THE NERVOUS SYSTEM i8i 



clavian artery obliquely. The fourth, and more variable, branch to 

 leave the gang, subclav. antr. is an anterior visceral nerve, which 

 passes alongside the anterior gastric artery to the stomach. This 

 also seems to occur more frequently on the right side than on the 

 left. Where the anterior visceral nerve does not separate from the 

 anterior subclavian ganglion, it does so from the posterior one. 

 The nerve described by Andersson as leaving the nerve strand just 

 in front of the gang, subclav. antr. and entering N. tr. intest. X has 

 not been found. 



It may be noted here that the rami communicantes from the first 

 six spinal nerves are not easy to see, since they frequently leave the 

 nerve while it is still within the subvertebral muscles, and pass 

 mesially through them to emerge close to the vertebral column. 

 Andersson fails to find any r. communicans from the fourth spinal 

 nerve, but it is certain that such exists in the majority, if not in all cases. 



The ganglion suhclavius posterior (g.scl.p.) marks the anterior end 

 of the abdominal portion of the sympathetic chain. It is fairly large 

 and frequently gives rise to the anterior visceral nerves (n.vis.a.) — 

 see above. The next two ganglia — five and six — are also large, and, 

 like all the subsequent ganglia of this section, have adrenal tissue 

 intimately associated with them. In this section also the ganglia and 

 the adrenal tissue are very closely applied to the post-cardinal veins, 

 and frequently envelop them like a sleeve. The longitudinal nerve- 

 fibres run parallel with the veins, and there is also a tendency in this 

 region, particularly in the anterior two-thirds, for the fibres to pass 

 from one ganglion to another in a divided condition, so that the 

 strand then appears to be double, treble, or in some higher multiple. 

 Sometimes one of the smaller bundles may miss a ganglion and join 

 the succeeding one, so that it is not possible to give an exact and 

 detailed description of the chain which will serve for any specimen. 

 Similarly with the ganglia, they also are very variable both in size and 

 arrangement. They normally, but not invariably, occur at the points 

 where the rami communicantes join the longitudinal strand. Bearing 

 in mind the disjunctive condition of this region of the sympathetic 

 chain in Selachians (Young, 1933), it is evident that Salamandra 

 forms a truly intermediate type between this and the more regular 

 and definite arrangement found in the Frog. There is a distinct 

 tendency for the rami communicantes in the posterior region of the 

 abdomen, i.e. in the region of the kidneys, to bifurcate and join 

 the longitudinal chain at two points. This bifurcation may occur 

 right at the point of separation from the spinal nerve, so that the 

 ramus communicans then appears double. Whether this subdivision 



