181 



sorption progressed at least as far when after mixing the bacterial 

 suspension and serum the tubes were allowed to lie in an almost 

 horizontal position without touching them, as when they were stood 

 op and frequently shaken. 



In experiments with homologous agglutination by various sera 

 no difference in the absorption power of cultures could be di- 

 stinguished, which had been cultivated for 12, 24 or 39 hours. 



As a standard method I have adopted a serum dilution of 1 : 20 

 and a bacterial concentration of 5. After mixing the serum and 

 suspension I have allowed the tube to lie down without shaking 

 for 2 hours at room temperature. The bacteria were then cen- 

 trifuged down A series of tubes containing 0.4, 0.2, 0.1 c.c. etc. 

 of the supernatant serum was arranged and the volumes made up 

 to 0.4 c.c. To each tube 0.1c. c. suspension of concentration 2 of 

 the culture was added, for which the agglutinating power of the 

 serum after absorption was to be estimated. In the actual agglu- 

 tination test therefore there was serum in the dilutions 1:25, 1:50, 

 1:100 etc. and culture in the concentration 0.4. 



The concentrations of serum and culture employed were (with 

 a single exception — Pa 5) always sufficient to allow the homo- 

 logous strain to remove the agglutinin „completely" by absorption 

 from a serum, by which is to be, understood that the serum after 

 absorption gave no reaction even in a dilution of 1:25. 



In many cases the serum and culture were employed in other 

 concentrations. The details are given under each individual case. 



As a preliminary orientation of the relation of the different 

 strains to one another as regards agglutination, a simple agglutination 

 experiment was carried out with each of the strains I 6, I 6, H 34, 

 and Pa 5, and each of the sera prepared with these strains. The 

 result was as follows: 



Sera 



'3 1 



H 34 Pa 5 



Vfg Vso V100 Vaoo Vwo Vmo Vimo Vmoo Vmoo Vis Vso Vim Vmo Vmo Vmo Vimo Vbm V«4m 



1 6 



1 21 



H34++ + 



n M _j_ _|_ _|_ (+) 



Pa 5 



