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.} 
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,? 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 ja 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,’ Fuld,t Fuld and Spiro,’ Wright,® and 
Morawitz’? 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: 
' Wooldridge, Collected Papers. 
* Journal of Phystology, xvii. 1888. 
3 Comptes rend. li. pp. 881 and 885. 
* Centralbl. f. Phystologie, p. 529, 1903. 
5 Hofmeisters Bettrage, v. p. 171, 1904. 
6 Journ. of Phys. xxviii. 
” Arch. f. Klin. Med. \xxix. ; Hofmeisters Bettraége, v. 1904. 
