DIVISION OF NERVE FIBRES. 



163 



whilst the axis cylinders diminish, it is obvious that the sheaths 

 must augment in thickness. This holds in particular for the 

 medullary sheath, the thickness of which is proportionately 



Pis. 23. 



Fig. 23. Medullated nerve fibre, from the electric organ of the Tor- 

 pedo, at the point of division, presenting a very thick sheath of 

 Schwann. a, trunk fibre ; 6, sheath ; c, nucleus of the sheath ; d, point 

 of divi&ion ; e, branches. After R. Wagner. 



much greater when the axis cylinder is thin than when it is 

 thick. Instead of the dichotomous division, three, four, or 

 more, even up to five and twenty branches may suddenly arise 



