THE SYMPATHETIC SYSTEM. 585 



The continuation of the sympathetic nerve in the neck consists of 

 two and sometimes three ganglia, the superior, middle, and inferior. 

 These ganglia communicate with each other, and also with the anterior 

 branches of the cervical spinal nerves. Their filaments follow the 

 course of the carotid artery and its branches, and are distributed to the 

 substance of the thyroid gland, and to the walls of the larynx, trachea, 

 pharynx, and oesophagus. By the superior, middle, and inferior cardiac 

 nerves they also supply sympathetic fibres to the cardiac plexus, and, 

 through it, to the substance of the heart. 



In the chest, the sympathetic ganglia are situated on each side the 

 spinal column, just over the heads of the ribs. Their communications 

 with the spinal nerves in this region are double ; each ganglion receiving 

 two filaments from the intercostal nerve next above it. The filaments 

 originating from the ganglia are distributed upon the thoracic aorta, 

 and to the lungs and oesophagus. 



In the abdomen, the continuation of the sympathetic S3 7 stem consists 

 mainly of the aggregation of ganglionic enlargements situated upon the 

 coeliac artery, known as the semilunar or cceliac ganglion. From this 

 ganglion a multitude of radiating and inosculating branches are sent out, 

 which, from their common origin and their diverging Bourse, are termed 

 the " solar plexus." From this, other plexuses originate, which accom- 

 pany the abdominal aorta and its branches, and are distributed to the 

 stomach, small and large intestine, spleen, pancreas, liver, kidneys, 

 supra-renal capsules, and internal organs of generation. 



Beside the above ganglia there are in the abdomen four other pairs, 

 situated in front of the lumbar vertebrae. 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 terminat- 

 ing, at the lower extremity of the spinal column, in the u ganglion impar," 

 which is probably to be regarded as a fusion of two separate ganglia. 



The entire sympathetic series is thus composed of numerous small 

 ganglia connected throughout, first with each other; secondly, with the 

 cerebro-spinal system ; and thirdly, with the viscera. 



Physiological Properties of the Sympathetic Ganglia and Nerves. 

 The properties and functions of the sympathetic nerves have been less 

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

 perhaps, to the anatomical difficulties in the way of reaching and ope- 

 rating upon them for purposes of experiment The principal part of 

 the sympathetic S3^stem is situated in the interior of the chest and abdo- 

 men ; and the mere opening of these cavities, to reach the ganglionic 

 centres, causes such a disturbance in the functions of vital organs, and 

 such a shock to the system fit large, that the results of these experiments 

 are liable to be more or less unsatisfactory, The connections of the sym- 

 pathetic ganglia with each other and with the cerebro-spinal axis are so 

 numerous and scattered, that these ganglia cannot be completely isolated 

 without resorting to a still more extensive operation. And finally, the 

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