256 Wilson Philip on the 



us consider how far the cases are parallel. I say, that when M. he 

 Gallois destroyed the power of the heart, by crushing the spinal 

 marrow, he was not at liberty to ascribe this effect to that power 

 depending on the nervous system, because although it were inde- 

 pendent of this system it might still be influenced through it. 

 It was therefore necessary to observe the effects of other modes 

 of withdrawing the nervous influence from the heart. My argu- 

 ment turns on the circumstance, that although the power of the 

 heart may be destroyed by crushing the spinal marrow, it is not 

 at all impaired by dividing the nerves which convey its in- 

 influence. If it were equally destroyed by both, M. Le Gallois 

 inference I conceive, would be unavoidable. Now this is the 

 case with the secreting power : it is equally destroyed by both ; 

 and unless Dr. Alison can point out some way of withdrawing 

 the nervous influence from secreting surfaces without destroy- 

 ing their power, as has been done with respect to the heart, he 

 cannot surely regard the two cases as at all parallel. 



To the question whether the power of secretion depends on 

 the nervous influence, we are now prepared to give, what appears 

 to me a ready answer. The fact just stated, I conceive, affords 

 this answer. We have no means of withdrawing the nervous 

 influence from secreting surfaces without destroying their power. 

 All will admit, that the only idea we attach to cause and effect is, 

 that of two events, one of which constantly follows the other. It 

 is therefore incumbent on those who deny that the nervous 

 influence is essential to secretion, to shew why the usual mode 

 of reasoning is not to be considered conclusive in this as in 

 other cases. 



But conclusive as this mode of reasoning is, it is not the only 

 way of answering the question before us. When the nerves of 

 a secreting surface are divided, it loses it power, either in con- 

 sequence of its nervous influence being impaired, or from the 

 immediate effects of the injury occasioned by their division. We 

 have direct evidence against the latter opinion. If the injury, 

 done to the nerves, were the cause of the derangement, the 

 more the nerves are injured in the act of dividing them, the more 



