162 STUDENTS HISTOLOGY 



located, properly speaking, in the submucosa and between the 

 villi. In the drawing, their bases do not all appear in the sub- 

 mucosa, inasmuch as the nodules are cut in different planes.) 



4. Muscularis mucosae. The elongated nuclei of the involun- 

 tary muscular elements. 



5. The submucosa. (a) The blood-vessels. (ft) 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 one to differentiate.) 



(HO 



6. The villi. (a) The covering columnar cells. (&) Goblet 

 cells scattered between the last. (These 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 

 circumstances, 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.) GO 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 lymphoid or adenoid tissue of the lymph -nodules. 



Mount also sections of (1) DUODENUM, to show Brunner's glands, which 

 occur there only. (2) LARGE INTESTINE (human), -which has no villi nor val- 

 vulse conniventes. The crypts of Lieberkiihn and solitary follicles are abun- 

 dant. (3) VERMIFORM APPENDIX (human), observe the abundant lymphoid 

 tissue . 



