COAGULATION OF THE BLOOD. 307 



A serum poor in ferment and having a weak action can be reactivated by the 

 addition of acid or alkali (ALEX. SCHMIDT, MORAWITZ), and in this action, accord- 

 ing to MORAWITZ, a thrombin (/?) is produced which is somewhat different from 

 a-thrombin. The /?-thrombin is produced from a special /?-prothrombin which 

 never occurs in the plasma, but only in the serum. FULD explains this by 

 affirming that the a-thrombin is changed in the serum into metazym (/?-pro- 

 thrombin), which is then transformed by the alkali or acid into neozym ( = /?- 

 thrombin). Nevertheless it is a fact that the quantity of thrombin in the serum 

 diminishes after coagulation and that the thrombin action is considerably increased 

 by the addition of alkali or acid as well as by zymoplastic substances. The above 

 view as to the occurrence of different thrombins has not sufficient basis, and 

 PEKELHARING 1 has also raised objections thereto. 



The theories of MORAWITZ, FULD and SPIRO at least stand in accord 

 with several known facts but do not take sufficient account of the action 

 of the zymoplastic substances of ALEX. SCHMIDT. Thrombokinase is 

 precipitated by alcohol and is not thermostabile, while the zymoplastic 

 substances, of SCHMIDT are thermostabile and soluble in alcohol. The 

 thrombokinase cannot therefore be identical with these zymoplastic 

 substances, and hence this theory does not explain the action of these 

 latter. Further, the mode of action of tissue extracts is unexplained, 

 and is a much disputed subject. It can be said that these two views are 

 in the main opposed to each other. According to one (ALEX. SCHMIDT, 

 ARTHUS, MORAWITZ and others) they do not act like fibrin ferment, but 

 have an indirect action. According to the other (PEKELHARING, Huis- 

 KAMP, DELEZENNE and LOEB 2 ) they are thrombin, or at least bodies hav- 

 ing an analogous action. 



L. LoEB, 3 who has carried out complete investigations on the coagu- 

 lation of blood, especially of Crustacese, has arrived at the following 

 view: The coagulation in the Crustacea? can, according to him, be of two 

 kinds. It may in part be an agglutination of the amcebocytes and 

 in part a fibrin formation from a fibrinogen of the plasma. This latter 

 coagulation is essentially the same as occurs in vertebrates. The sub- 

 stance acting here as the excitant for the coagulation is also active in 

 the absence of lime salts, and behaves therefore like a thrombin. The 

 tissues contain constituents which accelerate coagulation which LOEB 

 calls coagulins, which are not identical with the coagulins of the clot 

 or the blood serum, and these have also, although only in the presence of 

 lime salts (if the author understands LOEB), a direct coagulating action 

 upon fibrinogen. According to LOEB the tissue coagulins do not act 

 as kinases in the invertebrates, and he also finds it improbable that 



1 Bioch. Zeitschr., 11. 



2 Huiskamp. Zeitschr. f. physiol. Chem., 34, 39; Delezenne, Arch, de physiol., 

 1897; Loeb, Biochem. Centralbl., 6, pages 829 and 889. 



3 Medical News, New York, 1903, and Virchow's Arch., 176; Hofmeister's Beitrage, 

 5, 6, 8, 9, and Biochem. Centralbl., 6, pages 829 and 889. 



