Glossary 631 



Lungs: Two sponge-like organs composed of minute air tubes, air sacs, 

 and capillaries. Located in the chest and used in breathing. 



Lye: An alkali used in making soap. 



Lymph (limf) : The part of the blood plasma which escapes from the 

 capillaries into the spaces between the cells. It gives off nutrients to 

 the cells and receives wastes, part of which it carries off through the 

 lymphatics, a vein-like system discharging into the blood through the 

 thoracic duct. 



Lymphatics (lim-f at/Iks) : The system of pipe-like vessels which carries 

 the lymph. 



M 



Macadam road (mak-ad'am) : A road constructed of several inches of 

 broken stone, overlaid with thin layers of fine stone and stone dust, 

 the surface being curved to shed water and rolled. Often coated with 

 tar compounds to bind the fine stone material together. 



Machine: A device for transforming and applying energy, and for 

 making work easier or less burdensome. 



Magnet: A piece of metal which will attract and hold to itself bits of 

 iron and steel. 



Magnetic field: The space around a magnet which is influenced by its 

 force. 



Magnetic needle: A slender bar of magnetized steel, suspended on a 

 pointed pivot, which tends to point north and south. The essential 

 part of a compass. 



Magnetism: A form of energy exercised by magnets in attracting iron 

 and steel. 



Magneto: A dynamo in which the magnets are permanent magnets 

 rather than electromagnets. 



Malnutrition (mal-nu-trish'Mn) : Lack of proper nourishment of the 

 body. 



Mammals: Animals which nourish their young with their own milk. 



Mantle: A small fiber bag coated with a solution of thorium; used 

 over a gas, kerosene, or gasoline flame to give a better light. 



Marble: A form of limestone capable of a high polish; used for build- 

 ing and ornamental purposes. 



Masticate: To chew. 



Matter: Any material of which things are made or which occupies space. 



Mean temperature: Average temperature. 



Mechanical advantage: The efficiency of a machine as measured by the 

 force it exerts divided by the force applied to it. 



Mechanical energy: The energy of motion; kinetic energy. 



Medium: A substance through which a force is transmitted, as air is 

 a medium for carrying sound. A substance upon which bacteria 

 colonies are developed. 



Medulla (me-dtil'd) : A wedge-shaped organ, the connecting link between 

 brain and spinal cord, which controls the action of the respiratory 

 system, the contraction of arteries, and the movements of the esophagus 

 in swallowing. 



Membrane: A thin, pliable sheet or layer of animal tissue; a lining or 

 covering of the organs of the body, as the mucous membrane. 



Meningitis (men-in-ji'tis) : Inflammation of the membranes which en- 

 velop the brain and spinal cord. 



Mercury: A fluid, white, heavy metal. One of the elements. 



