234 . ANIMAL FORCES. [ii. 



435. If we would compreliend more distinctly how the 

 nerve-actions of an external impression can resemble all the 

 sentient actions, whether direct or indirect, of its external sen- 

 sation, we must take into consideration that the direct nerve- 

 actions in the part irritated result immediately from the appli- 

 cation of the external impression, and before it can be felt ; to 

 this class the internal impression is not required. With regard 

 to the indirect nerve-actions of external impressions, the matter 

 is as follows : 



436. When an external sensation, either from sympathy or 

 natural deflexions, develops direct sentient actions, or excites 

 incidental sentient actions by means of subordinate concep- 

 tions, imaginations, foreseeings, desires, &c., through other 

 branches of the nerve which has received the external impres- 

 sion, or by means of nerves quite different (131), it is requisite 

 to these series of phenomena, that the external impression be 

 changed into a conceptional internal impression before it can 

 suitabl}^ excite the cerebral origin of the nerve, or be reflected 

 in its course downwards on the other branches or nerves, as 

 an internal impression (123, 124). If the same nerves be 

 suitably excited in the same manner, by a reflexion or turning 

 back of the (External impression, exactly the same phenomena 

 are excited, as if they had resulted from secondary sensational 

 conceptions, foreseeings, desires, &c. 



437. It is thus we comprehend, how it is possible for head- 

 less animals to exhibit on a stimulus being applied (as proved 

 by experiment), the same adapted movements as are produced 

 by sensation, and by the ideas, foreseeings, desires, &c., resulting 

 therefrom ; as when a fly deprived of its head, flies away if 

 irritated, or as when a headless snake quickly withdraws its 

 body from whatever comes in contact with it, or a headless 

 fish strikes the boiling water it is put into with its tail, &c. 



438. It appears really wonderful that a blind external im- 

 pression is so reflected on other nerve-fibrils in its way to the 

 brain, as to produce those movements which the mind produces 

 in virtue of its sensational volitions. The wonder arises, 

 however, from our ignorance of the laws of animal nature, and 

 from our prejudice in concluding that all which results from 

 sensation, can result in no other way. The nerve- actions pro- 

 duced by external impressions, are referred by the mind to 



