PRIMITIVE a.
groove (Anat.), a depression or groove in the epiblast of the primitive streak. It is not connected with the medullary groove, which appears later and in front of it. -- Primitive plane (Spherical Projection), the plane upon which the projections are made, generally coinciding with some principal circle of the sphere,…
PTERYGOID a.
pterygoid process of the human skull, but which, in all vertebrates below mammals, is not connected with the posterior nares, but serves to connect the palatine bones with the point of suspension of the lower jaw. -- Pterygoid process (Anat.), a process projecting downward from either side of the sphenoid bone, in man…
QUINIC a.
Pertaining to, derived from, or connected with, quinine and related compounds; specifically, designating a nonnitrogenous acid obtained from cinchona bark, coffee, beans, etc., as a white crystalline substance. [Written also chinic, kinic.]
RADIUS VECTOR n.
A straight line (or the length of such line) connecting any point, as of a curve, with a fixed point, or pole, round which the straight line turns, and to which it serves to refer the successive points of a curve, in a system of polar coördinates. See Coördinate, n.
RAIL n.
rail obstructions. (b) A guard rail. See under Guard. -- Rail joint (Railroad), a splice connecting the adjacent ends of rails, in distinction from a chair, which is merely a seat. The two devices are sometimes united. Among several hundred varieties, the fish joint is standard. See Fish joint, under Fish. -- Rail tr…