THE NERVOUS SYSTEM. 
THE THORACIC PLEXUSES. 
Cardiac Plexuses.—The cardiac branches of the pneumogastric nerve (both 
cervical and thoracic) combine with the cervical cardiac branches of the sympathetic 
to form the superficial and deep cardiac plexuses. 
The superficial cardiac plexus is placed in the hollow of the aortic arch, 
superficial to the pericardiuin. It contains a small 
ganglion (ganglion of Wrisberg), and is joined by two 
small nerves—(1) the cardiac branch from the superior 
cervical ganglion of the sympathetic, and (2) the 
inferior cervical cardiac branch of the pneumogastric 
—hboth of the left side—which reach it after passing 
over the arch of the aorta. { 
Branches anil Communications.—From the plexus 
branches of communication pass (1) to the left half 
of the deep cardiac plexus, between the aortic arch 
and the bifurcation of the pulmonary artery ; (2) to 
the left anterior pulmonary plexus along the left 
branch of the pulmonary artery; (3) the branches of 
distribution to the heart extend along the pulmonary 
artery to join the anterior or right coronary plexus, 
which supplies the substance of the heart in the course 
of the right coronary artery. 
The deep cardiac plexus is much the larger. It 
is placed behind the arch of the aorta, on the sides 
of the trachea, just above its bifurcation. It consists 
of two lateral parts, joined together by numerous com- 
munications around the termination of the trachea. 
The two portions of the plexus are different in their 
constitution and distribution. The right half of the 
plexus is joined by both the cervical and thoracie 
branches of the right pneumogastric and by the 
branches of the right inferior laryngeal nerve, as well 
as by branches from the superior, middle, and 
inferior cervical gangha of the sympathetic. The /eft 
half of the plexus is joined by the superior cervical 
cardiac branch of the left pneumogastric, by branches 
from the left inferior laryngeal nerve, and by branches 
from the middle and inferior cervical ganglia of the 
left sympathetic; it also receives a contribution from 
the superficial cardiac plexus. 
The deep cardiac plexus is distributed to the 
heart and lungs. The right half of the plexus for 
the most part constitutes the anterior or right 
coronary plexus, reaching the heart alongside the 
ascending aorta, and is distributed to the heart sub- 
stance in the course of the right coronary artery. It 
is reinforced by fibres from the superficial cardiac 
plexus, which reach the heart along the pulmonary 
artery. Fibres from the right half of the deep cardiac 
plexus pass also to join the posterior or left coronary 
\Sy 
Cart 
Fic. 468.—THE CONSTITUTION OF 
THE CARDIAC PLEXUSES. 
Sy, Cervical sympathetic cord ; C.1, 
Superior, C.2, Middle, and C.3, In- 
ferior cervical ganglia ; Car.1, Su- 
perior, Car.2, Middle, and Car.3, 
Inferior cervical cardiac sympa- 
thetic branches ; Va, Pheumogastric 
nerve; R.L, Recurrent laryngeal 
nerve ; s, Superior, and i, Inferior 
cervical cardiac branches of vagus ; 
D.C.P, Deep cardiac plexus ; S.C.P, 
Superficial cardiac plexus ; A.P.P, 
Anterior pulmonary plexus ; P.P.P, 
Posterior pulmonary plexus ; 
R.Car.P, Right, and L.Car.P, Left 
coronary plexuses; Art.Pul, Pul- 
monary artery. 
plexus, and others extend outwards to join the anterior 
pulmonary plexus of the right side. 
The left half of the deep cardiac plexus, reinforced 
by fibres from the superficial cardiac plexus, is distri- 
buted to the heart in the form of the left or posterior 
coronary plexus, which is joined by a few fibres behind 
the pulmonary artery from the right half of the plexus, and supplies the heart 
substance in the course of the left coronary artery. The left half of the plexus 
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