THE DIGESTIVE TRACT. j^e 



The blood-vessels supplying the intestines follow the general 

 arrangement of those of the stomach. The larger vessels pierce the 

 serous and muscular coats, giving off slender twigs to supply the 

 tissues of these tunics ; upon reaching the submucosa the vessels 

 form a wide-meshed net-work. Numerous branches then pass 

 through the muscularis mucosae to be distributed to the deeper as 

 well as to the more superficial parts of the mucosa; narrow capil- 

 laries form net-works which surround the tubular glands, while be- 

 neath the epithelium wider capillaries encircle the mouths of the 

 follicles. From this superficial capillary net-work the veins arise and, 

 passing between the follicles, join the deeper venous plexus, which 

 in turn empties into the larger veins of the submucosa. 



In those parts of the intestine where villi exist, special additional 

 arteries pass directly to the bases of the villi, where they expand into 

 capillary net-works which run beneath the epithelium and around 

 the central lacteal as far as the ends of the villi. These capillaries 

 terminate in venous stems which descend almost perpendicularly 

 into the mucosa, in their course receiving the superficial capillaries 

 encircling the glandular ducts. Brunner's glands and the solitary 

 and agminated follicles are supplied from the submucosa by vessels 

 which terminate in capillary net-works distributed to the acini of the 

 glands and to the interior of the lymph-follicles. 



The lymphatics of the intestinal tract are very abundant. They 

 begin as blind canals, whose slightly-dilated ends lie within the mu- 

 cosa between the tubular follicles ; in those parts of the intestine 

 where villi exist, the centre of these projections is occupied by a 

 lymphatic radicle, the chyle-vessel, or lacteal. All these vessels de- 

 scend to join a rich plexus of lymphatic trunks situated within the 

 deeper layers of the mucosa. Within the submucosa an addi- 

 tional net-work of still larger channels exists, the two sets of vessels 

 freely communicating through numerous anastomoses. The accumu- 

 lations within these net-works are carried off by lymphatic trunks 

 which pierce the muscle and pass off between the two layers of the 

 peritoneum into the adjacent mesenteric glands, in their course 

 taking up the vessels carrying the lymph collected from the mus- 

 cular tissue. Many vessels of the submucous net-work, as well as 

 the larger lymphatic trunks, are provided with valves, whose position 

 is usually indicated by dilatations in the contour of the vessel. 



The nerves distributed to the intestines are arranged almost iden- 

 tically as those of the stomach ; they are composed largely of non- 

 medullated fibres, derived from the trunks which pass within the 

 mesentery from the large abdominal sympathetic plexuses. After 

 giving off branches to the serous coat, the nerves pierce the longitu- 

 dinal muscular tunic to form the rich intramuscular plexus of Auer- 



