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AIR.

CHAPTER IV.OF AIR.

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Unwholesome air is a very common cause of diseases.Few are aware of the danger arising from it. Peoplegenerally pay some attention to what they eat and drink, butseldom regard what goes into the lungs, though the latterproves often more suddenly fatal than the former.

Air, as well as .water, takes up parts of most bodies withwhich it comes into contact, and is often so replenished withthose of a noxious quality as to occasion immediate death.But such violent effects seldom happen, as people are gene-rally on their guard against them. The less perceptibleinfluences of bad air prove more generally hurtful to mankind ;we shall therefore endeavor to point out some of these, and toshow from whence the danger chiefly arises.

Air may become noxious many ways. Whatever greatlyalters its degree of heat, cold, moisture, &c. renders it un-wholesome./ For example, that which is too hot dissipatesthe watery parts of the blood, exalts the bile, and renders thewhole humors adust and thick. Hence proceed bilious andinflammatory fevers, cholera morbus, &c. Very cold air ob-structs the perspiration, constringes the solids, and congealsthe fluids. It occasions rheumatisms, coughs and catarrhs,with other diseases of the throat, breast, &c. Air that is toomoist destroys the elasticity or spring of the solids, inducesphlegmatic or lax constitutions, and disposes the body toagues, or intermitting fevers, dropsies, Sec.

Wherever great numbers of people are crowded into oneplace, if the air has not a free current, it soon becomes un-wholesome. Hence it is that delicate persons are so apt toturn sick or faint in crowded churches, assemblies, or anyplace where the air is exhausted by breathing, fires, candles,or the like.

In great cities so many things tend to pollute the air, thatit is no wonder it proves so fatal to the inhabitants. The airin cities is not only breathed repeatedly over, but is likewiseloaded with sulphur, smoke, and other exhalations, besidesthe vapors continually arising from innumerable putrid sub-stances, as dunghills, slaughter-houses, &c. All possiblecare should be taken to keep the streets of large towns open