36 



HUMAN PHYSIOLOGY. 



ABSORPTION. 



Absorption has for its object the introduction of new materials into the 

 blood, and takes place mainly from the alimentary tract, but also to some 

 extent from the skin, respiratory surface and closed cavities of the body. 



The Agents of Absorption are the veins and lymphatics. 



As a result of the process of digestion, the different alimentary substances 



FIG. 5. 



Di 



iagram of the portal vein (/z/) arising in the alimentary tract and spleen (s), and car- 

 rying the blood from these organs to the liver. From Yeo's Text-Book of Physiology. 



> 



are converted into forms which are capable of being absorbed into the 

 blood, e. g., albuminose, glucose and fatty emulsion, water and inorganic 

 matters undergoing no change, being already in a condition to be absorbed 

 and to play a part in the nutritive process. 



The blood vessels which are most active as absorbents, are the gastric, 

 superior and inferior mesenteric veins. They arise in the coats of the 



