SPASMODIC AFFECTIONS. 421 



impressions producing an exquisite or high degree either of plea- 

 sure or pain. 



Impressions which produce neither the one nor the other, 

 have hardly any such effects, unless when such impressions are 

 in a violent degree ; and then their operation may be consider- 

 ed as a mode of pain. It is, however, to be remarked, that all 

 strong impressions which are sudden and surprising, or, in other 

 words, unforeseen and unexpected, have frequently the effect of 

 bringing on epileptic fits. " In speaking of impressions, I have 

 considered them as causes of pain. But another impression, 

 quite peculiar in this case, is that of titillation, which is very 

 slight, but being attended with frequent oscillations, has a sin- 

 gular power with regard to our body. Every body knows its 

 power of producing convulsions to a certain degree, and these 

 will even amount to epilepsy : I will not say whether this im- 

 pression is to be referred to the general head of pleasure, but, 

 attending to our theory, it will lead to somewhat of the same 

 doctrine with regard to the irregularity in the succession of mo- 

 tions in our brain." 



MCCXCVIII. There are certain impressions made upon 

 different parts of the body, which, as they often operate with- 

 out producing any sensation, so it is uncertain to what head 

 they belong ; but it is probable that the greater part of them 

 act by excitement, and therefore fall to be mentioned here. The 

 chief instances are, the teething of infants ; worms ; acidity, or 

 other acrimony in the alimentary canal; calculi in the kid- 

 neys (" we have two or three cases of this kind in Lieutaud, 

 where nothing else was found") ; acrid matter in abscesses or 

 ulcers ; or acrimony diffiised in the mass of blood, as in the case 

 of some contagions. " Among the poisons disposing to epi- 

 lepsy, is to be reckoned the smallpox contagion, acting as a stimu- 

 lus. It is rarely of sufficient power, except in infants ; but in these 

 it frequently kills, which it may do merely by the repetition. of 

 epilepsy ; and there is so much hazard of it as to render it im- 

 prudent to throw that poison into young infants by inoculation. 

 That epilepsy is often a symptom of benign smallpox is to be im- 

 puted to this, that it is a proof of a lax and irritable system, 

 not liable therefore to any violent spasm on the surface which 

 may detain the variolous matter in the skin." 



