CH. I.] NERVEACTIONS IN GENERAL. 197 



exactly resembling the sentient actions produced by the ex- 

 ternal impression. 



iii. Hence follows the general principle (361), that those 

 movements in bodies which are most usually nerve-actions, 

 may at another time, or in another animal, be sentient actions, 

 or vice versa; or they may be at the same time both sentient 

 and nerve actions ; in every case being the same movements, 

 but only excited by different stimuli. 



365, i. If a sentient action cannot be also at the same time 

 a nerve-action, no unfelt or non-conceptional impression can 

 cause it as a nerve-action. 



ii. If a nerve- action cannot be also a sentient action, no im- 

 pression, either felt or produced by conceptions, can excite it (362). 



iii. If a sentient action can be also a nerve-action, the im- 

 pression exciting it can act in both ways (364, i, ii). 



366. Since sentient actions and nerve-actions are analogous 

 animal movements from impressions on the nerves, and differ 

 only in this, that in the former the impressions are felt or 

 originate from conceptions, but in the latter not, (193, 364, 

 iii,) it follows that all those movements which in one animal 

 are sentient actions only, or both sentient actions and nerve- 

 actions, may be nerve-actions only in another, excited by im- 

 pressions; so that the external impressions are never felt, and 

 the internal never produced by conceptions, but by other sti- 

 muli ; in this way an animal may not require for all its animal 

 actions, either material ideas, or a sentient brain, or conceptions, 

 or mind. This appears to be the case with those creatures 

 which have no brain, but only nerve-like fibrils, as polypes, in 

 which there is no brain, but the nerves are interwoven in 

 ganglia only. In animals with a sentient brain, every external 

 impression which is felt passes directly to it, and excites therein 

 a material idea, and in the mind a conception (35). Having 

 reached the brain, it is turned iDack or reflected, as it were, and 

 goes back as an internal impression of a conception, into those 

 nerve-fibrils that move the limb, which the external impression 

 is enabled to control by means of a sentient action of its sen- 

 sation (129) .j At the moment of this reflection, when the ex- 

 ternal impression is changed into the internal, thought takes 

 place in the mind, and thereby the movement which the ex- 

 ternal impression excites becomes a sentient action (97)1 When 



