SCIENCE SIFTINGS

New Zealand Tablet, 27 October 1921, Page 46

SCIENCE SIFTINGS

By "VOLT"

WHEN WE FEEL HOT. A certain amount of heat is essential ,to the carrying on of the usual functions of the body (says a medical contributor to Tit-Bits, London). These can be per formed efficiently only within a narrow range of temperature. Hence the danger to life, in many diseases, if the temperature rises above 104 or 105 degrees. A fall of temperature 10 to 12 degrees below normal is not nearly so dangerous. <, t When we are in good health our bodily heat remains at a level —98.9 —despite the efforts of a grilling sun, or a temperature below freezing-point. Thus it comes about that a man who lives in Lapland is no colder inside than a man who lives in Madras. How does this happen? On a boiling hot day you feel unbearably warm, and in an icy blizzard you seem to shiver in the very marrow of your bones. But the application of the impartial thermometer would tell you that the temperature of your blood remained unchanged in either case, and that your feelings gave you a totally unreliable impression of the true state of affairs. To parody Hamlet, "you're neither hot nor cold, but thinking makes you so." You feel hopelessly hot or in- ' tolerably cold as the case may be, but the thermometer, which, like Salem Scudder's camera, "cannot lie," speaks the scientific truth. The mercury has not budged by a fraction of a degree, up or down, in either case. It is something of a miracle that occurs. One of the many wonders of our bodies is the nervous mechanism that regulates the bodily temperature as surely as we regulate our own baths by turning on and off the hot or cold taps, or opening the waste-pipe, as circumstances require. This indispensable apparatus is situated in the brain, and operates largely without our control or knowledge. For short we can call it the heat centre. Our ordinary bodily heat is derived from the action of our muscles and the working of our glands. The friction of the blood on the walls of our arteries as it is pumped along by the heart is turned into heat. In the same way the movements of organs causing friction produce heat. The body also derives heat; from hot food or drink, and by its being conducted or radiated from the surrounding atmosphere. Hence the body derives from one source or another a very large supply of heat, and if this were "not removed from the body in some way, the mean temperature of the body would rise to such a degree that life could no longer be carried on. It is in these circumstances that the heat regulating centre gets to work. It works off the excess heat in various ways. Tims, when Ave are too hot, perspiration is poured out to such an extent that much of the* surplus heat is expended in converting the sweat into vapor. Much of it also is thrown off into the surrounding atmosphere if its temperature is below that of the body. Heat is lost also, in some circumstances, by taking cold food or drink. The evaporation of water through the lungs (actually visible in winter only) also gets rid of a good deal of heat. The heat centre regulates and controls to a nicety all these operations. On the other hand, when in very cold weather it is necessary to generate sufficient heat to replace what is lost, the heat centre adopts different tactics. ,The shivering we experience when too cold is an attempt on the part of the heat centre to produce involuntary muscular contractions in order to increase heat production. But besides . this visibly mechanical effect, the effect of cold, when not too extreme, is to cause an increase in all the vital processes of tissue change, so increasing the production of heat, and to put a keen edge on the appetite, so that the intake of heat-producing food, and the capacity to digest and absorb it, are greatly increased. It is this that enables the Eskimo to keep his blood and bones comfortably warm amid the rigors of his Polar fastnesses. In a word, the human heat centre is a model combination of. the intelligence and executive departments of the body always working harmoniously together.