1911.] Immunisation by Means of Bacterial Endotoxins. 53 



Series I. — Six guinea-pigs, each weighing 230 to 240 grm. were inoculated 

 with the diphtheria endotoxin on July 7, 1909, three receiving 1 mgrm. each, 

 and three - 5 mgrm. each of the endotoxin. One of the guinea-pigs which 

 received 1 mgrm. died on July 12. The five survivors, together with two 

 controls, were each inoculated subcutaneously with 1/10 of a loop of a 

 24-hour blood-agar culture of virulent diphtheria. The virulence of this 

 strain of diphtheria bacillus had been previously tested on June 25 with the 

 following results (Table V) : — 



Table V. — Virulence of Diphtheria Culture. 



Reference letter 

 of guinea-pig. 



Amount of 

 culture. 



Eesult. 



E 

 B 

 Z 

 A 

 P 



2 loops 



- 5 loop 

 0-1 loop 

 0-01 loop 



+ Dead, June 27 (two days). 

 + „ ,. 28 (three days). 

 + » • „ 28 

 + „ ,. 28 

 Induration and paresis, July 2. 



One-tenth of a loop therefore contained at least three or four minimal 

 lethal doses. 



The result of the inoculation of the animals treated with the diphtheria 

 endotoxin, together with two controls, is given in the following table 

 (Table VI):— 



Table VI. — Inoculation of Vaccinated Animals with Culture (^ loop), 

 July 14, 1909. 



Eeference letter 

 of guinea-pig. 



Amount of 

 endotoxin. 



Eesult. 



O 



1-0 



Lived. 



The four survivors had 



E 



1-0 



+ Dead, July 21 



ulcers at the seat of 



P 



0-5 



Lived. 



inoculation of the 



L 



0-5 





culture on July 26. 



S 



0-5 



"„ 



The ulcers were tend- 



ss 



Control 



+ Dead, July 17 



ing to heal and the 



T 







animals lived on. 



The results indicate that the diphtheria endotoxin confers considerable 

 protection against the injections of living diphtheria bacilli. 



