CHAPTER II 

 THE BLOOD 



BLOOD is a red, opaque, salty fluid, having a character- 

 istic smell and a specific gravity of 1.053-1.066. It has an 

 alkaline reaction, the alkalinity being equal to that of a 

 0.2-0.4^ sodium carbonate solution. 



The blood circulates through the entire animal body in a 

 closed system of vessels which is exceedingly ramified. 

 The most important physiological import of blood is to carry 

 foodstuffs to the organs and to remove the metabolic 

 products. 



Blood is composed of a clear yellowish fluid, the plasma* 

 in which are suspended the solid constituents, the red and 

 white blood corpuscles. Histologically considered, blood is 

 a tissue with a liquid intercellular substance. 



Blood coagulates within a few minutes after leaving the 

 vessels, i.e. it clots to a jelly-like mass. The coagulation 

 depends upon the separation of a proteid from the plasma, 

 the fibrin, which forms a fibrous mass inclosing the blood 

 corpuscles in its meshes. Gradually the clot shrinks, thereby 

 pressing out a clear, faintly yellowish fluid, the blood serum. 

 The coagulum with the inclosed corpuscles is called the 

 clot. Plasma is composed of serum and the fibrin-forming 

 proteid. Serum is plasma without its fibrin-forming proteid. 

 Blood from which the fibrin has been removed by whipping 

 (e.g. with a rod) is called defibrinated blood, and is com- 

 posed of serum and corpuscles. In whipping blood, the 

 fibrin clings to the rod. 



The quantity of blood in man is about 7.5^ of the body 



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