SEPTUM, HIPPOCAMPUS, PALLIAL COMMISSURES 



437 



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19 



20 



Fig. 19 Cistudo Carolina, dissection of the right hemisphere to show the 

 medial wall through the lateral ventricle. Nearly the whole lateral wall of the 

 hemisphere and the choroid plexus have been removed. The rough surface in. 

 the lower part represents the region in which the large fiber bundles were dis- 

 sected away by means of needles. The area parolfactoria appears as a some- 

 what bean-shaped ridge. Between this and the foramen is the greater part of 

 the primordium hippocampi. It extends forward as a very slender ridge in the 

 groove over the area parolfactoria and becomes enlarged in the olfactory bulb. 

 Compare figures 18 and 19. The light ridge over the primordium is occupied by 

 the fimbria. 



Fig. 20 Cistudo Carolina, medial view of the right hemisphere after removal 

 of the brain stem. Note especially the slender primordium hippocampi and the 

 fimbrio-dentate sulcus extending into the temporal region of the hemisphere. 

 In lizards the primordium is much larger. 



