43 



Effect of Intravenous Inoculation of Culture on the 

 Protective Substances and Agglutinins in an Immunised 



Animal. 



The subject of the experiment was a rabbit which had already 

 been immunised against a pneumococcus of Group IV, but 

 which had not been inoculated for two months. The object was 

 to ascertain (1) the effect of re-inoculation of culture upon the 

 antibodies present in the serum, and (2) the time after the re- 

 inoculation at which these suostances attained their maximum 

 concentration. A specimen of the rabbit's serum was taken 

 before the inoculation, which consisted of the deposited cocci 

 from 100 c.c. of broth culture heated to 60° C. for \ hour and 

 administered intravenously at four short intervals. Samples 

 of blood were taken the day after inoculation and on the 3rd, 

 5th, 9th and 11th days. The sera were preserved in the ice- 

 chest until the final bleeding, and the tests of protection and 

 agglutination with all the samples were made on the same day. 



The serum before inoculation did not agglutinate in 1 in 5 

 dilution; it protected against 0*000 001 c.c. of broth culture of 

 the homologous strain but not against 0*000 01 c.c. 



The day after inoculation there was no agglutination and no 

 protection. On the 3rd day there was still no agglutination 

 demonstrated in 1 in 5 dilution, but the serum protected against 

 0*000 1 c.c. of culture (5 out of 6 mice) and 0*001 c.c. (1 out of 

 2 mice). 



On the 5th day the serum contained agglutinins and pro- 

 tected against 0*01 c.c. of culture (3 mice), but there was some 

 irregularity, as one or two of the mice inoculated with smaller 

 quantities of culture died. The 9th and 11th day samples of 

 serum protected against 0*01 c.c. of culture, but failed to protect 

 against 0*1 c.c. ; apparently the maximum protective power was 

 attained on the 5th day. 



The rabbit was given a rest of three weeks. At the end of 

 this period its serum gave only a faint trace of agglutination and 

 had lost some of its protective power, e.g., 1 out of 5 mice sur- 

 vived a dose of 0*000 1 c.c. of culture and 3 out of 4 mice a dose 

 of 0*000 01 c.c. The inoculation of heated culture deposit of 

 200 c.c. of broth culture was then repeated. After the re-inocula- 

 tion agglutinins and protective substances were absent from the 

 samples of serum collected on the 1st and 2nd days. 



On the 5 th day the agglutininins had reappeared and the 

 serum again protected against 0*01 c.c. of culture (2 out of 4 mice) 

 This titre was maintained on the 9th and 1 lth days, but in no 

 instance was the serum found to be sufficiently strong to protect 

 against 0*1 c.c. of culture. 



In the course of the above protection tests there was notice- 

 able a certain irregularity in protection, e.g., a sample of serum 

 protected some mice against 0*01 c.c. of culture but failed to 

 protect every mouse against an inoculation of a smaller dose. 



