295 
ON THE TENTH PAIR OF NERVES. 
tion of the fibres of the oesophagus causes the pellet to descend 
towards the stomach. The animal has little to do with the force, 
or even the action of these fibrils. If the pellet is too laige, 
and cannot be driven on by the proper muscles of the oesophagus, 
even when they are excited to forcible or spasmodic action by 
the continuance of their natural stimulus, the pressure of the 
food, no act of the will can avail aught; and mechanical means 
alone, as the swallowing of some liquid, or the attempted deglu¬ 
tition of air, or, as the last resort, the probang for the human 
being, and the probang alone in the quadruped, will be effectual 
in removing the obstruction. In the action of this branch we 
recognize the organic principle alone. 
Arterial Branches .—Next are branches to the carotid, ramify¬ 
ing upon, and winding around it, and forming a complicated 
plexus, particularly observable at its bifurcation. I will not 
enter here into the disputed question of the power of the aiteiies, 
but I plainly recognize a muscular coat, thin and weak, near the 
grand central machine, but increasing in thickness and strength 
as I recede from the heart. It doubtless has its peculiar action, 
or it would not surround the artery. What that precise action is, 
I will not here inquire; but the vessel is indebted for it exclusively 
to the agency of these nervous branches. No spinal influ¬ 
ence can be traced to these vessels, except by the most circuitous 
anastomosis : it is the organic principle which is here also at work. 
The Laryngeal Branch .—The branches to the larynx are very 
large, and can scarcely fail of being recognized in your dissec¬ 
tions. They cross the carotid artery, wind down upon the side 
of the pharynx, and, in order to reach the larynx, pass tlnough 
an aperture on each side at the base of the cornu by means or 
which the hyoid bone articulates with the thyroid cartilage; 
they then ramify upon those muscles of the larynx which aie 
concerned in the constriction of the glottis. This branch anasto¬ 
moses with another derived also from the spino-cerebral, and at 
which we shall presently arrive, and the fibres of which aie 
principally expended on the dilators. 
Course 0/ the Nerve down the Neck .—I now trace the path of 
the cerebro-visceral down the neck, still in the same sheath with 
the great organic, and in company with the carotid artery. 
There are no branches given to the neighbouring parts, foi there 
are none here that are necessary to, or that can be well employed 
in, the purposes of organic life ; but there are almost innumera¬ 
ble filaments of communication between the spino-visceral and 
the great organic, more closely allying them togethei, although 
not identifying them; and preparing them for the completion of 
the all-important functions which they have soon to discharge. 
