SYNIPATTIETIC NERVOUS composed of (a) two series of ganglia which are eonneet441 with one another by nerve and extend along either side of the vertebral column front the base of the skull to the coccyx: (h) plexuses. three in immlwr, which lie in front of the spine in the thoracic, abdominal. and pelvic cavities; (e) smaller ganglia which are situated in or upon various viscera (d) nerve fibres which serve lo connect the ganglia with one an other, with the cerebrospinal system. and with e periphery.
The series of ganglia is known as the gangli ated cord and may be subdivided into three cer vical, twelve dorsal, four lumbar, and five sacral ganglia. In the neck these ganglia lie upon the transverse processes of the vertebra-, in t he thorax upon the heads of the ribs, in the abdo men and pelvis, upon the bodies of the and upon the sacrum. As the two cords pass into the pelvis they unite in a ganglion called the ganglion impar, in front of the coccyx. Superi orly, the gangliated cord is continued into the sympathetic plexus on the en rolid artery. this plexus being connected by filaments with the lower cranial nerves. The ganglia are connected with one another by bundles composed of inter mingled gray fibres and white fibres, the white fibres being derived from the spinal nerves. The branches which connect the sympathetic ganglia With the cerebrospinal are composed of both white fibres (medullated) and gray fibres The former are derived from the eerebro-spinal axis and pass to the sympa thetic, the latter originate in the sympathetic system and end in the eerebro-spinal.
The throe great gangliated are known respectively as the cardiac, the solar or epiga5 trie, and the hypogastrie. They are composed of nerve fibres and ganglia, the former coining front the cerebrospinal nerves and from t lie gangliated cord. The cardiac. plexus consists of a superficial portion which lies in the concavity beneath the arch of the aorta, and of a deep portion situated between the aorta and trachea.
The solar plexus is the great plexus of the ab domen and supplies all the abdominal viscera. it is subdivided into several smaller plexuses, the names of which sufficiently indicate their location and distribution. They are known as the aortic plexus, the coeliac plexus, the phrenie (dia phragmatic) plexus, the supra-renal plexus, the renal plexus, the spermatic plexus. and the superior mesenteric plexus. The hypogast•ic plexus lies on the front of the sacrum between the two common iliac arteries. Ilelow• the hypo gast•ic plexus is continued into the pelvic plexus, which is situated at the side of the rectum and bladder in the male: of the rectum, vagina, and bladder in the female. It sends to all the pelvic viscera and gives rise to the following suhanIiau•y plexuses, the inferior hemorrhoidal, the prostatic, the vesicle, and in the female the uterine and vaginal.
Smaller ganglia are situated in certain viscera, notably in the heart, stomach. intestines, and uterus. They are mostly microscopic in size.
All of these ganglia serve as true nerve centres and from them pass off branches of distribution to the involuntary muscles of the blood-vessels and of the gastrointestinal canal, to the thoracic and abdominal viscera, to the secreting cells of the various glands. etc.
Functionally the sympathetic system is quite distinct from the cerebrospinal system. It has been called the system of vegetative existence be cause of its presiding over the processes of nutri tion and growth, flue so-called vegetative func tions• in contra-distinction to the cerebrospinal system, which presides over such distinctly ani mal faculties as sensation, motion, and intellect. The sympathetic system controls the so-called automatic mechanisms of the body, the rhythmi cal beating of the heart, contraction and dilata tion of the arteries, the peristaltic action of the gastrointestinal tract, the contraction of smooth muscle in general wherever found, the control of secretion of various glands, etc. It has also been customary to ascribe to the sympathetic• a certain 'trophic' function by which was meant the determination of the nutrition of the various tissues and organs. It seems more proper to ascribe this nutritional control to its vasomotor function. by means of which it determines the blood supply to the various parts. The sympa thetic nerves contain both afferent and efferent fibres, so that impulses are transmitted both to and from the ganglionic centres. It is doubtful bow many of the afferent impulses are sensory, while certainly many of the efferent impulses are not motor. The close anatomical relation which exists between the cerebro-spinal and the sympa thetic system has been mentioned, and while the latter seems to be to a certain extent independent in its action, it is not infrequently brought under the control of the former even in our conscious activities. Thus in the case of hlushing., an im pulse reaching the cerehro-spinal centres through the eye, ear, or othi•r sense organs causes such a reaction on the part of the sympathetic as to bring about a dilatation of the capillaries of the face. Again, in the ease of the heart. quick heat and palpitation are frequently caused by the reaction of the sympathetic to impulses which bare pa cged in through the cerebrospinal nerves.
BIBLIOGRAPIly. ratersurkunmit Uher Gehtru and Niirkenniark des ilensehen and der Situ Vethirree Gerlach• The Npima1 Cord—.11anual of Ilis10199y. by S. Strieker 4Ent. trail,. New• York, IS721 " Sulla striatum del la SOS.- tanza grigia del cervello." in rkszzetta Ituliumt-Loniburchq, col, vi. ST3 ) (;))Igi, Sutler lbw anytomitt deyli oryuni ecntrali sistemu (Reggio-Emilia, lss2).
For review of the litter structure of the neurone, consult The errous .s•ijssImi owl Its Constituent _\ fAlrOn CS, Lewellys F. Barker) New York, 1599 I. For gross anatomy of nervous system, consult: Uray's .Inotomy, lith edition: inotomy, vol. iii., parts ] and 2; Gardinier, The .Inotomy o/ the rcntral .Vcrrwis ,‘,41/sit'in. For histology of the lielN01.1,-, system. consult: Stohr, Text-book of Histology (Philadelphia, 111t11) ; Piorsol. ornad if islotogy ; Schiitor, .1 Course of Praelicol Ilis toloyy and Es.!“ ?dials of Histology.