CHEMICAL COMPOSITION OF BLOOD-PLASMA. 451 



its temperature of heat coagulation is much lower (56 to 60 C.), 

 and it is completely thrown down from its solutions by saturation 

 with sodium chlorid as well as with magnesium sulphate. Its most 

 important and distinctive reaction is, however, that under proper 

 conditions it gives rise to an insoluble protein, fibrin, whose forma- 

 tion is the essential phenomenon in the coagulation of blood. 

 Fibrinogen has a percentage composition, according to Hammar- 

 sten, of: C, 52.93; H, 6.90; N, 16.66; S,1.25; O, 22.26; while its 

 molecular composition, according to Schmiedeberg, is indicated by 

 the formula C 108 H 162 N 30 SO 34 . 



Fibrinogen is found in blood-plasma, lymph, and in some cases, 

 though not always, in the normal and pathological exudations. It 

 is absent from blood-serum, being used up during the process of 

 clotting. It occurs in very small quantities in blood, compared 

 with the other proteins. Estimates of the amount of fibrin, which 

 cannot differ very much from the fibrinogen, show that in human 

 blood it varies from 0.22 to 0.4 per cent.; in horse's blood it may 

 be more abundant, 0.65 per cent. There is some evidence to 

 indicate that the fibrinogen is produced in the liver, or at any rate 

 that this organ is concerned in some way in its production. Thus 

 it is stated that extirpation of the liver in the dog, after establishing 

 an Eck fistula, is followed by a rapid disappearance of the fibrino- 

 gen of the blood.* In phosphorus poisoning, and particularly in 

 chloroform poisoning, which is attended by an extensive necrosis 

 of the central portions of the liver lobules, the amount of fibrinogen 

 in the blood is rapidly reduced, f and simultaneously, as we should 

 expect, the blood loses more or less completely its power of clotting. 

 Finally it has been noted that if the blood of a dog is withdrawn 

 in separate portions, defibrinated and reinjected into the circula- 

 tion, the missing fibrinogen is quickly regenerated in a normal 

 animal, while in one with its liver thrown out of function this re- 

 generation does not take placet 



The following table gives some results of analyses of blood 

 which indicate the average amounts of the different proteins 

 in the blood-plasma of several animals. The figures give the weight 

 of the protein in grams for 100 c.c. of plasma. 



SERUM- 

 TOTAL PROTEINS. ALBUMIN. PARAGLOBULIN. FIBRINOGEN. 



Man 7.26 4.01 2.83 0.42 



Dog 6.03 3.17 2.26 0.60 



Sheep 7.29 3.83 3.00 0.46 



Horse 8.04 2.80 4.79 0.45 



Pig 8.05 4.42 2.98 0.65 



* See Doyon, "C. r. Soc. Biol.," 56, 612, 1904, and Nolf, "Arch, internal, 

 de physiol.,"3, 1, 1905; "Archivio di Fisiologia," 7, 1909. 



t Whipple, "Journal of Exp. Medicine," 13, 136, 1911, and 15, 246, 1912. 

 j Meek, "American Journal of Physiology," 30 161, 1912. 

 I Lewinski, "Pfliiger's Archiv," 100, 611, 1903. 



