COAGULATION OF THE BLOOD. 305 



is there converted into thrombin by the calcium salts. The observation 

 that uncoagulated leech-plasma does not coagulate on the addition of 

 calcium salts, while it does coagulate on the addition of prothrombin 

 solutions, seems to support this view; still it is not quite conclusive. 

 Leech-extract contains a body, hirudin, which, according to MORAWITZ, 

 is an antibody toward thrombin and quantitatively neutralizes it. On 

 the addition of prothrombin, new thrombin may be formed, which may 

 act if the hirudin is not present in too great an excess. 



The behavior of sodium -fluoride plasma shows more conclusively 

 the absence of prothrombin in the circulating plasma. Such plasma, 

 according to ARTHUS, contains no prothrombin, a statement which has 

 been partly substantiated by MORAWITZ, who finds that fluoride-plasma 

 contains more or less prothrombin, dependent upon the greater or less 

 change the blood undergoes before it flows into the sodium-fluoride 

 solution. One can obtain, according to MORAWITZ, at least sometimes, 

 a fluoride-plasma which contains no prothrombin. The observations 

 of FULD and of SCHITTENHELM and BODONG contradict the statement 

 that fluoride-plasma contains prothrombin. As BORDET and GENGOU 1 

 have shown that prothrombin can be carried down by the precipitate 

 produced in fluoride-plasma, it seems as if the observations of ARTHUS 

 and MORAWITZ on this point are not conclusive, and MORAWITZ is now 

 also of the opinion that the prothrombin occurs preformed in the 

 plasma. NoLF 2 also holds this view, ana for the present we generally 

 believe that prothrombin, or as it is also now designated thrombogen 

 {MORAWITZ, NOLF), is a preformed constituent of the plasma. The 

 absence of prothrombin, as observed by ARTHUS, in peritoneal transu- 

 dates in the horse, can hardly be considered as sufficient evidence as to 

 the non-occurrence of this body in blood-plasma. 



Although the opinions are rather united as to the occurrence of at least 

 three bodies, fibrinogen, prothrombin (thrombogen) and lime salts in the 

 plasma, still the question arises how the thrombin is formed from the 

 thrombogen. The zymoplastic substances must be here considered, 

 and the starting-point in these new investigations is the accelerating 

 action upon coagulation, of different tissue extracts, an action which has 

 been known for a long time and was especially studied by DELEZENNE 

 on the plasma from bird's blood. Unfortunately we. are not in accord 



1 Arthus, Journ. de Physiol. et Pathol., 3 and 4, and Compt. rend. soc. biol., 56. 

 The works of Morawitz may be found in Hofmejster's Beitrage, 4 and 5, Deutsch. 

 Arch. f. klin. Med., 79 and 80, and in Oppenheimer's Handb der Bioch., 2; Fuld, 

 Centralbl, f. Physiol., 17, p. 529; with Spiro, Hofmeister's Beitrage, 5; Schittenhelm 

 and Bodong, Arch. f. exp. Path. u. Pharm., 54; Bordet and Gengou, Annal. Institut 

 Pasteur, 18. For more recent literature see Loeb, Biochem. Centralbl., 6, p. 907. 



2 Arch, internat. de Physiol., 6, 1908. 



