eter at Wesleyan University was so prophetic of worthy contributions to science that he was chosen to organize and direct the work of the Nutrition Laboratory of the Carnegie Institution, which is situated in Boston. The Germans, as ever, have also been leaders in this experimental work, an important contribution having come from the laboratory of Professor Flügge of Breslau. The English have been and are still contributing some of the most significant facts, especially a group of men led by Dr. Haldane of the University of Oxford. The work of Dr. Leonard Hill of London has become widely known through the public prints. The eminence of these various men is indicative of the interest which the homely subject of fresh air can arouse in us.
Several of the investigators have placed men within small closed experimental chambers, arranged with tubes passing through the walls to the outside air, so that the subjects within can at will rebreathe the hot, close, confined air or take in the fresh air from outside. Under such conditions it is found that confinement within and breathing of the unventilated air soon brings on the usual symptoms. If the subjects then breathe through the tube the fresh cool air from outside they obtain no relief. If they step outside relief comes instantly. If, on the other hand, a person standing in the fresh air outside breathes through the tube the stale air of the chamber, which has been breathed over and over again by the subjects within, the unpleasant symptoms do not appear; if he steps inside, they begin to appear at once. If with subjects within feeling the ill symptoms electric fans be started and the stale air be vigorously stirred, thus driving the hottest air away from the skin, relief comes at once. These fundamental experiments have been performed in varied ways, and have been supplemented by many others. Their results have accorded well with one another and allow but one general conclusion, namely, that the evil effects exerted upon human beings by air that has become vitiated by human beings result not from a lack of oxygen, not from an increase of carbon dioxide, not from the presence of an organic poison, not from any chemical features of such air acting through the lungs on the tissues, not in any manner from the rebreathing of such air, but solely from the physical features of excessive heat and excessive humidity interfering with the proper action of the skin in regulating bodily temperature. The problem of bad air has thus ceased to be chemical and pulmonary, and has become physical and cutaneous.
With this knowledge before us it is clear that in the ventilation of the future attention should be focused less upon the chemical purity of air, although of course there are ultimate limits to chemical purity, and more upon the maintenance of a physiologically proper temperature and humidity. What here constitutes physiological propriety varies with individuals, with age, with clothing, with occupations and with
