214 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



Fig. 61. HISTOLOGY or NERVE (from Landois and Stirling. 1, Primi- 

 tive fibrillse. 2, Axis- cylinder. 3, Non-medullated fibres. In their 

 course are seen numerous nerve-corpuscles. 5, 6, Medullated fibres ; 

 c, primitive sheath, internal to which the medulla, b, is seen ; U, 

 nodes of Ranvier between the two a single nerve-corpuscle ; a, axis- 

 cylinder. 7, Eleven medullated fibres in cross-section, surrounded by 

 connective tissue ; axis-cylinders dark, surrounded by white areas re- 

 presenting medulla. 8, Medullated fibre at node of Ranvier ; medulla 

 not shown. I., Multipolar ganglion-cell from spinal cord ; z, process 

 passing into axis-cylinder ; y, branched process to right of this 

 ganglion-cell is a bipolar one. III., Bipolar ganglion-cell from sym- 

 pathetic of Frog, surrounded by sheath, m ;. n, o, the two processes. 



