34 THE FIBRIN-FACTOKS. 



[A. Schmidt's Researches (1861). This observer rediscovered the chief facts already known 

 to Buchanan, viz., that some fluids which do not coagulate spontaneously, clot when mixed 

 with other fluids which show no tendency to coagulate spontaneously, e.g., hydrocele fluid and 

 blood-serum. He isolated from these fluids the bodies described us fibrinogen and fibrino- 

 plaslin. The bodies so obtained were not pure, but Schmidt supposed that the formation of. 

 fibrin was due to the interaction of these two proteids. The reason hydrocele fluid does not 

 coagulafe, he says, is that it contains fibrinogen and no fibrino-plastin, while blood-serum con- 

 tains the latter, but not the former. Schmidt afterwards discovered that these two substances 

 may be present in a fluid, and yet coagulation may not occur {e.g., occasionally in hydrocele 

 fluid). He supposed, therefore, that blood or blood-serum contained some other constituent 

 necessary for coagulation. This he afterwards isolated in an impure condition and called 

 fibrin-ferment. ] 



A. Schmidt's theory is that fibrin is formed by the coming together of toft 

 protcid substances which occur dissolved in the plasma, viz.: (1) fibrinoger, 

 >., the substance which yields the chief mass of the fibrin, and (2) fibrino-plastic 

 substance or fibrino-plastin (serum-globulin or paraglobulin, 32). In order to 

 determine the coagulation a ferment seems to be necessary, and this is supplied by 

 (3) the fibrin-ferment. 



1. Properties. Fibrinogen and fibrino-plastin belong to the group of proteids 

 called globulins, i.e., they are insoluble in pure water, but are soluble in dilute 

 solutions of common salt ( 249), and are not distinguished from each other by well- 

 marked chemical characters. Still they differ as follows : 



Fibrino-plastin is more easily precipitated from its solutions than fibrinogen. 

 It is more readily redissolved when once it is precipitated. It forms when pre- 

 cipitated a very light granular powder. 



Fibrinogen adheres as a sticky deposit to the side of the vessel. It coagulates 

 at 56 J C. 



On account of their great similarity, both substances are not usually prepared 

 from blood-plasma. FUMnoyen is prepared from serous transudations (pericardial, 

 abdominal, or pleuritic fluid, or the fluid of hydrocele), which contain no fibrino- 

 plastin. Fibrino-plastin is most readily prepared from serum, in which there is still 

 plenty of fibrino-plastin, but no fibrinogen. 



2. Preparation of Fibrino-plastin, Serum-globulin, or Paraglobulin. (a) 

 Dilute blood-serum with twelve times its volume of ice-cold water, and almost 

 neutralise it with acetic acid [add 4 drops of a 25 per cent, solution of acetic acid 

 to every 120 c.c. of diluted serum] ; or (b) pass a stream of carbon dioxide through 

 the diluted serum, which soon becomes turbid ; after a time a fine white powder, 

 copious and granular, is precipitated. 



[(c) Method of Hammarsten. All the fibrino-plastin in serum is not precipitated 

 either by adding acetic acid or by C0 2 . Hammarsten found, however, that if 

 crystals of magnesium sulphate be added to complete saturation, it precipitates the 

 whole of the serum-globulin, but does not precipitate serum-albumin; serum-globulin 

 is more abundant than serum-albumin in the serum of the ox and horse, while 

 in man and the rabbit the reverse obtains ; (compare 32).] 



Schmidt found that 100 c.c. of the serum of ox blood yielded 07 to 0*8 grm. ; horse's 

 serum, 03 to 0*56 grin, of dry fibrino-plastin. Fibrino-plastin occurs not only in seruni, but 

 also in red blood-corpuscles, in the fluids of connective-tissue, and in the juices of the cornea. 



3. Preparation of Fibrinogen. This is best prepared from hydrocele fluid, 

 although it may also be obtained from the fluids of serous cavities, e.g., the pleura, 

 pericardium, or peritoneum. It does not exist in blood-serum, although it does 

 exist in blood-plasma, lymph, and chyle, from which it may be obtained by a 

 stream of CO. after the paraglobulin is precipitated, (a) Dilute hydrocele fluid 

 with ten to fifteen times its volume of water, and pass a stream of C0 2 through it 

 for a long time. (6) Add powdered common salt to saturation to a serous trans- 

 udation, when a sticky glutinous (not very abundant) precipitate of fibrinogen is 

 obtained. 



