94 



NERVE 



[CH. VII. 



The arrangement of the nerve-fibres in a nerve is best seen in a 

 transverse section. 



The nerve is composed of a number of bundles orfuniculi of nerve- 

 fibres bound together by connective tissue. The sheath of the whole 

 nerve is called the epineurium ; that of the f uniculi the perineurium ; 

 that which passes between the fibres in a funiculus, the endoneurium 

 (fig. 122). Single nerve-fibres passing to their destination are sur- 

 rounded by a prolongation of the perineurium, known as the Sheath 



FIG. 123. Section across the second thoracic anterior root of the dog, stained with osmic acid. 



(Gaskell.) 



of Henle. The nerve trunks themselves receive nerve-fibres which 

 ramify and terminate as end-bulbs in the epineurium. 



The size of the nerve-fibres varies ; the largest fibres are found in 

 the spinal nerves, where they are 144 to 19/x, in diameter.* Others 

 mixed with these measure T8 to 3'6/x. These small nerve-fibres are 

 the visceral nerves ; they pass to collections of nerve-cells called the 

 sympathetic ganglia, whence they emerge as non-medullated fibres, 

 and are distributed to involuntary muscle. They are well seen in 



* /* = micro-millimetre = T?r Vo millimetre. 



