THE COAGULATION OF THE BLOOD. 



THIRD PAPER. 



HAMMARSTEN'S theory of the cause of blood- 

 clotting was formulated over twenty years ago, 

 and it has stood the severe test of time, before which so 

 many physiological theories fall to the ground. It still 

 continues to be the best working theory we have on the 

 subject. Put briefly it runs as follows : — 



In the living blood, a proteid of the globulin class called 

 fibrinogen exists in solution. When the blood is shed, the 

 fibrinogen molecule is split into two parts ; one part is a 

 globulin which remains in solution, the other and more 

 important part is the insoluble proteid called fibrin, which 

 entangles the corpuscles and produces the clot. This 

 decomposition of fibrinogen is accomplished by the fibrin- 

 ferment which is one of the products of the disintegration 

 of white corpuscles, blood-tablets and other protoplasmic 

 structures that occurs when the blood leaves the vessels 

 or comes into contact with foreign matter. 



This theory replaced the older one of Alex. Schmidt 

 who taught that fibrinogen and paraglobulin were both 

 necessary for the formation of fibrin. 



Since Hammarsten's theory was formulated investiga- 

 tors have not been idle, and in two papers published in 

 this Journal,^ I have given an account of the principal 

 work that has been done in relation to the question. This 

 work includes that of Wooldridge who introduced the im- 

 portant method of studying coagulation in the blood-vessels 

 themselves, and in not being content with mere experi- 

 ments z>2 z^z'/r^. He showed that the " tissue-fibrinogens," 

 substances obtainable from most of the cellular oroans of 

 the body, will, when injected into the circulation of a living 

 animal, produce intravascular coagulation. These tissue- 

 fibrinogens are nucleo-proteids, and fibrin-ferment belongs 



^ Vol. ii., p. 369 ; vol. iii., p. 127. 



