ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 7H 



The thoracic portion is composed of twelve ganglia. 



The abdominal, or lumbar, part consists of four ganglia. 



The pelvic portion consists of five or six ganglia, including the 

 coccygeal ganglion. 



Two structures only finally receive the sympathetic fibers; that 

 is, involuntary muscular tissue and secretory epithelium. 



SYMPATHETIC NERVOUS SYSTEM. 



The ganglia lying on each side of the vertebral column are 

 lateral or vertebral ganglia. The prevertebral collateral ganglia are 

 the ganglia in advance of the vertebra, as the semilunar, inferior 

 mesenteric, etc. From the prevertebral ganglia, nerves go to the 

 terminal ganglia in the tissues. 



The efferent fibers of the sympathetic nervous system arise in 

 the intermedio-lateral column of gray cells. They pass out by the 

 anterior root from the spinal cord. From here they go by the white 

 ramus to a sympathetic ganglion. From the sympathetic ganglion 

 they may pass in two directions: (1) they may form synapses 

 about these cells, and from these cells new axons (postganglionic 

 fibers) may arise and pass outwards in the visceral nerves, or back, 

 through the gray ramus connected to the ganglion, into the spinal 

 or somatic nerve to the blood-vessels as vasomotor nerves, or sweat- 

 glands as secretory nerves, or to hairs as pilomotor nerves; (2) or 

 they may pass through the ganglion on to one situated more towards 

 the periphery, in which they form synapses and are continued 

 onward by new axons. These ganglia from which they do not pass 

 back to somatic nerves are called the prevertebral or collateral gan- 

 glia. These nervous fibers, after their interruption, proceed as gray 

 nonmedullated fibers to their termination, where they break up into 

 a network of anastomosing fibers, with cells or a sort of terminal 

 ganglion. When sympathetic nerve-fibers are interrupted in a gan- 

 glion, the fibers, before they meet the ganglia, are preganglionic ; 

 after they leave the ganglion, postganglionic. The number of nerves 

 leaving a ganglion is greater than the number of nerves entering it. 

 If the sympathetic fibers pass through the vertebral ganglia to be 

 interrupted in the prevertebral ganglia, then they are preganglionic, 

 and the fibers leaving the prevertebral ganglia are postganglonic. 

 By nicotine it can be determined if fibers end in a ganglion or pass 

 through it, for nicotine paralyzes the preganglionic terminals of the 

 nerve-cells of a ganglion, or, according to Langley, a special recep- 

 tive substance in the nerve-cell. 



