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. 1 



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 2 ; 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 3 ). 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 



1 Buckmaster, Morphology of Normal and Pathological Blood, p. 212, 1906. 



2 Gamge, Text-book of Physiological Chemistry, vol. i. 1880. 



3 Ibid vol. i. p. 79. 



