486 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



undiluted blood-plasma, in which coagulation has been prevented by cold 

 or a neutral salt, an excess of sodium chloride in bulk be added, a sticky- 

 white precipitate will be formed, and if it is filtered off it will be found 

 that the plasma, even if warmed or diluted with water, has now lost its 

 power of coagulation. If the precipitate collected in the filter be 

 washed with a saturated solution of sodium chloride, in which it is 

 insoluble, and then dissolved in a small amount of distilled water 

 (enough salt will cling to the precipitate to make it a dilute saline 

 solution) and filtered, the clear filtrate will rapidly solidify in the same 

 manner as the blood-plasma prevented by cold from coagulation when 

 gently warmed. This substance is termed plasmine, and it is evident 

 that the coagulation of the blood is due to the conversion of plasmine 

 into fibrin. Plasmine is not, however, a simple body, but a mixture of 

 two proteids, as is shown by the following facts : — 



If sodium chloride in bulk be added to the serum which separated 

 from clotted blood, a precipitate will be formed which in its general 

 characters resembles plasmine, but its solution will not coagulate spon- 

 taneously. This body is termed paraglobulin or fibrinoplastin. 



If sodium chloride be added in bulk to some hydrocele fluid, a 

 similar precipitate will also be formed, which also, when in solution, will 

 not coagulate spontaneously. This substance is termed fibrinogen. If 

 a solution of fibrinogen be added to a solution of paraglobulin, coagula- 

 tion occurs in a manner precisely similar to that observed in blood-plasma 

 or in solutions of plasmine. So, also, the addition of blood-serum to 

 hydrocele fluid will likewise cause coagulation. These facts would seem 

 to indicate that plasmine is a mixture of paraglobulin and fibrinogen. 

 Another factor is, however, also concerned. 



Both paraglobulin and fibrinogen may be precipitated from serum 

 and hydrocele fluid by C0 2 , and yet the solutions of these precipitates 

 when mixed together will not coagulate. 



If some defibrinated blood be poured into about twenty times its 

 volume of strong alcohol, all the proteids will be coagulated. If, after 

 standing some weeks in alcohol, the precipitate be filtered off and ex- 

 tracted with water, a few drops of this solution added to the above mix- 

 ture of paraglobulin and fibrinogen obtained by C0 2 , coagulation will 

 rapidly result. If, however, the watery extract be first boiled, no 

 clotting will result. This points to the presence of a ferment. Conse- 

 quently we say coagulation results from the union of paraglobulin and 

 fibrinogen in the presence of the blood ferment. 



It has, however, been found that fibrin may result from the addition 

 of the fibrin ferment to pure fibrinogen, without in any way requiring 

 the assistance or presence of fibrinoplastin. Nevertheless, the amount 

 of fibrin so formed is considerably less than would result from the coag. 



