INHERITANCE OF MENTAL DEFECTS AND DISEASE 59 



namely, the so-called process of "antedating" or "anticipation." 

 "I 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." 



If 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, 

 191 2) 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 



