490 CIRCULATION OF BLOOD AND LYMPH. 



(Volkmann, Vierordt) attempted to arrive at a determination of the 

 normal output of the ventricles by calculations based upon the 

 velocity of the blood in the carotid and the width of the stream 

 bed. From observations on many animals they arrived at the 

 generalization that at each systole the amount of blood ejected 

 from the ventricles is equal to about 4^ of the body weight. For 

 a man weighing, say, 72 kilograms (158 lbs.) this ratio would give 

 an output for each systole of 180 gms. (6 ozs.). More recent 

 observers, however, have found this estimate too high. Howell 

 and Donaldson* measured the output directly for the heart of the 

 dog, making use of a heart isolated from the body and kept beating 

 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 (sis) of the body weight; for a rate of 120 beats per minute 

 it was equal to 0.0014 (totf)- 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 f 

 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. 



Left 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 y 9 g 5 = 1.28 grammeters, 

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



* Howell and Donaldson, " Philosophical Transactions," Royal Soc, Lon- 

 don, 1884. 



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



