284 THE DIGESTIVE ORGANS. 



in the mucosa and extending into the connective-tissue papillae of 

 the mucosa. 



The vessels of the stomach are arranged in plexuses in the 

 muscular coat, submucosa, and beneath the muscularis mucosae, as 

 previously described. From the plexus beneath the muscularis mu- 

 cosae, small branches are given off which pass through this layer and 

 in the mucosa form a capillary network, consisting of relatively small 

 capillaries, which surround the gastric glands, this plexus being par- 

 ticularly well developed in the region around the body and neck of 

 the glands, where the parietal cells are most numerous. The capil- 

 laries of this network are continuous with capillaries of a much larger 

 size, forming a network surrounding the gastric crypts and situated 

 immediately under the epithelium lining the mucosa of the stomach. 

 The blood is collected from this capillary plexus by small veins 

 which pass nearly perpendicularly through the mucosa, forming a 

 plexus above the muscularis mucosae, from which small veins pass 

 through the muscularis mucosae to the venous plexus in the sub- 

 mucosa. 



The blood-vessels of the mucosa of the small intestine may be 

 divided into (i) the arteries of the villi and (2) the arteries of the 

 intestinal glands. The former arise principally from the deep arterial 

 network in the submucosa, then penetrate the muscularis mucosae 

 and give off branches at acute angles which continue without 

 further branching into the summits of the villi. Within the villi 

 themselves the arteries lie in the axes. The broader villi may 

 contain two arteries. The circular muscle-fibers of the arteries 

 gradually disappear inside of the villi (dog), and at the summit of 

 the latter the vessels break up into a large number of capillaries. 

 These form a dense network extending beneath the basement mem- 

 brane and into its marginal layer. These networks give rise to 

 venous capillaries which unite to form small vessels and finally end 

 in two or more larger veins inside of the villi. These latter are con- 

 nected with the venous network in the mucosa. 



The glandular arteries, derived principally from the superficial 

 network of the submucosa, also pass through the muscularis 

 mucosae and break up internally into capillary nets which encircle 

 the intestinal glands ; these give rise to small veins which empty 

 into the venous plexus of the mucosa. The veins of the plexus in 

 the mucosa unite to form larger branches, which connect with the 

 plexus in the submucosa (compare Fig. 224). In the dog these 

 trunks inside of the muscularis mucosae are encircled by bundles of 

 muscle-fibers (sphincters, F. P. Mall). The capillaries of the solitary 

 lymph-nodules do not always penetrate into the centers of the latter, 

 but often leave a central nonvascular area. 



The blood-vessels of the mucosa of the large intestine are, in 

 their distribution, similar to the glandular vessels of the small intes- 

 tine and stomach. 



The lymph-vessels begin in the mucosa near the epithelium, pass 



