The circular recently issued by the Health Department of the City of New York, in relation to the prevention of tubercular consumption, is undoubtedly founded upon the most advanced laboratory investigations of the life history of the bacillus which is supposed, in the present state of our knowledge, to constitute the "contagium vivum" of this disease; but it is hardly characterized by a sufficient degree of practical applicability to warrant the hope of an immediate abolition of infection. Granting the postulate that the "living germs" in the sputa of consumptives, expectorated "on the street, floors, carpets, handkerchiefs, etc.," may, after drying, "float in the air as dust," and admitting the germicidal efficacy, even in a highly albuminous medium, of mercuric chloride, it is still difficult to understand how the prophylactic directions of the circular are to be generally carried out. In the population of New York there are probably more