81 
tlie measures hitherto adopted have entirely failed to pro- 
duce any improvement of the public health. 
The results which I have now laid before the Society, 
though perhaps not so full and complete as might be desired 
are, it seems to me, quite sufficient to iustify the following 
conclusions : — 
1. — That sanitary measures, tested by their effect on the 
diseases which are universally admitted to be infectious, 
have produced a, slight improvement in the public health 
which is equivalent to a saving of 1 life in every 134, or a 
reduction of 0T7 in the general death-rate ; but tested by 
their effect on the whole class of zymotic diseases they have 
caused no improvement whatever, and have not even pre- 
vented an increase in the mortality from these diseases 
which is equivalent to an extra loss of life in every 417. 
2. — Considering the great increase in the fatality of small- 
pox when that from all other infectious diseases has di- 
minished, tliat it has now become relatively much more 
prevalent among adults than at any time since vaccination 
was introduced ; that the experience of the last and of the 
present epidemic has furnished abundant proof that vacci- 
nation does not now, as it did in Tenner’s time, and for 
many years after, afford an almost certain protection against 
its attacks ; and that the question of the probability of its 
gradually becoming greatly modified and producing results 
that may be seriously unfavourable to the public health has, 
apparently, never been considered and investigated, it is 
desirable that an authoritative inquiry into the whole sub- 
ject should be at once set on foot in order to ascertain, if 
possible, why vaccination has now become so much less effi- 
cacious as a preventive of smallpox than it was for many 
years after its general adoption ; what has been the true 
cause of the great increase ot smallpox during the last 15 
to 20 years ; and why adults have become so much more 
liable to its attacks ? 
