304 DISEASES CLASS III. 1. 2. 



There is finally reason to believe, that not only sensorial power 

 in general is capable of accumulation in those parts which have 

 been accustomed to almost perpetual action; but also that each 

 kind or species of sensorial power, as that of irritation, sensation, 

 volition, and association, is separately capable of accumulation 

 in the parts which have almost perpetually been actuated by it; 

 which I hope some time to consider more at large, as I suspect it 

 may supply a key to many of the phenomena not only of insani- 

 ties and convulsions, but to those of fever. 



The disposition to insanity, as well as to convulsion, is believed 

 to be hereditary; and in consequence to be induced in those 

 families from slighter causes than in others. Convulsions have 

 been shewn to have been most frequently induced by pains owing 

 to defect of stimulus, as the shuddering from cold, and not from 

 pains from excess of stimulus, which are generally succeeded by 

 inflammation. But insanities are on the contrary generally in- 

 duced by pains from excess of stimulus, as from the too violent 

 actions of our ideas, as in common anger, which is an insanity of 

 short duration, for insanities generally, though not always, arise 

 from pains of the organs of sense; but convulsions generally, 

 though not always, from pains of the membranes or glands. And 

 it has been previously explained, that though the membranes and 

 glands, as the stomach and skin, receive great pain from 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 convul- 

 sion, are those which most readily become torpid in some part of 

 the system, that is, which possess less irritability; and that those 

 most liable to insanity, are such as have excess of sensibility; 

 and lastly, that these two circumstances generally exist in the 

 same constitution: as explained in Sect. XXXI. 2. on Tempera- 

 ments, These observations explain why epilepsy and insanity 

 frequently succeed or reciprocate with each other, and why in- 

 irritable habits, as scrofulous ones, are liable to insanity, of which 

 I have known some instances. 



In many cases however there is no appearance of the disposi- 

 tion to epilepsy or insanity of the parent being transmitted to the 

 progeny. First, where the insanity has arisen from some violent 

 disappointment, and not from intemperance in the use of spi- 

 rituous liquors. Secondly, where the parent has acquired the 

 insanity or epilepsy by habits of intoxication after the procrea- 

 tion of his children. Which habits I suppose to be the general 

 cause of the disposition to insanity in this country. See Class III. 

 J.I. 7. 



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



