300 



MICROSCOPIC ANATOMY OF THE ORGANS. 



bundle, and are lined on the inner surface with a layer of flat 

 cells, whose outlines can be well made out in silver nitrate 

 preparations. This connective tissue separating the individual 

 bundles is known as the perineurium (Fig. 225). From it 



FIG. 225. 



AVr/v fibres 

 cut across 



lEpineurinni 



Nucleus 



Endoneurium 



^Blood-vessel 



'Perinenrium 



Part of a transverse section of the human nervus tibialis anticus. X 76. 



connective-tissue septa run into the interior of the bundles of 

 nerve fibres, forming the so-called endoneurium. This tissue 

 surrounds small bundles of fibres (primary bundles), and gives 

 origin to the endoneural sheath (Henle's sheath) of the indi- 

 vidual fibres. The epineurium and perineurium contain, as 

 opposed to the endoneurium, fat cells and elastic fibres. 



As the nerve approaches its termination, it breaks up into 

 fine branches. Those made up of a simple bundle are sur- 

 rounded by a lamellated sheath. Fibres which are not joined 

 to form bundles possess only Henle's sheath. 



The sympathetic nerves consist for the most part of non- 

 mednllated fibres, although a certain number of medullated 

 fibres may also be present. They are grouped together in 



