450 



THE ALIMENTARY CANAL. 



[CH. XXVII. 



which cover the general surface of the mucous membrane, is sur- 

 mounted by a bright border which exhibits veiy delicate striations, 

 whence it derives its name, striated border (see pp. 27 29). 



Immediately beneath the basement nlembrane there is a rich 

 supply of blood-vessels. Two or more minute arteries are distri- 

 buted within each villus ; and from their capillaries, which form 



Fig. 383. A. Villus of sheep. B. Villiofman. (Slightly altered from Teichmann.) 



a dense network, proceed one or two small veins, which pass out 

 at the base of the villus. 



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

 of thin hollow cone immediately around the central lacteal, and 

 is, therefore, situated beneath the blood-vessels. It is instrumental 

 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, or the lacteals may form a network in the villus (fig. 383). 



