3 2 VOLUNTARY MOTIONS. Sect. IX 2. u 



excited thefe ideas repeatedly, you excite the idea of their differ- 

 ence, which is that of another right-angled triangle inverted 

 over the former ; you are faid to reafon upon this fubject, or 

 to compare your ideas. 



'Thefe ideas of recollection, like the mufcular motions above 

 mentioned, were originally excited by the irritation of external 

 bodies, and were termed ideas of perception : afterwards the 

 pleafure cr pain, that accompanied thefe motions, induced a rep- 

 lion of them in the abfence of the external body, by which 

 they were firft excited ; and then they were termed ideas of 

 imagination. At length they become voluntarily practiced in 

 fucceffion or in combination for the common purpofes of life ; a~. 

 when we make ourfelves mafters of the hiftory of mankind, or of 

 the Sciences they have inveftigated ; and are then called ideas of 

 recollection ; and are performed with Strength and velocity in 

 proportion to the energy of the volition that excites them, and 

 the quantity of fenforial power. 



II. 1. The mufcular motions above defcribed, that are mod 

 frequently obedient to the will, are neverthelefs occasionally 

 caufable by painful or pleafurable fenfation, as in the flarting 

 from fear, and the contraction of the calf of the leg in the 

 cramp. 



2. In like manner the fenfual motions, or ideas, that are mod 

 frequently connected with volition, are neverthelefs occasionally 

 caufable by painful or pleafurable fenfation. As the histories of 

 men, or the defcription of places, which we have voluntarily 

 taken pains to remember, fometimes occur to us in our 

 dreams. 



III. I. The mufcular motions that are generally fubfervient 

 to volition, are alio occasionally caufable by irritation, as in 

 ftrctchlng the limbs after fleep, and yawning. In this manner 

 a contraction of the arm is produced by palling the electric fluid 

 from the Leyden phial along its mufcles ; and that even though 

 the limb is paralytic. The fudden motion of the arm produces 

 a difagreeable fenfation in the joint, but the mufcles feern to be 

 brought into action fimply by irritation. 



2. The ideas, that are generally fubfervient to the will, are 

 in like manner occaiionally excited by irritation ; as when we 

 view again an object, we have before well ftudied, and often 

 recc 1. 



IV. 1. Innumerable trains or tribes of motions are affociated 

 with thefe voluntary mufcular motions above mentioned ; as 

 when I will to extend my arm to a dittant object, fome other 

 trr re brought into action, and preferve the balance of my 

 body. And when I v. ifh to perform any fieady exertion, as in 



threading 



