86 



THE ESSENTIALS OF HISTOLOGY. 



The axis-cijliiider, which runs along the middle of the nerve-fibre, 

 is a soft transparent thread which is continuous from end to end of 

 the nerve. 1 



FIG. 102. AXIS-CYLINDER, 



HIGHLY MAGNIFIED, SHOW- 

 ING THE FIBRILS COMPOS- 

 ING IT. (M. Schultze.) 



FIG. 103. SECTION ACROSS FIVE 

 NERVE-FIBRES. (Magnified 1000 

 diameters. ) 



The nerve was hardened in picric acid 

 and stained with picro-carmine. The 

 radial striation of the medullary 

 sheath is very apparent. In one 

 fibre the rays are broken by shrink- 

 age of the axis-cylinder. The fibrils 

 of the axis-cylinder appear tubular. 



FlG. 104. A SMALL BUNDLE OF 

 NERVE-FIBRES FROM THE 

 SYMPATHETIC NERVE. (Key 



and Retzius.) 



The bundle is composed of pale 

 nerve-fibres, with the exception 

 of the fibre m, m, which is in- 

 closed here and there by a thin 

 medullary sheath ; n. n, nuclei 

 of pale fibres. 



On account of the peculiar refractive power of the medullary sheath 

 it is difficult to see the axis-cylinder in the fresh nerve except at the 



1 According to Engelmaiin the axis-cylinder is not structurally continuous 

 across the nodes of Ranvier. 



