“There is one need before which hunger and thirst are silent, however great they may be; a need that is never satisfied, and is always making itself felt, whether we wake or sleep, by night, by day, every hour, every minute. It is the need of air. Air is so essential to the maintenance of life that it has not been left to us to regulate its use as we do in regard to food and drink; and this is so in order that we may not be exposed to the fatal consequences that would follow the slightest forgetfulness. Therefore it is with little or no consciousness on our part and independently of our will that air gains entrance into our body to do its marvelous work there. On air more than on anything else do we live, our daily bread coming only second in the order of importance. Our need of food is felt at only tolerably long intervals; our need of air is felt unceasingly, always imperious, always inexorable. Let any one try for a moment to prevent its admission into the body by closing the entrance passages, the mouth and the nostrils; almost immediately he is suffocated and feels that he would surely die if this state were prolonged a little. And what is true of man is true of all forms of animal life: air is necessary to them all, from the smallest to the greatest. “What I am going to tell you now will explain this absolute necessity for air for the maintenance of life. Man and also every animal of a superior organization—a classification that includes mammals and birds—have a temperature of their own, a degree of bodily heat peculiar to them, a heat resulting from no external conditions, but from the functions of life alone. Whether under a burning sun or in the freezing cold of winter, whether subjected to the torrid heat of the equator or to the glacial climate of the poles, man’s body has a temperature of thirty-eight degrees, centigrade, and cannot be lowered without danger of death. The natural heat of birds attains forty-two degrees in all seasons and in all climates.