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



and small-sized fibers predominating. In pyridine-silver prepa- 

 rations (fig. 15) non-medullated fibers are seen in considerable 

 numbers; but they are much less numerous than in the vagus 

 trunk and are less evenly distributed, 



THE RECURRENT NERVE 



In the lower part of the cervical trunk of the vagus a number 

 of large medullated fibers become grouped into a bundle near the 

 periphery of the nerve (fig. 11). This bundle separates off a little 

 lower down to form the recurrent nerve. At its origin this nerve 

 is composed of two quite sharply defined areas: one (fig. 8, a) 

 represents the bundle of large medullated fibers mentioned above; 

 the other (fig. 8, h) contains small and medium-sized medullated 

 fibers. In figure 8 there is also seen a third area, c, formed of 

 sympathetic fibers. The recurrent nerve at its origin from the 

 vagus is closely associated with the branches of the inferior 

 cervical sympathetic ganglion. 



Pyridine-silver preparations show that there are few, if any, 

 non-medullated fibers in the recurrent nerve aside from this ob- 

 viously sympathetic bundle that accompanies it. Molhant found 

 that the smaller fibers of the recurrent nerve, that is, those in 

 bundle b, were distributed in the cardiac, esophageal and tracheal 

 branches, and that the nerve as it enters the larynx is made up 

 entirely of large medullated fibers. Our preparations confirm 

 these observations. 



THE VAGUS BELOW THE ORIGIN OF THE RECURRENT NERVE 



As has already been stated, the vagus, is very closely connected 

 with the sympathetic trunk at the level of the inferior cervical 

 ganglion and at the origin of the recurrent nerve. Below the level 

 of the recurrent nerve the lower loop of the ansa subclavia runs 

 with the vagus for a short distance. The thoracic vagus, after the 

 ansa subclavia has separated from it, has the same structure as 

 the cervical trunk, except that it contains an even greater propor- 

 tion of non-medullated fibers. This is in part accounted for by 

 the fact that the recurrent nerve has taken out most of the 



