PRACTICAL HISTOLOGY. 



[XVII. 



fibres, and constitute the endoneurium. The larger blood- and 

 lymph-vessels lie in the epineurium and 

 A perineurium, while the endoneurium sup- 



ports the few capillaries which are distri- 

 buted to the nerve-fibres (fig. 190). 



The term Sheath of Henle is applied to 

 the prolongation of the perineurial sheath 

 usually a single lamella around a small 

 branch, or even one or two nerve-fibres. 



The following statement may facilitate the 

 study of the parts to be investigated : 



NERVE-FIBRES. 



I. Medullated (chiefly in cerebro-spinal 

 system). 



II. Non-Medullated (sympathetic or fibres 

 of Remak). 



A. Medullated Nerve Fibre consists of 



( i . ) Primitive sh eatk, sheath of Schwann 

 (or neurilemma). 



(2.) Nerve-corpuscles occur under the 

 primitive sheath in each inter- 

 annular segment. 



(3 . ) W h ite substance of Schwann, myelin, 

 or medullary sheath (with cylin- 

 der cones and incisures). It 

 contains a net-work of neuro- 

 keratin. 



(4.) Axis-cylinder, composed of primi- 

 tive fibrils (surrounded by a 

 sheath called the axilemma). 



(5.) Nodes of Ranvier and internodal or 

 interannular segments between 

 two successive nodes. 



Ranvier 's crosses and Frommanris lines, 

 tained by using nitrate of silver. 

 Sheaths of a Nerve-Trunk. Epineurium, 

 perineurium, and endoneurium. 

 B. Non-Medullated Nerve-Fibres consist of 



FIG. 182. Non-Meduiiated 

 Nerve-Fibre, vagus of Dog. 



b. Fibrils ; n. Nucleus ; p. 



Protoplasm surrounding it. 



(i.) A bundle of fibrils, usually enclosed in 



!2.) A transparent sheath or neurilemma (?). 

 3.) On the fibres are oval nuclei. 



