SERGLOBULINS. 251 



The nucleoproteir. has already been discussed. The fibrin-globulin, 

 which occurs in the serum only in small amounts, can be completely pre- 

 cipitated by NaCl. It has the general properties of the globulins, but 

 differs from the serglobulins by a lower coagulation temperature, 64- 

 66 C., and also in that it is precipitated by (NH^SC^ even at 28 per 

 cent saturation. 



Serglobulins. If the globulin obtained by saturation with magnesium 

 sulphate is dialyzed, then, as has been known for a long time and further 

 substantiated by MARCUS, only a part of the globulin separates out, 

 while a portion remains in solution and cannot be precipitated by the 

 addition of acid. For this reason MARCUS 1 also differentiates between, 

 a water-soluble globulin and one insoluble in water. According to the 

 recent investigations of HOFMEISTER and PiCK 2 the part insoluble in 

 water corresponds chiefly to a globulin fraction readily precipitated by 

 (NH 4 ) 2 SO4 (by 28-36 vols. per cent saturated solution), and the part 

 soluble in water corresponds to a more difficultly precipitable fraction 

 (by 36-44 vols. per cent saturated solution). The first fraction is called 

 euglobulin and the second pseudoglobulin. According to FORGES and 

 SPIRO 3 the serglobulins can be separated by (NH 4 ) 2 SO4 into three frac- 

 tions whose precipitation limits are 28-36, 33-42, and 40-46 vols. per 

 cent saturated solution. All three fractions contain globulin insoluble 

 in water. FREUND and JOACHIM 4 have found that the euglobulin as 

 well as the pseudoglobulin fraction is a mixture of globulin soluble in 

 water and globulin insoluble in water, and consequently the number of 

 different globulins in the serum may be still greater. 



It follows from all these investigations that either the difference between 

 the globulin soluble in water and that insoluble is not sufficient or that the frac- 

 tional precipitation with ammonium sulphate is not suited for the separation of 

 the various globulins. This latter seems to be the case, as shown by HASLAM 5 . 

 It must not be forgotten that the globulin fractions are always contaminated 

 with other serum constituents, and that these may influence the solubility and 

 precipitability. ' As HAMMARSTEN has shown, a water-soluble globulin can be 

 transformed into a globulin insoluble in water by careful purification, and also 

 the reverse, namely, a globulin insoluble in water can sometimes be converted 

 into one soluble in water by allowing it to lie in the air. An insoluble protein 

 like casein can also, according to HAMMARSTEN, 6 have the solubilities of a globulin 

 due to contamination with constituents of the serum, and K. MORNER 7 has also 



groups of proteins, the globulins and albumins can be accomplished by saturation with. 

 MgSO 4 of half-saturation with (NH 4 ) S SO 4 . 



1 Zeitschr. f . physiol. Chem., 28. 



2 Hofmeister's Beitrage, 1, 



3 Hofmeister's Beitrage, 3. 



4 Zeitschr. f. physiol. Chem., 36. 



5 Journ. of Physiol., 32. 



8 See Hammarsten, Ergebnisse d. Physiol., 1, Abt. 1. 

 T Zeitschr. f. physiol. Chem., 34. 



