This section is from the book "Warne's Model Housekeeper", by Ross Murray. See also: Larousse Gastronomique.
This is the reason that want of food causes shrinking of the body; it is an actual wasting in the fire. The fat of the body, which is the most combustible part, goes first, and afterwards the muscles. The animal heat expires, and death comes to close the sufferings of starvation.
The air, which acts so important a part in generating or causing animal heat, is composed principally of two gases, called oxygen and nitrogen, unequally mixed; it is composed of about one gallon of oxygen to four of nitrogen. It also contains small quantities of vapour of water, carbonic acid, and ammonia. The word " gas " means air, but the atmosphere is a compound of two gases, as we have said. The oxygen in the air sustains life by keeping up the animal heat, and giving vitality to the blood.
We breathe it in (i.e. inhale it), and it mingles with our blood in the lungs, which it turns to a bright red colour. Blood before the oxygen meets it is a dark purple.
This fact accounts for the pale cheeks and lips of people who breathe impure air, or air not quite fresh. Oxygen is the purest air; if there is not enough in our share of the atmosphere, the blood cannot turn a beautiful red: therefore, dwellers in towns where the allowance of oxygen is small, are pale; country folks who get plenty of oxygen are rosy and fresh-looking.
The reason why oxygen turns the purple blood red, is this: - The colouring matter of the blood is formed of very minute globules floating in it, the oxygen uniting with the coats of these globules makes them milky-looking, and the dark colouring matter seen through this milky tinge appears of a bright red.
Oxygen, as we have said before, causes combustion or heat by combining with the carbon which is the chief element in the blood, and thus sending warmth through all the capillary vessels. We swallow, of course, the mixture of nitrogen and oxygen of which the air is composed; but after we have absorbed the oxygen into the blood in the lungs, we breathe back carbonic acid which mixes with the air.
Thus the air breathed in houses and rooms is rendered impure - that is, full of carbonic acid - and requires to be constantly renewed fresh from the outside air or atmosphere. The reason why the atmosphere or whole body of the air is not gradually rendered bad by human beings thus absorbing the oxygen, is because the under surface of vegetable leaves gives out oxygen as long as it is daylight, and thus preserves the due proportion of oxygen and nitrogen in the air.* But you will say, where do the plants get this oxygen? Partly from the atmosphere, also from the earth which contains carbonic acid gas - that is, carbon and oxygen mixed - derived from the air through drops of rain. From the decay of vegetable and animal matter, and from the stones, which are full of carbonic acid in a solid state, the roots of trees and vegetables draw up, by capillary attraction,† this carbonic acid from the earth into their sap; they keep for themselves (for the formation of wood) the carbon, and return the oxygen from the under surface of their leaves to the atmosphere.
Thus God has made animal life to depend on vegetable life; for unless the plants returned to the air enough oxygen to supply the loss caused by our consumption of it, the atmosphere could not supply us with the breath of life.
But if we are so much indebted to the vegetable world, it also is de†Capillary attraction is the power which very minute tubes possess of making a liquid rise in them above its own level. The smaller the tube the higher the liquid will be attracted up it, pendent upon us. The plants, as we have said, require carbonic acid for their nourishment; now animals all exhale carbonic acid into the air, and thus supply the plants with it, in return for the oxygen which vegetation gives out. Thus all things are linked together in the golden chain of reciprocal benefits.
* The great currents of air circulating from the equator to the poles, and from the poles to the equator, also preserve the purity of the atmosphere, and keep up life by supplying the plants with carbonic acid borne from fully populated regions, and the populated regions with oxygen from the plants of little-inhabited lands. The fall of rain also washes impurities from the atmosphere.
This carbonic acid gas is a foe to animal life if inhaled. It is the most deadly of poisons. It was the cause of the death of the British prisoners in the Black Hole of Calcutta; as choke-damp it causes death sometimes in mines or deep wells, and even if inhaled slightly in the impure air of a heated or crowded room or church, it is dangerous to health. It is a narcotic poison, and its presence may be divined by a sense of drowsiness and lassitude. We have said much about it already in our former passages on Ventilation.
No fire will live in an atmosphere of carbonic acid; therefore candles let down into wells and placed in suspected rooms, are sure tests of the air. Where a candle will not burn a man cannot live. Fire (i.e., combustion) depends, you remember, on the union of carbon, or charcoal, and oxygen; if there is no oxygen there can be no fire.
You will perhaps wonder why there should be so much nitrogen (or bad air as we call it) mixed with the oxygen of the atmosphere. It is meant to dilate the oxygen, which has such great powers of combustion, that if it were not thus mixed, and weakened or diluted with nitrogen, it would quickly exhaust our lives by burning us up with animal heat.
We think these few hints will show the mother of a family the need of keeping the air of her house pure; and the benefit of "green leaves," which are not only ornamental, but useful in feeding the flame of life, Dear housemother, let your little ones, if you live in a town, have green plants and flowers in their nurseries, and walk in the parks near the life-feeding trees.
The necessity of being much in the open air will be made apparent by these facts.
 
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