BLOODVESSELS OF INTESTINAL MUCOUS MEMBRANE. 597 



twigs ascend without branching between the gland tubes to 

 supply the villi. 



There are no proper veins formed from the capillaries sur- 

 rounding the tubular glands, but the vessels collectively trans- 

 mit blood into the capillaries of the villi. We must therefore 

 regard the capillaries of the intestinal mucous membrane 

 and of the villi as forming a common system, except that 

 the latter receive special accessory arterial branches. The 



Fig. 117. 



Fig. 117. Vascular plexus of the intestinal mucous membrane, seen in 

 transverse section. 



capillary system of the villi lies close to the surface, being 

 separated from the epithelium by only a delicate homogeneous 

 layer, and is tolerably close (fig. 117). It consists essentially 

 of tubes, averaging 0'009 of a millimeter in diameter, which 

 pursue a slightly tortuous course in the long axis of the villi, 

 and communicate by numerous transverse tubules. 



The arterial twigs above alluded to, arising directly from the 

 vascular plexus of the mucous membrane, run singly or several 

 in number to the villi, in which, after a short course, they 

 break up into capillaries, and their terminal branches, after 

 forming loops, may frequently be seen to enter the venous 

 radicles. The relative numerical proportion of the longitudinal 



