THE REASON WHY. 213 



w Let every thing that hath breath praise the Lord. Praise ye the Lord." 

 PSALM CL. 



carbon, by which a gentle heat is diffused throughout the sys- 

 tem. It is for this purpose that fresh air is so constantly 

 necessary. 



But other exchanges take place. The blood, in addition to 

 oxygen and carbon, contains hydrogen and nitrogen. But it contains 

 its four elements in various forms of combination, producing the 

 following materials for the use of the body : of 1 ,000 parts of blood, 

 about 779 are tvater ; 141 are red globules ; 69 are albumen ; 3 are 

 fibrin ; 2 are fatty matter ; 6 are various salts. 



Albumen and fibrin are a kind of flesh imperfectly formed, and 

 probably are chiefly used in repairing the muscles. The red 

 corpuscles contain the oxygen which goes to combine with the 

 superabundant carbon, and develope heat ; the fatty matters 

 probably repair the fatty tissues, and glands that are of a fatty 

 nature ; and the various salts contribute to the bones, and to the 

 chemical properties of those secretions which are formed by the 

 glands, &c., while the great proportion of water is employed in 

 cleansing, softening, and cooling the whole, or the living edifice, 

 and it is "the medium through which all the nutrition of the body is 

 distributed. 



900. Why do we feel the pulse beat ? 



Because every time that the heart contracts it send a fresh supply 

 of blood to the blood-vessels, and the motion thus imparted creates 

 a general pulsation throughout the system : but it is more distinctly 

 perceived at the pulse, because there a rather large artery lies near 

 to the surface. 



901. What becomes of the matter collected ly the blood in 

 the course of its circulation ? 



We have already explained that carbon is thrown off from the 

 lungs in the form of carbonic acid gas. But there are many other 

 matters to be separated from the venous blood, and its purification 

 is assisted by the action of the liver, which is supplied with a large 

 vein, called the portal vein, which conveys into the substance of the 

 liver, a large proportion of the venous blood, from which that organ 

 draws off those matters wliich form the bile, and other matters 

 which are transmitted with the bile to the bowels. The liver and 



