8 



gated into a firm mass ; with the filtrate of the R culture there 

 was no visible reaction. 



The serum prepared with the R culture gave a precipitate 

 neither with the R nor with the S filtrate. 



Absorption of Agglutinin. — The serum of the rabbit immunised 

 with S culture lost after treatment with S culture all its agglu- 

 tinins, i.e., both for R and S suspensions. Treatment with the 

 R culture removed the agglutinin for the R and left unaltered the 

 agglutinating capacity of the serum for the homologous S strain. 



The serum of the rabbit prepared with the R strain required 

 two successive treatments with the R culture before it lost the 

 whole of its homologous agglutinin. Similar treatment with the 

 S culture did not exhaust the homologous agglutinin from the 

 R serum, but reduced the titre for the R strain from 1 in 640 to 

 1 in 160. 



Protection of Mice with R and S Sera. — The S serum, injected 

 intraperitoneally into mice in doses of 02 c.c, protected them 

 against a subsequent inoculation of doses of a Type I. strain 

 ranging up to 0*1 c.c. of broth culture, the virulence of which was 

 such that 0-000,000,01 c.c. of broth culture killed an unprotected 

 mouse within two days. Against the same strain of Type I. all 

 the R sera failed to show any protective power. The inoculation 

 of the three rabbits with R culture was continued in order to 

 ascertain whether more prolonged treatment would induce the 

 development of antibodies against the virulent strain. The 

 three rabbits were retested after they had been immunised for 

 a total period of four months, during which each rabbit received 

 26 intravenous injections. Their sera still failed to show the 

 presence of protective substances, when tested against a Type I. 

 culture which killed mice in a dose of 0*000,000,01 c.c. Two 

 other rabbits, which had been injected with the S culture for 

 five weeks and were tested at the same time, yielded sera which 

 protected mice against doses of - l c.c. of the above culture. 



Influence on the Type of Colony by Growth 

 in R and S Sera. 

 A virulent Type I. culture was grown in R serum and in S 

 serum. There was no alteration in the character of the colonies 

 obtained on plates after three successive passages through the 

 R serum. On the other hand the culture grown in the S serum, 

 when plated after incubation overnight, yielded a mixture of R 

 and S colonies. One of each variety was subcultured in plain 

 blood broth, and was tested for virulence on mice. The S strain 

 killed mice in a dose of 0000,000,1 c.c. of broth culture, while 

 0*2 c.c. of the R strain proved innocuous. 



Agglutinability of R and S Strains. 



The clumps formed after the interaction between a virulent 

 pneumococcus culture and homologous immune serum are very 

 characteristic. On the addition of a 1 in 10 dilution of the serum 



