384 BACTERIOLOGY. 



lus which killed by means of diphtheria toxin or, in 

 other words, not simply a virulent bacillus, but a viru- 

 lent diphtheria bacillus. When the bacilli to be tested 

 grow poorly in the simple nutrient bouillon they should 

 be grown in bouillon to which one-third its quantity of 

 ascitic fluid has been added. Quite a number of bacilli 

 have been met with which killed 250 gramme guinea- 

 pigs in doses of 2 to 15 c.c., and yet were unaffected 

 by antitoxin. These bacilli, though slightly virulent 

 to guinea-pigs, produce no diphtheria toxin, and so 

 cannot, to the best of our belief, produce diphtheria in 

 man. 



