73 
disease whatever has increased or decreased, thus strongly 
suggesting the idea that special means must have been taken 
to encourage its development. 
Thirty years ago it was commonly supposed that small- 
pox occurred much more frequently among children and 
young persons than among adults, and I find that in the 
five years, 1848-52, the first for which we have accurate 
returns, the deaths of males under 5 years of age were 66*5 
per cent, of the total number of deaths at all ages, but in the 
5 years 1869-73 the proportion had fallen to 31*0 per cent. 
For females the numbers were respectively 72'2 and 36T 
per cent. The proportion of deaths at all ages above 5 years 
was therefore more than doubled. But taking the deaths 
between the ages of 25 and 65 the proportion was more than 
trebled in the case of males, and more than quadrupled in 
the case of females ; and taking into account the increase in 
the total mortality at all ages it appears that the death-rate 
of males between the ages of 25 and 65 years was 4*46 times 
greater in 1869-73 than in 1848-52, and of females 5T4 
times greater. These remarkable Tacts seem to indicate that 
this loathsome disease has in some way become yotj much 
modified, and more virulent, or that some cause has been in 
operation which has rendered the adult portion of the popu- 
lation very much more susceptible to its attacks, and it is 
evident therefore that it is now a much more serious evil to 
society than it was 20 or 30 years ago, not only because the 
mortality from it has greatly increased, but also because a 
very much larger proportion of that mortality now falls upon 
the producing classes. In spite of sanitary improvements, 
and the protection supposed to be afiorded by the application 
of a special preventive, the death-rate from it has increased 
at all ages without exception, but more especially at those 
ages when it is most important for the general interests of 
society that life should be saved. 
The general conditions which tend to produce an outbreak 
