My o' pi a (_muo_, I contract; _ops_, the eye). Nar cot' ic. A drug producing sleep. Na' sal (na'-zal). From _nasus_, the nose. Nerve (neuron, a cord). Ni' tro gen Gas is the passive element of the air. Ni trog' e nous. Containing nitrogen. Nu tri' tion. The process by which the body is nourished. Œ soph' agus (e-sof'-a-gus). The gullet; literally, a "food-carrier." Ol fac' to ry. Pertaining to the smell. Or' gan. An organ is a portion of the body designed for a particular use, which is called its _function_; thus the heart circulates the blood. Os' se ous. Bone-like. Os' si fy (_ossa_, bones; _facio_, I make). Ox i da' tion. The process of combining with oxygen. Ox' y gen. The active element of the air. Pal' ate (_palatum_, the palate). Roof of the mouth. Pan' cre as (_pas_, all; _kreas_, flesh). An organ of digestion. Pa pil' la, plu. papillæ. Tiny cone-like projections. Pa ral' y sis. A disease in which one loses sensation, or the power of motion, or both. Pa rot' id (_para_, near; _ous_, _otos_, ear). One of the salivary glands. Pa tel' la (a little dish). The kneepan. Pec' to ral. Pertaining to the chest. Pep' sin (_pepto_, I digest). The chief constituent of the gastric juice. Per' i car' di um (_peri_, around; _kardia_, the heart). The membrane wrapping the heart. Per' i os' te um (_peri_, around; _osteon_, bone). The membrane around the bone. Per' i stal' tic (_peri_, round; _stallein_, to arrange). Applied to the worm-like movement of the alimentary canal. Phar' ynx (far'-inx). From _pharugx_, the throat. Pi' a Ma' ter (tender mother). See Brain. Pig' ment. A paint. Plas' ma (plaz'-ma). The nutritious fluid of the blood. Pleu' ra (plu'-ra). From _pleuar_, a rib. The membrane that lines the chest and wraps the lungs. Pres by o' pi a (_presbus_, old; _ops_, the eye). A defect in the eye common to old age. Proc' ess. A projection. Sometimes it retains its ordinary meaning of "operation." Py lo' rus (a gate). The doorway through which the food passes from the stomach. Pul' mo na ry (_pulmo_, the lungs). Pertaining to the lungs. Ra' di us. A Latin word meaning the spoke of a wheel, a ray, etc. Ram' i fy. To spread like the branches of a tree. Res' pi ra´ tion (_re_, again; _spiro_, I breathe). Act of breathing. Ret' i na (_rete_, a net). The expansion of the optic nerve in the eye. Sa' crum (sacred). So named, it is said, because this bone of the pelvis was anciently offered in sacrifice. Sa li' va. A Latin word meaning spittle; the fluid secreted by the salivary glands. Scap' u la. The shoulder blade. Scav' en ger. A street sweeper. Sele rot' ic (skie-rot'-ic). The outer coat of the eye. Se cre' tion (_secretum_, to separate). Sed' en ta ry persons are those who sit much. Sen' so ry Nerves. The nerves of feeling. Se' rous Membrane. A thin tissue, or skin, covering the cavities of the body that are not open to the external air. Se' rum. The thin part of the blood.