Ill 



thus the red blood corpuscles sink to the bottom of the test 

 tube without being further, to any great extent, affected. 



This method gives us, as will be shown later on, 

 more complicated results than those methods in which 

 the reaction is suddenly interrupted. The latter was 

 used, when an exact determination of the time of the 

 reaction was required. Then the test tubes, when the 

 reaction was over, were put into a mixture of salt and 

 ice, so that their temperature in a few minutes was re- 

 duced to C. After that they were as a rule centri- 

 fugalised; this took about 6 minutes. 



If we add a large amount of haemolytic body to the 

 bloodmixture, complete haemolysis occurs. Starting 

 from a certain concentration upwards, all toxins appa- 

 rently act in the same manner, total haemolysis having 

 then taken place (under the category of toxin we in- 

 clude all the haemolytic acting substances). On the other 

 hand the haemolysing action decreases rapidly with the 

 decreasing quantity of toxin. If therefore the quantity 

 of toxin is below a certain amount the haemolysis pro- 

 duced is not recognizable. Quantifies of toxin, the ac- 

 tion of which would be to produce almost complete 

 haemolysis or on the other side be very near the 

 limit, where it becomes recognizable, are unsuitable for 

 these investigations. When we used the 2,5% blood 

 mixture, we obtained the most exact results in the 

 cases where the haemolysis comprised 4 20 percent of 

 the red blood corpuscles. To this variation in the strength 

 of haemolysis a variation in the amount of toxin in the 

 relation of about 1 : 3 corresponded. It is thus a com- 

 paratively small interval in which the doses, suitable 

 for the experiments, lie. 



We proceeded therefore in such a way, that to 10 cc. 

 of bloodmixture different amounts of toxin were added 



