ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



13 



bulbar autonomic and sacral autonomic systems. The fibers 

 from the midbrain arise in it, and go out in the third nerve and by 

 the short ciliary nerves to the sphincter of the iris and the ciliary 

 muscles, and cause their contraction. The fibers arising in the bulb 

 travel through the facial, glosso-pharyngeal, vagus, and the spinal 

 accessory. 



Cranial Ganglia. 



The ciliary ganglion of the fifth cranial nerve has preganglionic 

 sympathetic fibers from the motor oculi by a short root which 

 arborize about the ganglionic cells and when irritated contract the 

 pupil. The postganglionic fibers of this ganglion start from the 

 superior cervical ganglion through Die ciliary ganglion to contract 

 the blood-vessels of the iris and retina. 



Ccn'fral nerve cell. 



a. b. 



Fig. 288. (LANGLEY.) 



The number of fibers leaving a ganglion is greater than the number of fibers 

 entering it. This is due to the fact that the preganglionic fibers divide. 



The spheno-palatine ganglion of the fifth cranial nerve obtains 

 its preganglionic fibers from the facial. Its nerve-cells send post- 

 ganglionic fibers to the blood-vessels and glands of the mouth and 

 nose. Stimulation of this ganglion dilates the blood-vessels and aug- 

 ments secretion. 



The otic ganglion of the fifth cranial nerve obtains its pre- 

 ganglionic fibers from the ninth nerve by the pathway of Jacobson's 

 nerve and the small petrosal. The postganglionic fibers run in the 

 auriculo-temporal of the fifth, to increase the secretion of the parotid 

 gland and to dilate the blood-vessels. 



The submaxillary and the sublingual ganglia acquire their pre- 

 ganglionic fibers from the chorda tympani of the facial. Their post- 

 ganglionic fibers dilate the blood-vessels and increase the secretions 

 of these glands. 



