our planet could be formed of ingredients which separately exhibit such striking peculiarities, and which combine in other proportions to form compounds all more or less fatal to life?
An atmosphere of pure oxygen would be too exciting to be compatible with long life in animals, even if we could imagine the existence of life in a blazing world; for not only those substances which are generally spoken of as combustibles, but even the metals, burn with great violence in oxygen.
In an atmosphere of nitrogen, animals could not exist at all; indeed this gas formerly went by the name of azote, the literal significance of which is "fatal to life."
Two volumes of oxygen mixed with eight of nitrogen form "the breath of life," but when these gases are combined in other proportions they form compounds which have very different properties.
One of these compounds is the protoxide of nitrogen, a gas which may be inhaled for a few minutes without danger, but which is incapable of supporting life for any length of time. When breathed it produces great mental excitement, and occasions a total loss of volition. The person who inhales it performs a hundred strange antics; he talks incoherently, laughs wildly, sings, dances, and sometimes fights; he feels that he is lighter than the atmosphere, and sees all things under a new aspect.