MEDULLARY a.
Filled with spongy pith; pithy. Medullary groove (Anat.), a groove, in the epiblast of the vertebrate blastoderm, the edges of which unite, making a tube (the medullary canal) from which the brain and spinal cord are developed. -- Medullary rays (Bot.), the rays of cellular tissue seen in a transverse section of exoge…
MICROCOCCUS n.
teria, in the form of very small globular or oval cells, forming, by transverse division, filaments, or chains of cells, or in some cases single organisms shaped like dumb-bells (Diplococcus), all without the power of motion. See Illust. of Ascoccus.
MICROMETER n.
rometer, in which the two images are formed by the double refraction of rock crystal. -- Filar, or Bifilar, micrometer. See under Bifilar. -- Micrometer caliper or gauge (Mech.), a caliper or gauge with a micrometer screw, for measuring dimensions with great accuracy. -- Micrometer head, the head of a micrometer scr…