NERVE TRUNKS 



14? 



perineurium stands in the same relation to the funiculus as does the 

 epineurium to the whole nerve trunk. 



Fro.ni the inner surface of the perineurium, septa pass into the 

 funiculus and break up to form a fine connective tissue framework, the 

 endoneurium, for the support of the individual nerve fibers. On sepa- 

 rating the fibers of a funiculus with needles a portion of this fibrous 

 endoneurium remains adherent to the surface of the nerve fiber and 

 gives the appearance of an outermost fibrous sheath, the so-called con- 

 nective tissue sheath of 

 Henle. * 



Nerve trunks fre- 

 quently branch, the 

 branches being formed 

 either by an individual 

 funiculus or by groups of 

 funiculi. In the smaller 

 nerve trunks the funiculi 

 are further subdivided. 

 It is by anastomosis of 

 the funiculi that most of 

 the nerve plexuses are 

 formed. Individual nerve 

 fibers of the medullated 

 type do not generally 

 branch except in those 

 portions which are naked 

 axis cylinders, viz., at the 



cytoproximal portion of the axon by means of collaterals, and at the 

 cytodistal portion by means of end arborizations. Occasionally also col- 

 laterals arise at a node of Eanvier. 



Vascular Supply. The nerve trunks are well supplied with blood- 

 vessels. The larger of these are found in the epineurium, and from 

 thorn branches of considerable size enter the septa to be distributed 

 throughout the perineurium to the funiculi. The coarser septa of the 

 endoneurium contain minute arterioles and venules. A capillary network 

 with elongated meshes occupies the finer divisions of the endoneurium, 

 its vessels being thus brought into contact with the nerve fibers. 



Perivasr-ular lymphatic vessels abound in the epineurium and its 

 septa, and lymphatic tissue spaces are found throughout the connective 

 tissue of the nerve trunk. Where the cerebrospinal nerve trunks pene- 



FIG. 162. TRANSECTION OF THE SCIATIC NERVE 

 OF A DOG. 



The fat cells and the myelin sheaths of the nerve 

 fibers have been blackened by osmium tetroxid. a, 

 fat cells; b, b', bloovi vessels, that at b' lies within a 

 funiculus; c, epineuiium; d, perineurium; e, coarser 

 bands of the endoneurium. Osmium tetroxid. Photo. 

 X 30. 



