175 



Yet the new problems which had presented themselves so unex- 

 pectedly, were fully deserving of attention. Not only from a general, 

 biological or a colloid-chemical point of view, but also because it 

 was clear that the solution of these questions might open new views 

 on the important problem of the nature of blood-coagulation, and 

 perhaps also on that of thrombus-formation. 



These questions were therefore submitted to n further investigation. 



In this investigation it had to be determined in the first place 

 which part of the fibrin produced the coagulating substance, either 

 the fibrin proper, as I began to suspect, or the attendant substances. 



Therefore pure phrin free from blood-corpuscles was experimented 

 on. This pure fibrin was obtained from bloodplasma which was 

 kept fluid by receiving the blood in an equal volume Na-fluoride- 

 solution of 1 — 2 7o» or in a citrate-NaCl-solution. 



The blood taken from cow or horse, and kept fluid in this man- 

 ner, was centrifugated until the fluid at the top had become clear, 

 when the red and white blood-corpuscles and the blood-platelets 

 were obtained as a sediment. 



This clear fluid, which contained "fibrinogen", the parent sub- 

 stance of fibrin, was removed with a pipette and left to itself. 

 After some time, (from a few to 48 hours) a spontaneous coagulum 

 had been formed. 



The coagulum thus obtained, was filtered off" and the filtrate was 

 again left to itself. After a shorter or longer period a new coagulum 

 was found in the filtrate. This process of partial coagulation was 

 repeated 3 or 4 times, the coagulum obtained from the last filtrate 

 being used for the experiments. This somewhat lengthy method was 

 followed in order to have the greatest possible certainty that all 

 blood-corpuscles, including the blood-platelets, had been removed, 

 so that the fibrin was obtained in as pure a state as possible. 



The somewhat coloured coagulum thus obtained, grew white 

 when washed with water, and consisted of a mass of elastic fibres. 



It soon appeared that this pure fibrin dissolved readily in strongly 

 diluted NaOH, Naj CO3 and in strongly diluted acids, wdiich solution 

 was preceded by a short stage when the fibres were visibly swol- 

 len. The swollen fibres were absolutely transparent, as clear as 

 glass, not turbid ly transparent as I had observed in the case of 

 ordinary fibrin. 



I shall first describe some experiments, made with solutions of this 

 pure fibrin in diluted acids, for instance in 0,1 "/o orthophosphoric acid. 



These and the following experiments were always carried out at 

 room-temperature. 



