AN AMAZING MACHINE.

Hauraki Plains Gazette, Volume XXXVIII, Issue 5184, 28 September 1927, Page 4

AN AMAZING MACHINE.

STORY OF THE HEART. The he,art is an amazing machine; it is so well adapted to its purpose and so capable 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 Athanaeum.”) Its duty is a. very vital one—like that of the “ safety men’ in mines—and if it goes l on strike even for a few monnnts its owner dies. Its job is to pump blood round the body. All the vital organs of the body need a continuous' stream of blood, in order to supply them with foodstults for fuel and materials for growth and repair, but especially to provide* them with oxygen. If the brain be deprived of oxygen, even for a few; seconds, it (or its owner, whichever way you like t,o 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 the total amount of blood in the body. This is nearly 500,000 gallons a year, about 30,000,000 gallons in sixty-five years, even in a man remaining continuously at rest —not a bad output for a self-regulating pumi) weighing less than a. pound. During muscular effort its output, is greater, under of severe exertion perhaps eight times as great as during regt. During this pumping process the hejart does a great deal of work. The pressure in the arteries is high, and equal approximately to that of about five or six feet of water. Thus in a year the heart of a resting man does work equivalent to raising nearly 500,000 gallons six feet upwards, or to raising 100 gallons to the top of Mount Everest. In a man doing average work the mean output will probably be twicoj as great, so that his heart in a year will do the work required to raise 200 gallons, that is, about one ton, from sea-level to the top of’ Mount Everest, The matter can be expressed in an ev-ejn more fantastic way. The work done by the heart of a healthy man would in five months be sufficient to lift it out, of tho gravitational field of the earth into empty space outside. The work done by his heart in 65 years would be enough to lift his whole body right away from the earth. The movements of the heart are, automatic. If we kill a frog and open up his chest we can see: his heart beating away inside a sac called the pericarium. If we remove this sac we can get at the heart itself and tie a thread on to its tip and connect the thread to a light lever, and so write a record of its movements on a smoked drum. We may go further. Wc may cut 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 ine<t 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 bath each strip in the salt water, and it will go on contracting automatically for long periods and writing its records by a lever on a smoked surface. The heart has an intrinsic rhythm of its own. Its nature is to beat and to beat, continuously ; it provides, so to speak, its own stimulus, and does not require one from outside*.