Memoirs of Erasmus Darwin, M.D. 309 



pain frorrr want of stimulus ; yet that the organs of sense, as 

 the eye and ear, receive no pain from defect of stimulus. 



Hence it follows, that the constitutions most liable to 

 convulsion, are those which most readily become torpid iu 

 some part of the system, that is, which possess less irrita- 

 bility ; and that those most liable to insanity, are such as 

 have excess of sensibility; and lastly, that these two cir- 

 cumstances generally exist in the same constitution-; These 

 observations explain why epilepsy and insanity frequently 

 succeed or reciprocate with each other, and why iuirri tabid 

 habits, as scrophulous ones, are liable to insanity, of which 

 I have known some instances. 



In many cases, however, there is no appearance of the dis- 

 position to epilepsy or insanity of the parent being trans- 

 mitted to the progeny. First, where the insanity has arisen 

 from some violent disappointment, and not from intem- 

 perance in the use of spirituous liquors. Secondly, where 

 the parent has acquired the insanity or epilepsy by habits of 

 intoxication after the procreation of his children. Which 

 habits I suppose to be the general cause of the disposition to 

 insanity in this country, 



As the disposition to gout, dropsy, epilepsy, and insanity, 

 appears to he produced by the intemperate use of spirituous 

 potation, and is in all of them hereditary; it seems probable, 

 that this disposition gradually increases from generation to 

 generation, in those families which continue for many ge- 

 nerations to be intemperate in this respect ; till at length 

 these diseases are produced ; that is, the irritability of the 

 system gradually is decreased by this powerful stimulus, and 

 the sensibility at the same time increased. This disposition 

 is communicated to the progeny, and becomes still increas- 

 ed, if the same stimulus be continued, and so on by a third 

 and fourth generation ; which accounts for the appearance 

 of epilepsy in the children of some families, where it was 

 never known before to have existed, and could not be 

 ascribed to their own intemperance. A parity of reasoning 

 shows, that a few sober generations may gradually in the 

 same manner restore a due degree of irritability to the family, 

 and decrease the excess of sensibility. 



U 3 From 



