The drying of the subsoil has been regarded as a chief cause of the reduction of consumption (page [226]). It is probable, however, that the wet soil merely predisposed to consumption, because it was commonly associated with cold and wet houses, which would favour catarrhs, and open the way for the infection of consumption.
The dryness of the house is a most important matter. If a damp soil means also a damp house it must favour consumption and other chest affections. Damp air, like water, rapidly abstracts heat from the body. Compare, for instance, the discomfort of sitting clad in water at a temperature of 65° F. with the comfort of sitting clad in a dry room at the same temperature! The domestic fowl is naturally immune to anthrax; but by being kept for a few hours with its feet in cold water, it can be rendered susceptible to inoculation with this disease.
The effects of breathing foul air are clearly shewn by the varying death-rate from phthisis in different occupations. Thus, if the comparative mortality figures of agriculturists be represented as 100, that of a commercial clerk = 176, of a draper = 200, of a tailor = 211, of a printer = 244, of a bookbinder = 246.
The effects of breathing dust-laden air are even more marked. Thus, if the comparative mortality figures from phthisis of agriculturists = 100, that of a coal-miner = 166, of a mason = 215, of a chimney-sweep = 249, of a file-maker = 373, of a cutler = 407, of a potter = 453. The last figure probably also shows the influence of alcoholism, which greatly favours tuberculosis.
Means for Preventing Tuberculosis.—The means for preventing tuberculosis from infected milk and meat have been already indicated. They comprise—
(a) Means of eradicating tuberculosis from cattle;
(b) Means of preventing harm from tubercle bacilli in milk or meat;
Under the first head improved conditions of housing of cattle, greater air-space, improved ventilation, a larger proportion of out-door life are important. The use of the tuberculin test, the separation of healthy from diseased cattle; the disinfection of sheds occupied by infected cattle are also essential.
Under the second head come efficient sterilization of suspected food (see p. 13), and the rejection of diseased meat. (See p. 24).
The most important measure against tuberculosis is the prevention of infection from patients with consumption. Under this head are comprised the following steps:—