226 
EXTRACTS. 
the bite of a rabid animal, or differing only in that the period of 
incubation between the inoculation and the characteristic symp¬ 
toms of rabies may be altered. The rabies thus transmitted by 
inoculation may, by similar inoculations, be transmitted through 
a succession of rabbits with marked increase of intensity. But 
the virus in the spinal cord of rabbits that have died of inoculated 
rabies may be gradually attenuated by drying the cords, so that 
after a certain number of days’ drying it may be injected into 
healthy rabbits or other animals without any danger of producing 
rabies; and by using on each successive day the virus dried dur¬ 
ing a period shorter than that used on the previous day an animal 
may be made almost certainly secure against rabies, whether 
from a bite or from any method of subcutaneous inoculation; and 
this protection is proved by the fact that, if animals so protected 
and others not thus protected be bitten by the same rabid animal, 
none of the first set will die of rabies, and, with rare exceptions, 
all of the second set will succumb. 
“ It may hence be deemed certain that M. Pasteur has dis¬ 
covered a method of protection from rabies comparable with that 
which vaccination affords against infection from small-pox. It 
would be difficult to over-estimate the importance of the discovery, 
whether for its practical utility or for its application in general 
pathology. It shows a new method of inoculation, or, as M. Pas¬ 
teur sometimes calls it, of vaccination, the like of which it may 
become possible to employ for protection of both men and domes¬ 
tic animals against others of the most intense kind of virus. The 
duration of the immunity conferred by inoculation is not yet de¬ 
termined ; but during the two years that have passed since it was 
first proved there have been no indications of its being limited. 
The preventive treatment by M. Pasteur is based on the foregoing 
experience; but the determination of the success of the method is 
far from easy, owing to (1) the difficulty in determining whether 
the bites were really those of rabid animals; (2) the probability 
of hydrophobia in persons bitten by dogs that were certainly 
rabid depending very much on the number and character of the 
bites, whether they were on exposed parts or parts protected by 
clothing; and in all cases in the amount of bleeding; (3) in all 
