THE COAGULATION OF THE BLOOD 55 
coagulation may be as low as 5 minutes or as high as 14'5, a 
statement which I can confirm, though the method which was 
employed differed from that which he has described.’ 
3. STATE OF THE SUBJECT AT THE CLOSE OF THE YEAR 1880 
The examination of the blood was essentially a study of 
those few early observers whose work at that time comprised 
not only the practice of medicine, but also all those subsidiary 
sciences bearing upon this subject which are to-day in some 
cases unfortunately so widely dissociated from medicine. 
During this time, which was succeeded by the period of 
humoral pathology, the contributions of Hewson and John 
Hunter form a definite starting-point in our knowledge of the 
coagulation process. The early discoveries of Hewson, those 
of Buchanan of Glasgow in 1845, those of Denis, who isolated 
a sero-fibrin, which he subsequently termed plasmine, from 
salted plasma—a substance which he proved, when mixed with 
water, gave a clot—down to the earlier work of Alexander 
Schmidt and Olaf Hammarsten on the conditions and factors 
influencing coagulation, have been already admirably de- 
scribed”; and our definite knowledge concerning the process 
of coagulation of the blood outside the body at the close of the 
year 1880 may, in the light of subsequent work, be briefly 
stated. Blood retained within the living vessels does not clot 
readily. Further, the plasma of blood clots in the same way 
and as readily as the whole mass of the blood. Contact with 
foreign material accelerates the clotting process or conceivably 
induces this, since blood remains unclotted for days when 
removed from the body with its containing vessel, or even if 
the wall of the vessel be replaced by a perfectly clean glass tube 
(Lister *). A definite protein substance—fibrinogen—can be 
precipitated from plasma, and solutions of this can yield fibrin. 
Moreover, fibrinogen exists as such in the plasma of normal 
living blood, since it can be thrown down as an insoluble body 
from living blood. The important proof of this fundamental 
statement is due to Fredrique, who, in 1877, repeated an old 
experiment of Hewson. He removed the jugular vein of a 
' Buckmaster, Morphology of Normal and Pathological Blood, p. 212, 1906. 
* Gamge, Text-book of Physiological Chemistry, vol. i. 1880. 
3 [bid vol. i. p. 79. 
