384 



MORPHOLOGY OF NERVES. 



CLASSIFIED TABLE OF THE NERVES OF THE LIMBS, WITH THEIR 

 PROBABLE HOROLOGIES continued. 



LOWER LIMB. 



Dorsal nerves. 

 Small sciatic : gluteal branches and outer 



part of femoral division. 

 Perforating 1 cutaneous. 



External cutaneous. 

 Anterior crural. 1 

 External popliteal. 

 Musculo-cutaneous. 

 Anterior tibial. 



Ventral nerves. 

 ( Obturator. 



< N. to quadratus femoris. 

 f N. to obturator intern us. 



Branches of internal popliteal in thigh. 

 Cutaneous of obturator. 



j Internal popliteal ) ( Internal plantar. 



j and posterior tibial \ \ External plantar. 



Small sciatic : inner part of femoral division. 



UPPER LIMB. 

 Dorsal nerve*. 

 Circumflex: cutaneous part ... 



Musculo-spiral. 



Branches in arm ... 



Rest of trunk 



Radial 



Posterior interosseous 

 Ventral nerves. 

 N. to subclavius 

 Anterior thoracics 



N. to coraco-brachialis 



Musculo-cutaneous. 



Muscular part 



Cutaneous part ... 

 Median ... 



Ulnar 



Internal cutaneous 



N. ofWrisberg 



Intercosto-humeral ... ... ... ) 



Recurrent or mening-eal divisions. These are presumably afferent nerves, and are said 

 to be furnished by all the spinal nerves (p. 278). 



Visceral or sympathetic divisions. These are the white rami communicantes of the 

 sympathetic system, in connection with which their arrangement has been described (p. 358). 

 They are absent in the cervical region, as well as from the lower two or three lumbar, first 

 sacral, last sacral, and coccygeal nerves. The grey rami communicantes. as has already been 

 explained, are not branches of the spinal nerves, but are given off by the sympathetic to the latter. 

 * Ganglia. The ganglia found in connection with the peripheral nerves fall into two 

 groups, which differ in their structure and position. To the first group belong the spinal 

 ganglia on the posterior roots of the spinal nerves, which contain unipolar nerve-cells. The 

 other group includes the various * i/ntpa tlietic ganglia, the cells of which are multipolar. Both 

 groups have a common origin, their nerve-cells being derived from the neural crest of the 

 embryo (see Embryology, pp. 73 and 81). The spinal ganglia undergo but little change in 

 position in the course of development, and are always placed on the posterior roots of the 

 nerves at or near their aperture of exit from the spinal canal, whence they have been named 

 stationary ganglia by G-askell. The neuroblasts which form the nerve-cells of the sympathetic 

 ganglia, however, make their way from the primitive ganglion-rudiments along the spinal 

 nerves and their visceral offsets into the ventral portion of the body, and there become 

 collected into groups which give rise to the various sympathetic ganglia the splanchnic or 

 vagrant ganglia of Graskell. It is probable that all the ganglia of the sympathetic arise in 

 this way, but they have as yet been fully traced only in the case of the heart. The mode of 

 development especially of the ganglia in the my enteric plexuses of the alimentary canal has 

 not been observed. 



Constitution of a seg-mental nerve. A typical segmental nerve comprises (1) somatic 

 efferent fibres distributed to skeletal muscles ; (2) splanchnic efferent or sympathetic fibres 

 passing through the sympathetic system, where many if not all are interrupted by the nerve- 

 cells of the ganglia, to the visceral muscles and other unstriped muscles of the body, as well 

 as to the glandular organs ; (3) somatic afferent fibres supplying the skin and other parts of the 

 body- wall with sensory nerves ; and (4) splanchnic afferent fibres furnished to the viscera. 

 The somatic efferent fibres and the greater part, if not the whole, of the splanchnic efferent 

 fibres constitute the anterior root of the nerve, while the somatic afferent fibres run in the 

 posterior root, being connected with the cells of its ganglion, and the same is probably the 

 case with the splanchnic afferent fibres. In the cervical region, in addition to the two roots of 



1 According to Eisler the anterior crural nerve is not exclusively dorsal, but contains both ventral 

 and dorsal elements. The ventral part comprises the internal cutaneous nerve, the branch to the 

 pectineus, and the internal saphenous nerve. Instead of occupying a ventral position at their origin, 

 however, these branches are placed on the mesial side of the trunk, in consequence of a torsion, 

 amounting to about 90, which is to be recognized in the bundles of the nerve between the lumbar 

 plexus and Poupart's ligament, and which is probably associated with the inward rotation of the limb 

 during development. 



