Mu'cous mem'brane. The lining membrane, or tissue, of the entire alimentary ca.n.a.l. It is very complex in structure, has different characteristics in different areas, and contains nerves, blood vessels, lymphatics, and in various parts special structures such as glands. It secretes mucous. It is continuous with the outside skin of the body, as may be seen at the lips.

Pan'cre as. The gland that secretes the pancreatic juice; located in the abdominal cavity near the stomach.

Pan cre at'ic juice. An alkaline digestive juice poured by the pancreas into the small intestine; especially valuable in the digestion of starches, fats, and proteins.

Per i to ne'um. The membrane lining the abdominal cavity and enfolding its organs.

Phar'ynx. The pa.s.sage between the nasal pa.s.sages and the esophagus: the throat.

Py lor'us. (1) The opening from the stomach into the small intestine.

(2) The fold of mucous membrane, containing muscle fibres, that helps to regulate the pa.s.sage of food through the pyloric opening.

Sa li'va. The digestive secretion in the mouth, consisting of the secretion of the salivary glands and the secretion of the mucous membrane of the mouth.

Stom'ach. The pouch-like enlargement of the alimentary ca.n.a.l, lying in the upper part of the abdominal cavity, and slightly to the left, between the esophagus and the small intestine.

III. RELATING TO FOOD AND DRINK

Ac'id ([)a]s'[)i]d). A substance (usually sour tasting) that has, among other properties, the power of combining with an alkali in such a way that both substances lose their peculiar characteristics and form a salt.

Al'co hol. A colorless liquid formed by the fermentation of starch-sugars or certain other substances, which is highly inflammable and burns without smoke or waste; it is a stimulant and an antiseptic.

Al'ka li. A substance that has, among other properties, the power of neutralizing acids and forming salts with them. (See Acid.)

Car'bo hy'drates. Plant or animal substances composed of carbon, hydrogen, and oxygen. (Called also starch-sugars.)

Chlo'ro phyll. The green coloring matter of plants, formed by the action of sunlight on the plant cells. It is a necessary part of the plant's digestive system, since without it the plant could not break up the carbon dioxid of the air into the carbon which it uses in preparing its starch food, and the oxygen which it gives off as waste.

Fer men ta'tion. A chemical change in plant or animal substance, produced usually by the action of bacteria, in the process of which the substance is broken up (decomposed), and new substances are formed.

Nar cot'ic. Any substance that blunts the senses, or the body's sensibility to pain or discomfort.

Ni'tro gen. A tasteless, odorless, colorless gas, forming nearly four-fifths of the earth's atmosphere; and const.i.tuting a necessary part of every plant and animal tissue.

Pro'te ins. Foods containing a large amount of nitrogen; such as meat, fish, milk, egg, peas, beans.

IV. RELATING TO THE BLOOD AND THE CIRCULATORY SYSTEM

A or'ta. The main artery of the body; it leads out from the left ventricle of the heart, carrying arterialized blood (blood that has been acted upon by oxygen) to all parts of the body except the lungs.

Ar'te ries. The blood vessels and their branches that carry blood from the heart to all parts of the body. The pul'mon a ry artery carries impure (ve'nous) blood to the lungs.

Au'ri cles (o'r[)i] klz). The two chambers of the heart that receive blood from the veins.

Cap'il la ries. The minute blood vessels which form a network between the ends of the arteries and the beginnings of the veins.

Cir cu la'tion. The pa.s.sage of the blood from the heart into the arteries, and from them through the capillaries into the veins, and through the veins back into the heart.

Cor'pus cles (cor'p[)u]s'lz). Minute jelly-like disks or cells. These are of two kinds, red and white, the red (the oxygen carriers) being about 350 times as many as the white, and giving the blood its color.

Heart. A muscle-sac located in the thorax between the lungs, its lower point, or a'pex, being tilted somewhat to the left; the centre and force-pump of the circulatory system.

Ox i da'tion. Combining with oxygen.

Ox'y gen. A colorless, odorless, tasteless gas, which forms about one-fifth of the earth's atmosphere. It is found in all animal and vegetable tissues. When it combines with other substances, a certain amount of heat is produced; and if the process is sufficiently rapid, a flame is seen.

Pulse. The regularly recurring enlargement of an artery, caused by the increased blood flow following each contraction of the ventricle of the heart.

Veins. The blood vessels and their branches through which blood flows from all parts of the body back to the heart. All the veins except the pulmonary veins carry impure (venous) blood; the pulmonary veins carry arterialized (oxidated) blood from the lungs. Ve'na ca'va. Either of the two large veins discharging into the right auricle of the heart.

Por'tal vein. The large, short vein that drains the liver and adjacent parts.

Ven'tri cles. The two chambers of the heart that receive blood from the auricles and force it into the arteries.

V. RELATING TO THE RESPIRATORY SYSTEM AND ORGANS OF EXCRETION

Al ve'o li ([)a]l v[=e]'o l[=i]). (Plural of _alveolus_). Air cells.

The cells, or cavities, that line the air pa.s.sages and air sacs at the ends of the bronchial tubes.

Breath. Air taken in or sent out in respiration; that breathed out containing carbon dioxid, watery vapor, and various impurities.

Bron'chi (br[)o]n'k[=i]). (Plural of _bronchus_). The two main branches of the trachea. These branch into numerous smaller branches, called the bron'chi al tubes.

Car'bon di ox'id. A gas formed of carbon and oxygen; colorless and odorless; has a somewhat acid taste, and is used for aerating soda water and other beverages; is present naturally in mineral and spring waters.

It is present largely in the fissures of the earth and makes the choke-damp of mines. Called also car bon'ic acid.

Ep i glot'tis. The valve-like cover that prevents food and drink from entering the larynx.

Ex cre'tion. A waste substance thrown out, or rejected, from the system; for example, carbon dioxid, sweat, ur'ine, the fe'ces.

Lar'ynx. The enlargement of the windpipe, near its upper end, across which are stretched the vocal cords.

Lungs. Two spongy organs in the thorax, entered by the bronchi with their bronchial tubes; they contain in the walls of their air cells the capillaries through which the blood pa.s.ses from the branches of the pulmonary artery to the branches of the pulmonary veins.

Rec'tum. The lowest and last section of the alimentary ca.n.a.l, being the discharge pipe of the large intestine, and excreting the solid wastes in the form of the feces.

Res pi ra'tion. Breathing; the action of the body by which carbon dioxid is given off from the blood and a corresponding amount of oxygen is absorbed into the blood.

Skin. The continuous outer covering of the body, in the deeper layer (der'ma) of which are located the sweat glands, which secrete sweat (a watery, oily substance containing impurities from the blood) and excrete it through the sweat ducts and their openings (pores) in the surface of the skin.

Tra'che a (or tr[=a] ch[=e]' [.a]). The windpipe between the larynx and the bronchi.

U'ri na ry system. The organs concerned in the secretion and discharge of urine: the kid'neys (two glands in the abdominal cavity, back of the peritoneum, which receive wastes from the blood, and excrete them as urine), the u re'ters (ducts through which the urine flows from the kidneys to the bladder), the blad'der (an elastic muscle-sac in which the urine is retained until discharged from the body).

VI. RELATING TO THE NERVOUS AND MOTOR SYSTEMS