394 



ZOOLOGY. 



segmented. In all Vertebrates above the lamprey, the verte- 

 bral column grows around the notochord, which finally 



Fig. 376. 



Fi?. 374 — Transveree section through the spinal cord of a calf, a, anterior, &, 

 poirterior longitudinal fissure ; c, central canal; d, anterior, e, posterior cornua; /, 

 substantia gclatinosa; (/, anterior column of the white isube^tance ; A, lateral, i, pos- 

 terior column ; k^ transverse commist-ures.— After Gegenbaur. 



Fig. 375.— SectioD throu^i^h the vertebral column of Ammoccetes (lamprey). Ch, no- 

 tochord; cs, chordal sheath ; m, spinal chord ; «, aorta; v, veins. 



Pig. 376. —Section tliroas;h the spinal column of a young salmon. Ch^ notochord ; 

 cs, chordal sheath ; m, spinal chord ; k, superior, k', inferior arch (rudimentary) ; a, 

 aorta ; y, veins.— After Gegenbaur. 



forms the central portion of the bodies of the vertebrae, and 

 in the higher Vertebrates is wholly effaced ; the centra or 



