138 PHYSIOLOGY CHAP. 



The watery extract containing thrombin quickly produces 

 fibrinous coagulation, either from solutions of pure fibrinogen, 

 containing a small amount of lime salts in solution, or from the 

 fluid transudate of hydrocele. When injected rapidly in moderate 

 doses into the vascular system of an animal, instantaneous death 

 may be produced by diffused thrombosis, which inhibits the circula- 

 tion of the blood (Edelberg). 



That there is in circulating blood no thrombin proper, but 

 only pro-thrombin, is proved by the fact that the watery extract 

 has no coagulative action when it is obtained (as above) not from 

 defibrinated blood or serum, but from fresh blood received direct 

 from the vein into absolute alcohol (Jakowicki). The perfect 

 ferment, or thrombin, is only formed when the blood-corpuscles 

 have been injured or disintegrated. 



Thrombin in a watery solution is not attacked by antiseptics ; 

 on warming to 75 C. it loses all its enzyme action ; it exhibits 

 the general properties of the globulins, and is a phosphorus-free 

 protein. 



Thrombin is not, however, the only substance derived from 

 leucocytes which is able to determine coagulation by the trans- 

 formation of fibrin. Besides these enzymes there are other 

 substances (particularly in the nuclei of leucocytes and the proto- 

 plasm of blood-platelets) which can produce the same effect, as has 

 recently been established by the experiments of Lilienfeld. 



We have seen that the fundamental substance of the nuclei of 

 leucocytes is a highly complex structure, which is termed nucleo- 

 histone because it results from the association of two groups, one an 

 acid phosphorus containing leuconuclein, the other basic, with the 

 properties of albumoses. Now Lilienfeld has demonstrated that 

 not only leuconuclein but also its derivative, nucleic acid, are 

 capable of decomposing fibrinogen and of producing fibrinous 

 clotting under all conditions in which Schmidt's thrombin has the 

 same action. Histone, on the other hand, not only does not excite 

 clotting, but, like other albumoses, has anti-coagulative properties, 

 both for circulating and for shed blood. 



From the blood that is rendered incoagulable by histone it is 

 possible to separate a histonised plasma that is highly resistant, 

 and only coagulates on the addition of nucleic substances. The 

 an ti- coagulating substance obtained by A. Schmidt from the 

 alcoholic extract of lymph glands, which he called cytoglobulin, 

 corresponds essentially with histone. 



Lilienfeld's results thus tend to prove that coagulation can 

 occur without 'fibrin ferment, through the action of the nuclein 

 substances of the leucocytes and platelets ; yet, as Carbone shows, 

 there is a considerable analogy in respect to the production of 

 fibrin ferment between the theory of Schmidt and that of 

 Lilienfeld. 



