394 DISEASES CLASS IV. 1. 3. 3. 



the ear. To practise daily by a looking-glass to stop the motions 

 with the hand. See the cure of a case of the leaping of a muscle 

 of the arm, Sect. XVII. 1. 8. See Convulsio debilis. Class III. 

 1. 1. 5. Frequent electric sparks, or very slight shocks. 



3. Risus invitus. Involuntary laughter. When the pleasure 

 arising from new combinations of words and ideas, as in puns; or 

 of other circumstances, which are so trivial, as to induce no vo- 

 luntary exertion to compare or consider their present importance 

 or their future consequence; the pleasure is liable to rise into 

 pain; that is, the ideas or sensual motions become exerted too 

 violently for want of some antithesistic ideas; in the same manner 

 as those muscles which have weak antagonists, as those of the calf 

 of the leg, are liable to fall into cramp or painful contraction. In 

 this situation, a scream is begun to relieve this pain of ideas too 

 violently exerted, which is stopped again soon, as explained in 

 Sect. XXXIV. 1. 4. and Class III. 1. 1. 4. and IV. 2. 3. 3. 



The pain into which this pleasure rises, which would excite the 

 scream of laughter, has been felt forcibly by every one; when 

 they have been under such circumstances, as have induced them 

 to restrain it by a counter- volition; till at length the increased 

 associate motions produce so much pain as to overcome the coun- 

 ter-volition, and the patient bursts out into indecent laughter, con- 

 trary to his will in the common acceptation of that word. 



4. Lusus digitorum invitus. An awkward playing with the 

 fingers in speaking in public. These habits are begun through 

 bashfulness, and seem rather at first designed to engage the at- 

 tention in part, and thus prevent the disagreeable ideas of mau- 

 vaise honte; as timorous boys whistle, when they are obliged to 

 walk in the dark; and as it is sometimes necessary to employ 

 raw soldiers in perpetual manoeuvres, as they advance to the first 

 charge. 



5. Unguium morsiuncula invita. Biting the nails is a depraved 

 habit, arising from similar causes as those of the last article. 



M. M. Dip the fingers in solution of aloes. 



6. Vigilia invita. Watchfulness, where the person wishes 

 and endeavours to fall asleep, properly belongs to this place, as 

 the wish or volition to sleep prevents the desired effect; because 

 sleep consists in an abolition of volition. See Class III. 1. 2. 3. 



