516 SYSTEM OF THE GUEAT bYMPATHETIO. 



In the chest, the ganglia of the sympathetic nerve are situated on 

 each side the spinal column, just over the heads of the ribs, with 

 which they accordingly correspond in number. Their communi- 

 cations with the intercostal nerves are double ; each sympathetic 

 ganglion receiving two filaments from the intercostal nerve next 

 above it. The filaments originating from the thoracic ganglia are 

 distributed upon the thoracic aorta, and to the lungs and oesophagus. 



In the abdomen, the continuation of the sympathetic system con- 

 sists principally of the aggregation of ganglionic enlargements 

 situated upon the coeliac artery, known as the semilunar or ccdiac 

 ganglion. From this ganglion a multitude of radiating and inoscu- 

 lating branches are sent out, which, from their diverging course and 

 their common origin from a central mass, are termed the " solar 

 plexus." From this, other diverging plexuses originate, which 

 accompany the abdominal aorta and its branches, and are distri- 

 buted to the stomach, small and large intestine, spleen, pancreas, 

 liver, kidneys, supra-renal capsules, and internal organs of gene- 

 ration. 



Beside the above ganglia there are in the abdomen four other 

 pairs, situated in front of the lumbar vertebrae, and having similar 

 connections with those occupying the cavity of the chest. Their 

 filaments join the plexuses radiating from the semilunar ganglion. 



In the pelvis, the sympathetic system is continued by four or five 

 pairs of ganglia, situated on the anterior aspect of the sacrum, and 

 terminating, at the lower extremity of the spinal column, in a single 

 ganglion, the " ganglion impar," which is probably to be regarded 

 as a fusion of two separate ganglia. 



The entire sympathetic series is in this way composed of nume- 

 rous small ganglia which are connected throughout, first, with each 

 other ; secondly, with the cerebro-spinal system ; and thirdly, with 

 the internal viscera of the body. 



The properties and functions of the great sympathetic have been 

 less successfully studied than those of the cerebro-spinal system, 

 owing to the anatomical difficulties in the way of reaching and 

 operating upon this nerve for purposes of experiment. The cerebro- 

 spinal axis and its nerves are easily exposed and subjected to exami- 

 nation. It is also easy to isolate particular portions of this system, 

 and to appreciate the disturbances of sensation and motion conse- 

 quent upon local lesions or irritations. The phenomena, further- 

 more, which result from experiments upon this part of the nervous 

 apparatus, are promptly produced, are well-marked in character, 



