BLOOD. 487 



ulation of the same amount of fibrinogen if fibrinoplastin were present. 

 It would, therefore, appear that the fibrinoplastin in some way assists in 

 converting the soluble fibrinogen into the insoluble fibrin, without itself 

 directly taking part in the formation of the latter. This view is sup- 

 ported by the fact that while blood-serum is entirely free from fibrin- 

 ogen it contains nearly as much fibrinoplastin as uncotigulated blood. 



Fibrinoplastin perhaps acts in the same way as certain salts (NaCl, 

 CaC] 2 ) and lecithin, which, when added in very small amounts to coag- 

 ulable fluids, appear to increase the amount of fibrin formed. 



The above-mentioned fibrin factors do not exist read3 r formed in 

 the circulating blood of living animals, but originate in the breaking 

 down of the white blood-cells in man and other mammals, and of the red 

 nucleated blood-cells of birds and amphibia. As to how far the hsemato- 

 blasts are concerned in this process is still the subject of controversy ; 

 it is, however, absolutely certain that immense numbers of the white 

 blood-corpuscles disappear during coagulation. 



Fibrinogen belongs to the group of globulins, i.e., albuminous bodies which 

 are insoluble in water, but soluble in dilute saline solutions, in which again they 

 are rendered insoluble through the action of acids and alkalies. 



Fibrinogen may be prepared by collecting horses' blood in one-fourth its 

 volume of a saturated solution of magnesium sulphate, stirring and filtering, 

 separating the corpuscles from the plasma by the use of the centrifugal machine, 

 and adding to the latter an equal volume of a saturated salt solution. The pre- 

 cipitate is then collected, dried by pressing between layers of filter-paper, dis- 

 solved in an 8 per cent, salt solution, again precipitated with an equal volume of 

 saturated salt solution, again drying and dissolving, and repeating the process until 

 a precipitate is obtained, which, after drying with filter-paper, still retains enough 

 salt adhering to it to render it soluble in distilled water, and which should con- 

 tain no trace of serum-albumen or paraglobulin. The removal of the paraglobu- 

 lin depends upon the fact that fibrinogen is very much more readily precipitated 

 by 15-20 per cent, salt solution than is paraglobulin. So obtained, fibrinogen, in 

 1-5 per cent, salt solution, coagulates at 52°-55° C. It also may be obtained, 

 mixed with fibrinoplastin, from hydrocele or pericardial fluid, by dilution with 

 10-15 volumes of water, or by the passage of a stream of C0 2 . 



The fibrinoplastic substance, or paraglobulin, is obtained as a white precipi- 

 tate when perfectly clear and colorless blood-serum is faintly acidulated with 

 acetic acid, and then diluted with fifteen or twenty times its volume of distilled 

 water. The precipitate is then collected on a filter and washed with distilled 

 water. Out of 100 c.c. ox-serum 0.7-0.9 gramme paraglobulin maybe obtained 

 by this process, though it is almost impossible to free it entirely from fibrin 

 ferment. 



The freshly precipitated paraglobulin is perfectly white, is insoluble in water, 

 but is soluble in dilute solutions of sodium bicarbonate, sodium phosphate, sodium 

 chloride, and other neutral salts of the alkalies. These solutions coagulate on 

 heating like ordinary albumen (between 60° and 80° C), and when diluted with 

 distilled water again precipitate the paraglobulin. 



If paraglobulin is added to certain serous fluids, such as hydrocele fluid, peri- 

 cardial fluid, and serous effusions, coagulation is instantly produced through the 

 action of the fibrin ferment, which always contaminates it. 



There is less paraglobulin in horses' blood than in oxen's blood — 0.3 to 0.5 

 per cent, in the serum of the former to 0.7 to 0.8 per cent, in the latter. 



Paraglobulin, as well as fibrinogen, originates in the breaking down of 

 white blood-corpuscles. 



The fibrin ferment has never been obtained pure. Its aqueous solutions may 

 be prepared by adding 15-20 volumes of absolute alcohol to the pure serum of 



