CHEMICAL COMPOSITION OF BLOOD-PLASMA. 451 



such as pericardial liquid, hydrocele fluid, etc. The amount of 

 serum-albumin in the blood varies in different animals, ranging 

 among the mammalia from 2.67 per cent, in the horse to 4.52 per 

 cent, in man. In some of the cold-blooded animals it occurs in 

 surprisingly small quantities, 0.36 to 0.69 per cent. 



Paraglobulin, which belongs to the group of globulins, exhibits 

 the general reactions characteristic of the group. As stated above, 

 it is completely precipitated from its solutions by saturation with 

 magnesium sulphate or by ^half saturation with ammonium sul- 

 phate. It is incompletely precipitated by saturation with common 

 salt (NaCl). In neutral or feebly acid solutions it coagulates upon 

 heating to 75 C. Hammarsten gives its percentage composition 

 as: C, 52.71; H, 7.01; N, 15.85; S, 1.11; O, 23.32. Schmiedeberg 

 gives it a molecular composition corresponding to the formula 

 C 117 H 182 N 30 SO 38 + iH 2 O. Paraglobulin occurs in blood, in lymph, 

 and in the normal and pathological exudations. The amount of 

 paraglobulin present in blood varies in different animals. Among 

 the mammalia the amount ranges from 1.78 per cent, in rabbits to 

 4.56 per cent, in the horse. In human blood it is given at 3.10 

 per cent., being less in amount, therefore, than the serum-albumin, 

 It is usually stated that more of this protein is found in the serum 

 than in the plasma. This fact is explained by supposing that dur- 

 ing coagulation some of the leucocytes disintegrate and part of 

 their substance passes into solution as a globulin identical with or 

 closely resembling paraglobulin. Paraglobulin as obtained from 

 blood-serum by half saturation with ammonium sulphate or full 

 saturation with magnesium sulphate does not behave like a chem- 

 ical individual. Portions of it, for instance, are precipitated by 

 CO 2 or by dialysis, and portions are not so precipitated. Recently, 

 therefore, it has been assumed that paraglobulin is in reality a 

 mixture of two or possibly three different, although related, pro- 

 teins. The separation usually given is into euglobulin and pseu- 

 doglobulin, euglobulin being the portion precipitated by ammo- 

 nium sulphate when added to one-third saturation (28 to 33 per 

 cent.), and pseudoglobulin the portion precipitated only by one- 

 half saturation (34 to 50 per cent.). The latter portion shows 

 properties more nearly related to the albumins.* The whole basis 

 of classification is, however, unsatisfactory and provisional (see 

 appendix) . 



Fibrinogen is a protein belonging to the globulin class and ex- 

 hibiting all the general reactions of this group. It is distinguished 

 from paraglobulin by a number of special reactions; for example, 



* Forges and Spiro, "Beitrage zur chem. Physiol. u. Pathol.," 3, 277 

 1903; and Freund and Joachim, "Zeitschrift f. physiologische Chemie," 36, 

 407, 1902. 



