GLOSSARY 447 



Medulla. The marrow. Anything resembling marrow, as the 

 medulla oblongata. Also the central part of an organ. 



Medullated. Containing or covered by a substance resembling 

 medulla or marrow. Medullated nerves covered with a myelin sheath. 



Mediastinum. (From the' Latin words in, medio, stare, "to stand 

 in the middle.") The space in the middle of the chest between the 

 two pleurse, divided into anterior, middle, posterior, and superior 

 mediastinum. 



Membrane. (From the Latin word membrana, from membrum, 

 "a member.") A thin layer of tissue lining or surrounding a part or 

 separating adjacent cavities. 



Mesentery. A fold of peritoneum which connects the intestine 

 with the posterior abdominal wall. 



Meshes. Net-work, reticular. 



Mesocolon. The fold of peritoneum connecting the colon with the 

 posterior abdominal wall. 



Mesoderm. The middle layer of the blastodermic vesicle of the 

 embryo, derived from both the ecto- and entoderm. 



Mesogastrium or Umbilical. The region corresponding to the 

 part of the abdominal wall surrounding the umbilicus (navel). 



Metabolism. The group of phenomena occurring in the tissues 

 whereby the organic beings transform foodstuffs into complex tissue 

 elements (anabolism), and convert complex substances into simple 

 ones in the production of energy (katabolism) . 



Metacarpal. Relating to the metacarpus. 



Metacarpus. (From the Greek words meaning beyond the wrist.) 

 That part of the hand between the bones of the wrist and the bones 

 of the fingers. 



Metatarsal. Pertaining to the metatarsus. 



Metatarsus. (From the Greek words meaning beyond the instep.) 

 That part of the foot between the bones of the instep and the bones 

 of the toes. 



Micturition. (From the Latin word micturire, "to pass water.") 

 The act of passing urine. 



Millimeter (mm.). The thousandth part of a meter. Equal to 

 0.039370 inch. 



Minimus. The least, smallest. 



Minor. The lesser, smaller. 



Minor Calices. The smaller calices. 



Mitral (bicuspid). (Resembling a miter, a covering for the head 

 worn by popes, bishops, and cardinals.) The valves of the left auriculo- 

 ventricular opening of the heart. 



Molecular. (From the Latin word mole, "a mass"). Pertaining 

 to or composed of molecules. 



Molecule. (From the Latin word, a dim. of moles, "mass.") The 

 minute portion of matter. In physics the smallest quantity into which 

 a substance can be divided and retain its characteristic properties; 

 or the smallest quantity of any gas, liquid, or solid that can exist in 

 a free state. 



Motor. (From the Latin word movere, "to move.") Moving or 

 causing motion. Concerned or pertaining to motion, as motor cells, 

 motor nerves, motor centre. 



