The various notices I have had the honour of presenting under this title have had the effect of demonstrating that changes of barometric pressure, if we except very rapid and great decompressions, have no physico-mechanical action upon animals and vegetables, but influence them exclusively from a chemical point of view. Below the normal pressure of the air too feeble tension of oxygen tends to promote asphyxia : above, too strong a tension tends to increase those formidable accidents which I have designated, somewhat paradoxically I admit, by the expression, poisoning by oxygen ; and hence the conclusion at which I have arrived, that all danger may be avoided by varying the oxygenous richness of the air inversely to the variation of pressure.

Apropos of the very remarkable effects of the respiration of atmospheric air enriched with oxygen confirmed by MM. Crocé-Spinelli and Sivel during their last aérostatic ascent, I remember to have obtained some long time since very analagous results.

This was in the year 1832, on the occasion of the great epidemic of cholera. A young physician employed me to administer to the cholera-patients of the ambulance of the Rue Grange-Batelière pure oxygen to assist in producing re-action. We operated upon the sick in the last stage of the malady, and some were saved by the employment of this means.