IN RABBITS. 357 



oculations in New Orleans during the heat of 

 summer ; (#) that this virulence was not an indi- 

 vidual peculiarity, inasmuch as eleven rabbits, 

 inoculated with the saliva of six different persons, 

 gave eight deaths and three negative results. As 

 no account was made of the previous history of 

 these rabbits, it is now impossible to say whether 

 these negative results are to be ascribed to a less 

 degree of virulence of the saliva injected, or to 

 antecedent experimental injections which had pos- 

 sibly been made in the laboratory, and which 

 afforded these animals protection. Still, a differ- 

 ence in the degree of virulence was shown by the 

 fact that in these, and in numerous subsequent 

 experiments, the writer's saliva has never failed to 

 kill unprotected rabbits within forty-eight, or at most 

 sixty hours ; while in a considerable number of 

 experiments with the saliva of other persons, there 

 have been several failures to kill; and in other 

 cases the fatal result has been delayed to three or 

 four days, and even longer. This difference could 

 not be accounted for as being connected with un- 

 sound teeth or the use of tobacco. The writer 

 has sound teeth, and the secretions which accumu- 

 late in his mouth are normal in appearance and 

 reaction, and free from any odor. 



The facts thus far observed seemed to be 

 worthy of fuller investigation, with a view to 

 explaining the cause of this virulence ; and in the 

 month of March further experiments were com- 

 menced in the biological laboratory of Johns Hop- 



