MODES OF TERMINATION OF NERVE-FIBRES. 



103 



plexus. From the primary plexus smaller branches (a) come off, and 

 these form a secondary plexus (e) nearer the surface, generally imme- 

 diately under the epithelium if the ending is in a membrane covered by 

 that tissue. Finally, from the secondary plexus nerve-fibrils proceed 

 and form a terminal plexus 

 or ramification amongst the 

 epithelium-cells (fig. 126, p), 

 the actual ending being gene- 

 rally in free varicose fibrils (I). 

 Such a mode of ending in ter- 

 minal plexuses is most char- 

 acteristically seen in the cornea 

 of the eye. The nerve-fibrils p&. 

 may be brought distinctly 

 into view by staining with 

 chloride of gold, and then the 

 fibrillar structure of the rami- 

 fications of the axis-cylinders 

 also becomes very apparent. 



Nerve-endings in tendons. 

 A special modification of the 

 terminal plexus is met with 

 in many of the tendons, near 

 the points of attachment of 

 the muscular fibres. The 



Ttt.S 



FIG. 124. PART OF PACINIAN BODY, SHOWING 



THE NERVE-FIBEE ENTERING THE CORE. FROM 



tendon-bundles are somewhat AN OSMIC ACID PREPARATION. 



ms, entering nerve-fibre, the medullary sheath of which 

 is stained darkly, and ends abruptly at the core ; 

 ps, prolongation of primitive sheath, passing towards 

 the outer part of the core ; c.f, axis-cylinder passing 

 through the core of the central fibre ; e, some of the 

 inner tunics of the corpuscle, enlarged where they 

 abut against the canal through which the nerve-fibre 

 passes the dots within them are sections of the 

 fibres of which they are composed ; n, nuclei of the 

 tunics ; n', nuclei of the endoneurium, continued by 

 others in the outer part of the core. 



enlarged, and the nerve-fibres 



one, two, or even more in 



number pass to the enlarged 



part, and penetrating between 



the fasciculi of the tendon 



end in a terminal arborisation, 



beset with irregular varicosities. The whole structure, including the 



enlargement of the tendon-bundle in which the aborisation occurs, is 



known as the organ of Golgi (fig. 127). 



Ending of motor nerves. Lastly the nerves to muscles also ter- 

 minate in plexuses, which in striated (voluntary) muscles are collected 

 into special organs termed motor end-organs, or, incorrectly, end-plates. 



In involuntary muscle, the nerve-fibres, which near their termination 

 are entirely non-medullated, end in plexuses. The primary plexuses 

 are generally furnished with ganglion-cells in abundance. From these 

 other nerve-fibres pass which form secondary plexuses and terminal 



