

CH. VII.] 



NON-MEDULLATED FIBRES 



77 



nerve is called the epineurium ; that of the funiculi the perineurium ; 

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

 (fig. 94). Single nerve-fibres passing to their destination are sur- 

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

 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 14'4 to 19 /* in 

 diameter.* Others mixed with these 

 measure 1*8 to 3 '6 /UL. 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 distri- 

 buted to involuntary muscle. They are well seen in sections stained 

 by osmic acid, the black rings being the stained medullary sheaths 

 (fig. 95). 



The non-medullated fibres or fibres of Remak have no medullary 

 sheath, and are therefore devoid of the double contour of the medul- 

 lated fibres, and are unaffected in appearance by osmic acid. They 



FIG. 95. Section across a nerve 

 bundle in the second thoracic 

 anterior root of the dog-, stained 

 with osmic acid. (Gaskell.) 



FIG. 96. Grey, or non-medullated nerve-fibres. A. From a branch of the olfactory nerve of the 

 sheep ; two dark-bordered or white fibres from the fifth pair are associated with the pale olfactory 

 fibres. B. From the sympathetic nerve, x 450. (Max Schultze.) 



consist of an axis cylinder covered by a nucleated sheath. 

 branch frequently. 



* fj. micro-millimetre = iVs^ millimetre. 



They 



