The American Association for the Advancement of Science Standards of Ventilation in the Light of Recent Research.

THE fact that the stagnant air of an occupied room becomes uncomfortable and mlakes those who are exposed to it listless anid inert is a matter of common experience. W'hen overcrowding in a close unventilated space reaches a certain point the results nmay even be fatal within a few' hours, as in the Black Hole of Calcutta, the underground prison at Austerlitz and the hold of the ship Londonderry. Conversely the value of fresh air in the treatment of tuberculosis and other diseases is one of the fundamentals of medical and hygienic practise. For the sanitarian it is necessary, however, to know something more than this general fact that bad air is bad. He must not only have some workable conception as to its operation, but also a more or less definite standard of permissible deviation from absolute purity. In the earlier days of ventilation this was an easy task. It was natural to assume that the evil effects of the air of occupied rooms was due, either to lack of oxygen or excess of carbon dioxide, or to the presence of some specific organic poison of human origin-morbific matter or anthropotoxin, as this hypothetical substance was called. Of either of these changes the amount of carbon dioxide shouild serve as a fair mneasure, and a carbon dioxide standard was therefore confidently advanced by the older sanitarians as a practically all-suffi-