416 



INFECTION AND RESISTANCE 



4. The poisons can be produced from boiled as well as from na- 

 tive bacteria. 



Although unsuccessful with none of the bacteria with which ex- 

 periments were carried out, different species yielded the poison with 

 varying degrees of intensity, though qualitatively the poisons were 

 similar. Bacillus prodigiosus, though non-pathogenic, seems, in 

 general, to be one of the most favorable microorganisms for such 

 experiments. 



Since a clear understanding of Friedberger's basic experiments is 

 essential to the further development of the theoretical conceptions 

 which have been based upon them, it will be useful to insert here a 

 protocol taken from his paper with Goldschmid. 



Experiment VI. 30, VI, 1910. Ten 3-day agar cultures of 

 typhoid bacilli washed up in salt solution 5 c. c. to 1/2 culture. 

 Varying amounts of inactivated typhoid immune serum are added, 

 the tubes brought to 11 c. c., 24 hours in refrigerator. 1, VII 

 Centrifugalized and to sediment added 4 c. c. guinea pig complement 

 (active or inactivated), 24 hours in refrigerator. 2, VII Centrif- 

 ugalized and supernatant fluids injected into guinea pigs of 200 

 grams intravenously. 



From Friedberger and Goldschmid, loc. eit., p. 402. 

 sion of control 19.) 



(Changes made only in wording and onus- 



This series alone shows that, under the given conditions, 4 c. c. 

 of alexin will produce the poison with 1/2 slant of typhoid bacilli, 

 without sensitization (tubes 1 and 2), with sensitization ranging 

 in degree from 1 c. c. to 0.001 c. c. of the given immune serum 

 (tubes 5, 6, 9, 10, 12, and 14), and that inactivation of the alexin 

 serum in all cases prevented the poison formation. Normal guinea 



