It is the general belief that pulmonary tuberculosis in the overwhelming majority of cases is the result of inhalation of tubercle bacilli. This seems such a natural and easy way to account for tuberculosis of the lungs. This explanation is supported by numerous experiments on animals in which forced inspiration of bacilli appeared to be followed by direct localization of bacilli in the lungs. The inhalation theory is also in harmony with the well-known fact that living bacilli occur in the dust and in droplets of sputum about tuberculous patients that use little or no care to prevent contamination of their surroundings; and with the further fact that commonly there is no lesion discoverable elsewhere in the body to which one can trace the pulmonary disease.
Nevertheless important objections are being urged against the inhalation theory of pulmonary tuberculosis, especially in its extreme form, which tends to minimize the dangers