222 
HERMANN M. BIGGS. 
oculated children nor the dogs bitten have developed any syrap 
toms of rabies, the probable result is evident. 
At the time of the writer’s visit to Paris there were fron 
twenty to twenty-five persons being inoculated daily, and scarcely 
a day passed that some new patients did not present themselves 
"for treatment. 
The principles underlying Pasteur’s method for the preven 
tive treatment for hydrophobia may be stated in a few words as 
follows: The period of incubation of rabies as transmitted frou 
the dog to other animals and man is very variable, but in man 
as a rule, is exceedingly long, being rarely less than thirty days 
By the passage of rabies from dogs 'through a series of rabbits 
the period of incubation of the disease may be finally reduced tc 
about seven days, as it occurs in these animals. The virulence oJ 
the spinal cords from rabbits dead of a seven-day rabies may hi 
diminished in a constant degree by suspension in an absolutely 
dry air at a given temperature. Man or animals that have been 
subjected to a series of inoculations with these cords of diminished 
virulence, beginning with a very weak virus and gradually goino 
on to a stronger and finally to the most virulent form, gradually 
become insusceptible to the most virulent virus. The period of 
incubation of this virus is very short, and the time required to 
confer insusceptibility to the disease is much less than the ordi 
nary period of incubation of hydrophobia as produced in man by 
the bite of a rabid animal; consequently, if too long a time has 
not elapsed after the bite of a rabid dog before treatment is com¬ 
menced, the person or animal may be rendered insusceptible to 
the disease before this period of incubation has elapsed. The 
time that may elapse in the case of the human being bitten by a 
rabid animal before successful treatment may be commenced is 
probably, as a rule, not less than twenty days, and in some cases 
may be considerably more than this, but is perhaps as variable as 
the period of incubation of the disease in different cases in the 
human subject resulting from the bites of rabid dogs, and is de 
pendent upon the same idiosyncrasies of the individuals. 
As to the interpretation of the prophylaxis against rabies, 
Pasteur says that the attenuation in the virulence of the rabic 
