630 
Proceedings of the Royal Society of Edinburgh. [Sess. 
a fact to be expected, as the chief cause of death is in both instances the 
same, namely, broncho-pneumonia. 
2. In this group the evidence is very scanty and not of the highest 
value. The essential condition, namely, the homogeneous population, can 
hardly be attained. For instance, in Glasgow, small-pox draws such a 
large number of its victims from the model lodging-house population, a 
population of inferior resistance and of lower mean ages, that the figures 
for the class mortality at middle ages cannot be compared with those at high 
ages. For this disease the epidemic in Gloucester (5) in 1895-6 has been 
chosen as affording more homogeneous material. With regard to typhus, 
on the other hand, Glasgow, with its large Irish population, among whom 
the disease chiefly spreads, affords more homogeneous material than London. 
When, however, data are selected in this manner their importance is much 
diminished. It is further to be noted that an epidemic attacking a 
practically virgin population may be expected to give better evidence than 
one where the susceptible persons have largely been protected by an attack 
of the disease before they arrived at old age. 
TABLE III. 
Table showing the Increase of Case Mortality in Typhus Fever 
at Ages above 25 Years in Glasgow and London. 
Glasgow, 1865-1871. 
London. 
Age 
Period. 
Cases. 
Deaths. 
Case Mortality. 
Cases. 
Deaths. 
Case Mortality. 
Actual. 
Tlieor. 
Actual. 
Theor. 
25-35 
841 
147 
17-6 
17-7 
3245 
574 
17*6 
17-7 
35-45 
648 
183 
28-3 
26-0 
2965 
842 
28-3 
26-3 
45-55 
309 
127 
41-0 
38-2 
1829 
834 
45-4 
38-2* 
55-65 
107 
57 
53-0 
54-9 
881 
479 
54-4 
54-9 
65-75 
20 
16 
80-0 
82*4 
272 
203 
74-7 
82-4 
* Age when the law does not hold. 
X 2 = 2 P = *74 x 2 = 25-5 P — '0001 
In Table III. a comparison of the death-rate of typhus fever in Glasgow 
(4) and London (6) for the times when that disease was common is given. 
It is to be noted in the first place that at these age periods — 25-35, 35-45, 
and 55-65 — the case mortalities in both cities are practically identical. 
These were therefore taken as a basis, and a geometrical progression fitted 
by the method of least squares. The result for Glasgow is very good, but 
from London far from satisfactory. The error is again almost wholly at 
one age period, 45-55. 
