CORTEX AND CORPUS STRIATUM 



95 



up to normal, the behavior changes and approaches 

 that of a bird deprived of cerebral hemispheres but 

 with normal thalamus. 



It appears that the thalamus 

 independently of the cerebral 

 hemispheres (that is, when the 

 latter have been completely re- 

 moved) controls reflexes arising 

 from painful stimulation and 

 many of the fundamental vis- 

 ceral reflexes (hunger, thirst, 

 body temperature, respiration, 



^^^')' Fig. 1 8.— The dorsal 



Figure l8 illustrates the ex- surface of the brain of the 



ternal form of the brain of the P^S^on, showing the elec 



J T7« ^ trically excitable areas 



pigeon and leisure 19 a cross- .„ ^ 



^ ° 111 (Rogers, 1 922^). /, maxi- 



section through the cerebral mum constriction of pupil 

 hemispheres. The striatum com- of opposite eye; 2, less 

 plex of the bird is unique in P^pill^ry constriction; 



I , 1 Si bilateral winking; 4. 



several respects : the great reduc- ^^^^.^^ ^^^ ^^^^.^^ ^^^^ 



tion of the olfactory component, (from underlying ectostri- 



the enormous increase in thala- atum); 5, depression of 



mic connections (both somatic ^^^^^' °^ ^°^^^^^^ ^"^ 



and visceral), the reduction to 



insignificant proportions of the overlying cerebral 



cortex. 



Rogers (1922) found in decerebrating pigeons that 

 if the cores of the hemispheres (i.e., the mesostriata 

 of Fig. 19) are left undisturbed the remainder of the 



