. The Journal of comparative neurology and psychology. the sensory root. The mesen-cephalic bundle crosses the motor Ijundles nearly at right angles and there isno indication of interchange of fibers. X ^^• Acipenser, and the mammals studied including the human course of the bundle in Scyllium canicula, Acipenser and tec-tums was described in my previous paper. I wish to make certainadditional notes on the basis of preparations made since that paper 6l2 Journal of Comparative Neurology and Psychology. was published. In Scyllium canicula the course of the radix mesen-cephalica throu
. The Journal of comparative neurology and psychology. the sensory root. The mesen-cephalic bundle crosses the motor Ijundles nearly at right angles and there isno indication of interchange of fibers. X ^^• Acipenser, and the mammals studied including the human course of the bundle in Scyllium canicula, Acipenser and tec-tums was described in my previous paper. I wish to make certainadditional notes on the basis of preparations made since that paper 6l2 Journal of Comparative Neurology and Psychology. was published. In Scyllium canicula the course of the radix mesen-cephalica through the ccrebelhun was somewhat complex and I sug-gested that this accounted for Edingers mistaking this bundle for atractus tecto-cerebellaris. In Scyllium stellare the course of thebundle is identical Avith that in S. canicula except that it makes amuch less complex bend or loop in passing through the cerebelluminto the velum medullare anterius. The course of the l)undle is sodirect that there is no chance of losing or mistaking it in following it. Fig. 11. Acipeiiser riibicundiis; some cells of the nucleus tecti as seeu in atransverse section. The bundle of fibers is the beginning of tlie radix niesen-cephalica. X ^^^• through transverse sections. The same is true of Squalus , in sagittal sections of Scyllium stellare the whole course of thebundle is very clearly followed (Figs. 9 and 10). The way inwhich the mesencephalic bundle crosses the motor root bundles inthese sagittal sections makes it quite impossible to make any mistakeas to wdiich root the mesencephalic bundle enters. In Acipenser the bundle was previously followed only into thetectum, not to its cells of origin. I have since traced the bundle in Johnston, flu^ Radix MesenceplHilica Trigemint. 613 other preparations with perfect clearness around the lateral part ofthe tectum to the nucleus magnocellularis tecti. The fibers run in abroad bundle immediately outside the ependymal layer and at theant
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