ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
75 
birth of living only one-half as long as those in better-class houses, or they die nearly 
20 years sooner, on the average, than those of the better class. This is an enormous 
difference. If we take the mean age of those who died above 20, we find that a 
similar lowering of the mean age at death likewise occurs in the worse class of houses, 
though not nearly to such a marked degree. It is, in fact, only the strong ones who 
have survived in the 1- and 2-roomed houses, the weaker ones having been mostly cut 
off' before they reach the age of 5 years. The higher mean age at death of those 
who died above 20 years of age in 1-roomed houses, though possibly due partly to 
the fact that a larger proportion of the people living in 1-roomed houses are employed 
in outside labour during the day than is the case with the other classes, is, doubtless, 
chiefly due to a process of natural selection, whereby the weaker ones have been 
taken off earlier in life, so that those who are left are much more able to combat 
circumstances unfavourable to life than are those in 2- and 3-roomed houses, and who 
have not undergone this natural selection to nearly such a great extent.'" The Table 
also shows that in better-class houses persons above 70 are likely to live about a year 
longer than those above 70 years of age in 1- and 2-roomed houses, although the latter 
are to a much greater extent a “ survival of the fittest.” 
(4.) As regards deaths from particular causes, those from phthisis require special 
notice. 
As is well known, and as other statistics t have conclusively proved, the prevalence 
of phthisis is very largely affected by the state of purity of the air. It might have 
been expected, therefore, that the death-rate from phthisis especially would show a 
marked parallelism with differences in the condition of the air, and, consequently, in the 
in 
* Koeosi (see ‘Annales d'Hygiene Publique,’ vol. 14, 1885, p. 571) finds that for the years 1874-1881 
Buda-Pestli the mean age at death was :—- 
Of all who died 
_A_ 
Among the rich . 
,, middle class 
„ poor . . . 
Below 5 years of age. 
1\3 years 
1-2 
1-0 „ 
Above 5 years of age. 
52'0 years 
„ 
4P6 „ 
Or, arranged according to the class of houses, as follows :— 
Of all who died above 5 years of age. 
Best class of houses. 44 - 2 years 
Middle ,, „ . 42‘2 „ 
Worst „ ,, (cellars) . . 39'9 „ 
t See Parkes’ ‘Hygiene,’ 6th edition, page 133 et seq., also page 105, in which a large number of 
facts are adduced, of which the following may serve as examples:— 
Two Austrian prisons, in which the diet and mode of life were, it is believed, essentially the same, 
offer the following contrast:—In the prison of Leopoldstadt, at Vienna, which was very badly ventilated, 
the death-rate in 1834-1847 was 86 per 1,000, and of these no less than 5P4 died from phthisis. 
In the well-ventilated House of Correction in the same city, the death-rate (1850-1854) was only 
14 per 1,000, and of these 7’9 died of phthisis. 
L 2 
