ON THE TENTH PAIR OF NERVES. 
299 
division of the nerve, although that division was made in the neck; 
but there was sadly laborious breathing and frequent vomiting, 
and at length he died completely exhausted. 
The Cardiac Plexus .—The cerebro-visceral nerve furnishes one 
more considerable, but somewhat mysterious plexus, within the 
thorax, and that is about the heart. As soon as the nerve on each 
side has entered the thorax, small branches are directed to the 
base of the heart, but afterwards, and after the giving off of the 
pulmonary branches, a very considerable one proceeds from the 
right nerve towards the heart, and this separating into two as it 
approaches the base of the heart, is distributed to each auricle, 
and to the bloodvessels of the two divisions of the heart. Now, 
gentlemen, I have very little proof of the agency of this nerve as 
a motor one as it regards the heart ; and, comparing the cardiac 
with the pulmonary plexus, and, by-and-by, with the gastric one, 
I find that this organ is sparingly supplied with nervous fibrils; 
and I cannot help attributing some importance to the circumstance 
which I have just pointed out to you, that the cardiac plexus is prin¬ 
cipally made up of ramifications from the right nerve alone. I pre¬ 
sume not, in the present state of veterinary knowledge, to explain 
this ; although ] can guess at the reason of it, viz. that this cen¬ 
tral and all-important organ is endowed with a contractility of 
its own, independent of nervous influence, and that the charac¬ 
ter by which it is distinguished from every other part of the frame 
is that of inherent and inexhaustible contractility. Then I can 
conceive that the influence of this motor nerve shall be little evi¬ 
dent, or, in the usual working of the machine, comparatively little 
felt; yet at all times existing, and connecting the motions of the 
heart with the changes and the wants of the general system, or 
the diseases of particular parts, and to such a degree that, inour 
patients, who cannot tell us the situation or the nature of their 
maladies, the variable character of the pulse is, although too lit¬ 
tle studied among us, the most valuable of all the indications of 
disease. Thus far I can fancy (for I confess, gentlemen, we have 
no direct proof, and we are wandering where I seldom dare to 
venture, on the tempting but dangerous paths of mere theory), that 
these nerves are here maintaining their character in controlling 
the action of the heart according to the changing circumstances 
of health and disease, and even of mental emotion ; and when I 
regard the other supposed power of the cerebro-visceral nerve— 
when I look to the sensitive ganglion as well as to the motor ori¬ 
gin, I can comprehend a thousand sympathies, and perceive how 
this central machine is bound up with the system generally, and 
forms with it one connected whole. In my next lecture we will 
follow this nerve into the abdomen. 
