252 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



vagus. Physiologically these fibers 



Fig. 112. — Diagram giving a schematic 

 representation of the course of the autonomic 

 (sympathetic) fibers arising from the thoraci co- 

 lumbar and sacral regions of the cord. The 

 preganglionic fiber is represented in red, the 

 postganglionic in black lines. The arrows in- 

 dicate the normal direction of the nerve im- 

 pulses or nerve conduction. _ S.c, Superior 

 cervical ganglion; I.e., inferior cervical gan- 

 glion; T, the first thoracic ganglion; Sp., the 

 splanchnic nerve; C, the semilunar or celiac 

 ganglion; m., the inferior mesenteric ganglion; 

 h., the hypogastric nerves; N.E., the nervus 

 erigens. The numerals indicate the corre- 

 sponding spinal nerves. 



consist of motor fibers (viscero- 

 motor fibers) to the mus- 

 culature of the esophagus, 

 stomach, and small intestine, 

 motor fibers to the bron- 

 chial musculature, inhibitory 

 fibers to the heart, and secre- 

 tory fibers to the gastric and 

 pancreatic glands. The gan- 

 glia in which the pregangli- 

 onic portions end have not 

 been definitely located, but 

 probably they comprise the 

 small and, for the most part, 

 unnamed local ganglia found 

 in or near the organs inner- 

 vated. 



General Course of the Au- 

 tonomic Fibers Arising from 

 the Sacral Cord — Sacral Auto- 

 nomics. — The autonomic fibers 

 of this region emerge from the 

 cord in the anterior roots of 

 the sacral nerves, — second to 

 fourth. The branches from 

 these roots unite to form the 

 so-called nervus erigens (pelvic 

 nerve), which loses itself in the 

 pelvic plexus without making 

 connections with the sympa- 

 thetic chain of ganglia. The 

 pelvic plexus is formed in part 

 also from the hypogastric 

 nerve arising from the inferior 

 mesenteric ganglion. Through 

 this latter path thoracic auto- 

 nomic fibers from the upper 

 lumbar region enter the plexus 

 (Fig. 112). The autonomic 

 fibers of the nervus erigens 

 supply vasodilator fibers to the 

 external genital organs, and in 

 the male constitute the nervous 

 part of the physiological mech- 

 anism for erection, whence the 



