378 CHEMISTRY OF THE PROTEIDS CHAP. 



IV. FIBRINOGEN AND FlBRIN 



Fibrinogen 



Fibrinogen, myosin, and casein assume a firm state of aggregation 

 when acted upon by certain ferments. 1 These firm compounds are 

 intermediate between the soluble condition in which the substances 

 may be obtained by the salting-out process and the completely 

 coagulated state into which they pass on becoming denaturalised. 

 When semi-coagulated they are insoluble in water and in salt-solutions, " 

 but converted into completely coagulated, denaturalised compounds 

 by such agencies as heat, alcohol, and formaldehyde. 2 



Eamsden 3 compares coagulated albumins with the mechanical 

 aggregates (see p. 274) which are produced by shaking, and which are 

 also semi-coagulated. Cohnheim is of the opinion that this view is 

 not permissible, because, according to Hammarsten, 4 fibrinogen which 

 has gradually become insoluble differs essentially from fibrin. That 

 Ramsden does not agree to this is shown on p. 382. 



Fibrinogen is contained in the blood plasma of all vertebrates. 

 As soon as the blood leaves the arteries, and under pathological con- 

 ditions even in the blood-vessels, it is changed by the fibrin ferment 

 into fibrin, and to the latter the clotting of blood is due. The fluid 

 portion of the blood before coagulation is called plasma, and after 

 coagulation, when it no longer contains fibrinogen, it is termed serum. 

 The first accurate observations on blood-coagulation were made by 

 Denis 5 and by Alexander Schmidt, 6 who discovered the fibrin ferment. 

 A great step forward was taken when Hammarsten 7 discovered the 

 function of the soluble lime salts during coagulation ; when he taught 

 us how to prepare fibrinogen in a pure state, and when he showed 

 that fibrinogen is the only albumin which is concerned in coagula- 

 tion. After Hammarsten, the part played by the lime salts has been 



1 The most recent papers on blood ferments are by P. Morawitz, Hofmeister's 

 Beitrage, 5. 133 (1904) ; J. Bordet and 0. Gengou, Ann. de VInst. Pasteur, 18. 26 (1904). 



2 A. Benedicenti, Arch.f. (Anat. u.) PhysioL, Physiol. Abteilung, 1897, p. 219. 



3 W. Ramsden, ibid. 1894, p. 517. 



4 0. Hammarsten, Zeitschr. f. physiol. Chem. 22. 333 (1896). 



5 Denis, Memoires sur le sang, Paris, 1859. 



8 Al. Schmidt, Arch. f. (Anat. u.) Physiol. 1861, p. 682 ; E. Samson-Himmelstjerna, 

 Dissert. , Dorpat, 1882 ; Al. Schmidt, Die Lehre von den fermentativen Gerinnungs- 

 vorgdngen, Dorpat, 1876 ; collected papers abstracted in Zur Blutlehre, Leipzig, 1892, 

 and Weitere Beitrage zur Blutlehre, Wiesbaden, 1895. 



7 0. Hammarsten, Untersuchungen uber die Faserstoffgerinnung, Nova acta societ. 

 scientiar. Upsaliensis, ser. iii. vol. x. 1 (1875) ; Pflilger's Arch. f. d. ges. Physiol. 

 14. 211 (1876); 19. 563 (1879); 22.431 (1880); 30.437(1883); Zeitschr. f. 

 physiol. Chem. 22. 333 (1896) ; 28- 98 (1899). 



