THE SYMPATHETIC NERVE SYSTEM. 569 



for the fore-limbs have their origin from cells in the stellate gang- 

 lion (first dorsal). After a short upward course they enter 

 the trunks of the nerves composing the brachial plexus. The 

 pre-ganglionic fibers come from the white rami of the fourth to the 

 ninth thoracic nerves. After entering the lateral chain they take 

 an upward direction and arborize around the cells of the stellate 

 ganglion. 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. In both 

 the brachial and sciatic nerves vaso-motor fibers (constrictors 

 and dilatators) and secretor nerves are present, as shown by 

 experimental methods (see page 331). 



The Functions of the Lumbo-sacral Portion. From the 

 ganglia of the lumbar and sacral regions gray rami enter the lumbar 

 and sacral nerves and accompany them to their distribution. In 

 the lumbar region the vertebral chain contains a number of pre- 

 ganglionic fibers which have descended from the thoracic region as 

 well as fibers which have come into the chain by the white rami from 

 the lumbar nerves themselves. Many of these fibers pass to the 

 inferior mesenteric ganglion, in which they find their cell station. 

 Fibers from the sacral cord pass into the hypogastric plexus. The 

 course and distribution of the individual nerves is complicated and 

 involved. In a general way it may be said that these two regions of 

 the lateral chain send viscero-motor and viscero-inhibitor, vaso-con- 

 strictor and dilator nerves to the pelvic viscera and to the external 

 organs of generation. Their function therefore is to regulate the 

 activities of the viscera as well as the blood-supply in accordance 

 with functional needs. 



The Functions of the Cephalic Ganglia. The ganglia situated 

 in the head are usually described in connection with and as con- 

 stituent 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 connective-tissue stroma containing nerve-cells. 

 From these cells post-ganglionic fibers emerge which, after a 



