ANIMAL SENSATION AND PERCEPTION. 61 



open air they were certainly accustomed to the wind, 

 and to the way in which it moves trees and branches, 

 so that they were not alarmed by a phenomenon 

 which they recognized from experience. I fastened 

 a cord to the head of the shrub which I passed 

 through a hole in the door, making another to look 

 through, and in this way I moved it to and fro as 

 the wind might have done. One day when there 

 was a high wind which could be heard in the room, 

 and when the current of air through the window 

 was perceptible, I tried the experiment when the con- 

 ditions of resemblance were perfect. And yet when 

 the violent movement and oscillation of the shrub was 

 combined with the noise of the wind, the frightened 

 birds all fluttered about, and after repeating the 

 movement, and then allowing it to subside, they kept 

 away from the shrub and did not dare to settle 

 on it. 



At another time, aided by an ingenious young 

 friend, I constructed a toy windmill, of which the 

 vanes were moved by weights. I placed this toy 

 in a cage, so arranged that its motions could be 

 regulated from the outside, and I put into the cage 

 a sparrow, which had 'been taken from the nest, and 

 which consequently had no experience of the external 

 world. Much patience was needed, since the toy re- 

 quired careful adjustment and was easily thrown out 

 of gear, but I managed it at last. The sparrow pecked 

 at the little mill as soon as he was put into the cage, 



