THE BLOOD. 415 



probable agencies is to introduce air into the stomach, to 

 act upon its lining membrane and produce from it one 

 of the constituents of the gastric juice. The solvent 

 agency of this fluid is in part owing to the ferment 

 thus formed, and in part to the free acids which it con- 

 tains in solution. The latter are phosphoric, hydro- 

 chloric, butyric, and lactic acids, in part free, and partly 

 in the form of salts. 



1035. COMPOSITION OF THE BLOOD. 



Give the com- 



position of the If fresh blood is beaten with a branched 

 blood ' stick, it is separated into a slightly alka- 



line liquid, called the serum, a fibrous material called 

 fibrine, and red globules, which sink, after a time, to 

 the bottom of the vessel. The fibrine adheres in threads 

 to the stick with which the operation is performed. It 

 is analogous, in composition and properties, to the vege- 

 table gluten from which it is formed. The serum con- 

 tains albumen, and resembles the white of egg. The 

 globules are also principally albumen, with a small 

 proportion of a red coloring matter called hematosine. 

 Albumen and fibrine both contain phosphate of lime or 

 bone earth. The serum contains, also, certain salts, 

 and a small proportion of fat. All of these substances 

 together form but about one-fifth of the blood ; the 

 remaining four-fifths are water. When blood is left to 

 stand, after being drawn from the body, the fibrine coag- 

 ulates spontaneously, entangling and taking with it the 

 red globules, and thus separating them from the serum. 



1036. ANIMAL NUTRITION. It is evident 



What niateri- /. , -, . 1,1 -u 



ah arc. found irom the preceding paragraph that much 

 ready formed O f the mater j a i required to build up the 



in the blood ? r 



body, is found ready formed in the blood. 



