INFLUENCE OF THE NEEVOUS SYSTEM OX THE HEAKT. 229 



thorities held the opinion that the cause of the irritability of 

 the organ was derived from the nerves. One of the most 

 distinguished advocates of this opinion was Legallois. This 

 observer arrested the action of the heart of the rabbit by sud- 

 denly destroying the spinal cord, from which he drew the 

 conclusion that the heart derived its contractile power from 

 the cerebro-spinal system. 1 The experiments which we have 

 already cited, showing the continuance of the heart's action 

 after excision, disprove this so completely, that it was not 

 thought worth while to discuss this view while treating of 

 the cause of its rhythmical contraction. The same may be 

 said with regard to the experiments of Brachet, in which he 

 endeavored to prove that the contractility of the heart is de- 

 rived from the cardiac plexus of the sympathetic system of 

 nerves. The fact that the heart does not depend for its con- 

 tractility upon external nervous influence may be regarded 

 as long since definitely settled ; but within a few years the 

 discovery in its substance of ganglia belonging to the sympa- 

 thetic system has revived, to some extent, the view that its 

 irritability is derived from nerves. 



It is not necessary to follow out all the experiments which 

 combine to demonstrate the incorrectness of this view. Ber- 

 nard, by a series of admirably conceived experiments upon 

 the effects of the woorara poison, has succeeded in demon- 

 strating the distinction between muscular and nervous irri- 

 tability. 2 In an animal killed with this remarkable poison, 

 the functions of the motor nerves are entirely abolished ; so 

 that galvanization, or other irritation, does not produce the 

 slightest effect. Yet the muscles retain their irritability, and 

 if artificial respiration be kept up, the circulation will con- 

 tinue for a long time. The heart, by this means, seems to 

 be isolated from the nervous system as completely as if it were 

 excised; and galvanization of the pneumogastric nerves in 



1 LEGALLOIS, (Euvres, tome i., p. 9*7. 



BERNARD, Lemons sur Ics Effets des Substances Toxiques et Medicamenteuses, 

 Paris, 1857. 



