to the Agenci/ of the Netves. 1 13 



in the stomach ? The same supposition, of diminution, or de- 

 struction of sensation, and of the substitution of sensations of a 

 different kind, may explain the want of any increased secretion 

 from the action of the arsenic in Mr. Brodie's experiments. 



When) therefore, Mr. Brodie concludes, from these experi- 

 ments, that " the suppression of the secretions was to be attri- 

 " butedto the division of the nerves," and " that the secretions 

 " of the stomach and intestines are very much under the con- 

 '• trol of the nervous system," his inferences must command 

 general assent. But when he hazards the farther conclusion, 

 that " the secretion was prevented in consequence of the ner- 

 " vous influence having been interrupted," I would beg to ask, 

 what is the precise meaning attached in this instance to the 

 term nervous influence, and what proof there is of its having 

 been interrupted ? 



If it be meant merely, that the nerves are prevented from 

 performing their accustomed actions, in regard to secretion, 

 we may object to the expression, because it seems to imply, 

 that these actions are constant and essential to the effect, whereas 

 it is very possible that they may be only occasional, and may 

 modify, without assisting, the secreting actions. 



If it be meant that some influence derived from the nervous 

 system really essential to secretion is cut off" by the operation, 

 we may object to the conclusion, because the fact may be equally 

 well explained by supposing the lesion of the nerves to commu- 

 nicate a noxious influence to the secreting organ, without inter- 

 cepting a salutary one. 



The other arguments in favour of the dependance of secretion 

 on the nervous system, chiefly insisted on by the authors for- 

 merly mentioned, are these ; 



1 . Changes in the blood, somewhat similar to those produced 

 by secretion, particularly the coagulation of the albuminous 

 and the separation of the saline part, may be produced by 

 galvanism. 



2. Galvanism is excited by the contact of the nerve and 

 muscle of an animal recently dead, and a galvanic pile may be 

 formed of alternate layers of nervous and muscular substance. 



Vol. IX. I 



