INHERITANCE OF MENTAL DEFECTS AND DISEASE 59 
namely, the so-called process of ‘‘antedating” or ‘‘anticipation.” 
“T have found,” he says, ‘‘that there is a signal tendency in the 
insane offspring of insane parents for the insanity to occur at 
an earlier age and in a more intense form in a large proportion 
of cases; for the form of insanity is usually either congenital 
imbecility or the primary dementia of adolescence, which gen- 
erally is an incurable disease.” The consequence of this alleged 
tendency is that, with increasing age, the offspring of insane 
parents become less liable to insanity. ‘‘Besides the fact,” 
continues Dr. Mott, ‘that this shows Nature’s method of elimi- 
nating unsound elements of a stock, it has another important 
bearing, for it shows that after the age of twenty-five there is a 
greatly decreasing liability of the offspring of insane parents to 
become insane, and therefore on the question of advising marriage 
of the offspring of an insane parent this is of great importance. 
Sir George Savage recently said in his presidential address that 
this statistical proof of mine accorded with his own experience, 
and that if an individual who had such an hereditary taint had 
passed the age of twenty-five, and never previously shown any 
signs, he would probably be free, and he would offer no objection 
to marriage.” 
Tf on the basis of the principle of anticipation advice is to be 
given on the subject of marriage, it is well to be assured that 
the principle rests upon a firm foundation. Dr. Mott arrived at 
his conclusion in the following way: He examined the age at the 
time of the first attack of insanity of 508 pairs of parents and off- 
spring. In 47.8 per cent of the offspring the first attack occurred 
before the age of twenty-five. ‘‘In 299, or 58.8 per cent, of the 
508 pairs of insane parents and offspring, the first attack in the 
offspring occurred at an age twenty or more years earlier than 
in the parents; of these 299 instances 73 of the offspring were 
imbeciles.”’ 
Professor Karl Pearson in a letter written to Nature (Nov. 21, 
1912) showed that Mott’s principle of anticipation involved a 
statistical fallacy. It was pointed out that a man or woman who 
develops insanity at an early age is not so likely to become a 
