GLOSSARY 913 



Keratin (ker'atin), a nitrogenous substance forming the chemical foundation 



of hair, horn, feathers, nails, claws, etc. 

 Kinetic energy (kinet'ik), energy inherent in motion of a body. 



Labium (la'bium), posterior boundary or lower lip of an insect's mouth. 

 Labrum (la'brum), the exoskeletal anterior boundary or upper lip of the in- 

 sect's mouth. 

 Lacrimal (lak'rimal), pertaining to tears. 

 Lacteal (lak'teal), pertains to milk; refers to lymphatics of the intestinal 



region because of their light color following absorption of fat. 

 Lacuna (laku'na), a cavity or space, particularly that of bone, which contains 



the bone cells. 

 Lamella (lamel'a), a thin layer or plate. 



Larva (lar'va), the young stage of an animal, which changes form during life. 

 Larynx (lar'inks), the expanded upper end of the windpipe or trachea; voice 



box. 

 I Lethal (le'thal), capable of producing death. 

 Leucocyte (lii'kSsit), a white blood corpuscle. 

 Ligament (lig'ament), a band of white fibrous connective tissue connecting 



structures other than muscles; particularly joining bones at the joints. 

 Limpet (lim'pet), a small tj-pe of gastropod (Mollusca) with a simple uncoiled 



shell. 

 Linin (li'nin), the delicate threadlike structure which supports the chromatin 



granules in the nucleus. 

 Linkage (lingk'ij), the constant association of particular genes in certain 



chromosomes. 

 Lipase (li'pas), a fat-splitting enzj-me. 

 Lipin (li'pin), fatty substance. 

 Lipoid (lip'oid), fatlike substance. 

 Lophophore (lo'fofor), a disc which surrounds the mouth and bears the 



tentacles of the Bryozoa. 

 Lumbar (lum'ber), pertaining to the region usually known as the small of the 



back. 

 Lumen (lu'men), internal cavity of a tubular duct, gland, vessel, etc. 

 Luminescence (lu mi nes'ens), the emission of light from the body. 

 Lymph (limf), the blood plasma and white corpuscles in the lymph spaces 



about the tissues. 

 Lymphatic (limfat'ik), a vessel which carries lymph. In general, pertaining 



to lymph. 



Macronucleus (mak ro nu'kle us), the large nucleus of certain protozoans sup- 

 posed to control vegetative functions. 



Madreporite (mad're p6 rlt), the strainerlike external aperture of the water- 

 vascular system of echinoderms. 



MalpigMan (mal pig'i an) body, a structure in the cortex of the kidney, com- 

 posed of a glomerulus and Bowman's capsule which serves to take urine 

 from the blood. 



Mantle (man't'l), a fold of the body wall which partially envelopes the body; 

 present in most mollusks and here secretes a shell. 



Marsupial (mar su'pi al), having a pouch for carrying the young. 



Marsupium (mar su'pi um), an external pouch used in carrying the young, as 

 in the kangaroo or opossum. 



Matrix (ma'triks), the mother substance, such as that which encloses anything; 

 the intercellular material of cartilage or other sustentative tissue. 



Maturation (mat ti ra'shiin), the series of changes occurring in the development 

 of germ cells before fertilization, including a reduction in the number 

 of chromosomes in the cells. 



