166 THE CIRCULATION 



29. Activity of the Heart. The average number of heart- 

 ^eats during a lifetime may be considered as at the rate of 

 seventy-two per minute, although this estimate is somewhat 

 low, for during several years of early life the rate is above one 

 hundred a minute. In one hour, then, the heart pulsates four 

 thousand times ; in a day, one hundred thousand times ; and 

 in a year, nearly thirty-eight million times. If we compute 

 the -number during a lifetime forty years being the present 

 average longevity of civilized mankind we obtain as the vast 

 aggregate, fifteen hundred millions of pulsations. (Read Note 10.) 



pallor, loss of sensation, and trembling of the limbs and loss of power 

 over the muscles ; the breathing and pulse go on imperfectly or stop. 

 The first thing to do is to place the head low, thus favoring the supply of 

 blood to the brain ; the very act of falling is often sufficient to restore 

 consciousness. Water may be sprinkled on the face, hartshorn held to 

 the nose, or mustard over the heart. Pure air is a great restorative ; 

 allow a current of fresh air to flow over the face, and loosen any tight 

 bands that may confine the chest." Dr. J. Knight (in part). 



9. The Heart a Vital Machine. " The heart is a machine. It is an 

 organ constructed >of muscular chambers and communicating passages, 

 and supplied with mechanical contrivances, adapted to guide the stream 

 of blood passing through it, and to prevent a reflux in the backward 

 direction. Does not this take away wonderfully from the character of 

 fanciful mystery with which poets and sentimentalists have invested it ? 

 The heart that we have always heard of as the centre of the affections, 

 the home of sensibility, the dwelling-place of courage, of faith, of hope, 

 and all the rest of the virtues, is after all, nothing but an organ to serve 

 for the impulsion of the blood a mere force-pump, a machine. Does 

 not this bring down our ideas, and show that no poetical mystery can 

 escape the searching investigation of the anatomist ? Not at all. 



"For this machine that we carry about with us in our breasts is alive. 

 There, at its post, at the central point of the circulation, with the soft 

 lobes of the lungs folded round it like a curtain, it contracts and relaxes, 

 and relaxes and contracts, with a steady and unremitting industry that 

 by itself is something worthy of our admiration. No other muscle in the 

 body can do this. By some incomprehensible vitality of its own, it keeps 

 up its rhythmical contractions without the aid of our will and even with- 

 out our knowledge. While you are asleep and while you are awake, from 

 the first moment of your birth, even from before your birth, up to the 

 present time, it has never for one moment stopped or flagged in its move- 

 ments, for if it were to do so death would be the result." Dr. J. C. 

 Dalton. 



Average numbei of heart-beats ? In oue hour ? Year ? Lifetime T 



