41 



respective homologous strains, both the agglutinins and pro- 

 tective substances are removed with the deposited cocci. For 

 example, 3 c.c. of T. I serum were treated with the deposit of 

 200 c.c. of heated broth culture contained in 4 o.c. of broth: 

 after the mixture had stood overnight in the ice-chest, it was 

 centrifuged and the supernatant fluid was removed for inocu- 

 lation into mice in doses of 0*5 c.c. (i.e., equivalent to 0*2 c.c. of 

 serum). 



Protection Test with absorbed and unabsorbed 

 Type I Serum. 



The Type I culture was fully virulent, and control mice inocu- 

 lated with 0000 000 01 c.c. of broth culture died in 2 days. 



The sera of Type I and Type II were fairly readily exhausted 

 of their content of protective substances by treatment with the 

 homologous strain. On the other hand greater difficulty has 

 been experienced in removing the protective power from the 

 particular Group IV sera which have been tested, in spite of the 

 use of large quantities of the absorbing culture. 



There are technical difficulties in the way of demonstrating 

 complete exhaustion of a strong protective serum. As is well 

 known, a single treatment of a concentrated serum with the 

 homologous culture cannot remove the whole of the agglutinins 

 and similar antibodies. 



The serum cannot be diluted beyond a certain point, since 

 it is not desirable to inoculate a larger amount of fluid than 

 0-5 c.c. or at the most 1*0 c.c. intraperitoneally into a mouse. 

 With a dilution of 1 in 2*5, which has generally been used, the 



