The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . Nerves toright arm. Nerves tofront ofright leg. Nerves toback ofright leg. Fig. 53.—Brain and spinal cord, with the thirty-one pairs of spinal nerves. in these organs. The brain is a very complex or^gan, being composed of several different ganglia,each of which has its own peculiar functions. Indescribing the nervous system it will b
The outlines of anatomy, physiology, and hygiene Being an edition of The essentials of anatomy, physiology, and hygiene, rev to conform to the legislation making the effects of alcohol and other narcotics upon the human system a mandatory study in public schools . Nerves toright arm. Nerves tofront ofright leg. Nerves toback ofright leg. Fig. 53.—Brain and spinal cord, with the thirty-one pairs of spinal nerves. in these organs. The brain is a very complex or^gan, being composed of several different ganglia,each of which has its own peculiar functions. Indescribing the nervous system it will be convenient,therefore, to begin with the sympathetic system, asbeing the simplest in its structure and functions. CHAPTER II. THE SYMPATHETIC SYSTEM. 257. Structure of the Sympathetic System.—The sympathetic system consists of a double chain of nerv-ous ganglia in the head, neck, and trunk, sendingfibres to various organs and to the blood-vesselsthroughout the body (Fig. 54). The arms and legs. Fig, 54.—The sympathetic system of uerves in the truiik. 200 ORGANS OF CO-ORDINATION. are organs of animal life, and are supplied with cere-bro-spinal nerves. The ganglia of the sympatheticvary very much in size, some being only visible withthe microscope, and others as large as a pea, or,rarely, even larger. They are composed, as hasbeen said, of gray nerve-matter, and are connectedwith each other and with the cerebro-spinal nervesby means of communicating fibers. Some of thesefibers are of the ordinary white matter, while othersare transparent and grayish in color, and appear toconsist of an axis-cylinder alone, without any sur-rounding myelin. The sympathetic ganglia all lievery deep in the cavities of the body, in the vicinityof and surrounding the important organs,^ whosefunctions they control, and it is very difficult to getat them for purposes of experiment. The conse-quence of this is, that very little has been learnedabout the real action of the sympathetic system,and man
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