246 PHYSIOLOGICAL CHEMISTRY 



protein bodies, fibrinogen, nucleoprotein, serum globulin (euglobulin and 

 pseudo-globulin) and serum albumin. Plasma contains .about 8.2 per 

 cent of solids of which the protein constituents named above constitute 

 approximately 84 per cent and the inorganic constituents (mainly 

 chlorides, phosphates and carbonates) approximately 10 per cent. 

 Among the inorganic constituents sodium chloride predominates. To 

 prevent coagulation, blood plasma is ordinarily studied in the form of 

 an oxalated or salted plasma. The former may be obtained by allowing 

 the blood to flow from an opened artery into an equal volume of 0.2 per 

 cent ammonium oxalate solution, whereas in the preparation of a salted 

 plasma 10 per cent sodium chloride solution may be used as the diluting 

 fluid. 



Fibrinogen is perhaps the most important of the protein constituents 

 of the plasma. It is also found in lymph and chyle as well as in certain 

 exudates and transudates. Fibrinogen possesses the general properties 

 of the globulins, but differs from serum globulin in being precipitated 

 upon half -saturation with sodium chloride. In the process of coagula- 

 tion of the blood the fibrinogen is transformed into fibrin. This fibrin is 

 one of the principal constituents of the ordinary blood clot. 



The nucleoprotein of blood possesses many of the characteristics of 

 serum globulin. In common with this body it is easily soluble in sodium 

 chloride, and is completely precipitated from its solutions upon satura- 

 tion with magnesium sulphate. It is much less soluble in dilute acetic 

 acid than serum globulin, and its solutions coagulate at 65-69C. 



The body formerly called serum globulin Is probably not an indi- 

 vidual substance. Recent investigations seem to indicate that it 

 may be resolved into two individual bodies called euglobulin and pseudo- 

 globulin. The euglobulin is practically insoluble in water and may be 

 precipitated in the presence of 28-36 per cent of saturated ammonium 

 sulphate solution. The pseudo-globulin, on the contrary, is soluble in 

 water and is only precipitated by ammonium sulphate in the presence of 

 from 36 to 44 per cent of saturated ammonium sulphate solution. 



In common with serum globulin the body known as serum albumin 

 seems also to consist of more than a single individual substance. The 

 so-called serum albumin may be separated into at least two distinct 

 bodies, one capable of crystallization, the other an amorphous body. 

 The solution of either of these bodies in water gives the ordinary albu- 

 min reactions. The coagulation temperature of the serum albumin mix- 

 ture as it occurs in serum or plasma varies from 70 to 85C. according to 

 the reaction of the solution and its content of inorganic material. 

 Serum albumin differs from egg albumin in being more levorotatory, 

 in being rendered less insoluble by alcohol, and in the fact that when 



