THE HEART

Evening Star, Issue 19666, 20 September 1927, Page 7

THE HEART

SOME STAGGERING FACTS

The heart is an amazing machine; it is so well adapted to its purpose and so capabje of meeting the needs of the body in emergency (writes Professor A. V. Hill in one of an interesting series of articles dealing with nerves and muscles, now appearing in the ‘Nation and Athemeum ’). Its duty is a very vital one—like that of the “safety men” in mines—and if if. goes on strike even for a few moments its owner dies. Its job is to oiimp blood round the body. All the vital organs of the body need a continuous stream of blood, in order to supply them with foodstuffs : for fuel and materials for growth and repair, but especially to provide them with oxygen. If the. brain be deprived of oxygen, oven for a few seconds, it (or its o'xpcr. whichever way you like to look at it) passes into unconsciousness. The amount of blood circulating is Fairly large; in a man at rest it may be about four litres a minute—nearly a gallon—about equal to {he total amount of blood in tbo body. This is nearly sflo,ooogal a year, about dO.OOO.OOOgaI in sixty-live years, oven in a man remaining continually at rest—not a bad mtpnt for a little self-regulating pump weighing less than a pound. During muscular effort its output is greater—under conditions of severe exertion perhaps eight times as great as during rest. During this pumping process the heart docs a great deni of work. The pressure in the arteries is high, and equal approximately to that of about sft or 6ft of water. Thus in a year the heart of a resting man docs work equivalent to Pearly 500,000 gal 6ft upwards, or to raising lOOgal to the top of Mount Everest. In a man doing average work the mean output will probably be twice as great, so that his heart in a year will do the work required to raise 200 gal—that is, about one ton—from sea level to the top of Mount Everest. The matter can he expressed in an even more fantastic way. i'.,Tbo work done bv the heart of a healthy.man would in five months suffice to lift it clean out of the gravitations* field of the earth into empty space outside. The work done hy his heart in sixtv-five years would be enough to lift his whole body right awav from the earth. The movements nf the heart are automatic. If we kill a frog and open his chest we can see bisheart beating away inside a sac called the pericardium. If we remove this «ac we can get at the heart itself and lie a thread on to its tip and connect the thread to a light lover, and so write a record of its movements on a smoked drum. We may go further. We may nut the heart completely out and connect It to a glass tube filled with salt solution, and it will go on working and pumping the salt water for hours and hours. It requires a little oxygen, and it demands that the salt water shall contain, salts in the right concentrations and the right proportions. _ If these simple needs are met the little pump can go on working once a second or so for days. ‘We may go further still. We may cut the heart up into strips and bathe each strip in the salt water, and ?t will go on contracting automatically for long periods, and writing its records hy a lever on a smoked surface. . The heart has an intrinsic rhythm of its own. _ Its nature is tc beat and to beat_ continuously; it provides, so to speak, its own stimulus, and does not require one from outside.