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CHAPTER XIII. 



ABSORPTION. 



ABSORPTION is another function, related to nutrition, 

 which deserves special notice. The principal object of this 

 function is the removal of such materials as have been al- 

 ready deposited, and have become either useless or injurious, 

 and their conveyance into the general mass of circulating 

 fluids; purposes which are accomplished by a peculiar set of 

 vessels, called the Lymphatics. These vessels contain a 

 fluid, which, being transparent and colourless like water, has 

 been denominated the lymph. The lymphatics are perfect- 

 ly similar in their structure, and probably, also, in their mode 

 of action, to the lacteals, which absorb the chyle from the 

 intestinal cavity: they are found in all the classes of verte- 

 brated animals, and pervade extensively every part of the 

 body. Exceedingly minute at their origin, they unite to- 

 gether as they proceed, forming larger and larger trunks, 

 generally following the course of the veins, till they finally 

 discharge their contents either into the thoracic duct, or into 

 some of the large veins in the vicinity of the 

 heart. Throughout their whole course, they 

 are, like the lacteals, provided with numerous 

 valves, which, when the vessel is distended 

 with lymph, give it a resemblance to a string 

 of beads, Fig. 378.* In the lower animals, it 

 appears that the veins are occasionally en- 

 dowed with a power of absorption, similar to that possessed 



* In warm-blooded animals, the lymphatics are made to traverse, in some 

 part of their course, certain bodies of a compact structure, resembling glands, 

 and termed, accordingly, the lymphatic glands. One of these is represented 



