60 
ANIMAL PATHOLOGY. 
tion, and in all of them the act of deglutition is more easily and 
safely performed. 
The superior laryngeal branches are prominent in your dissec- 
tions, and cannot fail of being recognized. These nerves soon 
divide into an external and internal branch, and having reached 
the side of the larynx, ramify on the muscles concerned in the 
construction of the larynx, and also on the posterior pha- 
ryngeal constrictor compelling it to assume at the same time 
the same action : they likewise visit the thyroid gland for 
some purpose unknown. The internal branch passes through an 
aperture in the membrane connecting the thyroid cartilage and 
the hyoid bone, and then separates into numerous fibres, taking 
opposite directions upwards and downwards. The former go to 
the epiglottis and the pharyngeal membrane, still more connect- 
ing the pharynx and the larynx in the discharge of one common 
function ; the ascending branch supplies the mucous membranes 
about the arytenoid cartilages and the rimae glottidis, and gives 
filaments to s the constrictor muscles, and, within the mucous 
membrane, there are anastomoses with the inferior laryngeal — 
the recurrent nerve — the nerve which governs the expansion of 
the larynx ; thus establishing a useful and beautiful harmony be- 
tween the apparently opposing powers that regulate the working 
of this exquisitely constructed machine : — but more of this here- 
after. 
The Cervical Plexus . — As we proceed down the neck, we find 
several filaments from this nerve given to the cervical plexus. 
This plexus is composed of communications from the four first 
cervical nerves with each other, and with the great sympathetic ; 
and these compound branches again interlacing and forming an 
intricate but powerful plexus of nervous influence. It extends, 
from some of the muscles even of the face, to those of the sca- 
pula and the anterior portion of the chest. Beginning to see, as 
we do already, the connexion of the great spinal organic with the 
functions of respiration and circulation and digestion, we per- 
ceive at once the importance of an anastomosis like this, by 
means of which almost every important muscle in the region of 
the frame is rendered occasionally subservient to the principle of 
organic life. They all involuntarily assist in the common dis- 
charge of the three important functions just mentioned; and in 
cases of necessity they are available to almost any extent that 
can be desired. As an excito-motory nerve, how valuable is the 
influence of the great spinal organic on a plexus like the cervi- 
cal ; presiding over some part of it, influencing the rest, and 
preserving the sympathy so necessary between the different parts 
of the organic system ! 
