686 



PHYSIOLOGY OF SPECIAL NERVES 



the sympathetic or autonomic (Langley) nervous system presides over all 

 of the functions not tinder the direct control of the will. 



All these nerves agree in having their origin in the central nervous sys- 

 tem. In the strict sense the sympathetic nerves constitute processes of the 



lateral horn cells on the 

 same side of the cord. 



The efferent fibers 

 belonging to the auto- 

 nomic nerves are slen- 

 der in comparison with 

 other efferent nerve 

 fibers, and, unlike the 

 motor nerves to the 

 skeletal muscles, connect 

 somewhere along their 

 course with ganglion 

 cells from which new 

 fibers issue to complete 

 the pathway. 



The afferent fibers 

 found in the sympa- 

 thetic nerves are for the 

 most part offshoots from 

 the ganglion cells in the 

 spinal ganglia ; there are 

 among them some which 

 spring from peripheral 

 ganglion cells, and thus 

 constitute true sympa- 

 thetic fibers. 



The most important 

 visceral fibers of the 

 cranial nerves have al- 

 ready been studied. We 

 have then to consider 

 only the visceral fibers 

 coming from the spinal 

 cord. 



The preganglionic 



FIG. 301. Schematic representation of the connections of 

 the sympathetic fibers, after Kolliker. PG, peripheral 

 ganglion; Gs, chain ganglion; Pk, Pacinian corpuscle; 

 Rca, white ramus cornmunicans ; Rcgr, gray ramus com- 

 municans; St, sympathetic trunk. The preganglionic fibers 

 are black, the postganglionic red, the afferent fibers blue. 



filters, to use Langley 's 

 term, make their exit 



exclusively in the white rami communicantes of the spinal cord (Gas- 

 kell), and all of them end with their terminal arborizations about ganglion 

 cells situated at a greater or less distance from the cord. There are no 

 connections between the separate ganglion cells either within the same or 

 different ganglia. 



The length of these fibers varies greatly (cf. Fig. 301, m^ m 7 ). Some 



