32 THE STRUCTURE OF 



lated nerve fibres speedily undergo chanoe. They then not 

 unfrequently assume an irregular or varicose appearance — • 



PiO. 4.— Small Branch of a Muscular Nerve of the Frog, near its Termination, 

 showing divisions of the Fibres. Magnified 350 diameters (KoUiker). <f, into two ; 

 h, into three. 



principally owing to changes in the white medullary 

 sheath (fig. 3, h, h). 



The use of this white investin<]C substance is not known. 



