SYMPATHETIC SYSTEM. 



755 



that two spinal nerves are supplied from one ganglion ; or two ganglia may supply 

 branches to a single spinal nerve. The gray ramus is distributed along the somatic 

 divisions of the spinal nerves, supplying branches to unstriped muscular fibres 

 (vase-motor, pilo-motor) and glands (secretory). They also provide small recurrent 

 branches, ending in the membranes enveloping the spinal nerve-roots. Mingled 

 with the non-medullated fibres of the gray rami are a small number of medullated 

 fibres, regarded as 

 afferent fibres 

 axons passing to the 

 spinal ganglia which 

 are incorporated with 

 the gray rami. 



The connect- 

 ing cords of the 

 sympathetic system 

 are composed of white 

 and gray fibres. The 

 white fibres are : (1) 

 splanchnic efferent 

 fibres, passing to a 

 ganglion above or 

 below the point of 

 entrance into the 

 sympathetic system ; 

 (2) splanchnic affer- 

 ent fibres, guided \\/ SPLANCHNIC 



along the connect- 

 ing cord and over or 

 through the ganglia. 

 The gray fibres are 

 the axons of sympa- 

 thetic ganglion cells: 

 (1) true association 

 fibres passing into 

 connexion with the 

 cells of a neighbour- 

 ing ganglion; (2) 

 fibres passing along 

 the connecting cord 

 for a certain distance 

 upwards or down- 

 wards before entering 

 the splanchnic area as 

 peripheral branches. 



The peripheral 

 branches of the 

 sympathetic trunk 

 consist of (1) white 

 fibres, which may be 



either splanchnic afferent fibres on their way from the viscera through the 

 gangliated trunk to the spinal ganglia, or splanchnic efferent fibres which, after 

 traversing the gangliated trunk, proceed to join and end in collateral or terminal 

 ganglia in relation to viscera; (2) gray fibres, efferent branches, the axons of 

 the ganglion cells, distributed on the one hand peripherally to the vessels and 

 viscera of the splanchnic area, and on the other hand centrally through the gray 

 rami communicantes and the somatic divisions of the spinal nerves, to the glands 

 and involuntary muscles in the somatic area, as secretory, and vaso-motor and 

 pilo-motor fibres. 



Although forming always one continuous cord, the sympathetic system may 



49 a 



FIG. 636. SCHEME OF THE CONSTITUTION AND CONNEXIONS OF THE 

 GANGLIATED TRUNK OF THE SYMPATHETIC. 



The gangliated trunk is indicated on the right, with the arrangement of the fibres 

 arising from the ganglion cells. On the left the roots and trunks of 

 spinal nerves are shown, with the arrangement of the white ramus com- 

 municans above and of the gray ramus below. 



