PLASMA 83 



tions, as sodium or magnesium sulphate, it will not clot. The 

 corpuscles may then be allowed to sink, or they may be cen- 

 trifugalized off. The method of action of the salt is not 

 known. 



Peptones and albumoses, when injected into an animal, 

 will prevent the clotting of its blood for a long time. But 

 peptone added to blood already shed has no such effect. The 

 action of the peptone in the body is explained in that it causes 

 a rapid destruction of leukocytes. This sets free two sub- 

 stances a nucleoprotein and histon. The first takes part in 

 the formation of fibrin ferment, which is destroyed by the 

 liver, while the second, which is known to be antagonistic to 

 the coagulation of the blood, is left in the bloodvessels. The 

 addition of oxalate solutions by precipitating the soluble calcium 

 salts will prevent coagulation. 



Plasma consists of water, at least three kinds of simple pro- 

 teins, combined proteins, extractives, and salts. The simple 

 proteins are serum albumin, serum globulin, and fibrinogen. 

 The serum albumin is separated from the other two by satura- 

 tion with magnesium sulphate, which leaves it in solution, 

 while it precipitates the globulins. It may be brought down 

 in a neutral or acid medium by heat, which gives three different 

 coagulations at 73, 77, and 84 C. respectively, indicating 

 three kinds of serum albumin. In man it forms about 4.52 

 per cent, of the solids. Its source is the absorbed foodstuffs. 

 Serum globulin (par a globulin) is coagulated at 75 C. In man 

 it forms about 3.1 per cent, of the solids present, and is more 

 abundant in serum than in plasma, on account of the dis- 

 integration of the white blood corpuscles, which takes place 

 during coagulation. Whether this is its sole source is not 

 known. Paraglobulin does not behave like a chemical individual. 

 Portions of it are precipitable by carbon dioxide, and other por- 

 tions not. Furthermore, a one-third saturation with ammonium 

 sulphate will bring down a fraction of the total protein only. 

 This portion is now known as euglobulin. A less easily pre- 

 cipitable portion, pseudo globulin, will not come down until 

 one-half saturation with ammonium sulphate has been reached. 



Fibrinogen is another globulin coagulating at from 56 to 

 60 C. It is present in human blood to the extent of 0.22 to 

 0.4 per cent. Its nutritive value to the body and its source 



