Secreting Power of Animals. 263 



its excitability is soon exhausted ; and that those muscles, over 

 which the will has no power, are notwithstanding supplied with 

 nerves. It occurred to me, that this question could only be 

 determined by some experiment, which should ascertain whether 

 the permanence of the excitability of muscles is proportioned to 

 the nervous influence they receive, or whether this influence 

 tends, like other stimuli to exhaust it; for if it be proved that 

 the permanency of the excitability is unimpaired by cutting off all 

 fresh supply of nervous influence, and that the nervous influence 

 exhausts this quality precisely as other stimuli do, a doubt, I 

 conceive, cannot remain respecting its dependance on tlie 

 mechanism of the muscular fibre itself. The 32d experiment 

 related in the above Inquiry, appears to answer these questions 

 in the affirmative, and therefore to prove the independent power 

 of that fibre. 



I am here called upon to notice an opinion on this subject, 

 which, I believe to be altogether new,' advanced by Dr. Alison in 

 an able and ingenious paper in the last number of the Quarterly 

 Journal, entitled Observations on the Theory which ascribes Se- 

 cretion to the Agency of Nerves. While he admits the foregoing 

 conclusion respecting the muscles of voluntary motion, he con- 

 ceives, that in the muscles of involuntary motion, the nervous 

 influence produces an " alteration in the vital power or tendency 

 to contraction." A few observations on this, and another 

 opinion of Dr. Alison relating to the same part of the subject, 

 namely, that the arguments I have used against the opinion of 

 M. le Gallois, that the power of the heart depends on the spinal 

 marrow, are equally strong against the dependance of the secret- 

 ing power on the nervous influence, will prepare us for consider- 

 ing the question which forms the principal subject of this paper. 



Dr. Alison, I have just had occasion to observe, admits it to 

 be proved, with respect to the muscles of voluntary motion, that 

 stimuli applied to the brain and spinal marrow excite them 

 merely by calling into action a power, which exists in the muscle 

 itself; but as it is found also, that stimuli applied to the same 

 origans produce the same effects in the muscles of involuntary 

 motion, there is surely the strongest proof that analogy, a princi- 



