174 PRINCIPLES OF PHYSIOLOGY 



transmitted, and apparently with accumulat- 

 ing energy. So far as can be observed, all 

 fibres act alike. 



97. Nerves, composed of fibres, may be 

 divided, and if rejoined they will re-unite 

 and act as before. This has led to the experi- 

 ment of dividing two adjacent nerves, (a) 

 motor, and (b) sensory, and reuniting the 

 ends so that the upper end of a is joined to 

 the lower end of b, and vice versa ; they may 

 then unite and functions may be restored. 

 It is evident that if the upper end of a was 

 motor and conducted downwards, while the 

 lower end of b was sensory and conducted 

 upwards, the nervous impulse in one or the 

 other nerve must now conduct in the reverse 

 direction to what it did before division 

 But if a nerve is only a sensitive conductor, why 

 are the results of stimulation so various ? 

 It is due to the fact that the result depends 

 on the apparatus at the end of the nerve. If 

 the fibres end in muscle, there will be motion ; 

 if in a gland, secretion ; if in a blood vessel, 

 change of calibre ; if in a special part of the 

 brain, sensation or pain. The analogy to 



