rhombocœlia

Century Dictionary and Cyclopedia

1. n. The sinus rhomboidalis of the myelon: a dilatation of the cavity of the spinal cord in the sacral region. This is a sort of ventricle, or enlargement of the hollow of the primitively tubular spinal cord, observable in many vertebrate embryos, representing to some extent the complicated and persistent system of ventricles in the opposite end of the same neural axis; but it is not often well marked in adults. It is most notable and persistent in birds, in which class it presents the figure which has suggested the term sinus rhomboidalis and its later synonym rhombocœlia or rhombocœle, applied conformably with a recent system of naming the several cœliæ of the cerebrospinal axis. See cut under protovertebra.