128 THE A LIMENTA R Y S YSTEM. 



representative of the tunica propria, is a loose and delicate 

 connective tissue extending between the glands and providing 

 basement-membranes and sustentacular tissue for their sup- 

 port. It contains a rich capillary plexus enveloping the 

 glands. Lymphoid cells are scattered about and diffuse 

 lymphoid tissue occurs in places in the subepithelial tissue ; 

 lymphpid nodules occur especially in the pyloric region, where 

 they are called lenticular glands. 



The mmcularis mucosce consists of two thin layers of in- 

 voluntary muscle-cells, the outer longitudinal, the inner cir- 

 cular ; it separates the mucosa from the submucosa, also send- 

 ing muscular branches up among the gland-tubes. When 

 the stomach is contracted the mucosa is thrown into folds 

 or rugaB, permitted by the loose nature of the submucosa. 



The submucosa is a loose areolar tissue lying beneath the 

 mucosa. It contains the larger blood and lymphatic vessels. 

 The muscular coat of the stomach, lying beneath the sub- 

 mucosa, is a thick layer of involuntary muscle, divided in 

 general into two parts, an inner arranged circularly and an 

 outer longitudinal. At the pyloric orifices the circular muscle 

 is thickened to form a sphincter. 



Outside the muscular layer, and covering the outer surface 

 of the stomach, is the serous or peritoneal coat, a portion of 

 the peritoneum reflected over the surface of the organ. It 

 consists of a thin fibrous membrane covered with endo- 

 thelium. 



The stomach is richly supplied with blood and lymphatic 

 vessels, the larger trunks lying in the submucous tissue and 

 giving off capillaries to form a rich network in the mucosa. 



The gastric juice consists of a homogeneous serous secretion, 

 containing leukocytes and epithelium-cells partly digested, 

 " snail-shell-like " granules probably formed by the action of 

 the juice on mucin, and extraneous food-particles and 

 bacteria. 



The Small Intestine. 



The walls of the small intestine are composed of four layers, 

 mucous, submucous, muscular, and peritoneal, from within 

 outward. They are studded with papillary structures called 



/ 



