MORBID HEREDITY. 389 



same probabilities of degeneration as morbid consanguinity. It 

 appears with nervous, hysterical, and veneric persons, and with 

 criminals, among whom vice becomes the basis of unions leading 

 to progressive degeneracy. 



Some infectious diseases, usually propagated by contagion, may 

 be transmitted to the child by the mother, or even by the father, 

 while the mother remains free from them. The disease being due 

 to a special agent of infection, that is, to a being with an existence 

 of its own, such transmission can not, properly speaking, be re- 

 garded as a fact of heredity. The generative agents have served 

 only as vehicles for the morbid agent or its products. What has 

 been transmitted is not a natural characteristic, or even a defi- 

 nitely acquired characteristic, but a strange and accidentally im- 

 posed property, susceptible of disappearing or of being destroyed. 

 Transmission of this kind does not correspond with the definition 

 of biological heredity. Direct heredity of certain diseases has 

 attracted the attention of observers of all times, and has been 

 most regularly noticed in mental diseases. 



The family defect is very often exhibited gradually. One or 

 more generations manifest slight troubles, which we might call 

 preparatory. Heredity has to be accumulated, capitalized, as it 

 were, before displaying itself as a morbid entity to which we can 

 give a name. We often find individuals among the ancestors of 

 insane persons, individuals subject to overexcitement, enthusiasts, 

 originals, unfortunate inventors, dissipated persons, or men of 

 irregular life or afflicted with mental or moral eccentricities. 



Heredity is not manifested in the same degree in all the forms 

 of madness, and is less evident in the acute than in the chronic 

 forms. Mental troubles generally are most likely to transmit 

 themselves by heredity when they are active at the moment of 

 conception. They are less surely transmissible if their activity 

 in the progenitors is suspended at the time, and especially if the 

 first attack does not come on till after the birth of the child. The 

 fact that we occasionally see a person who has not yet been insane 

 transmit the predisposition to become so to his descendants dem- 

 onstrates that it is not the disease itself, but the aptitude to acquire 

 it that is transmitted. Accumulated heredity often results in the 

 production of individuals distinguished by physical malformations 

 or by abnormal emotionalisms, constituting what are called the 

 physical and the psychical stigmata of degeneracy. Yet we can 

 not say that heredity impresses special characteristics on mad- 

 ness. But persons inheriting morbid tendencies are more sensi- 

 tive to excitement of every kind, and more frequently suffer acute 

 irritations under the influence of insignificant causes, while most 

 usually these irritations disappear as easily and as abruptly as 

 they came on. 



