NEUROLOGY. 







THE Nervous System is the most complicated and highly organized of the various 

 systems which make up the human body. It is the mechanism concerned 

 with the correlation and integration of various bodily processes and the reactions 

 and adjustments of the organism to its environment. In addition the cerebral 

 cortex is concerned with conscious life. It may be divided into two parts, central 

 and peripheral. 



The central nervous system consists of the encephalon or brain, contained within 

 the cranium, and the medulla spinalis or spinal cord, lodged in the vertebral canal ; 

 the two portions are continuous with one another at the level of the upper border 

 of the atlas vertebra. 



The peripheral nervous system consists of a series of nerves by which the central 

 nervous system is connected with the various tissues of the body. For descriptive 

 purposes these nerves may be arranged in two groups, cerebrospinal and sympathetic, 

 the arrangement, however, being an arbitrary one, since the two groups are inti- 

 mately connected and closely intermingled. Both the cerebrospinal and sym- 

 pathetic nerves have nuclei of origin (the somatic efferent and sympathetic efferent) 

 as well as nuclei of termination (somatic afferent and sympathetic afferent) in the 

 central nervous system. The cerebrospinal nerves are forty-three in number on 

 either side twelve cranial, attached to the brain, and thirty-one spinal, to the 

 medulla spinalis. They are associated with the functions of the special and gen- 

 eral senses and with the voluntary movements of the body. The sympathetic 

 nerves transmit the impulses which regulate the movements of the viscera, 

 determine the caliber of the bloodvessels, and control the phenomena of secre- 

 tion. In relation with them are two rows of central ganglia, situated one on 

 either side of the middle line in front of the vertebral column; these ganglia are 

 intimately connected with the medulla spinalis and the spinal nerves, and are also 

 joined to each other by vertical strands of nerve fibers so as to constitute a pair 

 of knotted cords, the sympathetic trunks, which reach from the base of the skull 

 to the coccyx. The sympathetic nerves issuing from the ganglia form three great 

 prevertebral plexuses which supply the thoracic, abdominal, and pelvic viscera; 

 in relation to the walls of these viscera intricate nerve plexuses and numerous 

 peripheral ganglia are found. 



STRUCTURE OF THE NERVOUS SYSTEM. 



The nervous tissues are composed of nerve cells and their various processes, 

 together with a supporting tissue called neuroglia, which, however, is found only 

 in the brain and medulla spinalis. Certain long processes of the nerve cells are of 

 special importance, and it is convenient to consider them apart from the cells; 

 they are known as nerve fibers. 



To the naked eye a difference is obvious between certain portions of the brain 

 and medulla spinalis, viz., the gray substance and the white substance. The gray 

 substance is largely composed of nerve cells, while the white substance contains 

 only their long processes, the nerve fibers. It is in the former that nervous impres- 

 sions are received, stored, and transformed into efferent impulses, and by the latter 

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