346 



OF DIGESTION ANI> NUTRITIVE ABSORPTION. 



Fig. 85. Fig. 86. 



Vessels of an Intestinal Villus of a Hare, from a 

 dry preparation by Dollinger; 1, 1, veins filled 

 with white injection; 2, 2, arteries injected red. 

 Magnified about 45 diameters. 



A. apex of intestinal villus from the duodenum 

 of human female ; B, a mesh of the vascular net- 

 work, 1. 1. filled up with delicate cellular tissue. 2. 

 Magnified about 45 diameters. (After Wagner.) 



Fig. 87. 



Man thoy are commonly cylindrical or nearly so ; but in many of the lower 

 animals they are spread out into broader laminae at their base, and are con- 

 nected together so as to form ridges or folds. It was formerly believed that 

 the villi were not supplied with blood-vessels. So far is this from being the 

 case, however, that in each villus there is a minute plexus of blood-vessels, of 

 which the larger branches may even be seen with the naked eye, when they 

 are distended with blood. It can scarcely be doubted that through these 

 capillaries takes place the absorption of fluid from the digestive cavity, which 

 will be immediately stated to convey a portion of their contents directly into 

 the veins ( 463). The Lacteal vessels, which are distributed upon the walls 

 of the intestine, but not upon those of the stomach, 

 occupy the interior of the villi of the former ; each 

 lacteal tube commencing, as it were, in the midst of 

 the tissue of a villus. The accompanying figure 

 represents the appearance offered by the incipient 

 lacteals in the villi of the jejunum of a young man, 

 who had been hung soon after taking a full meal of 

 farinaceous food. The lacteal that issued from each 

 villosity arose by several smaller branches, in some of 

 which free extremities could be traced, whilst others 

 anastomozed with each other. It is certain that the 

 lacteals never open by free orifices on the surface of 

 the intestine, as was formerly imagined; and the same 

 is true of the lymphatics, which originate in the sub- 

 stance of the various tissues. From the recent ob- 

 servations of Mr. Goodsir,* it appears that the villi are 



One of the intestinal villi, 

 with the commencement of a 

 lacteal. After Krause. 



* Edinb. New Phil. Journal, July, 1842. 



