CHAP. XXV.] THE VILLI. 229 



basement membrane. From this arise at various points small veins, 

 which pass out of the villus in one or more trunks (fig. 162). 



The cavity of the villus also contains one or more small lacteals, 

 in which originates the proper lacteal plexus of the intestine. The 

 villi are seen white with chyle, during the absorption of that fluid, 

 and the chyle may be fixed in them by coagulation, if the membrane 

 is promptly immersed in alcohol. Respecting the manner in which 

 these vessels are disposed in the villus, however, nothing certain is 

 known. Some have described a net-work of these vessels extending 

 to the extremity of the villus. The investigation is one of the 

 most difficult in minute anatomy, and is highly important as bearing 

 upon the mechanism of the absorption of chyle. 



Capillary plexus of the villi of the human small intestine, as seen on the surface after a 

 successful injection, magnified 50 diam. 



Nothing whatever is known of the relation of the nerves to the 

 villi. The tissue which occupies the cavity of the villus, and which 

 supports the capillary plexus, and whatever other vessels may exist 

 in it, is a soft, imperfectly formed areolar tissue, containing nuclei 

 and granules, and resembling somewhat the tissue contained in the 

 gustatory papillae of the tongue. That portion of it which cor- 

 responds to the free extremity of the villus differs from the rest ; it 

 exhibits a vesicular structure, and resembles very minute fat vesi- 

 cles filled by some transparent fluid. The tissue which occupies 

 the remainder of the villus seems to consist chiefly of nuclei or 

 granules, some of which present an indistinct arrangement in 

 columns, which are parallel to the axis of the villus. During the 

 process of chylification it appears to be the seat of some very 

 remarkable changes connected with the absorption of chyle. 



