144 NEEVE FORCE. CHAP. XI. §. III. 



SO arranged as to inclose the needle. The sciatic 

 nerve being laid bare, a plate of glass was placed 

 beneath it, and thus the nerve was elevated above 

 the surrounding muscles; it was then brought 

 beneath the magnetic needle, and kept in that 

 position, being supported upon a stool about a 

 quarter of an inch below it. The nerve was placed 

 in various positions with regard to the needle, some- 

 times parallel, at other times transversely or ob- 

 liquely to it. The needle being perfectly steady, the 

 muscles of the leg were made to contract, as in the 

 previous experiments; but, in whatever manner the 

 experiment was arranged, there was no indication of 

 any action upon the needle. Whenever any motion 

 of the needle occurred, it was evidently due to the 

 motion of the atmosphere produced by a too great 

 motion of the limb. I may also observe, that, as the 

 experiment was performed near a window, it was 

 necessary to guard against the heating effects of the 

 sun's rays upon the air within the tube. To the 

 importance of attending to this latter circumstance 

 in these experiments I have already alluded. 



Can we magnetise a needle ? Thick and thin needles 

 about three quarters of an inch long, and free from 

 magnetism, were inserted either transversely or longi- 

 tudinally in the nerve, and the muscles then made to 

 contract powerfully, and for some time by means of 

 an electric current from two of Grove's cells. In 

 these experiments there was no distinct evidence of 



