VIL´LI (L. _vil´lus_, the nap of cloth). Minute thread-like projections found upon the internal surface of the small intestine, giving it a velvety appearance. VIT´RE-OUS (L. _vi´trum_, glass). Having the appearance of glass; applied to the humor occupying the largest part of the cavity of the eyeball. VIV-I-SEC´TION (L. _vi´vus_, alive, and _se´co_, to cut). The practice of operating upon living animals, for the purpose of studying some physiological process. VOCAL CORDS. Two elastic bands or ridges situated in the larynx; they are the essential parts of the organs of the voice. * * * * * {265} INDEX. ------o------ A. PAGE Absorbent vessels, 97 Absorption, 96 by blood-vessels, 96 by the lacteals, 96 of the food, 96 Accommodation, function of, 213 Achilles, tendon of, 27 Adam's apple, 229 Air, atmospheric, 131 Changes in, in respiration, 132 Carbonic acid in, 138 Composition of, 131 Dust in the, 137 Effects of impure, 139 Impurities in, 136 Matters in the expired, 132 Provision for purifying, 141 Renovation by ventilation, 142 Air-cells of the lungs, 125 Air-passages, 125 Albinos, 44 Albumen, 58 of the blood, 102 Albuminoid substance, 57 Varieties of, 57 Properties of, 57-58 Albuminose, 94 Alcoholic liquors, 77 Physiological action of, 78 Alimentary canal, 81 Animal functions, 143 Animal heat, 143 how produced, 143 regulated by perspiration, 145 Animals, relative strength of, 28 Apoplexy, 171 Aqueous humor, 210 Arachnoid membrane, 152 Arbor vitæ, 154 Arterial blood, 107-135 differs from venous, 135 Arteries, 114 Arrangement of, 115 Carotid, 116 Distribution of, 115 Pulsation of, 115 Radial, 116 Temporal, 116 Arytenoid cartilage, 229 Asphyxia, 250 Assimilation, 80, 121 Audition, 215