1. Dys-æsthesia. Defective perception; a morbid state of the corporeal senses generally.

2. An-aesthesia. Absence of the sense of touch. The former term is extended to all the senses; the present is limited to a single

sense.

3. Estheterium. The seat of the senses, or the sensorium. The term has been applied to an organ of sense, and to the perceptive faculty.

4. Esthesiometer (uiтpov, a measure). An instrument for measuring the tactile sensibility of the surface of the human body, in health and disease, by finding the shortest distance by which two points can be separated when brought into contact with the body, and yet both be distinctly perceived and felt.-Webster.

ESTHETICA (αἰσθητικός, belonging to αἴσθησις or sensation). Agents affecting sensation, and employed either to increase or to diminish sensibility; in the former case they may be termed hyperesthetica, in the latter hypæsthetica. See Anaesthetica.

ÆSTIVATION (@stivus, belonging to summer).

Præfloration.

A term used in botany, to express the manner in which the parts of a flower are arranged in the flower-bud, with respect to one another, before their expansion. Compare Vernation.

E'STUS VOLA'TICUS. Literally, flying heat; a synonym of Wild-fire rash. See Strophulus.

ETAS. Age; a term including the several states of life, as infancy, youth, and old age. Etas firmata is the prime or full strength of age, the age of thirty. Etas constans is the steady age, the age of forty. Etas matura is the age of maturity or prudence, the age of fifty.

To these may be added the following terms :-Etas affecta, a state of total decay in the human frame; Etas ingravescens, a burdensome age, the weight of years; Etas exacta vel præcipitata, the decline of age or end of life; Etas decrepita, decrepit age, as relates to the countenance and state of old age; and Etas extrema, relating to the approaching end of life. See Ages of Life.

AETHEO'GAMOUS PLANTS (anons, unusual, yáuos, marriage). Semivascular plants; a class of flowerless plants furnished with stomates and vascular tissue. The term has reference to the unusual method of their reproduction. See Amphigamous.

ETHER (alone, ether, the sky, the pure region of air above our atmosphere). A term applied to a highly volatile and inflammable liquid produced by the action of an acid on alcohol or on rectified spirit. The ether of the Br. Ph. is "a volatile liquid prepared from alcohol, and containing not less than 92 per cent. by volume of pure ether." Pure ether is "ether free from alcohol and water."

ETHE'REA. Spirituosa. A class of stimulants, including ardent spirits, wine, beer, and the ethers. See Methystica.

ÆTHEREO-ÓLEO'SA. A class of vegetable stimulants which owe their medicinal powers wholly or chiefly to volatile oil.

ETHIOPS (Aldío, an Ethiop). An Ethiop; and, hence, a medicine as black as an Ethiop. Hence the terms mineral aethiops, or black sulphuret of mercury; aethiops per se, or grey oxide of mercury; martial aethiops, or deutoxide of iron; &c.

ETHOGEN (aï0wv, brilliant, yɛivouaι, to become). A compound

of boron and nitrogen, discovered by Mr. Balmain. It gives a brilliant phosphorescent light, when heated before the blowpipe.

ETIOLOGY (airioλoyía, a giving of a cause; from airía, a cause, Móyos, an account). The doctrine of the causes or reasons of phenomena; hence, the doctrine of the causes of disease, the proximate or occult, and the remote or evident causes.

AFFECTIO, AFFECTUS (afficere, to do something to). The former term denotes the affecting of the mind or body; the latter denotes the effect thus produced. See Preface, par. 3.

A'FFERENT (afferre, to convey to). Bearing or conducting; a term applied to the lymphatic vessels which convey fluids into the glands, as distinguished from the efferent vessels, which convey the fluids from the glands towards the thoracic duct. The term afferent has also been applied to those nerves which convey impressions to the central axis, and which Hartley called sensory nerves, in contradistinction to the efferent or motor nerves. See Efferent.

AFFINITY, CHEMICAL (affinitas, relationship). That kind of attraction by which different classes of bodies combine, at insensible distances, to form compounds, or new bodies, as in the case of an acid with an alkali, forming a salt. The term was introduced from the idea that chemical attraction takes place between those substances only which resemble each other. The metaphor significs, however, not a resemblance, but a disposition to unite.

1. Single affinity is the power by which two elementary bodies combine, as hydrogen and chlorine.

2. Elective affinity denotes the preference which one body manifests in combining with another, rather than with a third, a fourth, &c.

3. Double elective affinity occurs when two compounds decompose each other, and two new compounds are formed, by an exchange of elements. This is also called double decomposition, or complex affinity. 4. Quiescent affinity is that which tends to maintain the elements of a compound in their present state, preventing decomposition.

5. Divellent affinity is that which tends to arrange the particles of a compound in a new form, producing decomposition. In mixing dif ferent compounds, if the sum total of the divellent be more powerful than that of the quiescent affinities, decomposition takes place.

6. Disposing affinity is that which promotes the tendency of bodies to combine in a particular way, by presenting to them a third substance which exerts a strong attraction to the compound they form; when the combination has been effected, the third substance may be withdrawn. Some writers call this tendency to unite the affinity of intermedium. Berthollet styles it reciprocal affinity.

7. Berthollet distinguishes affinity into elementary, when it takes place between the elementary parts of bodies; and resulting, when it takes place with a compound only, and would not take place with the elements of that compound.

AFFINITY, BA'SYLOUS, HALO'GENOUS. Terms employed in the investigation of chemical polarity, and denoting two attractive powers of opposite natures; thus, in a binary compound, as chloride of potassium, there is the basylous affinity of the metal potassium, and the halogenous affinity of the salt-radical chlorine. The former corresponds with vitreous, the latter with resinous electricity.

AFFLA'TUS (afflare, to blow or breathe on). A blast, vapour,

or blight. The term is applied to a current or blast of air which strikes the body and produces disease.

AFFUSION (affundere, to pour to). The pouring of water upon the whole or a part of the body, as a remedy in disease.

AFTER-BIRTH. A term applied to the placenta and membranes of the ovum, which are expelled after the delivery of the fœtus. AFTER-DAMP. The carbonic acid which results from the explosion of marsh-gas, or light carburetted hydrogen.

A'FTER-PAINS. A term applied to the contractions of the uterus which are continued for a certain length of time after delivery.

AGALA CTIA (άyaλakтía, from a, priv., and yála, milk). Defectus lactis; oligogalactia. A diminution or complete absence of milk in nursing women. See Galactorrhea.

A'GAME (ayauos, from a, priv., yάuos, marriage). Agamous or sexless; a term applied to cryptogamous plants, from the notion that they possess no sexual organs.

AGA'RICUS. Agaric; the generic name for all the species of mushrooms, properly so called. The term must not be confounded with Amadou. See Boletus Igniarius.

AGENNE'SIS ( a. priv., yévvnois, a producing). Male sterility; inability to beget offspring. As applied to the brain, it denotes imperfect development and atrophy of that organ.

AGES OF LIFE. The periods of human life, characterized by the most remarkable processes of development, or by their completion, are, according to Müller, the following:-

1. The period of embryonic life. During this period the processes of formation and growth are in their greatest activity. The organs which are forming present none of their functional phenomena, or only a gradual commencement of them.

2. The period of immaturity. This period extends from birth to puberty. It is marked by growth, by the development of the forms of the different parts of the body, and by the gradual perception and analysis, by the mind, of the different phenomena of the senses. The period of childhood comprises the first six years; that of boyhood extends to the fifteenth year.

3. The period of maturity. This period begins at puberty and ends at the period when the generative power is lost, which in woman occurs from about the forty-fifth to the fiftieth year. This period is distinguished into the ages of youth and manhood, or womanhood.

4. The period of sterility. This period extends from the cessation of the fruitful exercise of the generative function to extreme old age.

AGEU'STIA (dysvoría, from a, priv., and yɛúouaι, to taste). This term properly denotes fusting, but is used to imply defect or loss of taste, one of the dysæsthesia of Cullen.

AGGLUTINATİON (agglutinare, to glue or cement to). Adhesive union; the adhesion of parts by means of coagulating substance. See Adhesion.

A'GGREGATE (aggregatus, herded together). 1. Formed into clusters, as aggregate glands. 2. Composed of florets united within a common receptacle, as in composita; or of carpels crowded together, as in ranunculus.

AGMINATE GLANDS (agmen, agminis, a heap). Another name for the aggregate or clustered glands of Peyer, situated in the small intestines. Agminal is the classical term.

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A'GNAIL (ang-nægle, A.S. from ange, uneasy). An old English term for a small flaw of the skin, near the finger-nail, occasioning sometimes a whitlow. It is now applied to the little ragged band of cuticle which curves back and projects at the root of the nail. If the etymology given above is correct, the vulgarity of the term hangnail is solely owing to the undue use of the unfortunate letter h.

AGNI'NA MEMBRANA (agninus, from agnus, a lamb, membrana, a membrane). The name given by Aotius to one of the membranes of the fœtus, from its tenderness.

-AGO'GA, -AGOGUES (dywyós, one who leads, from ayw, to lead or drive). Á termination of words denoting substances which capel others, as in copr-agogues, expellers of fæces; lith-agogues, expellers of calculus, &c.

AGO'MPHIOS (ȧyóupios, from a, priv., and youpios, a grindertooth). Without grinders. The terms agomphiasis and agomphosis are not classical; but gomphiasis and gomphosis are found, the former denoting tooth-ache, the latter a form of articulation.

-AGRA (aypa, seizure). A termination of words denoting a seizure, or pain, generally as applied to gout, as in cleis-agra, gout of the clavicle; pod-agra, gout of the foot, &c.

AGRAPHIA (a, priv., ypaw, to write). Loss of the cerebral faculty of expressing ideas by writing. See Aphasia.

A'GRIOS (aypios, wild, fierce). Agrius. This term denotes living in the fields, and, hence, living wild. In a medical sense, it means malignant, cancerous, &c., with reference to the violence of certain diseases, as in lichen agrius.

AGRY'PNIA (άypuπvía). Sleeplessness; waking; watching. Hence the terms agrypnocóma (@ua, drowsiness), a lethargic state without actual sleep; and agrypnótica, agents which cause wakefulness. The latter have been termed anthypnotica.

A'GUE (Fr. aigu, from Lat. acutus, acute). Intermittent fever. An intermittent fever, attended by alternate cold and hot fits. The interval of the paroxysms has given rise to the following varieties of ague: an interval of 24 hours constitutes a quotidian ague; of 48 hours, a tertian; of 72 hours, a quartan; of 96 hours, a quintan.

The following terms are also in use:-1. The double quotidian, having two paroxysms every day. 2. The double tertian, having a paroxysm every day, those of the alternate days being of equal duration and intensity. 3. The triple tertian, in which two paroxysms occur on one day, and one on the other. 4. The duplicated tertian, which recurs twice on each alternate day. 5. The double quartan, in which a paroxysm occurs on the day succeeding that of the regular quartan, so that there is a perfect intermission only on the third day. 6. The duplicated quartan, in which two paroxysms occur on the day of attack, with two days of intermission. 7. The triple quartan, in which a slight paroxysm occurs on each of the usual days of intermission. 8. Those forms of ague which have longer intervals, as five, six, seven, eight, nine, or ten days, a month, or a year, are termed erratic. See Brassfounders' Ague.

AGUE-CAKE. Enlargement of the spleen, induced by ague, and presenting the appearance of a solid mass or cake.

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AGUE-DROP. A solution of the arsenite of potassa; empirical remedy for which the liquor arsenicalis, or Fowler's solution, is now substituted.

AIR (anp, aër). This term denotes popularly the atmosphere. In chemical language it is frequently applied to a gas, or a permanently elastic or aëriform fluid. Thus, oxygen gas was called vital air; hydrogen gas, inflammable air; carbonic acid, fixed air; ammonia, alkaline air, &c.

AIR-BED. A mattress made of vulcanized india-rubber, divided into separate compartments, each of which is provided with an air-valve. Air-cushions are similarly prepared.

AIR-CELLS IN PLANTS. Air-cavities. Circumscribed spaces surrounded by cells, or lacunæ formed by obliteration of the septa between a number of contiguous cells, as in hemlock and the pith of walnut. They are large in aquatic plants, and enable them to float.

AIR-GAS. The principle of this and similar inventions is that of passing atmospheric air through light hydrocarbons, the latter furnishing the illuminating power.

AKY'ANOBLEPSIA (a, priv., kúavos, blue, Bλéπw, to see). A want of power to distinguish the shades of the blue colour.

AL. 1. The Arabic article signifying the, prefixed to many terms formerly in use, as al-chemy, al-kahest, al-cohol, &c. 2. The terminal particle-al is frequently employed in chemical nomenclature, to express the names of bodies which are either homologous with aldehyd, or are derived from it, as butyr-al, valer-al, chlor-al, brom-al, &c.

A'LA. A wing; and, by metonymy, the arm-pit. Also, in botany, the designation of each lateral petal of a papilionaceous corolla. The following are its anatomical uses :

1. Ala, or pavilion. The upper and cartilaginous part of the ear. 2. Ala majores. Literally, larger wings; another term for the labia externa of the pudenda.

3. Ala minores. Literally, lesser wings; a name applied to the two small folds formed by the nymphæ.

4. Ale nasi. The lateral or movable cartilaginous parts of the

nose.

5. Ala vespertilionum. Literally, bats' wings; the broad ligaments situated between the uterus and the Fallopian tubes.

6. Ale vomeris. Two lamina constituting the sphenoïdal edge of the vomer.

ALA'LIA (a, priv., and Aaλéw, to speak). An old name revived to designate the loss of the cerebral faculty of speech. See Aphasia. ALA'RIS (ala, a wing). Pterygoïd or wing-like; as applied to each of the pterygoid processes of the sphenoïd bone, &c.

ALBINO (albus, white). A person in whom the skin, hair, and iris are light, and the pigmentum of the eye is wanting. The term Albino is derived from the Portuguese, by whom it was applied to individuals found on the coast of Africa, who resembled the negroes in every respect except in their colour, and who were consequently called Leuk-Ethiopes, white negroes. The ferret is supposed to be an albino polecat. See Alphosis.

ALBUGINEA (albus, white). Whitish. The word tunica being understood, we have the following terms:

1. Albuginea oculi. The tunica sclerotica, or fibrous membrane situated immediately under the conjunctiva, formed by the expansion of the tendons of the four recti muscles. From the brilliancy of its whiteness, it has given rise to the popular expression white of the eye.