1168 



SPLANCHNOLOGY 



vagi, the former being distributed upon the back, and the latter upon the front part of the organ. 

 A great number of branches from the celiac plexus of the sympathetic are also distributed to 

 it. Nerve plexuses are found in the submucous coat and between the layers of the muscular coat 

 as in the intestine. From these plexuses fibrils are distributed to the muscular tissue and the 

 mucous membrane. 





The Small Intestine (Intestinum Tenue). 



The small intestine is a convoluted tube, extending from the pylorus to the colic 

 valve, where it ends in the large intestine. It is about 7 metres long, 1 and gradually 

 diminishes in size from its commencement to its termination. It is contained in 

 the central and lower part of the abdominal cavity, and is surrounded above and 

 at the sides by the large intestine; a portion of it extends below the superior 

 aperture of the pelvis and lies in front of the rectum. It is in relation, in front, with 

 the greater omentum and abdominal parietes, and is connected to the vertebral 

 column by a fold of peritoneum, the mesentery. The small intestine is divisible 

 into three portions: the duodenum, the jejunum, and the ileum. 





FIG. 105C. The duodenum and pancreas. 



The Duodenum (Fig. 1056) has received its name from being about equal in 

 length to the breadth of twelve fingers (25 cm.). It is the shortest, the widest, 

 and the most fixed part of the small intestine, and has no mesentery, being only 

 partially covered by peritoneum. Its course presents a remarkable curve, some- 

 what of the shape of an imperfect circle, so that its termination is not far removed 

 from its starting-point. 



In the adult the course of the duodenum is as follows : commencing at the pylorus 

 it passes backward, upward, and to the right, beneath the quadrate lobe of the 

 liver to the neck of the gall-bladder, varying slightly in direction according to the 

 degree of distension of the stomach: it then takes a sharp curve and descends 

 along the right margin of the head of the pancreas, for a variable distance, generally 

 to the level of the upper border of the body of the fourth lumbar vertebra. It 



