480 PEACTICAL PHYSIOLOGY 



8-25 grammes carbon; so that 30-8-25 = 21-75 grammes carbon 

 represents 21-75x1-3 = 28-3 grammes fat. On this diet, therefore, 

 the subject retains in his tissues 15-6 gr. proteid and 28*3 gr. fat 

 per diem. 



To express this result in terms of energy liberated, we know that 

 3027-5 C. were supplied and that all these have been used except 

 15-6x4-1 = 64 retained as proteid, and 28-3x9-3 = 263-2 retained as 

 fat ; or in toto 327-2 C. We find, therefore, that 3027-5 - 327*2 = 2,700 

 C. have been required. 



CHAPTER XV. 



FIBKJNOGEN. FIBRIN FERMENT. AMMONIA AND SUGAR 

 IN BLOOD. 



Preparation of Fibrinogen. Blood plasma obtained by any of the 

 methods detailed on page 190 except the natural salt method, is 

 thoroughly mixed with an exactly equal amount of a cold saturated 

 solution of sodium chloride. By this means, half saturation with 

 sodium chloride is obtained in the mixture and in this the fibrinogen is 

 precipitated, whereas the other globulins remain in solution. The 

 precipitate is collected on a folded filter (see p. 491), washed quickly 

 with a half-saturated solution of sodium chloride and redissolved by 

 adding water to it. The salt adhering to the precipitate forms with 

 the water added to the latter, a weak saline solution and in this the 

 fibrinogen dissolves. This process of purification may be repeated 

 several times, but the operations must be very quickly carried out as, 

 otherwise, the precipitate of fibrinogen becomes insoluble in a. weak 

 saline solution (Hammarsten's method). 



Preparation of Fibrin Ferment. Blood serum or some defibrinated 

 blood is mixed with twenty times its bulk of alcohol. A copious white 

 precipitate of all the proteids is thereby obtained. This precipitate 

 is allowed to stand under the alcohol for two months. After this 

 time all the precipitated proteids except fibrin ferment become 

 coagulated so that they are no longer soluble in their original solvents. 

 The fluid is then pipetted off and the sediment collected on a 

 filter, and, after the spirit has drained off, ground up in a mortar 

 with water. The resulting extract is filtered and contains the fibrin 

 ferment. 



