same direction. They both get rid of waste, and with it of the poisons in the system, which are depressing various organs. We need not, therefore, be surprised when we are told by Sir D. Galton that after barracks were better ventilated the rations of the men had to be increased; or by "the pathetic story" of certain seamstresses whose work-room was ventilated, and who then begged that the old state of things might be restored, as their appetites had increased beyond their earnings. Sir D. Galton gives another experience, illustrating the depressive effect of these poisons upon the functions of life. A New York medical man rather cruelly shut up some flies without food, some in foul air, others in pure air; the pure air being constantly changed. To his surprise, the flies in the pure air died first, these dying from simple starvation; while the flies in the foul air died from poison, and with the tissue of their bodies unexhausted, indicating how the functions of life were carried on to the last where oxygen was available, but had been slowed and depressed by the presence of the poison, so that life was actually maintained longer in the foul than in the pure air. To take one more example. Parkes tells us (page 159) that it was found in the case of miners that they required six thousand cubits of air introduced per man per hour (this included the air necessary for horses and lights) to be able to work at their best. When this quantity was reduced to one third or one half, there was a great reduction in their working energy. In other words, the poison within their system being imperfectly oxidized, impaired their faculties.
We could wish that it were possible to write the whole of the noble story of oxygen from a physiological point of view. It is a double service that it performs for us. It not only, as we have seen, neutralizes the deadly poisons resulting from waste, but it provides the heat and energy, by the oxidizing or burning up of this waste. All through animal life the consumption of oxygen, serving this double purpose, is the measure of activity. Just as reptiles and cold-blooded creatures consume small amounts of oxygen and develop little activity, so birds and insects consume im-
- We may also take the case of races living in hot and cold climates. In hot climates we breathe a smaller quantity of oxygen (owing to the expansion of gases) than in cold climates. Thus, taking two climates, one of 32° F. and the other of 80° F., we should inhale about 2,164 grains of oxygen per hour in the one climate (the cold), and only 1,971 in the other climate (the warm), or a difference of about nine per cent (Galton, Our Homes, p. 498). This would in part account for the difference of energy that exists in the races of hot and cold climates; just as our own energy varies considerably on hot days and keen frosty days, though we think some allowance ought to be made for the more open-air life that would be led in the warm climate. The bearing of these facts upon crowded rooms should be perceived. As the room gets hotter, not only are we breathing more poison, but less oxygen, which is the only remedy for the poison. We are therefore doubling the causes of evil.