Accommodation of the Eye. The alteration in the shape of the crystalline lens, which accommodates, or adjusts, the eye for near or remote vision.

Acetabulum (Lat. _acetabulum_, a small vinegar-cup). The cup-shaped cavity of the innominate bone for receiving the head of the femur.

Acid (Lat. _acidus_, from _acere_, to be sour). A substance usually sour, sharp, or biting to the taste.

Acromion (Gr. ????? the tip, and ???, the shoulder). The part of the scapula forming the tip of the shoulder.

Adam's Apple. An angular projection of cartilage in the front of the neck. It may be particularly prominent in men.

Adductor (Lat. _adduco_, to draw to). A muscle which draws towards the middle line of the body, or of the hand or foot.

Adenoid (Gr. ?d??, a gland). Tissue resembling gland tissue.

Afferent (Lat. _ad_, to, and _fero_, to convey). Vessels or nerves carrying the contents or impulses from the periphery to the center.

Alb.u.men, or Alb.u.min (Lat. _albus_, white). An animal substance resembling the white of an egg.

Alb.u.minuria. A combination of the words "alb.u.min" and "urine."

Presence of _alb.u.men_ in the _urine_.

Aliment (Lat. _alo_, to nourish). That which affords nourishment; food.

Alimentary (Lat. _alimentum_, food). Pertaining to _aliment_, or food.

Alimentary Ca.n.a.l (Lat. _alimentum_). The tube in which the food is digested or prepared for reception into the blood.

Alkali (Arabic _al kali_, the soda plant). A name given to certain substances, such as soda, potash, and the like, which have the power of combining with acids.

Alveolar (Lat. _alveolus_, a little hollow). Pertaining to the alveoli, the _cavities_ for the reception of the teeth.

Amba (Gr. ?e??, to change). A single-celled, protoplasmic organism, which is constantly changing its form by protrusions and withdrawals of its substance.

Amboid. Like an _amba_.

Ampulla (Lat. _ampulla_, a wine-flask). The dilated part of the semicircular ca.n.a.ls of the internal ear.

Anabolism (Gr. ??a???? to throw or build up). The process by means of which simpler elements are _built up_ into more complex.

Anaesthetics (Gr. ??, without, and a?s??s?a, feeling). Those medicinal agents which prevent the feeling of pain, such as chloroform, ether, laughing-gas, etc.

Anastomosis (Gr. ???, by, and st?a, a mouth). The intercommunication of vessels.

Anatomy (Gr. ??at???, to cut up). The science which describes the structure of living things. The word literally means dissection.

Antiseptic (Lat. _anti_, against, and _sepsis_, poison). Opposing or counter-acting putrefaction.

Antrum (Lat. _antrum_, a cave). The cavity in the upper jaw.

Aorta (Gr. ???t?, from ?e???, to raise up). The great artery that _rises up_ from the left ventricle of the heart.

Aponeurosis (Gr. ?p?, from, and ?e????, a nerve). A fibrous membranous expansion of a tendon; the nerves and tendons were formerly thought to be identical structures, both appearing as white cords.

Apoplexy (Gr. ?p?p????a, a sudden stroke). The escape of blood from a ruptured blood-vessel into the substance of the brain.

Apparatus. A number of organs of various sizes and structures working together for some special object.

Appendages (Lat. _ad_ and _pendeo_, to hang from). Something connected with a part.

Aqueous Humor (Lat. _aqua_, water). The watery fluid occupying the s.p.a.ce between the cornea and crystalline lens of the eye.

Arachnoid Membrane (Gr. ??????, a spider, and e?d??, like). The thin covering of the brain and spinal cord, between the dura mater and the pia mater.

Arbor Vitae. Literally, "the tree of life"; a name given to the peculiar appearance presented by a section of the cerebellum.

Areolar (Lat. _areola_, a small s.p.a.ce, dim. of _area_). A term applied to a connective tissue containing _small s.p.a.ces_.

Artery (Gr. ???, air, and te???, to contain). A vessel by which blood is carried away from the heart. It was supposed by the ancients to contain only air, hence the name.

Articulation (Lat. _articulo_, to form a joint). The more or less movable union of bones, etc.; a joint.

Arytenoid Cartilages (Gr. ???ta??a, a ladle). Two small cartilages of the larynx, resembling the mouth of a pitcher.

Asphyxia (Gr. ?, without, and sf????, the pulse). Literally, "without pulse." Condition caused by non-oxygenation of the blood.

a.s.similation (Lat. _ad_, to, and _similis_, like). The conversion of food into living tissue.

Asthma (Gr. ?s?a, a gasping). Spasmodic affection of the bronchial tubes in which free respiration is interfered with, owing to their diminished caliber.

Astigmatism (Gr. ?, without, and st??a, a point). Irregular refraction of the eye, producing a blurred image.

Atrophy (Gr. ?, without, and t??f?, nourishment). Wasting of a part from lack of nutrition.

Auditory Nerve (Lat. _audio_, to hear). The special nerve of hearing.

Auricle (Lat. _auricula_, a little ear). A cavity of the heart.

Azygos (Gr. ?, without, and ?????, a yoke). Without fellow; not paired.

Bacteria (a?t?????, a staff). A microscopic, vegetable organism; certain species are active agents in fermentation, while others appear to be the cause of infectious diseases.

Bactericide (_Bacterium_ and Lat. _caedere_, to kill). Same as _germicide_.

Bile. The gall, or peculiar secretion of the liver; a viscid, yellowish fluid, and very bitter to the taste.

Biology (Gr. ???, life, and ?????, discourse). The science which treats of living bodies.

Bladder (Saxon _bleddra_, a bladder, a goblet). A bag, or sac, serving as a receptacle of some secreted fluid, as the _gall bladder_, etc. The receptacle of the urine in man and other animals.