668 COMPARATIVE ANATOMY 



angular (e). A membrane bone of the lower jaw. 



anisotropic. Doubly refracting or polarizing. 



ankylosis. Consolidation or fusion of the bones of a joint or suture. 



anlage. The embryonic fundament of an organ. 



anterior. Toward the head. In human anatomy toward the ventral side. 



anthropoids. The man-like apes. 



antibodies. Chemical substances formed by a body in reaction to foreign substances 



introduced, 

 antihelix. The inner curved edge of the external ear. 

 antithrombin. A substance in the blood which prevents clotting. 

 antitoxin. A substance in the blood serum antagonistic to a poisonous substance or 



toxin. 

 antitragus. An ear prominence opposite the tragus. 

 antrum. A bone cavity. 

 anus. The egestive opening of the intestine. 

 aorta. The chief artery which leaves the heart. 

 aponeurosis. A connective tissue membrane or fascia which surrounds or attaches a 



muscle. 

 appendices epiploicae. Fatty pouches attached to the colon. 

 appendicularia. A free-swimming pelagic genus of urochordates. 

 aqueous hiunor. The refractive liquid between cornea and lens of the eye. 

 arachnoid. A web-like membrane between the dura mater and pia mater of brain and 



spinal cord. 

 arbor vitae. The tree-Uke arrangement of hber tracts seen in section of the cerebellum. 

 arch. .\ bent or curved structure. 

 archenteron. The primitive digestive cavity. 

 archencephalon. The primitive forebrain of chordates. 

 archetype. An ideal original form. 



archicortex ('archipallium). The olfactory cerebral cortex including the hippocampus, 

 archinephros. The primitive kidney or mesonephros (Wolffian body). 

 archipterygium. The original appendicular skeleton of vertebrates. 

 areolar tissue. .\ fibrous tissue containing minute interspaces, 

 arrectores pilorum. Cutaneous muscles attached to hairs, 

 articulare. The bony articular element of the lower jaw of lower vertebrates, 

 arytenoid. A pitcher-like cartilage of the larynx or voice-box. 

 assimilation. Constructive metabolism, 

 astragalus. The ankle bone which articulates with the tibia, 

 ateliotic dwarf. A normal dwarf or midget, 

 atlas. The first cervical vertebra. 

 atrium, i. An auricle of the heart. 2. The chamber surrounding the gills of lower 



chordates. 

 atrioventricular bundle. A muscle which connects auricle and ventricle, 

 atrophy. The wasting of a part or organ. 



atropine. A poisonous alkaloid which stimulates the sympathetic, 

 auditory bulla. A capsule-like portion of the tympanic bone, 

 auditory meatus. The external meatus extends from the drum to the outside, 

 auditory tube. A passage from the middle ear to the pharynx. 

 Auerbach's plexus. A sympathetic plexus in the wall of the intestine, 

 auricle, external. The pinna of the ear. 



auricularis magnus nerve. A sensory nerve distributed to face, ear, and neck. 

 Australopithecus. A South .\frican fossil anthropoid. 

 autonomic system. The sympathetic and parasympathetic nervous systems. 



