First lines of physiology, being an introduction to the science of life; written in popular language . red bysome physiologists as a little independent brain, rulingover some of the organs in the same manner that thetrue brain seems to do over the frame in general. 288. The brain and ganglia are two most importantparts of the nervous system, and each little row ofglobules of medullary matter which they contain (283),may be regarded as a nervous filament; yet theseorgans are not commonly called nerves; that name beingreserved for another portion of the system which will bepresently described: t
First lines of physiology, being an introduction to the science of life; written in popular language . red bysome physiologists as a little independent brain, rulingover some of the organs in the same manner that thetrue brain seems to do over the frame in general. 288. The brain and ganglia are two most importantparts of the nervous system, and each little row ofglobules of medullary matter which they contain (283),may be regarded as a nervous filament; yet theseorgans are not commonly called nerves; that name beingreserved for another portion of the system which will bepresently described: they are often called nervous one extremity, each of the nerves in the body is con-nected either with the brain or a ganglion, from whenceit runs to be distributed to some distant part. It is thespecial function of each of the nervous centres to receiveinformation by means of certain nerves, of what is pass-ing in that portion of the frame over which it presides,and to issue through certain other nerves, the ordersnecessary to regulate the action of all the organs of thebody NERVOUS FILAMENTS AND TRUNKS. 143 289. A nerve is a bundle of medullary filaments (283)collected into a cord passing from the brain or from aganglion to some distant portion of the body, the func-tions of which are subject to its control. At fig. 36 yousee the representation of a portion of a very large Fig» 36. nerve with its fibres orfilaments, one of whichhas been drawn out by a pin. The whole cord a portion of nerve. is always covered by a strong sheath of cellular tissue strengthened with fibres,forming a membrane called the neurilema or nervouscoat, which would resemble a tube were all the fila-ments removed; and each particular fibre is enclosedin an extremely delicate sheath of the same kind ofmembrane. In this respect the nerves are arrangedlike the muscles (146). In fig. 36, the thick membranouscovering conceals the filaments, so that their dividedextremities alone are vis
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