, the inheritance of such a
frame, betokened a constitution lacking in vigor, and with little power
of resistance to the invading microbe. Some milking breeds which tend to
the above conformation, show an unusual development of the lymph glands
and plexuses, and as tuberculosis attacks the lymphatic system
preëminently, the bacillus finds an especially favorable field for
development in such systems. It would, however, be an error to assume
that the compact, rounded frame, with circular chest and abdomen, and
full, firm neck and shoulders, with a great disposition to fat and
little to milk, is in any degree immune. Under the presence of the
tubercle bacillus, and close stabling, they often succumb quite as
rapidly as the most susceptible milking breeds. The meat producing
breeds with a strong propensity to fatten, have an extraordinary
development of lymph spaces and plexus in the intermuscular and
subcutaneous connective tissue, and the microbe finds a welcome home in
their sluggish, inactive and atonic systems as well as in the typical
dairy cows.