Behring, who is a good authority on such questions and whose opinion, therefore, carries weight, accepts the view that everyone is slightly tuberculous, but this by no means implies that everyone is or will be affected with pulmonary phthisis. He thinks two things are necessary to produce phthisis: a tuberculous focus and bodily conditions favoring the development of the disorder. He regards the contagion of consumption in adults with grave doubt, holding that it has not yet been demonstrated. Therefore, the predisposition to pulmonary infection is not in exposure to infection which is shared by all more or less, but in the conditions of life. The more probable cause is the awakening of a latent focus into activity on account of defects of nutrition or from impairment of health.
Leaving out of consideration for the present his opinions as to the early infantile origin of pulmonary phthisis, his views are