Page:Popular Science Monthly Volume 91.djvu/522

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��Popular Science Monthly

��breathe through, but when it expands it may become large enough to close up com- pletely the breathing space in that nostril. It was found that warm air, from 80 to 90 degrees, has a tendency to make this turbinate bone expand. Warm, moist air is apparently more likely to do this than warm dry air. The man in one of the pictures is breath ing on a cold, shiny metal plate. The moisture in his breath condenses, is turned into water droplets on the plate and makes two little im- pressions whose size gives some idea of the breathing space. The black areas of the chart show that in this case the heated air of the room caused the turbinate bone in one nostril to expand considerably more than that in the other nostril. While this appreciably lessened his breathing space he was not so oppressed by the closeness of the room as he would have been if both nostrils had been affected to the same extent. This fact is of importance because this swollen or congested condition of the turbinates and adjoining membrane, accompanied as it is by increased secretion, has a good deal to do with catching of colds. The physical sensation resulting is like that of a cold in the head.

Why Even Warm Winds Are Cooling

The reader may be tempted to inquire why, if heat has such a pronounced effect on the body, we are not all sick in the summer time. The answer is that we are not all sick in the hot summer weather simply because we have means of keeping our bodies cool — as cool or actually cooler than when indoors in the winter time.

In the first place the body produces less heat in summer. In the second place, we wear lighter weight clothing in summer.

By reason of the excessively high tem- perature of the air about us in summer — 80 to 100 degrees — our bodies are caused to perspire much more freely than is the case in an atmosphere of 70 degrees indoors

���This man's body is exposed to the temperature of one room and his head to that of another. He is breath- ing the air from the first room. The temperature of his head is being taken with an attached thermometer. The experiment determine.-; exactly which part of the body is most af- fected by changes of temperature

��in the winter. Our clothing becomes damp on absorbing this moisture from the skin. Now, when' a current of air passes over a damp cloth it takes moisture away from the cloth : — or causes water to evaporate from the cloth. Heat is used up in converting water or moisture into water vapor. Place a damp cloth on the bulb of an ordinary thermom- eter — the cloth need not be cold — and expose this to a breeze. You will observe that the thermometer imme- diately indicates a lower temperature.

This is just what

happens to the bod}-.

When a breeze — even

though it be a hot breeze

— blows across damp skin

or damp clothes it extracts

heat. The body is exposed

more frequently to breezes

in the summer; for we are

out of doors more and even

when indoors we have the

windows wide open. This

outdoor air is only very

slightly purer chemically

than the cool indoor air of

winter. It is the cooling

effect — not, however, cool

enough to be chilling — which constitutes

refreshment. The ventilating engineer has

got to know the causes of "freshness."

��A

��Determining whether a student can do bet- ter mental work in a cool or a warm room

�� �