SPINAL NERVES IN VERTEBRATES 177 



fibers probably carry on the function of a sympathetic system 

 to the peripheral blood vessels and glands. The true spinal- 

 sympathetic system of the higher vertebrates may arise as a 

 survival and further modification of this primitive migration 

 of the neural crest cells, or the nem-al crest may later in phy- 

 logeny assume a sunilar but an entirely independent migratory 

 process along very different channels. 



2. Vagus nerve cells 



An examination of a reconstruction of the vagus-glossopharyn- 

 geal nerve trunk immediately after it leaves the skull discloses 

 several nerve cells (fig. 6, N.C.) scattered through it. These 

 cells have a tendency to be collected immediately cephalad of 

 the branching off of the glossopharyngeal nerve. Transverse 

 sections through this region show no grouping of the nerve 

 fibers into large bundles as is characteristic for lower levels. 

 Nerve cells appear in all parts of this common trunk, but no 

 section had more than two cells and there were no cells in the 

 majority of the sections. A few cells (figs. 6 and &, N.C.) were 

 found in the glossopharyngeal nerve at the point of its separation 

 from the vagus. Their arrangement and abundance are about 

 the same as in the common trunk. 



It will be seen from transverse sections (figs. 7 and 8) and a 

 reconstruction (fig. 5, X.) of the vagus nerve in the region of the 

 caudal extremity of the mandibular retractor muscles that the 

 nerve fibers have been separated into four bundles. Isolated 

 nerve cells are scattered throughout the three most dorsal 

 bundles, while these cells have accumulated in sufficient num- 

 bers in the ventral bundle to suggest an elongated ganglion. 

 From one or two cells in the cephalic and caudal sections of the 

 ventral bundle, these cells increase in number centrally until 

 some ten or fourteen cells will be seen in the most central sec- 

 tions (fig. 8). 



It is apparent then that all of the bundles of the vagus and 

 glossopharyngeal nerves contain receptive or sensory fibers, 

 unless perchance some of these cells represent effective sympa- 

 thetic relays. Likewise all of these bundles may contain ef- 



THE jpURNAL OF COMPARATIVE NEUROLOGY, VOL. 2S, NO. 1 



