112 Alison o)t the Theory ascribing Secretion 



mentioned, althongh obviously susceptible of explanation in thia 

 manner, are not sufficient to justify this conclusion. Without 

 supposing the secretions of the stomach to depend upon any 

 thing derived from the nervous system, we may suppose them 

 liable to change, or even to total annihilation, from certain le- 

 sions of that system. And although the kind of lesion wliich 

 produces this efl'ect on these secreting organs be different from 

 that which stops the movements of the heart ; yet as we are ig- 

 norant of the manner in which any lesion of the nervous system 

 affects muscular action or secretion, we are not more entitled 

 to conclude, that the secretions of the stomach depend on its 

 nerves, from finding them stopped by the division of these 

 nerves, than Le Gallois was, to conclude that the action of the 

 heart depends on the spinal marrow, from finding it stopped, in 

 his experiments, by crushing that organ. 



If the conclusion in question does not necessarily follow from 

 the experiments, we are justified in refusing our assent to it, 

 without pointing out any other manner in which the results of 

 these experiments may be explained. Different theories may 

 perhaps be formed for this purpose, but there is one consi- 

 deration that appears to me particularly deserving of notice. 

 The eighth pair of nerves are generally regarded as those 

 which are most concerned in the sensations of the stomach. 

 Now it is pretty certain that different secretions are very de- 

 pendant on certain sensations. No one can doubt of the 

 effect of the sensation of grateful food in the mouth, upon 

 the action of the salivary glands. I think it cannot be doubt- 

 ed, that dividing the nerves of the tongue and palates, 

 and so paralysing the organ of taste, would greatly dimi- 

 nish the flow of saliva during the mastication of food ; but 

 we know that the salivary glands cannot derive any energy from 

 these nerves, because they are supplied by other nerves. By 

 dividing the eighth pair of nerves after an animal has taken food ; 

 the natural sensations which accompany and succeed the reced- 

 tion of food into the stomach are prevented from taking place, 

 and the painful sensations of dyspnoea and nausea are produced, 

 and may not this be sufficient to explain the failure of secretion 



