6io TEXT-BOOK OF PHYSIOLOGY. 



The general arrangement of the sympathetic ganglia, their inter-connect- 

 ing cords and branches, is shown in Figs. 285 and 286. 



Structure of the Ganglia. Each ganglion consists of a capsule or 

 stroma of connective tissue in which are contained large numbers of nerve- 

 cells, nerve-fibers, medullated and non-medullated, and blood-vessels. 

 The nerve-cells give origin to two or more dendrites, which, perforating a 

 nucleated capsule by which each cell is surrounded, branch and rebranch and 

 interlace to form a pericapsular plexus. Each cell gives origin also to an axon, 

 which as it leaves the cell becomes invested with a sheath continuous with 

 the capsule surrounding the cell-body. It is, however, wanting in a medullary 

 sheath, and hence the nerve presents a gray color. Such a structure, in its 

 entirety, is known as a sympathetic neuron. 



The axonic processes as they emerge from the cells divide and sub- 

 divide forming ever smaller and smaller bundles which pass in different 

 directions to regions varying in position according to the situation of the 

 ganglion from which they come. The branches are conventionally termed 

 rami, communicantes or rami viscerales according as they become associated 

 with spinal nerves or pass directly to visceral structures. Whatever the route 

 they pursue, it has been shown by histologic and physiologic methods of 

 investigation that they are ultimately and directly distributed to but two 

 structures, viz., non-striated muscle and secretor epithelium. Moreover, there 

 is no evidence to warrant the assumption that these structures ever re- 

 ceive nerve impulses directly from the spinal or cranial nerves. All nerve 

 impulses that influence their activities, either in the way of augmentation 

 or inhibition, emanate directly though not primarily or originally from the 

 sympathetic ganglion cells. Since non-striated muscle-cells are found in 

 the walls of the blood-vessels, in the walls of hollow viscera and around 

 hair follicles, and since secretor epithelium is found in all glands there is 

 every reason to believe that the ganglia in some way are associated with 

 vaso-augmentor and vaso-inhibitor, mscero-augmentor and viscera-inhibitor, 

 secreto-motor and secreto-inhibitor, and pilo-motor phenomena. 



Structure of the Interconnecting Cords. The interconnecting cords 

 are composed of non-medullated and medullated nerve-fibers. The former 

 are the axons of cells found in the ganglia more centrally located; the latter, 

 as will be stated later, are derived from the spinal nerves, from the fibers of 

 which, however, they differ in character, being much smaller and finer. 

 The fibers of the interconnecting cords, as a rule, transmit nerve impulses 

 from the more centrally to the more peripherally located ganglia, and are 

 therefore termed rami efferentes. In the vertebral chain some of the cords 



cervical ganglion. 25, 26. Anterior branches of the seventh and eighth cervical and the first 

 dorsal nerves, sending filaments to the inferior cervical ganglion. 27. Middle cervical ganglion. 

 28. Cord connecting the two ganglia. 29. Inferior cervical ganglion. 30, 31. Filaments connect- 

 ing this with the middle ganglion. 32. Superior cardiac nerve. 33. Middle cardiac nerve. 

 34. Inferior cardiac nerve. 35, 35. Cardiac plexus. 36. Ganglion of the cardiac plexus. 37. 

 Nerve following the right coronary artery. 38, 38. Intercostal nerves, with their two filaments 

 of communication with the thoracic ganglia. 39, 40, 41. Great splanchnic nerve. 42. Lesser 

 splanchnic nerve. 43, 43. Solar plexus. 44. Left pneumogastric. 45. Right pneumogastric. 

 46. Lower end of the phrenic nerve. 47. Section of the right bronchus. 48. Arch of the aorta. 

 49. Right auricle. 50. Right ventricle. 51, 52. Pulmonary artery. 53. Right half of the 

 stomach. 54. Section of the diaphragm. (Sappey.) 



