24 PHYSIOLOGY. 



this gives occasion to perception or thought, which, as first aris- 

 ing in the mind, we term SENSATION. This sensation, accord- 

 ing to its various modifications, gives occasion to VOLITION, or 

 the willing of certain ends to be obtained by the motion of cer- 

 tain parts of the body ; and this volition gives occasion to the 

 contraction of muscular fibres, by which the motion of the part 

 required is produced. 



" Metaphysicians have divided the operations of the mind 

 into three parts, viz. perception, intellect, and will ; and if the 

 term thought is applied, it is to the intellect ; but there is no 

 other general term for the whole of these operations but that of 

 thought. Perception is the first beginning of all our mental 

 operations : I say then, that perception or thought, as first aris- 

 ing in the mind, we term sensation. When I was in the gar- 

 den, and perceived a flower, I did so with a perception 

 of its being an object before me; but now that it is re- 

 moved, I can recollect the image of its colour, shape, 

 &c. but that is, at the same time, with an opinion that the ob- 

 ject is not before me now. There are two different conditions, 

 therefore, of the perception of yesterday and of to-day. The 

 whole of perception ha been long spoken of among metaphysi- 

 cians under the general term of idea. It was Mr. Hume who 

 first thought of distinguishing between the first perception aris- 

 ing, and that depending upon recollection or memory : he call- 

 ed the first an impression and the other only an idea ; but the 

 term impression does not convey all we would wish ; I, there- 

 fore, have, with Dr. Haller, employed for a perception as 

 it first arises, what I strictly call sensation ; and recollected per- 

 ceptions I term ideas. This sensation, according to its various 

 modifications, that is, as it is agreeable or disagreeable, gives the 

 one or other mode of volition, desire, or aversion. There are 

 some subtile doctrines insinuated towards the latter part. I 

 do not say that volition wills the contraction of muscular fibres ; 

 we are not conscious of any such thing ; but I say, that volition 

 is the willing of certain ends or purposes to be obtained by the 

 motion of certain parts of the body, as in the example I ad- 

 duced the plucking of a flower, and the bringing it nearer, 

 we attend very often to the motions we employ, but not at all 

 to tfye muscles that perform these," 



