HEREDITY IN THE CASE OF DEMENTIA PRÆCOX AND RELATED DISEASES 123 
further, a number of likewise heritable forms of Paranoia, which occur 
along with the two others and which may be considered to depend on 
similar special factors in combination with the same common factor. 
As an extremely fine example, among many others, I may note a case 
of typical Dementia præcox in a man of sound parents, but the 
father had a sister with paranoia and the mother a sister with manio- 
depressive psychosis, in addition to some more remote relatives with 
the one of the other of these diseases or with lighter mental defects. 
Excluding the last and using D to indicate the specific factor for 
Paranoia, the genetic formula here may have been: 
AaBbccDd X AaBbCcdd = AaBBccdd +. . . 
There is no reason however to deal specially with this disease; its 
relations in every way are the same as the manio-depressive psychosis 
and Dementia præcox. None of these occur in such a manner as to 
_ suggest more complicated conditions of heredity. None of them is 
specially connected with the one or the other sex, and there is nothing 
to indicate that the factors conditioning them attract or repel each 
other, and the same is the case with the other diseases mentioned 
above and related to Dementia præcox. On the other hand, in these 
families we find a number of heritable defects or deformities of a 
special kind, the causes of which are as yet but little known, but 
which in any case are only in part inherited according to the Men- 
delian laws. Such are the stigmata hereditatis often mentioned in the 
older teaching; they were supposed te be specially frequent in the 
so-called degenerated families and were thus taken as a sign of de- 
generation, but they do not stand in any obvious, genetic relation to 
the heritable mental defects. Nor has it been determined that these 
diseases really occur more frequently in families with heritable mental 
disease than in others, and in any case they are so diverse in their 
nature that they must of necessity have a different origin. There can 
be no question here cf entering into a ‘detailed discussion of this 
extensive subject, but it may just be noted as an example, that in the 
family mentioned above (p. 118) with two cases of Dementia præcox 
in cousins and nine cases of chronic alcoholism in the antecedents one 
boy was an imbecile with cleft palate and a sister lacked the fingers 
of the one hand. As this sister is now dead, nothing further is known 
regarding this defect but it probably took its origin in one of the, not 
rare, intrauterine amputations arising from some chord-formation in 
the amnion. The cleft palate of the brother may have come from 
several causes, but it is in any case not excluded that it may have been 
