GENERAL INTRODUCTION. GENTLEMEN: The subject of the nervous system, which has been chosen as the theme of my winter's course of lectures, is one which probably comprises more points of practical interest than any other portion of anatomy. I say of practical interest, because there is hardly a field of medicine or of surgery where the nervous system does not help to explain many of the symptoms which might otherwise tend to possibly mislead the practitioner, and where it does not also afford invaluable aid in the diagnosis of obscure affections which might remain unrecognized, without a knowledge of the nerves and of their distribution and function, till the opportunity of relief to the patient has passed. The distribution of those small nerve-filaments which supply the skin of the body with sensation, and thus allow of the perception of external impressions, such as those of heat, cold, pain, and touch, possesses to-day an importance which is not confined to the researches of the physiologist, but which the advanced physician and surgeon are both keenly alive to grasp in all its practical detail. In every work now published upon diseases of the nervous system, you will find cuts, which, in less modern treatises, have no analogue. These are designed to show the situation of certain motor points on the cutaneous surface of the different anatomical regions of the body, where the electric current can be best applied to accomplish certain desired effects, and also the area of cutaneous distribution of each of the sensory nerves. The important relationship which exists between the nerves of the skin, the muscles underneath it, and the joints which those muscles move, is affording the enlightened physician a means of tracing the seat of obscure affections, by the use of certain general rules governing the nerve-supply of the body, with a degree of accuracy and ease which strikes those not familiar with the method as remarkable. 8 The investigations of Meynert,' Türck,' Charcot,' Ferrier,* Brown-Séquard,' Clarke,' Flechsig,' Luys, Broca,' Bouillaud," Andral," and a host of others, have awakened the profession to the fact that many of the old ideas of the anatomy and physiology of the brain and the spinal cord were radically wrong. By symptoms referable to certain anatomical regions, the existence of disease in certain corresponding parts of the brain or spinal cord may now be positively localized during life. To what extent this new guide to diagnosis, given us by means of investigations calculated to determine the precise distribution of the nervous system, may be developed in the future, time alone will show. We have, however, ample proof that some positive information of a practical character has been gained, and that a great advance has been made toward accurate knowledge of the anatomy of the nervous centers. When we consider that every act which distinguishes the animated being from the corpse is dependent upon the influence of the nerves, and that, without these electric wires, the heart would cease to throb, the lungs no longer perform their "The Brain of Mammals," "Stricker's Histology," New York, 1872. A paper originally read before the Academy of Vienna in 1851. 3" Localizations dans les maladies cérebrales." 4" Functions of the Brain"; "Localization of Cerebral Disease." 5" Lectures on the Physiological Pathology of the Brain," "Lancet," 1876–77. 6" Researches on the Intimate Structure of the Brain," "Phil. Trans.," London, 1858 and 1868. "Die Leitungsbahnen im Gehirn und Rückenmark des Menschen." 10" Recherches expérimentales sur les fonctions du cerveau." gie," Paris, 1830. “Traité de l'Encéphalite," Paris, 1825. 11" Clinique Médicale." "Jour. de Physiolo GENERAL INTRODUCTION. 5 function, the eye no longer be capable of vision, the ear no longer perceive sound, and that smell, taste, expression, and movement would cease to exist, we can then understand how much of physiological interest must center around this special study, and how necessary is the thorough understanding of the distribution and function of the individual nerves, if we ever hope to attain a comprehensive grasp of the general plan of our construction. During the last session, I closed my course of lectures with a description of the general construction of nerves and the anatomy of the human brain. It will assist us, in our study of the distribution and practical utility of the separate nerves of the body, to hastily review the main classifications of nerves and the general plan upon which the nervous system is formed. The nervous system of the human race consists of the following component parts: The cerebro-spinal axis. 1st. Cerebro-spinal system. The motor nerves. The sensory nerves. 2d. The sympathetic nerve and its vaso-motor connections. 3d. Various ganglia, connected with special nerves. FIG. 1.—Nerve fibers from the human subject; magnified 350 diameters. (Kölliker.) Four small fibers, of which two are varicose, one medium-sized fiber with borders of single contour, and four large fibers; of the latter, two have a double contour and two contain granular matter. 45 54 FIG. 2. Cervical and thoracic portion of the sympathetic. (Sappey.) 1, 1, 1, right pneumogastric; 2, glosso-pharyngeal; 3, spinal accessory; 4, divided trunk of the sublingual; 5, 5, 5, chain of ganglia of the sympathetic; 6, superior cervical ganglion; 7, branches from this ganglion to the carotid; 8, nerve of Jacobson; 9, two filaments from the facial, one to the spheno-palatine and the other to the otic gan glion; 10, motor oculi externus; 11, ophthalmic ganglion, receiving a motor filament from the motor oculi communis and a sensory filament from the nasal branch of the GENERAL INTRODUCTION. 7 fifth; 12, spheno-palatine ganglion; 13, otic ganglion; 14, lingual branch of the fifth nerve; 15, submaxillary ganglion; 16, 17, superior laryngeal nerve; 18, external laryngeal nerve; 19, 20, recurrent laryngeal nerve; 21, 22, 23, anterior branches of the upper four cervical nerves, sending filaments to the superior cervical sympathetic ganglion; 24, anterior branches of the fifth and sixth cervical nerve sending filaments to the middle 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 connecting 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. The CEREBRO-SPINAL SYSTEM includes, as its first component part, those nerve-centers inclosed within the cavities. of the cranium and spinal column, viz., the cerebrum, cerebellum, crus, pons Varolii, medulla oblongata, and spinal cord. The second component part of the system, viz., the motor nerves, are efferent nerves, which carry the impulses of the nerve-centers to the muscles. The third component part, the sensory nerves, are afferent nerves, which carry only sensory impressions from the periphery of the body to the nerve-centers, viz., to the brain or spinal cord. The cerebro-spinal nerves are usually found in company with the larger blood-vessels. They are protected from injury either by investing muscular layers, or, when near the surface, by the lines of flexion of the joints. It is worthy of remark that the foramina of exit of the cranial nerves from the base of the skull are less liable to variation than those for the transmission of blood-vessels. The SYMPATHETIC NERVE' comprises a continuous chain of nerve-fibers and ganglionic enlargements, which extends from the head to the coccyx, on both sides of the spinal column, and which is in constant communication along its course with branches of the cerebro-spinal system of nerves. It supplies branches to various ganglia of the thorax and abdomen, and helps to form plexuses of nerves which ramify upon 1 See Fig. 2 and Fig. 3. |