THE ALIMENTARY CANAL 



373 



epithelium and can only with 

 difficulty be distinguished from 

 the adjacent intestinal glands. 

 In the deeper part of the mu- 

 cous membrane the ducts 

 branch and pursue a somewhat 

 tortuous course to the fundus 

 of the gland, where the ter- 

 minal acini of each subdivision 

 of a duct are invested with a 

 distinct fibrous capsule. 



The secreting epithelium 

 of the duodenal glands consists 

 of tall columnar cells which 

 surround a wide lumen. When 

 loaded with secretion the cells 

 are swollen and clear, but be- 

 come shrunken and granular 

 after a period of activity. 

 Their cytoplasm reacts to the 

 specific stains for mucin only 

 when these are applied for a 

 considerable time in concen- 

 trated solution (Bensley). The 

 spheroidal nucleus is situated 

 at the proximal or basal end, 

 and as the cell fills with secre- 

 tion the nucleus becomes pro- 

 gressively flattened. 



Blood Supply. The blood 

 supply of the small intestine 

 resembles that of the stomach. 

 The branches of the mesenteric 

 arteries pass around the intes- 

 tinal wall in the subserous con- 

 nective tissue. From this point 

 they penetrate the muscular 

 coat to form intramuscular and 

 submucous plexuses. From 

 the latter a few branches sup- 



.6 





FIG. 347. THE BLOOD-VESSELS OF THE 

 SMALL INTESTINE OF A DOG, DRAWN AFTER 

 AN INJECTED PREPARATION. 



The arteries are striped, the veins black, 

 the capillaries open. A, villi; B, glands; C, 

 muscularis mucosa?; D, submucosa; E, cir- 

 cular, and F, longitudinal layer of the mus- 

 cular coat; a, venule beginning from the cap- 

 illaries of the villus, and at b, from those 

 among the glands; c, artery to the villus; d, 

 venules in the deeper part of the mucosa; e, 

 main arterial trunk to several adjacent villi; 

 /, arterial branch to the glandular region. 

 Highly magnified. (After Mall, from Oppel.) 



