THE NERVOUS SYSTEM 



491 



Sympathetic nerve cords or connectives unite the series of sympathetic 

 ganglia. 



Reptiles. The cerebral hemispheres of reptiles are larger than those 

 of amphibia and by extension caudad have partially overgrown the 

 diencephalon. The paired ventricles are nearly obliterated by the enlarge- 

 ment of the striate bodies, archistriatum and neostriatum. For the 

 first time in the vertebrate series, a cortical layer of pyramidal cells 

 appears in the pallium, having nervous connexions with fibers of the 



Fig. 407. — Brain of goose, ac, anterior commissure; cb, cerebellum; e, epiphysis; 

 /, flocculus; h, hypophysis; hs, hyperstriatum; i, infundibulum; I, lateral ventricle; m, 

 medulla oblongata; 7ns, mesostriatum; ob, olfactory bulb; ol, optic lobe; s, striatum; 

 I, temporal lobe; III, third ventricle; x, plane of section E. (From Kingsley's "Com- 

 parative Anatomy of Vertebrates," after Biitschli.) 



oKactory tract. Septum and hippocampus appear in the medial wall 

 much as in amphibia. The dorsal wall of each hemisphere is homologized 

 with the gyrus dentatus of the mammalian brain. The transitional 

 region between this dorsal pallium and the neostriatum has important 

 potentialities, since it is unconnected with olfactory fibers, and since in 

 mammals it becomes the neopallium from which develops the greater part 

 of the cerebral cortex on which the higher psychical activities of man 

 depend. (Figs. 406, 414) 



In the region of the diencephalon of lizards the anterior epiphysial 

 outgrowth, the parietal organ, develops a lens, retinal and pigment layers, 

 and nerve fibers which are connected with centers in the brain wall. 



