no BRAINS OF RATS AND MEN 



voluminous intrinsic connections of all parts of the striatum com- 

 plex it serves as efferent path for part of the caudate activities 

 also. 



The efferent fibers from the globus pallidus go downward in 

 a large and complex strand of fibers known as the lateral fore- 

 brain bundle, which is the precursor of the internal capsule sys- 

 tem of mammals. In lower mammals (and probably in reptiles) 

 efferent fibers also leave large cells of motor type in the ventral 



midbrain 

 cercbcllurr) 



cortex 



medulla obhrigaba 



olfactory bulb- 



Fig. 25. — ^The brain of a young alligator ^^ cm. long as seen from the 

 right side, one and one-half times natural size. The lateral cerebral 

 cortex has been removed, opening the lateral ventricle and exposing the 

 underlying corpus striatum complex. Redrawn from Crosby (1917). 



part of the head of the caudate nucleus (olfacto-striatum). These 

 go downward in the medial forebrain bundle. There is a third 

 and very large efferent tract passing down in the medial fore- 

 brain bundle from the amygdala and pyriform lobe, the olfactory 

 projection tract of Cajal. All parts of the strio-amygdaloid com- 

 plex are intimately connected by short intrinsic fibers, and the 

 pathway taken by the efferent discharge from this complex in 

 any reaction is probably determined by the particular motor 

 organs to be innervated. 



In lizards and serpents the arrangements described for turtles 

 are considerably modified and complicated, but into these details 

 we need not here enter. In crocodiles the hemispheres are further 



