PREVENTION OF COAGULATION. 243 



The coagulation of the blood may be prevented in other ways. After 

 the injection of pep tore, or, more correctly, proteose, solutions into 

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

 veins (FANO, SCHMIDT-MULHEIM J ). The plasma obtained from such 

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

 to ARTHUS and HuBER 2 the caseoses and gelatoses act like fibrin 

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

 organs (see Chapter VII) 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 



1 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. 



5 Journ. of Physiol., 19. 



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



