1176 



SPLANCHNOLOGY 





of a lens, their orifices appearing as minute dots scattered between the villi. Their walls are 

 thin, consisting of a basement membrane lined by columnar epithelium, and covered on their 

 exterior by capillary vessels. 



The duodenal glands (glandules duodenales [Brunneri]; Brunner's glands) are limited to the 

 duodenum (Fig. 1058), and are found in the submucous areolar tissue. They are largest and most 

 numerous near the pylorus, forming an almost complete layer in the superior portion and 

 upper half of the descending portions of the duodenum. They then begin to diminish in 

 number, and practically disappear at the junction of the duodenum and jejunum. They are 

 small compound acinotubular glands consisting of a number of alveoli lined by short columnar 

 epithelium and opening by a single duct on the inner surface of the intestine. 



The solitary lymphatic nodules (noduli lymphatid solitarii; solitary glands) are found scattered 

 throughout the mucous membrane of the small intestine, but are most numerous in the lower 

 part of the ileum. Their free surfaces are covered with rudimentary villi, except at the sum- 

 mits, and each gland is surrounded by the openings of the intestinal glands. Each consists of a 

 dense interlacing retiform tissue closely packed with lymph-corpuscles, and permeated with an 

 abundant capillary network. The interspaces of the retiform tissue are continuous with larger 

 lymph spaces which surround the gland, through which they communicate with the lacteal 

 system. They are situated partly in the submucous tissue, partly in the mucous membrane, 

 where they form slight projections of its epithelial layer (see Fig. 1082). 



The aggregated lymphatic nodules (noduli lymphatid aggregati; Peyer's patches; Peyer's glands; 

 agminated follicles; tonsilloe intestinales) (Fig. 1063) form circular or oval patches, from twenty 

 to thirty in number, and varying in length from 2 to 10 cm. They are largest and most numerous 

 in the ileum. In the lower part of the jejunum they are small, circular, and few in number. 

 They are occasionally seen in the duodenum. They are placed lengthwise in the intestine, and 

 are situated in the portion of the tube most distant from the attachment of the mesentery. Each 

 patch is formed of a group of solitary lymphatic nodules covered with mucous membrane, but 

 the patches do not, as a rule, possess villi on their free surfaces. They are best marked in the 

 young subject, become indistinct in middle age, and sometimes disappear altogether in 

 advanced life. They are freely supplied with bloodvessels (Fig. 1064), which form an abundant 

 plexus around each follicle and give off fine branches permeating the lymphoid tissue in the 

 interior of the follicle. The lymphatic plexuses are especially abundant around these patches. 



Vessels and Nerves. The jejunum and ileum are supplied by the superior mesenteric artery, 

 the intestinal branches of which, having reached the attached border of the bowel, run between 



the serous and muscular coats, with frequent in- 

 osculations to the free border, where they also 

 anastomose with other branches running around 

 the opposite surface of the gut. From these 

 vessels numerous branches are given off, which 

 pierce the muscular coat, supplying it and forming 

 an intricate plexus in the submucous tissue. 

 From this plexus minute vessels pass to the glands 

 and villi of the mucous membrane. The veins 

 have a similar course and arrangement to the 



FIG. 1071. The myenteric plexus from the rabbit. 

 X 50. 



FIG. 1072. The plexus of the submucosa from the 

 rabbit X50. 



arteries. The lymphatics of the small intestine (lacteals) are arranged in two sets, those of the 

 mucous membrane and those of the muscular coat. The lymphatics of the villi commence in 

 these structures in the manner described above. They form an intricate plexus in the mucous 

 and submucous tissue, being joined by the lymphatics from the lymph spaces at the bases of 

 the solitary nodules, and from this pass to larger vessels at the mesenteric border of the gut. The 

 lymphatics of the muscular coat are situated to a great extent between the two layers of muscular 

 fibers, where they form a close plexus; throughout their course they communicate freely with 



