72 



THE ESSENTIALS OF HISTOLOGY 



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

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

 the nerve. 



On account of the peculiar refractive power of the medullary sheath 



FIG. 85. AXIS- 

 CYLINDER, HIGHLY 

 MAGNIFIED, SHOW- 

 ING THE FIBRILS 

 COMPOSING IT. 



FIG. 86. PORTION OF THE 

 NETWORK OF FIBRES OF 

 REMAK FROM THE PNEUMO- 

 OASTRIC OF THE DOG. 



, nucleus; p, protoplasm sur- 

 rounding it ; 6, striatiou caused 

 by fibrils. 



H IG. 87. A SMALL BUNDLE OP 

 NERVE-FIBRES FROM THE 

 SYMPATHETIC NERVE. 



The bundle is composed of pale 

 nerve-fibres, \vith the exception 

 of the fibre m, m. which is en- 

 closed here and there by a thin 

 medullary sheath ; n, n, nuclei 

 of pale fibres. 



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

 nodes, where it may be observed stretching across the interruptions in 

 the medullary sheath, and it may also sometimes be seen projecting 

 from a broken end of a nerve-fibre. It is longitudinally striated, being 

 really made up of exceedingly fine fibrils (ultimate fibrils, fig. 85), 

 which are darkly stained by chloride of gold. Staining with nitrate 



