SYMPATHETIC GANGLIA 239 



As development advances, the sixth cranial sympathetic gan- 

 glion becomes more compact and somewhat farther removed from 

 the first spinal nerve and the cellular tract connecting the former 

 with the latter gradually becomes smaller and finally disappears. 

 The anterior portion of this sympathetic ganglion remains in 

 close proximity with the jugular ganglion. In embryos of 

 Opsanus 13 mm. in length, it lies in immediate contact with the 

 latter ganglion. 



From the anterior end of the sixth sympathetic ganglion, the 

 slender sympathetic trunk may be traced cephalad along the me- 

 dian aspect of the ganglionic complex of the vagus nerve. A 

 slight ganglionic enlargement, the anlage of the fifth sympathetic 

 ganglion, occurs at the level of the second lobe of the vagus 

 ganglion (fig. 1, sy 5). This ganglionic enlargement may be ob- 

 served almost as early as the sympathetic trunk can be traced. It 

 does not become conspicuous, however, and no direct connections 

 could be found between it and either the X or the IX cranial 

 nerves. As early as the sympathetic trunk may be traced ceph- 

 alad from the sixth ganglion, its fibers are accompanied by 

 cells obviously of nervous origin. It is probable, therefore, that 

 the relatively small number of cells which give rise to the fifth 

 sympathetic ganglion advance cephalad from the sixth sjonpa^het- 

 ic ganglion. 



The sympathetic trunk continues cephalad from the fifth sym- 

 pathetic ganglion along the ventro-mesial aspect of the root of 

 the IX cranial nerve but removed from the latter by a short in- 

 terval. Another sUght ganghonic enlargement, the anlage of 

 the fourth sjrmpathetic ganglion, occurs on the sympathetic 

 trunk at the level of the ganglion of the IX cranial nerve (fig. 1, 

 sy 4) • This ganglionic enlargement also may be observed almost 

 as early as the sympathetic trunk can be traced. Like the fifth 

 "sympathetic ganglion, it does not become conspicuous and no 

 connections could be observed between it and the IX cranial 

 nerve. It is probable, therefore, that, like the fifth sympathetic 

 ganglion, this ganglion also arises from cells which advance 

 cephalad from the sixth sympathetic ganglion. 



