CH. XXVII.] 



STRUCTURE OF THE STOMACH. 



445 



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. Con- 

 tinuous 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 mu- 

 cous membrane bounding the 

 minute, polygonal pits before 

 referred to. From this super- 

 ficial network the veins chiefly 

 take their origin. Thence pass- 

 ing 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 sub-mucous tissue (fig. 



376). 



Nerves. The nerves of the 

 stomach are derived from the 

 pneumogastric and sympa- 

 thetic, and form two plexuses, 

 one in the sub-mucous and the 

 other between the muscular 

 layers. 



These plexuses are con- 

 tinuous with those which occur 

 in the same situations in the 

 intestine, and which we shall again refer to there. 



- 3?6. Plan of the blood-vessels of the 

 stomach, as they would be seen in a 

 vertical section, a, arteries, passing up 

 from the vessels of submucous coat: 

 6, capillaries branching between and 

 around the tubes ; c, superficial plexus 

 of capillaries occupying the ridges of 

 the mucous membrane ; d, vein f ormed 

 by the union of veins which, having 

 collected the blood of the superficial 

 capillary plexus, are seen passing down 

 between the tubes. (Brinton.) 



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 Small Intestine, the average 



