Dementia and general paralysis are the usual, or, at least, the possible termination of all kinds of insanity. Hence their hereditary transmission does not properly constitute a particular case to be considered separately. Sometimes the dementia of progenitors is reproduced in the same form and at about the same age in the descendants. Esquirol saw it appear at the age of twenty-five in a young sculptor, whose family was subject to this disease. At other times the simple insanity of parents is metamorphosed, and becomes dementia or general paralysis in the children. Thus individuals have been seen, born of parents affected with mental diseases, to reach the age of forty or fifty without appreciable signs of mental disease, and then fall into dementia. without any apparent cause, and even contrary to all expectations. In idiots and imbeciles the mental activity has suffered such an arrest of development that some of them adopt the habits of the mere animal. This disease is incurable, since to cure it we should have to create a new brain. As Esquirol ingeniously remarks, the demented subject is a rich man that has become poor; the idiot, a pauper who can never attain to wealth. As the sexual appetite is mostly very keen in idiots, the consequence being an unhappy fertility, it is easy to show the heredity of idiocy. Cases of the direct heredity are numerous. Thus, Esquirol saw at the Salpêtrière an idiot woman, the mother of two daughters and a son, all of them idiots. But idiocy appears to be transmitted rather in the collateral form; or if in the direct line, then it disappears for a generation or two. Haller was the first to note this in the case of two noble families in which idiocy had appeared one hundred years before, and it was found to reappear in the fourth or fifth generation. In our own time, Dr. Séguin, who is a good authority on the question, remarks: 'I have not, to my knowledge, ever had to attend an idiotic son of an idiot, or even the son of a man of weak intellect; but I have often found in the family of one of my pupils an aunt, an uncle, or oftener a grandfather afflicted with idiocy, alienation, or, at least, imbecility.' In conclusion, we could wish that we could answer here two 1 Further facts in Lucas, ii. 787. questions that are unfortunately very obscure. The first is this: What rank must we assign to heredity among the causes of insanity? Good statistical documents alone can afford the answer; but the various tables agree but little with one another. Cases of hereditary insanity are, according to Moreau of Tours, nine-tenths of the whole number; according to other writers they are only one-tenth. According to Maudsley they are more than one-fourth, but less than half: in 50 cases of insanity carefully examined by him, 16 were hereditary, or one-third. In 73 cases given by Trélat in his Folie Lucide, 43 are represented as due to heredity. From a report made to the French Government in 1861, it appears that in 1000 cases of persons of each sex admitted to asylums, 264 males and 266 females had inherited the disorder. Of the 264 males, 128 inherited from the father, 110 from the mother, and 26 from both. Of the 266 females, 100 inherited from the father, 130 from the mother, and 36 from both. Hence we should hardly be in error were we to say that the cases of hereditary insanity represent from one-half to one-third of the total number. The second question is this: To what form of mental heredity must hereditary insanity be referred? In the first place, as regards mere, simple hallucination, it is plain that it is only a form of heredity of the sensorial faculties. As for insanity, properly so called, since it assumes every possible shape; since it presents, now separately, now collectively, perversion of the sentiments and instincts, loss of intellect, and weakness of will; and since it has never been found possible so far to trace back all the psychological phenomena of insanity to one cause, we may affirm that the foregoing facts are a fresh demonstration, in extenso, of psychological heredity under all its forms. |