VI 



pletc precipitation in the k\sl lul)es with the greatest 

 amount of serum, through decreasing agglutination with 

 finer and finer clumps until no agglutination at all can 

 be observed. A test tube, with a not too advanced agglu- 

 tination, will easily be distinguished from its neighbours 

 through the size of its clumps. Such a test tube was 

 taken out and as quickly as possible used for the deter- 

 mination of the tube in each of the other series which 

 showed the corresponding degree of agglutination. 



That, which was obtained in this way, was the 

 relation between the agglutinating power of the sera to 

 be tested, and just this relation was of importance for 

 the following experiments. A control was usually made 

 by repeating the comparison with another test tube 

 containing a litte more agglutinin. 



This way of determination is based upon a similar 

 principle as the colorimetric method, used for measu- 

 ring hsemolytic toxins 1 ). By some practise rather exact 

 results are easily obtained. 



The most convenient way to determine the amount 

 of agglutinin would be to keep the test tubes at exactly 

 87" for just the same time and always use the same 

 degree of clarification as a standard. But as the con- 

 ditions for the agglutination depend upon many cir- 

 cumstances which cannot be regulated, it was found 

 more practical to have a standard agglutinin and always 

 use the same dose of it for the test. 



The following example will give the best idea of the 

 mode of proceeding. 



A rabbit, treated with increasing doses of B. typhos. 

 culture, got on the 23 / y an injection of such a culture 

 and the following days until the 33 / 4 the variations of 

 agglutinin in its serum had to be examined. 12 sam- 

 ples of blood were taken. 



i) Th. Madsen: Ueber Tetanolysin. Zeitschr. f. Hygiene etc. XXXII. 1899. 



