Chap. XIV.] 



NER VE-FIBRES. 



109 



the internodal segment. Each internodal segment has 

 generally one, occasionally more than one, nerve 

 corpuscle. The medul- 

 lary cylinder of each in- 

 ternodal segment is made 

 up of a number of coni- 

 cal sections (Fig. 6 6 A) 

 imbricated at their ends 

 (Schmidt, Lantermann) 

 (Fig. 66), and each such 



3. Medullated Nerve- 

 fibres. 



A, A medullated nerve - fibre, 

 showing the subdivision of the 

 medullary sheath into cylin- 

 drical sections imbricated with 

 their ends ; a nerve corpuscle 

 with an oval nucleus is seen 

 between the neurilemnia and 

 the medullary sheath ; B, a 

 medullated nerve fibre at a 

 node or constriction of Ranvier; 

 the axis cylinder passes unin- 

 terruptedly from one segment 

 into the other, but the medul- 

 lary sheath is interrupted. 

 (Key and Retzius.) 



Fig. 65. Medullated Nerve - fibres, 

 after staining with Nitrate of Silver. 



a, The axis cylinder ; 6, Ranvier's constric- 

 tion. (Key and Retzius.) 



section is again made up of 

 a large number of rod-like 

 structures (Fig. 67) placed 

 vertically on the axis cylin- 

 der. 



These rods are, how- 

 ever, connected into a net- 

 work. The network itself 

 is very likely the neuro- 

 keratin of Ewald and Kuhne, 

 whereas the interstitial sub- 

 stance of the network is 

 probably the fatty sub- 

 stance leaving the nerve- 

 fibre in the shape of droplets 



