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course of the foregoing pages I have endeavoured to prove 

 that the brain and nervous system are anatomically, 

 physiologically, and psychologically transmitted by heredity ; 

 in other words that, organically and dynamically, the structure, 

 functions, and powers of the human brain and nervous 

 system are hereditarily transmitted from parents to their 

 children. Of this fact there can be little or no doubt ; but 

 I have now to consider whether this statement is true in a 

 pathological sense, whether in fact the scientific accuracy of 

 the first statement does not involve an affirmative reply to the 

 question : Are the derangements and diseases of the brain 

 and nervous system subject, in like manner, to the law of 

 heredity ? In attempting to answer this question I propose, 

 in the first place, to refer in a few words to those derange- 

 ments or diseases of the brain grouped under the term morbid 

 psychological heredity, and including Hallucination, Mono- 

 mania, Suicide, Mania, Dementia, and Idiocy, and assume 

 that there is no form of mental disease independent of an 

 organic cause, for "since the direct cause of insanity is some 

 morbid affection of the nervous system, and as every part of 

 the organism is transmissible, clearly the heredity of mental 

 affections is the rule." 1 



Esquirol observes, that, of all diseases, insanity is the 

 most hereditary, and reliable statistics prove that it is so to the 

 extent of from thirty-five to fifty per cent. All the forms 

 and varieties of insanity are unquestionably transmissible by 

 heredity, and nothing could be easier than to supply facts 

 and cases in illustration and defence of this statement, but I 

 shall content myself by quoting the following from the 

 graceful pen of Dr. Maudsley concerning the hereditariness 

 of suicide. He says : "It is, indeed, striking and startling 

 iRibot 



