364 PHILOSOPHICAL TRANSACTIONS. [aNNO l/SS. 



out any communication of motion between the stimulus, that is, application pro- 

 ducing the motion, and the end of the nerve in which it is excited; therefore, on 

 any supposition, a stimulus is capable of exciting a motion, in a part at a dis- 

 tance, without any communication of motion; and it is therefore not necessary 

 that the nerves should be at all employed in the motions of the body excited by a 

 stimulus, as it can act at a distance without their intervening. Further, that the 

 nerves'are not employed in the motions excited by stimuli, is evident from this 

 experiment: take the heart out of a living animal, cut all the nerves off as close 

 as possible, lay it in nearly the heat of the body of the animal, it will continue 

 to contract for some time. As soon as it has ceased contracting, prick a fibre in 

 one of the ventricles; both ventricles, and all their fibres, will contract instantly, 

 though there be now no communication by the nerves, between many of the 

 contracting fibres, and the fibre stimulated. It might be suspected that the mo- 

 tion of the fibre stimulated might affect the others: in this case the contractions 

 would be progressive; but, on the contrary, the whole contract at once. 



I cannot help bringing another instance, where stimuli produce action in parts 

 at a distance, without any communication of motion by the nerves. When in- 

 fusion of cantharides is applied to the skin, as we say vulgarly, it is not applied 

 immediately to the skin; but in the first instance to the mucous and sebaceous 

 matter, which every where covers the scarf skin; under this lies the scarf skin, 

 which the infusion can hardly be conceived to come at; if it did, the scarf skin 

 we know is perfectly impenetrable to such a fluid; it can therefore never touch 

 the skin, in which it excites inflammation, and on which it therefore acts at a 

 distance, and excites motion, which no one can suspect to come through the 

 nerves: nor is there any motion through the mucus and scarf skin, of any other 

 kind than would arise if an infusion of any other insect had been applied, which 

 had no power of exciting inflammation. From what has been said we may con- 

 clude, that when a stimulus has been applied so as to excite motion in a distant 

 part, no motion whatever takes place in the nerves, or is communicated by them 

 from the part to which the stimulus is applied to the moving part. 



I need not draw youj5 attention to another proposition, viz. that when a sti- 

 mulus is applied to a distant part, so as to produce motion, it often happens, 

 that the stimulating matter is not carried by the blood-vessels, or otherwise, to 

 the moving part. This proposition has often been demonstrated, and is well 

 known. All the original power exerted by any of the moving parts consists in a 

 power of particles coming nearer to one another; for every muscle or fibre be- 

 comes shorter when it acts ; or in other wo^ds contracts ; and every other moving 

 part in like manner contracts when in action. It is true that there are many 

 contrivances to make the contraction have great effect in producing motion, 

 force being never spared for conveniency, as Mr. Hunter has I believe already 



