138 1NNERVAT10N. [c HAP. XXI. 



The lesser splanchnic nerve takes its rise by two roots from the 

 eleventh and twelfth, or from the tenth and eleventh ganglia ; it 

 passes down in similar course to the larger nerve, parallel to, and 

 behind it, pierces the diaphragm, and unites with the renal plexus 

 of nerves, and with the aortic plexus. 



The striking analogy between these nerves and the cardiac nerves 

 cannot fail to attract the attention even of the most superficial ob- 

 server. The latter nerves, distributed to an important organ in the 

 thorax, have their rise in the neck; and the splanchnic nerves, de- 

 riving their origin from nearly all the thoracic ganglia, are devoted 

 to important viscera of the abdomen. 



Of the Lumbar and Sacral Portions of the Sympathetic. The chain 

 may be followed down to the coccyx; the lumbar ganglia are small 

 and irregular in number. The continuity of the chain between the 

 lumbar and dorsal segments, is maintained sometimes by a small in- 

 tercommunicating cord, between the last dorsal and first lumbar 

 ganglion, which pierces the diaphragm, sometimes by a branch of the 

 greater or lesser splanchnic, which of course establishes the contin- 

 uity indirectly. The branches of communication of these nerves 

 with the lumbar spinal nerves, are sufficiently distinct, and some of 

 them are of great length. The gray branches are, according to 

 Beck, larger than the corresponding ones in the thorax. 



The nerves which come from the lumbar portion of the sympa- 

 thetic are destined to the aorta, and to the lumbar arteries; the 

 greater part of them form a plexus around the aorta, between the 

 mesenteric arteries, from which proceed fibres to form the inferior 

 mesenteric plexus, which follows the inferior mesenteric artery; be- 

 low this artery the aorta is still embraced by a plexus, (inferior 

 aortic plexus) which divides into the hypogastric plexuses, one on 

 the right and the other on the left, which supply the rectum and 

 bladder, the organs of generation, and the accessory parts. At 

 the base of the coccyx, the sympathetic of the right side, anastomoses 

 with that of the left by means of a branch passing on each side from 

 the last sacral ganglion to a ganglion in front of the coccyx, which 

 is called the ganglion impar. 



adjacent to the nerve from which it arises, becomes associated with some ge- 

 latinous fibres. Thus, while each intercostal nerve contributes certain tubular 

 fibres, each thoracic ganglion contributes gelatinous fibres. Sometimes these 

 two sets of fibres are kept distinct, and the splanchnic nerve consists obviously 

 of a white and a gray portion. The gelatinous fibres are considerably more 

 numerous at the lower than at the upper part of the splanchnic nerve, as point- 

 ed out by Mr. Beck, who very justly cites the fact as strongly confirmatory of the 

 statement that these fibres arise from the ganglia. Phil. Trans. 1846, p. 224. 



