chap, xiv.] NERVE-FIBRES. 105 



which form an intercommunicating system, and 

 anastomose with the lymphatics of the epineurium 

 whence they can be injected. Between the lamellae, 

 and in the spaces, are situated flattened endotheloid 

 connective tissue corpuscles. 



The nerve-bundles are either single or compound. 

 In the former the nerve-fibres contained in a bundle 

 are not sub-divided into groups, in the latter the 

 bundles are sub-divided by thicker and thinner septa 

 of fibrous connective tissue connected with the peri- 

 neurium. When a nerve-bundle divides as when a 

 trunk repeatedly branches, or when it enters on its peri- 

 pheral distribution each branch of the bundle receives 

 a continuation of the lamellar perineurium. The more 

 branches the perineurium has to supply, the more re- 

 duced it becomes in thickness. In some of these minute 

 branches the perineurium is reduced to a single layer 

 of endothelial cells. When one of these small bundles 

 breaks up into the single nerve-fibres, or into small 

 groups of them, each of these has also a continuation 

 of the fibrous tissue of the perineurium. In some 

 places this perineural continuation is only a very 

 delicate endothelial membrane, at others it is of 

 considerable thickness, and still shows the laminated 

 nature. Such thick sheaths of single nerve-fibres, 

 or of small groups of them, represent what is called 

 Henle's sheath. 



138. The nerve-fibres are held together within the 

 bundle by connective tissue, called the Endoneurium 

 (Fig. 64). This is a homogeneous ground substance in 

 which are embedded fine bundles of fibrous connective 

 tissue, and connective tissue corpuscles, and capillary 

 blood-vessels arranged so as to form a network with 

 elongated meshes. Between the perineurium and the 

 nerve-fibres are found here and there lymph spaces ; 

 similar spaces separate the individual nerve-fibres, and 

 have been injected by Key and Retzius. 



