THE SYMPATHETIC NERVE SYSTEM. 619 



the ciliary ganglion to the blood-vessels of the iris and retina and are 

 vaso-constrictor in function. Sensor fibers from the peripheral division 

 of the fifth nerve pass to the cornea and endow it with sensibility. 



2. The spheno-palatine ganglion is situated in the spheno-maxillary fossa. 



Its nerve-cells send non-medullated post-ganglionic fibers to the blood- 

 vessels and glands of the mucous membrane of the nasal and oral 

 regions. Stimulation of the ganglion gives rise to dilatation of the blood- 

 vessels and increase of secretion in this entire region. The pre-ganglionic 

 fibers are derived from the seventh or facial nerve by way of the great 

 petrosal. Sensor fibers from the superior maxillary division of the 

 fifth nerve pass through the ganglion to the same regions. 



3. The otic ganglion is situated just below the foramen ovale and internal 



to the third division of the fifth nerve. The post-ganglionic fibers 

 pass to the parotid gland by way of the auriculo-temporal division of the 

 fifth nerve, and to the blood-vessels of the mucous membrane of the 

 lower lip, cheek, and gums. The pre-ganglionic fibers are derived from 

 the efferent fibers in the glosso-pharyngeal or ninth nerve, by way of 

 Jacobson's nerve and the small petrosal. Stimulation of these nerves 

 in any part of their course gives rise to vascular dilatation and increase 

 of secretion in the region of the distribution. Motor fibers from the 

 small or motor root of the fifth nerve pass through this ganglion to the 

 tensor tympani muscle. 



4. The submaxillary and sublingual ganglia are situated close to the corre- 



sponding glands. Their post-ganglionic fibers pass to the blood-vessels 

 and gland-cells. The pre-ganglionic fibers are derived from the seventh 

 or facial nerve through the chorda tympani branch. Stimulation of the 

 chorda or of the ganglia themselves gives rise to marked dilatation of 

 the blood-vessels and an increased flow of saliva. It therefore contains 

 vaso-dilatator and secretor fibers for these glands. Vaso-constrictor 

 and a few secretor nerves, it will be recalled, come to these glands from 

 the superior cervical ganglion. 



5. The cardiac ganglia are situated in different regions in the walls of the 



heart; their visceral branches are distributed directly to the heart 

 muscle-cells. Stimulation of these ganglia inhibit the action of the heart. 

 The pre-ganglionic fibers for these ganglia are contained in the trunk 

 of the vagus (pages, 305, 599). Stimulation of the vagus has a 

 similar inhibitor action on the heart. 



6. The pelvic ganglia, lying at the base of the bladder are by reason of their 



position and relations somewhat inaccessible to direct experimentation. 

 The pre-ganglionic fibers in connection with them are contained in part 

 in the pudendal or pelvic nerve. Stimulation of the post-ganglionic and 

 of the pre-ganglionic nerves gives rise to a marked dilatation of the blood- 

 vessels of the penis, clitoris, vulva, contraction of the muscles of the 

 bladder, rectum, etc. 



