32 ORGANS OF DIGESTION. 



The Small Intestine, though an uninterrupted tube from one 

 end to the other, is divided by anatomists into Duodenum, Jeju- 

 num, and Ileum. There is some reason for the first name, but 

 the two latter may be very conveniently blended, as has been 

 done by some, under the term Mesenteric Portion of the intesti- 

 nal canal. 



The Duodenum, named from its being about twelve inches, or 

 twelve fingers' breadth in length, is nearest to the stomach; or, 

 in other words, is the commencement of the canal. It is sensi- 

 bly larger than either of the others, and is, moreover, suscepti- 

 ble of great dilatation, whence it has also been called Ventriculus 

 Succenturiatus. Its direction is much varied: beginning at the 

 pylorus, it first of all passes upwards and to the right side till it 

 reaches the neck of the gall-bladder; it then turns downwards, 

 so as to form a right angle with itself, and descends in front of 

 the right kidney to the third lumbar vertebra, being there placed 

 behind the superior lamina of the transverse mesocolon. It 

 then forms a round elbow, crosses the spine obliquely, under 

 the junction of the mesentery and mesocolon, in ascending 

 from right to left; and making its appearance to the left of the 

 second lumbar vertebra, is there continued into the mesenteric 

 portion of intestine. 



The beginning of the duodenum is moveable, and has a pe- 

 ritoneal coat continued from the lesser omentum; the descend- 

 ing and the transverse portions have no proper peritoneal coat, 

 but are only loosely fixed between the laminae of the mesocolon; 

 the termination is both moveable and has a peritoneal covering. 

 from being at the commencement of the mesentery. 



From the course assigned to the duodenum, it is evident that 

 it forms the segment of a circle, the concavity of which looks to 

 the left side. This concavity is occupied by the head of the 

 pancreas. The transverse portion crosses the spine below 7 the 

 latter, and is separated from it by the superior mesenteric artery 

 and by the vena portarum: behind it are the crura of the dia- 

 phragm, the ascending cava, and the aorta. 



The organization of the duodenum is the same with that of 

 other portions of the intestinum tenue. Its peculiarities consist 

 only in a partial deficiency of peritoneal coat, and in its aug- 

 mented size. Its internal or mucous coat is very much tinged 



