2 ON THE INFLUENCE 



tain how far the influence of the brain is neces- 

 sary to the action of the heart, I found that 

 in an animal in which the spinal chord had 

 been divided in the upper part of the neck, re- 

 spiration was immediately suspended, while the 

 heart still continued to contract circulating dark- 

 coloured blood, and that, in some instances, from 

 ten to fifteen minutes elapsed before the heart's 

 action had entirely ceased. I further found that 

 when the head was removed, the divided blood 

 vessels having been secured by a ligature, the cir- 

 culation still continued, apparently unaffected by 

 the entire separation of the brain. These experi- 

 ments confirmed the observations of Mr. Cruik- 

 shank* and M, Bichatf, that the brain is not 

 directly necessary to the action of the heart, and 

 that when the functions of the brain are destroyed, 

 the circulation ceases only in consequence of the 

 suspension of respiration. This led me to con- 

 clude, that, if respiration were produced arti- 

 ficially, the heart would continue to contract for 

 a still longer period of time after the removal of 

 the brain. The truth of this conclusion was 

 ascertained by the following experiment. 



EXPERIMENT I. 



I divided the spinal chord of a rabbit in the 

 space between the occiput and atlas, and having 

 made an opening into the trachea, fitted into it 



* Philosophical Transactions, 1795. 



t Recherches Physiologiques sur la Vie et la Mort. 



