BLOOD. 183 



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 con- 

 stituents 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 globu- 

 lin in being precipitated upon half -saturation with sodium chloride. 

 In the process of coagulation of the blood the fibrinogen is trans- 

 formed 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 solu- 

 tions upon saturation with magnesium sulphate. It is much less 

 soluble in dilute acetic acid than serum globulin and its solutions 

 coagulate at 65-69 C. 



The body formerly called serum globulin is probably not an in- 

 dividual 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 pseudoglobulin, 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 albu- 

 min seems also to consist of more than a single individual sub- 

 stance. The so-called serum albumin may be separated into at least 

 two distinct bodies, one capable of crystallization, the other an amor- 

 phous body. The solution of either of these bodies in water gives 

 the ordinary albumin reactions. The coagulation temperature of 

 the serum albumin mixture as it occurs in serum or plasma varies 

 from 70 to 85 C. according to the reaction of the solution and 

 its content of inorganic material. Serum albumin differs from egg 

 albumin in being more laevorotatory, in being rendered less insolu- 

 ble by alcohol, and in the fact that when precipitated by hydro- 

 chloric acid it is more easily soluble in an excess of the reagent. 



