206 INNERVATION. [CHAP. viu. 



The remainder of the nervous system is made up entirely of 

 ganglions, with their connecting cords and nerves', which ramify in 

 a plexiform manner among various internal viscera, and upon the 

 coats of blood-vessels. In the higher vertebrate animals, it is dis- 

 posed as a chain of ganglia on each side of the vertebral column, 

 and at the base of the skull near the foramina through which the 

 spinal and encephalic nerves pass out ; and at all these situations it 

 forms a very intimate connexion with the brain and spinal cord. 

 This portion of the nervous system possesses many peculiarities, 

 both in its composition, in its arrangement, and in its connexion 

 with the organs among which its nerves ramify, which, at least, 

 entitle it to be considered apart from the cerebro-spinal system. 

 How far it can be regarded as independent of that system, is a 

 question which must be reserved for future examination. This is 

 the sympathetic or ganglionic system, formerly known and described 

 as the great intercostal nerve, and by Bichat as the nervous system of 

 organic life : it has also been called the visceral nerve. All these 

 titles are liable to objection, inasmuch as each involves to a greater 

 or ]ess extent some theory of the uses or actions of these nerves ; 

 but the two first mentioned are preferable, as those which are best 

 known, and most confirmed by use. 



The nervous system, then, in man and the vertebrate series, con- 

 sists of the brain, spinal cord, and the nerves associated therewith, 

 the cerebro-spinal system ; and that double chain of ganglia, with 

 their nerves, situate along the spinal column, the sympathetic or 

 ganglionic system. Among the invertebrata, although the arrange- 

 ment of the nervous system differs very materially from that in the 

 vertebrata, an analogous subdivision of it may be made in a large 

 proportion of those classes, the anatomy of which has been satisfac- 

 torily made out. 



Physical and Chemical Properties of the Nervovs Matter. The 

 nervous matter of both kinds is a soft, unctuous substance, easily 

 disturbed by slight mechanical force. Were it not associated with 

 other tissues, and supported to a certain extent, by the blood- 

 vessels which ramify among its elements, its physical tenacity 

 would be very feeble. 



Its great softness is due, in part, to the admixture of a large 

 quantity of water with it, which constitutes three-fourths, or four- 

 fifths, and, in many instances, seven-eighths, of its weight. Ac- 

 cording to Vauquelin, whose analysis was made in 1812, the brain 

 is an emulsive mixture of albumen, fatty matter, and water : the 

 last holding in solution certain saline and other ingredients commo 



