356 BACTERIA IN INFECTIOUS DISEASES. 



the skin of a rabbit. The unexpected death of the 

 animal led to a repetition of the experiment, with 

 the same result, except when the animal experimented 

 upon had previously been inoculated with various fluids 

 containing bacteria. These exceptions will be re- 

 ferred to later. 



The question at once arose in the writer's mind 

 as to whether the virulence of his saliva, as shown 

 by, these experiments, was an individual pecu- 

 liarity, due perhaps to some antecedent event in 

 his personal history, e. g., an attack of yellow 

 fever experienced in 1875 ; or whether it was due 

 to circumstances relating to his environment at 

 the time, e. g. ? residence in a Southern city dur- 

 ing the summer months, and constant contact with 

 putrefying organic material in the course of his 

 experimental studies ; or whether it was, possibly,' 

 a general fact that human saliva is fatal to rabbits, 

 when injected beneath their skin. 



These questions could evidently only be settled 

 by the experimental method, and a visit was made 

 to the city of Philadelphia, during the month of 

 January, 1881, for the purpose of pursuing the 

 investigation, with the kind assistance of Dr. 

 Formad, in the laboratory of the Medical Depart- 

 ment of the University of Pennsylvania, Here, 

 eleven inoculation experiments demonstrated 

 (a) that the virulence noted was not due to sea- 

 son or to locality, as the same result followed 

 inoculations made in Philadelphia during the win- 

 ter months as had been obtained by similar in- 



