OF THE INTELLIGENCE AND OF INSTINCT. 153 



have just enumerated are the determining cause of most of 

 our actions. 



316. Certain actions, as those of the heart and intes- 

 tines, called peristaltic, are automatic, that is, they are alto- 

 gether independent of our will. Other movements are semi- 

 automatic, as the respiratory, and the force which determines 

 these seems to reside in the spinal marrow ( 255). 



The effects of habit and of the association of ideas form an 

 interesting subject of psychological inquiry ; but for this we 

 have no space, but must remain content with merely pointing 

 out the analogy between the acts resulting from these and 

 the operations of instinct. 



317. Faculties of Animals. Contrary to what might 

 have been expected, the study of animal instinct is more diffi- 

 cult than that of the human understanding ; we have, in fact, 

 no means of knowing how they think and feel; we can judge 

 only by the results, that is, their actions. 



318. All animals feel ; but in the lowest it is not easy 

 to perceive that the sensations they experience lead to any 

 act of judgment or reflection : they move to avoid an 

 obstacle, and that is all. The faculties of relation seem 

 limited to this in the infusoria and in zoophytes. But as we 

 ascend in the scale, acts appear in the history of animals, so 

 complex and so appropriate, as to force us to admit an ad- 

 mirable instinct to preside over these, and even a degree of 

 intelligence resembling, however distantly, our own. The 

 natural history of the beaver, the bee, and the ant, are singu- 

 larly instructive on this point ; whilst the intelligence of the 

 dog, the elephant, and the ape, has at all times attracted the 

 notice of man. 



319. Instincts of Animals. The character which espe- 

 cially distinguishes instinct from reason, is, that instinctive 

 actions are not the result of experience or of previously acquired 

 knowledge through the senses, whilst those of reason can be* 

 readily traced to that source. In man, the reason takes 

 almost wholly the place of instinct; in animals it is the re- 

 verse. As one of the simplest examples of instinct, we may 

 cite the case of ducklings hatched and brought up by a hen. 

 In spite of every effort made by the supposed parent, the 

 duckling at once seeks the water, and boldly plunges into a 

 medium of which it has no experience, and into- which its 

 adopted parent dare not follow. 

 As examples of instinctive acts of extreme complication, we 



