260 THE LAWS OF ORGANIC 



CHAP. XII. 



The Causes which Influence the Action of the 

 Heart. 



CCLXXX. INHERE are probably few subjects 

 concerning which a greater diversity of opinion 

 exists, than regarding the cause of the contrac- 

 tions of the heart, and the precise manner in 

 which these are influenced by chemical and 

 mechanical changes. HALLER and his partisans 

 endeavoured to shew that the contractions are to 

 be ascribed to a vis insita independent of the 

 nervous system. LEGALLOIS concludes, that the 

 heart derives its powers from the whole of the 

 spinal cord : WILSON PHILIP has proved that 

 this organ can act when the brain is removed 

 and the medulla oblongata is destroyed, a fact I 

 have repeatedly ascertained. In Experiment V. 

 page 48-9, the heart was found contracting 70 

 times per minute in a rabbit that had been in- 

 flated for an hour, in which neither brain nor 

 spinal cord was present* 



CCLXXXI. In Chapter X. we gave a cursory 

 glance at the properties and office of the nervous 

 system, and, therefore, shall not occupy the pre- 

 sent pages in discussing the same point. The 

 irritability which has been supposed by HALLER 



