CH. XXVI.] PROTEIDS OF SERUM 417 



Serum globulin and serum albumin. These substances exhibit the 

 usual differences already described between albumins and globulins 

 (p. 400). Both are coagulated by heat at a little over 70 C. They 

 may be separated by dialysis or the use of neutral salts.* The 

 readiest way to separate them is to add to the serum an equal volume 

 of saturated solution of ammonium sulphate. This is equivalent to 

 semi-saturation, and it precipitates the globulin. If magnesium 

 sulphate is used as a precipitant of the globulin it must be added in 

 the form of crystals, and the mixture well shaken to ensure complete 

 saturation. 



Serum globulin was formerly called fibrinoplastin, because it was 

 believed to take some share in fibrin formation. It is also called 

 paraglcibulin. It may be imperfectly precipitated by diluting 

 serum with twenty times its volume of water and then adding a 

 little dilute acetic acid, or passing a stream of carbonic acid gas 

 through the diluted serum. 



Fibrin-ferment. Schmidt's method of preparing it is to take 

 serum and add excess of alcohol. This precipitates all the proteids, 

 fibrin-ferment included. After some weeks the alcohol is poured off; 

 the serum globulin and serum albumin have been by this means 

 rendered insoluble in water ; an aqueous extract is, however, found 

 to contain fibrin-ferment, which is not so easily coagulated by alcohol 

 as the other proteids are. 



B. Extractives. These are non-nitrogenous and nitrogenous. 

 The non-nitrogenous are fats, soaps, cholesterin, and sugar, the 

 nitrogenous are urea (0'02 to 0*04 per cent.), and still smaller 

 quantities of uric acid, creatine, creatinine, xan thine, and hypo- 

 xanthine. 



C. Salts. The most abundant salt is sodium chloride; it con- 

 stitutes between 60 and 90 per cent, of the total mineral matter. 

 Potassium chloride is present in much smaller amount. It consti- 

 tutes about 4 per cent, of the total ash. The other salts are 

 phosphates and sulphates. 



Schmidt gives the following table : 



1000 parts of plasma yield 



Mineral matter ......... 8*550 



Chlorine 3*640 



SO S 0-115 



P 2 O 5 0-191 



Potassium 0'323 



Sodium 3-341 



Calcium phosphate 0'311 



Magnesium phosphate ....... 0*222 



* The globulin of the serum precipitated by *' salting out" really consists of 

 two proteids, one of which is precipitated by dialysis (euglobulin), and the other is 

 not (pseudo-globulin). 



2 D 



