Tuberculosis is most prevalent and most fatal under conditions of social misery, and when the surroundings of the patient are insanitary. This chapter discusses ordinary sanitary measures in relation to the prevention of tuberculosis, it is convenient to consider the measures practicable against it. There are two ways in which overcrowding can be abated: one is the slow measure of official inspections, followed by official notices in the instances in which overcrowding is detected. The alternative remedy is the removal from the congested dwelling of those liable to convey infection. This has been done for typhoid and typhus fevers and for small-pox, and has led to an immense reduction in their prevalence. In scarlet fever and diphtheria similar measures have not been successful to an equal extent, because of the failure to track slight cases of these diseases, which remain at home or in school spreading infection.