SCIENCE SIFTINGS

New Zealand Tablet, Volume XLVIII, Issue 45, 15 November 1923, Page 54

SCIENCE SIFTINGS

sacs a-;', ~r-3f~ By VOLT" IT- ■■ = iii-a fa.v a..!*—. . i ■ n. j

Why Bread Has a Crust. Why does a loaf of bread have a crust? When a mass of dough is baked in the oven the water in it turns to steam at 212 degrees Fahrenheit. After this it cannot get any hotter, but the outside of the loaf is not limited by the presence of water, and both the pan and the air in the oven get much hotter. This converts - the starch in the outer layer of dough into sugar, part of which is burnt to caramel. The latter gives the outside of the loaf its crust, and makes it quite different in appearance and flavor from the crumb inside. Where It Hurts Most. Drawing a tooth is said to be the extreme of human pain. The rupture of the branching denial nerve causes such agony as no human being could stand for more than two seconds at a time. It is a curious fact that while a deep and dangerous wound often causes nothing but a dull ache, a slight surface injury is often intensely painful. A splinter driven into the quick of the nail causes the most exquisite agony. The tips of the fingers and the tip of the tongue are the most sensitive portions of, the human frame. The cornea, of the eye is also extremely sensitive. Most of us know the misery caused by getting a speck of cinder or something hard under the eyelid. A burn on the hand is much more painful than one on the back. The hand is a mass of nerves, and a man shot through the palm of the hand will usually collapse as completely as if shot through the body. Of ailments, the three which cause most pain are toothache, earache, - and neuralgia of the fifth nerve. The latter has been known to drive the sufferer quite mad for the time being. 4 Can Plants See? We know that plants are sensitive to light and dark. Many of them move during the day in order to turn the faces of their flowers always to the sun. Others open only when the daylight is dying, and when the moths on whom they rely to carry their pollen are abroad. Climbing plants, such as sweet-peas, seem to fling their tendrils in an almost uncanny way in the direction of anything that will serve as a support, A scientist engaged recently in taking photographs of leaves through the microscops was surprised to discover that some of them showed hundreds of little round patches, each of which reflected the image of some object, just as do the facets of the compound eye of an insect. Closer examination proved that each of these patches consisted of a cell whose rounded outer wall formed a perfect lens. Each cell was, in fact, a perfect eye. It was tempting to jump to the conclusion that plants could see. Actually they do not. The “eyes” serve quite a different purpose. A plant lives by the process of bottling up sunshine, whose action produces chemical changes within the leaves and the stem. The leaves focus the sun’s rays and enable the work to be done effectively. Plants are sensitive to light simply because when the sun shines the chemical changes within them go on with increased speed. Climbing plants find supports by groping. The tendrils follow the sun, and as they move round they touch and hold on to anything suitable that lies in their path. Be filled with hope and give the world the impression of your own mind, and material wealth will not count so much.