374: 



ZOOLOGY. 



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

 bral column grows aronnd the notochord, which finally 



Fig. 371. 



Fig. 369.— Transverse section throngh the spinal cord of a calf, o, anterior, 6, 

 posterior lono:itndinal fis-itre ; c, central canal; d, jinterior, c, posterior cornna; fy 

 substantia gelatinosa; (?, anterior column of the white Bubstauce; A, lateral,;, pos- 

 terior column ; i-, transverse commissures.— After Gegenbaur. 



Fig. 370.— Section throuirh the vertebral column of Ammoccetes (lamprey). Ch, no- 

 tochord ; c«, chordal sheath ; m, spinal chord ; a, aorta ; tj, veins. 



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

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

 aorta ; w, veins. — After Gegenbaur. 



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

 la the higher Vertebrates is wholly effaced ; the centra or 



