THE ALIMENTARY CANAL AND ITS APPENDAGES. 343 



plexus of Auerbach which lies between the two muscular 

 coats, and the plexus of Meissner found in the submucous 

 coat. The extrinsic fibres proceed immediately from the 

 gangliated solar plexus already referred to and from a similar 

 mesenter ic plexus which lies lower in the abdomen; except a 

 few branches to the longitudinal muscular coat of the rectum 

 which pass directly from some of the sacral spinal nerves. 

 Some of the fibres distributed from the solar plexus are 

 those running from the brain in the right pneumogastric, 

 and probably also from the left, having crossed over to the 

 left in branches joining the two. Others reach the solar 

 plexus by means of the splanchnics and other nerves pro- 

 ceed ing from the thoracic parts of the two sympathetic chains. 

 These are partly vaso-constrictor fibres (Chap. XVIII.), but 

 in part go to the muscular coats of the intestine. They may 

 be traced back through the communicating branches from 

 sympathetic ganglia to the corresponding spinal nerves and 

 thence by the ventral nerve-roots into the spinal cord. 

 The fibres passing to the intestines from the mesenteric 

 plexus reach that plexus from the posterior thoracic and 

 anterior lumbar sympathetic ganglia, and can also be tracked 

 by experiment to the spinal cord. 



The Liver. Besides the secretions formed by the glands 

 imbedded in its walls, the small intestine receives those of 

 two large glands, the liver and the pancreas, which lie in the 

 abdominal cavity. The ducts of both open by a common 

 aperture into the duodenum about 10 centimeters (4 inches) 

 from the pylorus. 



The liver is the largest gland in the Body, weighing from 

 1400 to 1700 grams (50 to 64 ounces). It is situated in the 

 upper part of the abdominal cavity (le, U' 9 Fig. 1), rather 

 more on the right than on the left side and immediately 

 below the diaphragm, into the concavity of which its upper 

 surface fits, and reaches across the middle line above the 

 pyloru; end of the stomach. It is of dark reddish-brown 

 color, and of a soft friable texture. A deep fissure incom- 

 pletely divides the organ into right and left lobes, of which 

 the risrht is much the larger; on its under surface (Fig. 116) 

 shallower grooves mark off several minor lobes. Its upper 

 surface is smooth and convex. The vessels carrying blood 

 to the liver are the portal vein, Vp, and the hepatic artery; 

 both enter it at a fissure (the portal fissure) on its under side, 



