xv

It will be seen that, except in case No. 11, small-pox appeared in no case later than
the 6th day after vaccination. Now the vesicles of vaccination do not ripen till the 8th
day when the protection given by the operation is at its maximum. Besides, small-pox
has an incubation period (that is a period between contracting the disease and the mani-
festation of any symptoms) of from 10 to 14 days. So that in every case the persons
affected must have contracted the disease several days before being vaccinated. They
cannot therefore be quoted as cases of small-pox contracted shortly after successful vac-
cination. Case No. 11 had been vaccinated a year previously, and should have had good
marks to indicate this. But I could only find two very minute ones on one arm which
I was obliged to accept as signs of vaccination, on account of the parents insisting that
they were remains of the vesicles produced in the former year. This was really a case
of bad vaccination, and does not affect the question under consideration.

Besides these cases I saw several cases of undoubted chicken-pox (shákrá shákrá)
measles (sobhra) and even one case of scabies (khárish), which had been mistaken
for small-pox. But as there was no doubt of these cases I have not entered them
in detail. I am also sorry to state that in some villages I was informed that small-
pox had attacked children after vaccination, but when I made investigations I found
that there was no foundation at all for the statement. It therefore behoves us to in-
vestigate every case, where such statements are made, before accepting them as facts, and
to remember that there are these three sources of error :—

(1). The person affected may have contracted the disease before he was vac-
cinated.

(2). The disease appearing after vaccination may not be small-pox, but some
other disease like it.

(3). The rumour may have no foundation, and has been spread by persons
adverse to vaccination, simply to bring the operation into discredit.

There is another source of fallacy : a child may have been vaccinated, but not success-
fully, in which case it would be in the same position as an unvaccinated child. I may
therefore state that I have not come across a single definite case of small-pox appearing
in a person shortly after successful vaccination.

I do not wish to convey the impression from these remarks that small-pox never
attacks children soon after vaccination. If people can occasionally have small-pox twice,
and even thrice, as Bristowe states, it is not surprising that vaccinia, which is a very much
milder complaint, should sometimes be insufficient to protect against the severer disease.
But I do say, from the fact that I have searched several districts for such cases at a time
when small-pox was epidemic and very severe, and was unable to find a single case of this
kind, that small-pox very rarely indeed attacks people within a year or two of successful
vaccination. All the districts in which I searched have used buffalo calf lymph exclusively
since 1890, so, I think, we may admit that, at least, at first, buffalo lymph is practically
as good as cow lymph.