558 CIRCULATION OF BLOOD AND LYMPH. 



by an artificial circulation. The ratio of the output varied with the 

 rate of beat; for a rate of 180 beats per minute it was equal to 

 0.00117 (-g-h-) of the body weight; for a rate of 120 beats per minute 

 it was equal to 0.0014 (TTS-). This ratio is therefore about one-half 

 of that proposed by Volkmann. Tigerstedt, from observations 

 upon rabbits, obtained a lower ratio still (0.00042); but from his 

 own results and those obtained by other workers he concludes* 

 that an average valuation for the volume of blood discharged by 

 each ventricle of the human heart is from 50 to 100 c.c. On this 

 basis one may make an approximate estimate of the work done 

 at each beat. Using Tigerstedt's figures, such results as the follow- 

 ing are obtained: On the left side the heart empties its 100 c.c. 

 against a pressure of 150 mms. Hg. (0.150 meter) and on the right 

 side against a pressure of, say, 60 mms. Hg. (0.06 meter). The 

 work done is calculated from the formula w=pr, in which p repre- 

 sents the weight of the mass thrown out and r the resistance or 

 mean aortic pressure. This latter factor must be multiplied by 

 13.6, the density of mercury, to reduce to a column of blood. 



Lett ventricle, 100 gms. X (0.150 X 13.6) = 204.0 grammeters. 

 Right " 100 " X (0.06 X 13.6) = 81.6 



285.6 grammeters. 



To this must be added the energy represented by the velocity 

 of the mass ejected into the aorta. Placing this velocity at 500 

 mms. (0.5 meter) for both aorta and pulmonary artery, the energy 

 represented in mechanical work is estimated from the formula ^ 

 in which p represents the weight of the mass moved, v the velocity 

 of its movement, and g the accelerating force of gravity. Applying 

 this formula we have for each ventricle 2 X X 9 . 8 ' 5 = 1 .28 grammeters, 

 or for both ventricles 2.56 grammeters, making a total of over 288 

 grammeters of work. That is, the mechanical work done at each 

 contraction of the heart is equal to that necessary to raise 288 gms. 

 a meter in height. The calculations made by different authors as 

 to the amount of blood discharged from each ventricle during 

 systole may be tabulated as follows: 



Thomas Young 45 gms. 



Volkmann 188 



Vierordt 180 



Fick 50-73 



Howell and Donaldson 75-90 



Hoorweg 47 



Zuntz 60 



Tigerstedt 50-100 



Plumier 70 



Loewy and v. Schrotter .... 55 



' for weight of 72 kgms. 



i ti a fi (i 



65 



60-65 kgms. 



Krogh and Lindhard 39-103 



* Tigerstedt, "Lehrbuch der Physiologie des Kreislaufes," p. 152, 1893. 



