222 



INTESTINAL DIGESTION. 



Valvulce Conniventes. The mucous coat of the intestine is 

 arranged in folds, to which the name valvulce conniventes has been 

 given (Fig. 116). These folds, which begin about 2 cm. below 

 the pylorus, are present throughout the length of the small intes- 

 tine, excepting in the lower part 

 of the ileum. They are more 

 abundant in the upper half of 

 the intestine, where they have 

 been counted to the number of 

 600, than in the lower half, 

 where only 250 have been found, 

 making about 850 in all. These 

 folds are arranged around the 

 interior of the intestine at right 

 angles to its long axis. They do 

 not completely encircle it like a ring, but vary in length, some 

 extending about two-thirds and others only one-third the distance 

 around. The widest of them is not more than 1.5 cm. in width, 

 projecting into the caliber of the intestine to this extent. Each 

 is a double fold of mucous membrane with connective tissue be- 

 tween, which so binds the folds together that even in the condi- 

 tion of distention the valvulse conniventes are not obliterated, as 



FIG. 116. Portion of the wall of the 

 small intestine, laid open to show the 

 valvulae conniventes (Brinton). 



FIG. 117. Mucous membrane of the jejunum, highly magnified (schematic) : 

 1, 1, intestinal villi ; 2, 2, closed or solitary follicles ; 3, 3, orifices of the follicles 

 of Lieberkuhn (Testut). 



is the case with the rugae of the stomach. By means of these 

 foldings the extent of the mucous membrane is greatly increased 

 over what it would be did it simply line the intestine. 



Villi. Projecting from the mucous membrane including the 



