

''THE BLOOD. 175 



and round, from place to place, by the heart, the blood picks 

 up nourishing things in its course through the walls of 

 the alimentary canal, and oxygen as it flows through the 

 lungs; it then carries them to all other parts of the body. 



The Removal of Wastes. The rapidly flowing blood not 

 only conveys a supply of nutritive material for all the 

 organs, but is a sort of sewage stream that drains off their 

 wastes (p. 108), and carries them to the excretory organs, by 

 which they are sent entirely out of the body. 



The blood is a middleman: on the one hand, between the 

 receiving organs (lungs and alimentary canal) and all the 

 rest; and on the other hand, between the excretory organs 

 and all the others. Each part is thus 'kept in a well-fed 

 and healthy state, though it may lie far distant from all 

 places where new materials first enter the body, and from 

 those where refuse and deleterious substances are finally 

 passed from it. 



The Blood, as every one knows, is a red liquid which is 

 yery widely distributed over the body, since it flows from 

 any part of the surface when the skin is cut through. 

 There are very few portions of the body into which blood 

 is not carried. One of them is the outer layer of the skin;* 

 hairs and nails, the hard parts of the teeth and most carti- 

 lages also contain no blood; these non-vascular tissues are 



Where does the blood receive nutritive matters? Oxygen? 

 What does it do with them? 



What part does the blood play in the removal of wastes? 



State briefly the functions of the blood with reference to the 

 nutritive processes of the body 



What is blood? How do we know that it is widely distributed? 

 Name parts into which blood does not flow. How are the non- vas- 

 cular tissues nourished? 



* The absence of blood in the superficial layer of the skin may be readily 

 shown: take a fine needle threaded with silk; by taking shallow stitches a pat- 

 tern can be easily embroidered on the palm or back of the hand without draw 

 ing a drop of blood, 



