140 PHYSIOLOGICAL CHEMISTRY 



mainly of collagen, the yellow of elastin. Both forms contain 

 mucoid and extractives. 



The Blood. Many points in connection with the blood have 

 been considered elsewhere, chiefly in the discussion of hemo- 

 globin in the chapter on proteins. Some additional points 

 will be considered here. The blood is a fluid in which a variety 

 of formed elements, corpuscles and platelets, are suspended. It 

 is of the utmost importance as a circulating medium for it car- 

 ries oxygen, C0 2 , food materials, products of internal secretion, 

 various waste substances, heat, salts, etc., to or from the cells. 

 The blood is thus the common carrier of the body, delivering 

 fuel and other supplies to the cells, and carrying away the 

 cell refuse. Each cell is bathed in an aqueous fluid just as 

 were the original independent unicellular organisms which 

 lived in the sea. 



In recent years, much value has been attached to variations 

 in the amounts of the nonprotein constituents of the blood such 

 as urea, uric acid, creatinin, sugar, cholesterol, etc., in the diag- 

 nosis of disease. In the laboratory section will be found meth- 

 ods for the estimation of these various substances. In diabetes, 

 blood sugar is high, in nephritis the amount of uric acid first 

 increases, later that of urea, and still later that of creatinin. 

 The following table has been compiled from the work of various 

 investigators in this field, Hammett, MacLean and others. 

 Amounts are given in milligrams per 100 c.c. of blood. Insig- 

 nificant decimals have been omitted. 



Nonprotein constituents of blood in milligrams per 100 c.c. 

 blood: (Normal) 



Urea Uric Total non- Sugar Creatinine 



N acid prot. N 



10-25 0.5-1.16 27-45 85-166 0.37-0.6 



Cholesterol Chlorides 



140-180 524-584 



The general composition of the blood is as follows (from 

 Mathews) : 



