72 ON THE MOTION OF THE BLOOD. 



the blood driven to the distance of at least live feet 

 from the carotid of an adult and robust man. * 



124. This wonderful, and, while life remains, con- 

 stant, strength of the heart, is universally allowed to 

 depend on its irritability, (41) in which it very far sur- 

 passes, especially as to duration, f (98) every other 

 muscular part. J 



That the pariet.es of the cavities are excited to con- 

 traction by the stimulus of the blood, is proved by the 

 experiment of Haller, who lengthened at pleasure the 

 motion of either side of the heart, by affording it 

 the stimulus of the blood for a longer period than the 

 other. (C) 



* The experiments of Hales, in which the blood was received into very long 

 glass tubes fixed to the arteries of living animals, and the length of its pro- 

 jection measured, are indeed beautiful, like every thing done by this philo- 

 sopher, who was by nature calculated for such enquiries. But if the force of 

 the heart is to be estimated in this way, we must take into account the 

 pressure of the column of blood contained in the tube and gravitating upon the 

 left ventricle. The result of Hales's calculations was, that the blood being 

 projected from the human carotid seven feet and a half, and the surface of the 

 left ventricle being fifteen square inches, a column of blood, weighing 51.5 Ibs. 

 was incumbent upon the ventricle, and overcome by its systole. Statical 

 Essays, vol. ii. p. 40. London. 1733. 8vo. 



t Thus, to say nothing of the phenomena so frequently observed in the cold- 

 blooded amphibia and fishes, I lately found the heart of the chick beat for 

 twelve hours, in an egg, on the fourth day of incubation. 



J Consult Fontana, who treats of this prerogative of the heart minutely m 

 his Ricerche sopra la Fisica animate, and limits it too much. Haller answered 

 him in the Literary Index of Gottingen. 



Haller on the motion of the heart from stimulus, Comment. Soc. Sclent. 

 Gottingens. Tom. i. 



G. E. Remus, Experimenta circa circulat. sanguin. institvta. Gotting. 

 1752. p. 14. 4to. 



