Page:Popular Science Monthly Volume 71.djvu/474

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POPULAR SCIENCE MONTHLY

growth. We are rather dull. We do not often stop to think about things. We buy a new horse which comes from the country, has never seen a train; drive him to the station, and are frightened, perhaps, because the horse himself is so much alarmed—possibly have a narrow escape because of the excitement which his first sight of a train causes him. But that horse, after a few months' discipline, will scarcely turn his ear, much less his head, to look at the train which a short time before so frightened him and held his attention that nothing else could get into his mind save the fright that train gave him. So we, too, act a good deal like the horse. We see a thing the first time and it surprises us; the next time it seems like an old acquaintance, a thing

Fig. 58. Section of the Epithelial Lining of the Human Œsophagus.

familiar and therefore unregarded. I say this apropos of the skin. How many of you have thought what the lesson of the skin is in regard to the power of growth? Spring is coming; we shall soon be taking to our boats, rowing or canoeing, and the first day we do so doubtless we shall have blisters upon our hands, and the outer part of the skin, raised by the blister, will probably fall off and be lost altogether. The softer, underlying skin will be exposed, will be sensitive and uncomfortable for a while, but soon the cells behind the surface will assume a horny character, the cells underneath will grow and multiply, and presently the wound will be healed over. Did you ever stop to think that that means that there is a reserve power of growth in the skin all the time? always ready to act, to come forward, waiting