52 M. R. CHASE AND S. W. RANSON 



bound together in a common sheath in the neck, remain inde- 

 pendent and distinct. In each series some few very fine sjonpa- 

 thetic filaments could be traced into the vagus; but no communi- 

 cating twigs of large size were seen passing between these two 

 nerves in the common sheath. On the other hand, free communi- 

 cations between the pharnygeal and laryngeal branches and the 

 sympathetic were found. Some fairly good-sized bundles of sym- 

 pathetic fibers join these branches and run along them to join 

 the vagus trunk. These sympathetic bundles can be recognized 

 easily in the vagus, where they retain their individuality and are 

 differentiated from the vagus fibers by their lighter stain and 

 the compactness with which the fibers are grouped. These sym- 

 pathetic bundles can be followed long distances in serial sections 

 as well-defined independent bundles within the vagus. These 

 sjrmpathetic bundles can sometimes be followed into the vagus, 

 along its trunk, and out again without their having in any way 

 lost their identity. 



It thus appears that the cervical trunk of the vagus in the dog, 

 although contained for some distance in a common sheath with 

 the sympathetic, is not especially intimately connected with that 

 nerve; and the number of sympathetic fibers that enter the vagus 

 is insignificant in comparison with the total number of its non- 

 medullated fibers. So far as we have been able to determine, 

 these sympathetic fibers are all contained within well-defined 

 bundles which run with the vagus for a short distance to leave it 

 again at another level. 



THE VAGUS AT THE LEVEL OF THE INFERIOR CERVICAL GANGLION 

 OF THE SYMPATHETIC 



In the lower part of the neck the sympathetic leaves the 

 vagus to run into the inferior cervical ganglion. This ganglion is 

 connected with the vagus trunk by numerous small and a few 

 good-sized bundles of sympathetic fibers. The lower pole of the 

 ganglion is attached to the vagus and to the beginning of the recur- 

 rent laryngeal nerve by one or more good-sized fascicles. These 

 represent the lower half of the ansa subclavia and leave the vagus 



