324 THE RHOMBENCEPHALON. 



elucidated. If the sulcus hypothalamicus really separate ventral 

 from dorsal zone in the inter-brain, as is claimed by many, it would 

 seem that both the optic and olfactory terminal nuclei might be 

 included in the posterior series ; but there is need of further inves- 

 tigation, as this places the whole cerebral hemisphere in the dor- 

 sal zone. 



The cortical connection of the terminal nuclei of the optic nerve 

 (Fig. 67) is established by fibers of the optic radiation (radiatio 

 occipito-thalamica) which rise in the lateral geniculate body and 

 in the pulvinar of the thalamus and terminate hi the cortex of the 

 calcarine region of the occipital lobe. From this cortical center, 

 corticifugal fibers run through the occipito-thalamic radiation 

 and brachium superius to the superior quadrigeminal colliculus. 

 This colliculus also receives a few fibers directly from the outer 

 root of the optic tract; it thus becomes the center of optic reflexes; 

 and axones of the superior colliculus form the anterior longitudinal 

 bundle, which completes the connection with opposite motor nuclei. 



The terminal nucleus of the olfactory nerve is situated in the olfac- 

 tory bulb (Figs. 26 and 63). The axones of this nucleus establish 

 direct cortical connection, first, with the uncinate region and an- 

 terior perforated substance by way of the lateral olfactory stria 

 and, probably, by way of the intermediate stria ; and, second, with 

 the parolf actory area, the olfactory triangle, the gyrus subcallosus 

 and the gyrus cinguli through the fibers of the medial stria of the 

 olfactory tract. The reflex connection of the olfactory nerve is 

 but little understood. The following probabilities may be stated : 

 First, the fornix, stria medullaris thalami, fasciculus retroflexus 

 and axones of interpeduncular ganglion; second, the fornix, thala- 

 mo-mammillary bundle and descending axones of the thalamus; 

 and, third, the fornix and the pedunculo-mammillary bundles 

 running into mid-brain, pons and medulla. 



Genetic Nuclei (Nn. Origines) (Fig. 96). The nuclei of the 

 oculomotor, trochlear, abducent, facial, accessory and hypoglos- 

 sal nerves and the nuclei of the motor roots of the trigeminal, 

 glossopharyngeal and vagus nerves represent the anterior columna 

 of gray matter in the cord and constitute the anterior columna 

 series. These nuclei are connected "with the cerebral cortex on both 



