CHAPTER XV 



BLOOD AND ITS 

 IMPORTANCE 



William Harvey. 



Vesalius' idea of blood vessels. 



What iff the relation of blood to the other tissues of the body? Where is 

 hlood made and where are its various parts destroyed? What is meant 

 by different types of blood? What /.v the importance of blood tests? 



Many cells are far from the source of supply of food and oxy- 

 gen and far from the organs which will excrete their wastes. 

 The blood, therefore, acts as a medium for the distribution of 

 food materials and oxygen to the cells, and for the collection of 

 wji-tcs from the cells. 



Circulation is the ceaseless movement of blood through the 

 body in a system of closed tubes called blood vessels which branch 

 to all parts of the body. When blood flows from any. part of the 

 body, blood vessels have been broken. 



Problem. Study of the blood. 



Secure some freshly drawn blood from a butcher or slaughterhouse. Keep 

 in a tightly corked lx>ttle when not in use. 



I. Pour two or three ounces of the blood into an open dish and beat it 

 vigorously with a few broom strau ^. 



A. Describe the nature of the material removed by this beating. This 

 material is called fibrin. As the beating exposed the blood to the air, 

 the liquid blood protein, fibrinogen, was converted into the solid form, 

 fibrin. 



B. Describe the material left in the dish. This is defibrinated blood. 



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