280 ANIMAL FORCES. [ii. 



devoid of cerebral forces, and so constituted that the impressions 

 made on their nerves, are communicated to the mechanical ma- 

 chines, as they are when felt, or produced by spontaneous sensa- 

 tional conceptions, these animals can perform all the sentient 

 actions of pleasurable or painful sensations, imaginations, fore- 

 seeings, &c. (437 — 439); and the actions themselves vj^ill have 

 all the favorable or unfavorable influence on the economy, which 

 they would have had if they had been true sentient actions. 



550. The efiPort of the conceptive force, arising out of the 

 pleasurableness or painfulness of sensational foreseeings, is 

 termed desire or aversion (81, 89); and by it the cerebral forces 

 are strained to develop fully the material idea of a certain fore- 

 seen conception (83). Ail the sentient actions of the sensational 

 desires and aversions are compounded of those of a sensational 

 foreseeing and of its pleasure or pain (255). Now, since all 

 these sentient actions can be caused also by the vis nervosa 

 (549), it follows that the sentient actions of the sensational 

 desires and aversions can be caused in like manner. 



551. The blind instincts and emotions are sensational desires 

 and aversions dififering from the latter only in this, that they 

 manifest a higher degree of intensity, that they are wholly 

 sensational, and that the mind has only an obscure and confused 

 knowlege of their objects (90) ; their sentient actions diff'er also 

 in attaining a high degree of intensity, often bordering on the 

 contra-natural (256). Now, since the vis nervosa can of itself 

 cause the actions of the sensational desires and aversions, it 

 follows, that it can also cause those of the sensational instincts 

 and emotions. 



552. Nature leads animals by means of sensational instincts, 

 to perform the acts necessary to self-preservation and self- 

 defence, to the propagation of the species, and to the care of 

 their young, by means of external impressions which she places 

 in their way at the proper time, if necessary (262 — 265) ; and 

 which impel even rational animals by very obscure sensations 

 to the fulfilment of these duties (266 — -269). Hence it is so 

 much the less surprising, that external impressions so wisely 

 prepared beforehand and produced by nature, can excite the 

 sentient actions of the natural instincts, as nerve-actions ; and 

 attain to and accomplish their object without their being felt, 

 and without the cerebral forces taking any share therein (89). 



