370 DIPHTHERIA 



excluded. If an acid reaction results, then all the microscopical 

 and cultural characters must be carefully observed, and the 

 virulence of the bacillus may be ascertained by inoculating a 

 guinea-pig, say with 1 c.c. of a broth culture of two days' growth. 

 (See also pp. 359, 365.) A fatal result with characteristic 

 appearances may be taken as positive evidence, but if the animal 

 survive there is still theoretically the possibility that the 

 organism is an attenuated diphtheria bacillus (p. 364). 



