57 o TEXT-BOOK OF PHYSIOLOGY. 



short course forward, penetrate the eyeball and terminate in the 

 circular fibers of the iris and the ciliary muscle. Pre-ganglionic 

 fibers of small size, and similar in their anatomic features to 

 the fibers of the white rami of the spinal nerves, leave the motor 

 oculi by a short root from the inferior division and arborize 

 around the ganglionic cells. Stimulation of the pre-ganglionic 

 fibers gives rise to contraction of the circular fibers of the 

 iris, with a diminution in the size of the pupil, and contraction 

 of the ciliary muscle with accommodation of the eye for near 

 vision. Division of these fibers is followed by the opposite 

 results. Post-ganglionic fibers from the superior cervical gang- 

 lion which come through the cavernous plexus pass through the 

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

 are vaso-constrictor in function. Sensor fibers from the per- 

 ipheral 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-gang- 

 lionic fibers pass to the parotid gland by way of the auriculo- 

 temporal division of the fifth nerve, and to the blood-vessels of the 

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

 rived from the efferent fibers in the glosso-pharyngeal or ninth 

 nerve, by way of Jacobsen's nerve and the small petrosal. Stimu- 

 lation of these nerves in any part of their course gives rise to 

 vascular dilatation and increase of secretion in the region of 

 their distribution. Motor fibers from the small or motor root 

 of the fifth nerve pass through this ganglion to the tensor tym- 

 pani muscle. 



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



corresponding 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 



