io6 



SEX AND HEREDITY 



divided his material into males and females, treating the 

 sexes separately. Table 2 gives the results for the male 

 pedigrees, i.e. fathers and sons. The female pedigrees 

 gave similar results. 



TABLE 2. Inheritance of Insanity. Correlation = -6. 



First, let us take the first number (both father and son 

 sane) under " numbers actually found." It is clear that no 

 lunatic asylum records will be able to furnish this figure, 

 since it is only families of which at least one member is 

 insane that come within the ken of such an institution. 

 Nevertheless it is of the utmost importance to discover 

 this figure if we wish to get a true measure of the inherit- 

 ance of insanity, and it can be calculated from the known 

 percentage of insane in the general population. The 

 number of certified lunatics in Scotland on ist January, 

 1901, was 15,475 or -6 per cent. This, however, only 

 gives those certified insane on the date in question, and 

 takes no account of those who have been insane at some 

 period of their lives and subsequently discharged as 

 ' cured/' It is reckoned that the percentage of the 

 population which is or has been at some time or other 

 certified as insane is about 1-5 per cent. On this basis 

 it is easy to calculate the figure 26,774 to correspond on 



