90 



PRACTICAL MICROSCOPY. 



the. crypts, when it becomes mingled with the secretion previously 

 mentioned, and constitutes the succus entericus. 



We have then seen that the succus entericus is secreted, partly 

 from the epithelial cells covering the villi (or, in other words, sur- 

 rounding the crypts) and partly from Ihe cells of B runner's glands. 



THE REMAINING STRUCTURES OF THE INTESTINE CONCERNED 

 MAINLY IN FOOD ABSORPTION. 



The diagram (Fig. 67) is intended to show the same layers as were 

 indicated in the previous figure (Brunner's glands and the blood-ves- 

 sels have been omitted in order to avoid confusion). The villi and 

 crypts are seen as before. 





FIG. 67. DIAGRAM SHOWING PORTIONS OF INTESTINAL Mucous MEMBRANE, CONCERNED IN 



ABSORPTION. 



A. Mucosa. 



B. Muscularis mucosae. 



C. Submucosa. 



D. D. Villi. 



E. F. Crypts of Lieberkiihn. 

 G, G. Lacteals. 



H, H. Chinks and intercommunicating channels of the lymph plexus of the submucosa. 

 I. Bottom of a mass of adenoid tissue a so-called solitary gland. Peyer's patches are 

 formed of aggregations of these nodules. 

 J. Efferent lactial or lymph duct. 



In the centre of each villus is the blind tube Gr Gr, a part of the 

 lymphatic system, and here called a lacteal. When, during digestion, 

 the minute globules of fatty food reach the small intestine, they are 

 grasped by the epithelial cells covering the villi, and are carried event- 

 ually within the body of the villus to this lacteal. 



