74 



GENERAL ANATOMY. 



FIG. 51. Transverse section through a microscopic 

 nerve, representing a compound nerve-bundle, sur- 

 rounded by epineurium. Magnified 120 diameters. 

 The medullated fibres are seen as circles with a cen- 

 tral dot viz. medullary sheath and axis-cylinder in 

 transverse section. They are imbedded in endoneur- 

 ium, containing numerous nuclei, which belong to the 

 connective-tissue cells of the latter. (Klein and Noble 

 Smith.) p. Epineurium, consistingof laminae of fibrous 

 connective tissues, alternating with flattened nucleated 

 connective-tissue cells. I. Lymph-space between epi- 

 neurium and surface of nerve-bundle. 



fasciculi, which are hound together in a common membranous investment, and 

 constitute the nerve. 



In structure the common mem- 

 branous investment, or sheath of the 

 whole nerve, which is called the epi- 

 neurium, as well as the septa given off 

 from it, and which separate the fas- 

 ciculi, consists of connective tissue, 

 composed of white and yellow elastic 

 fibres, the latter existing in great 

 abundance. The tubular sheath of 

 the funiculi, called the perineurium, 

 consists of a fine, smooth, 'transparent 

 membrane, which may be easily sepa- 

 rated, in the form of a tube, from the 

 fibres it encloses ; in structure it con- 

 sists of connective tissue, which has a 

 distinctly lamellar arrangement, con- 

 sisting of several lamellae, separated 

 from each other by spaces containing 

 lymph. The nerve-fibres are held 

 together and supported within the 

 funiculus by delicate connective tissue, 

 called the endoneurium. It is con- 

 tinuous with septa which pass inward 

 from the innermost layer of the peri- 

 neurium, and consists of a ground-sub- 

 stance in which are imbedded fine bun- 

 dles of fibrous connective tissue which 



run for the most part longitudinally. It serves to support the capillary vessels, 

 which are arranged so as to form a network with the elongated meshes. The 

 cerebro-spinal nerves consist almost .exclusively of the medullated nerve-fibres, 

 the non-medullated existing in very small proportions. 



The blood-vessels supplying a nerve terminate in a minute capillary plexus, 

 the vessels composing which pierce the perineurium and run, for the most part, 

 parallel with the fibres ; they are connected together by short, transverse vessels, 

 forming narrow, oblong meshes, similar to the capillary system of muscle. Fine 

 non-medullated nerve-fibres accompany these capillary vessels, vaso-motor fibres, 

 and break up into elementary fibrils, which form a network around the vessel. 

 Horsley has also recently demonstrated certain medullated fibres as running in 

 the epineurium and terminating in tactile corpuscles or end-bulbs of Krause, or 

 in small, but perfect, Pacinian corpuscles. These nerve-fibres are termed nervi 

 nervorum, and have been considered to have an important bearing upon certain 

 neuralgic pains. 



The nerve-fibres, as far as is at present known, do not coalesce, but pursue an 

 uninterrupted course from the centre to the periphery. In separating a nerve, 

 however, into its component funiculi, it may be seen that they do not pursue a 

 perfectly insulated course, but occasionally join at a very acute angle with other 

 funiculi proceeding in the same direction ; from this, branches are given off, to 

 join again in like manner with other funiculi. It must be remembered, however, 

 that in these communications the nerve-fibres do not coalesce, but merely pass 

 into the sheath of the adjacent nerve, become intermixed with its nerve-fibres, 

 and again pass on, to become blended with the nerve-fibres in some adjoining 

 funiculus. 



Nerves, in their course, subdivide into branches, and these frequently commu- 

 nicate with branches of a neighboring nerve. In the subdivision of a nerve the 

 filaments of which it is composed are continued from the trunk into the branches, 



