Secreting Power of Animals. 266 



what these considerations are ; but he will admit that it is a con- 

 sideration of weight respecting the statement he here makes 

 that the effect of the stimulus applied to the brain and spinal 

 marrow on the heart, was precisely the same, whether the 

 blood had been wholly evacuated or not. He is not himself an 

 experimenter ; and here, as in some other instances, experiences 

 the disadvantage which often attends reasoning from the expe- 

 riments of others. All the circumstances of an experiment are 

 seldom related, the experimenter chiefly noting those which 

 affect his own views on the subject, and thus others, who reason 

 from them with other views, are often misled. To say that the 

 nervous influence in one set of muscles, can increase and impair 

 the excitability of the muscular fibre ; and yet, that in another 

 set this excitability depends wholly on the irritable nature of 

 that fibre itself, either supposes that there are two kinds of 

 muscular excitability, wholly differing in their nature, or im- 

 plies a contradiction. The nervous influence, however inde- 

 pendent the power of the muscular fibre, may call it into action 

 or it may so affect its organization as to impair its power ; but 

 how it can bestow a greater or less degree of what is derived 

 from a different source, it would be difficult to understand, and 

 Haller, in the passages quoted from his works by Dr. Alison, in 

 the 108th page, has been justly regarded as forced into contra- 

 dictions by the strength of his opponent's arguments, who called 

 upon him to say, why the heart is supplied with nerves, if its 

 excitability be wholly independent of the nervous system. Thus 

 it appears, that Dr. Alison has not only adduced no proof of the 

 opinion above stated, but that unless we admit of two kinds of 

 muscular excitability, for which I believe nobody will contend, 

 it is incompatible with opinions, the truth of which he admits. 



With regard to the other opinion of Dr. Alison, relating to 

 this part of the subject, — he observes in the 112th page, " 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 find- 

 ing, it stopped in his experiments by crushing that organ." Let 



