We have reviewed the major exaggerations and distortions of personal traits which characterize the psychoses—individual differences due to pathological conditions. But there has been mentioned a group of disorders, the biogenetic, that arise upon constitutional incapacity for mental adaptation to life, and in this aspect do the psychoses represent pathological conditions due to individual differences. Here we see individuals, who, though in early years presenting no such abnormalities as would bring them into the group of feeble-minded, and adapting themselves at least passably well to the situations of childhood, yet, when they meet situations of a certain character in later life, are not able to cope with them as normal individuals, but are precipitated into psychosis.
The fact that these situations are common ones in every-day experience has been held to refute the supposition that they could be the precipitating factor in psychosis. Thus, if a girl, such as I have in mind, develops a brief, dementia-præcox-like episode on the death of an old lover, this would not be an occasion for the psychosis, because thousands of people live through the situation with no abnormal reaction. But this fairly obvious reasoning that the shock could not occasion the psychosis has to yield before the very obvious fact that it does. The truth is rather that in these individuals certain particular shocks would tend to be followed by psychotic reactions, and this girl developed her psychosis because, as further observation indicated, the death of that old lover meant to her something very different from what the corresponding event means to the average person.
Just what mental events will in any given individual be of the character to precipitate a psychosis is a psychogenetic matter, and varies as people's life-histories do. But that they have the property of precipitating one at all, and what kind of psychosis they will precipitate, depends on individual differences of constitution.
The most definite conception has been reached in regard to those mental constitutions on which dementia præcox reactions develop. It has been found by Adolf Meyer, August Hoch, and others who have repeated their observations, that individuals who develop these psychoses tend to be distinguished by a combination of traits which they sum
