180 THE MOTION OF THE BLOOD. 



The heart, however, of frogs, for instance, contracts and relaxes 

 alternately, for a length of time, when out of the body and des- 

 titute of blood. 



Sir B. Brodie divided the great vessels in rabbits, and found the 

 action of the heart " apparently unaltered, for at least two minutes 

 after that viscus and the great blood-vessels were empty of 

 blood." s But the quantity of blood greatly influences the action 

 of the heart. 



" Since a supply of nerves and blood is requisite to the action 

 of the voluntary muscles, it has been enquired whether these, 

 both or either, are requisite to the heart also. h 



" The great influence of the nerves over the heart, is demon- 

 strated by the size of the cardiac nerves, and by the great sym- 

 pathy between the heart and most functions, however different. 

 A convincing proof of this is, the momentary sympathy of the heart 

 during the most perfect health l with all the passions, and with 

 the primes vice in various disorders. 



" The great importance of the blood to the irritability of the 

 heart is evident from the great abundance of vessels in its mus- 

 cular substance. 



" Besides these powers of the heart, there is another which is 

 mechanical, dependent on structure, and contributing greatly, in 

 all probability, to sustain the circulation. For, when the blood 

 is expelled from the contracted cavities, a vacuum takes place, 

 into which, according to the common laws of derivation, the blood 

 from the venous trunks must rush, being prevented, by means of 

 the valves, from regurgitating." k 



e Dr. Cooke, A Treatise on Nervous Diseases, vol. i. p. 63. 



h " On this dispute consult v. c. R. Forsten, Question, select. Pkysiol. Lugd. 

 Bat. 1774. 4to. 



J. B. J. Behrends, Dissert, qua demonstratur Cor Nervis carere, Mogunt. 

 1792. 4to. 



And on the other side, J. Munniks, Observations varies. Groning. 1805. 4to. 



Lucae, Obs. circa Nervos Arterias adeuntes. Francof. 1810. p. 37. tab. ii." 



1 " And how much more so when the heart is diseased, is shown v. c. in Caleb 

 Hillier Parry's Inquiry into the Symptoms and Causes of the SYNCOPE ANGINOSA, 

 commonly called ANGINA PECTORIS. Bath, 1799. p. 114." 



k " Andr. Wilson, Inquiry into the moving Powers employed in the Circulation 

 of the Blood. Lond. 1784. 8vo. p. 35. sq. 



And at great length in J. Carson's Inquiry into the Causes of the Motion of tfte 

 Blood. Ibid. 1815. 8vo." Second edition, 1833, 



