CH. XX VI I.] THE INTESTINES 451 



situated. They are directly continuous with Brunner's glands in the 

 duodenum. 



Lympliatics. Lymphatic vessels surround the gland tubes to a 

 greater or less extent. Towards the fundus of the cardiac glands are 

 found masses of lymphoid tissue, which may appear as distinct 

 follicles, somewhat like the solitary glands of the small intestine. 



Blood-vessels. The blood-vessels of the stomach, which first break 

 up in the sub-mucous tissue, send branches upward between the 

 closely packed glandular tubes, anastomosing around them by means 

 of a fine capillary network, with oblong meshes. Continuous with 

 this deeper plexus, or prolonged upwards from it, is a more superficial 

 network of larger capillaries, which branch densely around the orifices 

 of the tubes, and form the framework on which are moulded the 

 small elevated ridges of mucous membrane bounding the minute, 

 polygonal pits before referred to. From this superficial network the 

 veins chiefly take their origin. Thence passing down between the 

 tubes, with no very free connection with the deeper inter-tubular 

 capillary plexus, they open finally into the venous network in the 

 submucous tissue (fig. 378). 



Nerves. The nerves of the stomach are derived from the pneumo- 

 gastric and sympathetic, and form two plexuses, one in the sub- 

 mucous and the other between the muscular layers. 



These plexuses are continuous with those which occur in the 

 same situations in the intestine, and which we shall again refer to 

 there. 



THE INTESTINES. 



The Intestinal Canal is divided into two chief portions, named, 

 from their differences in diameter, the small and large intestine. 

 These are continuous with each other, and communicate by means 

 of an opening guarded by a valve, the ileo-ccecal valve, which allows 

 the passage of the products of digestion from the small into the 

 large bowel, but not, under ordinary circumstances, in the opposite 

 direction. 



The Small Intestine, the average length of which in an adult 

 is about twenty feet, has been divided, for convenience of descrip- 

 tion, into three portions, viz., the duodenum, which extends for eight 

 or ten inches beyond the pylorus ; the jejunum, which forms two-fifths, 

 and the ileum, which forms three-fifths of the rest of the canal. 



Like the stomach, it is constructed of four coats, viz., the serous, 

 muscular, submucous, and mucous. 



(1.) The serous coat is formed by the visceral layer of the 

 peritoneum, and has the structure of serous membranes in general. 



(2.) The muscular coat consists of an internal circular and an 

 external longitudinal layer: the former is usually considerably the 



