88 



THE ESSENTIALS OF HISTOLOGY. 



sympathetic nerves are largely made up of fibres of this nature, but, 

 on the other hand, many of the fibres of the sympathetic trunk possess 

 a thin medullary sheath (fig. 104). 



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

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



FIG. 106. PART OF A SECTION OF ONE OF THE FUNICULI OF THE SCIATIC NERVE OF MAN. 

 (Key and Retzius. ) (Magnified. ) 



P, perineurium consisting of a number of closely arranged lamella? ; En, processes from the 

 perineurium, passing into the interior of the funiculus, and becoming continuous with the 

 endoneurium, or delicate connective tissue between the nerve-fibres. The connective- 

 tissue fibrils of the endoneurium are seen cut across as tine points, often appearing to en- 

 sheath the nerve-fibres with a circle of minute dots (fibril-sheath of Key and Retzius). 

 Numerous nuclei of connective-tissue cells are embedded in the endoneurium ; v, section 

 of a blood-vessel. 



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

 meet with in dissection. The connective tissue which unites the 

 funiculi and invests the whole nerve, connecting it to neighbouring 



FIG. 107. NERVE - FUNICULUS 

 STAINED WITH NITRATE OF SIL- 

 VER, SHOWING THE OUTLINES OF 



EPITHELIOID-CELLS OF THE 



PERINEURIUM. (Ranvier.) 



The dark crosses on the nerve-fibres at 

 the nodes of Ranvier are due to the 

 staining of the axis-cylinder and of 

 a band of intercellular substance 

 which encircles the axis-cylinder at 

 the node (constricting band of Ran- 

 vier). 



parts and conveying to it blood-vessels, lymphatics, and even nerve- 

 fibres destined for its coats, is termed the epineurium (fig. 105, ep). 

 That which ensheaths the funiculi is known as the perineurium (fig. 

 105, pe). It has a distinctly lamellar structure (fig. 106, p), the lamellae 



