SPINAL NERVES IN VERTEBRATES 173 



myzon. The vertebral ganglia were said to be in connection 

 with the ventral sensory rami by rami communicantes. John- 

 ston ('05) and ('08) described and figured a vertebral sympa- 

 thetic trunk in the branchial region of Petromyzon, w^hich takes 

 origin from the facial nerve and has connections with the vagus. 

 This nerve is composed of fine fibers and said to have sympa- 

 thetic nerve cells in the gill region, the peripheral processes of 

 which probably supply the neighboring blood vessels, lymph 

 sinuses and other visceral surfaces. Johnston did not find the 

 vertebral sympathetic ganglia as described by Julin, but found 

 one, and only one, peripheral ganglion cell in close relationship 

 with a ventral spinal nerve root. Numerous peripheral ganglion 

 cells were described and figured in the head region, some of which 

 were multipolar, but the majority were bipolar. They were 

 in relationship to the V, VII, IX, and X nerves. No vertebral 

 sympathetic ganglia and cord have been described for the 

 my^noids. A continuation of the vagus nerves to the viscera 

 is represented by J. Mtiller and Cole as a sympathetic trunk in 

 Myxine. The relationship of the vertebral sympathetic sys- 

 tem to the spinal nerves is too well known in the higher verte- 

 brates to need mentioning here. 



1. Peripheral spinal nerve cells 



As was pointed out earlier, nerve cells isolated and in clusters 

 appear peripherally in many of the spinal nerves. In the re- 

 construction of the two most cephalic spinal nerves (fig. 6) no 

 nerve cells were found other than the true spinal ganglion cells. 

 A spinal nerve in the pharynx region (fig. 5) contained a single 

 peripheral nerve cell (N.C.) situated in the ramus ventralis 

 close to the ventral border of the myotomes. 



In the reconstruction of the spinal nerves of the tail region of 

 the 20 cm. series (fig. 1) there is a single peripheral nerve cell 

 (N.C) located in the ramus ventralis passing between the last 

 two mucous sacs. In the second spinal nerve there is a nerve 

 cell (N.C.) in the dorsal sensory ramus at the base of a dorsal fin 

 ray. No peripheral nerve cells were found in the third, fourth 



