6i8 TEXT-BOOK OF PHYSIOLOGY. 



which they find their cell station. For this reason these nerves are sometimes 

 termed the injerior splanchnics. Stimulation of these nerves as well as of the 

 ganglion and its branches gives rise to contraction of the blood-vessels of the 

 pelvic viscera, contraction of the detrusor muscle of the bladder, contraction 

 of the muscle-fibers of the uterus and vagina, and inhibition of the circular 

 and longitudinal fibers of the large intestine. 



The cutaneous nerves for the hind-limbs are derived from the lower 

 lumbar and the upper sacral ganglia. They also enter the spinal nerves 

 by the gray rami and pass to the blood-vessels and glands of the skin. The 

 pre-ganglionic fibers come from the twelfth thoracic to the third lumbar 

 nerves. 



The phenomena that follow stimulation of this portion of the vertebral 

 sympathetic chain resemble in a general way those that follow stimulation 

 of the thoracic portion for the reason that the post-ganglionic fibers are dis- 

 tributed to similar structures. Thus from the lumbar and upper sacral 

 ganglia gray rami enter the lumbar and sacral nerves to be distributed 

 ultimately to the blood-vessels and sweat glands of the skin of the hip and 

 leg. Stimulation, therefore, of these nerves gives rise to contraction of the 

 blood-vessels and a secretion of sweat of the corresponding parts. If the 

 stimulation with the induced current be slow, dilatation of blood-vessels 

 may also be observed, a fact that indicates that these nerves also carry 

 vaso-dilatator fibers. The pre-ganglionic fibers descend the vertebral chain 

 having entered it mainly from the lumbar nerves. Stimulation, therefore, 

 of the lumbar chain gives rise to the same effects as stimulation of the 

 post-ganglionic fibers. 



The Functions of the Peripheral Ganglia. The ganglia situated in the 

 head are usually described in connection with and as constituent parts of the 

 cranial nerve system. They, however, bear the same relation to the cranial 

 nerves that the ganglia of the trunk bear to the spinal nerves. They consist 

 of ganglion cells from which post-ganglionic fibers pass to glands, blood- 

 vessels, and non-striated muscles, and to which pre-ganglionic fibers pass 

 from the cranial nerves. Motor and sensor nerves pass through one or 

 more ganglia, though they have no anatomic connection with them. In 

 their structure, distribution, and functions they closely resemble the col- 

 lateral ganglia of the abdominal sympathetic: 



i . The ciliary or ophthalmic ganglion is situated in the orbital cavity posterior 

 to the eyeball. It is small in size, gray in color, and consists of a con- 

 nective-tissue stroma containing nerve-cells. From these cells post- 

 ganglionic fibers emerge which, after a 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 ana- 

 tomic 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 ganglion 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 accom- 

 modation of the eye for near vision. Division of these fibers is followed 

 by the opposite results. Post-ganglionic fibers from the superior cervical 

 ganglion which come through the cavernous plexus pass through 



