32 THE STRUCTURE OF 



lated nerve fibres speedily undergo change. They then not 

 unfrequently assume an irregular or varicose appearance 



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

 showing divisions of the Fibres. Magnified 350 diameters (Kolliker). a, into two ; 

 b, into three. 



principally owing to changes in the white medullary 

 sheath (fig. 3, 6, b). 



The use of this white investing substance is not known 



