444 CHORDATE ANATOMY 



labyrinth. The internal ear of vertebrates. 



lacrimal. Pertaining to the tears. 



lacteal. Pertaining to milk. An intestinal lymphatic. 



lacuna. A pit or hollow. In bone the cavity filled by a bone cell. 



lagena. An outgrowth of the sacculus of the ear. 



lamella. A thin leaf or plate as of bone. 



lamina terminalis. The thin membrane which forms the anterior wall of the third 

 brain ventricle. 



lanugo. The fine hairy covering of the fetus of man. 



larva. An immature but active stage in the development of an organism. 



larynx. The cartilaginous organ which encloses the vocal cords. 



lateral line. A series of sense organs which extends along the sides of the body of 

 fishes and some amphibia. 



lenunatochord or bothriochord. An arthropod structure which W. Patten has com- 

 pared with the notochord. 



leucocyte. A "white" blood corpuscle. 



Lieberkuehn's glands or crypts. Tubular mucous glands of the intestine. 



linea alba. The tendon in the median line of the abdomen. 



lingual. Pertaining to the tongue. 



lipase (steapsin). A fat-splitting enzyme secreted by the pancreas and some other 

 digestive organs. 



lipoids. Fat-like cell constituents soluble in alcohol and ether. 



lobule. A normal small division of a lobe. 



Lorenzini's ampullae. Tubular sensory organs of Elasmobranchs. 



luciferin. A substance which combined with luciferase in luminous animals produces 

 light. 



lumen. The cavity of a hollow organ. 



lunula. The whitish crescent at the root of a nail. 



luteal hormone. The hormone progestin secreted by a corpus luteum. 



lymph. The coagulable liquid of the lymphatic vessels. 



maculae acusticae. The sensory patches of the sacculus and utriculus. 



macula lutea. The point of clearest vision at the center of the retina. 



malar bone. The zygomatic or cheek bone. 



malleolus. The hammer-headed process of a bone (tibia and fibula). 



malleus. The ear ossicle which is attached to the drum. 



maltase. The enzyme which splits maltose into dextrose. 



manuna. The breast or mammary gland. 



mammillary bodies. Paired rounded bodies posterior to the tuber cinereum. 



mandible. The horseshoe-shaped lower jaw. 



mandibular arch. The anteriormost visceral arch. 



mantle. The body wall of urochordates. The shell-secreting organ of molluscs. 



manubrium. The anterior division of the sternum. 



marsupial pouch. The abdominal pouch of marsupials in which the young are carried 



after birth. 

 mastoid. A process of the temporal bone. 



maturation. The process by which homologous chromosomes are segregated. 

 maxilla. The upper jaw bone, 

 maxillo-turbinals. The inferior turbinated bones. 

 meatus. A passage or opening. 



Meckel's cartilage. The lower jaw of cartilaginous fishes. 

 mediastinum. The thick partition which divides the two pleural cavities. 



