7 i8 



SYMPATHETIC NERVOUS SYSTEM. 



SYMPATHETIC NERVOUS SYSTEM. 



Connected with the cerebrospinal system, the sympathetic occupies a special 

 position in consequence of the peculiarity of arrangement of its tracts, as well 

 as on account of the presence of non-medullated, gray fibers and characteristically 

 constructed ganglion-cells. The anterior branch of each spinal nerve gives off a 

 visceral branch (formerly designated communicating branch of the sympathetic) , 

 which is derived either from the anterior or the posterior root of the spinal nerve, 

 and this naturally (in the sense of Bell's law) indicates the function of the nerve. 

 All of the visceral branches collect on each side of the vertebral column to form the 

 sympathetic chain, in the course of which ganglionic nodes are interpolated. 

 From the first dorsal nerve downward there is a ganglion at the point where each 

 visceral branch enters the sympathetic. In the cervical portion a contraction 

 and partial coalescence of the ganglia has occurred, and the eighth and the 

 seventh and also the sixth and the fifth nerves are represented by single ganglia, 

 and the four upper cervical nerves together by the superior cervical ganglion. 

 Sympathetic filaments also pass through the path of individual visceral branches 

 from the sympathetic into the cerebrospinal nervous system. 



From the sympathetic system fibers pass to the various viscera of the head, 

 the chest and the abdomen, where again they form ganglionic plexuses, from 

 which finally fibers endowed with varied functions pass to the different organs. 



Visceral branches pass also from the 

 cerebral nerves (although demonstrable 

 with greater difficulty) and are con- 

 nected with ganglia. The ciliary gan- 

 glion belongs to the third nerve as a part 

 of the sympathetic system The 

 sphenopalatine nerves pass from the 

 second division of the trigeminus as 

 visceral branches into the sphenopala- 

 tine ganglion. The greater superficial 

 petrosal nerve also is to be considered 

 as a second visceral branch of this 

 ganglion. The otic ganglion is to be 

 looked upon as a sympathetic ganglion 

 of the third division; likewise the sub- 

 maxillary ganglion, the chorda tympani 

 being the visceral branch. It appears 

 that the glossopharyngeal, the vagus 

 and the hypoglossal have their visceral 

 branches in part in anastomotic fila- 

 ments that they send to the superior 

 cervical ganglion, which, therefore, 

 gives off these cerebral nerves, together 

 with the four upper cervical nerves, to 

 the common ganglion. 

 The sympathetic consists: (i) Of medullated fibers supplied to it as visceral 

 branches by cerebral and spinal nerves, and (2) of fibers of Remak, which arise 

 from sympathetic ganglia. The medullated fibers are (a) sensory, (6) motor, for 

 vessels (vasomotors) and viscera, the latter entering into sympathetic ganglia, 

 whence Remak's fibers, as well as medullated fibers, pass from the ganglion-cells 

 to the innervated areas; (c) inhibitory fibers and vasodilators, in the course of 

 which no sympathetic ganglia are intercalated. The fibers of Remak are all 

 motor and they innervate directly or indirectly (that is entering again into ganglia) 

 the unstriated musculature of the vessels, the viscera, the skin, and the muscles 

 of the heart. 



The conduction of the sympathetic nerve-fibers is in part direct and uninter- 

 rupted by means of sensory, inhibitory and vasodilator fibers. The medullated 

 motor fibers from the visceral branches conduct indirectly, that is they pass at 

 first in sympathetic ganglia, where they surround the cells, whose neurites then 

 continue the conduction. The sympathetic contains further secretory fibers and 

 fibers that control chemical processes, as in the thyroid gland and the adrenals. 

 According to Langley all motor and sensory tracts derived from the spinal cord 

 and situated in the sympathetic make their exit from the cord between the first 

 dorsal and the second lumbar nerve. 



FIG. 249. Diagrammatic Representation of the Course 

 of a Thoracic Branch of the Sympathetic: i, spinal 

 cord; 2, ventral root; 3, dorsal root with spinal 

 ganglion; 4, intercostal nerve; 5, dorsal branch; 

 6, visceral branch; 7, ganglion of the sympathetic 

 cord; 8, lateral cutaneous branch (pectoral and 

 abdominal); a, posterior branch; b, anterior 

 branch; 9, anterior cutaneous branch (pectoral 

 and abdominal). 



