ioo6 HUMAN ANATOMY. 



The Nerve-Trunks. The fibres composing the peripheral nervous system are 

 grouped into the larger and smaller nerve-trunks which extend to various parts of the 

 body. In the make-up of those that supply both muscles and sensory surfaces 



gument or mucous membranes , as, for example, the median or the third division 

 of the trimeminal nerve, ti are included: (i) the efferent axones of 



motor neurone^ whose cell -bodies are situated within the spinal cord or brain ; (2) the 

 afferent dend: :v neurones within the spinal and other sensory ganglia ; 



and .} > the efferent axones of neurones within the sympathetic ganglia that accompany 

 the spinal fibres to the periphery and serve for the innervation of the involuntary 

 muscle of the bloc. ! and of the skin and the glands. 



The in: the various kinds usually more or less intermingled, are 



;>e<l into bundles, the funiculi, which differ in number and diameter according 

 to the si/e (if the entire trunk that they form. Kach funiculus is surrounded by a 

 definite sheath of dense connective tissue, the pcrincnriiun, which is directly con- 

 tinuous with the delicate fibro-el.istic tissue prolonged between the individual nerve- 

 fibres as the < ;i(/o>ifnrii<i. When well re-presented, the sheath of the funiculus 

 C' insists of concentric lamellae of fibrous tissue which enclose pcrhicurial lymph-spaces. 



849. 



I ; .- 



Blood-vessels 



-Perineurium 



*> 



Funiculus of 

 nerve- fibres 



Transverse section ..I sin. ill n ,,-d of loosely united funiculi. X 20. 



The latter, lined by flattened ,,,nn nw plates, are in relation with the clefts 



between the nerve-fibres, , , M the ..IK- hand, and with the lymphatics within the inter- 

 hmi< tilar tissue on the other. When-, as usual, the nerve IS composed of several 

 funiculi. these are loosely bound together and the entire trunk so formed is invested 



ral tibr. the <pincuriiun< in which course the blood-vessels 

 and lymphatics. These envelopes of the nerve trunk are continued over its branches, 



onto its smallest subdivisions. The last representative of these coverings 



n the indi\idual fibres as the x /i,;itli of IInil,\ that surrounds the fibre 

 and consists of flattened cells and delicate strand-, . ,f connective tissue outside the 

 neurilemina. 



In ' " f lhr nerve-trunk the transversely cut individual 



medullated ne,\,. t,|,,e. appear aa .mall circles, sharplv defined by a fine outline (the 



neurilemi h enclosing a deeply stained dot (the axis-cylinder in section) 



interval between the latter and file nemilemma, correspond in.-- to the space 



bv the mvelin, usually appears clear and unstained with the exception of 



niil uncertain sii^eMi.nis of membranous septa. In contrast with its 



unstained appearance in sections tin-ed with carmine, after the action of OSmic acid 



or sp,-, i.,l hematpxylin staining W. igert > the medullarv substance exhibits a dark 



-"id th. :,der ajipr.irs surroun-led by a deeply tinted ring The neuri 



