When this condition is induced by breathing noxious gases, the best results are obtained from oxygen. Sometimes a free current of fresh air is sufficient to restore persons rendered unconscious by an escape of gas or by the products of combustion retained within a room; but, in extreme cases, pure oxygen would seem the only means of saving life. Limousin has reported a case of asphyxia from carbonic acid inhalation, with intense cyanosis, which recovered under the use of oxygen, and in which he was able to verify a steadily increased elimination of carbonic acid by the lung, in proportion to the oxygen taken (Comptes Rendus, Societe de Therapeutique, 1868). M. Constantin Paul has recorded many cases, including cyanosis from obstructed respiration, coma from opium-poisoning (when the respirations were only seven per minute), and asphyxia from carbonic oxide, all quickly and markedly relieved by oxygen (Bulletin de Therapeutique, August, 18G8). Rabuteau refers to an instance of its good effect in asphyxia from sewer-gas, when ordinary means, employed by M. Griscolle, had failed to relieve ("Elements," p. 48); and finally I may quote a striking case recently reported by Dr. Charles B. Ball. A man, wife, and daughter, were found unconscious in a small room where there had been, through the night, a large fire, though the chimney was blocked. The two adults recovered with fresh air and ordinary means, but the daughter, aged sixteen (phthisical), remained unconscious and convulsed. After many hours of stimulating treatment she seemed to be dying; respiration was feeble and slow, the pulse imperceptible; then she was made to inhale pure oxygen, afterward oxygen and air. "The effects were rapid and marked:" respiration, color, and pulse improved, and though at first convulsed, she ultimately recovered. Dr. Ball, impressed by this case, and remembering Reynault's proof that man can live in an atmosphere strong in carbonic acid, provided that the proportion of oxygen is also increased, has contrived an apparatus with a reservoir of oxygen and a mask for safe use in dangerous mines. He has himself safely respired an atmosphere containing 18 per cent. carbonic acid with 30 per cent. oxygen added (British Medical Journal, i., 1878). If we compare the result in Dr. Ball's case with the fatal course of such cases of gas-asphyxia as, e.g., may be found in the Edinburgh Journal, 1874, we shall better realize the importance of using oxygen in preference to other measures. In various forms of poisoning, whenever death threatens from asphyxia, as under prussic acid, chloroform, etc., artificial respiration, i.e., supplying more oxygen, offers the best means of saving life.

Rosenthal and Leube found that the symptoms of strychnia-poisoning might be deferred or prevented by artificial respiration (Reichert's Archiv, 1867). H. Ebner thought the same result could be obtained by rhythmical movements of the limbs without supplying more air to the lungs, but Ananoff has since proved that pure oxygen is distinctly antagonistic to strychnia-action, and that when supplied to animals poisoned by this alkaloid it relieves them more than free access of ordinary air, or any movements (Centralblatt fur Medicin, No. 27, 1874).