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 space between the cornea and crystalline lens of the eye. Arachnoid Membrane (Gr. ἀράχνη, a spider, and εἰδώς, like). The thin covering of the brain and spinal cord, between the dura mater and the pia mater. Arbor Vitæ. Literally, “the tree of life”; a name given to the peculiar appearance presented by a section of the cerebellum. Areolar (Lat. _areola_, a small space, dim. of _area_). A term applied to a connective tissue containing _small spaces_. Artery (Gr. ἀήρ, air, and τερέω, 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. ἀρύταινα, a ladle). Two small cartilages of the larynx, resembling the mouth of a pitcher. Asphyxia (Gr. ἀ, without, and σφίξις, the pulse). Literally, “without pulse.” Condition caused by non-oxygenation of the blood. Assimilation (Lat. _ad_, to, and _similis_, like). The conversion of food into living tissue. Asthma (Gr. ἆσθμα, a gasping). Spasmodic affection of the bronchial tubes in which free respiration is interfered with, owing to their diminished caliber. Astigmatism (Gr. ἀ, without, and στίγμα, a point). Irregular refraction of the eye, producing a blurred image. Atrophy (Gr. ἀ, without, and τροφή, 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. ἀ, without, and ζυγός, a yoke). Without fellow; not paired. Bacteria (βακτήριον, 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. βίος, life, and λόγος, 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. Bright’s Disease. A group of diseases of the kidney, first described by Dr. Bright, an English physician. Bronchi (Gr. βρόγχος, windpipe). The first two divisions, or branches, of the trachea; one enters each lung. Bronchial Tubes. The smaller branches of the trachea within the substance of the lungs terminating in the air cells. Bronchitis. Inflammation of the larger bronchial tubes; a “cold” affecting the air passages.