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occurred amongst each 40 of un-vaccinated persons. In an epidemic of small-pox that
occurred in another city, where the number of vaccinated and un-vaccinated
was known, it was found that while only 66 per cent. of the vaccinated took the
disease, as many as 50 per cent. of the un-vaccinated took it. I merely mention
these as two examples of the truth I am dwelling upon. If, then, I am asked why
any vaccinated persons suffer at all on exposure? I reply, 1st: that the occurrence in
a very small proportion of instances depends upon an exceptional proclivity on the
part of some individuals to take the disease: such persons will suffer small-pox even
after inoculation, or after having had. the disease a greater or less number of years
previously. Such as these, even one attack of small-pox will not protect against a
second, or even a third, much less can vaccination (which is merely small-pox
modified by passing through the constitution of the cow) protect. 2nd: that about
the age when adult age is attained there happens, from constitutional causes, a
remarkable tendency to take small-pox, both on the part of the vaccinated and the
un-vaccinated, who may hitherto have escaped attack, but even at this age vaccinated
persons are comparatively protected by the vaccination they have undergone. 3rd:
that besides this, the protection of vaccination given in infancy gradually wears out
as age advances, and hence that an unknown proportion of such individuals are
endangered. It is on this ground, as well as on that last mentioned, that I have
from time to time urged in my monthly reports the necessity for having recourse to
re-vaccination, and in periods of epidemic outbreaks have pressed upon our district
vaccinators the desirableness of offering to adults in small-pox localities the renewal
of their protection. 4th: that a great deal of the vaccination performed now a days
is of a very imperfect character; partly this is the fault of the operator not being
careful in the selection of the pocks from which he takes the virus, or in using
preserved or dry virus in place of vaccinating from arm to arm. But there is an
additional cause in the now indisputable fact, that the virus which has passed through
some hundreds or thousands of human systems since it left the cow, has undergone
in such transmission and repeated human generation, a degradation in its character
and force. The vaccine disease, as produced by most practitioners now by arm to
arm vaccination, is a much less virulent disease than it was when firBt inoculated by
Dr. Jenner, or that it has proved itself where new sources have been opened on the
occasional discovery of natural cases of cow-pox. Jenner contented himself with a
single puncture with such virus, and was even then alarmed, although needlessly, at
the local result produced; others, under similar circumstances, have contented themselves
with two, whereas for the production of a satisfactory result with the virus
mostly in use here, four or eight punctures are needed, and even then a less amount
of constitutional disturbance follows the operation. Yet we find on examining the arms
of vaccinated children, in place of scars which may be seen half across a long room,
marks so poor and superficial left by the vaccination that close inspection may be
needed to see them at all, and in place of four to eight pocks, possibly only one or two
paltry vesicles raised by the operation. Can it bo wondered at then that the