CHEMICAL EXAMINATION OF THE BLOOD. 315 



Properties. As the term indicates, serum-globulin belongs to the 

 class of globulins. In its moist state it represents a snowy-white, 

 finely flocculent mass, which is not tough and elastic like fibrinogen. 

 From its solutions the substance can be precipitated, as already in- 

 dicated, by saturation with magnesium sulphate or by half-saturation 

 with ammonium sulphate. Sodium chloride causes only an incom- 

 plete separation of the substance when added to saturation, while 

 half-saturation is of no effect at all. It is thus an easy matter to 

 isolate serum-globulin when fibrinogen is present. An incomplete 

 separation also occurs when its neutral or feebly acid solutions (using 

 acetic acid) are diluted from ten to twenty times with distilled 

 water, or by passing a stream of carbon dioxide through such dilute 

 solutions. In the presence of from 5 to 10 per cent, of sodium chlo- 

 ride its solutions coagulate at 75 C. They cause a rotation of the 

 polarized light to the left, the specific degree corresponding to 47.8. 



According to Morner, serum-globulin yields a reducing substance 

 when boiled with dilute mineral acids. It might thus be supposed 

 that serum-globulin is in reality a glucoproteid, and not a native 

 albumin, but it is possible also that the reaction is due to the acci- 

 dental presence of a glucoproteid, which is thrown down together 

 with the globulin. 



Though serum-globulin is usually spoken of as a unity that is, 

 an individual substance it appears likely that the compound which 

 is thrown down upon saturation with magnesium sulphate repre- 

 sents a mixture of several globulins. If this material is thus dis- 

 solved in dilute saline solution and subjected to dialysis, a precipitate 

 forms which possesses all the properties of serum-globulin which we 

 regard as characteristic of globulins. The remaining solution, how- 

 ever, contains an albuminous substance which may be thrown down 

 by magnesium sulphate, and which when isolated in this manner 

 differs only from the first precipitate in being soluble in water. 

 Formerly it was thought that all globulins are insoluble in water, 

 but it is thus shown that at least one form differs in this respect. 



The globulin which is obtained from blood-plasma is also spoken 

 of as plasma-globulin, in contradistinction to the so-called cell- 

 globulin ; and Hammarsten's secondary globulins, which are found 

 in the serum together with plasma-globulin, are thought to result 

 from disintegration of the leucocytes and the fibrinogen molecule, 

 respectively. Accordingly we also find more serum-globulin in the 

 serum than in the plasma. Chemically, these various globulins are 

 not sufficiently characterized to warrant a separate description, and 

 as they are all thrown down together with our present methods of 

 isolation, it follows that the numerical datti regarding the elementary 

 composition of serum-globulin as unity must also be more or less 

 at fault. We find, as a matter of fact, that these data are by no 

 means constant. The value of carbon thus varies between 52.32 and 

 53.3, and that of nitrogen between 15.61 and 16.25, which would 

 represent a difference of nearly 1 and 0.64 per cent., respectively 



