THE COAGULATION OF THE BLOOD 955 



is still somewhat uncertain, the fact that blood-serum often has an 

 inhibitory effect on the action of a solution of fibrin ferment points 

 to the presence in the serum of some antibody to the ferment. One 

 must assume too that processes of disintegration are continually 

 occurring in the blood and involving the plasma, blood-platelets, and 

 leucocytes, just as we know them to affect the red blood-corpuscles. 

 In the healthy animal the liberation of thrombokinase which must 

 take place under these circumstances has no influence in producing 

 clotting. The organism therefore must possess means of neutralising 

 the presence of small quantities either of kinase or of fibrin ferment. 

 When small quantities of either of these substances are injected into 

 the blood- stream no coagulation takes place, but the blood obtained 

 after the injection clots with less readiness than before, a change 

 which can only be ascribed to the production in the body of antikinase 

 or of antithrombin. This production of anticoagulins must be 

 continually taking place and must co-operate in the preservation of 

 the fluid state of the blood while in the vessels. 



INTRAVASCULAR CLOTTING. On account of the protective 

 mechanisms with which the animal organism is endowed the production 

 of clotting in the vessels of the living animal is not readily effected by 

 the injection of thrombin. Solutions obtained by Schmidt's method 

 from alcohol-coagulated serum are generally without effect, and we 

 have to inject a very strong solution of thrombin or the strong fibrin 

 ferment contained in the venom of certain snakes in order to bring 

 about coagulation of the blood in the vessels. Intravascular clotting 

 is more easily effected by the injection of thrombokinase. It was 

 shown by Wooldridge that normal saline extracts of tissues rich in 

 cells, such as the thymus, lymph-glands, or testis, causes invariably 

 extensive thrombosis. If such extracts be acidified with acetic acid 

 a precipitate is produced which is soluble in dilute alkalies, and on 

 gastric digestion yields a precipitate rich in phosphorus. Alkaline 

 solutions of the acid precipitate bring about intravascular clotting 

 when injected into the blood-stream. According to Wooldridge the 

 injected substance takes part in the formation of the clot, and he 

 therefore gave it the name of ' tissue fibrinogen.' It is usual to regard 

 these tissue fibrinogens as nucleo-proteins. They are certainly rich 

 in lecithin, and the precipitate obtained from them on gastric digestion 

 may contain as much as 25 per cent, of this substance. They must 

 be derived either from the cytoplasm or from the interstitial fluid of 

 the tissues, and it is still doubtful whether we are justified in giving 

 them the name of nucleo-proteins or whether we should not rather 

 classify them with the phospho-proteins which play so great a part 

 in the building up of the cytoplasmic part of the cell. We may 

 explain the action of these tissue extracts as due to their containing 



