PREVENTION OF COAGULATION. 251 



the blood (in the living dog), it does not coagulate on leaving the veins 

 (FANO, ScHMiDT-MtiLHEiM 1 ). The plasma obtained from such blood 

 by means of centrifugal force is called peptone-plasma. According to 

 ARTHUS and HTJBER 2 the caseoses and gelatoses act like fibrin proteosc 

 in dogs. Eel serum and certain lymph-forming extracts of organs 

 (see Chapter VI) have an analogous action. The coagulation of the 

 blood of warm-blooded animals is prevented by the injection of an 

 effusion of the mouth of the officinal leech or a solution of the active 

 substance of such an infusion, hirudin (FRANZ), into the blood current 

 (HAYCRAFT 3 ). If the blood is allowed to flow directly, while stirring 

 it, into a neutral salt solution best a saturated magnesium-sulphate 

 solution (1 vol. salt solution and 3 vols. blood) we obtain a mixture 

 of blood and salt which remains uncoagulated for several days. The 

 blood-corpuscles, which, because of their adhesiveness and elasticity, 

 would otherwise easily pass through the pores of the filter-paper, are 

 made solid and stiff by the salt, so that they may be easily filtered 

 off. The plasma thus obtained, which does not coagulate spontaneously, 

 is called salt-plasma. 



An especially good method of preventing coagulation of blood con- 

 sists in drawing the blood into a dilute solution of potassium oxalate, 

 so that the mixture contains 0.1 per cent oxalate (ARTHUS and PAGES 4 ). 

 The soluble calcium salts of the blood are precipitated by the oxalate, 

 and hence the blood loses its coagulability. On the other hand, HORNE 5 

 found that chlorides of calcium, barium, and strontium, when present 

 in large amounts (2-3 per cent), may prevent coagulation for several 

 days. According to ARTHUS 6 a non-coagulable blood-plasma may be 

 obtained by drawing the blood into a sodium-fluoride solution until it 

 contains 0.3 per cent NaFl. 



On coagulation there separates in the previously fluid blood an insoluble 

 or a very difficultly soluble protein substance, fibrin. When this separa- 

 tion takes place without stirring, the blood coagulates in a solid mass, 

 which, when carefully severed from the sides of the vessel, contracts, 

 and a clear, generally yellow-colored liquid, the blood-serum, exudes. 

 The solid coagulum which encloses the blood-corpuscles is called the 

 blood-clot (placenta sanguinis). If the blood is beaten during coagula- 

 tion, the fibrin separates in elastic threads or fibrous masses, and the 



J Fano, Arch f.. (anat. u.) Physiol., 1881; Schmidt-Mulheim, ibid., 1880. 



2 Arch, de Physiol. (5), 8. 



3 Haycraft, Proc. Physiol. Soc., 1884, 13, and Arch. f. exp. Path. u. Pharm., 18; 

 Franz, Arch. f. exp. Path. u. Pharm., 49. 



4 Archives de Physiol. (5), 2, and Compt. Rend., 112. 

 6 Journ. of Physiol., 19. 



6 Journ. de Physiol. et Path., 3 and 4. 



