STRUCTURE OF NERVE-FIBRES 73 



of silver produces a curious transversely striated appearance in the axis- 

 cylinder, but it is not known if this indicates a pre-existent structure. 

 Intermingled with the medullated fibres there may always, even in 

 the cerebro- spinal nerves, be found a certain number of pale fibres devoid 

 of the dark double contour which is characteristic of the presence of 

 a medullary sheath. There are the non-medullated fibres, also called, 

 after their discoverer, fibres ofBemak (fig. 86). They frequently branch, 

 which the medullated fibres never do except near their termination, 

 and they are beset with numerous nuclei which perhaps belong to a 

 delicate sheath. The sympathetic nerve is in many animals chiefly 

 made up of fibres of this nature, but in some animals, on the other 

 hand, most of the fibres of the sympathetic possess some small amount 

 of medullary sheath (fig. 87). 



jjer 



end, 



FIG. 88. SECTION OF THE SAPHENOUS NERVE (HUMAN), MADE AFTER BEING 

 STAINED IN OSMIC ACID AND SUBSEQUENTLY HARDENED IN ALCOHOL. 

 (Drawn as seen under a very low magnifying power.) 



ep, epineurium, or general sheath of the nerve, consisting of connective-tissue bundles of 



ends of the medullated nerve-fibres, which are embedded in the connective tissue within 

 the fnniculns (endoneurium). The fat-cells and the nerve-fibres are darkly stained by the 

 __ osmic acid, but the connective tissue of the nerve is only slightly stained. 



Structure of the nerve-trunks. In their course through the body 

 the nerve-fibres are gathered up into bundles or funiculi, and the 

 funiculi may again be united together to form the nerves which we 

 meet with in dissection. The connective tissue which unites the 



