CHAPTER XVII.

TEMPERATURE OF APARTMENTS.

FEW if any, ordinary buildings, whether churches, houses, shops, or factories, are so constructed as to preserve exactly the same temperature in every apartment, at all seasons of the year. As for heating themselves, and preserving one uniform temperature by means of the very employments or manufactures which are being carried on within them, probably no one ever heard or thought of such a thing. A self-heating-house! Why, it would excite as much astonishment, as would a machine that was really endowed with the power of perpetual motion.

And yet the House I live in has this power, wonderful as it is, not only of heating itself, by the process of generating and purifying the blood, concerning which I have before treated, and by other very curious processes, but also of regulating that heat, and keeping it at the same point, with scarcely any perceptible variation.

The heat of the human body is never far from ninetyeight degrees of Fahrenheit's thermometer. By this is meant, that if the bulb of the thermometer, which contains the quicksilver or mercury, could be plunged into the flesh of the body, or even if it were to be held in the mouth, the mercury would rise in the tube till it arrived at the mark which indicates 98° or thereabouts, and there would remain.

Now why does this heat continue nearly the same at

all times and in all places? If you were to take a piece of wood, or iron, about the size and shape of a man, and heat it to 98°, and set it up in Greenland or Lapland, where it is so cold that the mercury would sink to 20° in the open air, do you think this iron would remain heated to 98°? Would not the air cool it down to about 20°? How would it be with a man of wood or straw? How would it be even with the body of a dead man?

Does any one suppose that the body of a dead man, heated to the same temperature as that of a living being, would remain warm very long? Then why should the living body of a man? Why does not the cold air rob it of its spare heat, just as it would a mass of straw or iron? Yet the daily experience of our lives proves that it does not.

The skin and the outside of the hands, the face, and other parts of the body, may be very cold, and sometimes even actually frozen, but the blood and the flesh will generally remain at about the same temperature, unless the individual be absolutely frozen to death. In that case, the heat very rapidly escapes; the dead, as you know, very quickly becoming cold.

Curious Question.-But why the heat does not escape from everybody under ordinary circumstances, so that they become frozen to death, is the point in question. You will hardly suppose that there is a fire in the inside of us which keeps up the heat: for, if So, what supplies the fuel? Spirits will burn, it is true, and when applied to many chemical and other purposes, afford the means of giving heat. Yet in the human body this is not the case, except perhaps for a very limited period. Although many persons adopt the per

nicious habit of frequently drinking intoxicating liquors, yet their blood is in reality no warmer than is the blood of those who refrain from this practice; nay, it is even asserted by some experimenters, that the blood of the dram-drinker is actually a little colder than the blood of him who drinks little else but pure water.

When we think of all this, and remember that individuals can live very comfortably in climates like Labrador, and Greenland, Norway, Lapland, and Siberia, where everything around them-air, water, earth, trees -is cooled down to less than half the heat of the human body, for the greater part of the year, and as low as the freezing-point (30° of the thermometer) a considerable portion of the time, is it not a wonder, that all our bones and flesh and blood can retain a temperature of 98°, not only through an hour, a day, or a year, but throughout the whole of perhaps a very long life?

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It is indeed almost a miracle, or would be thought so, if we concerned ourselves at all about it. It shows, at least, how wonderful life is. For not only man, but all living animals have this same power. Birds have even a higher degree of heat than man. The blood of some birds reaches a temperature of about 108°. If it were not so, they would soon become frozen to death in the cold season, and their bodies would probably become separated and fall to pieces, in like manner as the frost in swelling sometimes cracks the frozen ground, or as trees are sometimes split into fragments, in very severe winters.

You should be told also, that living trees and shrubs, and plants, and seeds, have this same power of resisting cold, though in a less degree than is possessed by

animals. Trees do not often freeze very completely; and were it not for this contrivance of the great Creator, everything would perish in the winter, and we should have no beautiful foliage and verdant meadows in the spring. Seeds and roots would decay in the ground, and the regular return of the seasons would not produce those beneficent results, which gladden our hearts and supply our wants.

But we not only have this wonderful power of resisting cold; we are also equally able to resist extreme heat. By long practice, men have been enabled to remain in ovens, and other places, heated to 220°, and even to 260° of Fahrenheit, for ten or twelve minutes at a time. The only serious inconvenience which arises in such cases is an extremely profuse perspiration.* But a piece of flesh without life, if subject to so great a heat for only a few minutes, would be thoroughly baked, and the organization of the part irreparably destroyed. This heat is much greater than that of boiling water, which, as you know, is 212, measured by the same thermometer.

Having laid down and illustrated the general rule, that the temperature of our bodies does not admit of much variation, it may be as well to mention some of those slight varieties which under different circumstances are found to exist.

Variations of Temperature.-Infants, excepting when newly born, have a temperature only of about 94°. The heat increases as the body advances towards ma

* Perspiration always modifies the heat of the human body more or less, and is one means of keeping us cool. The reason is, that the moisture on the surface of our bodies evaporates, and this produces cold. It is said that you may almost freeze a man in midsummer, by keeping him wet with ether; so rapidly does the ether evaporate.

turity, after which it remains nearly stationary at about 98°, until it begins to decline, when a slight diminution takes place. In the spring, and in the beginning of summer, it increases a little, in people of every age; but it again declines towards winter; and when a person is greatly enfeebled by sickness, or otherwise, the temperature is slightly diminished. In fevers and in inflammatory diseases, it sometimes increases to 104°, and even to 107°.

But I have not yet told you how this steady temperature of 98° is kept up in the human system, notwithstanding the extremes of heat and cold to which it is exposed. Indeed I cannot do it; for I do not know the cause. It is in some way connected with the principle which we call life, but about the nature of which we are at present entirely ignorant. I have already told you that the evaporation of the matter of perspiration from the skin, has some effect in keeping the body cool; but this cannot be the sole cause why men can remain with impunity in places heated to a greater temperature than boiling heat. There are doubtless other and more important causes, but the limited sphere of human understanding has not at present enabled us to discover them. As to the reason why we retain so high a temperature as 98°, when the atmosphere is at a considerably less degree of heat, we know nothing. There have been a great many speculations started by ingenious philosophers in various ages and countries, but they have been in general mere guesses; in many instances hardly amounting to plausibility. The process of digestion, the formation of chyle, the change of chyle into blood, and the alteration made in the blood during its passage through the lungs-but more particularly the latter-all are believed

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