THE COAGULATION OF THE BLOOD 63 



existing between the fibrinogen of blood and that other 

 fibrinogen which originated from the tissues. He regarded 

 the protoplasma as a living substance, capable, as he said, of 

 being stimulated by such agents as carbon dioxide or weak 

 acetic acid, so that a response or coagulation occurred. 1 



Tissue-extract is allowed by all observers to contain much 

 nucleo-protein. The differences between this substance obtained 

 from blood-plasma, leucocytes, or tissues such as the thymus 

 or testis, and Schmidt's fibrin-ferment have been pointed out by 

 many workers. Halliburton and Brodie, 2 among others, have 

 insisted upon this difference. Whether nucleo-protein possesses 

 a ferment action or whether in the preparation of this sub- 

 stance it becomes contaminated with thrombin, the same 

 questions may be asked with reference to tissue-extracts, and 

 investigations into the relations of these to the non-coagulating 

 plasmata of birds have permitted a definite answer to be 

 obtained, and at the same time enabled ,a large number of 

 conflicting facts to be explained. 



Although early observations on the coagulation of birds' 

 blood showed that this quickly coagulated, Schmidt and Tiegel 

 could not confirm this. The discoveries of Delezenne in 1897 

 that birds' plasma remained uncoagulated, that when the sedi- 

 mented blood did coagulate the phenomenon started at the zone 

 of leucocytes just above the red corpuscles and slowly extended 

 upwards and downwards through the blood, and that both 

 the blood and completely cell-free plasma quickly coagulated 

 on the addition of tissue-juice from any source, have been 

 confirmed by all observers. Among other work bearing on this 

 subject that of Phisalix, 3 Fuld, 4 Fuld and Spiro, 5 Wright, 6 and 

 Morawitz 7 may be mentioned here. 



According to Fuld's view, whether thrombin action is 

 similar or not to that of other enzymes, the formation of 

 thrombin is due to the interaction of three factors which exist 

 in the plasma of circulating blood or in plasma of unaltered 

 blood outside the body. These are : 



1 Wooldridge, Collected Papers. 



2 Journal of Physiology, xvii. 1888. 



3 Comptes rend. li. pp. 881 and 885. 



4 Centralbl. f Physiologie, p. 529, 1903. 



5 Hoftneister 's Beilrdge, v. p. 171, 1904. 



6 Journ. of Phys. xxviii. 



7 Arch, f Klin. Med. lxxix. ; Hofnieister's Beifrdge, v. 1904. 



