208 SECTIONAL ADDRESSES. 
This means, to take a concrete example, that the miners who form 
only 8-7 per cent. of the parent class provide 10-7 per cent. of the surviving 
children. The unskilled labourers, the mining and the agricultural 
classes thus appear to be gaining at the expense of the upper and middle 
and the distributing classes. Miners and agriculturists are usually of 
good physique, though from the mental standpoint the change is possibly 
dysgenic. 
There appears to be a general impression that the number of defective 
individuals, particularly of those suffering from mental defect, is greatly 
increasing. There is little evidence on this point of a comparable nature, 
but it may be definitely said that in London no such increase has taken 
place during the last fifteen years. The stocks from which defective 
individuals come are certainly often prolific, but the infant mortality is 
high. Indeed, so far as those individuals who are themselves mentally 
defective are concerned, the figures from institutions indicate death 
rates from ten to twenty times as great as those of the normal population. 
The figures regarding the defectives who have been kept under supervision 
in their own homes indicate rates far above the normal, though perhaps 
less than those in the institutions to which the worst cases naturally drift. 
Contrary also to popular belief mentally defective individuals do not mate 
in nearly as high a proportion as the normal. Out of some 360 defective 
girls who, while remaining outside an institution, have been under super- 
vision during the past ten years and who are of reproductive age, only 
eighteen have married and only seventeen have had illegitimate children, 
a figure which, if regrettably above zero, is not one to cause alarm. Of 
their children a large proportion appear up to the present to be of normal 
capacity. There is some reason for thinking that there is a great inter- 
marriage between defective stocks, and that the actual number of such 
stocks is in reality quite limited. 
The London school service has collected information as to the size of 
the families one member of which has come to notice on account of mental 
deficiency. The figure will naturally appear higher than one derived 
from the census returns, since no knowledge exists concerning childless 
families of the same stocks or of families in which all the children had died. 
The figures are corrected to show only completed families which have been 
taken as those where the mother, at the time of the inquiry, had died or 
had attained the age of forty-five, and, for purposes of comparison, similar 
figures are given for the families of children who had obtained scholarships. 
| - No. of No. of No: of >| 
Group | Pregnancies D nth Surviving 
a of Mother | ~“""* Children 
= 
| Imbeciles and Idiots 6-0 1-7 4:3 
| Children at Schools for the mentally | / 
defective . : 5:3 a) 4-4 
| Scholarship holders . Z j 4-8 5 : 4:3 
As the differential death rate continues to act there is reason to think that 
the defective stock are the less effectively fertile by the time the reproduc- 
tive age is reached. If it be remembered that the factors act still more 
severely against those themselves actually defective, the reason why the 
defective has not overrun the country is evident. Experience in any 
