24 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



trate from the coagulum again coagulates at about 65, and 

 the filtrate from this at about 75. 



2. Residue. Preparation of Myosin. The meat residue 

 is again extracted in the same manner with water, the water 

 poured off, and then the residue stirred into a thin paste with 

 a 15 per cent, solution of ammonium chloride, and after 

 twenty-four hours filtered. The solution contains myosin. 



(a) A part of the solution is poured into a test-tube two- 

 thirds full of water. Separation of myosin in a swollen con- 

 dition. 



(6) A part of the solution is poured upon a piece of salt 

 in a small beaker. The surface of the salt becomes covered 

 with the precipitated myosin. Instead of this we may also 

 cause the separation of the myosin by introducing finely pul- 

 verized salt into the solution and stirring. 



(c) A portion of the solution is heated to boiling and fil- 

 tered. The filtrate contains calcium salts, as may be shown 

 by the addition of ammonium oxalate. 



Myosin is therefore characterized by its insolubility in 

 water and strong solutions of salts, solubility in salt solutions 

 of medium concentration, and by the fact that it contains 

 calcium, which it gives up on coagulation. 



III. PREPARATION OF THE XANTHINE BASES, ALLOXURIC 



BASES. 



METHOD A. 



Dissolve 50 g. of meat extract in 500 cc. of water in a 

 flask and, after the addition of 75 to 100 cc. of nitric acid 

 (1.2 sp. gr.) to destroy substances which hinder the precipi- 

 tation of the xanthine bases by silver nitrate heat on the 

 sand-bath until the solution has cleared up which will require 

 about three-quarters of an hour. After cooling make strongly 

 alkaline with ammonia, filter from the phosphates which 



