Chorda dorsalis

from The Collaborative International Dictionary of English v.0.48

Notochord \No"to*chord\, n. [Gr. nw^ton the back + E. chord.]
   (Anat.)
   An elastic cartilagelike rod which is developed beneath the
   medullary groove in the vertebrate embryo, and constitutes
   the primitive axial skeleton around which the centra of the
   vertebrae and the posterior part of the base of the skull are
   developed; the {chorda dorsalis}. See Illust. of {Ectoderm}.
   [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Chorda \Chor"da\, n. [NL., fr. L. chorda. See {Chord}.] (Anat.)
   A cord.
   [1913 Webster]

   {Chorda dorsalis}. [NL., lit., cord of the back.] (Anat.) See
      {Notochord}.
      [1913 Webster]