32 VOLUNTARY MOTIONS. SECT. IX. 2. i. 



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 recolleiion, like the rnufcular motions above 

 mentioned, were originally excited by the irritation of external 

 bodies, and were termed ideas of perception ; afterwards the 

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

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

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

 imagination. At length they become voluntarily pradlifed in 

 fucceffion or in combination for the common purpofes of life ; as 

 when we make ourfelves matters of the hiilory of mankind, or of 

 the fciences they have inveitigated ; and are then called ideas of 

 recollection ; and are performed with ftrcngth and velocity in 

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

 the quantity of feriforial power. 



II. i. The mufcular motions above defcribedj that are mod 

 frequently obedient to the will, are neverthelefs occasionally 

 caufable by painful or pleafurable fenfation, as in the ftarting 

 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 moil 

 frequently connected with volition, are neverthelefs occafionally 

 cauiable by painful or pleafurable fenfation. As the hiftories 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 fubfervienl 

 to volition, are alfo occafionally caufable by irritation, as in 

 ftretching 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 morion of the arm produces 

 a difagreeabie fenfation in the joint, but the mufcles feem to be 

 brought into action {imply by irritation. 



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

 in like manner occafionally excited by irritation ; as when we 

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

 recollected. 



IV. i. Innumerable trains or tribes of motions are aflbciated 

 with thefe voluntary mufcular motions above mentioned ; as 

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

 mufcles are brought into action, and preferve the balance of my 

 body. And when I wifh to perform any iteady exertion, as ia 



threading 



