226 THE HUMAN BOLT. 



millimeters (8 inches) high. The left ventricle therefore 

 drives out, seventy times in a minute, 180 grams (6.3 

 ounces) of blood against this pressure. Since the specific 

 gravity of mercury is 12.5 and that of blood may for prac- 

 tical purposes be taken as 1, the work of each stroke of the 

 ventricle is equivalent to raising 180 grams (6.3 ounces) 

 of blood 200 X 12.5 = 2500 millim. (8.2 feet)- or one, 

 gram 450 meters (one ounce 51.66 feet); or one kilo- 

 gram 0.45 meters (one Ib. 3.23 feet). Work is measured 

 by the amount of energy needed to raise a definite weight 

 a given distance against gravity at the earth's surface, the 

 unit, called a kilogr ammeter, being either that necessary to* 

 raise one kilogram one meter, or, called & foot-pound, that 

 necessary to raise one pound one foot. Expressed thus the 

 work of the left ventricle in one minute, when the heart'* 

 rate is seventy strokes in that time, is 0.45 X 70 31.50 

 kilogrammeters (3.23x70 = 226.1 foot-pounds); in one 

 hour it is 31.50 X 60 = 1890 kilogrammeters (226.1 X 60 

 = 13,566 footpounds); and in twenty-four hours 1890 x 24 

 = 45,360 kilogrammeters (325,584 foot-pounds). The pres- 

 sure in the pulmonary artery against which the right ventricle 

 works is about -J of that in the aorta; hence thie ventricle 

 in twenty-four hours will do one third as much work as the 

 left, or 15,120 kilogrammeters (108,528 foot pounds) and 

 adding this to the amount done by the left, we get as the 

 total work of the ventricles in a day the immense amount 

 of 60,480 kilogrammeters (434,112 foot-pounds). If a man 

 weighing 75 kilograms (165 ibs.) climbed up a mountain 

 806 meters (2644 feet) high his skeletal muscles would 

 probably be greatly fatigued at the end of the ascent, and 

 yet in lifting his Body that height they would only have 

 performed the amount of work that the ventricles of the 

 heart do daily without fatigue. 



The Flow of the Blood Outside the Heart. The blood 

 leaves the heart intermittently and not in a regular stream, 

 a quantity being forced out at each systole of the ventri- 

 cles: before it reaches the capillaries, however, this rhythmic 

 movement is transformed into a steady flow as may readily 

 be seen by examining under the microscope thin trans- 



