Over-exertion is well known to predispose to infection. The common method of origin of an ordinary catarrh is an illustration of this, and there are numerous instances in experimental bacteriology. It is important to recognise that, although exhausting exercise be taken in the open air, it is conducive to the development of consumption if it entails exhaustion or fatigue. The apparent influence of local injury in determining the site of tuberculous disease of bones and joints is well recognised. Injury to the chest wall has sometimes appeared to light up active phthisis. Tuberculosis is commonly associated with certain diseases, especially with chronic insanity. Certain acute infectious diseases, especially influenza, whooping-cough, measles, and to a less extent scarlet fever and enteric fever, undoubtedly favour the occurrence of tuberculosis. Good nutrition is considered by some authorities to play a very important part in the prevention of tuberculosis. Alcoholism is in fact the most powerful factor in the propagation of tuberculosis.