AN AMAZING MACHINE

Hawera Star, Volume XLVII, 24 September 1927, Page 11

AN AMAZING MACHINE

heart is an amazing machine; it is so wc.il adapted to its purpose and so capable of meeting the needs of the body in emergency t.writes Rrotessor A. V. Hill in one of an interesting series or articles dealing with nerves and muscles in the •‘Nation and Athenaeum”;. Its duty is a very vital one—like that or .tlv? “safety men” in mines—and if it goes on strike even lor a few moments 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 foodstuffs for fuel and materials for growth and repair, but especially to provide hem with oxygen. If the brain be deprived ot oxygen, even for a few seconds, it (or its owner, whichever way you like to look at it) passes into unconsciousness. The amount of blood circulating i.~ 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 'i.s nearly 500,000 gallons a year, about- 30,000,000 gallons iri 65 years, even in a man remaining continually at rest —not a bad output 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 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 pn 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 STORY OF THE HEART

thv.- mean output will probably lie twice as great, so that the heart in a year wdl do the work required to raise 200 gallons, that is about one ton, from sea-level to the top of Mount Everest, T'ne matter can be expressed in an even ni-ore fantastic way. The work done by the heart of a heal thv man would in live months be sufficient to lift it mean out of the gravitational field of . the earth into empty span? outside. The work done bv his heart in 65 years would be enough to lift his whole body right, awav from the earth. The movements of the heart are automatic. If we kill a frog and open up his clipst we can see bis heart beating away inside a sac called the pericardium. It we remove this .sac wo can get at the heart itstrif arid 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. We mav cut the heart completely out and connect it to a glass tube ‘tilled 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 proportions. If these .simple needs are met the little pump can go on working once a- second or so for clays. 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 hv a lever on a- smoked .surface. The heart ha.s an intrinsic rhythm of its own. Its nature is to beat and to heat continuously: it provides, so to I speak, its own stimulus and does not require one from outside.