374 



ZOOLOGY. 



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

 bral column grows around the notochord, which finally 



FIG. 371. 



Fig. 369. Transverse section through the spinal cord of a calf, a, anterior, 6, 

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

 enbstantia gelatinosa; (/, anterior column of the white substance; h, lateral, i, pos- 

 terior column ; k, transverse commissures. After Gegenbaur. 



Fig. 370. Section through the vertebral column of Ammocoetes (lamprey). Ch, no- 

 tochord; cs, chorda! sheath ; M, spinal chord ; a, aorta; i\ veins. 



Fig. 371. Section through the spinal column of a young salmon. Ch, notochord ; 

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

 aorta; v, veins. After Gegtnbaur. 



forms the central portion of the bodies of the vertebra?, and 

 in the higher Vertebrates is wholly effaced ; the centra or 



