183 



They were absorbed for 6 hours at room temperature with 

 frequent shaking. The dilutions of the unabsorbed serum were 

 made at the same time as those in the absorption experiment, 

 and were kept at the same temperature. 



It will be noticed that while the homologous strain even in a 

 concentration of 4, absorbs all the agglutinin in a serum concen- 

 tration as strong as 1:20, none of the heterologous strains absorb 

 enough of the agglutinin to make it possible to demonstrate the 

 deficiency with certainty although the experiment is arranged under 

 conditions likely to be extremely favourable for showing the pre- 

 sence of absorption power. 



Nor could any absorption whatever be demonstrated in a repeti- 

 tion of the experiment with serum I 6 and strains I 21, H 34 and 

 Pa 5; serum I 21 and strains I 6, H 34, and Pa 5; serum H 31 

 and strains I 6 and I 21; and with serum Pa 5 and strains I 6, 

 I 21 and H 34, with varying technique (weak serum concentrations 



— large bacterial concentrations). 



An absorption test was made with the serum I 6 in a concen- 

 tration 1 : 160 and the strain H 34 in a concentration 10 in such 

 a way that after centrifuging fresh culture in the same concentra- 

 tion as before was ground up with the separated serum and this 

 was repeated once more. In each of the three absorptions the 

 mixture of serum and culture was allowed to combine for one hour. 

 In spite of the repeated treatment of a highly diluted serum with 

 a liberal amount of culture, the serum agglutinated its homologous 

 strain iri just as high a dilution as the untreated serum. The same 

 was the case in similar experiments with three-fold absorption of 

 serum H 34 in a concentration 1 : 40 with strain I 6 in a con- 

 centration 10. ' 



The agglutinative properties of the lour strains examined 



— which were chosen quite at random — proved therefore 

 to be absolutely specific for each strain. No common relation- 

 ship could be demonstrated. 



In addition to the experiments described, numerous agglutina- 

 tion tests were performed in the orientation of the technique, which 

 will not be reported further. One of the results of these tests 

 was that inhibition of agglutination sometimes occurred in the two 

 first tubes (1 : 25 and 1 : 50), but never in the following ones. It 

 was also found that the milder degrees of group agglutination may 

 be rather variable, and that strains with absorptive power for he- 

 terologous agglutinin were only present among those showing .par- 

 ticularly marked agglutination with the homologous agglutinin. Group 

 agglutination only in a dilution of 1 : 25, must for the last two reasons, 

 be considered to have special significance. 



