CORTEX AND CORPUS STRIATUM in 



enlarged (Fig. 25). The striatum complex approaches that of 

 birds and the cortex is more extensive than in other reptiles 

 (Crosby, 191 7). 



Johnston (1916) found that the cerebral hemisphere of the 

 turtle is electrically excitable, but in the light of the later experi- 

 ments of Koppanyi and Pearcy (1925) it is uncertain whether this 



Fig. 16. — Dorsal view of the brain of the alligator. The shaded area 

 marks the electrically excitable field. After Bagley and Richter (1924). 



is a cortical response or from the underlying corpus striatum. In 

 the alligator electrical stimulation of the area shaded in Figure 26 

 (Bagley and Richter, 1924) produced various general movements 

 of the body and limbs, but it was not possible to produce move- 

 ments of the individual extremities. Here again we are somewhat 

 in doubt about the particular cells which were stimulated, 

 whether truly cortical or subcortical. 



The corpus striatum of mammals is generally said to be elec- 

 trically inexcitable, but recent studies show that in some lower 

 species (opossum, Rogers, 1924) this is not true. This is further 

 evidence that in lower mammals the physiological relations be- 

 tween cortex and corpus striatum are more intimate than in 

 higher forms. 



