Those cows found healthy were given the best of care, including a marked diminution of the amount of housing or confinement in barns, and were again tested at intervals of six months, several times, to weed out any others which might still have the infection in their systems. In a short time all signs of the disease disappeared, and no other cases developed in these herds unless fresh infection was introduced from without. To guard against this, each farm established a quarantine station, where all new-bought animals, after having been tested with tuberculin and shown to be free from reaction, are kept for a period of at least a year, for careful observation and study, before being allowed to mix with the rest of the herd. It is now a common requirement among intelligent breeders of pedigreed cattle to demand, as a formal condition of sale, their submission to the tuberculin test, or the certificate of a competent veterinarian that the animal has been so tested without reacting. Protected herds have now been in existence under these conditions, notably in Denmark, where the method was first reduced to a system under the able leadership of Professor Bang, of Copenhagen, for ten years with scarcely a single case of tuberculosis developing. Only a fraction of one per cent of calves from the most diseased mothers are born diseased.
Not only is the method spreading rapidly among the more intelligent class of breeders, but many progressive countries of Europe and states of our Union require the passing of the tuberculin test as a requisite to the admission within their borders of cattle intended for breeding purposes. So that, while the problem is still an enormous one, it is now confidently believed that complete eradication of bovine tuberculosis is only a question of time.
The other instance furnishes a much more crucial test, as it is carried out upon wild animals under the unfavorable conditions of captivity in a strange climate, like our slum-dwellers from sunny Italy, and comes home to us more closely in many respects, inasmuch as it is concerned with our nearest animal relatives on the biological side--monkeys and apes, in zoölogical gardens.
Tuberculosis is a perfectly frightful scourge to these unfortunate captives, causing not infrequently thirty, fifty, and even sixty per cent of the deaths. This, however, is only in keeping with their frightful general mortality. The collection of monkeys in the London Zoo, for instance, some fifteen years ago, was absolutely exterminated by disease and started over afresh _every three years_, a death-rate of thirty-five per cent per annum as compared with our human rate of about two per cent per annum. Here, it would seem, was an instance where there was little need to call in the bacillus. Brought from a tropical climate to one of raw, damp fog and smoke, from the freedom of the air-roads through the tree-tops to the confinement of dismal and often dirty cages in a stuffy, overheated house, condemned to a diet which at best could be but a feeble and far-distant imitation of their natural food, it seemed little wonder that they "jes' natcherly pined away an' died."