THE SYMPATHETIC SYSTEM. 497 



of the sympathetic, and to the cardiac plexus, afford a striking instance 

 of the same kind. 



The ganglia on the spinal and cranial nerve roots are undoubtedly 

 analogous, in their anatomical relations, to those of the sympathetic 

 system ; and this system may be considered as made up of nervous 

 centres disseminated through the great cavities of the body, and con- 

 necting filaments which receive fibres from the cerebro-spinal nerves 

 and supply to these nerves fibres of their own. All the organs in the 

 body, accordingly, contain nerve fibres from both sources ; the differ- 

 ence consisting in the relative numbers of one kind or the other in par- 

 ticular parts. The cerebro-spinal nerves are in greatest abundance, 

 and manifest their most striking properties, in the organs of animal 

 life ; those of the sympathetic system preponderate in the organs of 

 nutrition, and in their influence on the functions of circulation, secre- 

 tion, and growth. 



General Arrangement of the Sympathetic System. The central part 

 of the sympathetic system is a double chain of ganglia, on the sides 

 of the spinal column, united with each other by longitudinal filament^ 

 Each ganglion is connected, by motor and sensitive fibres, with the 

 cerebro-spinal system. Its nerves are distributed to glands and mucous 

 membranes, mostly destitute of general sensibility, and to muscular 

 fibres which are independent of the will. The sympathetic ganglia 

 are situated in the head, neck, chest, and abdomen ; and in each of 

 these regions are connected by their nerves of distribution with special 

 organs. 



The first sympathetic ganglion in the head is the ophthalmic ganglion, 

 in the orbit of the eye, on the outer aspect of the optic nerve. It com- 

 municates by slender filaments with the carotid plexus of sympathetic 

 nerves, receives a motor root from the oculomotorius, and a sensitive 

 root from the ophthalmic division of the fifth pair. Its filaments of dis- 

 tribution, known as the "ciliary nerves," pass forward upon the eye- 

 ball, pierce the sclerotic, and terminate in the iris. 



The next is the spheno-palatine ganglion, in the spheno-maxillary 

 fossa. It communicates, like tHe preceding, with the carotid plexus, 

 receives a motor root from the facial nerve, and a sensitive root from 

 the superior maxillary division of the fifth pair. Its filaments are dis- 

 tributed to the levator palati and uvular muscles, to the mucous mem- 

 brane of the posterior part of the nasal passages, and to that of the 

 hard and soft palate. 



The third is the submaxillary ganglion, connected with the submax- 

 illary gland. It communicates with the superior cervical ganglion of 

 the sympathetic by filaments accompanying the external carotid and 

 facial arteries. It derives its sensitive filaments from the lingual 

 branch of the fifth pair, and its motor filaments from the facial nerve, 

 by the chorda tympani. Its branches of distribution pass mainly to 

 the submaxillary gland and duct. 



The last sympathetic ganglion in the head is the otic ganglion, situ- 



2G 



