Page:Popular Science Monthly Volume 12.djvu/444

428 no epidemic in these houses, although it prevailed largely immediately beyond the English Garden and close to the Diana Baths in 1854 and 1873. It must have been accidental that no isolated cases occurred, as the inmates of the Chinese Tower, or the Kleinkessellohe, might have caught it in Munich as others did who came from a distance, but, had there been single cases, probably no epidemic would have occurred in these houses.

Even if these deductions must be accepted with caution from an etiological point of view, still, on the whole, they indisputably tell in favor of trees and woods.

Surface vegetation has also other advantages, besides its use in regulating the moisture in the soil; it purifies it from the drainage of human habitations, whereby it is contaminated and impregnated. If this refuse matter remains in soil destitute of growing vegetation, further decomposition sets in, and other processes are induced, not always of a salubrious nature, but often deleterious, the products of which reach us by means of air or water, and may penetrate into our houses. But from this indisputable fact false conclusions are sometimes drawn. Many people imagine that if a few old trees are left standing in an open space their roots will absorb all the impurities from the houses around, and render the refuse which accumulates beneath them innocuous. This idea is not only false in a sanitary point of view, but very injurious, as it prevents people from taking the measures which alone can keep the ground under our houses pure.

We will now explain why the shade of gardens and woods is at certain seasons so beneficial. The human race during its pilgrimage on earth and wanderings over it has many difficult tasks to perform. One of the most difficult is involved in the necessity that all our internal organs, and the blood, whether at the equator or the north pole, should retain an equable temperature of 37° Centigrade (98° Fahr.). Deviations of but one degree are signs of serious illness. The blood of the negro and that of the Esquimaux is of the same temperature, while the one lives in a temperature of 40° above, and the other 40° below zero (Centigrade). A difference of 80° has therefore to be equalized.

Our organism, doubtless, possesses a special apparatus for the performance of this colossal task, self-acting sluices so to speak, by means of which more or less of the heat generated in the body passes off: these consist mainly in the increase or diminution of the peripheric circulation, and the action of the pores of the skin. But we soon come to the end of our natural regulating apparatus, and have to resort to artificial means. Against cold we have excellent methods in clothing, dwellings, and fires; but at present our precautions against heat are very limited. This is, doubtless, the reason why higher civilization has extended so much farther toward the polar regions than toward