SERGLOBULINS. 259 



cannot be completely and positively separated from each other. The 

 mixture of globulins obtained from blood-plasma or blood-serum by 

 saturation with magnesium sulphate or half-saturation with ammonium 

 sulphate consists of nucleoprotein, fibrin-globulin, and the true serglobulin 

 or mixture of globulins. 



The nucleoprotein has been previously 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^SCU even in 28 per 

 cent solution. 



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 l also differentiates between 

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

 later investigations of HOFMEISTER and PiCK 2 the part insoluble in 

 water corresponds chiefly to a globulin fraction readily precipitated by 

 (NH4)2SO4 (by 28-36 vols. per cent saturated solution), and the part 

 soluble in water corresponds to a fraction difficult to precipitate (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^SCU into three 

 fractions 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 MELLANBY 

 HASLAM and recently by WIENER. 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 



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



2 Hofmeister's Beitrage, 1. 



3 Hofmeister's Beitrage, 3. 



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



5 Mellanby, Journ. of Physiol., 36; Haslam, ibid., 32; Wiener, Zeitschr. f. physiol 

 Chem., 74. 



