194 ABSORPTION. 



crowded with oily particles, taken up by absorption from the intestinal 

 cavity. (Fig. 61.) The oily matter then passes onward, penetrating 

 deeper into the substance of the villus, until it is at last received by the 

 capillary vessels in its interior. 



Absorption by the Bloodvessels. The final absorption of the digested 

 fluids is accomplished mainly by the bloodvessels of the intestinal villi. 

 Their situation, their numbers, and the rapid movement of the blood 

 through these channels, are all circumstances especially favorable for 

 the performance of this function. The capillary plexus of each villus 

 is situated in the most superficial part of its substance, almost immedi- 

 ately beneath the epithelium cells which cover its surface, so that the 

 absorbed fluids, after passing through the epithelial layer, come at once 

 in contact with the capillaries of the vascular network. The exten- 

 sion of absorbing surface, from the repeated division and inosculation 

 of these vessels, and the constant renovation of the fluids which they 

 contain, by the movement of the circulation, provide for their constant 

 activity, and drain away the absorbed fluids from the substance of the 

 villus as fast as they are taken up by its exposed surface. 



Fig. 62. 



CAPILLARY BLOODVESSELS OF THE INTESTINAL VILLI; from the Mouse. 



(KOlliker ) 



The activity of the bloodvessels in the process of absorption is also 

 a matter of direct observation. Abundant experiments have demon- 

 strated, not only that soluble substances introduced into the intestine 

 may be soon afterward detected in the blood of the portal vein, but 

 that absorption takes place more rapidly and abundantly by the blood- 

 vessels than by the lacteals. This was first shown by Magendie, 1 who 

 found that the absorption of poisonous substances would take place, in 

 the living animal, both from the cavity of the intestine and from the 

 tissues of the lower extremity, notwithstanding that all communication 

 through the lacteals and lymphatics was cut off, and the passage by the 



1 Journal de Physiologic. Paris, 1825, tome i. p. 18. 



