Elementary biology; an introduction to Elementary biology; an introduction to the science of life elementarybiolog00grue Year: 1924 340 ELEMENTARY BIOLOGY that it is the excess of air that interferes with life there; no light is available in such places. If we consider artificial conditions produced by the digging of mines or the use of caissons under water, it is indeed true that these conditions interfere with normal life processes; but they do this not because there is too much air, but because the Fig. 159. The wind as an obstacle to life The wind, often helpful to life and growth, is
Elementary biology; an introduction to Elementary biology; an introduction to the science of life elementarybiolog00grue Year: 1924 340 ELEMENTARY BIOLOGY that it is the excess of air that interferes with life there; no light is available in such places. If we consider artificial conditions produced by the digging of mines or the use of caissons under water, it is indeed true that these conditions interfere with normal life processes; but they do this not because there is too much air, but because the Fig. 159. The wind as an obstacle to life The wind, often helpful to life and growth, is sometimes a hindrance. In the picture the wind, besides making the tree grow one-sided, and bending over the top branches, has blown the earth away from the roots. (Photograph lent by New York Botanical Garden) human beings that go into these places are not adjusted to the high pressure} Nor is there any place on earth where there is naturally a scarcity of air, except on the very highest mountain tops; but in these situations other conditions are sufficiently unfavorable to life, so that we do not usually think of the absence of plants and animals in these places as due to the lack of oxygen. 1 The distressing disease known as '' the bends,' which affects many of those who have to work in the high-pressure atmosphere of the caissons, is very easily avoided by taking sufficient time to enter the working chamber and sufficient time to come out. The disease is not caused by the high pres- sure ; it is caused by the sudden change from high pressure to the normal pressure of the surface atmosphere.
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