F. W. Mott.Medicine and Eugenics.425
Fig. 18 Fig. 19
Fig. 18 shows the curves of uncles and aunts and nephews and nieces constructed from the
percentages in Table II. Fig. 19 shows the curves of uncles and aunts and nephews and
nieces, including those cases where one of the parents was also insane, so that there is direct
and collateral heredity. It will be observed that there is a considerable difference in the
offspring curves. When there is only collateral heredity there are a far larger number of
offspring ir which the first attack occurred in the later periods of life. There is antedating,
but it is not nearly so marked as is shown in Fig. 19; nor is it nearly so marked as in parents and
ottspring, Figs. 16 and 17. These figures are constructed from the data contained in Table II.
This tendency of certain diseases to occur at an earlier age in the off-
fpring of diseased parents was termed by Darwin “ antedating ” or
“anticipation,” and I have found, as the above statistics show, that
there is a singular tendency in the insane offspring of insane
parents for the insanity to occur at an earlier age and in a more intense
form, either as congenital imbecility or the primary dementia of adolescence,
an incurable disease; not that all the cases are of this nature, but a large
proportion of them. First let me call attention to certain facts regarding
the age at first attack in 508 pairs of parents and offspring. Some of the
parents had more than one insane offspring; there were only 464 parents.
You will observe that 47 ‘8% of the 500 offspring had their first attack
at or before the age of 25 years, and as you see in the curves of parents
