Sect. III.] Theor}/ aiid Practice of Phijsic. S3C; 



desire or aversion, occasioned by fibrous motions, 

 which liad been previously i)rodu(( d by tbe senso- 

 rial power of sensation. That of association is at 

 first eixerted in consequence of tlie stinuihis of 

 fibrous motions, previously occasioned by irrita- 

 tion, sensation, or volition. 



Having thus stated the various modes of action 

 of the sensorial power. Dr. Darwin proceeds to de- 

 liver the other fundamental principles of his theory. 



During the application of any of the above-men- 

 tioned stimuli, the sensorial power becomes ex- 

 hausted; on the contraiy, while any of them an* 

 withdrawn, it becomes accumulated. 



In order to illustrate and establisli his important 

 doctrine of association. Dr. Darwin asserts that 

 there are various circles of associate motions in the 

 animal system, which may take their names Ironi 

 that faculty of the sensorial power by which they 

 are introduced. Those circles, for example, which 

 are introduced by an irritative motion, may be 

 termed irritative associate motions ; and, in like 

 manner, the sensitive and voluntary associate mo- 

 tions are produced and denominated. All these 

 several circles of motions act upon one another by 

 means of the sensorial power of association.; they 

 may be affected by other sensorial motions, such 

 as those of irritation, sensation, and volition ; and 

 they may be considered as compounded, each one* 

 of smaller circles ; as, for instance, tiie great circle 

 of irritative associate motions may be sup|)ose(l to 

 be made up of smaller circles of the same kind. 



Conformably to this scheme of association, tin 

 introductory link of any circle of associate motions 

 may have its action increased, diniiiiislied, or ^u^- 



Z 2 



