130 Heredity. 



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 meta- 

 morphosed, 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 conse- 

 quence 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 Salpetriere an idiot woman, the mother of two 

 daughters and a son, all of them idiots. 1 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. Seguin, 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. 



