CHAPTER VIII 



THE BLOOD. ITS RELATION TO THE LIVING 

 TISSUES 



56. WE have seen that the various food stuffs 

 rendered soluble by the processes of digestion 

 are taken into the blood. This fluid is brought 

 by the smaller vessels, the capillaries, into 

 close proximity to all the elements of the 

 living tissues. From the blood vessels a fluid 

 passes out through their walls and permeates 

 all the tissues, bathing their elements, so that 

 there is much truth in the aphorism that the 

 elements of the living tissues, and more especi- 

 ally the living cells, live like aquatic organ- 

 isms, that is to say, they live in a fluid, and 

 their lives and activities depend on inter- 

 changes between them and the fluid. This 

 fluid is the lymph. Some of it is used up in 

 the nutrition of the tissues, and the surplusage, 

 now containing in solution matters derived 

 109 



