814 Appendix 



Acromegaly (ak ro -meg' a li) (Gr. akron, point; megas, large), a disease in 

 which the head, hands, and feet become enlarged, caused by overactivity 

 of the pituitary gland. 



Actinic rays (ak-tin'ik) (Gr. aktis, beam or ray), the chemically active rays of 

 light. 



Adaptation (ad ap -ta' shun) (L. ad, to; aptus, fit), the process of becoming 

 fitted to an environment or the mutual fitness of an organism to its internal 

 and external environments. 



Adaptive radiation, the radiating or spreading in various directions of organ- 

 isms arising from the same generalized stock and the assuming of dif- 

 ferent characters by them because of their adaptation to different kinds of 

 environments encountered. 



Adductor (a -duk' ter) (L. ad, to; duco, to lead), leading toward the center or 

 median line (contrast with abductor). 



Adipose (ad' i pos) (L. adiposus, fatty), pertaining to fat. 



Adrenal (ad -re' nal) (L. ad, near; renes, kidney), an endocrine (ductless) gland 

 near the kidney (same as suprarenal). 



Adrenalin (ad -ren' a lin), a hormone secreted by the inner part or medulla of 

 the adrenals. 



Aerobe (a'erob) (Gr. aer, air; bios, life), requiring free oxygen for living (con- 

 trast with anaerobe). 



Aestivation (estivation) (es ti -va' shun) (L. aestas, summer), a semitorpid con- 

 dition of certain animals in summer. 



Afferent (af er ent) (L. ad, to; ferro, to bear), conveying toward a center. 



Agglutination (a gloo ti -na' shun) (L. agglutinans, gluing or clumping together), 

 the collection of cells in a liquid into clumps due to specific substances 

 known as agglutinins. 



Agnostic (ag-nos'tik) (Gr. a, not; gnosco, to know), no convictions on a subject. 



Albinism (al'binizm) (L. albus, white), the absence of normal pigments in the 

 hair, skin, and eyes of animals or the absence of normal chlorophyll in 

 plants which normally possess it. 



Algae (al'ji) (L. alga, seaweed), simple, green, chlorophyll-bearing plants. 



Alimentary (al i -men' ta ri) (L. alimentum food), pertaining to food and di- 

 gestion. 



Allantois (a -Ian' to is) (Gr. alias, sausage), an embryonic membrane of higher 

 vertebrates for respiration. 



Allelomorphs (alleles) (a -le' lo morf) (Gr. alleon, of one another; morphe, 

 form), genes similarly located in homologous chromosomes. 



Allergy (al'erji) (Gr. alios, other; ergon, activity), a reaction to a foreign sub- 

 stance, especially protein. 



Alternation of generations, see Metagenesis. 



Alveolar (al -ve' o lar) (L. alveolus, small cavity), small cavity; foamlike. 



Ambulacral (am bu -la' kral) (L. ambulacrum, covered way), regions in echino- 

 derms in which are located the ambulacral tube feet for locomotion. 



Amino acid (a -me' no), organic acid containing the amino group (NH2) and 

 serving as building material for proteins. 



Amitosis (ami -to' sis) (Gr. a, without; mitos, thread), cells dividing directly 

 without forming chromosomes, spindle, etc. 



