CH. in.] ACTIONS OF INSTINCTS. 133 



receive the external impressions necessary thereto, and which 

 are appointed, as it were, to this end. For example, when 

 nutriment is necessary to the body, the fluids collected in the 

 empty stomach must impress on it an external impression, 

 which excites the sensational instinct of hunger ; when animals 

 ought to propagate their kind, the male inhales from the female 

 during heat an odour which causes the instinct of copulation to 

 be active. On such occasions, even certain external sensations 

 become sensational stimuli to the animal that formerly were 

 not so, or had even a contrary effect, as, for example, the sight 

 or smell of the sexual organs, previously unnoticed or even 

 disagreeable and disgusting, become the sensational stimuli 

 of the strongest sensual pleasure. At the same time, when the 

 instincts are regularly excited into activity in accordance with 

 the object of nature, the circumstances whereby they can be 

 satisfied are so carefully provided for previously, that the satis- 

 faction of the instincts can hardly fail. Thus, hunger is rarely 

 excited in animals that lie dormant through the winter, until 

 they can find food in the fields. So also the instinct of self- 

 preservation operates, when they fatten themselves towards 

 winter, or return into a warmer climate, or creep into a retreat 

 from the cold, no sooner than they have occasion. Lastly, 

 when once the natural instincts are excited, it is difficult to 

 cause them to cease, by means of psychological or physiological 

 hindrances, before they are satisfied, which may, however, be 

 done as to desires, aversions, and even emotions. A hungry, 

 or vindictive, or enamoured person is not easily appeased by 

 artful management, but the satisfaction of the instinct must 

 be effected, that is to say, repletion of the stomach, or accom- 

 plishment of copulation, or wreaking of vengeance. Nature, 

 indeed, seems to have actually weakened or diminished those 

 hindrances which on previous occasions moderated or prevented 

 sensational stimuli (47), so that the instincts might break forth 

 without restraint and overcome all obstacles, and continue their 

 appointed time until their satisfaction has been sufficiently re- 

 peated. In other desires and even in emotions, the animal with- 

 draws the sensational stimulus voluntarily, being conscious of it, 

 and its effects ; but in the instinct it is not conscious of the 

 stimulus as it is only obscurely perceived (262) ; consequently, its 

 effects are unknown, and the animal is carried blindly on by 



