CHEMICAL COMPOSITION OF PLASMA. 217 



each of these fluids a substance can be precipitated by passing a 

 stream of carbon dioxide (CO 2 ) through the fluids. Both pre- 

 cipitates readily re-dissolve in weak saline solutions. 



The solution prepared from the hydrocele fluid causes blood 

 serum to coagulate ; that prepared from the blood serum causes 

 the hydrocele fluid to coagulate; and when mixed together the 

 mixture of the two solutions coagulates; while the serum and 

 hydrocele fluid from which the substances have been removed no 

 longer have the power of exciting coagulation in each other or 

 in like fluids. Here, then, are brought to light two materials: 

 one, which may be obtained in considerable quantity from serum 

 after coagulation, is called serum-globulin or paraglobulin, the 

 other occurring in serous fluids is named fibrinogen. Both of 

 these substances are present in the dying plasma of the blood 

 prior to coagulation. They can be obtained both together 

 from the plasma (when either of the precautions already men- 

 tioned, viz., the application of cold, or the addition of neutral 

 salt, has been taken to prevent the formation of fibrin) if the 

 plasma be treated with sodium chloride to saturation. This pre- 

 cipitates a substance which readily dissolves if water be added to 

 weaken the salt solution, and after some time the solution under- 

 goes spontaneous coagulation, while the plasma from which it has 

 been made has last that power. This plasmin (Denis) no doubt 

 is made of different globulins, chiefly serum-globulin and fibrin- 

 ogen, and contains in itself all the necessary " factors " of fibrin 

 formation, but is not at all identical with fibrin, since it readily 

 dissolves in weak saline solutions, like the class of proteids called 

 globulins, while fibrin is quite insoluble in such solutions. 



In plasma removed from its normal relationships, then, both 

 serum-'globulin and fibrinogeu exist; but the former in far greater 

 quantity than the latter, since the serum, after the blood-clot is 

 formed, contains no more fibrinogen, while the serum-globulin or 

 paraglobulin makes up nearly half the entire solids of the remain- 

 ing serum. 



In preparing fibrinogen and paraglobulin (or, as he called the 

 latter, fibrinoplastin) Schmidt found that the more carefully they 

 were made, the weaker and more uncertain their action as fibrin 



