LECTURE II. ' 59 



mitted along the nervous chords, an evident 

 motion of the visible matter of those chords 

 should be induced. Electrical motions 

 take place along a wire without occasioning 

 any visible motion of the metal itself. 



Formerly, it was thought that the mo- 

 tions of the nerves that cause sensation, 

 were the effect of an impulse made on 

 their tangible extremities, which was pro^ 

 pagated along the chord to the brain. 

 , It seems to be an improvement in modern 

 physiology, to attribute sensation to an 

 action begun in the nervous fibrils, in con- 

 sequence of the stimulation which they suf- 

 fer from such impulses. This opinion is 

 contended for by Dr. Darwin, in his paper 

 on ocular Spectra, published in the Phi- 

 losophical Transactions ; and Sir Everard 

 Home has further shown, that the living 

 principle of nerves has an irritability be- 

 longing to it, resembling that of muscles, 

 and capable of causing a contraction in 

 them when they are divided. * 



* Croonian Lecture. 



