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HANDBOOK OF PHYSIOLOGY. 



cosce, and a single lymphatic or lacteal vessel rarely looped or branched 

 (fig. 263). 



The epithelium is continuous with that lining the other parts of the 

 mucous membrane. The cells are arranged with their long axis radiat- 

 ing from the surface of the villus (fig. 260), and their smaller ends 

 resting on the basement membrane. The free surface of the epithelial 

 cells of the villi, like that of the cells which cover the general surface 

 of the mucous membrane, is covered by a fine border which exhibits very 

 delicate striations, whence it derives its name, striated basilar border. 



Beneath the basement or limiting membrane there is a rich supply of 

 blood-vessels. Two or more minute arteries are distributed within each 

 villus; and from their capillaries, which form a dense network, proceed 

 one or two small veins, which pass out at the base of the villus. 



The layer of the muscularis mucosm in the villus forms a kind of 



Fig. 862. Vertical section of a villus of the small intestine of a cat. a, striated basilar border 

 of the epithelium; 6, columnar epithelium; c, goblet cells; d, central lymph-vessel; e, smooth mus- 

 cular fibres; /, adenoid stroma ot the villus in which lymph corpuscles lie. (Klein.) 



thin hollow cone immediately around the central lacteal, and is, there- 

 fore, situated beneath the blood-vessels. It is without doubt instru- 

 mental in the propulsion of chyle along the lacteal. 



The lacteal vessel in each villus is the form of commencement of the 

 lymphatic system of vessels * in the intestines. It begins almost at the 

 tip of the villus commonly by a dilated extremity. In the larger villi 

 there may be two small lacteal vessels which join on (fig. 263), or the 

 lacteals may form a kind of network in the villus. The last method 

 is rarely or never seen in the human subject, although common in some 

 of the lower animals (A, fig. 263). 



The Large Intestine. The Large Intestine, which in an adult 

 is from about 4 to 6 feet long, is subdivided for descriptive purposes 

 into three portions, viz. : the ccecum, a short wide pouch, communi- 

 cating with the lower end of the small intestine through an opening, 

 guarded by the ileo-c&cal valve; the colony continuous with the caecum, 



*For an account of the Lymphatic System, see Chapter IX. 



