668 THE NERVOUS SYSTEM. 4 
in the gangliated cord or its peripheral branches, become connected with the 
sympathetic ganghon cells, or with the cells of peripheral (collateral or terminal) 
ganglia, from which again (non-medullated) axons proceed to supply branches 
to viscera and vessels. The ultimate destination of the upper stream of white 
rami from the thoracic nerves has been mentioned in the description of the 
cervical sympathetic ; the peripheral branches supplying thoracic organs contain 
vaso-motor fibres for the lungs and aorta. The peripheral branches from the lower 
part of the sympathetic cord in the thorax, receiving white rami from the 
lower thoracic nerves, are mainly destined for distribution to structures below 
the diaphragm. They comprise (a) viscero-inhibitory fibres for the stomach and 
intestines; (>) motor fibres for part of the rectum; (¢) pilo-motor fibres for the 
lower part of the body; (d) vaso-motor fibres for the abdominal aorta and its 
branches, and for the lower limbs; (e@) secretory, and (f/f) sensory fibres for the 
abdominal viscera. The thoracic part of the sympathetic cord is placed upon 
the heads of the ribs, and is covered over by the pleura. 
The branches from the ganghated cord are, as in the neck, divisible into two 
sets—(4) Central branches, communicating with other nerves, and (L) peripheral 
branches, distributed in a plexiform manner to the thoracic and abdominal viscera. 
Central Communicating Branches.— The white rami communicantes from 
the thoracic nerves have already been described. Passing forwards from the 
beginning of the anterior primary divisions of the nerves, they become connected 
with the gangha or the commissural cord of the sympathetic. 
The gray rami communicantes are branches arising irregularly from each thoracic 
ganglion, which, passing backwards along with the white rami, join the anterior 
primary divisions of the thoracic nerves. 
Peripheral Branches of Distribution.—These branches arise irregularly 
from the gangla and the commissural cord. They are composed of non-medullated 
fibres (splanchnic efferent), derived from the ganglon cells, and medullated fibres 
(splanchnic efferent and afferent), derived directly from the white rami, without 
the intervention of the cells of the gangha. 
1. Pulmonary Branches.—From the gangliated cord opposite the second, third, 
and paren gangha fine filaments arise which join the posterior pulmonary plexus. 
_ Aortic Branches. —The upper part of the thoracic aorta receives fine branches 
fae ‘the upper five thoracic ganglia. 
3. Splanchnic Nerves.—Three nerves arise from the lower part of the 
ganghated cord, partly from the ganglia themselves, and partly from the com- 
missural cord between the gangha. Passing downwards over the bodies of the 
thoracic vertebree they pierce the diaphragm, to end in the abdomen. 
(a) The great splanchnic nerve (n. splanchnicus major) arises from the 
gangliated cord between the fifth and ninth ganglia. By the union of several 
irregular strands a nerve of considerable size is formed, which descends in the 
posterior mediastinum, and piercing the crus of the diaphragm, joins at once the 
upper end of the semilunar ganglion of the solar plexus. In its course in the 
thorax the great splanchnic ganglion (g. splanchnicum) is found upon the nerve. 
It is more prominent in the foetus than in the adult. From both nerve and ganglion 
branches arise in the thorax for the supply of the cesophagus and descending 
thoracic aorta (Fig. 479). 
(>) The small splanchnic nerve (n. splanchnicus minor) arises from the ganghated 
cord opposite to the ninth and tenth ganglia. It passes over the bodies of the 
lower thoracic vertebrae, pierces the diaphragm near or along with the great 
splanchnic nerve, and ends in the solar plexus (aortico-renal ganglion). 
(c) The least splanchnic nerve (n. splanchnicus imus) arises from the last 
thoracic ganglion of the sympathetic, or it may be a branch of the smaller 
splanchnic nerve. It pierces the diaphragm, and ends in the renal pleaus. 
THE LUMBAR PART OF THE SYMPATHETIC CORD. 
The lumbar part of the sympathetic cord is placed upon the bodies of the 
lumbar vertebra, internal to the origins of the psoas muscle, and in front 
