184 



Dr. J. O. W. Barratt. The Nature of the 



a small amount of thrombin or else of serozyme-ferment is also introduced 

 or set free at the time of injection, leading to the intravascular separation of 

 fibrin in relatively insignificant quantity. 



It is obvious that the above method of injection into the circulating blood 

 plasma will enable a liquid, which has been shown by tests in vitro to 

 contain thrombin, to be distinguished from a second liquid which has 

 similarly been shown to contain thrombokinase. The plasma contained in 

 circulating blood is, moreover, the only liquid to which the designation " fluid 

 plasma " or " stable plasma " can with propriety be applied. Up to the 

 present no " fluid plasma " has been prepared which is not recognisably 

 different from circulating blood plasma. 



Effect of Heat upon Thrombin and Thrombokinase. 



Method. — A solution of fibrinogen was obtained as follows from plasma 

 prepared by Freund's method.* The internal carotid artery of a rabbit was 

 exposed and ligatured in its upper part, a spring forceps being applied to the 

 lower part of the vessel, which was then opened below the ligature and 

 thoroughly washed out with 085-per-cent. solution of sodium chloride by 

 means of a paraffined capillary pipette, after which a paraffined cannula was 

 introduced. By releasing the forceps blood was allowed to flow from the 

 cannula into a paraffined tube, which was then centrifugalised until the red 

 cells were precipitated. The supernatant liquid plasma was next removed 

 with a paraffined pipette and mixed with 20 volumes of distilled water 

 through which a stream of C0 2 had been passed. The fibrinogen, which was 

 thereby precipitated from solution, was collected by centrifugalisation and 

 dissolved in 85-per-cent. solution of sodium chloride, the volume of the 

 liquid thus obtained being made equal to that of the plasma employed. 



A solution of thrombin was prepared by adding to 10 c.c. of solution of 

 fibrinogen 0'9 c.c. of a 0-6-per-cent. solution of calcium chloride, together 

 with such an amount of a suspension of stromata of the red cells of the 

 rabbitf (usually about 2"5 c.c.) as would produce a coagulum at the end of 

 15 minutes at 37° C. From this coagulum about 13 c.c. of fluid (= thrombin 

 solution) was expressed with a glass rod at the end of two hours. 



Thrombin is destroyed by exposure to a temperature of 55° C. for 

 30 minutes, or to a temperature of 60° C. for about five minutes. This effect 

 of heating is illustrated below : — 



* E. Freund, " Ein Beitrag zur Kenntniss der Blutgerinnung," ' "Wien med. JakrbUcher, 

 1886, p. 46 ; " Uber die Ursache der Blutgerinnung," ibid., 1888, p. 260. 

 t Prepared as described in the preceding section, p. 180. 



