THE COAGULATION OF THE BLOOD 225 



tion, because the peptone tends to cause a certain degree of vascular 

 depression. The respiratory movements are quickened and the blood- 

 pressure frequently drops to a very low level. 



It is believed that this action of peptone is made possible by the 

 liberation or formation of a substance which hinders coagulation, the 

 so-called antithrombin.^ As the latter is not a constituent of the 

 peptone, it must be formed subsequent to its injection. Nolf^ and 

 others believe that it is produced in the liver, because the exclusion 

 of this organ from the circulation destroys the aforesaid action of the 

 peptone. Moreover, Delezenne^ has succeeded in producing an anti- 

 coagulating agent by perfusing the excised liver with a peptone solu- 

 tion. It seems that this antibody is enabled to unfold its character- 

 istic action by neutralizing a certain quantity of the fibrin ferment. 

 It is also of interest to note that the peptone gives rise to a certain 

 degree of resistance or immunity, because if a second injection is made 

 a day later, it fails as a rule to render the blood non-coagulable. Ex- 

 tracts of crayfish or of mussels act in a somewhat similar manner. 



Leech Extract and Snake Poisons. — A substance possessing a 

 marked inhibitor power upon coagulation has been obtained by Hay- 

 craft^ from leeches. In its pure crystalline form it is known as hirudin. 

 Although relatively resistant to high temperatures, its effectiveness 

 may be materially lessened by heating it to 100° C. It behaves in 

 general like a secondary albumose. When injected intravenously^ 

 or when mixed with fresh blood after its renioval from the body, 

 it produces a rather lasting non-coagulability. Its action is said to 

 depend upon the production of an antibody which, in accordance with 

 the statements of Moravitz, regulates the formation of thrombin with 

 quantitative precision. Pekelharing, on the other hand, has expressed 

 the opinion that it prevents the liberation of those bodies upon which 

 the production of the fibrin ferment depends. The latter view has 

 recently been advocated by Biirker who emphasizes the fact that 

 solutions of hirudin act preservatively upon the blood platelets. 



Substances possessing a similar action have been found in ixodes 

 ricinus^ and in ankhylostomum caninum.'^ In this connection atten- 

 tion should also be called to the biological peculiarity that the venoms 

 of snakes may act either acceleratory or inhibitory. The poison of 



1 Fuld and Spiro, Hofmeister's Beitrage, v, 1904, or Moravitz, Archiv fiir 

 klin. Med., Ixxix, 1903-4. 



2 Arch, intern, de phys., ii, 1904-5. 



3 Arch, de phys., viii, 1896, 655. 



* Arch. f. Exp. Path. u. Pharm., xviii, 1884, 209. It has been isolated by 

 Franz (Archiv f. Exp. Path. u. Pharm., xlix). The leeches are dried, pulverized 

 and extracted with normal saline solution. It suffices, however, to use only the 

 head portions of these animals, because the active substance is contained in the 

 buccal glands. 



^ Use 10 to 20 eg. for 10 kg. of body weight in 10 to 20 c.c. of saline solution, and 

 1 eg. for each additional kilo of weight. 



^ Sebatani, Arch, ital, de biol., xxxi, 1899, 375. 



'' Loeb and Smith, C. Bact., xxxvii, 1904, 37. 



15 



