ABSORPTION. 



215 



extremity a narrow border of the cell presents a striated appearance, as if it 

 were composed of small rods embedded in some cement substance. Goblet 

 or mucin-holding cells are also to be found among the columnar cells. The 

 body of the villus, that portion within the basement membrane, consists of a 

 reticulated connective tissue supporting arteries, capillaries, veins, and 

 lymphoid corpuscles. In the center of the villus there is usually a single, 

 though at times a double, club-shaped lymph-capillary, the walls of which 

 are composed of endothelial cells with sinuous margins. This capillary 



<Zs 



FIG. 91. LONGITUDINAL SEC- 

 TION OF A VILLUS FROM IN- 

 TESTINE OF THE DOG, HIGHLY 

 MAGNIFIED, a. Columnar epi- 

 thelium containing goblet-cells (ft) 

 and migratory leukocytes (h). c. 

 Basement membrane, d. Plate- 

 like connective-tissue elements of 

 core, e, e. Blood-vessels. /. Ab- 

 sorbent radical or lacteal. 

 (Piersol.) 



FIG. 92. SECTION OF INJECTED SMALL 

 INTESTINE OF CAT. a, b. Mucosa. g. 

 Villi. i. Their absorbent vessels, h. Sim- 

 ple follicles, c. Muscularis mucosae. ;'. Sub- 

 mucosa. g, e'. Circular and longitudinal 

 layers of muscle. /. Fibrous coat. All the 

 dark lines represent blood-vessels filled with 

 the injection mass. (PiersoL) 



probably begins by a blind extremity and opens at the base of the villus into 

 the subjacent lymph-vessels. The communicating orifice is guarded by a 

 valve. It is also surrounded by a layer of non-striated muscle-fibers, 

 arranged longitudinally, derived from the muscularis mucosae and attached 

 toj;he apex of the body of the villus. 



" The arteries which penetrate the villi are derived from those of the sub- 

 mucous coat of the intestine, which are the ultimate branches of the intestinal 

 artery, and serve the purpose of delivering nutritive material to the capillary 

 plexus (Fig. 92). While passing through the latter a portion of the blood- 

 plasma transudes through the capillary walls into the spaces of the reticu- 



