136 ANIMAL-SENTIENT FORCES. [i. 



an animal to think of supplying itself with food, at certain fixed 

 periods the stomach is emptied of all the food taken into it, and 

 from this emptiness an unpleasant external sensation arises, 

 termed hungriness. This is the sensational stimulusofthe instinct 

 of hunger, which is communicated to the mind by means of the 

 emptiness of the stomach naturally and necessarily ; nay, even 

 contrarily to the wish of the animal (27). This unpleasant 

 external sensation reminds it of the contrary pleasant sensation 

 experienced when the stomach was full. From this com- 

 bination arises the foreseeing and expectation (73) of the agree- 

 able sensation of a fall stomach, and the effort of the mind to 

 develop it (81), which is the instinct of hunger, and the con- 

 tentment of which by eating to satiety, is the object nature had in 

 view in exciting the instinct, so as to provide for the nutrition 

 of the animal (262). When an animal has remained motionless 

 for a length of time, the body becomes sickly, because the 

 functions of all organs go on imperfectly. This is the pre- 

 ordained cause of the instinct of muscular activity, because the 

 sickliness excites unpleasant external sensations, which the 

 animal cannot avoid, and which are the sensational stimuh of 

 the instinct. Out of this unpleasant external sensation of the 

 animal, and the recollection of the well-being experienced when 

 the limbs were moved, arise the foreseeing and expectation of 

 the opposite pleasant sensation of a future movement, and thus 

 results an effort — the instinct of movement — the satisfaction of 

 which by bodily exercise is the design of nature, so as to pro- 

 vide for the well-being of the animal. The same mechanism 

 and series of phenomena may be readily traced in the develop- 

 ment of other natural instincts. 



269. In thinking animals, all the sentient instincts, together 

 with the sentient actions that accompany them, are thus 

 developed, although obscurely enough, from the natural in- 

 ducements pre-ordained by the Creator, according to the laws 

 of the conceptive force and of the animal sentient forces; but 

 only on the condition that the animals have lived so long, and 

 felt, thought, and compared so much as to be able to associate 

 imaginations with the sensations induced, and which must de- 

 velop the foreseeing into instinct (66, 89) . But it is impossible 

 to suppose that this takes place with newly born animals, that 

 have scarcely begun to feel, and seem to have no other concep- 



