Physiology of the human skin. Of checking perspiration. Diseases thus produced. "Dirt" not "healthy." How the mistake originated. "Smell of the earth." Effect of uncleanliness on the morals. Filthiness produces bowel complaints. Changing dress for the sake of cleanliness. No mother will ever pay that attention to cleanliness which its importance to health and happiness demands, till she perceives its necessity. And she will never perceive that necessity till she has studied attentively the machinery of the human frame--and especially its wonderful covering. The skin is pierced with little openings or _pores_, so numerous that some have reckoned them at a million to every square inch. At all events, they are so small that the naked eye can neither distinguish nor count them; and so numerous, that we cannot pierce the skin with the finest needle without hitting one or more of them. When we are in perfect health, and the skin clean, a gentle moisture or mist continually oozes through these pores. This process is called _perspiration_; and the moisture which thus escapes, the _matter_ of perspiration. Perspiration may be checked in two ways. 1. by filth on the skin; 2. by what is commonly called taking cold--for taking cold essentially consists in chilling the skin to such a degree as to stop, for some time, the escape of this moisture. Most persons have doubtless observed, that in the first stages of a cold, they frequently have a very dry skin. Whereas, when we are in health, the skin usually feels moist. Our health is not only endangered, and a foundation laid for fevers, rheumatisms, and consumptions, by stopping the pores of the skin with dirt, or anything else, but there is also danger from another and a very different source. The blood, in its circulation through the body, is constantly becoming impure; and as it thus comes back impure to the heart, is as constantly sent to the lungs, where it comes in close contact with the air which we breathe, and is purified. But this same purifying process which goes on in the lungs, goes on, too, if the skin is in a pure, free, healthy condition, all over the surface of the body. If it is not--if the skin cannot do this part of the work--an additional burden is thus laid on the lungs, which in this way soon become so overworked, that they cannot perform their own proportion of the labor. And whenever this happens, the health must soon suffer. The strange belief, that "dirt is healthy," has much influence on the daily practice of thousands of those who are ignorant of the human structure, and the laws which govern and regulate the animal economy. It has probably originated in the well-known fact, that those children who are allowed to play in the dirt, are often as healthy--and even _more_ healthy--than those who are confined to the nursery or the parlor.