28 PROTEIDS. 



4. Fibrinogen 1 . 



This globulin occurs in blood-plasma together with paraglobulin 

 and serum-albumin. During blood-clotting it is converted largely, if 

 not entirely into fibrin (but see below). It is also found in chyle, 

 serous fluids and transudations, more particularly in hydrocele fluids 2 . 



In its general reactions it resembles paraglobulin but is markedly 

 distinguished from the latter by the following characteristics. (1) As 

 it occurs in plasma 3 or in dilute solutions of sodium chloride (1 5 p.c.), 

 it coagulates at 55 56. (2) It is very readily precipitated by the 

 addition of sodium chloride to its saline solutions until the whole 

 contains 16 p.c. NaCl, whereas paraglobulin is not appreciably pre- 

 cipitated until at least 20 p.c. of the sodium salt has been added. 



Preparation 4 '. Salted plasma, obtained by centrifugalising blood 

 whose coagulation is prevented by the addition of a certain proportion 

 of magnesium sulphate, is mixed with an equal volume of a saturated 

 (35-87 p.c. at 14 C.) 5 solution of sodium chloride; the fibrinogen is thus 

 precipitated while the paraglobulin remains in solution. The adhering 

 plasma may be removed by washing with a solution of sodium chloride, 

 and the fibrinogen finally purified by being several times dissolved in 

 and reprecipitated by sodium chloride. 



Hammarsten's statements as to the nature and properties of fibrinogen have been 

 the subject of much controversy between himself, Al. Schmidt and Wooldridge. 



When a fluid containing purified fibrinogen is made to yield fibrin 

 by the action of fibrin-ferment, the amount of fibrin formed is always 

 less than that of the fibrinogen which disappears at the same time 6 . 

 The deficit thus observed is at least partly accounted for by the 

 simultaneous appearance of a globulin which coagulates, when heated 

 in saline solution, at 64. Although at first sight it seems very 

 tempting to regard the process of fibrin-formation from fibrinogen as 

 partaking of the nature of a hydrolytic fZ) cleavage of which this 



1 Hammarsten, Nov. Act. Reg. Soc. Sci., Upsala, Vol. x. 1, 1875. Maly's Bericht. 

 vi. (1876), S. 15. Pfluger's Arch. Bd. xiv. (1877), S. 211; xix. (1879), S. 563; xxn. 

 (1880), S. 431; xxx. (1883), S. 437. Maly's Bericht. xn. (1882), S. 11. Al. Schmidt, 

 Pfliiger's Arch. Bd. vi. (1872), S. 413; xi. (1875), S. 291; xm. (1876), S. 146. 

 "Lehre von den ferment. Gerinnungserscheinungen u. s. w.," Dorpat, 1877. 

 Wooldridge, Jl. of Physiol. Vol. iv. (1883), pp. 226, 367. Arch. f. Physiol. 1883, S. 

 389; 1884, S. 313; 1886, S. 397. Proc. Roy. Soc. Vol. LXII. (1887), p. 230. 

 Ludwig's Festschrift, 1887, S. 221. Zt. f. Biol. Bd. xxiv. 1888, S. 562. Arch. f. 

 Physiol. 1888, S. 174. Jl. Physiol. Vol. x. (1889), p. 329. 



2 Hammarsten, Maly vm. (1878), S. 347. 



3 Fredericq, Ann. Soc. de Med. Gand, 1877. Arch. d. Zool. Exp., 1877, No. 1. 

 Bull, de VAcad. roy. de Belgique, T. LXIV. (1877), No. 7. "Becherches sur la con- 

 stitution du plasma sanguin." Paris, 1878. 



4 Hammarsten, loc. cit. passim. Gamgee, Physiol. Chem. Vol. I. p. 41. 



5 Poggiale, Ann. Chim. Phys. (3), Vol. vm. p. 469. 



6 Hammarsten, Pfluger's Arch. Bd. xxx. (1883), Sn. 459, 465, 475. 



