1 88 THE NERVOUS SYSTEM 



The greater and smaller splanchnics descend through the 

 thorax and pierce the crus of the diaphragm. On the 

 abdominal surface of the latter, they join the large casliac 

 (sem'ilunar) gang/ion, which is a subsidiary sympathetic ganglion. 

 The two cceliac ganglia are connected to one another by 

 numerous branches, which are closely associated with the 

 cceliac artery and its branches. From the ganglia visceral 

 branches arise and travel on the coats of the arteries to be 

 distributed to the abdominal viscera. The precise innervation 

 of the viscera is dealt with under the individual organs. 



In the abdomen, the sympathetic trunk lies on the sides of 

 the bodies of the lumbar vertebrae. There are usually five 

 lumbar ganglia, and, while each possesses a grey ram us 

 communicans, only the first and, sometimes, the second 

 possess white rami communicantes. Most of the efferent 

 fibres of the latter are carried off by the femoral and obturator 

 nerves to supply the blood-vessels, etc., of the lower limb, 

 while others have a similar distribution in the walls of the 

 abdomen. 



In the pelvis, the sympathetic trunks lie in front of the 

 sacrum, medial to the anterior sacral foramina, and in front of 

 the coccyx they unite with one another in the ganglion impar. 

 There are usually five sacral ganglia and, though each possesses 

 a grey ramus communicans, the white rami are restricted to 

 the second and third, or, in some cases, to the third and 

 fourth ganglia. 



A large plexus is developed in connection with the sym- 

 pathetic in front of the promontory of the sacrum. It is 

 termed the hypogastric plexus and it is formed by (i) fibres 

 from the aortic plexus, which is a downward continuation of 

 the plexus connecting the cceliac ganglia; (2) branches from 

 the lumbar ganglia ; (3) branches from the sacral ganglia. By 

 means of this plexus the white rami communicantes of the mid- 

 sacral region are distributed to the pelvic viscera, the rectum, 

 anal canal, bladder, prostate, etc. 



LESIONS OF THE SYMPATHETIC SYSTEM fall into two groups. 



