Basal Ganglia of Birds 121 



animal depends on the nature of the hereditary 

 instinctive qualities of the nervous matter con- 

 stituting their basal ganglia and mid-brain. 

 From experiments made by Prof. Yerkes it 

 appears that these movements may, in certain 

 reptiles, become altered if the animal is sub- 

 jected to appropriate treatment; in other words, 

 the behaviour of reptiles is capable of being 

 modified by proper training. Thus turtles, 

 when subjected to labyrinth training, gradually 

 learn how to follow rather complicated paths 

 in order to reach their food. If an inclined 

 plane is so placed as to intercept their path, 

 to shorten the journey turtles on reaching the 

 summit of the obstruction, systematically throw 

 themselves over its edge so as the more speedily 

 to reach the food contained in the water of their 

 feeding tank. 1 



Among the class of birds the brain is remark- 

 ably constant in its outward form; its most 

 characteristic feature is the great size of the 

 basal ganglia as compared with other parts of 

 the brain. The increased development of these 

 structures is the result of the constant use 



1 The Animal Mind, by M. F. Washburn, p. 222. 



