444 THE TISSUES. 



2. The Ganglionic Nerves. 



These are usually included under the designation of the "sym- 

 pathetic nerve," or " nerves of organic life.'' They are to be re- 

 garded rather as an appendage to the spinal nerves, and are hence 

 next to be described. 



The sympathetic nerve consists of a whitish trunk with a series 

 of ganglia (Fig. 282, s) upon it ; into which branches pass from the 

 spinal nerves (the rami communicantes.) In the chest and abdo- 

 men, these ganglia and the main nerve are situated on each side of 

 the spinal column. 



We have to consider: 



A. The connecting branches. 



B. The ganglia, and their fibres. 



A. The rami communicantes rise from the trunks of the spinal 

 nerves immediately after they are formed by the junction of the 

 anterior and posterior roots. They contain both the coarse and the 

 fine nerve-fibres, but always a preponderance of the latter; of which 

 a portion may be derived from the spinal ganglia. They may thus 

 be regarded as the roots of the sympathetic. Possibly they are 

 derived in some small degree from the sympathetic itself also; the 

 fibres from the latter source, however, entering the main trunk with 

 the rest. 



Having entered the trunk of the sympathetic, the communicating 

 branches run both upwards and downwards in it, towards its ce- 

 phalic and pelvic extremities. Finally, they doubtless go off to be 

 distributed in its peripheral branches; since all the latter frequently 

 contain the same dark -bordered thicker fibres. 



B. The ganglia of the sympathetic have essentially the same 

 structure as the spinal ganglia. They consist (1) of perforating 

 nerve-fibres, proceeding from one part of the trunk to the other, 

 besides those of the rami communicantes; (2,) of numerous gan- 

 glion-cells, and (3} of ganglion- fibres originating from the last. 

 (Fig. 288.) 



1. The perforating fibres require no special description. 



2. The ganglion-cells precisely resemble those in the spinal gan- 

 glia (Fig. 284), except that they are, on an average, smaller; being 

 STHJZJ to TS^JS f an i nc h in diameter, with less and paler pigment, 

 or even none at all ; and usually pretty uniformly rounded. Cells, 



