xni PHYLUM CHORDATA 545 



hand, there is no such union ; the fibres of the tsenia run towards 

 the foramen of Monro, where they become divided into several sets. 

 Of these one set, constituting the great majority of the fibres, 

 pass into the hippocampus of the opposite side, giving rise to a 



Nit 



Cr.ce 



HH 





Met 



m\ 





Ro7 



M 



FIG. 1133. Brain of Dog. A, dorsal ; B, ventral ; C, lateral aspect. B. ol. olfactory lobe ; Cr. ce. 

 crura cerebri ; Fi. p. great longitudinal fissure ; HH, HH', lateral lobes of cerebellum ; Hyp. 

 hypophysis ; Ml. spinal cord ; NH, medulla oblongata ; Po. pons Varolii ; VH. cerebral 

 hemispheres ; Wu, middle lobe (vermis) of cerebellum ; 1 XII. cerebral nerves. (From 

 Wiedersheim's Comparative Anatomy.) 



hippocampal commissure (hip. com.), the great development of which 

 readily leads to its being mistaken for a corpus callosum. The fibres 

 entering into the formation of this commissure correspond, however, 

 not to the fibres of the corpus callosum, but, as proved by their 

 VOL. II N N 



