28 THORAX 



join the corresponding intercostal nerve. One of these 

 branches, called the white root of the ganglion, contains 

 medullated fibres which are passing from the medulla spinalis 

 (O.T. spinal cord) through the intercostal nerve to the 

 ganglion. The other, the grey root, consists of non-medullated 

 fibres which are passing from the cells of the ganglion to the 

 nerve. Some of these fibres are distributed with the branches 

 of the nerve, and others run medially, along the intercostal 

 nerve, to the spinal nerve trunk, whence some are distributed 

 by the posterior branch and others pass more medially to 

 the membranes of the medulla spinalis. 



(2) Medial Branches. (a) Pulmonary ; (fr) Aortic ; (c] 

 Splanchnic. (a) The pulmonary branches arise from the 

 second, third, and fourth ganglia. They run anteriorly to the 

 posterior surface of the root of the lung. There they com- 

 municate with branches of the vagus, forming a plexus called 

 the posterior pulmonary plexus, (b) The aortic branches are 

 fine filaments which arise from the upper five ganglia and pass 

 to the coats of the aorta ; the dissector will rarely be able to 

 trace them in an ordinary dissection, (c) The splanchnic 

 branches arise from the sixth to the last ganglion, and they run 

 together to form three distinct nerves the greater, the lesser, 

 and the lowest splanchnic nerves, which are all destined for 

 the abdominal viscera. 



Nervus Splanchnicus Major. This nerve is formed by the 

 union of four or five roots derived from the sixth to the tenth 

 ganglia, or from the portions of the trunk between. It 

 passes downwards, on the bodies of the vertebrae, pierces the 

 diaphragm, and terminates in the coeliac (O.T. semilunar) 

 ganglion of the same side in the abdomen. 



Opposite the last thoracic vertebra there is frequently a small ganglion 

 upon the greater splanchnic nerve, or connected with it ; from this ganglion 

 branches are distributed to the aorta, where they communicate with their 

 fellows of the opposite side. 



Nervus Splanchnicus Minor. The small splanchnic nerve 

 arises by two roots either from the ninth and tenth, or from 

 the tenth and eleventh ganglia. It also pierces the crus of 

 the diaphragm and ends in the coeliac ganglion. 



Nervus Splanchnicus Imus. The lowest splanchnic nerve is 

 a minute branch which springs from the last thoracic ganglion. 

 It is frequently absent, but when it is present it pierces 

 the crus of the diaphragm and ends in the renal plexus. 



