THE THORAX 



t035 



monary branches are given off to the posterior pulmonary plexus. 

 From the fifth ganglion downwards the three splanchnic (' visceral ') 

 nerves — great, small, and least — are given off. 



The great splanchnic nerve arises by five separate roots from the 

 fifth, sixth, seventh, eighth, and ninth ganglia, the fibres of the 



upper roots being traceable in the 

 sympathetic cord as high as the 

 second ganglion. The roots arch 

 obliquely forwards and downwards 

 upon the sides of the bodies of the 

 adjacent vertebrae, and by their 

 union they form a large nerve, 

 which pierces the crus of the 

 diaphragm and terminates in the 

 semilunar ganglion of the epi- 

 gastric or solar plexus. The great 

 splanchnic nerve contains a large 

 number of spinal fibres, which 

 impart to it a white colour and 

 firm consistence. The right nerve 

 presents a small ganglion just be- 

 fore it leaves the thorax, called the 

 splanchnic ganglion, and there may 

 be one on the left nerve. The great 

 splanchnic nerve gives vascular 

 branches to the lower part of the 

 thoracic aorta. 



The small splanchnic nerve arises 

 by two roots from the tenth and 

 eleventh ganglia. It pierces the 

 crus of the diaphragm, and termi- 

 nates in the aortico-renal ganglion 

 of the epigastric or solar plexus. 



The least splanchnic nerve, which 

 is sometimes absent, arises by one 

 root from the twelfth ganglion. It 

 either passes behind the internal" 

 arcuate ligament of the diaphragm 

 or through the crus, and it termi- 

 nates in the renal plexus. When 

 the least splanchnic nerve is ab- 

 sent, its place may be taken by a 

 branch from the small splanchnic 

 nerv^e. 

 Subcostal Muscles. — These are 

 small indefinite muscular sheets, which lie on the inner surfaces 

 of the ribs in the region of the angles. They coincide in direction 

 with the internal intercostal muscles, and are best developed 

 interiorly. They are attached to the inner surfaces of the ribs 



Fig. 425. — Scheme of the Gang- 

 LiATED Cord of the Sympa- 

 thetic IN THE Thorax (after 

 Flower). 



I to 12. Thoracic Ganglia 

 R.C. Rami Communicantes 

 B.D. Branches of Distribution from 



Upper Ganglia 

 G.S. Great Splanchnic Nerve and 



Ganglion 

 S.S. Small Splanchnic Nerve 

 L.S. Least Splanchnic Nerve 



