488 Proceedings of Royal Society of Edinburgh. [sess. 
that in London in the spring of the same year.* The statistics of 
the summer epidemics in London are difficult to deal with, on 
account of the manner in which the death certificates have con- 
founded the ordinary summer diarrhoea with the more deadly 
disease. It is also to be noted that, though the epidemics referred 
to occurred at different seasons of the year, the form in each 
disease is much the same, showing that the infecting agent is more 
Diagram II. 
Plaeue Deaths. 
20.000 
16.000 
12 000 
\ \ 
London, 11 
365 
\ \ 
\\ 
i 
// 
// 
II 
\ 
o nnn 
// 
/ 
// 
// 
// 
/ / 
/ / 
U 
y\ 
\\ 
4,000 
// 
/ / 
/ / 
/ / 
// 
\ 
// 
/ / 
May 30 
June 27 
Jul. 25 
Aug. 22 
Sept. 19 
Oct. 17 
Nov. 14 
Dec 12 
potent in determining the outburst than either season itself or 
seasonal constitutional differences in the population. 
From the large body of figures relating to smallpox, several 
examples have been chosen. For the last two centuries statistics 
of numerous epidemics exist where the number of deaths is re- 
corded for each succeeding week or month of the epidemic, and 
since 1890, when compulsory notification began, the epidemic 
wave can he traced for both cases and deaths. 
* Report of Board of Health upon Epidemic Cholera, 1848-49, plate, 
p. 26. 
