The Depressor Nerve of the Rabbit. 



231 



originate from the angle where the superior laryngeal leaves the vagus. 

 When the two branches of origin were separate, one usually left the vagus 

 at this point, but sometimes lower down, the other was "derived from the 

 superior laryngeal a short distance after it had left the vagus. In certain 

 cases the whole nerve ran along the superior laryngeal for a little distance 

 before emerging as a separate nerve. As Ludwig and Cyon state, the 

 depressor lies close to the cervical sympathetic throughout most of its course : 



Superior Cervical A 



Ganglion 9 



Superior Laryngeal 

 Nerve 



Cervical Sympathetic 



Nerve 



Inferior Cervical 

 Gonglion 



Ganglion of the 

 VagusTrunk 



Vagus Nerve 



Depressor 

 Nerve 



Aorta 



Superior Cervical 

 Ganglion 



Superior Laryngeal 

 Nerve 



Cervical Sympathetic 

 Nerve 



Inferior Cervical 

 Ganglion 



Ganglion ofrhe 

 VagusTrunk 



Depressor 

 Nerve 



Vagus Nerve 



Aorta 



Fig. 1. 



Fig. 2. 



Fig. 1. — Diagram of origin and course of depressor nerve in a rabbit, showing the usual 

 derivation of the nerve by two threads, one from the superior laryngeal and the 

 other from the vagus trunk. 



Fig. 2. — Diagram showing the nerve originating as a single filament from the superior 

 laryngeal. Note the (unusual) splitting and rejoining of the nerve in the middle of 

 its course. 



in the lower part of the neck one or two short branches unite it with the 

 inferior cervical ganglion. I have usually found it to divide at its lower end 

 into three filaments, one of which passes to the aorta and the other two to 

 the base of the heart. In two instances in which the two branches of origin 

 were quite separate throughout, one branch (the vagal) ran to the aorta 

 without forming any connexion with the inferior cervical ganglion,* while the 



* This ganglion, which has always been known to physiologists as the 

 cervical," is now frequently termed by anatomists the " middle cervical." 



; inferior 



