200 PHYSIOLOGY OF MUSCLES AND NKUY1-S. 



regard -d a- composed of many particles arranged one 

 behind the other, each of which is retained in a defi- 

 nite position by its own forces and by the influence 

 of tin- neighbouring particles. Whatever acts as an 

 irritant on the nerves must displace these particles 

 from this position, and must cause a disturbance, which 

 then propagates itself, owing to the fact that. a change 

 in the position of one particle causes a disturbance in 

 the equilibrium of the adjacent particles, in consequence 

 of which the latter are set in motion. ^Negative Yaria- 

 tion must lie regarded as a result of this movement of 

 the nerve-particles, in that the electrically acting parts 

 are arranged in different order by the movement, and 

 therefore must exercise a different external influence. 

 Pmt just as thi< change in the portion of the nerve- 

 part ides is able to set the needle of a mult iplier, if it 

 i- properly connected with the nerve, in motion, so the 

 electric process originating in the nerve must act on 

 the imiM-le, if the latter is sensitive to electric varia- 

 tions. This was the assumption from which we started, 

 and which, after the above explanaf ions, will be regarded 

 as thoroughly trustworthy. To enter further into the 

 details of the activity of nerves and muscles, and to 

 substitute more definite conceptions for such as are at 

 present often indefinite, is impossible in the present 

 :-tate of knowledge. 



