THE SYMPATHETIC SYSTEM 299 



The sacral and coccygeal ganglia supply the pelvic vessels. 



Properties. The ganglia and nerves are slightly sensitive. 

 Contraction of involuntary muscular tissue follows stimulation 

 not immediately, but after a considerable interval, and the sub- 

 sequent relaxation is tardy. Some of the ganglia are dependent 

 for power upon their fibers from the cerebro-spinal system, while 

 others seem capable of acting independently, at least for a time. 



Functions. Little is known of the functions of the sympa- 

 thetic except as regards efferent fibers. They are distributed in 

 general to the non-striped musculature of the circulatory appara- 

 tus and of the viscera, to secreting glands and to the heart. The 

 heart furnishes the only example of a direct sympathetic supply 

 to striated muscle. The sympathetic has a very definite effect 

 upon secretion, nutrition and the local production of heat. Sec- 

 tion of the sympathetic fibers going to any part causes hyper- 

 emia, an increased amount of secretion (sweat, e. #.), and a rise 

 of temperature in that part. The last two conditions are caused 

 by the first, and it in turn is due to a paralysis of the muscular 

 coat of the vessels, allowing an abrogation of their usual tonic 

 condition and, consequently, dilatation and an increased amount 

 of blood with exaggerated nutritive activity. This statement 

 confronts us with the question of vaso-motor action. 



Vaso-motor Phenomena. By vaso-motor nerves is meant 

 those fibers which convey to the muscular coat of the vessel 

 walls impulses causing them to contract and decrease the caliber, 

 or to relax and increase it. Those causing contraction are called 

 vaso-constrictors ; those causing relaxation vaso-dilators. It 

 is mainly through the operation of vaso-motor nerves that the 

 sympathetic system influences nutrition in a particular part, 

 though all vaso-motor fibers are not confined to the sympathetic 

 cords. However, it is not through the operation of the vaso- 

 motor nerves alone that the sympathetic lays claim to be the 

 "system of nutrition," for all the parts to which its other fibers 

 are distributed contribute also very materially to nutrition, 



