4JLASS III. 1. I. OF VOLITION. 277 



to 110, when tbey lie down again in their beds. Whence it 

 appears, that when a very quick pulse accompanies convulsion 

 or insanity, it simply indicates the weakness of the patient; that 

 is, that the expenditure of sensorial power is too great for the 

 supply of it. But if the strength of the patient is not previously 

 exhausted, the exertions of the muscles are attended with tem- 

 porary increase of circulation, the reciprocal swellings and elon- 

 gations of their bellies push forwards the arterial blood, and 

 promote the absorption of the venous blood; whence a tempo- 

 rary increase of secretion and of heat, and a stronger pulse. 



A correspondent acquaints me, that he finds difficulty in un- 

 derstanding how the convulsions of the limbs in epilepsy can be 

 induced by voluntary exertions. Tnis I suspect, first to have 

 arisen from the double meaning of the words " involuntary mo- 

 tions;" which are sometimes used for those motions, which are 

 performed without the interference of volition, as the pulsations 

 of the heart and arteries; and at other times for those actions, 

 which occur, where two counter volitions oppose each other, 

 and the stronger prevails; as in endeavouring to suppress laugh- 

 ter, and to stop the shudderings when exposed to cold, Thus 

 when the poet writes, 



video meliora, proboque, 



Deteriora sequor. 



The stronger volition actuates the system, but not without the 

 counteraction of unavailing smaller ones; which constitute .de- 

 liberation. 



A second difficulty may have arisen from the confined use of 

 the words " to will," which in common discourse generally 

 mean to choose after deliberation; and hence our will or voli- 

 tion is supposed to be always in our own power. But the will 

 or voluntary powers, act ahvay from motive, as explained in 

 Sect. XXXIV. 1. and in Class" IV. 1. 3. 2. and III. 2. 1. 12. 

 which motive can frequently be examined previous to action, 

 and balanced against opposite motives, which is called delibera- 

 tion; at other times the motive is so powerful as immediately 

 to excite the seusorial power of volition into action, without a 

 previous balancing of opposite motives, or counter volitions. 

 The former of these volitions is exercised in the common pur- 

 poses of life, and the latter in the exertions of epilepsy and in- 

 sanity. 



It is difficult to think wilhout words, which however all those 

 must do, who discover new truths by reasoning; and still more 

 difficult, when the words in common use deceive us by their 



