CHAPTER XII. 



THE SYMPATHETIC OR AUTONOMIC NERVOUS 

 SYSTEM. 



The chain of nerve ganglia extending on each side of the spinal 

 column to the coccyx is known as the sympathetic nervous system. 

 This name was given to the structure under the misapprehension 

 that it constitutes a nerve pathway through which so-called sym- 

 pathetic or, as we now designate them, reflex actions of distant 

 organs are effected. It was supposed to arise from the brain by 

 branches connected with the fifth and sixth cranial nerves.* We 

 now know that this system consists of a series of ganglia or col- 

 lections of nerve cells connected with each other and connected also 

 with the spinal nerves. Strictly speaking, the term sympathetic 

 system is applicable only to the chain of ganglia which begins with 

 the superior cervical ganglion at the base of the skull and ends 

 with the ganglion coccygeum. There are, however, other outlying 

 nerve ganglia with or without specific names which from a physio- 

 logical and indeed from an anatomical standpoint belong to the same 

 group. In the abdomen we have the so-called prevertebral ganglia, 

 the semilunar ganglion from which arises the celiac plexus, the 

 superior mesenteric, and the inferior mesenteric ganglion giving 

 rise to the hypogastric nerve. These ganglia lie ventral to the 

 sympathetic trunk, but are in direct connection with it. In the 

 head region the ciliary, sphenopalatine, and otic ganglia are 

 also of the same type. More peripherally are numerous other 

 ganglia lying in or around the various visceral organs, such as the 

 submaxillary ganglion near the duct from the corresponding gland, 

 the cardiac ganglia in the heart, and the extensive system of nerve 

 cells in the walls of the alimentary canal known as the plexuses 

 of Meissner and Auerbach. With the exception, perhaps, of this 

 last system, whose histological structure and connections are not 

 satisfactorily known, all of these ganglia are frequently designated 

 as sympathetic, and from a physiological as well as an anatomical 

 standpoint may be considered with the ganglia of the sympathetic 

 trunk or chain. Langley, who has contributed greatly to our 

 knowledge of the finer anatomy and the physiology of this system, 

 has recently proposed a different classification.! 



* Charles Bell, " The Nervous System of the Human Body," third edi- 

 tion, London, 1844, p. 9. 



fSchafer's "Text-book of Physiology," 1900, vol. ii ; " Ergebnisse der 

 Physiologie," 1903, vol. ii, part n, p. 823 ; also " Brain," 1903, vol. xxvi. 



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