DUODENUM AND PANCKEAS DISSECTED. 341 



ring, which assists in closing the opening. If this membrane and 

 the submucous layer are removed from the pyloric part of the 

 stomach, the ring of muscular fibres (sphincter of the pylorus) will 

 be more perfectly seen. 



With the aid of a lens, the surface of the mucous membrane, when On the sur- 

 well washed, may be seen to be covered by shallow depressions or or alveoli; 

 alveoli (fig. 127), which measure from ^th to Ttrrrth of an inch their size, 

 across. Generally hexagonal or polygonal in outline, the hollows shape, 

 become larger and more elongated towards the small end of the and appear- 

 stomach ; and near the pylorus the margins of the alveoli project, 

 and become irregular. In the bottom of each depression are the 

 apertures of minute tubular glands. 



Blood-vessels. The arteries of the stomach are derived from the Arteries; 

 branches of the coeliac axis, and have been seen to form an arch along 

 each curvature (pp. 332 et seq.}. From these arches branches pass to 

 both surfaces of the stomach, and after supplying the muscular coats 

 divide in the submucous layer into minute vessels which enter the 

 substance of the mucous membrane. The veins have a corresponding veins ; 

 arrangement, and pass to the portal system (p. 334). 



Lymphatics. The lymphatic vessels proceeding from the stomach lymphatics; 

 run with the blood-vessels, and have a few small glands connected 

 with them along the two curvatures. 



Xu-i-es. The nerves are derived from the pneumo-gastric and and nerves, 

 sympathetic, and can be followed to the fibrous coat : small ganglia 

 have been observed on them. 



THE DUODENUM AND PANCREAS DISSECTED. 



Dissection, The duodenum will now be washed and its mucous 

 surface examined. The commencement of the valvulae couniventes 

 one or two inches from the pylorus will be noticed, and the opening 

 of the biliary and pancreatic ducts examined. 



The aperture of the common bile and pancreatic ducts (fig. 128, e) Opening of 

 is a narrow orifice, from three to four inches below the pylorus, and ' 

 situate in a small prominence of the mucous membrane, at the where 

 inner and posterior part of the duodenum. A probe passed into the Sl1 

 bile-duct will show its oblique course (half an inch or more) under 

 the mucous coat. Occasionally the pancreatic duct opens by a 

 distinct orifice. 



Structure of the common bile-duct. The bile-duct consists of an Two coats 

 external, strong fibrous layer, and of an internal mucous coat. On J^JJf bl 

 the surface of the inner membrane are the openings of numerous 

 branched mucous glands, which are embedded in the fibrous coat ; glands, 

 some of them are aggregated together, and are visible with a lens. 



The coats of the duodenum are like those of the rest of the small 

 intestine (pp. 321 et seq.\ but Brunner's glands should be noticed. 



The Glands of Brunner are small compound bodies, similar to the Glands of 

 buccal and labial glands of the mouth, which exist in the duodenum. Brun 

 Thev are most numerous for a distance of one or two inches near 



