ACTIVATORS, KINASES AND HORMONES 187 



complement, to form a new and active compound, the tryp- 

 sin, and the whole reaction has been still further compli- 

 cated by the discovery (Delezenne) that the trypsinogen 

 may be activated by calcium salts without the presence of 

 enterokinase. The action of the calcium requires some 

 time for its development, but when it occurs it takes place 

 not gradually, but abruptly, just as in the case of the 

 activation produced by enterokinase. The further fact 

 stated by Delezenne that the enterokinase itself needs the 

 presence of calcium salts before it acquires the property of 

 affecting trypsinogen suggests naturally the thought that 

 the action of the enterokinase may be at bottom another 

 case of calcium activation. Pozerski states that in the in- 

 active pancreatic juice obtained by injections of secretin 

 calcium is not present; whereas in the active juice follow- 

 ing upon the use of pilocarpin, calcium is contained, and 

 the digestive action of the juice runs parallel with the con- 

 tent in calcium. But whether the enterokinase acts as a 

 ferment, or an amboceptor, or a calcium carrier it consti- 

 tutes a special type of organic activator, and this fact sug- 

 gests the possibility that other processes in the body may 

 be controlled by similar compounds. At present only one 

 other organic activator of this kind has been described, 

 namely, the thrombokinase of blood coagulation. This 

 hypothetical substance is given great importance in the 

 theory of coagulation proposed by Morawitz. According 

 to this theory the blood corpuscles under abnormal environ- 

 ment yield an unknown substance of colloidal nature which, 

 together with calcium, is necessary for the complete activa- 

 tion of thrombin, and therefore for the clotting of blood. 

 A similar kinase is furnished by the tissues in general, so 

 that blood escaping from a vessel and coming in contact 

 with the surrounding tissues obtains from them a kinase 

 which accelerates the process of clotting. The evidence for 

 the existence of this kinase is far less satisfactory than in 

 the case of the enterokinase, indeed one may have serious 

 doubts whether the facts at present warrant the assumption 



