562 CIRCULATION OF BLOOD AND LYMPH. 



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 15 cm. Hg. and on the right side against a 

 pressure of, say, 6 cm. Hg. The work done may be calculated from 

 the general formula W = FS that is to say, the work W is equal to 

 the product of the force F into S, the space or distance through 

 which the force acts. If the left ventricle empties 100 c.c. of blood 

 at each systole into the aorta, then, since the diameter of the aorta 

 is, say, 3 cm., there is forced out of the ventricle a column of blood 

 about 14 cm. long with a cross area of 7 sq. cm. This column is 

 driven out of the ventricle against a pressure or resistance equiva- 

 lent to the weight of a column of mercury 15 cm. high, or, counting 

 the specific gravity of blood as 1.06, a column of blood 192 cm. high 



"I Q A \ 



(15 X ^gl This is equivalent to saying that at each systole the 



left ventricle lifts a column of blood 192 cm. long and with a cross 

 area of 7 sq. cm. to a height of 14 cm. A column of blood 192 cm. 

 high with a cross area of 7 sq. cm. weighs 1425 gm. (192X7 X 1.06). 

 To move this weight through a distance of 14 cm. means the per- 

 formance of 19,950 gm. cm. of work (1425X14). In addition to 

 this work which represents the overcoming of a resistance there is 

 the further work represented by the velocity communicated to the 

 blood discharged from the ventricle. The kinetic energy of this 

 moving massfriay be calculated from the formula: 



Substituting for m its value of ?, in which p represents the weight 

 and g the acceleration of gravity (p mg, hence m = -), then 

 E = ^- in which p is equal to 106 gm. and v to 50 cm., the average 



1 Ofi V ^fP 



velocity of the blood in the aorta. Q81 ^ 2 = 13 ^ && cm - ^ 

 work. The total work done by the left ventricle, therefore, at each 

 systole is equal to 20,085 gm. cm. A similar calculation will give 

 the work done by the right ventricle. 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 



Vierordt 180 



Fick 50-73 



Howell and Donaldson 75-90 



Hoorweg 47 



Zuntz 60 



Tigerstedt 50-100 



Plumier 70 



Loewy and v. Schrotter 55 



Krogh and Lindhard 39-103 



for weight of 72 kgms. 



K t( (I K t( 



65 



60-65 kgms. 



