23: 



Mr. B. B. Sarkar. 



other (the superior laryngeal) was connected by two filaments with that 

 ganglion and then passed to the tissue at the base of the heart (fig. 3). 



Superior Cervical 

 Ganglion — 



Superior Laryngeal 

 Nerve 



Cervical Sympathetic 

 Nerve 



inferior Cervical. 

 Ganglion 



Jfc Ganglion_of the. 



VagusTrunk 



-Vagus Nerve 



.Depressor 

 Nerve 



y Aorta 



Fig. 3. — Diagram showing the depressor passing down as two separate nerves, one of 

 which, arising from the superior laryngeal, goes to the aorta ; the other, arising 

 from the vagus trunk, to the base of the heart. The first one is connected with the 

 inferior cervical ganglion by two fine filaments. (These are also shown in figs. 1 

 and 2.) 



To determine the exact origin of the nerve, serial sections of the vagus 

 were made upwards from the angle where the superior laryngeal and the 

 depressor leave it. All three nerves are encased in a single epineurium until 

 the superior laryngeal separates from the vagus (fig. 6 — see Plate 4). On 

 examining such a series of sections a group of ganglion cells is found lying 

 between the superior laryngeal and the main vagus trunk just before the 

 superior laryngeal separates out (fig. 4). In some animals these cells are 

 continued into the beginning of the superior laryngeal nerve as far as the point 

 where its depressor branch leaves that nerve. "When the whole depressor or 

 one of its parts separates from the vagus after the superior laryngeal branch 

 has been given off, the group of ganglion cells in question extends down the 

 vagus trunk nearly as far as the point where its depressor branch emerges 

 (fig. 5). These cells probably give origin to afferent fibres of the- 

 depressor. In cases in which the depressor emerges high up,, the group 

 may lie close below the ganglion trunci, although distinctly separate from, 

 that sanglion. 



