364 Recent Studies of the Inheritance Factor in Insanity 
become insane, and this introduces further spurious anticipation. Another hypo- 
thetical example will perhaps make this clear. Let us take the case of a mother 
with six children, five of whom have become insane as follows : 
TABLE III. 
Mother 
Children 
1 
2 
3 
5 
6 
Born 
1830 
1850 
1852 
1854 
1856 
1858 
1860 
Became Insane 
1860 
1872 
1896 
1914 
1888 
18601 
Age at Onset of Insanity 
30 
-* 
20 
42 
58 
30 
0 
The extent to which this family would show anticipation or antedating 
would depend very largely on the time at which the record was made as is shown 
in the following table. 
TABLE IV. 
Age of Onset of Insanity in 
■ 
Date of 
Average for 
Amount of 
Record 
Children 
Anticipation 
Mother 
Cbildreu 
1860 
30 
0 
0 
30 
1872 
30 
0, 20 
10 
20 
1888 
30 
0, 20, 30 
16-7 
13-3 
1896 
30 
0, 20, 30, 42 
23 0 
7 
1914 
30 
0, 20, 30, 42, 58 
30 
0 
If the case were noted in 1860 then the age of onset of insanity in the mother 
is 30 years — of the child 0 years — a clear case of anticipation, and nothing 
would be known of the fact that four other children will afterwards become insane 
and will bring the average age of onset in the children up to SO years — exactly 
the same as that of the mother. Nor is the record even now complete for if the 
eldest child ever becomes insane, the age of onset in his case must be at least 
64 years and this will further increase the average age of onset in the children. 
It is thus clear that in dealing with incomplete families and ignoring the possi- 
bility that those who are normal at the time of record may afterwards become 
insane, Dr Mott has introduced a further spurious anticipation or antedating. 
If we examine carefully the first pedigree given by Dr Mott at the Eugenics 
Congressj, we see clearly how probably much of the anticipation recorded by 
* Alive, 64 years of age and still normal. 
t Congenital Idiot. 
% Problems in Eugenics, p. 413. 
