212 Agricultural Chemistry. 



When taken from an animal the plasma quickly deposits one of 

 its protein constituents, fibrin, which, entangling the corpuscles, 

 causes them to separate as a clot from the yellowish liquid the 

 serum. Blood plasma is therefore the liquid portion of fresh 

 blood, while blood serum is the liquid portion after clotting. The 

 latter differs from the former by having lost its fibrin and a 

 portion of its lime, magnesia and phosphoric acid. 



Blood is the nutrient fluid of the body. It is the source of 

 nourishment for all the cells. Out of its ingredients the tissues 

 are built. It contains about 8.1 per cent of water, so that it 

 easily holds in solution whatever soluble nutrients are furnished 

 it from the digestive tract. 



The 19 per cent of solids consists of the following materials: 

 10 per cent of haemoglobin ; 7 per cent of proteins ; about 1 per 

 cent of ash; the remaining 1 per cent consists of fats, sugars, 

 lecithin, etc. The color of the blood is due to haemoglobin. This 

 body is extremely complex in composition and contains about 

 0.4 per cent of iron. Haemoglobin is a dark purplish-red colored 

 substance. It readily combines with oxygen to an oxy-compound 

 which is bright red in color. The haemoglobin plays an import- 

 ant part in respiration as the carrier of oxygen to the tissues. 



The red corpuscles consist of circular, bi-concave discs, though 

 their shape and size vary in different animals. They are largest 

 in reptiles. In man the average diameter of a blood corpusle is 

 about 1/3200 of an inch, and its thickness about 1/12800 of an 

 inch. These corpuscles contain the haemoglobin, the coloring 

 matter of the blood. When they are treated with water or ether 

 they loose their coloring matter and leave a nitrogenous residue 

 which retains the shape of the original corpuscles. 



Bones consist of an earthy frame work composed mainly of 

 calcium phosphate, permeated by an albuminoid, called ossein, 

 and by nerves, blood vessels, etc. In the hollow center of many 

 bones is the marrow, which consists of fats and proteins. The 

 relative proportion of mineral and organic matter in bones varies 

 considerably. The amount of mineral matter in the green boi 



bone 



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