. 
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APPENDIX A XLVII 
The transmissibility of certain diseases or predisposition to disease 
had, of course, long occupied the attention of the medical profession, 
but it is only within recent years that the claim has been made that 
it is the duty of society to adopt measures to protect itself against 
that progressive decadence which is the logical outcome of such hered- 
itary transmission. Owing to Galton’s efforts, much attention is now 
being attracted to Eugenics in England and on the continent of Europe. 
The necessity for this is amply proved by the conditions observable 
in the slum populations of great cities and elsewhere. The causes of 
these are several: 
1. It has been shown recently by Mr. David Heron that twenty 
five per cent. of the married population of London is responsible for 
fifty per cent. of the next generation and that the twenty-five per cent. 
in question forms the lowest stratum of society—the least valuable 
element of the population, with an enormous contingent of notorious 
drunkards, incorrigible criminals and tuberculous and mentally defec- 
tive subjects. 
Now statistics from other sources show that the birth-rate among 
such unfit elements of the population is higher than the normal. 
2. The above phenomenon is accompanied by another of equal 
importance, namely, the decreasing birth-rate of the higher classes, 
where the hygienic conditions are the most favorable and the physical 
and psychical most desirable. It is easy to see, in view of these facts, 
what disastrous consequences must result from the transmissibility 
of the defective constitutions above referred to. 
3. À third factor in this decadence which one almost hesitates 
to allude to, is the elimination of natural selection, which would other- 
wise remove the unfit in the struggle for existence, by the development 
of means for improving their conditions, philanthropic schemes of 
various kinds, improvements in modern hygiene and the progress of 
medical science. By these various methods individuals are preserved 
up till the period of reproduction who otherwise would have succumbed 
at an earlier period and are thus able to transmit their defective qualities 
to their progeny. 
Eugenics does not seek to interfere with the development of 
proper channels of philanthropy, or the progress of hygiene and medicine, 
for an unfavourable environment is apt to eliminate the fit as well as 
the unfit, but seeks to find remedies for existing evils by applying 
scientifically ascertained facts of heredity to Man, in Galton’s own 
words, “to study the agencies under social control that may improve 
or impair the racial qualities of future generations, physically and 
mentally.” It is therefore intended to have a direct bearing on prac- 
tical life and legislation. Professor Karl Pearson in a recent: lecture 
