224 



INTESTINAL DIGESTION. 



cement-substance, and the reticulum of the matrix of the villus is 

 continuous from the interior of the villus through this interstitial 

 substance to its exterior. Next the basement-membrane is a 

 plexus of capillary blood-vessels. Still more interior is muscular 

 tissue, a part of the muscularis mucosae, while the central structure 

 of all is a lacteal. 



The capillary plexus, muscular tissue, and lacteal are sur- 

 rounded by reticular tissue constituting the matrix of the villus, 

 and in the interstices of this are lymph-corpuscles and the cells of 



FiG. 119. Longitudinal section through summit of villus from human small 

 intestine ; X 900 (Flemming's solution) : at a is the tissue of the villus axis ; &, 

 epithelial cells; c, goblet-cell; d, cuticular zone (Bohm and Davidoff). 



the villus ; large, flat cells with oval nuclei. If the components of 

 a villus are named in the reverse order to that just given, we shall 

 have, starting from the center, (1) lacteal, (2) muscular tissue, 

 (3) capillary plexus, (4) basement-membrane, (5) columnar epi- 

 thelium. The lacteals are single in some of the villi and in others 

 double. Their walls consist of a single layer of endothelium, and 

 the cement-substance between the cells is continuous with the 

 reticular tissue composing the matrix. It will be seen, therefore, 

 that from the lacteal to the surface of the villus there is continuous 

 reticular tissue. This is regarded by Dr. Watney as the path 



