38 PRACTICAL PHYSIOLOGY. [V. 



acid and ferrocyanide of potassium; Millon's reagent; and the 

 NaHO and CuSO^ reaction (Lesson I. 1). Alcohol causes coagu- 

 lation. 



{(•.) Saturate it with ammonium sulphate. ThLs precipitates all 

 the proteids, globulin and albumin. Filter , the filtrate is proteid- 

 free. 



Study its individual proteids. 



(A.) Preparation of Serum-Globulin (Paraglobulin). 



(a.) A, Schmidt's Method.— To lo cc. of serum add 200 cc. of ice-cold 

 water, and pass a stream of carbon dioxide through it for some time = a white 

 precipitate of serum-globulin. This method does not precipitate it entirely. 

 No precipitate is obtained unless the serum be diluted. 



(h.) Panum's Method. — Dilute i cc. of serum with 15 cc. of water; add 5 

 drops of a 2 per cent, solution of acetic acid = a white precipitate of serum- 

 globulin, or, as it was called, " serum-casein." AU the serum-globulin is not 

 precipitated. 



(c.) Hammarsten's Method. — Saturate serum with magnesium 

 sulphate, and shake briskly for some time. An abundant precipi- 

 tate of serum-globulin is obtained. Allow the excess of the salt 

 and the precipitate to settle. The undissolved crystals fall to the 

 bottom, and on their surface is precipitated a dense white fiocculent 

 mass of serum-globuUn. Filter. "Wash the precipitate on the 

 filter with a saturated solution of magnesium sulphate , add a httle 

 distilled water to the precipitate. It is dissolved, i.e.j it is a globulin, 

 and is insoluble in excess of a neutral salt, but is dissolved by a 

 weak solution of the same. The solution does not coagulate spon- 

 taneously. It gives all the reactions for proteids with the special 

 reactions of a globulin. 



(d.) Kauders Method. — Add to serum half its volume of a 

 saturated solution of ammonium sulphate (i.e., half saturate it) = 

 precipitate of the globulin. Complete saturation precipitates the 

 albumin as well 



Only methods (c) and (d) are now used. Kauder's method enables 

 one rapidly to separate the globulin and then the albumin by the 

 use of one salt. 



(^.) Allow a few drops of serum to fall into a large quantity of 

 water, and observe the milky precipitate due to the presence of a 

 globulin = serum-gloiHilin. This is best observed by placing a dead 

 black surface behind the vessel of water. "We can then trace the 

 *' milky way " of the falling drops of serum as they traverse the 

 water. 



(B.) Serum-Albumin. — From (A.), (c), filter ofl' the precipitate, 

 and test the filtrate for the usual proteid reactions. It is evident 

 that the filtrate still contains a proteid, which is serum-albumin 

 (Lesson 1. 5, 2). To the filtrate add sodic sulphate, when serum- 



