THE JEJUNUM AND ILEUM 



1293 



extending from the base to the summit of the villus, and giving off laterally individual muscle 

 cells, which are enclosed by the reticulum, and by it are attached to the basement membrane. 



The bloodvessels form a plexus between the lacteal and the basement membrane, and are 

 enclosed in the reticular tissue; in the interstices of the capillary plexus, which they form, are 

 contained the cells of the villus. 



The intestinal glands, crypts or glands of Lieberkuhn (glandulae intestinales [Liebrkithni]) 

 (Figs. 1020 and 1024), are found in considerable numbers over every part of the mucous membrane 

 of the small intestine. They consist of minute simple tubular depressions of the mucous mem- 

 brane, arranged perpendicularly to the surface, upon which they open by small circular aper- 

 tures. They may be seen with the aid of a lens, their orifices appearing as minute dots seen at 

 the base of the villi. Their walls are thin, consisting of a basement membrane lined by simple 

 columnar epithelium, and are surrounded by capillary vessels. In the glands of the ileum and 

 also to a certain extent those of the jejunum are seen some coarsely granular cells, the cells of 

 Paneth. They seem to be cells of special secretion. 



The duodenal or Brunner's glands (glandulae duodnialcs [Bntnneri]) are limited to the duode- 

 num. They are small, branched, tubular glands in the submucous coat, and open upon the 

 surface of the mucous membrane by minute excretory ducts. They are most numerous and 

 largest near the pylorus. They resemble the pyloric glands in appearance, and are believed to 

 be a direct continuation of those glands. The cells are clear and pale staining, and Stohr states 

 that cells resembling parietal cells are occasionally seen. 



CALCIFORM 

 CELL 



GLANDULAR 

 CELL 



FIG. 1020. Section of a gland of Lieberkiihn in the 

 mouse. (Paneth.) 



FIG. 1021. Transverse section of crypts of 

 Lieberkuhn. (Klein and Noble Smith.) 



The lymph nodules (noduli lymphatici) are small pyriform structures. The bodies of the nodes 

 are in the submucous coat; the apices are in the mucous membrane, which is thrown by them 

 into rounded elevations. They are divided into solitary follicles and Peyer's patches. 



The solitary follicles (noduli lymphatici solitarii) (Fig. 1017) are found scattered throughout 

 the mucous and submucous coats of the small intestine and the large intestine. In the small 

 intestine they are most numerous in the lower part of the ileum, upon and between the valvulae 

 conniventes. Thev are small, round, whitish bodies, from one-twenty-fourth of an inch to one- 

 quarter of an inch (1 to 6 mm.) in diameter. Their free surface is covered with villi, and each 

 follicle is surrounded by the openings of the glands of Lieberkuhn. They are now recognized 

 as lymph nodules. They consist 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 at the base of the nodule, through which 

 they communicate with the lacteal system. Each consists of a lighter central area, the germinal 

 centre, where the leukocytes are reproducing, and a peripheral darker zone, where the cells are 

 more numerous and closely packed. 



Peyer's patches, the agminated follicles, or the tonsillae intestinsles (noduli lymphatici 

 ar/r/rrr/ati [Peyeri]) (Figs. 1022, 1023, and 1024) may be regarded as aggregations of solitary follicles, 

 forming circular or oval patches from te,n to sixty in number, and varying in length from half an 

 inch to four inches (1.25 to 10 cm.). Thev are largest and most numerous in the ileum. In 

 the lower part of the jejunum they are small, of a circular form, 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 the above-described solitary follicles covered with mucous membrane, and 

 in almost every respect are similar in structure to them. They do not, however, as a rule, 



