THE ILEUM. PKACTICAL DEMONSTRATION. 93 



free extremities of many of the villi in the drawing are seen broken, 

 and the epithelium is wanting in places. It is almost impossible to 

 secure perfect villi from human intestine, on account of the length of 

 time usually intervening between death and the removal of the 

 tissue.) (c) Oblique sections. 



2. The crypts of Lieberkuhn. 



3. The lymphatic nodules (so-called solitary glands), constituting 

 the elements of a patch of Peyer. (a) Their projection upon the 

 mucous surface of the gut between the villi. (b) The cover- 

 ing with epithelium on their free borders. (They are located, 

 properly speaking, in the submucosa and between the villi. In the 

 drawing, their bases do not all appear in the submucosa, inasmuch as 

 the nodules are cut in different planes.) 



4. Muscularis mucosse. (a) The elongate nuclei of the invol- 

 untary muscular element. 



5. The submucosa. (a) The blood-vessels, (b) Lymph 

 spaces. (Lymphatic channels are very irregular in form and size, 

 and are often mistaken, in sections, for ruptures in the connective 

 tissue. The stained nuclei of the endothelial cells, with which all 

 lymph channels are lined, will enable you to differentiate.) (c) 

 Glands of Brunner. (There are none shown in this section. The 

 glands consist of convoluted, branching tubes which penetrate from 

 the crypts to the submucosa. They are lined with columnar epithe- 

 lium, and as they are divided in a section, they resemble very nearly 

 a crypt of Lieberkuhn. Extensive groups are found in the duodenum 

 at its pyloric origin.) 



(H.) 



6. The villi. (a) The covering columnar cells, (b) Beaker 

 cells scattered between the last. (These beaker, goblet, or mucous 

 cells are well shown in the intestine of the dog or rabbit.) (c) The 

 lacteals. (These are not plainly demonstrable, under ordinary cir- 

 cumstances, in human tissue. Sections from the gut of a dog killed 

 during the active digestion of materials rich in hydrocarbons, will 

 show them filled with minute fat globules. ) '(d) The basis tissue, 

 a fibrous reticulum containing many lymphoid cells, (e) Portions 

 of the capillary plexuses. 



7. Blood-vessels of the mucosa below the villi. 



8. The adenoid tissue of the lymph nodules. 



