HEREDITY IN THE CASE OF DEMENTIA PRÆCOX AND RELATED DISEASES 115 
however little we know about it, the picture of the disease in its en- 
tirety is sufficiently clear to justify us in treating it as a manifestation 
of a degenerative process in the central organ, which may show itself 
at different periods of life and may be modified by different outer and 
inner causes. This degenerative process may almost be considered as 
a too early cessation of the normal functions in a certain part of the 
central organ, and in so far the title Dementia precox is so fitting that 
it deserves to be retained. In other diseases, when the normal functions 
cease too soon in other parts of the central organ, this may occur with 
or without disturbance of the mental balance and in several of these 
diseases we can even detect a destructive process with varying localisa- 
tion. These so-called abiotrophisms doubtless have different causes, 
but the most obvious seems to be an inherited, diminished vitality in 
the part concerned of the organ. In favour of this view at any rate 
we have the fact, that such diseases are very often inherited; naturally 
however this does not exclude the possibility, that a similar functional 
or somatic destruction with the same or similar manifestations may 
arise from quite other causes. That Dementia præcox depends upon 
such an abiotrophic process, is only a supposition, but its mode of 
appearance and the course it follows point in this direction. The de- 
structive process is essentially functional and the somatic indications in 
any case are not specially well-marked. Not rarely the disease appears 
so suddenly and takes such a violent course, that it must be considered 
to arise from a purely chance disturbance of the nutritive conditions 
of the organ and not from any abiotrophism; and this is one of the 
reasons why the inheritance of the disease is so irregular and difficult 
to determine. In general however, there is a well-defined, inherited dis- 
ease, arising insidiously and usually in youth. On the other hand, 
there seems no doubt that it is identical with quite similar diseases 
which appear very late or very early, as Dementia senilis or puerilis, 
or may even be inborn. 
Dementia præcox is inherited in such an irregular manner, that in 
any case it cannot be regarded as a simple monohybrid, recessive or 
dominant character. This is not unusual however. The great propor- 
tion of the inherited diseases are such complicated phenomena, we can 
hardly imagine that they are based on a single factor, but as experi- 
mentation is excluded and as a sufficiently large and reliable material 
can be obtained only with great difficulty, the genetic analysis is not 
easy. It is not sufficient to know, how many sound brothers and 
sisters a certain number of diseased persons may have and from these 
