SECT. XII. i. OF STIMULUS AND EXERTION. 67 



mufcular con traction, as above obferved, there ap- 

 pears no difference in the velocity or force of it at 

 irs commencement or at its termination ; from 

 whence we muft conclude that animal contraction 

 is governed by laws of its own, and not by thofe 

 of mechanics, chemiftry, magnetifm, or electri- 

 city. 



On thefe accounts I do not think the experiments 

 conclufive, which were lately publiihed by GaUani, 

 Volta, and others, to fhew a fiinilitude between the 

 fpirit of animation, which contracts the inulcular 

 fibres, and the electric fluid. Since the electric 

 fluid may act only as a more potent ftimukis exciting 

 the mufcular fibres into action, and not by fupply- 

 ing them with a new quantity of the fpirit of life. 

 Thus in a recent hemiplegia I have frequently ob- 

 ferved, when the patient yawned and ftretched 

 himfelf, that the paralytic limbs moved alfo, though 

 they were totally difobedient to the will. And 

 when he was electrified by parting fhocks from the 

 affected hand to the affected foot, a motion of the 

 paralytic limbs was alfo produced. Now as in the 

 act of yawning the mufcles of the paralytic limbs 

 were excited into action by the Itimulus of the irk- 

 fomenefs of a continued pofture, and not by any 

 additional quantity of the fpirit of life; fo we 

 may conclude, that the paffage of the electric fluid, 

 which produced a limilar effect, acted only as a fti- 

 mulus, and not by fupplyingany addition of fenfb- 

 rial power. 



If neverthelefs this theory fhould ever become 

 eftablifhed, a ftimulus muft be called an eductor of 

 vital ether ; which ftimulus may con lift of lenfati- 

 on or volition, as in the electric eel, as well as in 

 the appuites of external bodies ; rwd by drawing off 

 the charges of vital fluid may occalion the contrac- 

 tion or motions of the mufcular fibre s, and organs 

 of fenfe. 



a. 'The 



