74 



THE ESSENTIALS OF HISTOLOGY 



funiculi and invests the whole nerve, connecting it to neighbouring 

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

 fibres destined for its coats, is termed the epineurium (fig. 88, ep). 

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

 88, per). It has a distinctly lamellar structure (fig. 89, p), the lamellae 



JET. 



FIG. 89. PART OF A SECTION OF ONE OF THE FUNICULI OF THE SCIATIC NERVE 

 OF MAN. (Magnified.) 



P, perineurium, consisting of a number of c'ose'y arranged lamellae. En, processes from the 

 perineurium, passing into the interior of the funicu'us, and becoming continuous with the 

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

 tissue fibri s of the endoneurium are seen cut across as fine 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. 



being composed of connective tissue and covered on both surfaces by 

 flattened epithelioid cells (fig. 90). Between the lamellae are clefts for 

 the conveyance of lymph to the lymphatics of the epineurium. The 

 delicate connective tissue which lies between the nerve-fibres of the 

 funiculus is the endoneurium (fig. 88, end ; fig. 89, En). It assists in 



FIG. 90. NERVE-FUNICULUS 

 STAINED WITH NITRATE OF SIL- 

 VER, SHOWING THE OUTLINES OF 



EPITHELIOID CELLS OF THE 

 PERINEURIUM. 



The dark crosses on the nerve-fibres at 

 the nodes of Ranvier are due to the 

 staining of the axis-cylinder and of 

 & band of intercellular substance 

 which encircles the axis-cylinder at 

 the node (constricting band of Ran- 

 vier). 



supporting the longitudinally arranged meshwork of blood-capillaries, 

 and its interstices communicate with the lymphatic clefts of the 

 perineurium. 



The nerve- trunks themselves receive nerve-fibres (nervi nervorum) 

 which ramify chiefly in the epineurium and terminate in this in end- 

 bulbs. 



