transformation of matter in the body, which are regulated by the requirements of breathing. The inhalation of oxygen is not a primary but a secondary thing. When we inhale air at every breath richer than usual in oxygen—for example, when breathing highly compressed air, as divers do, or laborers on the pneumatic foundations of bridge-piers—the result is not a larger consumption of matter and an increased production of carbonic acid, but merely a decrease in the number of inhalations. If in air of ordinary density we make about sixteen respirations in a minute, in air of greater density we should involuntarily make only twelve, ten, or eight, according to the density and our need of oxygen; all else remains the same.
Lavoisier, and, half a century later, Regnault and Reiset, placed animals for twenty-four hours in air very rich in oxygen, but they did not consume more of it than in the ordinary air. An increase of oxygen in the air, therefore, or pure oxygen gas, only produces an effect in certain morbid conditions, in cases of difficulty of breathing, or where breathing has been for some time suspended, because an inspiration communicates more oxygen to the blood than breathing ordinary air. A healthy person can, however, without difficulty or injury, compensate for considerable differences, and an increase or decrease of one or two per cent, of oxygen does no harm, for under ordinary circumstances we only inhale one-fourth of the oxygen in the air we breathe; we inhale it with twenty-one per cent, and exhale it with sixteen per cent.
So far, therefore, as we feel ill or well in a winter garden, it does not depend on the quantity of oxygen in the air, and there is no greater appreciable quantity of oxygen in a wood of thick foliage than in a desert or on the open sea.
Let us also for a moment consider the ozone in the air, which may be looked upon as polarized or agitated oxygen. After its discovery, which has immortalized the name of Schönbein, was made known, it was thought for a time that the key had been found for the appearance and disappearance of various diseases, in the quantity of ozone in the air. But one fact, which was observed from the first, shows that it cannot be so; for the presence of ozone can never be detected in our dwellings, not even in the cleanest and best ventilated. Now, as it is a fact-that we spend the greater part of our lives in our houses, and are better than if we lived in the open air, the hygienic value of ozone does not seem so very great. Added to this, the medical men of Königsberg long had several ozone-stations there, during which time various diseases came and went, without, as appears from the reports of Dr. Schiefferdecker, ozone having the slightest connection with the appearance or disappearance of any of them.
Dr., assistant at the Hygienic Institute at Munich, has lately been occupied with the question of the sanitary value of ozone, but has arrived at only negative results.