WORK OF THE HEART 49 



force may be imitated by a feeble faradic current, which renders the 

 pulsations of the heart less frequent and more powerful, or it may be 

 still further exaggerated by a more powerful current, which arrests the 

 action of the heart. Phenomena are not wanting in the human subject 

 to verify these views. Causes operating through the nervous system 

 frequently produce palpitation and irregular action of the heart. 

 Cases are not uncommon in which palpitation habitually occurs after 

 a full meal. There are instances on record of death from arrest of the 

 heart's action as a consequence of fright, anger, grief or other severe 

 mental emotions. Syncope from these causes is by no means un- 

 common. In the latter instance, when the 'heart resumes its contrac- 

 tions, the nervous shock carried along the pneumogastrics is sufficient 

 only to arrest its action temporarily. When death takes place, the 

 shock is so great that the heart does not recover from its effects. 



Work of the Heart. The total work of the heart is easily com- 

 puted by multiplying the weight of the blood discharged at each con- 

 traction of the ventricles by the blood-pressure. Taking the weight of 

 blood discharged by both ventricles as about 4.5 ounces (130 grams) 

 and estimating the blood-pressure as equal to about five feet (1.5 

 meter), the result would be about 1.25 foot-pounds (0.175 kilogram- 

 meter) of work for each contraction of the heart. Assuming that the 

 heart beats seventy-two times in a minute, the total work for twenty- 

 four hours would be about 130,000 foot-pounds (18,000 kilogrammeters). 

 These figures are given as representing the probable work and are not 

 to be taken as anything more than approximate estimates. 



