SECTION XVI 

 THE AUTONOMIC NERVOUS SYSTEM 



CHAPTER LI 

 THE SYMPATHETIC AND PARASYMPATHETIC SYSTEMS 



General Arrangement. It has been stated above that the nervous 

 system consists of a central and a peripheral division, and that the 

 latter in turn is built up of (a) the cranial and spinal nerves, and (6) 

 the ganglia and nerves of the sympathetic system. The term sympa- 

 thetic, however, is somewhat misleading, because, as originally em- 

 ployed, this system included merely those ganglia which are situated 

 along the spinal cord, beginning above with the superior cervical and 

 ending below with the coccygeal. Its function was said to be the 

 regulation of the activities of the internal organs or viscera. In the 

 course of time a number of ganglia have also been found which, al- 

 though innervating the viscera, do not occupy a position within the 

 realm of the sympathetic system as originally mapped out. These 

 are said to form the so-called parasympathetic system. On account 

 of this conflict, Langley 1 has advocated the use of the more general term 

 visceral or autonomic. Hence, in its modern conception the autonomic 

 nervous system is composed of a number of ganglia and plexuses of 

 nerves which are rather sharply differentiated from the cerebrospinal 

 system by certain anatomical, histological and physiological character- 

 istics. It is formed, on the one hand, by the sympathetic system as 

 originally conceived and, on the other, by certain ganglia which are 

 situated in the realm of the cranial and sacral nerves. The latter are 

 collectively known as the parasympathetic system. In making these 

 distinctions the student is cautioned not to regard the autonomic 

 system as a functional curiosity, or to separate it completely from the 

 cerebrospinal system, because it forms after all a closely correlated 

 ' division of the whole nervous mechanism. 



The entire autonomic nervous system is composed of a series of 

 ganglia which are scattered through the regions of the head, neck, 

 thorax, abdomen and pelvis, beginning above with the superior cer- 

 vical and terminating below with the coccygeal ganglion. These col- 

 onies of cells are united by nerve-fibers which are frequently augmented 

 into networks or plexuses. It consists of: 



1 Ergebn. der Physiol., ii, 1903, 2, and Zentralbl. fur Physiol., xxvii, 1913, 149. , 



627 



