On the Agency of Nerves. 275 



that the action of the heart, though independent of the spinal 

 marrow, may be altered or stopped by crushing that organ. 



Dr. Philip, however, maintains, in answer to this, that Le 

 Gallois's conclusion could not have been objected to, unless it 

 had been found that the heart is not affected by dividing the 

 nerves issuing from the spinal marrow. If the action of the 

 heart had been equally destroyed, both by crushing the spinal 

 marrow and by cutting the nerves, he says, ** Le Gallois's infer- 

 ence would have been unavoidable." 



This is the precise point at which it appears to me that Dr* 

 Philip has gone wrong. Le Gallois's opinion was disproved by 

 Dr. Philip's experiments, in which the action of the heart con- 

 tinued, notwithstanding the division of the nerves, and removal 

 of the brain and spinal marrow from the body ; but I main- 

 tain that it would not have been proved, although that operation 

 had stopped its action as effectually as crushing the spinal 

 marrow did. The heart's action we now know is independent 

 of the nervous system. Yet a certain injury of the nervous 

 system stops that action. Why might not another? What 

 reason can be given for supposing that a conclusion might have 

 been fairly deduced from the effect of one lesion of the nervous 

 system, which we have seen was unfairly deduced from that of 

 another ? If I understand the subject rightly, the effect which 

 crushing the spinal marrow had on the action of the heart, in Le 

 Gallois's experiments, was a fact ; but the conclusion, that the 

 living power of the heart depends upon, or is derived from, the 

 nervous system, involved a theory, which would not have been 

 confirmed, although fifty other injuries of the nervous system 

 had done the same thing ; and the very same theory is involved 

 in the answer which Dr. Philip has given to the argument 

 which I had advanced, in regard to secretion. 



When Dr. Philip calls on me, therefore, to point out some 

 way of withdrawing tfie nervous influence from secreting sur- 

 faces without destroying their power, I answer, first let it be 

 made clear that there is such an existence in nature as this 

 nervous influence, and then I will admit the obligation. The 

 simple fact is, that the secretion is changed when the nerves of 



