1 20 Heredity. 



If we restrict ourselves to palpable, visible, demonstrated, and 

 accepted facts, we meet with two sorts of cases : those in which 

 disorders of the intellect have corresponding to them evident 

 changes of the tissue of the nerve-centres, and those in which the 

 brain presents no appreciable degeneration. 



Taking their stand on facts of the second of these categories, 

 some writers on insanity, of whom the most celebrated is Leuret, 

 have held that insanity may proceed from purely psychological 

 causes. ' Physiology,' says he, ' pathology, acquaintance with the 

 facts and the laws of thought and of passion, clinical and micro- 

 scopic observations, therapeutical experiments all concur to 

 negative the absolute proposition that insanity always and 

 necessarily has its rise in an affection of the organs. While 

 everything contributes to bestow the character of evidence upon 

 the following definition of insanity : ' Insanity consists in the 

 aberration of the understanding . . . and the causes that produce 

 it mostly belong to an order of phenomena that have nothing to 

 do with the laws of matter.' Notwithstanding these categorical 

 affirmations, Leuret's view finds daily fewer adherents. The 

 reason of this is, that it really rests only on our ignorance and 

 impotence. It simply affirms that in many cases there exists no 

 physical cause, since we discern none. But beyond the limits 

 that cannot be passed by the microscope, there exist phenomena 

 which, though inappreciable to our senses, are nevertheless 

 material. Electricity, magnetism, and all the various physical 

 and chemical agencies, produce in our inmost organs molecular 

 changes which elude our methods of investigation, but of which 

 the consequences may be fatal. Moreover, the idea of a mental 

 disease independent of all organic cause is a theory so unintel- 

 ligible that the Spiritualists themselves have rejected it, and it is 

 now generally admitted that the cause of madness is always to be 

 found in a diseased state of the organs : insanity, like other 

 maladies, is a disease physical in its cause, though mental as 

 regards most of its symptoms. 1 



1 See Lemoine, VAliene, p. 105137. The hypothesis of purely psycho- 

 logical causes of insanity led Heinroth to pen the following absurdities which 

 are worth quoting : 



' Insanity is the loss of moral freedom ; it never depends on a physical cause ; 



