173 



Üntill now next to nothing was known of the former question, 

 whilst the hitter has given rise to a great many investigations which 

 have resulted in more or less divergent theories, without a definite 

 solution of the problem being arrived at. Tlie latter circumstance is 

 naturally connected with the former; as long as the nature of the 

 relation between tibrinogen and tibi-in, the base so to speak of the 

 problem relating to blood-coagulation, was unknown, a solution of 

 this problem could hardly be expected. 



As I believe that my. investigations bearing on this subject have 

 brought to light the nature of the relation between fibrinogen and 

 fibrin, I beg leave to give the following shorty account of the 

 researches which have led to this result. 



Beforehand it should be observed that originally it was by no 

 means my intention to occupy myself with researches in this 

 direction. It was rather some observations, made in the course of 

 experiments, undertaken for another purpose, which suggested to 

 me a series of investigations relating to fibrin, with a view to the 

 problem of blood-coagulation. I had observed, for instance, that an 

 addition of an acid, to a solution of fibrin in strongly diluted NaOH 

 caused a precipitate, which, after being left to itself for some time, 

 was found to have passed into a fibrous coagulum. This observation, 

 which naturally struck me verj much, was first made with phos- 

 phoric acid and afterwards also v/ith other acids ^). 



When subsequently it was investigated more closely under what 

 experimental conditions coagulation in fibrin-NaOH solution took 

 place when an acid was added, it appeared : 



1. that by adding drops of HCl of a rather high concentration, 

 to a fibrin-NaOH-solution, an acid coagulum in an alkaline medium 

 could be obtained, which coagulum disappeared again when it was 

 shaken and could be produced again by the addition of more HCl, 

 as long as the fluid gave a distinctly alkaline reaction. 



2. That by an addition of so much ROl, either gradually or at 

 once, that, the solution was about neutral a permanent coagulum 

 could be obtained. 



3. That likewise a permanent coagulum was obtained by an 

 addition of so much HOI that the medium became strongly acid. 



4. That an addition of so much HCl that a feebly but distinctly 



1) The fibrin-NaOH-solulion had been obtained by exposing ordinary fibrin to a 

 strongly diluted NaOH-solution (e.g. 0.3%,). The fibrin swells in it strongly, the 

 swollen mass gradually passes into a liquid state and finally forms a thin liquid 

 solution. Such a solution, after being filtered, was used for the experiments. 



