ANIMAL MECHANICS. 



1 145 



We are now in a condition to calculate in foot tons, the 

 daily work done by the left ventricle of the human heart, which 

 lifts at each stroke 3 ounces through a height of 9.923 ft. Its 

 value is the following : — 

 Daily work of left ventricle 



m 3 x 9.9,3 x 75 x 6° x 24 _ ft tons 



16 x 2240 



1 find, on taking an average of the estimates of Bouillaud, 

 Laennec, Cruveilhier, Sommering, and Andral, that the right 

 ventricle has a thickness, which is to that of the left in the pro- 

 portion of 5 to 13 ; and as the cavities are of equal dimensions, 

 the thicknesses are proportional to their muscular powers ; in 

 order, therefore, to find the total work done by both ven- 

 tricles of the heart, we must add to the preceding result T 5 ^ths 

 of its amount, from which we obtain finally, 



Daily work of left ventricle, .... 89.706 ft. tons. 

 Daily work of right ventricle, . ... 34.502 



Total daily work of both ventricles, 1 24.208 ft tons. 

 The total work done by the heart is somewhat greater than 

 this estimate, for the auricles of the heart do some work, in 

 propelling the blood into the ventricles ; of which work 110 

 account has been taken in the preceding calculation. 



The average weight of the human heart is found from the 

 following Table : — 



Table XXV. — Table of Average Weight of Human Heart. 





Ounces. 



I . 



Meckel, , 





10.0 



2. 



Cruveilhier, 





7-5 



3- 



Bouillaud, 





8-375 



4- 







9-5 



5- 



Boyd [set. 30- 



-40]. • • 



0.41 



6. 



Boyd [set. 40- 



-50],. • 



10.56 



. 



Mean = 



9-39 oz. 



