Glossary 615 



Adenoids (ad'e-noidz) : Spongy enlargements of the tissues of the upper 



end of the pharynx which cause difficulty in breathing through the 



nose. 

 Adrenal glands (ad-re'nal) : Two ductless glands, one in front of each 



kidney. 

 Adulterant (d-dul'ter-ant) : A substance placed in food to increase its 



bulk or cheapen it, which makes it less nutritious. 

 Aeration (a-er-a'shwn) : The process of introducing air into a substance, 



such as soil or water. 

 Aerial (a-e'ri-ol) : One or more wires suspended in the air to give out 



or collect radio waves; antenna. 

 Agar-agar (a'gar-a'gar) : A jelly-like substance obtained from seaweed; 



used as a food for the growth of bacteria. 



Agriculture: The cultivation of the soil, including raising of crops. 

 Air: A colorless, odorless, tasteless mixture of several gases; necessary 



^ to the respiration of all living things. 

 Air conditioning: Supplying clean indoor air that has exactly the right 



f temperature and moisture content for human comfort and health. 

 Airplane: A heavier-than-air machine capable of flying in the air. 

 Air pump: A pump for exhausting air from a closed space, or for 



^ forcing air into a closed space. 

 Air sac: An air cell in a living thing. 

 Airship: See dirigible balloon. 



Albumen (al-bu'men) : The white of egg; a form of protein. 

 Albumin (al-bu'min) : A thick, sticky nitrogenous protein found in both 



animal and plant tissue. An essential part of the blood. 

 Alcohol: The intoxicating part of liquors. Commonly produced by the 



fermenting action of yeast on sugar. 

 Alimentary canal (al-i-men'td-ri) : The whole digestive tract of a man 



or an animal. 

 Alkali (al'kd-li) : One of a class of substances which is soluble in water 



or alcohol, and which, when combined with fats or oils, makes soap. 



An alkali turns red litmus paper blue. Soda and potash are two of 



the most common alkalis. 

 Alloy (d-loi') : A substance composed of two or more metals closely 



united, usually by being fused, or melted together, such as solder or 



brass. 

 Alternating current: An electric current that changes its direction in 



a circuit many times per second. 

 Altimeter (al-tim'e-ter) : An instrument much like the barometer, used 



for measuring height above sea level. 

 Altitude : Height ; distance above sea level. 

 Ammeter (am'me-ter) : An instrument for measuring, in amperes, the 



amount of an electric current. 

 Ammonia (d-mo'm-d) : A colorless, pungent, alkaline gas, composed of 



hydrogen and nitrogen. Used in making artificial ice, in solutions as 



a medicine, and as a general household cleansing agent. 

 Amoeba (d-me'bd) : A minute, one-celled animal of constantly changing 



shape. 



Ampere (am-par') : A unit used for measuring the amount of an elec- 

 tric current. 

 Amylopsin (am-I-lop'sin) : A ferment in pancreatic juice which helps 



digest starch. 

 Anaesthetic (an-es-thetlk) : A gas or a drug used to reduce pain or to 



produce unconsciousness. Cocaine and ether are examples. 



