320 THE BLOOD. 



thrombin), which is then transformed by the alkali or acid into neozym (=/3- 

 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 

 PEKELHARISG l 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, 

 HUISKAMP, DELEZENNE and LOEB 2 ) they are thrombin, or at least bodies 

 having an analogous action. 



CRAMER and PRINGLE S have made the important observation that a 

 carefully prepared oxalate plasma when filtered through a Berkefeld 

 filter does not coagulate on adding calcium chloride, while the unfiltered 

 but centrifuged plasma does coagulate. The reason for this lies in the 

 fact that centrifuged plasma contains blood-plates, which are absent 

 in the filtered plasma. By means of these blood-plates, which yield 

 thrombokinase, the coagulation is produced on the addition of calcium 

 chloride. The points in NOLF'S theory of coagulation that are difficult 

 to understand as well as the observations of FREUND (page 313) and of 

 BORDET and GENGOU (page 314) are explained by this observation. 



L. LoEB, 4 who has carried out complete investigations on the coagulation of 

 blood, especially of Crustacea, has arrived at the following view: The coagula- 

 tion in the Crustacea can, according to him, be of two kinds. It may in part 

 be an agglutination of the amrebocytes and in part a fibrin formation from a fibrino- 

 gen of the plasma. This latter coagulation is essentially the same as occurs in 

 vertebrates. The substance 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, 



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 Quarterly Journ. of exp. Physiol., 6. 



4 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. 



