sympathetic ganglion. (Figures 10 and 11). POSTERIOR ROOT ANTERIOR ROOT FIG. 10. Cross section of spinal cord and roots of spinal nerves, with anterior root cut; also showing ganglion on posterior root. FIG. 11. Shows the manner in which the brachial plexus of nerves in the neck branches from the spine. The spinal cord consists partly of white matter and partly of gray; the gray portion, occupying the center of the cord, is arranged somewhat in the form of the letter H, with the two upright prongs curv ing outward at both ends, (Fig. 10). The white matter entirely surrounds the gray matter. Nerve cells are scattered throughout the gray matter of the cord, but they are arranged, more or less distinctly, in groups. Effort is being made by surgeons to safely get within the spinal column, and reach the posterior nerve, so that an anesthetic may be applied to this nerve, so deadening it that no sensation can be received in the spinal cord, nor conveyed by the spinal nerves to the brain. This power of sensation being deadened, the operation might be performed with the entire consciousness of the individual, yet without pain. As the nerve fibres of the trunk and the extremities reach the upper end of the spinal cord, they cross so that the nerves of the right side of the body enter the left side of the brain, and conversely-the nerves on the left side of the body enter the right side of the brain, thus in case of paralysis or a hemorrhage of the right side of the brain we look for a paralysis in the left side of the body. The double chain of nerve ganglia, Sympathetic Nerves extending on each side of the spinal column, and in front of it, from the base of the skull to the coccyx is known as the Sympathetic Nervous System proper. The sympathetic system, as the name implies, regulates the sympathy and the harmony between the different organs; it regulates the involuntary processes of organic life, or the acts beyond our control, such as certain processes of digestion, the cells of the liver, the pancreas, the spleen, etc. It is materially affected by the character of thought and emotion. It consists of a series of ganglia, or collections of nerve cells connected with each other, and connected also with the spinal nerves. Physiologically and anatomically belonging to the same group, are various nerve ganglia about the visceral organs, such as the submaxillary ganglion near the submaxillary duct, the cardiac ganglia in the heart, extensive system of 1 cells in the walls of the alimentary canal, the prevertebral ganglia in the abdomen, the semilunar ganglion from which arises the celiac plexus, and the superior mesenteric and the inferior mesenteric ganglia, which give rise to the hypogastric nerve, see Fig. 12. These ganglia lie ventral to the sympathetic nerve chain but they are in direct connection with it. The sympathetic nerves lie so deeply imbedded within the body that it is difficult to get at them for experiment. They do not extend to the muscles of the extremities; but they send branches to all organs of the thorax, abdomen and pelvis; they also give off fibres to the nerves coming from the brain and the spinal cord. The ganglia of these nerves vary greatly in size, some being invisible to the naked eye and others as large as a pea, occasionally even larger; while connected with the cerebro spinal nerves by communicating fibres, each nerve ganglion is connected with the other in the form of a complex chain, as illustrated by Figure 12. They surround the important vital organs and |