1010 THE DIGESTIVE SYSTEM. 
branches, which enter the mucous membrane and form capillary plexuses around the glands as 
far as the surface. 
The veins begin in the « capillary plexuses around the glands ; uniting, they form a network in 
the submucosa, from which arise branches that pierce the muscular coat, and fins wy end in the 
following veins: the right gastro-epiploic, which joins the superior mesenteric; the left gastro- 
eprplore, ‘and four or five veins corresponding to the vasw brevia arteries, which fee the splenic ; 
the coronary or gastric vein, which runs along the lesser curvature tow ards the cardia, receives an 
cesophageal branch, and then turns down and runs beside the coronary artery to join the portal 
trunk ; and the pyloric vein, corresponding to the same named artery, which also joims the portal. 
These veins contain numerous valves, which, though competent to prevent the return of blood in 
the child, are rarely so in the adult. 
The lymphatics arise in the mucous membrane around the gastric glands; they then join a 
plexus of valved vessels in the submucosa, from which the chief trunks pass with the blood- 
vessels to the curvatures, being joined on the way by the efferent vessels of a subperitoneal 
lymphatic plexus. They are connected with the superior gastric glands along the lesser curya- 
tures, the inferior gastric glands along the great curvature, and the splenic g clands, which they reach 
with the vasa brevia. Finally, the efferent vessels of all these join the coeliac glands. 
The nerves are derived ‘from the two pneumogastrics and trom the solar plecus of the 
sympathetic. The pneumogastric nerves pass down through the diaphragm with the cesophagus, 
the left lying on its front, the right on its back ; in this way they reach the upper and lower 
surfaces of the stomach respectively. Here they unite with the sympathetic fibres from the 
ceehae plexus (an offshoot of the solar plexus), which pass to the stomach with the branches of 
the coeliac axis. The nerve fibres, which are chiefly non-medullated, form two ganghated 
plexuses, those of Auerbach and Meissner , in the muscular and submucous coats respectively. 
The development of the stomach is described with that of the intestines on page 1055. 
INTESTINES 
As the coats of the remaining portions of the digestive tube agree in many 
particulars, it will be convenient to describe the general structure of the intestines 
here. Subsequently, any pecularities of structure in particular regions will be 
described with the corresponding division of the tube. 
STRUCTURE OF THE INTESTINES. 
The wall of the intestines, like that of the stomach, is made up of four coats, which 
are named from without inwards—serous or peritoneal, muscular, submucous, and mucous 
(Figs. 683 and 684). 
1. Serous Coat (tunica serosa).—This is formed of peritoneum, and confers on the 
Two mesenteric lymphatic glands 
Artery 
Mesentery 
a Lymphatic 
Circular 
muscular fibres 
Longitudinal muscular fibres 
Fic. 683.—A Portion OF SMALL INTESTINE, WITH MESENTERY AND VESSELS. The peritoneal coat has been 
removed from the right half, and the two layers of the muscular coat exposed. 
intestines their smooth and glossy appearance. It varies in the extent to which it clothes 
the different divisions of the tube, giving the duodenum, the ascending, descending, and 
iliae colons, and the rectum only a partial covering ; whilst it clothes the jejunum and 
ileum, the cecum, the transverse and the pelvic colons completely. The detailed 
