X.

The requirements of the system differ greatly, according to the degree of heat, the purity of the air, and the degree of physical exercise. What suffices at the equator would be but a morsel at the pole. What sustains the quiet student would starve the active athlete.

When Volney spoke in surprise of the few ounces required to sustain the Bedouin, he forgot the purity of the air of the desert, as well as the indolent life of the Arab.

When we offer as example the frugal diet of Cornaro, which was twelve ounces of solid food, with fourteen ounces of wine, daily, we must remember that the celebrated man lived a life of moderation, avoided bad air, and guarded against the extremes of heat and cold.

The data of Frerichs, the observations of Sir John Sinclair, and the determinations of Professor Horsford, show that eighteen ounces of properly selected food may sustain life; and they also show that the nutrient substances must be of known value.