THEORIES OF COAGULATION. 169 



globulin does not take part in forming fibrin. By precipitating fibiin- 

 ogen by half-saturating plasma with sodium chloride, he obtained it 

 free from serum globulin, and found that its solution in dilute salt 

 solution was coagulated by the addition of Schmidt's extract the so- 

 called fibrin ferment alone. Hammarsten proved that coagulation 

 consists in a conversion of fibrinogen into fibrin ; the change being 

 accompanied by a splitting of the fibrinogen, and not by a combination 

 of it with the serum globulin, as was supposed by Schmidt. 



Influence of lime salts. Theories of Freund and of Arthus and Pages. 

 The more recent researches since these of Hammarsten have been 

 in the direction of elucidating the true nature of the substances 

 contained in Schmidt's extract. Green l found the extract to contain 

 sulphate of lime, and that if lime were removed from plasma by 

 dialysis its coagulability became lost, but was restored by the addition 

 of sulphate of lime. Einger and Sainsbury 2 showed that other salts of 

 lime, such as calcium chloride, might replace the sulphate, and that the 

 calcium might be replaced by barium and by strontium, although the 

 salts of these metals are not so efficacious as the corresponding salts 

 of calcium. 



Freund 3 also drew special attention to the important part played by 

 lime salts in promoting the formation of fibrin. He supposed the 

 original cause of the deposition of fibrin in fibrinogenous liquids to be 

 the formation of insoluble tribasic phosphate of lime, by the interaction 

 of soluble phosphates (which he supposed to be shed out from the 

 corpuscles whenever they come in contact with and adhere to foreign 

 surfaces) with soluble lime salts contained in the plasma; the lime 

 phosphate combining at the moment of formation with fibrinogen, and 

 forming fibrin, and no other agency in the shape of a special ferment 

 being necessary. This inference has not, however, been confirmed by 

 subsequent observers. Freund supposed neutral salts, peptone, etc., to 

 act in preventing coagulation, by keeping phosphate of lime in solution, 

 and the walls of the blood vessels to act in preventing coagulation 

 because the corpuscles do not adhere to them. Freund based his theory, 

 partly upon the fact that if blood is drawn from an artery through a 

 tube smeared with oil or vaseline into a vessel similarly prepared, the 

 blood remains fluid for a long time, presumably because the adhesion of 

 the corpuscles to the walls does not occur. Similar experiments with 

 blood kept surrounded by paraffin or oil were performed by Hay craft 

 with like result. 4 



Arthus and Pages 5 mixed blood as it flowed from the vessels with a 

 small quantity of a soluble oxalate 6 (O'07-O'l parts per 100 of blood) 

 sufficient to precipitate the lime salts dissolved in the plasma. They 

 found that blood thus treated did not coagulate, however long it might 

 be kept, 7 but that coagulability of its plasma is immediately restored on 

 again adding a soluble lime salt, such as calcium chloride. They 



1 Journ. Physiol., Cambridge and London, 1887, vol. viii. p. 354. 



2 Ibid., 1890, vol. xi. p. 369. 3 Mcd. Jahrb., Wein, 1888, S. 259. 



4 Journ. Anat. and Physiol., London, 1888, p. 172 ; Haycraft and Carlier, ibid., p. 582. 



5 Arch, dephysiol. norm, et path., Paris, 1890, p. 739 ; Arthus, These de Paris, 1892. 



6 Solutions of soap (0'5 parts per 100 of blood) or of soluble fluorides (0'2 parts per ]00 

 of blood) act similarly to those of oxalate. 



7 Hammarsten makes a similar statement for horse's blood, but it is certainly not 

 correct for all kinds of blood. Oxalate plasma, obtained from dog's or sheep's blood, does 

 undergo coagulation on standing ; coagulability is therefore not abolished by precipita- 

 tion of the lime by oxalate, but merely deferred. We shall return to this point immediately. 



