74 



stances connected with diseases. Vehe- 

 ment actions may occur in the tangible ex- 

 tremities of nerves, independent of im- 

 pulses, and occasion severe pain. This 

 seems to happen in the disease called 

 tic douloureux. Ordinarily, actions be- 

 ginning in the tangible extremities of 

 nerves, are regularly transmitted to the 

 brain ; but in cases of nervous pains, ac- 

 tions sometimes seem to begin in the 

 middle of nerves ; and it is probable, 

 that actions beginning in the sensorial 

 extremities of nerves may be productive 

 of illusory sensations, and excite falla- 

 cious ideas. 



If this theory of nervous actions could 

 be proved, the extent of our knowledge 

 \vould only lead to this conclusion, that 

 motions of a subtile substance, propagated 

 to and fro in the nervous fibrils, took 

 place in consequence of excitement by 



