CEREBRAL HEMISPHERES AND MEMORY 241 



transparent bell-jars placed in their way were avoided 

 just as much as chairs and table legs, or boards of 

 different colours." It is evident that optic space-per- 

 ception still continues, even when the cerebral hemi- 

 spheres (and with them the associative memory) have 

 disappeared entirely. If such a pigeon is placed in 

 an uncomfortable position, it flies to another place 

 with perfectly coordinated movements. Schrader 

 gives the following description : " We place our 

 pigeon on the cloth-covered stopper of a large bottle. 

 The stopper is large enough to support the animal on 

 both feet, and is placed in the middle of a large, empty 

 room, so that the pigeon is one to two metres above 

 the floor. For some minutes the pigeon sits with its 

 head drawn in, its feathers ruffled, in a condition of 

 sleep or inhibition ; then it shakes itself and begins to 

 turn around and look about ; finally it stoops and with 

 an exertion looks down on the floor as if it wished to 

 measure the height. It makes preparations to fly 

 down, stops again, however, turns about once more, 

 and again directs its attention to the floor. The dura- 

 tion of this play varies, but at last it flies down in a 

 slight curve and alights easily on the floor. If a 

 cross-bar is placed at the same height, one or two 

 metres from the bottle, the pigeon flies determinedly 

 to the bar and seats itself there. If a chair be used 

 instead of a bar, the pigeon is seated on the arm" (4). 

 These experiments show that these pigeons are able 

 to measure distance by visual impressions also. 



Schrader's observation is also of importance for the 



IV 



