GLOSSARY 447 



Mi'cro-scope (Gr. mikros, little, and skopein, to see), an instrument 

 which makes minute objects appear large. 



Milk, the fluid which all female mammals secrete for the nourishment 

 of their young. 



Mi'tral (Gr. mitra, a head covering), the valve between the left auricle 

 and ventricle ; when closed it resembles a priest's miter or hat. 



Molar (Lat. mola, a mill), a tooth having a flat surface for grinding 

 food. The last three teeth on each side of each jaw are molars. 



Mold, a low order of microscopic plants which usually grow in the in- 

 terior of substances. Common forms send up spore stalks which 

 form the velvety coating popularly called mold. 



Mor-phine' (Gr. morpheus, the god of sleep), the principal alkaloid of 

 opium. 



Mo'tor nerves (Lat. mover e, to move), the nerves which carry orders 

 from the brain or spinal cord to cause the cells of the body to act. 



Mu'cous mem'brane, the soft, skin-like membrane lining cavities which 

 open upon the surface of the body. 



Mu'cus (Lat. mucus), the thin, slimy fluid produced by the epithelium 

 lining the organs of digestion and respiration. 



Mu-ri-at' ic acid (Lat. muria, brine), the common name of hydro- 

 chloric acid. The acid is very sour and corrosive. It combines 

 with sodium to form common salt, but many of its combinations 

 are poisonous. 



Mus'cle (Lat. musculus, a little mouse), a collection of cells which can 

 become thicker and shorter and so produce motion. 



Nar-cot'ic (Gr. narkoun, to benumb), a substance which hinders the 



action of nerves and nerve cells and produces sleep. 

 Na'sal duct (Lat. nasa, the nose), the duct which carries tears from 



the eyes to the nose. 

 Nerve (Gr. neuron, nerve), a collection of the threads which conduct 



impulses between the cells of the body and the central nervous 



system. 



Neuritis (new-rftis) (Gr. neuron, nerve), inflammation of a nerve. 

 Neu'tral-ize (Lat. neuter, neither), to make neither acid nor alkaline. 

 Nic'o-tine, the active principle in tobacco, named from the Frenchman 



Nicot who introduced tobacco into France in 1560. 

 Nu'cle-o albumin, a form of albumin containing iron and found in the 



nucleus of cells. From it hemoglobin is formed. 



